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TABLE OF CONTENTS

I. CLINKER fORMATION AND CLINKER GRANULOMETRY ..,..,.., , ,..,., , 1

II. IMPORTANCI'; OF COOLER EFFICIENCY FOR HEAT CONSUMPTION 3

m. COOLER TYP-ES " , , .4

A, P!l\!1t;!~ry Cooler. '" , , ,.4B. RP!'!Q' Cooler. , " , , , 9C. First Generation Grate Cooler 10D. S.~<e9!19 Generation Grate Cooler , , 11

1, Pundamcntal Design Features of Second Generation (Air-Beam)Orate Coolers " , 12

([I) Bridging (Dead) Grates and EvolvedGrate-Line Configurations . 13

(b) Alternative Grate-Line Suspensions , , 14(c) External Spillage Conveyosr & Valves ..,,, 16(0 Reduced F[l1I Through Grates 17(e) Hydraulic; Drives .. . 18(jj Clinker Crushers , 19(g) Three-Component Control System 20(h) Air Beam Technology , 22(i) Elevated Resistance Grate Plates .., 230) Stationary Inlet Section.... . 27

2, Process Considerations ".', , 283, Efficiency, Recuperation and Cooler Heat Loss , 304, Impact of Second Generation Grate Coolers

(Air-Beam & Elevated Resistance Grate Plate Designs) .355, Second Generation Grate Cooler Summary and

Commentary '.'.•.... ,.. ,., ,.39

E. Third Q~!1eration Grate Coolers. , .., .41

I. fundamental Design features of Third Generation GrateCoolers "'.""""" .42(a) Modular Design. , . 42(b) Fixed Grate-Line For Air Distribution ..43(c) Separate Clinker Conveying System .. 44(d) Air Distribution Plates With Mechanical

Flow Regulators, ,.... . .452, Further Improvements/Developments of Third Generation Grate Coolers .483, Third Generation Grate Cooler Performance 51

IV, COMPARlSON OF FIRST, SECOND and THIRD GENERATION COOLER PERFORMANCE 52

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I. CLINKER FORMATION AND CLINKER GRANULOMETRY

It is a well-known fact that the granularity of clinker products can vary considerably from

one cement plant to another. Even kilns within the same plant are often found to produce

quite different clinker, although fed with the same raw mix.

FIGURE 1 shows some sieve test results obtained from a wide range of clinker samples. It

appears that the dust content, for example grains finer than half a 111m, can vary between I

and 70%. Also the presence of even a small proportion of oversize clinker, say bigger than

40mm (1-1/2"), contributes very much to the overall appearance of a clinker product.

Furthermore, clinker made up of compactly fused and well shaped nodules appears to be

completely different from clinker with a similar sieve curve, but consisting of cokelike and

sharp edged agglomerations of dust particles.

Such observations have naturally led to investigations of the factors affecting clinker

formation.

In preheater kilns, the formation of nodule shaped clinker must take place in or just above

the burning zone, since the raw mix somewhere further up in the kiln is in the form ofmeal.

In a wet-process kiln strong nodules often come out from the chains as determined during the

drying of slurry. The extent to which these nodules affect the final clinker granulometry, if

at all, is unknown. However, wet kilns tend to produce a coarser clinker size distribution

than do precalciner kilns.

Clinker formation is related to raw mix composition and operating conditions. The clinker

formation may start already in the calcining zone, where a certain agglomeration of the fine,

solid particles may take place aided perhaps by the presence of low melting alkali salts.

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However, the final result depends on what happens in the burning zone. Here the formation

of liquid phase begins at a temperature slightly below l300°C, and the quantity of liquid

increases with the temperature up to a certain final value as shown in FIGURE 2.

The amount of liquid does not increase gradually with the temperature, but in steps on

reaching certain temperatures. Only by applying extreme temperatures can this final amount

of liquid be further increased which, however, usually has disastrous effects on coating and

lining.

The quantity of liquid phase at normal burning temperature amounts to 20-25% of the

clinker, depending on the content of alumina, iron, magnesia, and alkalies. If the quantity of

liquid phase is too small, good clinker formation will not take place. Conditions may then

be improved by changing the raw mix composition, which in practice is usually done by

adding iron ore, thus reducing the silica ratio.

In some cases it will be possible to improve the clinker formation by burning harder, even

harder than required for bringing down free lime. The reason, of course, being an increase in

liquid phase. But it is often seen that if the burning temperature is raised even further, the

result will be dusty clinker, probably due to a too low viscosity of the liquid. At several

plants we have also found a rather sharp limit to the lime saturation factor, if good clinker

grading is to be obtained; if this limit is exceeded the clinker becomes dusty.

The clinker granulometry is important for the satisfactory operation ofany cooler: There

must not be too much dust. Less than J5% minus 0.5 mm (0.02") is good. Too much clinker

plus 25 mm (I") increases the clinker temperature after the cooler because of the slow

cooling of this fraction. Less than I0% plus 25 mm (I") is good.

The clinker dust in the cooler tends to blow back into the kiln, thus establishing a dust

circulation between kiln and cooler. The dust can disturb the radiation from the flame in theAsocemAugust 2006

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kiln, and often it spoils the clinker formation so that the dust circulation tends toaccelerate.

Dust circulation means that the amount ofheat contained in the clinker entering the cooler

increases. This result is always to lower the efficiency ofthe cooler.

II. IMPORTANCE OF THE COOLER EFFICIENCY FOR THE HEAT

CONSUMPTION

A characteristic heat balance for a kiln with a 4-stage preheater and a conventional grate

cooler can look like this: (Ref. Temperature 18°C - MOF)

kcal/kg MBtu/t

Heat in Exit Gas + Dust 177 .637

Surface Loss Kiln 56 .202

Surface Loss Preheater 24 .086

Cooler Loss 142 .511

Heat of Reaction 417 1.50 I

816 2.937

Total Heat Consumption 790 2.843

Ifwe look at the possibilities of bringing down the heat consumption, then about 25 kcal/kg

(0.09 MBTU/ST) can be saved in the exit gas by adding a 5th cyclone stage to the preheater,

but in some plants the full amount ofheat in the exit gas is used for drying the coal and raw

materials, so this heat is not wasted.

The surface loss from the kiln shell can be brought down by using a type of insulating bricks

in part of the kiln, but these bricks have generally a poor lifetime.

A better insulation in the preheater will partly result in a higher exit gas temperature instead

of saved heat input to the system.

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Regarding the cooler, it is so that if we could establish a perfect counterflow in the heat

exchange between clinker and air, then nearly all the heat in the clinker could be transferred

to the combustion air. Therefore, the largest potential for bringing down the heat

consumption rests with the cooler.

III. COOLER TYPES

In the following the four (4) types of coolers, considered by the industry for modern cement

kilns, are discussed. These are: planetary coolers, rotary coolers, grate coolers (both

conventional and air-beam types), and cross-bar coolers.

A. Planetary Coolers

The planetary cooler served the cement industry for many years and was originally

designed for wet process kilns with a high amount of secondary air available for the

cooler.

In modern dry process kilns with a low heat consumption, the amount of secondary

air available for cooling (when this is done with secondary air only) is only about I

kg air per kg clinker (1 lb. air per lb. clinker) or even less. This requires a very

efficient heat transfer between air and clinker obtained by cascading the clinker

through the air flow. It also requires that the internal parts in the hot end can stand

high temperatures, which is obtained with wear resisting ceramic materials.

In a planetary cooler, such as the Unax, the principle of having a number of cooler

tubes rotating with the kiln and connected directly to the kiln is used.

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A breakthrough for the new planetary cooling principles came when a kiln support

below the cooler was introduced. This permitted heavy cooler tubes with the

necessary internal fittings to be supported without excessive stresses in the kiln shel1

and opened the way for designing Unax coolers for kilns with a high capacity. The

one shown in FIGURE 3 is producing 4000 tid clinker (4,400 STPD), and the cooler

consists of 10 tubes, each 2.4 x 29 m (7'IO"x 94'9"). It is only for kilns having

capacity less than 1000 tid (1100 STPD) for which it is economical to leave out the

support below.

Each cooler tube is attached to the kiln with a fixed and a movable support, welded

to heavy kiln sections as shown in FIGURE 4.

The inlet to the cooler has a special design which prevents clinker from fal1ing back

into the kiln when a tube is in top position.

The cooling is based upon cascading the clinker through the air flow. This is not as

simple as it seems, as fine clinker falling down from the lifters through the air is

carried the wrong way by the air, and an excessive number of lifters has proved to

lead to overfilling the coolers, back spilling into the kiln and high exit clinker

temperatures.

The shape and number of the lifters in the various temperature zones have to be

carefully determined by means of a mathematical model, the input being an

anticipated grading of the clinker as shown in FIGURE 5.

At the cooler outlet the fine clinker falls through a grizzly to the clinker transport,

while coarse clinker and lumps are discharged at the side to a hammer mill clinker

crusher as shown in FIGURE 6.

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In principle, coarse clinker requires more cascading and fine clinker less in the hot

end of the cooler in order to avoid excessive circulation between cooler and kiln,

which conveys more heat to the coolers. The inlet part with a special shape is lined

with castables. In recent years special, dense castables have been developed for such

a purpose, fulfilling all requirements regarding abrasion resistance, shock resistance,

chemical resistance against alkali attack etc., and the practical experience with these

modem castables has been very good.

In the cylindrical part ofthe coolers there is first a section ofcorrugated brick lining,

followed by cast heat resistant steel lifters of special design, either lined with steel

plates, as shown, or for the hot part with a ceramic lining, either bricks or castables.

In the cold end of the coolers, mild steel lifters with a high lifting capacity,

increasing towards the outlet, are used, and no lining is used here.

The outlet of the kiln to the coolers was previously made with steel casings, which

caused problems when exposed to high temperatures. The problems have been

solved by using a ceramic outlet made of the high quality, dense castables now

available.

The cooling effect depends, of course, on the size of the cooler. It can be expressed

as the clinker production in relation to surface and volume for the cooler tube by the

following formula:

r =Specific Load =(n P J- [_t_]or[ shT ]* DI 5 * L - m25d m2 5d

,

Illsrna R:»T fHI·

UIN 511'''O'1r lUJ "lrIE

Where:

p

n

L

D

clinker production in t/24 h (shT/24 h)

number of cooler tubes

length of cooler tubes in rn

cooler tube diameter in m

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A normal specific load would be 3.65 tlm25 * d or (0.208 shT/m2 5) . A normal

clinker exit temperature would be 160°C (320°F) above ambient at this loading and

at a specific heat consumption of 780 kcal/kg for the kiln system. For calculating

expected clinker temperatures at other clinker capacities, the following relation may

be used:

Expected Clinker Tempature above ambient = 160"C * (...l)1.6 * 780kcallkg3.6 X

Where X is the specific fuel consumption (kcal/kg) at the new conditions and y is the

cooler loading in tlm2.5 * d at the new conditions.

The air velocity in the cooler tubes should not be too high to avoid excessive dust

circulation. Therefore the expression:

p

* II 0 2n -x4

should not exceed 70 t/m 2 or (77 shT/m2) .

The temperature of the clinker from a Unax cooler ofan economical dry process kiln

will usually average 160°C (320°F) above ambient temperature. It can vary with the

clinker grading, and, ofcourse,it increases by forced output. The temperature can be

reduced, if required, by addition of water to the coolers ncar the outlet. The

equipment required is very simple: Just a gutter around the coolers, from which the

water runs into the individual cooler tubes. The amount ofwater is controlled by the

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clinker temperature, and it has been established that I % water on clinker basis

reduces the clinker temperature by about 15-20°C (68°F), which is close to the

theoretical maximum. The effect on the heat consumption is therefore small, as long

as the amount of water is kept below 3% of the clinker weight.

The heat losses from a planetary cooler consist of: (I) radiation loss and (2) sensible

heat in the clinker leaving the cooler. A normal cooler loss would be: (20°C ref.

temp./68°F).

TYPICAL COOLER LOSS-PLANETARY TYPE

Radiation 90 kcal/kg 0.349 MBTU/shT

Clinker (150°C/300on 25 kcal/kg 0.090 MBTU/shT

SUM 122 kcal/kg 0.439 MBTU/shT

This compares favorably with a conventional grate cooler especially when the

lower power consumption is also taken into consideration.

Depending on the cost relation between fuel and power, I kWh/t will often

correspond to the cost of 7 kcal/kg clinker (0.025 MBTU/shT).

It would, of course, be possible to insulate the cooler much better, but that would

lead to an excessive clinker temperature - a certain amount of heat has to be wasted

through radiation. The length of the different types of lining has to be chosen so that

the cooler shell temperature does not become excessive at any point.

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Another favorable feature is the low power consumption, only about 1.0-1.5 kWhJt

(0.9-1.5 kWhJshT) clinker added to the kiln drive and exhaust fan.

The Planetary cooler is unique in its simplicity, no excess air to handle, no motors or

fans, no instruments. In operation there is nothing to control, it is self-adjusting. One

disadvantage is that the clinker temperature is higher than for grate coolers. The

primary disadvantage is that the planetary cooler does not permit take-out for hot

tertiary air as required for modem calciner kilns. The higher noise level can also be a

problem in some areas.

B. Rotary Cooler

As mentioned above, the main drawback of the planetary cooler is that it was not

suited for modem precalciner kilns with external tertiary duct. This had (prior to the

dominance of grate coolers) given the separate rotary cooler a come-back.

The rotary cooler is also operated without excess air, but it permits take out of

tertiary air for a precalciner through a specially designed "rabbit-ear" kiln hood.

The cooler shown in FIGURE 7 is designed for a 2000 tid (2200 shT/D) kiln with

precalciner and has the dimensions 4.75 x 55 m (15'6" x 180'), which means that it is

bigger than the kiln.

Just as for the planetary cooler, the cooling is based upon cascading the clinker but

with specially designed lifters, which prevent clinker from hammering on the lining

when dropping into the large diameter cooler. The mild steel section is divided into

six compartments so that efficient cascading is permitted.

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The rotary cooler necessitates two efficient seals. The cooler has a 4.5% inclination

and a maximum rotating speed of 4.0 RPM. The power consumption for the cooler

drive is 3.5 kWh/t (3.2 kWh/shT).

Because the specific surface is lower than for a planetary cooler, the surface heat

losses are also lower, and that gives a favorable thermal efficiency, but it also results

in a higher clinker temperature, 200-250°C (390-480°F). Again, however, this can be

reduced somewhat by spraying water into the outlet.

The investments for a rotary cooler are higher than for a planetary cooler, but may in

some cases be lower than for a grate cooler when efficient cleaning of excess air is

required.

C. First Generation Grate Coolers

The grate cooler, however, is overwhelmingly accepted as the preferred method of

clinker cooling for today's modern cement plants.

As shown in FIGURE 8, for the traditional grate cooler, the clinker drops from the

kiln onto reciprocating, air-quenching grates with compartmentized high-pressure

cooling fans.

Below the grates, the cooler is divided into a number of compartments, each

provided with fans having adjustable inlet vanes for automatic air flow control and

minimum power consumption. Clinker spillage through the grates is collected in

hoppers and removed through air-tight flap valves to the clinker conveyor.

FIGURE 9 presents the advantages of the grate cooler over other types of coolers.

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As shown, the reasons for grate cooler's preference are because the grate cooler is

capable of handling large outputs (10,000 MTPD or more) and because it is capable

of cooling clinker to very low temperatures (65°C above ambient or less). The grate

cooler as shown in FIGURE 10 also permits recuperation of hot tertiary air for

today's precalciner kiln systems.

D. Second Generation Grate Coolers

The second generation (air-beam type) grate cooler has a standard cooler heat loss of

90 to 110 kcal/kg, which is a significant improvement over other cooler types such as

the rotary and planetary coolers. This, in itself, is remarkable since these other

cooler types operate without excess air; excess air being far and away the most

significant area of heat loss from the grate cooler.

Nevertheless, 90 to 110 kcal/kg (air-beam grate cooler heat loss) is still a substantial

portion of the overall loss of the kiln system. Therefore, the clinker cooler offers the

largest potential for further decreasing the heat consumption of modern

pyroprocessing systems as shown in FIGURE J]. Undoubtedly, further

developments will be made in the area of clinker cooling. One point is obvious: the

second generation (air-beam type) grate cooler represents a compromise between

reliability and efficiency. For this reason, third generation designs such as

F.L.Smidth's Cross-Bar Cooler or Polysius's Poly-Track Cooler or Claudius Peters

Eta Cooler or KHD's Pyrotloor Cooler have emerged in recent years.

During the period of time since Fuller Company/F.L.Smidth first developed the air­

quenching grate cooler during the late 1930s, the grate cooler emerged as the logical

choice for any new clinker cooler installation. Second generation grate cooler

designs employ a number offundamental design features that evolved over 60 years.

By the early 1990's, all of the major cement equipment suppliers were offering

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cooler designs that incorporated the latest developments in grate plate and air

distribution technologies. These "air-beam" technologies were integrated with the

fundamental design attributes which made the Grate Cooler an industry standard for

many decades.

The following section will highlight the mechanical design features present in all

second generation (air-beam) grate coolers and describe the maintenance and process

benefits of each.

1. Fundamental Design Features of Second Generation (Air-Beam) Grate

Coolers

Over the first 60 years since the introduction ofthe grate cooler, a number of

developments helped to make the grate cooler a reliable and efficient piece of

machinery; namely,

(a) Bridging (Dead) Grates and Evolved Grate-Line Configurations

(b) Grate-Line Suspension Systems (e.g. Internal Wheels)

(c) External Spillage Conveyors & Spillage Valves

(d) Reduced Fall Through Grates

(e) Hydraulic Grate Drives

(f) Clinker Crushers

(g) Three-Component Control System

(h) Air Beam Technology

(i) Elevated Resistance Grate Plates

(j) Stationary Inlet Section

Until the late 1990's the design features listed above had been the universally

accepted staples of the modern grate cooler. Though variations in design

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existed, all major equipment suppliers generally were offering the above

components. Moreover, the variations offered usually had very similar

results in actual practice. A description of maintenance and process benefits

of each component follows.

(a) Bridging (Dead) Grates and Evolved Grate-Line Configurations

. Bridging plates (dead grates) are the conversion of a moving plate to a fixed

plate by bridging from fixed row to fixed row over a moveable row. Fuller

Company/F.L.Smidth first installed bridging plates (dead grates) during the

mid-1960s in order to rectify problems associated with hot fines coming into

contact with side castings. Bridging plates (dead grates) as shown in

FIGURE 12A were installed adjacent to the side castings, then covered with

castable refractory to protect the cooler's structural frame from the hot clinker

fines. Bridging plates (dead grates) were found to improve cooler

performance and increase capacity. Observation showed reduction in cooler

width gave a deeper bed depth and greater uniformity across the width of the

cooler.

With a deeper and more uniform clinker bed, it was found that the material

cooled quicker, the air to the kiln was warmer, and the operation of the kiln­

cooler was more stable. At the time of their development, dead grates

allowed for an increase in the cooler's specific loading from 38 to 42

MTPD/m2. Today dead grates also are used on modem air-beam coolers,

which have a loading of 50 MTPD/m 2 or more. For these coolers, dead

grates and tapered refractory are installed on the static inlet rows as a means

to distribute clinker evenly across the cooler's width.

1) Maintenance Benefit - Bridging plates (dead grates) act as a barrier

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to prevent damage to the structural frame.

2) Process Benefit - The bridging plates allow deep bed operation,

improving cooling efficiency.

Over the years, many different grate line configurations have been employed.

The earliest grate designs were known as inclined coolers and were sloped at

10 degrees using horizontal grate plates. In order to re-gain control over the

clinker transport efficiency, grate lines of 5 degrees, 3 degrees, and

eventually 0 degrees (horizontal) were employed. The reciprocating action•

of the grates takes place on a 10 degree inclination resulting in an overall

horizontal grate line as determined by the height of the grate's pusher face as

shown in FIGURE i2B and FIGURE i2C.

For modern air-beam coolers, the transport capacity of the cooler is generally

increased due to a more complete aeration of the grate line. It is important to

control the clinker transport to avoid the possibility for "running" clinker, but

it is also important to minimize grate speeds so as to minimize wear. For this

purpose, a four (4) degree inclination of the grate line employing a

configuration of "one movable row followed by two stationary rows" has

been found by some suppliers as a proper compromise between grate wear

and transport efficiency.

(b) Alternative Grate-Line Suspension Systems

Since early cooler designs employed external wheels for carrying the

movable frame, a common maintenance problem was found in the area ofthe

sliding seals where wheel shafts penetrated the cooler housing.· Over the

years, it was found that the most simple and elegant solution to this problem

was the use of internal wheels as shown in FIGURE 13A and FiGURE 13B.

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This eliminated potential loss ofcooling air and prevented clinker dust from

escaping through this area. Internal wheel design has developed to a point

where such components are essentially maintenance free. The preferred

design is a wide, flat wheel constructed of cast steel combined with anti­

friction bearings. This design is essentially wear-free and so robust that a

sunken movable frame or a worn underside grate plate is unheard of. Center

guide rollers are used at standard locations along the movable frame to

ensure proper tracking. Finally, an automatic lubrication system, protected

by a large pipe diameter, keeps the bearings purged of contaminants.

I) Maintenance Benefit - Rugged, wide, flat wheels ensure minimal

wear and sturdy support of the movable frame.

2) Process Benefit - This arrangement eliminates the wheel seals as a

potential source of lost cooling air.

An interesting alternative to use of internals wheels to support the moveable

frame was patented by E.N.C.I. during the early 1970s. This concept known

as the "Pendulum Suspension" was subsequently adopted by lKN as shown

in FIGURE 13C and Claudius Peters as shown in FIGURE 13D during the

1990s. The idea was to suspend the moveable frame on long spring steel

straps (or a series of smaller straps) so that they are self-centering. This had

the advantage of being able to eliminate moving parts such as rollers and

bearings. The spring-steel strips were dimensioned so that, in the vertical

direction, the pendulum lift was 0.5 mm. This enabled the moveable gaps to

be set to I mm. The prerequisites are that the spring-steel strips do not

lengthen, the pendulums are correctly aligned, and that no settlement of the

foundation occurs.

1) Maintenance Benefit - Swing-type support systems eliminate rollers,

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bearings, and lubrication points.

2) Process Benefit - Swing-type support systems better retain the widths

of unwantcd moveable gaps.

In general, these types of sophisticated ",[:WP managcment" systems had great

benefit for air-beam coolers in which the cooler's performance is largely

determined by the size of the gaps between stationary and moveable grate

line components. This is because the cooling air will always take the path of

least resistance.

Of course, it is more beneficial to eliminate the gaps altogether by making

the entire grate line stationary. This iii precisely the reason for the

subsequent popularity of third generation coolers introduced during the late

1990' s. Such "cross-bar type" of coolers make sophisticated "gap

management" techniques obsolete. Moreover, the possibility for a

completely stationary grate line makes obsolete the following components:

(a) Dead grates, (b) Gap managemcnt systems, and (c) Spillage conveyors.

This is because clinker fall-through is completely eliminated.

(c) External Spillage Conveyor & Spillage Valves

Early on in the development of first generation grate coolers, it was found

that proper distribution ofcooling air into the respective undergratc chambers

was a predominant factor in determining the thennal efficiency of the cooler.

For this reason, Fuller CompanylF.L.Smidth led the industry in its

recommendations for small, controllable undergrate chambers. However, it

was recognized that proper distribution of this cooling air would still be

ineffective if the air were allowed to escape with the removal of undergrate

clinker spillage. Thus, modern coolers are equipped with an airtight floor and

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pneumatically operated, double tipping valves for removal of spillage

without the loss of cooling air as seen in FIGURE 14. Coolers equipped

with an internal, open drag chain have sleeve seals between compartments,

but it was Fuller's experience that these seals were not effective at the higher

undergrate static pressures demanded by the industry for improved efficiency

and deeper clinker bed depths. For this reason, the use of external spillage

conveyors and double tipping valves became a staple of modem cooler

design.

I) Maintenance Benefit - This method provides low maintenance,

pneumatically operated tipping valves.

2) Process Benefit - High pressure, deep bed operation results from

eliminating the spillage/product conveyor as a potential source oflost

cooling air.

(d) Reduced Fall Through Grates

Reduced fall through grate plates were first employed by Fuller

Company/F.L.Smidth in 1990 as an alternative to the conventional grate plate

with holes. The grates were designed to reduce spillage into the undergrate

area by means oflabyrinth-type slots as seen in FIGURE 15. In this regard,

their design is similar to modem air beam grate plates, which feature

labyrinth-type slots to prevent the possibility of clinker falling into the air

beam. These slots promote the uniform distribution of cooling air into the

clinker bed. In fact, many operators report that higher levels of aeration can

be accommodated without fluidization of the clinker layer as compared with

conventional grate plates with holes. Reduced fall through grates are

designed to be mounted on conventional grate plate supports with open

bottoms. Thus, the air enters RFT-type grate plates conventionally, that is,

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by means of a pressurized undergrate chamber.

I) Maintenance Benefit - Less clinker fall-through minimizes damage to

undergrate components and spillage conveying system.

2) Process Benefit - Less spillage allows more clinker to remain

available for cooling/recuperation.

(e) Hydraulic Grate Drives

Since the mid-1980s, equipment suppliers have provided hydraulic grate

drives for grate coolers. Suppliers such as F.L.Smidth have since installed

them on nearly all new coolers. The development of the hydraulic drive

system advanced over time to offer more flexibility, reliability and greater

ease of maintenance than mechanical types. Force and motion are imparted

to each grate section by hydraulic cylinder(s) attached to the cross-head shaft.

Sized to overcome expected loads at normal - and maximum - system

pressures, the system is designed to provide a full stroke length, regardless of

speed as seen in FIGURE 16.

I) Maintenance Benefit - Require less maintenance than mechanical

types.

2) Process Benefit - Offer greater ease to move cooler out from under a

load condition, thereby offering the potential for increased

availability.

From a technical standpoint, hydraulic drives offer the following advantages

over electromechanical designs:

I) Possible to vary the speed as conditions require.

2) Possible to vary the operating pressure as conditions require.

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3) Hydraulics are much better in jam conditions because they provide

less shock on the mechanical components.

4) Opportunity to run at significantly different speeds and pressures,

because of the flexibility one gets with using hydraulics.

5) It is much less likely to stall or overload the electric motor with

hydraulics, because hydraulics have a relief valve for overload

protection.

(f) Clinker Crushers

Clinker Crushers are employed to reduce clinker lumps to typically less than

25 mm. This is done either by means of a conventional clinker breaker as

seen in FIGURE 17 at the discharge of the cooler or by means of a modern

roll crusher as seen in FIGURE 18 at either a mid-cooler or end-cooler

position.

Though roller breakers are sometimes used to replace conventional clinker

breakers, they were primarily designed to create more uniform size reduction

for better cooling obtained by mounting between the drives of the cooler.

The roll breaker provides distinct advantages over the conventional hammer

mill type: It runs slower, creates less dust, and receives less wear.

I) Maintenance Benefit - Causes less wear than conventional hammer

breaker due to lower speeds.

2) Process Benefit - Improved cooling results from increased surface

area.

The rollers consist of transport and crushing rolls. The number of rolls is

determined by the capacity of the unit. The transport rolls tum at

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approximately 2 rpm; crushing rolls at about 4 rpm. By comparison, the

operating speed of a conventional hammer mill is about 350 rpm. Normally

roll breakers are hydraulically driven and the rolls automatically reverse if

material jams in the rolls. A unique feature of F.L.Smidth's HRB (heavy­

duty roll breaker) is the ability to reposition the first crushing roll to

compensate for wear and thereby maintain clinker product size. This so­

called "exclusive cavity feature" also enables the efficient size reduction of

very large (e.g 1m diameter) clinker balls.

(g) Three-Component Control System

The grate cooler is based on cross-current cooling air. It therefore needs more

air for cooling than can be used in the precalciner kiln, and the excess air

must be removed and dedusted.

The amount of air needed depends very much on the type ofgrate cooler (air­

beam or conventional) but varies also according to the clinker grading and to

the clinker temperature required. It is costly to cool to low temperatures, but

often this is a requirement for cement grinding operations.

Efficient sealing between the compartments permits operation with relative

high and different pressures in the various compartments. With a normal

clinker bed of 750 mm (30") the pressure drop at a constant air flow per m2

of grate area will decrease from about 750 mm WG (30") in the hot end to

about 250 mm WG (10") in the cold end. The fans are sized accordingly, so

that the maximum pressure decreases from 810 to 300 mm WG (32" to 12").

For trouble-free operation it is an advantage to use a larger air flow in the hot

end, up to 150 kg/rnin.zm" (400 SCFM/Ift\ and less in the cold part,

minimum 60 kg/min.zrn" (165 SCFM/ft2) .

AsocemAugust 2006

The width of the grate is typically reduced at thc inlet in order to spread the

clinker more evenly. Having a high air flow and a thick layer of clinker, it is

possible to get an imperfect, but acceptable, uniform clinker bed and a usable

air flow over the width of the grate. This is essential not only to avoid local

overheating of the grate in the fine side of the clinker but also to avoid

"snow-men", as the clinker is kept moving throughout the whole grate until

the surface solidifies.

The speed ofthe grate can normally be varied between 4 and 25 strokes/min.

Normal operation is typically 10-12 strokes/min. Efficient cooler operation

requires automatic control. A simple and reliable system involves three main

functions as described below and depicted on FIGURE 19A, FIGURE 19B

and FIGURE 19C.

I. Constant air flow to each under-grate compartment (using piezometer

or some other air-flow device).

2. Constant under-pressure in kiln hood (using pressure indicators

spaced around the circumference of the kiln).

3. Regulation of grate speed for constant bed thickness (using the

pressure under the first or second under-grate compartment as a

measure ofbed depth). Note: The second and third grate sections are

usually "slaved" in proportion to the first one.

If the clinker happens to become very coarse, the undergrate pressure may

not correspond to the bed depth, and in such cases the pressure control may

be overruled by the power consumption of the grate.

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oNS"'lJ"'O"'lJ"'lUJ"'lJ"'l5

Such a simple system functions without problems, and in automated plants it

can be supplemented with automatic control of the clinker temperature or

constant air flow to the grate for a given capacity.

(h) Air Beam Technology

In a conventional grate cooler, air distribution and, therefore, cooling

efficiency, is largely determined by the mechanical condition ofthe cooler. A

significant improvement in grate cooler efficiency was gained in the late

1980s with IKN's introduction ofair beams at the inlet to the cooler. During

the early 1990's, all major equipment suppliers developed air-beam systems

and such systems largely replaced conventionally aerated grate coolers. In

essence, air beam systems prevented the possibility that cooling air could

bypass the clinker layer. In this way, air beam technology worked by

improving the air distribution below the grate by connecting individual rows

of the cooler directly to the air supply, rather than by blowing air into the

undergrate chamber in the conventional manner as seen in FIGURE 20. In

such systems, the grate plate supports were used to duct the cooling air

directly to the grate plates and into the clinker bed. Depending upon the

equipment supplier, the air beam was further subdivided across the width of

the cooler such that only a few individual grate plates received air from a

separate, controllable source. Preference was given to the extension of air

beams throughout the entire recuperation zone of the cooler. For this reason,

most equipment suppliers developed air beam systems for use on both the

stationary and movable rows of the cooler. However, in many markets,

simplicity (rather than efficiency) was the key and, therefore, Hybrid Designs

(which incorporate air beams only on the stationary rows) were developed as

shown in FIGURE 21.

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ON!S1iU1iU"ll"lE

1) Maintenance Benefit - Air beam technology improves cooling of

grate plates and supports.

2) Process Benefit - This method Improves cooling air distribution

below grate, minimizing the effect of the cooler's mechanical

undergrate condition on thermal efficiency.

Favorable results were demonstrated in a number of coolers that were

converted from conventionally aerated grates to air-beam systems. Results

were shown to be dependent upon how many of the existing rows were

converted to air beam technology as depicted in FIGURE 22 (Table of

Results). Savings in fuel consumption resulted in a reduction of kiln and

preheater exit gas, both in terms of mass flow and temperature'. In most

instances, this reduction was used to increase clinker capacity.

(i) Elevated Resistance Grate Plates

A well known phenomena in the traditional grate cooler is the "red river",

which is a narrow stream of the clinker, which continues far down in the

cooler at a temperature, which far exceeds that of the neighboring clinker. It

is often red hot (hence the name) long after the other clinker has turned dark,

and it has been seen, that such "red rivers" can reach the clinker crusher.

This is due to the difference in resistance to the air flow across a transverse

section of the cooler. The fine clinker offers a much lowerresistance to the

air flow, than does the coarse clinker and the air, of course, takes the easiest

path. The clinker segregates out of the kiln, with the fine clinker on the kiln

load side and the coarse clinker on the other. Furthermore the air is not

confined to the holes in the grate plates, but can also pass between the gaps

between the grate plates. Investigations have shown that as much of60% of

the cooling air may pass in the gaps between grate plates, thus decreasing the

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quality of the air distribution. Since it is easier to blow air through the coarse

clinker layer, an excess ofair must be applied to the component asa whole to

ensure that enough air is applied at the fine side. FIGURE 23A, FIGURE

23B, FIGURE 23C, FIGURE 23D and FIGURE 23E show how this

phenomenon effects the air distribution in traditional coolers and how it can

be avoided in a modern grate cooler.

The distribution of air in the clinker bed is best described by watching the

pressure drop through a cold layer ofclinker. This can be described by Ergun's

equation as follows:

Where:

~P

H

Y

00

Va =

Dpm =

Pressure Drop Through Clinker Bed

Thickness of Clinker Bed

Clinker Bed Void

Air Viscosity

Air Velocity

Average Particle Diameter

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332

In FIGURE 24 the pressure drops of various clinker sizes are shown as a

function of the free air velocity. The dramatic influence of particle size on air

distribution is clearly seen.

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INSTITUTE

Let us look at an example where the "fine" side mainly consists of2 mm clinker

and the "coarse" side of 5 nun clinker. Here the relationship between air

velocities will be 1/5, meaning that only approx. 17% ofthe cooling air is blown

up through the "fine" side and the rest in the "coarse" side. In cases where the

kiln is producing very dusty clinker, red river will usually be an almost

inevitable consequence.

Air beam systems ensured that virtually all of the cooling air was directed

into all areas of the clinker bed (where some air may have otherwise

bypassed the clinker layer altogether). However, the air distribution above

the grate line was largely influenced by differences in granulometry within

the clinker layer, itself. To ensure a more uniform air distribution above the

grate line, suppliers developed increased flow resistance grate plates for use

with their air beam systems. These grate plates must have anti-sifting

features so that clinker dust cannot fall through the plates and into the air

beams (even if the air supply is interrupted). The increased flow resistance

gives high-pressure losses shown in FIGURE 25.

The higher-pressure losses "normalize" the effects of unequal airflow

velocities through the clinker caused by different regions of resistance within

the clinker bed. This results in an even-velocity profile in all areas of the

clinker bed and a low-mean velocity value. This lower-mean velocity

through the clinker layer tends to reduce the quantity of dust recirculation

between the kiln and cooler, thereby improving the cooler's recuperation

efficiency as depicted in comparative Figure 23A, Figure 23B, Figure 23C,

Figure 23D and Figure 23E.

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334

m aIDl 'IJ' IKJ

Over the years many different systems were developed, but common for all the

systems and the "secret" behind any type any of the second generation grate

coolers was the "built in" resistance in the grate plate which is approximately 25

mbar at an air quantity of approximately 110 kg air/mvrnin, By having this

initial resistance, the air supply will "even out" to the individual plates within

an aeration field.

I) Maintenance Benefit - Lower thermal loading of grate plates is

possible.

2) Process Benefit - Improved cooling air distribution above the grate

minimizes the effect of clinker granulometry on thermal efficiency.

Each of the second generation equipment suppliers had proprietary grate

plate designs. Typically, second generation grate plates had narrow air

stream apertures designed to create flat air jets and high-pressure losses as

shown in FIGURE 26. However, the physical differences between these

grate plates was less important than the fact that it was the grate's air-flow

resistance that gave the desired heat exchange. As long as flow was uniform

over the entire grate surface, then the distribution of cooling air through the

clinker layer was also uniform, provided the bed is not too deep.

A satisfactory level of grate resistance is on the same order of magnitude as

the bed resistance and a satisfactory air distribution is one that allows high

aeration rates without fluidization of the clinker bed.

The basic philosophy behind all of the second generation grate systems was

to provide a more uniform distribution ofair through the clinker bed in a way

such that the heat transfer was maximized. It is a scientific fact that the

cooling air always seeks the path oflcast resistance. With this in mind, all of

AsocemAugust 2006

Ii!SmlDTHoINS TOTUTE

the major equipment suppliers devised schemes to gain more control over the

air distribution. While Air Beam Technology works by improving the cooling

air distribution below the grate line, Elevated Resistance Grate piates work

by improving the air distribution above the grate.

OJ Stationary Inlet Section

By the end of the 1990's, stationary inlet sections had become a universal

feature of all new grate coolers. Fixed inlet designs deliver a higher degree

of utilization and minimize overall maintenance costs. For this reason,

second generation cooler designs (and also third generation designs) employ

some type of stationary inlet section offering a rigid support against the

impact of chunks. This largely eliminates wear due to the absence of any

movable parts.

Equipment suppliers have all adopted the use of a stationary inlet, sloped

section of 3 to 8 rows of air beams inclined at about 15 degrees as shown in

FIGURE 27. Individual designs vary from one supplier to another, but these

design features are less important than the reasons for the derived benefits:

(I) maintenance savings result from the absence ofany moving parts and (2)

fuel savings result from the use of air beam technology.

1) Maintenance Benefit - Having no moving parts ensures extended

grate plate life for many years; rugged stationary designs protect

grate plates from falling clinker/coating.

2) Process Benefit - May provide lower efficiency than alternating

movable and stationary air beams for operational reasons; however,

little is gained in relation to maintenance savings gained through the

absence of any moving parts.

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DNSTDTlUJTE

Preferred Inlet Systems allowed the operator to control the amount of air to

each side of the cooler and to each row of the static section. Preference was

given for a 5 to 9 row stationary inlet module. In the subsequent stationary

and movable grate section, a grate slope of 2-4 degrees was preferred to

minimize grate speed and grate wear. Again, preference was given to the

extension of air beams throughout the entire recuperation zone of the cooler.

2. Process Considerations

The above section has identified the mechanical design features present in

first and second generation grate coolers and has described the maintenance

and process benefits of each. In the sections that follow, the impact of these

mechanical components on process design will be considered.

Handling and dedusting of the excess air is the main disadvantage of the

grate cooler and is also decisive for a comparison between the investment

costs of different cooler types.

The excess air varies with regard to quantity, temperature and dust content,

and the system for its handling, of course, has to be designed for the worst

condition. F.L.Smidth typically uses design figures corresponding to 2.8 kg

. excess air/kg clinker (2.8 Ib/lb clinker) and 400°C (700°F) for conventional

coolers and about 1.9 kg/kg clinker for air-beam grate coolers.

The preferred method of handling the excess air is by means of an air-to-air

heat exchanger and bagfilter. Air cleaning with multi-cyclones is not

acceptable in a modern plant.

AsocemAugust 2006

Another option is to use electrostatic precipitators for excess air. They have

proven reliable and efficient with low operating costs. To reduce the size of

the precipitator, a small quantity of atomized water can be injected through

nozzles in the cooler ceiling/exhaust gas duct during upset conditions.

However, a study of investment costs between precipitators and bag filters

demonstrates the cost effectiveness of bag filters over precipitators for

emission requirements of less than 50 mg/Nrrr' (dry basis). This is because

the size of the precipitator increases exponentially with decreasing emissions

levels whereas the size of the fabric filter remains constant. For this reason,

bag filters combined with air-to-air heat exchangers are preferred in many

parts of the world, where demands for very low emission rates are required.

The decisive factors for the choice between these solutions are operating

costs and reliability, especially the ability to cope with upset conditions.

The advantage ofthe grate cooler is that it is independent of the kiln and very

flexible with regard to production. Also a low clinker temperature can be

obtained, 65°C (150°F).

An important consideration is the high power consumption of the grate

cooler, for conventional type cooler 5-7 kWhit (4.5-6.3 kWhlshT), exclusive

of power for dedusting. Depending on the cost relation between fuel and

power, I kWh/t will often correspond to the cost of? kcal/kg clinker (0.025

MBTU/shT).

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oNSTUTlUJ'ii"l5

3. Efficiency, Recuperation and Cooler Heat Losses

When you wish to specify a new cooler or evaluate how well your existing

cooler is performing with respect to heat recuperation and cooling of the

clinker, it is convenient to be able to do that by means ofsome characteristic

key figures. Often, terms like cooler efficiency, heat recuperation or cooler

loss are used.

It is necessary to define exactly what we understand by those terms and how

we calculate them.

The grate cooler heat losses consist of(1) radiation loss, (2) heat contained in

the hot excess air and (3) sensible heat in the clinker leaving the cooler as

shown in FIGURE 28.

A typical heat loss for a conventional grate cooler would be:

TYPICAL COOLER LOSS-CONVENTIONAL GRATE COOLER

20°C ref. temp. (68°F) KcaI/kg MBtu/shTRadiation 5 0.018Excess Air, 2 kg/kg cl. @ 246°C (475°F) 119 0.428

Clinker 85°C (185°Fl 12 0043

Sum 136 KCALlKG 0.489 MBtu/shT

In cases where low-temperature heat can be utilized for drying of raw

materials or coal, up to 50 kcal/kg clinker (0.180 MBTU/shT) of the waste

heat can be recuperated and then, of course, the thermal efficiency becomes

very favorable.

AsocemAugust 2006

Ii!smIDTH·

UNS"lJ"'O"lJ"'lUl"lJ"'lE

The heat recuperation is also at times called cooler efficiency. It is necessary

to know the temperature of the clinker coming from the kiln to calculate the

% heat recuperation; this temperature is nearly impossible to measure.

Arayo-tube gives incorrect values, because the clinker at the kiln outlet is

often covered with a layer of dust coming from the cooler, and also the

temperature at the surface can be different from that in the center of the

clinker particles. It is also difficult to take out a representative sample of

clinker into a bucket and to measure the temperature outside the kiln.

What is important for the heat consumption 111 the kiln is the heat

recuperation from the moment the clinker leaves the burning zone. The

burning zone temperature is also difficult to measure, but often I450°C is

taken as a standard value.

For the same cooler working with the same type of clinker, the heat

recuperation will depend on the amount of combustion air that goes from the

cooler to the kiln. This amount again depends on the heat consumption,

excess air for the combustion, the amount of primary air and the amount of

false air through the kiln seals.

FIGURE 29 shows the cooler loss and heat recuperation in relation to the

amount of combustion air. The different lines represent coolers with

different recuperation abilities. As the grate cooler is not a cooler with a

perfect counter-flow, there is an absolute maximum for the heat recuperation

ability. The lines K = 1.00 represent such an ideal cooler with maximum

recuperation ability.

The curve K = 0.23 corresponds to a traditional cooler working well.

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IiJsmlDTHDNSTBi1"U.i1"lE

The following comments can be made on the amount of combustion air:

A dry process kiln using 750 kcal/kg clinker will only need half as much

combustion air as a wet process kiln using J500 kcal/kg clinker. It is

therefore obvious that the cooler loss will be much less for the wet process

kiln than for the dry process kiln, even when the amount and temperature of

the clinker from the kiln, and of the cooling air blown into the cooler, is

exactly the same in both cases.

The only difference is: (1) the amount and, (2) temperature of the excess air

will be very much different; clinker temperature and surface loss of the

cooler will be the same in the two cases.

Figures for cooler losses are therefore without meaning if the amount of

combustion air from the cooler to the kiln system is not known. The same, of

course, applies to cooler efficiency or recuperation percent which is basically

100 minus the cooler loss expressed as percent of the heat in the clinker

leaving the kiln.

Although it is possible to measure the amount of tertiary air on precalciner

kilns by a Pitot tube or similar, there is no way to measure the amount of

secondary air from cooler to kiln tube. It is therefore better to determine the

amount of recuperated air by calculation, Lambda = 1.00.

Usually the figure works out at about 1.41 - 1.42 kg air per 1000 kcal lower

(net) heat value fired when the fuel is bituminous coal or fuel oil; for fuels

with a high content of water the figure will typically be higher.

AsocemAugust 2006

Ei!s.m'I.DTHUII\!! S"1r011"U "1rIe

The combustion air actually used will (in addition to the stoichiometric air)

also include the air excess, which can be calculated from the 02 - and CO2­

content in the gas after the combustion process, .The formula is:

Lambda = ----------1_79.I

X02

20,9 100-C0 2 -0 2

Lambda = 1.20 for instance means that there was 20% air excess where the

gas analysis was made.

From the total combustion air Lcom = Lambda x Lmin it is necessary to

subtract the various sources of false air, including primary air, which do not

come from the clinker cooler.

The most complicated case is when there arc two combustion processes in

series, such as ILC precalciner kilns.

Estimation of the secondary air requires a measurement ofthe 02 - and CO2­

percent in the kiln tube exit. From this the lambda value can be calculated

and hence Lcom.

Not all of this air has come from the cooler. The primary air, including

transport air for coal meal (if any), must be measured and subtracted.

Further, false air entering at the kiln outlet seal between kiln tube and kiln

hood and through gaps in the kiln hood, must be subtracted.

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Iij!os:nlID.THDN.STDTUTE

If the probe sampling the gas after the kiln tube is not located inside the kiln

tube, but rather in the riser duct, false air entering through the kiln back end

seal must also be subtracted.

The tertiary air can be determined in a similar way. Lmin for the total

amount offuel burned in kiln and calciner is calculated. O2 and CO2 after the

calciner are measured, and the lambda is calculated. The total amount of

combustion air is calculated.

From this must now be subtracted secondary air from cooler to kiln, primary

air to kiln burner, false air at kiln hood/outlet seal, false air through back end

seal, primary air/transport air calciner, false air in calciner and false air in

tertiary air dust trap. IfO2 and CO2 analysis are not made immediately after

the calciner but after the top cyclone, false air in the cyclone preheater

including air from pneumatic kiln feed transport (if any) must also be

deducted.

Cooler losses are usually measured and calculated according to rules laid

down by the German Cement Makers Association VDZ, which use ambient

temperature as the reference. When calculating the recuperation efficiency,

VDZ assumes a clinker temperature of 1450 °C and nil dust circulation

between kiln and cooler. The latter can have a huge influence on the actual

cooler loss. VDZ further does not take into consideration that practically all

mechanical energy put into the cooling fans has been converted into heat

when the air leaves the surface of the clinker bed with zero pressure and

velocity. The latter can be eliminated if the temperature of the cooling air is

measured on the pressure side of the fans.

AsocemAugust 2006

mlDTHnfI\!l S TOTlUlT15

FIGURE 30A and FIGURE 30B give the definitions for Cooler Loss

including Total Cooler Loss (reference temperature DoC), VDZ Cooler Loss

(reference temperature = cooling air temperature), and Standard Cooler Loss

(normalized combustion air requirement). F.L.Smidth has introduced the

concept standard cooler loss, which means the VDZ cooler loss at a

total recuperated amount of cooling air of 1.155 kg/kg clinker. Similarly, the

standard efficiency must refer also to 1.155 kg/kg clinker ofrecuperated air.

FIGURE 31 shows how the cooler loss and process heat recuperation vary as

a function of the amount of recuperated air; The more recuperated air, the

lower the cooler loss and the higher the recuperation efficiency.

4. Impact of Second Generation Grate Coolers (Air-Beam &

Elevated Resistance Grate Plate Designs)

A significant development in the efficiency of grate coolers was made in the

early 1990's with the introduction of (I) Air-Beam technology and (2)

Elevated Resistance Grate Plates.

The amount ofair for air-beam coolers generally lies between 2.3 and 2.6 kg

air/kg clinker (2.3-2.6 lb air/lb) but in order to cope with forced conditions

and fluctuations, we normally install a fan capacity corresponding to approx.

2.8 kg air/kg clinker (2.8 Ib air/lb). In comparison, the conventional type

grate coolers were designed for 3.5 to 3.8 kg air/kg clinker (3.5 to 3.8 Ib

air/lb).

343

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DmlDTHlONSTOTUTI5

The specific load of new type grate coolers expressed in tid per m2 is

normally 45-50 MTPD/m2 compared to 38-42 MTPD/m2 for conventional

grate coolers. This higher grate load is mainly possibly due to a much better

heat recuperation in the air-beam type grate coolers which allow for a lower

retention time and partly the result of the tendency to work with a thicker

clinker bed.

Air-beam coolers and modem grate plate designs were developed in response

to traditional deficiencies of the conventional grate cooler (such as the air

taking the path of least resistance) whose correction would contribute to.better grate lifetime and better heat recuperation.

It is clear that the area on which attention should be focused is in the first

section of the cooler (heat recuperation zone). Ifmore heat can be recovered

from the clinker and utilized in the process, we can save energy and obtain a

more stable kiln and cooler operation.

Many different second generation grate systems were developed, but

common among all was a "built-in" resistance across the grate plate which is

approximately 250 mmWG (lOinWG) at an air quantity of approximately

110 kg air/m2/min (300 SCFM/ft\

To have full control over the flow/speed of the clinker layer, to avoid "red

rivers" as shown in FIGURE 32A, and to guard against "snowmen"

formations as depicted in FIGURE 32B, a preferred grate arrangement uses a

horizontal grate layout and a moveable first row. However due to

maintenance reasons and the general lifetime of the impact zone, the use of

five to eight stationary rows at a slope of approximately 15°became widely

accepted. For this reason, most equipment suppliers such as F.L.Smidth

AsocemAugust 2006

today use an inclined impact section. To avoid material build up and

"snowman" formation it is necessary to install air blasters for the stationary

inlet section, depending on the clinker materials tendency to form

"snowmen" and the cooler size as shown in FIGURE 32C.

After the Stationary Inlet Section, second generation cooler designs typically

employed a series of air-beam grates that covered the rest of the recuperation

zone as shown in FIGURE 33. As shown, preference was often given to the

use of grate sections inclined at 2° - 4° where every second and third grate

row was stationary. Operational complexity is clearly minimized by

maximizing the number of stationary rows compared to moveable rows.

After the air-beam section, Reduced Fall Through grates typically covered

the rest of the drive sections as shown in FIGURE 34.

If required, the air beam system can cover the entire cooler grate area, but

due to increased operational complexity and cost, such an arrangement is

uncommon. When air-beams are extended throughout the recuperation zone,

the result is a more efficient grate cooler where the heat recuperation is

greatly improved compared to coolers of conventional design.

The overall result of an air-beam cooler compared to a conventional cooler

IS:

30 - 40 kcal/kg clinker reduction in standard cooler loss.

Reduced size of Cooler, approx. 30%

30 - 40% reduction in size of Cooler ventilation system.

Improved Kiln and Cooler operation.

Possibly lower maintenance cost.

Reduced tendency to "red river" formation.

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DNSTITUTE

Not only new coolers can be supplied with the air-beam systems. An

existing, conventionally aerated grate cooler can be modified to include air­

beam features. With the air-beam systems, the grate load may be increased

(and together with an improved heat recuperation) the clinker production can

be increased.

For a retrofit, normally only the first cooler grate is modified. The remainder

of the grate(s) and cooling systems are left untouched. By retrofitting the

complete first grate, maximum benefits will be delivered since this grate (in

most cases) will cover the complete heat recuperation zone. However, the

system can also be offered for less than the complete first grate, i.e. installing

a static inlet section only.

In addition to the operating advantages, there are compelling economic

considerations like heat savings of 30-85 kcallkg clinker, a yearly capacity

increase typically in the neighborhood of5% and a payback time ofless than

1 year.

Conversion of an existing cooler to a modem air-beam type offers some

evident operational benefits, including:

heat savings of 30 - 85 kcallkg clinker

reduced dust circulation

reduced air consumption

During the Work Session on Clinker Coolers, you will have the opportunity

to make an estimate of the heat savings resulting from a retrofit to the

cooler's first grate. You will find that the savings is proportional to the

AsocernAugust 2006

amount of "air-beam" air. In other words, the savings is proportional to the

number of installed air-beam grates rows, but also to the mechanical

condition of the cooler. As will be shown, when carrying out a retrofit, it is

preferable to change the complete recuperation zone. With careful planning

retrofits can be undertaken very efficiently (typically, the erection can be

done in less than 3 weeks during a planned kiln stop).

5. Second Generation Grate Cooler Summary & Commentary

From the late 1980's until the late 1990's, the cement industry's cooler

market had been dominated by air-beam technology and resistance grate

plates. All major equipment suppliers offered some type of air-beam

technology and high-pressure resistance grate plate designs. Unquestionably,

these technologies made improvements over the conventional grate cooler, in

particular, improvements were made to the air distribution below the grate,

through the grate, and above the grate. As a result, the heat transfer between

the air and clinker improved and substantial reductions in specific cooling air

requirements were realized.

Taken as a whole, continually improved design features made it possible to

substantially improve the thermal efficiency of the grate cooler from 1990 to

2000. FIGURE 35 and FIGURE 36 present comparative heat balances of

typical grate cooler performance resulting from design improvements during

the 1990's. As shown, it was made possible to reduce the cooler's heat losses

from 160-130 kcal/kg to 125-100 kcal/kg or even less. These heat loss

savings were the result of a reduction in the specific cooling air requirement

from 3.1 kg air/kg clinker to 2.5 kg air/kg clinker during this time. This

reduction in cooling air input resulted in a 'corresponding reduction in the

cooler's excess air requirements from 2.0 kg air/kg clinker to 1.4 kg air/kg

341,

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AsocemAugust 2006

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,-

UNSTUTUTlE

clinker, thereby decreasing the capital costs of cooler vent systems.

However, the grate cooler of the mid 1990's still represented a compromise

between efficiency and reliability. In many respects, potential process

benefits had taken a back seat to maintenance benefits, or more aptly,

availability. This was because mechanical simplicity is favored over process

complexity. That is, despite dramatic improvements, the air-beam grate

coolers of the mid 1990's were still plagued by relatively high maintenance

costs and operational complexities associated with these equipment

innovations. Disadvantages included:

• The valves, pipes, dampers and connectors for the air-beams required

operator adjustment. Furthermore, these components precluded

access to the under-grate chamber.

• Since the cooling and conveying mechanisms were integrated,

air-beam coolers suffered from deteriorating cooling performance as

the grate plates (located in the moving sections) began to wear.

• The requirement to supplement "air-beam" air with "sealing" air (i.e.

air introduced in the conventional manner) was one of the primary

disadvantages of the high-pressure resistance grate plate designs.

• The continued possibility for clinker fall-through with any moveable

grate system and the resultant need for an under-grate spillage

conveying system constituted a further disadvantage.

For these reasons, in 1996, engineers at F.L.Smidth set out to develop a

cooler that was superior to the second generation grate coolers (i.e. the most

efficient of air-beam coolers). The goal was to develop a cooler having

maximum availability by focusing on a design which was simpler to operate

and simpler to maintain than either the conventional grate cooler or the

air-beam technologies. Many ideas were proposed and discussed. The

requirement was to separate the cooling mechanism from the conveying

mechanism so that there would be absolutely no deterioration of cooling

efficiency over time, inefficient sealing air would not be required, clinker

fall-through would be eliminated, and the needfor under-grate sealing and

transport systems could be avoided.

E. Third Generation Coolers

The clinker cooler is a critical component in the cement manufacturing process and

has been an area of great innovation over the years because it represents the greatest

potential for further improving the heat consumption oftoday' s modem kiln systems.

In 1997, arguably the most revolutionary development witnessed by the cement

industry in the last fifteen years took place when the first 3'd generation clinker

coolers were put into operation. These 3rd generation coolers were characterized by

the following innovative features: stationary grate line, separation of the conveying

and cooling mechanisms, modular design, and active airflow control to every grate.

These breakthrough technologies have subsequently led to the current clinker cooler

innovations that are sweeping the industry. The 3'd generation designs provide high

reliability, low maintenance costs, and excellent process efficiency. In some cases,

the 3'd generation technologies have become more affordable because they can be

retrofitted into any cooler, resulting in significantly lower installation costs.

F.L.Smidth was the first supplier to implement a 3'd generation cooler technology (in

1997) which was characterized by the following innovations:

• Stationary Grate Line for the Entire Cooler (FIGURE 37)

• Separation of Conveying and Cooling Functions (FIGURE 38)

• Flow Regulation to Every Grate Plate (FIGURE 39)

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350

BN S T BTUTIE

• Modular Design (FIGURE 40)

The key benefits of these technologies can be summarized as follows:

• Significantly Improved Reliability

• Reduced Maintenance Costs

• Predictable Maintenance

• Commonality of Spare Parts

• High and Constant Thermal Efficiency Over Time

• Quick and Easy Installations

• Workshop Quality

Due to the separation of cooling and conveying functions, the technology became a

win-win solution for both the plant process engineer and maintenance manager.

Modular design reduced installation times and the 'split-drive' configuration (e.g. by

modules or "tracks" or "lanes") enabled both flexible operation and extremely high

availability. With the 3'd generation designs, down-time caused by the clinker cooler

generally became a thing of the past. With F.L.Smidth's successful implementation

of these new technologies, competitors began to develop new designs over recent

years. These new designs largely draw upon the success of the original, innovative

features first developed in 1997, generically known as the "cross-bar cooler"

FIGURE 41 as presented below.

1. Fundamental Design Features of Third Generation Grate Coolers

(a) Modular Design

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I

1 __

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The entire cooler is constructed in modular form. A typical module is four (4)

plates wide and fourteen (14) plates long (1.3 m wide and 4.2 m long) as

depicted in FIGURE 40.

A single module could be a whole cooler or several modules could be

assembled to form a larger cooler. The modules are set side-by-side and end­

to-end.

The modules consist of an under-grate chamber with a grate-line at the top.

The air distribution plates are supported on a stationary tray system. The

grate line is completely stationary so there is no deterioration of cooling

efficiency over time.

The "modular design" is demonstrated in that each module can be pre­

assembled prior to installation, including its refractory. The modules are

simply set side-by-side and end-to-end. As a result, existing grate coolers can

be completely replaced with a new "cross-bar" cooler in as little as 3 to 4

weeks. Also, because all modules are duplicates ofone another, it is possible

to significantly shorten delivery times.

(b) FixedGrate-Linefor Air Distribution

Just as for a conventional grate cooler, the grate-line sits atop a under grate

compartment as shown in FIGURE 42. However, because the sealed grate­

line is completely stationary, the grate plates can be locked together for

maximum process efficiency.

The sealing system of the grate-line is so effective that no devices are

provided for removal of spillage from the under-grate chamber. The bottom

351

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INSTITUTE

of the under-grate chamber has a steel floor without any openings. No

spillage removal valves are provided and no spillage conveyor is installed

under any of the cross-bar coolers. This means less items for maintenance. It

also means lower head room requirements. For new kiln line installations, the

lower head room requirements may yield a savings of 2 - 4 meters in height

for the entire preheater tower and kiln which significantly contributes to

lower civil costs. For existing installations, it enables the cross-bar cooler to

replace existing coolers with low headroom (i.e. coolers with internal drag

conveyors or disc gate spillage removal systems).

Unlike second generation air-beam coolers, no sealing air is required because

both the grate-line and the under-grate chamber are effectively locked. By

eliminating the need for inefficient cooling air and by eliminating the

possibility for under-grate spillage, significant gains in thermal efficiency are

obtained.

(c) Separate Clinker Conveying System

As originally introduced, there were two types of cross bars: stationary and

movable. The stationary and movable cross bars alternated the same as

stationary and movable grate rows alternate in conventional coolers as shown

in FIGURE 43. The movable cross bars are driven by a drive plate. The

drive plate is attached to a movable frame.

AsocemAugust 2006

Unlike the movable frame used in a conventional grate cooler, the frame does

not support any grate plates or their support beams. Quite simply, there are

no movable grate plate supports. As a result, a much more simple design of

movable frame is employed. This allows a simple system oflinear bearings

to be used.

The cross bars are attached to the drive plate by a retainer bracket that

attaches to ears extending from the drive plate. The retainer bracket and cross

bars are locked by wedges driven in by hammer. Replacement of the cross

bar is simply made by knocking the wedges out with a hammer and removing

the retainer bracket.

Spillage is prevented from entering the plenum chamber by a series of

sealing profiles. The sealing profiles combine to form a labyrinth type seal

that prevents undergrate spillage. Since the grate plates do not move, it is

possible to make a very effective seal between the stationary air distribution

system and the moving drive plate. Each module has a hydraulic cylinder

located in the under-grate chamber that imparts a reciprocating motion to the

movable frame that is parallel to the grate-line. When modules are installed

end-to-end, the movable frames ofeach module are connected in such a way

that they move in unison. Modules installed side-by-side do not have their

movable frames connected. In other words, a module positioned alongside of

another module may be stroking rearward while the other module is stroking

forward. In addition, their speeds could be different.

353

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354

DillI OT"oNS"lrD"D"'lUI"'[l"15

(d) Air Distribution Plates with Mechanical Flow Regulators

The heart of the "cross-bar" cooler is its unique and patented air distribution

system. Each air distribution plate consists ofa stainless steel top section that

looks similar to a pocket-style Controlled Flow Grate (CFG) plate.

On the bottom of each individual plate is a rectangular tower containing a

weighted Mechanical Flow Regulator (MFR). Depending upon the pressure

inside the tower, the regulator opens or closes. Because the pressure inside

the tower is an exact measure of the resistance of the material layer above it,

the regulator opens to compensate for an increase III the "measured"

resistance or closes to compensate for a decrease III the "measured"

resistance. The MFR, thus, controls the amount ofcooling air that flows from

the under-grate chamber into each individual air distribution plate as seen in

FIGURE 44A.

The regulators are specially designed to maintain a constant air flow through

the air plate and the clinker layer, irrespective of the clinker bed height,

particle size distribution, temperature, etc. In his way, every air plate in the

cooler is provided with the quantity of cooling air that it needs.

The MFR consists ofa special orifice plate which hangs from the tower. The

hanging plate acts as a variable orifice that moves relative to the difference in

pressure on either side of the plate. The regulator, therefore, only introduces

a pressure drop through it self in the event that the resistance of the clinker

layer is below normal.

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This is in contrast to second generation "air beam" grate plates which

introduce a constant pressure loss for a given air volume. Normally, a

pressure loss of at least 200 mm WG is required to normalize differences in

the clinker layer in order to ensure uniform distribution of cooling air.

With the self regulating mechanical flow device, it is possible to obtain

constant air-flow through the clinker layer without paying for the required

pressure loss of200 mm WG. This, coupled with higher thermal efficiency,

results in a power savings compared to modern air-beam coolers.

Cooling air is supplied to the under-grate chamber of each module by fans

equipped with piezometers. The mechanical flow regulators are so effective

that the required number offans is typically only determined by the number

of modules set end-to-end. That is, modules set side-by-side have their

undergrate chambers joined so that only one fan supplies air to both the right

and left. For example, the a 3x5 "cross-bar" Cooler for 3600 tpd is equipped

with a total of only 6 cooling fans even though it is a triple-wide modular

cooler. It has one fan for the "Controlled Impact Module" plus one fan for

each of the five cross bar modules in length. The regulator used in each grate

plate is designed for a specific air-flow rate as shown in FIGURE 44B. The

regulator design is varied (along the cooler's length) to .compensate for

changes in the resistance of the clinker layer as the clinker temperature

decreases. For example, it is possible to employ a higher specific air-flow to

the air plates at the inlet to the cooler simply by using one regulator design

over another. It is also possible to vary the regulator design across the width

of the cooler. For example, "Zero Flow" regulators may be used along both

sides of the cooler within the "Stationary Impact Module" as a means to

compensate for non-uniform distribution ofclinker across the cooler's width.

355

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Ii!smIDTH.

oNS"'ll'"OTtUJ"'ll'"15

2. Further Improvements/Developments of Third Generation Grate Coolers

Today, the following 3'd Generation Coolers are available:

• "Smidth-Fuller Cross-Bar Cooler" by FLSmidth (FIGURE 45A)

• "Eta Cooler" by Claudius Peters (FIGURE 45B)

• "Polytrack Cooler" by Polysius (FIGURE 45C)

• "Pyro Floor Cooler" by KHD (FIGURE 45D)

In addition, a multi-moveable version of the original "cross-bar" cooler is

now available called the "Multi-Movable" Design which provides all of the

benefits previously afforded by "the cross-bar" cooler in addition to the

following features:

• Increased Transport Efficiency to Allow Horizontal Installation

• Flexibility for Retrofit Situations

• Fewer Wear Parts

• Even Higher Reliability

The increased transport efficiency is accomplished by "removing" the

stationary bars from the original "cross-bar" design and revamping the

moveable bars. The moveable bar transportation mechanism was modified as

follows:

• All drives move in unison in the forward flow direction (FIGURE

46A)

• The "first" drive retracts while the "second" drive acts as a

"stationary" bar (FIGURE 46B)

AsocemAugust 2006

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oIi\!]S'1r0'1rU '1rIE

• The second drive retracts while the first drive acts as a "stationary"

bar (FIGURE 46C)

• The mechanism is repeated (FIGURE 46D)

This subtle change in the drive mechanism has significantly increased the

transport efficiency such that a horizontal grate line is possible for coolers

equipped with the multi-moveable design.

Additionally, the multi-movable technology was specifically designed with

an eye for retrofits. As such, the known dimensions of traditional and air­

beam style coolers have been targeted to design the various cassettes for the

multi-moveable cooler. A multi-moveable cooler cassette is designated with

the width based on grates and supporting beam and the length based on

grates. The cassette configurations cover the following ranges:

• Width: 6, 7, 9 and II Grates

• Length: 12 or 16 Grates

To support partial retrofits of existing coolers, such as the recoup zone, a

special outlet transition has been designed such that the multi-moveable

technology mates to the existing grateline. In this way, the cement producer

can stage the replacement of the entire cooler over a couple of years or they

can simply limit the retrofit to the area that provides "the most bang for the

buck" (i.e. - recoup zone).

With the enormous flexibility in width, length, and transition; a large number

of existing coolers can be retrofitted inside the existing box with the multi­

moveable technology. In addition to retrofitting existing coolers, complete

357

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£i!smIDTHINSTITUTE

new cooler constructions can be installed with the multi-moveable

technology. As with the original "cross-bar" cooler's modular approach, the

cassettes of the multi-moveable can be set side by side and end to end to

make up the entire new or retrofit cooler. Through the utilization of 3D

drawing programs and parametric design, the optimal configuration of

cassettes can be utilized to tailor the multi-moveable cooler to any plant.

It is anticipated the multi-moveable technology will be highly reliable,

maintain a high level of thermal efficiency, and further reduce the

maintenance costs of clinker coolers since the number of wear components

has been reduced. With the increase in transport efficiency and the reduction

of wear parts, it is estimated that the wear components will now last up to

three years before they will require changing. As such, it is estimated that

the average annual parts price for a 10 year period will be further reduced 25

- 50% from the expected figures on the original "cross-bar" cooler.

The increased transport efficiency makes it practical to install the "Multi­

Movable" design horizontally instead of on, for example, a 3 to 5 degree

slope. By means of comparison, FIGURE 47 presents an elevation view for

both an original "cross-bar" cooler and the new multi-movable design.

Importantly, 'bull nose' velocities through the cooler throat are critical to the

success of the cooler operation (e.g. to minimize dust circulation), especially

for this specific retrofit solution presented by FIGURE 47 in which the

existing clinker cooler was of the reverse flow variety (i.e. - it went back

underneath the kiln). As shown in FIGURE 47 A, in the case of a sloped

cooler, the space constraints to maintain proper velocities would have

normally required digging a pit at the cooler discharge area which was not an

attractive option for the cement producer as it would require extra time and a

significant amount of additional money for the modernization. In contrast,

AsocemAugust 2006

the horizontal installation of the new multi-moveable cooler allowed the

proper velocities within the system to be maintained while building the new

cooler on the existing foundation. In this case, it was originally foreseen to

reuse the existing cooler sideframes; however, due to the very poor condition

ofthe sideframes and roof, it was decided to go for a completely new cooler.

The multi-moveable cooler was built in a manufacturing shop, shop tested,

and shipped to site in modular cassette form to maintain the workshop

quality. Arriving early onsite, there was ample opportunity to conduct a

certain level ofpreassembly prior to the major outage. During the outage, the

old cooler was completely removed and the new multi-moveable cooler was

lifted and slid into place on the existing cooler foundation .. The installation

of the cooler was part ofan overall plant wide upgrade. Refer to FIGURE 48

for pictures from the preassembly, installation, and final assembly at the

plant.

3. Third Generation Grate Cooler Performance

Third generation coolers have shown a Standard Cooler Loss corresponding

to 80 to 95 kcal/kg. In comparison, air-beam grate coolers typically have a

Standard Cooler Loss of90 to 120 kcal/kg. This means that the heat recovery

is extremely high for the cross-bar type of clinker cooler.

Improved thermal efficiency of the cross-bar cooler is made possible by the

following design features:

• Inefficient sealing air is not required.

• Clinker fall-through is completely avoided.

359

mlDTH

DNSTDTUT15

• The grate-line is completely stationary, so no gaps exist for possible

short-circuiting of cooling air.

• The clinker conveying system and clinker cooling systems are

completely independent therefore cooling efficiency does not

deteriorate over time.

• The MFR system (a separate air flow regulator for each grate plate) is

used throughout the entire cooler (not just the inlet section and not

just the recuperation zone of the cooler).

• The regulationvalves ensure that each plate in the cooler is provided

with the quantity of cooling air that it needs regardless of process

conditions.

FIGURE 49 presents a typical cooler balance for a cross-bar type cooler. As

shown, significant improvements can be gained compared to "modem" air­

beam coolers.

IV. COMPARISON OF FIRST, SECOND AND THIRD GENERATION

COOLER PERFORMANCE

FIGURE 50 presents comparative process efficiencies for each type of cooler:

• Conventional Grate Cooler (First Generation)

• Hybrid (Air-Beam/Conventional Grate) Cooler

• Air-Beam Cooler (Second Generation).• Modem Grate Cooler (Third Generation)

AsocemAugust 2006

360

99,5

98CIII

-1II(; 95eng' 90CI'l •(I)

co.0. 80fl.;~' 70

60

50

40

. 30

20

1510

" 5

2

10,5

SIZE DISTRIBUTION OF CLINKER

v/. ~~.~-:VJ!/

./~ V) lIllr2'L.: . , ~~~~ LJV I.I P ~v.;y / V

If V ,0;/ Ifl<:,0

;;:?:./ Y.0 / /v / Z 1/~v

~o

',r ,,,~./ j

./ cl/ ~/I

l(AV ~fj.

V ~.»: ,:.. .

./'V·

0,10,09' 0,5 ',0 5 10 50

Screen (mm)

FIGURE 1

361

362

~ ~)

.~

CIltilC'J.r:. .

Q. 20

-::J

::Jtr~

11l

IMPACT OF BURNING CONDITIONS ONCLINKER FORMA TION

i Ca, Si J:( ~r

II

Fe, Mg, AI,. "

I 11--..

I II )K, Na, GI, S <,

I I~

.

Material Temperature ("C)

-~ 35-e-U0:::>tov-r-' 30l':I

llJ(/)

':'J.::::Q. 25-0~

1:7-J

20

'52

FIGURE 2

4

Silica Ralio, Ms

363

364

PLANETARY COOLER WITH 4-STAGE PREHEATER

FIGURE 3

PLANETARY COOLER

TUBE DESIGN

c-: I!!I k/ 'I .... ;":'1 I I·"',':;

'\If "\J f II j hr.=<. ,

~.~

k7V- '-7-

I"""" ,.

cu = - !

c-c

FIGURE 4

365

PLANETARY COOLER

DESIGN OF INTERNALS

Il' ;,. IJOQ ~)O •

c

.-..- ~

I. iI i I I I

_IIttH+Hi I -l-~

~ ,Ill II I . f 1-- r- ' 'Ii._ \ ',///

I ............. tr ...1:11 .... h"'.. rt ~~ I,·~tt -1.!.. ..!. .s, .s, ..!.. ~

AI 1JZlr!;Jly

/~

'L.-

-r~1

~ \ \ ~-~\ :".-::"1

.~ ',r7",Ir'AI'

\~·I.~~

FIGURE 5

366

. ",: v '

UNAX CLINKER COOLER

FIGURE 6

367

E-ED-Dc-c

FIGURE 7

Brick LI nlng

ROTARYKILN

8-B

Max: 6 RPM

A-A

368

First Generation AIR-QUENCHING RECIPROCA TINGGRATE COOLER

FIGURE 8

369

370

•

•

•

•

•

GRATE COOLER

ADVANTAGES

ABILITY TO HANDLE lARGECAPACITIES

CAPABLE OF ACHIEViNG lOW CLINKERTEMPERATURES

FAVORABLE HEAT RECUPERAr~ON

PERMITS TAKE-OUT OF HOT TERTIARYAIR

GREATEST POTENTIAL FORDEVELOPMENT

FIGURE 9

Second Generation GRA TE COOLER

FIGURE 10

371

372

POTENTIAL FOR DECREASING FUEL CONSUMPTION

TYPICAL HEAT LOSSES

(5-STAGE PREHEATER)

lOSS SAVINGSkcallkg cl POTENTIAL

Exit Gases, incl. Dust 165 ModerateRadiation Losses:- Preheater 26 Low- Kiln 35 Low

Cooler losses 130 High

Heat of Reaction 400 None

Water Vaporization 4 None

Free Heat -20 None

NlEllH1eat~ Consumption 740

FIGURE 11

M::Jving Row

BRIDGING PLATES (DEAD GRA TES)

Dead GrateBolt

FIGURE 12A

373

GRATE LINE CONFIGURATION

~oo

Horizontal Cooler

,,,, .>

.--1'100

3 0 Slope Cooler

\

,

374

: -,

Inclined Cooler

FIGURE 12B

COMPARATIVE METHODS FOR GRATE LINE CONFIGURATION

Fuller

DIFFERENT METHODS FOR OBTAINING AN 10° PLATE INCLINATION TO GIVEAN OVERALL HORIZONTAL GRATE LINE

Fa/ax

FIGURE 12C

375

I,

INTERNAL WHEELS WITH GUIDE ROLLERS

FIGURE 13A

376

~~~-----

FLS-STYLE INTERNAL WHEEL DESIGN

C""", pie!.

OustseeI

Grates,

Supporting roller

Cross beam Longitudinalgirder

Guide roller

FIGURE 13B

377

378

Second Generation GRATE COOLERIKN PENDULUM SUSPENSION SYSTEM

PEN'DULuMSU5PEN[)EDFRAME

FIGURE He

~ ~---- --~~-------:---------------...,....-----------------------------:-

Second Generation GRA TE COOLERCLAUDIUS PETERS COMPACT SWING SYSTEM

III .I,,

FIGURE 13D

379

380

EXTERNAL SPILLAGE VALVES

FIGURE 14

REDUCED FALL THROUGH GRATES

FIGURE 15

381

382

Second Generation GRATE COOLERSHYDRAULIC GRATE DRIVE

Fuller Hydraulic Drive

CPAG Hydraulic DriveFIGURE 16

CLINKER BREAKER

FIGURE 17

383

ROLL-TYPE CLINKER BREAKER

FIGURE 18

384

AUTO AIR FLOW CONTROL LOOP

® Pressure Transmitter

@ Pressure Indicating Controller

@ Speed Actuato r

Vari-SpeedDrive

FIGURE 19A

385

KILN HOOD DRAFT CONTROL.

CoolerVent Fan

Vari-SpeedDrive

HeatExchanger

Cooler

KilnHood

~~@<f)~~

Pressure Transmitter

Pressure Indicating Controller

Speed Actuator

FIGURE 19B

386

--------------0----------------;--------------

COOLER GRA TE DRIVE CONTROL LOOP

-. . Z}-----,,.---{

® Hafio Bias Oontroller

® PressureTransmltter

® Pressure Indicating Contr~ller

.@ Speed Actuator

L- -{Fy}--'- ---..;J

FIGURE 19C

387

388

AIR BEAM TECHNOLOGY

FIGURE 20

First/Second Generation HYBRID SYSTEM

INTERNAL VIEW

If

Iloj i

•I

FIGURE 21

389

Second Generation (Air-Beam) COOLER CONVERSTION PERFORMANCE RESULTS

APRIL 1992-AUGUST 1995

PLANT YEAR TPD SIZE GUARANTEE ACTUALPERFO~ANCE

1 1992 2000 9 Row CFG 22 kcal/kg Savings 29 kcal/kg Savings

2 1992 22009 RowCFG

20 kcal/kg Savings . 57 kcal/kg Savings9 Row RFT9 RowCFG

58 kcal/kg Savings3 1992 1900 9 RowRFT 20 kcal/kg Savings

PfH Modif.6.9% Capacity Increase

4 1992 5000 23 Row CFG40 kcal/kg Savings 68 kcal/kg Savings

1.75 kWhiT Reduction 2.2 kWh/T Reduction

5 1992 200018 Row CFG 1500 to 2000 TPD

2200 TPD Actual CapacityPfH Modif. Capacity Increase

6 1993 8509 RowCFG 8.0% Increase of Recuperation

19.4% Increase of Recuperation Eff.8 RowRFT Eff.

7 1993 106017 RowCFG 49 kcal/kg Total Cooler Loss 39 kcallkg Total Cooler Heat Loss19 RowRFT 6.6 kWhiT Total Power 6.5 kWhiT Total Power

8 1993 580036 RowCFG

40 kcal/kg Savings80 kcal/kg Savings

22 RowRFT 9.4% Capacity Increase

9 1994 195018 RowCFG

4.8% Capacity Increase 6.5% Capacity IncreasePfH Modif.

10 1994 4600 32 RowCFG 60 kcal/kg Savings70 kcal/kg Savings

8.1 % Capacity Increase

FIGURE 22

390

KILN - COOLER RELA TIONSHIP

FIGURE 23A

391

392

CONVENTIONAL COOLER AIR DISTRIBUTION

FIGURE 23B

BED DEPTH EFFECT ON COOLING

THIN BEDOPERATION

"'" I KILN.----r-...../ ROTATION

I

I

THICK BEDOPERATION

FIGURE23C

393

COOLING CLINKER WITH ONE COMPARTMENT COOLER

CLINKERBED

COOLINGCURVE

AIRFLOWCURVE

PRESSURECURVE

394

1

FIGURE 23D

COOLING CLINKER WITH FOUR COMPARTMENT COOLER

COOLINGCURVE

CLINKERBED

L--I-_---J. --L- ]_

I~.,---",,-_~Ii

I

I II

I I I

~ I~I.----~

AIRFLOWCURVE

.-{--_----'--_l

PRESSURE·CURVE"

-I3

..--

I I I '4 I1~11 2 ~I-.----_~ ]+-1-------+

FIGURE 23E

395

' ....'(ll

0;..:,x' ....

, Q;'··c...,"C

"al'...:::lrtI

.rtI

2:!C.

RED RIVER

Pre'~~ui-e'dtop ~c r,ossclinker bedbased Ergun's equ .

.

.-

--~ ,

./

/ /'/ I, ,

If I---'"

/ -- ------ ---'

IJ

I //

_.Op': C>.~.l}.2 ~

_Op=a.".()OSCH

_ Dp = o-.Q-1Co 1M

_ op = l).l}1S rM

396

1,00 1,~

Ve 10city [m/s]

FIGURE 24

ELEVATED RESISTANCE GRA TE PLATES

FIGURE 25

397

398

TYPICAL AIR BEAM ASSEMBLY

FIGURE 26

STATIONARY INLET SECTION

FIGURE 27

FlOw

•• ••••••". . . /

399

COOLER LOSS

• HEAT LEAVING THE COOLER ASSENSIBLE HEAT WITH THE CLINKER

• HEAT LEAVING THE COOLER WITH THEEXCESS AIR

• HEAT LEAVING THE COOLER ASRADIATION

FIGURE 28

400

COOLER LOSS AND RECUPERA TION AS A FUNCTION OFCOMBUSTION AIR REQUIREMENT

90

80z0-...<l: 70n::wa..:::JU

·w 60n::I-«w:l: 50~

40

~ ---- ........... ! I Ir-, r-..... ,.....1_-

--~- ~-,

I'-. '" r----...:-.. I" ........... K./1.

"I'--- r-,r-; r---....-.... I l-I--~1'-.' r-, ---... ....... r-Q

~ r-:---r---, r-.. "r-, <,I'-... <,:--... 1""-"<

~'--C'+---I'-- <,r-, :r-~ r----r---

........ r- fo.,.- .... r-......... I . -.I'-... ! r-. I "I r----<,

r-, I'"fL....r--...........

l""'- I .::l-1r--_r-I~~

-I-I ,

,~

1.3

1.3121:11.0

0.9

Q9

0.8

0.8

I -I~~~-I-.,-

~ -.V --l.-'-

V '" ~V .....-

,/ -"~

~--./ .-/ ..-'--V ./V lP ;;.-

-----~.... - --V »:---- ~~........... ......- ..-

/ .//" V

----V (J$ """ !--

/ .,/ - V ----V ~V .-~~--.I ./

",. V V l-VV V V.... V .-V .......-V

V --V .............V

200

180

1GO

140

120

100

80

60

40

20

o100

(f)(f)

o'..J

'0:W....Joou

-..JU

COMBUSTION AIR rROM COOLERKG/KG CLINKER

FIGURE 29

401

COOLER LOSS

• COOLER RADIATION LOSS• HEAT IN CLINKER FROM COOLER• HEAT IN EXCESS AIR FROM COOLER

A. TOTAL COOLER LOSSREFERENCE TEMPERATURE = DOC

CLr=+++

Q IN CLINKER FROM COOLERQ IN EXCESS AIRQINHOT AIRRADIATION

B. VDZ COOLER LOSS (also known as NET Cooler Loss)REFERENCE TEMPERATURE = COOLING AIR TEMPERATURE

CLvDz =+++

Q (CLINKER FROM COOLER) - Q (CLINKER AT COOLING AIR TEMPERATURE)Q (EXCESS AIR) - Q (EXCESS AIR AT COOLING AIR TEMPERATURE)Q (HOT AIR) - Q (HOT AIR AT COOLING AIR TEMPERATURE)RADIATION

C. STANDARD COOLER LOSSCOOLER LOSS INDEPENDENT OF KILN SYSTEM

NORMALIZE:

• COMBUSTION AIR REQUIREMENT = 1.15 kg/kg clinker• COOLING AIR TEMPERATURE = 18°C

FIGURE 30A

402

COOLER EFFICIENCY

A. The cooler efficiency to be defined and calculated as follows:

IJ cooler = 100

Where:

100 x Cooler Loss. %

1450 X SK 1450 + (Mc A X TCA X SA TCA )

Cooler Loss = TKO XSKTKO + MEX XTEX XSATEX+ RA

MCA = kg of cooling air per kg of clinkerMEX = kg of excess air per kg of clinkerTC = temperature ambient (of cooling air)TEX temperature of excess airTKO temperature of clinker leaving the coolerSAT = specific heat of air at temperature T"CSKT = specific heat of clinker at temperature TOCRA = cooler housing radiation in kcal/kg of clinkerReference Temperature = O°C

B. VDZ Cooler EfficiencyReference temperature = cooling air temperature

E =100 _ 100 x (Cooler Loss - Fan Power)voz Maximum Heat Release Clinker

Where:

Maximum Heat Release is defined as the heat content of clinker at the kiln dischargetemperature (arbitrarilydefined at a temperature rangingfrom 1350°C to l450°C)minustheheat content of clinker at the ambient temperature .

C. . Nominal cooler recuperation reference temperature = O°C

R = QSECAIR + Q TERT AIR x100QCLlNKER 1450,C + QCOOLINGAIR

FlGURE30B

403

VDZ COOLER LOSS vs. AIR FROM COOLER TO KILN SYSTEM

........... ; .

1.51.45

1:3 1.41.25 1.35

kg/kg cl.

0.9 1 1.1 f 1.20.85 0.95 1.05 1.15

Secondary & tertiary air

0.7 0.80.75

, .. .

-i~[-:~l~~:t_:li:::·~Fr :t::· .:~:·:.·.t:: .::::....7 ~ ••••••••_

! ! !! ! i I!

·oOJ~

---­COo~

(j)(j)

o'-Q)

ooU

FIGURE 31

404

TYPICAL RED RIVERS

October 1998

May 2000

FIGURE 32A

405

I

406

SNOWMAN FORMATION

FIGURE32B

---------------------

AIR-BEAM STYLE STATIC INLET GRATE

FIGURE32C

407

TYPICAL AIR-BEAM STYLE COOLERWITH STATIC INLET GRATE

FIGURE 33

408

6

12

o

ELEVATION VIEW OF CFGICIS AIR-BEAM 1278 COOLER

CD...

.. ~ ,. '~ '" "' .. '" " ..... ;. fl '. '" ..'J ,'\ ~ _ ,1 <J ill ;. e u "... 1'1 l' "l I'll It " ~ r; r;- ~ 10 .- ,., ,. :~ " ,. " ., "I "1 " " • t! • r- '" - ,., '" ., '1 '"' .. -1 .... l' n ... ,., ,,' "" '" r-: .. .. '. 'J <: 'I

.. -¢ It .. 'l '.' ~ It " ... __' ...~ '" " ~ Jt III fI " II lI. " .. t;, ...0 .1 d " " .:;. ,.; .. " lJ I; ..... ". " ... , ...... OJ_ :i

SSSSSSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMSSMS

cr

FIGURE 34

409

TYPICAL First Generation GRA TE COOLER BALANCE

CONVENTIONAL

Radiation11 kcal/kg

Excess Air2.00 kg/kg

265°C130 kcallkg

aaaa~

aaKiln Exit

1450't383 kcallkg

aa

Tertiary Air0.65 kg/kg <} a a "a

750°C aa

124 kcal/kg aaaaaa..aaaaa

Secondary Air0.45 kg/kg1070 °c

126 kcal/kg

Cooling Air3.10 kg/kg

35°C26 kcal/kg

a

"aaconaccQ

Clinker1.00 kg/kg

100°C19 kcallkg

TOTAL COOLER LOSS: 160 kcallkgSTANDARD COOLER LOSS: 130 kcal/kg

FIGURE 35

410

TYPICAL Second Generation GRATE COOLER BALANCE

AIR BEAM DESIGN

Radiation11 kcal/kg

Excess Air1.45 kg/kg

270°C95 kcal/kg

oo

~oooo$>ooooooooooooo'

Kiln Exit1450 "c

383 kcal/kg

oo

Tertiary Air0.65 kg/kg <l 0000

815°C 0o

135 kcal/kg 0oooooooooo

Secondary Air0.45 kg/kg1220 °c

145 kcal/kg

Cooling Air2.55 kg/kg

35°C21 kcal/kg

ooo

o c a c n e c c

Clinker1.00 kg/kg

100°C19 kcaVkg

TOTAL COOLER LOSS: 125 kcallkgSTANDARD COOLERLOSS : 100 kcal/kg

FIGURE 36

411

412

FIGURE 37

FIGURE 38

413

414

High BedResistance

LowerValve !\P

FIGURE 39

Low BedResistance

FIGURE 40

415

Third Generation (SF CROSS-BAR™)GRATE COOLER

FIGURE 41

417

---------------~-----------~------~------------,---------

Third Generation (SF CROSS-BARTM) GRA TE COOLER

.. ....----- ----"-....

FIGURE 42

419

,

Third Generation (SF CROSS-BAR") GRA TE COOLER

FIXED GRATE LINE

FIGURE 43

421

LOWER

VALVE L1P

Third Generation (SF CROSS-BAR") GRATE COOLER

~WBEDRESISTANCE

HIGHER

VALVE LlP

FIGURE 44A

423

MECHANICAL FLOW REGULATOR CHARACTERISTICS

100

90 J - . - .

80 - . -- - ----. .. - ~ --- - ..- ,- ...-- -

......N 70E - ~ •. - --0,- - _______ - .- -. -_.- -r --]-c:

60E

~ .- --~- ..- IOl 50,:;,c ~-_ ...- -......... ..

S 40 I0.....J ILL 30 - - --__A ---- - .. ~. -- - - I0:: I« 20 ------ ". . . ---_ .. _--- .- . . _. - _.

r10Ia --'

a 50 100 150 200 250 300 350

PRESSURE DROP ACROSS REGULATOR [mmWG](Variation in Clinker Bed Resistance)

FIGURE 448

425

FIGURE 45 A:Fl.Smidth - Cross-Bar Cooler

FIGURE 45 BClaudius Peters - ETA-Cooler

FIGURE 45 D:KflD's - 3rd Generation "Pyro Floor" Cooler

427

FIGURE 46ADrives Move in Unison

FIGURE 46 C:Second Drive Retracts

FIGURE 46 B:First Drive Retracts

FIGURE 46 D:Drives Move in Unison

429

FIGURE47A

FIGURE47B

431

FIGURE 48

433

TYPICAL Third Generation GRA TE COOLER BALANCESF CROSS-BAR'" COOLER

Radiation11 kcal/kg

Excess Air1.05 kg/kg

295 DC75 kcaVkg

Clinker1.00 kg/kg

100 DC19 kcal/kg

~OOOO$>occotroonooooo

Kiln Exit1450

DC

383 kcal/kg

-aOjD:-:O;1r;

oo

Cooling Air2.15 kg/kg

35DC

18 kcal/kg

ll!=:[==~

Tertiary Air0.65 kg/kg <J c c DO

870 DC 0c

145 kcal/kg ocoaoccco

L~: ..;:;- _

Secondary Air0.45 kg/kg1260 DC

150 kcal/kg

TOTAL COOLER LOSS: 105 kcalfkgSTANDARD COOLER LOSS: '85 kcallkg

FIGURE 49

435

OMPARISON OF First. Second. Third Generation GRATE DIFFERENT COOLER TYPES

FIRST FIRST/SECOND SECOND THIRD

PARAMETERSGENERATION GENERATION GENERATION GENERATION

ConventionalHybrid Cooler

Air-Beam Cross-BarCooler Cooler Cooler

Fuel (kcal/kg elk) 745 722 710 692

Stage I Temp. (0C) +20°C +12°C +7"C _oC

Stage I Press. (mrn WG) +8.0% +4.7% +2.7% -Operating Kiln J.D. Fan (kW/mt) 6.03 5.97 5.78 5.49

Air for 80°C + Ambient (kg air/kg elk) 2.90 2.50 2.35 2.10

Standard Cooler Loss (kcal/kg elk) 130 110 100 85

Operating Vent Fan Volume (m3/hr) 245,000 201,000 182,000 151,000

Operating Cooler Vent Temp. 286°C 305°C 298°C 321°C

Operating Cooler Vent Fan Power 1.22 kW/mt 0.97 kW/mt 0.88 kW/rnt 0.72 kW/mt

Clinker Cooling Fans Operating Power 4.80 k w/mt 4.77 kW/mt 4.70 kW/mt 4.28 kW/mt

FIGURE 50

437