Cement Industry Expertise

Ask Dr Clark - Raw materials

Q: What is SO3 in clinker if SO3 in lime stone is 0.35%.

Sulphur in Petcoke is 6-6.5%.Petcoke is firing in kiln with a 40-45% of total

coal consumption per hour.if any direct formula/calculation is there for

getting SO3 in clinker.Please suggest.

A:

The contribution to the clinker SO3 from the limestone will be given by 0.35

x 0.8 x 1.55. The contribution from the fuel will be given by SO3 content of

fuel x kg fuel/kg clinker.

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Q: new cement plant to be built and needs expert advice

do you offer such a service in which you provide expert advice for newly

built cement manufacturers?

A:

Certainly. That is our main line of business.

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Q: High MgO limestone

We are in the process of doing sampling of limestone to check on their

quality before making a proposal to acquire the limestone hill for setting up

an integrated cement plant.We have taken random surface samples covering

about 10% of total hill area and found out that CaO/MgO reading as follows

55.3/0.22,

55.2/0.25,53.3/1.49,51.8/2.79,41.3/11.0,36.4/13.9,54.1/1.32,55.4/0.17,48.6/6.

16,55.5/0.24.We have now used jack hammer so that we can deeper sample

at the high MgO areas again just to retest the quality..Do u expect

difference in MgO level between surface sample and sample at 2 feet depth?

Is the limestone hill usable if we carefully mix it?What is the limit for MgO at

raw mix stage?Can we use the high MgO limestone as additive for cement

grinding? Appreciate your further advice on our next step.

A:

I know no reason to expect a difference in MgO content of the limestone

between surface samples and those at 2 feet depth. Based on the

information provided some of the limestone is high purity and therefore

certainly useable with careful blending. 3% MgO in limestone is the

maximum limit, dependent to some extent on MgO content of secondary

materials and your national standard for cement. The high MgO limestone

can be used as an additive for cement grinding.

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Q: Which slag is suitable for producing Portland slag cement ?

Which slag is suitable for producing portland composite cement? Air cooled

slag or Blast furnace slag? Tahmid

A:

Granulated blastfurnace slag that has been quenched in water when drawn

off the blastfurnace. Air-cooled slag has little or no hydraulic properties and

is not suitable.

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Q: How I can detect slag in Portland Composite Cement

Dear Sir, How I can detect Slag or quantity of slag mixed in portland

composite cement by chemical method? Tahmid

A:

That will be difficult because the slag will be composed mainly of lime, silica,

alumina and iron oxide therefore undistinguishable from the clinker minerals

by chemical methods.

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Q: Raw Mill Residue

Dear Sir, is there any effect of raw mill residue on the bag house bags either

we grind finer or coarser.

A:

No, I don't expect the fineness of grinding the raw meal will have any effect

on the baghouse bags.

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Q: How I can estimate flyash,slag,limestone content in portland composite

cement

How I can estimate of Fly ash, slag ,limestone in portland composite cement

A:

The best way would be by X-ray diffraction.

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Q: Dear Sir, we are using high sulphur coal. Clinker Lt. wt. is 1300 -1350. we

want to increase C3S more than 45%. Please advice for required liquid phase

in the clinker. Our kiln feed LSF= 112, SM= 2.24, Al2O3= 2.9, Fe2O3= 2.4.

Our clinker SO3= 2.6 to 2.8

A:

To achieve a higher C3S content in clinker you need to raise the lime

saturation of the clinker. Your kiln feed lime saturation is high but so is your

clinker SO3. The full analysis of kiln feed, coal ash and clinker would be

required to properly adtvise you this.

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Q: How to fix the raw mix ratio with following raw materials

Dear Sir, I have following composition of raw materials. LOI SiO2 Al2O3

Fe2O3 CaO MgO Limestone 42.58 3.24 0.79 0.38 50.01 1.24 Clay 5.87 74.98

8.80 6.20 0.98 0.24 Iron Ore 4.65 9.16 2.00 83.04 0.06 0.41 By using of these

raw materials I want to fix the raw mix with following modulus but I can't

success to get following target modulus in raw mix HM=2.3 SM=2.5 IM=1.5

Here, I am kindly asking what are the ratios of raw mix to get the above

modulus of the raw mix. If not, what kind of correcting raw mat should I

used to obtain above target modulus in raw mix? Your valuable suggestions

will be very appreciable for me Regard Dinesh Koirala

A:

T&he hydraulic modulus is an outdated concept. Better is to use the lime

saturation factor. In order to control 3 rations in the mix you need four raw

materials. You only have 3 so can only control 3 ratios.

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Q: Belite

What is the major difference between alpha-belite and beta-belite ? Higher

content of which crystal form of belite is preferable ? Explain.

A:

These are different crystal forms of the belite. beta-belite has the most

hydraulic reacttivity and this therefore preferred. It is what is normally

produced in an industrial cement kiln.

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Q: Laterite

Hello Dr., Can you suggest any material that would replace laterite and still

produce high strength cement ? If possible ,please state the chemical

composition of such material.

A:

Laterite is normally added to cement raw mixes to increase the Fe2O3

content of the mix. Therefore any source of iron oxide can be used instead

of laterite. Alternatively a higher alumina modulus mix can be prepared

which will reduce the amount of laterite used and still produce high strength

cement. The Fe2O3 containing clinker mineral (C4AF) does not make a major

contribution to cement strength.

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Q: Coating

Hi Sir, What is coating index ? what is its significance ?

A:

The coating index is an indicator the likelihood that a raw mix of a particular

chemistry will give rise to coating with the cement rotary kiln.

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Q: Clinker Burning

Hi Sir, What is the general expression for calculating burning temperature of

clinker ?

A:

There is no general expression for calculating the burning temperature of

clinker.

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Q: Coal Ash

Hello Dr., How do coal ash gets added to the kiln feed ? Please clarify with

explanation

A:

The fine coal burnt in the kiln contains some ash. That ash is predominatly

silica and alumina so the ash combines with the lime from the limestone to

produce the clinker minerals C3S, C2S, C3A and C4AF.

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Q: Effect of Ash

What is the effect of ash on LSF, SM, AM of clinker ?

A:

Coal ash is mainly composed of silica, alumina and iron oxide so the LSF is

reduced. The effect on silica and alumina modulus depends on the exact

composition of the ash.

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Q: Hydraulic Modulus

Hello Sir, What is the significance of hydraulic modulus in the present days ?

A:

The hydraulic modulus is the ratio of CaO to the sum of SiO2, Al2O3 and

Fe2O3. It was often used historically and for good cement quality, it should

be between 1.7 and 2.3. However, this is not a useful as the lime saturation

factor so it does not have major significance today.

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Q: industrial waste in cement

Sir,Can we use zinc metallurgical waste, jarosite in cement manufacturing

process either as raw material for raw meal preparation or as set retarder

by partial replacement of gypsum? anybody in the world uses hazardous

waste jarosite in cement manufacturing process?

A:

I am not aware of anyone using jarosite in the cement manufacturing

process. The first step would be to know the chemical composition of the

jarosite.

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Q: Online Analyser for Raw Mix

Hello Sir, Can you provide some information about online analyser used for

monitoring raw mix ? Nowadays what are the online analysers cement

manufacturer use for controlling the raw mix ? Please advice.

A:

The most widely used would be Gammametrics or the Scantech analysers.

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Q: Lime Saturation Factor (LSF)

Hello Sir, It is found that LSF of output of the Raw mill (Vertical Roll Mill) is

94% whereas the LSF of Kiln feed is 95%. Can you provide any possible

reason for this change ? Please advice.

A:

This might arise from how the dust from the kiln is handled. The kiln feed

will contain the dust. The raw mill product might not contain the dust.

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Q: kiln not giving rated production

sir our kiln with capacity 600 tonns per day is not going on rated capicity.it

is operating upto 60% of rated capacity.As soon as feed rate is increased

proper clinker formation does not take place also sometimes there is sudden

feed surge.It also accompanies decaoting and ball formation.What can be

the possible causes?

A:

There could be many causes. A technical audt is required to identfy the

possible causes.

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Q: what happend in kiln when latarite is not gone in rawmeal

A:

The laterite is presumably added for it's iron oxide content. Therefor if has

not gone into the raw meal for whatever reason there will be a deficiency of

iron oxide in the meal in the kiln. That will mean less liquid phase or flux and

changed properties of the remaining flux. The clinker will be more difficult to

combine therefore fuel consumption is likely to be higher. Coating tendency

will change and perhaps the coating will be stripped out of the kiln.

Potentially the clinker will be over 100% lime saturated and there will be

high levels of residual free lime.

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Q: Excessive Dust in Preheater

Sir our CF is 1.85 you said that it is caused by excessive dust loss from the

top stage of the preheater. So how do we reduce this dust loss from Pre

Heater Section?

A:

That depends on the wider situation. Things to be checked are the condition

of the internal fittings (dip tubes, feed distribution plates, feed flaps) in the

preheater. Also the drafting of the preheater, excess air, inleaking air, etc.

Also the fineness of the kiln feed. The give more specific advice a technical

audit would be required. 

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Q: Excessive fines in raw material

Hi Sir I posted a question on excessive fines in raw material for which you

said that the fines can be added directly to the VRM separator Thanks for

your answer. If we do the above exercise will our clinker factor come down?

(now it is at 1.85). Is there any other plant where the above exercise is

successfully followed. Thanks

A:

There is no reason why the raw mix to clinker factor would reduce from it's

current value. 1.85 is a very high factor which must be caused by excessive

dust loss from the top stage of the preheater. How you handle the fines in

the raw milling circuit will not make any difference in the top stage of the

preheater.

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Q: Excessive fines in Raw Material

Hi Sir We are having excessive fines in our raw material. this is directly

grinded by Imapct type crusher and is carried to stacker reclaimer. My

doubts are 1. Since excessive fines are there it reduces the capacity of

crusher and when it comes to raw mill it is grinded excessively. 2. Our cooler

has IKN KIDS and we also are faced with Red river formation and spillage in

cooler due to which stoppages happen often. Our suggestion is to provide

screen in crusher area to remove excessive fines thereby improving the

capacity of crusher. I have a doubt on where can the fines be supplied either

to raw mill or after raw mill based on the size. Please suggest your valuable

inputs on how to get rid of this problem.

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A:

Certainly a screen to scalp the feed to the crusher seems to be a good idea.

Whether the fines can be added back to the raw mill feed or product will

depend on the sieve residues of the fines. One solution would be to add the

fines to the separator of the raw mill. Then any material already fine enough

will go straight to the product while the coarser material will be returned to

the mill for regrinding.

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Q: method of raw mix pile avg calculation according to hourly tonnage in

excel?

A:

This requires that the weighted average of each oxide in the pile be

calculated after each new sample using the analysis of the sample and the

wieght of material added to the pile. The composition to correct the pile to

target can then be calculated.

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Q: Sir, Why we multiply with 2.8 to Sio2, 1.18 to Al2O3 & 0.65 to Fe2O3 in

LSF formula i.e. CaO/(2.8SiO2+1.18Al2O3+0.65Fe2O3)

A:

These are the coefficients in the Lea and Parker formula for the maximum

combinable lime in Portland cement clinker. They are derived from the

phase equilibria of the CaO-SiO2-Al2O3-Fe2O3 system.

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Q: How 5 or more components raw mix design are calculated ?

it is too important for me please answer it to me

A:

By setting up 5 simultaneous equations with the 4 targets in the raw mix

that you want to control. Then solvng those simultaneous equations.

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Q: chemical and physical analysis for white cement (LSF- SIM -ALM & C3S -

C2S - C3A - C4AF)?

A:

LSF = 95%, SM = 4+, AM = 10+. C3S = ~60%, C2S = ~20%, C3A = ~15%,

C4AF <1%. Strengths higher than grey cement due to higher silicate

content.

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Q: lime stone is pure cristaline calcite @ 87% T.CO3 and in the same bench it

has very low T.CO3% as pegmatite or gniees with 16 % MgO , sir our raw mill

is 170 TPH VRM and is there any difficulty of raw mill fine grinding of this

calcite and gniees

dear sir , good evening. here in kenya we are going to instal 3000 TPD

clinker unit with 170 TPH VRM for raw mix and is there any difficult to get

fine grinding like 212 mic residue up to 2% and 90 mic residue up to 18%

with this lime stone pure calcite crystalline and bottom layer is very low

phlegmatic or genies with 2 to 16% mgo. one place we find low cao stone

with 56 silica and i came to know that this stone silica should not be good

reactive as it formed from calcite washed with water and cao is eliminated. i

think that in ball mill we can maintain finesse as we required. please give

me reply at the earliest thanking you RAO . Y . S NATIONAL CEMENT CO. LTD

NAIROBI - KENYA

A:

There is no reason to suppose that a VRM would not be able to grind this

material while a ball mill would.

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Q: Difference Between Limestone & Shale

How to Distinguish between Limestone & Shale with chemical compostion.

A:

Limestone is a form of calcium carbonate. Pure limestone has 56% CaO.

Shale is geologically altered clay so composed of alumino silicate minerals.

The CaO content of shale is very low. It's silica content is likely to be around

50-60%.

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Q: Why we set carbonates 77 or 76 per in pile formation ?

what happened when we increase the carbonates or decrease in pile like 70

or 80? why we set 80 or 70 per carbonates in pile formation?

A:

Because that level of carbonate will give you the required amount of CaO in

the pile. If you set lower then you will need to add high grade limestone at

the raw mill to bring the kiln feed LSF up to target. If you set higher then

you will have to add silica, alumina or iron oxide at the raw mill to bring the

LSF down to target.

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Q: crusher for kaolin

Hi sir What is the best crusher for Breaking kaolin? Also in our factory for

kaolin Breaking use of jaw crusher & Gyratory crusher.What do you think

about using impact crusher? Best regards

A:

Impact crushers are normally used for brittle materials. Kaolin is normally

quite soft. The only problems that might arise are if the kaloin is wet and

sticky.

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Q: low liter weight clinker and decrease product

LSF X- RAY : 90-92 SIM : 2.3-2.4 ALM :1.3-1.4 LSF CHEMICAL :88-90 SIM :2.4

ALM 1.3

A:

Well, it seems that you X-ray is reading high on CaO, if the chemical

analyses are correct. That does not explain the decreased productivity. My

suspicion that there is some other problem.

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Q: How to calcualate or simulate the alkali enrichment in the preheater

when alkali rich material is used as additive?

I am substituting Trass for Sand to get silica in the raw mix. The trass

contains 1.2% K2O and 3.2% Na2O. Consequently, the total alkalies in the

raw meal inceases from 0.34 % to 0.56%. How calculate or simulate the

alkali enrichment in the preheater circulation material?

A:

It is of course possible to do this with an Excel based model of the alkali

cycles, as I demonstrated at Cemtech in Dubai and Jakarta. However, it is

not just a question of calculating. That depends on yhe volatility of the Na2O

and K2O, which is dependent on the amount of chloride and sulphate

present. It is too complicated for a simple calculation and depends on a

model. However at 0.56% total alkali there should be no problems.

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Q: what is silica modules & alumina modules give me defination.

A:

Silica modulus is the ration of the %silica to the sum of the %alumin and

%iron oxide. Alumina modulus is the ration of the %alumina to %iron oxide.

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Q: LSF FORMULA

Dear sir,kiln feed is: Cao=42.3%, Mgo=2.7% ,sio2=12.90%, Al2o3=3.37%,

Fe203=2.23% .some plants do not consider Mgo in calculation of LSF and

they use the formula LSF=100*cao/(2.8*sio2+1.18*Al203+0.65*Fe2o3)is it

right?or they should add 0.75*Mgo in numerator. if we want to announce

kiln feed LSF with above analysis what should we say about LSF?

LSF=102(without Mgo)or LSF=105(with considering Mgo).

A:

Normally for kiln feed LSF the MgO is not included.

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Q: Finess of raw meal influenced snow man

Hi Dr Clarck, Can raw meal fineness(212) influenced formation of snowman?

A:

Only indirectly. This will not be the primary cause of snowman formation in a

cement kiln clinker cooler.

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Q: what is the essential raw materials to produce white cement

A:

Raw materials which give the required CaO, SiO2 and Al2O3 content with the

minimum of Fe2O3 contamination. No other first row transition elements can

be tolerated, but they are rare components on cement raw materials or

fuels.

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Q: Raw mix design of 4 components

How 4 components raw mix design are calculated and what are the LSF,SM,

and AM for the mix design?

A:

Proportioning 4 raw material components to LSF, SM and AM targets

involves setting up and solving 4 simultaneous equations. The LSF, SM and

AM targets are variables within those simultaneous equations. I suggest

that the enrol of the CemNet Cement Manufacturing Technology course.

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Q: Sweetner grade (High Grade ) Lime stone

Sir, Pls tell me, is it possible that CaO % 57 in High grade lime stone (Its LSF

aprox 1050)

A:

The maximum CaO content in pure limestone (calcium carbonate) is 56%.

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Q: The ingredients in ASTM C150....

Dear Dr. Clark, I have some questions on ASTM C150/C150m-11 Standard

Specification for Portland Cement revised in April 1, 2011. There are several

ingredients specified in Item 5. Ingredient of the specification, 5.1.1

Portland Cement Clinker 5.1.2 Water or Calcium Sulfate 5.1.3 Limestone (not

more than 5 %) 5.1.4 Inorganic Processing additions (not more than 5 %)

5.1.5 Organic Processing additions (not more than 1 %) 5.1.6 Air-entraining

addition Would you be more specific about the following aspects? 1. What's

the meaning of Water of "5.1.1 Water or Calcium Sulfate" ? 2. What's the

meaning of Processing additions ? What's the difference between 5.1.3 and

5.1.4 ? 3. What's the maximum addition rate ? Not more than 10 %? 4.

What's the meaning of 5.1.5 ? Does it mean grinding aids? 5. What's the

purpose the us government revised the specification like this? For the

reduction of CO2 emission? I really thank you for your help up to now! Best

Regards.

A:

Dear Obong, The short answer is I don't knnow exactly. I presume the

reference to water or calcium sulphate is saying that the calcium sulphate

addition might be gypsum with 2 molecules of water of crystallisation. I

think inorganic processing additions are pfa, gbs, etc. so the same as

limestone. As far as I I am aware the total additions are 10%, including the

gypsum. I think organic processing additions are grinding aids and organic

quality improvers. I don't know the motives of ASTM or the US Government

but this seems to be a move towards EN197 CEM I cements.

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Q: Intensity of kiln feed

Hi sir How we can get the analyze of material , from intensity of kiln feed?

Best regard

A:

I presume you mean the intensify of the fluorescent X-radiation from a kiln

feed sample in X-ray fluorescense spectrometer. These are calibrated so

that the SiO2, Al2O3, Fe3O3, CaO, etc.content of the kiln feed is correlated

with the X-ray intensity.

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