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Section 1

Description of the Process and the Design Requirements

Copper is an excellent conductor of electricity and heat. It resists corrosion and it is

easily fabricated into wire, pipe and sheets. Copper's most exploited property is its high

electrical conductivity in conjunction with its excellent corrosion resistance, formability and

joinability. Its early uses were in jewelry, utensils, tools and weapons. Today, copper find their

way in applications ranging from building constructions and industrial equipment to

transportation, telecommunications, power transmission, consumer electronics, and other high-

tech products. Moreover, it plays a major role in numerous applications such as in piping,

coinage, and in many household products. Alloyed with other elements, copper is transformed

into compounds, such as brass, bronze, and cupro-nickels.

Copper is most commonly present in the earth's crust as copper-iron-sulfide and copper

sulfide minerals. The concentration of these minerals in an ore body is low. In this sense,

metallurgical methods such as pyrometallurgical and hydrometallurgical method are employed

to extract copper from these ores to form concentrated copper products (Davenport et al.,

2002).

Extracting copper from copper-iron-sulfide ores by the pyrometallurgical method entails:

(a) isolating an ore's Cu-Fe-S2 mineral particles into a concentrate by froth flotation, (b) smelting

this concentrate to molten high-Cu matte, (c) converting the molten matte to impure molten

copper and (d) electro-refining this impure copper to ultra-pure copper (Davenport et al., 2002).

On the other hand, hydrometallurgical extraction entails: (a) sulfuric acid leaching of Cu

from broken or crushed ore to produce impure Cu-bearing aqueous sotution, (b) transfer of Cu

from this impure solution to pure, high-Cu electrolyte via solvent extraction and (c) electroplating

pure cathode copper from this pure electrolyte (Davenport et al., 2002).

About 80% of the world's copper-from ore is produced by the pyrometallurgical method.

The other 20% is produced by the hydrometallurgical method. Moreover, both processes have

their corresponding advantages and disadvantages as shown in Table 1.1 below which served

as the basis for selecting the method used (Davenport et al., 2002).

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Table 1.1 Advantages and Disadvantages of the Hydrometallurgical and Pyrometallurgical Method

Metallurgical Methods Advantages Disadvantages

PyrometallurgicalMethod

cheap; produces saleable by-products such as sulfuric acid;generates clean concentrate

high dust potential and gasemission

HydrometallurgicalMethod

low dust potential; low gasemission; cleaner workplace

residue disposal problem; largepower requirement; labor intensive

The most effective technique of isolating the Cu minerals in pyrometallurgical method is

by froth flotation. This process causes the Cu minerals to become selectively attached to air

bubbles rising through a mixture of water and finely ground ore. Selectivity of flotation is created

by using reagents which make Cu minerals water repellent while leaving waste minerals wetted.

These reagents cause Cu minerals to float on rising bubbles while the other minerals remain

unfloated. The floated Cu-mineral particles overflow the flotation cell in a froth to become

concentrated (Davenport et al., 2002).

The aim of this project is to design five flotation cells (1st, 2nd and 3rd rougher, and 1st and

2nd cleaner) for use in the extraction of copper from copper-iron-sulfide ores using froth flotation

process of the pyrometallurgical method which would increase the Cu extraction efficiency. With

this, for the plant to produce 500, 000 tons of concentrated copper granules, 963,800 tons of

iron concentrate and 201,120 tons of white metal per year; the first rougher flotation cell must be

able to handle 1,463,800 tons of granulated copper ores per year.

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Section 2

Process Definition

2.1 Process Concepts Chosen

Flotation is a physico-chemical separation process that utilizes the difference in surfaceproperties of the valuable minerals and the unwanted gangue minerals. The theory of froth

flotation is complex, involving three phases: solid, liquid, and froth with many sub-processes and

interactions (Wills & Munn, 2002).

The process of material being recovered by flotation from the pulp comprises three

mechanisms:

(1) selective attachment to air bubbles or true flotation

(2) entrainment in the water which passes through the froth

(3) physical entrapment between particles in the froth attached to air bubbles often referredto as aggregation

The attachment of valuable minerals to air bubbles is the most important mechanism

and represents the majority of particles that are recovered to the concentrate. Although true

flotation is the dominant mechanism for the recovery of valuable mineral, the separation

efficiency between the valuable mineral and gangue is also dependent on the degree of

entrainment and physical entrapment. Unlike true flotation, which is chemically selective to the

mineral surface properties, both gangue and valuable minerals alike can be recovered by

entrainment and entrapment. Drainage of these minerals occurs in the froth phase and

controlling the stability of this phase is important to achieve an adequate separation. In industrial

flotation plant practice, entrainment of unwanted gangue can be common and hence a single

flotation stage is uncommon. Often, several stages of flotation called circuits are required to

reach an economically acceptable quality of valuable mineral in the final product.

True flotation utilizes the differences in physicochemical surface properties of particles of

various minerals. After treatment with reagents, such differences in surface properties between

the minerals within the flotation pulp become apparent and, for flotation to take place, an air

bubble must be able to attach itself to a particle, and lift it to the water surface (Wills & Munn,

2002).

Figure 2.1.1 illustrates the principles of flotation in a mechanical flotation cell. The

agitator provides enough turbulence in the pulp phase to promote collision of particles and

bubbles which attachment of valuable particles to bubbles and their transport into the froth

phase for recovery.

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Figure 2.1.1 Froth Flotation Process (Wills et al., 2002)

The process can only be applied to relatively fine particles, because if they are too large

the adhesion between the particle and the bubble will be less than the particle weight and the

bubble will therefore drop its load (Trahar & Warren, 1976; Crawford & Ralston, 1988; Finch &

Dobby, 1990).

In flotation concentration, the mineral is usually transferred to the froth, or float fraction,

leaving the gangue in the pulp or tailing. This is direct flotation and the opposite is reverse

flotation, in which the gangue is separated into the float fraction.

The function of the froth phase is to enhance the overall selectivity of the flotation

process. The froth achieves this by reducing the recovery of entrained material to theconcentrate stream, while preferentially retaining the attached material. This increases the

concentrate grade while limiting as far as possible the reduction in recovery of valuables. The

relationship between recovery and grade is a trade-off that needs to be managed according to

operational constraints and is incorporated in the management of optimum froth stability.

The mineral particles can only attach to the air bubbles if they are to some extent water-

repellent, or hydrophobic. Having reached the surface, the air bubbles can only continue to

support the mineral particles if they can form a stable froth, otherwise they will burst and drop

the mineral particles. To achieve these conditions it is necessary to use the numerous chemicalcompounds known as flotation reagents (Ranney, 1980; Crozier, 1984; Suttill, 1991; Nagaraj,

1994; Fuerstenau and Somasundaran, 2003). Moreover, since most minerals are not water-

repellent in their natural state, flotation reagents must be added to the pulp. The most important

reagents are the collectors, which adsorb on mineral surfaces, making them hydrophobic or

aerophilic and facilitating bubble attachment. The frothers help maintain a reasonably stable

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froth. Regulators are used to control the flotation process; they either activate or depress

mineral attachment to air bubbles and are also used to control the pH of the system.

In the pyrometallurgical method, concentration of Cu ores consists of isolating an ore's

Cu minerals into a high Cu concentrate. It entails:

(a) crushing and grinding the ore to a size where its Cu mineral grains are divided from

its non-Cu-mineral grains. This process is collectively called as comminution.

(b) froth flotation which physically separates Cu minerals from non-Cu minerals to form

Cu rich concentrate and Cu barren tailing.

(c) dewatering, or solid-liquid separation, produces a relatively dry concentrate for

shipment.

2.1.1 Crushing and Grinding (Comminution)

Isolation of an ore's Cu minerals into a concentrate requires that the ore be ground finely

enough to liberate its Cu mineral grains from its non-Cu-mineral grains. The extent of grinding

required to do this is fixed by the size of the mineral grains in the ore. It is ascertained by

performing grinding or flotation tests.

Liberation of mineral grains from each other generally requires grinding to -100 pm

diameter. Slime formation begins to adversely affect flotation when particles less than -10 pm

are formed (Davenport et al., 2002).

Comminution is performed in three stages:

(1) breaking the ore by explosions in the mine (blasting)

(2) crushing of large ore pieces by compression in eccentric crushers

(3) wet grinding of the crushed ore in rotating 'tumbling mills when abrasion, impact and

compression all contribute to breaking the ore

Separate crushing and grinding is necessary because it is not possible to break massive run-of-

mine ore pieces while at the same time controlling fineness of grind for flotation.

2.1.1.1 Blasting

Blasting entails drilling holes in the mine, filling the holes with explosive and exploding

fragments of rock from the mine wall. The explosions send cracks through the rock, releasing

multipIe fragments. Fuerstenau et al., 1997, report that closer drill holes and larger explosive

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charges give smaller rock fragments. This may be useful for decreasing subsequent crushing

requirements.

2.1.1.2 Crushing

Crushing is mostly done in order to reduce the size of the large ores from the mines.

This permits ore to be transported out easily by the conveyor for grinding. Eccentric crushers

are the usual equipment in this process such as jaw crusher, gyratory crusher, cone crusher,

impact crushers and shaft crushers.

2.1.1.3 Grinding

Grinding takes the ore from crushing. It produces ore particles of sufficient fineness for

Cu mineral recovery by flotation. Grinding is always done wet with mixtures of 80 mass% solids

and 20 mass% water (Davenport et al., 2002).

The most common grinding mills are the following: (a) semi-autogenous and autogenous

mills and (b) ball milIs. The semi-autogenous or autogenous mill grinds crusher product and

prepares it for final grinding in a ball mill. Its product is usually passed over a large vibrating

screen to separate oversize pebbles from correct-size particles. The correct-size material is sent

forward to a ball mill for final grinding. The oversize pebbles are recycled through a small

eccentric crusher, and then back to the semi-autogenous or autogenous mill. This procedure

maximizes ore throughput and minimizes electrical energy consumption. The ball mill accepts

the semi-autogenous or autogenous mill product. It produces uniform-size flotation feed. It is

operated in a closed circuit with a particle size measurement device and size control cyclones.

The cyclones send correct size material on to flotation and oversize back to the ball mill for

further grinding.

2.1.2 Froth Flotation

Froth flotation is a process used to separate minerals, suspended in liquids, by attaching

them to gas bubbles to provide selective levitation of the solid particles. It is the cheapest and

most extensively used process for the separation of chemically similar minerals, and toconcentrate ores for economical smelting.

The principles of froth flotation are the following:

(a) sulfide minerals are normally wetted by water but they can be conditioned with

reagents (collectors) which cause them to become water repellent

(b) this repellency can be given selectively to Cu minerals, leaving other minerals wetted

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(c) collisions between small rising air bubbles and the now-water repellent Cu minerals

result in attachment of the Cu mineral particles to the bubbles

(d) the other wetted mineral particles do not attach to the rising bubbles.

Copper ore froth flotation entails: (a) conditioning a water-ore mixture (pulp) to make its

Cu minerals water repellent while leaving its non-Cu minerals wetted and (b) passing a

dispersed stream of small bubbles (0.5 mm diameter) up through the pulp.

These procedures cause the Cu mineral particles to attach to the rising bubbles which

carry them to the top of the flotation cell. The other minerals are left behind. They depart the cell

through an underflow system. They are mostly non-sulfide rock with a small amount of Fe-

sulfide.

The last part of flotation is creation of strong but short-lived froth when the bubbles reach

the surface of the pulp. This froth prevents bursting of the bubbles and release of the Cu mineral

particles back into the pulp. The froth overflows the flotation and into a trough. There, it

collapses and flows into a collection tank.

Copper flotation consists of a sequence of flotation cells designed to optimize Cu

recovery and %Cu in concentrate. The froth from the last set of flotation cells, after water

removal, is Cu concentrate.

To achieve a stable froth to contain the Cu mineral particles, it is necessary to use the

numerous chemical compounds known as flotation reagents such as collectors, and modifiers

frothers. These flotation reagents are presented in the sections that follow.

2.1.2.1 Collectors

Collectors are reagents that are used to

selectively adsorb onto the surfaces of particles. They

form a monolayer on the particle surface that

essentially makes a thin film of non-polar hydrophobic

hydrocarbons as shown in Figure 2.1.2. The reagents

which create the water repellent surfaces on sulfide

minerals are hetero-polar molecules. They have a

polar end and a non-polar hydrocarbon end. They attach their polar end to the mineral surface

which is also polar, leaving the non-polar hydrocarbon end extended outwards. It is this

orientation that imparts the water repellent character to the conditioned mineral surfaces.

Figure 2.1.2 Interaction of collector

with mineral surface

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Typical collectors for flotation of metallic sulfides and native metals are xanthalates, and

dithiophosphates of two to six carbon atoms (Wills & Munn, 2002).

2.1.2.2 Modifiers

Modifiers are used extensively in flotation to modify the action of the collector, either by

intensifying or reducing its water-repellant effect on the mineral surface. They thus make

collector action more selective towards certain minerals. For instance, separating sulfide

minerals such as chalcopyrite from pyrite relies on modifying the surfaces of non-Cu sulfides so

that the collector does not attach to them while still attaching to Cu sulfides.

The most common modifier is the OH (hydroxyl) ion. Its concentration is varied by

adjusting the basicity of the pulp with burnt lime (CaO), occasionally sodium carbonate

(Davenport et al., 2002).

2.1.2.3 Frothers

Collectors and modifiers give selective flotation of Cu minerals from non-Cu minerals.

On the other hand, frothers create the strong but short-lived froth which holds the floated Cu

minerals at the top of the cell. They give a froth which is strong enough in the flotation cell to

support floated Cu minerals and breaks down quickly once it and its minerals overflow the cell.

Branch chain alcohols are the most common frothers (Mulukutla, 1993). These alcohols are

classified as natural (e.g. pine oil or terpinol) or synthetic (e.g. methyl isobutyl carbinol,

polyglycols and proprietary alcohol blends) (Chevron Phillips, 2002). Frothers stabilize the froth

by absorbing their OH polar end in water while their branch chains form a cross-linked network

in air. The froth should not be long-lived, so the branch chain hydrocarbon tails should not be

too long.

2.1.2.4 Flotation Equipment

Various types of flotation machine designs can be classified into different categories

based on the methods used for the generation and introduction of air bubbles into theequipment (See Figure 2.1.4). Each of the techniques of air bubble generation and particle-

bubble contact along with the special features associated with different kinds of equipment has

its own advantages and limitations. These must be considered carefully in selecting the

equipment for a specific application.

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Electrolytic Flotation Units

Electrolytic or electroflotation is based on the generation of hydrogen and oxygen

bubbles in a dilute aqueous solution by passing direct current between two electrodes. Choices

of electrode materials include aluminum, platinized titanium, titanium coated with lead dioxide,

and stainless steel of varying grades. Figure 2.1.5 illustrates the basic arrangement of an

electrolytic flotation unit.

This method is attractive for the separation of small particles and fragile flocs. To date,

electroflotation has been applied to effluent treatment and sludge thickening. However, because

of their bubble generation capacity, these units are found to be economically attractive for small

installations in the flow-rate range of 10 to 20 m3/h. The main drawback of the electroflotation

Figure 2.1.4 Classification of flotation equipment based on the generation and introduction of air

bubbles (Perry et al., 1999).

Figure 2.1.5 Schematic diagram of an electrolytic flotation plant (Perry et al., 1999)

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units is associated with the electrodes in terms of their fouling requiring mechanical cleaning

devices and their consumption needing replacement at frequent intervals.

Dissolved-Air Flotation Units

Dissolved-air flotation entails saturating the process stream with air and generating air

bubbles by releasing the pressure. Particle-bubble contact is achieved by the direct nucleation

and growth of air bubbles on the particles, and very little mechanical agitation is employed. The

dissolved-air precipitates in the form of fine bubbles in the size range of 20 to 100 mm. This

method of air bubble generation does not require the addition of frother-type chemical reagents

and often limits the total quantity of aeration possible. As such, dissolve-air flotation systems are

used to treat process streams with low solids concentration (0.01 to 2 percent by volume).

Vacuum flotation and pressure flotation are the two main types of dissolved-air flotation

processes, with the latter being most widely used.

The dissolved-air flotation process is most commonly used for sewage and potable water

treatment. It is also gaining popularity for the treatment of slaughterhouse, poultry processing,

seafood processing, soap, and food processing wastes (Zoubulis et al., 1991).

Dispersed-Air Flotation Units

Dispersed-air flotation involves the generation of air bubbles, either pneumatically or by

mechanical means. In both cases, relatively large air bubbles (at least 1 mm in size) are

generated. In order to control the size and stability of air bubbles, frothers are added to the

flotation devices. These devices represent the workhorses of the minerals industry in

beneficiating metallic and nonmetallic ore bodies and cleaning of high-ash and high-sulfur coals

in which feed streams contain relatively high percent solids (5 to 50 percent by volume), and

high throughputs are maintained (in excess of 4000 t/h). Handling of large quantities of solids in

these flotation devices requires such special design considerations as maintaining the solids in

Figure 2.1.6 Schematic diagram of a dissolved air flotation plant (Perry et al., 1999)

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suspension, promoting particle-bubble collisions leading to attachment, providing a quiescent

pulp region below the froth to minimize pulp entrainment, and finally providing sufficient froth

depth to permit washing and drainage of hydrophilic solids entering the froth region.

Mechanical Cells

Figure 2.1.7 presents a schematic representation of a typical mechanical device

commonly known as a flotation cell. It is characterized by a cubic or cylindrical shape, equipped

with an impeller surrounded by baffles with provisions for introduction of the feed slurry and

removal of froth overflow and tailings underflow. The machines receive the supply of air through

a concentric pipe surrounding the impeller shaft, either by self-aeration due to the pressure drop

created by the rotating impeller or by air injection by means of an external blower. In a typical

installation, a number of flotation cells are connected in series such that each cell outputs froth

into a launder and the underflow from one cell goes to the next one. The cell design may be

such that the flow of slurry from one cell to another can either be restricted by weirs or

unrestricted.

As illustrated in Figure 2.1.7, a mixture of

ore and water called pulp [1] enters the cell

from a conditioner, and flows to the bottom

of the cell. Air [2] or nitrogen is passed

down a vertical impeller where shearing

forces break the air stream into small

bubbles. The mineral concentrate froth is

collected from the top of the cell [3], while

the pulp [4] flows to another cell.

In the physical separation of Cu minerals from non-Cu minerals by froth flotation, the

four sets of flotation cells that are used are the following:(a) rougher-scavengers in which the incoming ground-ore pulp is floated under

conditions which give efficient Cu recovery with a reasonable concentrate grade

(b) cleaners in which non-Cu minerals in the rougher-scavenger concentrate are

depressed with CaO to give a high grade Cu concentrate

Figure 2.1.7 Diagram of mechanical flotation cell

(Perry et al., 1999)

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(c) re-cleaners which maximize concentrate grade (%Cu) by giving Fe minerals and

rock' a final depression

(d) cleaner-scavengers which, with the addition of more collectors, scavenge the last bit

of Cu from the cleaner tails before they are discarded.

Examples of mechanical cells include the Fagergren machine, Denver machine and the

Agitair flotation machine. These flotation cells are discussed in the succeeding paragraphs.

In the Fagergren machine (see Figure.2.1.8),

pulp is drawn upward into the rotor A by the rotors

lower portion B. Simultaneously the rotors upper end C

draws air down the standpipe Dfor thorough mixing with

the pulp inside the rotor E. The aerated pulp is then

expelled by a strong centrifugal force F. The shearing

action of the stator G, a stationary cage fitting closely

around the rotor, breaks the air into minute bubbles.

This action uniformly distributes a large volume of air in the form of minute bubbles in all parts

of the cell.

In the D-R Denver machine (see Figure 2.1.9),

the pulp enters the top of the recirculation well, while the

low-pressure air enters through the air passage. Pulp

and air are intimately mixed and thrown outward by the

rotating impeller through the stationary diffuser. The

collector-coated mineral particles adhere to be removed

in the froth product.

In the Agitair flotation machine (Figure 2.1.10); the impeller is a

flat rubber-covered disk with steel fingers extending downward

from the periphery. A rubber-covered stabilizer eliminates dead

spots in the agitation zone and improves bubble-ore contact. The

degree of aeration is controlled by regulating air volume on each

cell with an individual air valve.

Figure 2.1.8 Fagergren flotation

machine (Perry et al., 1999)

Figure 2.1.9 Denver flotation machine


Figure 2.1.10 Agitair flotation machine


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Flotation Columns

Flotation columns belong to the class of pneumatic devices in that air-bubble generation

is accomplished by a gas-sparging system and no mechanical

agitation is employed. Columns are built of long tubes of either

circular or square cross sections that are commonly fitted with

internal baffling. They are usually 10 or even 15 m high with a

cross sectional area of 5 to 10 m2. Figure 2.1.11 presents a

schematic of a typical flotation column unit. Inputs to the column

include preconditioned slurry feed and air and wash water spray,

which are introduced at about two-thirds of the height from the

bottom, in the bottom region, and at the top of the column,

respectively. The outputs are froth overflow, consisting of

hydrophobic particles from the top, and underflow from the

bottom of the column, carrying the non-floatable hydrophilic

particles. Flotation columns make use of the countercurrent flow

principle in that the swarm of air bubbles rises through the

downward-flowing slurry during which time transfer of hydrophobic particles occurs between the

slurry and bubble phases. The particle transfer process occurs in three distinct zones known as

collection, intermediate, and froth zones.

Table 2.1.1 Advantages and Disadvantages of Various Types of Flotation Equipment

Flotation Equipment Advantages Disadvantages

ElectrolyticFlotation Unit

Economically attractive for separation ofsmall particles and for small installations of10 to 20 m

3/h flow rates

Need for mechanical cleaningdevices due to fouling and needfor replacement at frequentintervals

Dissolved-AirFlotation Unit

Does not require addition of frother-typechemical reagents

Used for process streams withlow solids concentration

Dispersed-AirFlotation Unit

Used for feed streams containing highpercent solids and high throughput rates

Requires addition of frothers andother chemical reagents

2.1.2.5 Tailings

Flotation tailings account for 98% of the concentrator's ore feed. They are stored in large

dams near the mine property. Water is reclaimed from the dams and recycled to the

concentrator. This minimizes water consumption and avoids mixing concentrator effluents with

the surrounding water table. Furthermore, the pH of the tailings water is close to that required

for rougher-scavenger flotation so its recycle minimizes CaO consumption.

Figure 2.1.11 Schematic

diagram of a flotation column


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2.1.3 Dewatering

Dewatering methods can be broadly classified into three groups:

(a) sedimentation - rapid settling of solid particles in a liquid produces a clarified liquid

which can be decanted, leaving a thickened slurry, which may require further

dewatering by filtration.

(b) filtration - the process of separating solids from liquid by means of a porous medium

which retains the solid butallows the liquid to pass.

(c) thermal drying drying of concentrates by using rotary thermal dryers.

2.1.4 Operational Conditions

The factors or operational conditions that should be considered in the recovery of copper

by the froth flotation process include: pH, feed size, pulp density, temperature, pressure, feed

rates and reagent flow rates. These factors are discussed in the succeeding paragraphs.

pH Dependence

Flotation is carried out at alkali pHs (above 7) because most collectors are stable at

higher pH. At pH between pH (4 & 5) collectors such as xanthates will break down. Higher pHs

also minimizes corrosion of flotation cells and plumbing. Moreover, each mineral has a pH

above which it will not float called the critical pH. The critical pH is dependent on the

concentration of the collector.

Figure 2.1.3 Effects of CoIlector concentration and pH on the Floatability of Pyrite (CuFeS2),

Galena (PbS) and Chalcopyrite (FeS2) (Wak and Cox, 1934) (Davenport et al., 2002)

Note: Each line marks the boundary between float and non-float conditions for the specific mineral.

Precise float or non-float boundary positions depend on collector, mineral and water compositions.

Figure 2.1.3 shows critical pH vs collector concentration for three minerals: pyrite (FeS 2),

galena (PbS), and chalcopyrite (CuFeS2). It shows that: (a) up to pH 5 (acid pulp): CuFeS2, PbS

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and FeS2 all float, (b) between pH 5 and pH 7.5 (neutral pulp): CuFeS2 and PbS float while FeS2

is depressed, and (c) between pH 7.5 and pH 10.5 (basic pulp): only CuFeS2 floats. The most

common agent for raising the pH is lime (CaO). In the case of copper recovery from chalcopyrite

ores by froth flotation, the pH range considered is 8.5 9.5.

Feed size

For coarse-grinding processes, crushed ore particles between 50 mm and 250 mm are

reduced in size to between 40 and 300 m prior to the flotation process. The process can only

be applied to relatively fine particles, because if they are too large the adhesion between the

particle and the bubble will be less than the particle weight and the bubble will therefore drop its

load. In the case of the flotation process considered, the desired ore size is approximately 100

mm in the crusher vibrating screens system and 100m in the grinder classifier system. This

100m particle size renders the grinded ores floatable for recovery in the froth phase.

Pulp density

The feed pulp density is usually between 65% and 75% solids by weight; finer feeds

(40m to 300m) require lower pulp densities between 20% and 50%. The pulp density of the

feed should be consistent with ease of flow through the pipes. Moreover, fine-grinding circuits

may need lower pulp densities since viscosity of the pulp increases with the fineness of the

particles.

Temperature and Pressure

Froth flotation does not require strict monitoring and maintenance of pressure and

temperature. Efficiency of the recovery process does not depend so much on these two

operating conditions. In fact, copper recovery through froth flotation is often carried out at room

temperature (between 30C - 40C) and at atmospheric pressure (1 atm or 101.325 KPa).

Feed rate and Reagent Flow rates

Reagent flow rate go hand in hand with the feed rate. For a particular feed rate,corresponding reagent flow rates are required to ensure efficient recovery of copper from the

ores. The reagents which include collectors, frothers, promoters and modifiers (such as lime)

are combined with water to form process water. This process water is often mixed in the

conditioning tank with an approximately equal amount of feed from the grinder classifier

system forming the feed slurry with pulp density of 40% - 50% solids by weight.

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Refer to Table 2.2.1 in the succeeding subsection for the reagent flow rates required specific to

the flotation process considered.

2.2. Block Scheme Diagrams

The general flow of the froth flotation process in the pyrometallurgical method of

extracting copper from ores is illustrated in Figure 2.2.1 below.

Magnetics

Copper Ores

White Metal(To smelting area)

CRUSHING GRINDING FLOTATION DEWATERING

Iron Concentrate

(To Piling Yard)

Copper Concentrate(To smelting area)

Figure 2.2.1. Flotation Plant - General Process Flow

Diagram

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For the actual flow of the incoming and outgoing slurry streams with reference to the design of

the flotation cell units, refer to Section 4 - Figure 4.4.7.

Process Water

It should be noted that the process water that is introduced to the flotation process has

the following components: water, collector A (sodium dialkyl dithiophhosphate), collector B

(potassium amyl xanthate), promoter (sodium dibutyl dithiophosphate), frother (pine oil: cresol

5-10%) and modifier (lime or calcium oxide). The exact amount of the reagents and water

introduced are based on percentage composition typical to most flotation plants undergoing

copper recovery by froth flotation is given in Table 2.2.1 below.

Table 2.2.1 Composition of Process Water

Component % CompositionMass Flow Rate

(tons/yr)Mass Flow Rate

(kg/min)

Water 0.630 418824.0 969.50

Collector A(sodium dialkyl dithiophhosphate) 0.036 23932.8 55.40

Collector B(potassium amyl xanthate)

0.126 83764.8 193.90

Promoter(sodium dibutyl dithiophosphate)

0.009 5983.2 13.85

Frother(pine oil: cresol 5-10%)

0.099 65815.2 152.35

Lime (CaO) 0.100 66480.0 153.89

Figure 2.2.3 Incoming and Outgoing Streams of the Flotation Process for Cu Recovery

Total Mass In = 1.6649x106

tons/yr Total Mass In = 1.6649x106

tons/yr

White metal

2.0112x10

5

tons/yr(65.35 % Cu, 31.81 % Feand 2.84% impurities)

Flotation

Process

Process Water

(Water and Chemical Reagents)

6.648 x105

tons/yr

Note:

Chemical Reagents include collectors,promoter,

frother and modifier (such as lime)

Metallic ores

1.00012x106

tons/yr

13.53 % Cu42.56 % Fe

43.91% Impurities

Iron concentrate

5.848x105

tons/yr

(0.73% Cu, 67.46% Fe,

16.81% Impurities,

15% Moisture)

Copper concentrate

2.142x105

tons/yr

(63.53 % Cu, 15.01 % Fe,

9.46% Impurities, 12% Moisture)

Process Water

(Water and Chemical Reagents)

6.648 x105

tons/yr

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The process water characterized above is fed only once, that is, it is combined in the

conditioning tank with the grinded ores from the grinder-classifier system to form the pulp or

slurry which is fed to the 1st rougher flotation cell. From here, subsequent flotation processes

occur in all five flotation cells. After the froth from the 1st cleaner and the tailings from the 3rd

rougher have undergone the dewatering stage, process water is then recovered. This one time

addition of process water and recovery after the dewatering stage lowers the cost of raw

materials for a more economical operation.

Impurities

The impurities considered in the detailed process flow diagram of Figure 2.2.2 are made

up of various elements which comprise the chalcopyrite (CuFeS 2) ores other than Cu and Fe.

The components of these impurities with their corresponding percentage composition are shown

in Table 2.2.2 below.

Ingredients S SiO2 As Bi Sb Se Te

Content % 12.047 87.614 0.077 0.005 0.214 0.027 0.016

Rougher and Cleaner

From the process flow diagram in Figure 2.2.2 it can be observed that two kinds of

flotation cells were utilized, the rougher and the cleaner. These two flotation cells differ in their

function and role in the froth flotation process.

Roughers basic function is to float the valuable material from the incoming ground-ore

pulp under conditions which give efficient Cu recovery with a reasonable concentrate grade (15

20% Cu). On the other hand, cleaners primary objective is to depress the non -Cu minerals in

the rougher concentrate with CaO to give high grade Cu concentrate. Moreover, the last cleaner

scavenge the last bit of Cu from the cleaner tails before they are discarded.

White Metal

White metals are composed of non-magnetic materials which can be separated from the

crushed chalcopyrite ores by a magnetic separator. White metal contains a higher percentage of

copper (typically 60% - 70% Cu) than that of the magnetic (typically 9% - 15% Cu) which

undergoes flotation. This white metal does not anymore undergo flotation process due to its

high Cu content, but is directly transported to the smelting plant to serve as one of the raw

materials in the smelting process aside from copper concentrate.

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Re-grind Ball Mill or Tumbling Mills

The function of the re-grind ball is to ensure that the tailings that come out from the 1 st

rougher, 3rd rougher and 1st cleaner are well mixed before it is introduced to the 2nd cleaner. In

this case, when the mill is rotated, the mixture of reagents, water and grinded ore is intimately

mixed to ensure that this slurry that enters the 2 nd rougher flotation cell is free from clumps for

efficient flotation process. Grinding in this stage of the process is usually performed wet to

provide a slurry feed to the flotation process (Wills &Munn, 2006)

2.3 Basic Assumptions

2.3.1 Production Capacity & Product Specifications

The aim of this project is to design a flotation cell for use in the pyrometallurgical method

of copper extraction from copper-iron-sulfide ores. This copper recovery of process will have an

annual production of 214,200 tons of copper concentrate containing 63.53%Cu and 584,800

tons of iron concentrates containing 67.46%Fe both in the form of granules. Moreover,

production of white metal containing 65.35%Cu and 31.81%Fe will be 201,120 tons per year.

With this, the flotation plant will operate 24 hours a day for 300 days a year.

2.3.2 Location

The copper flotation plant is located in Toledo City, Cebu, Philippines. Since the area is

known to have one of the largest copper reserves in the country and is famous for its mining

industry, the city was chosen for the plant. The place is near the sea and the main road, thus

the concentrated copper products can be easily transported through sea and land. The plant

would also provide employment to the constituents of the locality which would result to

economic growth in the region.

Figure 2.3.2.1 Location of the Flotation Plant

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2.3.3 Battery Limits

In this design project, included are the chemical and mechanical engineering design of

the five flotation cells (1st, 2nd and 3rd rougher, and 1st and 2nd cleaner) which covers the

materials of construction, sizing requirement and power requirements. Basically, these five

flotation cells have the same design but they differ only on their individual capacities. Included

as well are the specifications of the miscellaneous or auxiliary equipments necessary for the

feed preparation before it enters the flotation cell. This auxiliary equipment include the following:

crusher, vibrating screen, ball mill grinder, conditioning tank, pump, pipes and conveyor.

However, this design project does not take into account the design specifications of the process

control equipment and the storage tanks of the raw materials and products, and the details of

the dewatering stage of the flotation process. A summary of the inside and outside battery limits

of this design project is presented in Table 2.3.3.1 below.

Table 2.3.3.1 Flotation Cell Battery Limits

Inside Limits Outside Limits

Chemical Engineering Design

(Volume Requirement; Sparger System - Superficial

Gas Velocity Requirement, Sparging Hole Diameter;

Agitation System Agitator Dimensions, Power

Requirement)

Mechanical Engineering Design

(Support; Materials of Construction)

Miscellaneous Equipment Specifications(Ball Mill Grinder; Conditioner Tank; Spiral Classifier;

Pipes and Pumps)

Process Control Equipment Specifications

Miscellaneous Equipment Specifications

(Vibrating Screens; Thickener; Drum Filter;

Crusher; Re-grind Ball Mill and Magnetic

Separator)

2.3.4 Definition of In- and Out-going streams

In the flotation process, the feed is the granulated copper-iron-sulfide ores coming from

the ball mill grinder. To maximize the recovery of copper, three flotation cells are used wherein

the tailings from the first flotation cell is carried over to the succeeding flotation cells to extract

copper that has not been extracted from the previous flotation cell. With this, two streams come

out of each flotation cell, the tailings and the froth. The froth contains a higher copper

percentage than the tailings.

The granulated copper ore that comes in to the first flotation cell contains 6.41% copper.

Subsequent flotation process occurs in the five flotation cells namely: 1 st rougher, 2nd rougher,

3rd rougher, 1st cleaner and 2nd cleaner. The final froth and tailings which comes out from the

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five flotation cells system contains 31.5% copper and 40.93%Fe respectively. This final froth

and tailings undergoes dewatering process to produce concentrated copper and iron granules.

For the plant to produce 214,200 tons of concentrated copper granules, 584,800 tons of

iron concentrate and 201,120 tons of white metal per year, the flotation process must be able to

handle 1,463,800 tons of granulated copper ores per year.

2.4 Economic Margins

Table 2.4.1 Cost of Raw Materials

Raw Material Flowrate (tons/yr) Unit Price (Php/ton) Price (Php/yr)a

Copper ore 1,000,120.0 30,000 3.00036 x1010

Processed water 664,800.0

Water 418824.0 31.99 1.33982 x107

Collector A 23932.8 3,765 9.01070 x107

Collector B 83764.8 4,025 3.37153 x108

Promoter 5983.2 4,553 2.72415 x107

Frother 65815.2 2,866 1.88626 x108

Lime 66480.0 1000 66.48 x106

Total Cost 3.0727 x1010

Source:a

Philippine Associated Smelting and Refining Corporation (PASAR)

Table 2.4.2 Estimated Price of Product

Product Flowrate (tons/year) Unit Price (Php/ton) Price (Php/yr)a

Copper concentrate 214,200 135,000 3.9627x1010

Iron concentrate 584,800 100,000 6.4328x1010

White metal 201,120 135,000 2.7151x10

10

Total Revenue 1.31106x1011

Source:a

Philippine Associated Smelting and Refining Corporation Annual (PASAR)

For the whole process to be economically attractive, a maximum economic margin of 0.3 30% is

required. To be economically attractive, the economic margin must be equal to or lower than

this maximum value. With this, economic margin is defined:

=

= 3.072710101.311061011 = 23.44%

The flotation process gives an economic margin of 23.44%. Hence, the process is economically

attractive.

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Section 3

Chemical Engineering Design of Equipment

3.1 Volume Requirement

A plot of % copper recovery versus flotation time of a mechanical cell obtained from

experiment which is specific to the system considered is needed in calculating for the residence

time of the flotation process. From this plot, the flotation time corresponds to the residence time

of the flotation process. This plot is shown Figure 3.1.1 below.

Although two metals (copper and iron) are recovered in this flotation process, copper is

the one that goes into the froth phase by selective attachment of the bubbles and the iron

together with the impurities are the ones that goes into the tailings. Residence time in each

flotation cell is dependent on the time needed for the bubbles to recover copper into the froth

phase which is dependent as well in the concentration of copper in the slurry. This is the reason

why the determination of the residence time is based on percentage copper recovery alone.

In calculating for the % copper recovery of the flotation cell unit, equation 3.1 from Wills

and Munn (2006) below is used.

% = ()( ) 100

Figure 3.1.1 Flotation behavior of copper ores in various flotation cells

(3.1)

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(3.2)

where c is the % Cu in the concentrate, f is the % Cu in the feed and t is the % Cu in the

tailings.

Prior to the calculation of the volume for each flotation cell, pulp density is first calculated

using equation 3.2 (Wills & Munn, 2006).

, = 1000 100100 + (1000)where: s is the density of the solids and x is the % solids by weight.

In calculating for the solids density s, equation 3.3 below is used.

= where: Xiis the weight fraction of each component in the pulp and i is the density of each pulp

component. In this case, the solids consist of Cu and Fe which has a density of 8960 and 7870

kg/m3 respectively. The impurities are taken to be 1600 kg/m 3 which typical to most rock

materials (Microsoft Encarta 2007).

After calculating the pulp density, the volume requirement of each flotation cell is then

determined. For different % copper recoveries for each of the five flotation cells (1 st, 2nd and 3rd

rougher; 1st and 2nd cleaner), different residence time is obtained. With this residence time, the

volume of each flotation cell is calculated using equation 3.2 below (Perry et al., 1984).

= ( )/where: is the flotation time in minutes, G is the mass flow rate in kg/min, P is the pulp volume

per unit mass of dry solids (reciprocal of pulp density) in m3/kg and V is the cell volume in each

of the flotation cell unit in m3 with N number of cells.

It must be noted that the total volume of the flotation cell unit is divided bythe number of cells N to get the volume per flotation cell. The number of flotation cells is set to

get a volume of 8 to 10 m3 which is the typical volume range of flotation cells used in the

metallurgical industry for the recovery of copper by froth flotation. A safety factor of 20% for the

flotation cell working volume is taken into account to obtain the actual volume.

The number of cells N in each flotation cell unit, % copper recovery, residence time,

working cell volume and actual cell volume is given in Table 3.1.1 below. Refer to Appendix B.1

for the detailed calculations.

(3.2)

(3.3)

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Table 3.1.1 Flotation Cell Sizing Requirements

Flotation Cell

%

Copper

Recoverya

Residence

Time

(min)

Number of

cells per unit

(N)b

Flotation Cell Volume (m3) c

Working volume

V

Actual volume

Va

1

st

Rougher 91.61 10 3 7.23 8.682nd Rougher 92.35 10 14 7.79 9.36

3rd Rougher 83.02 5.0 1 7.95 9.54

1st Cleaner 90.81 10 4 8.13 9.76

2nd Cleaner 68.31 2.5 4 7.00 8.41

*Note:a

Refer to Appendix B.1 for the calculation of % Copper recoveryb

Number of flotation cells is set to get a volume of 8 to 10 m3which is the typical volume range of

flotation cells used in the industry.cThe average working flotation cell volume and actual flotation cell volume for the five flotationcells are 7.62 m

3and 9.15 m

3respectively.

For this design project, the volume is the one chosen to be dependent on . This is

because; the project aims to produce a specified amount of products (copper concentrate, iron

concentrate and white metal) in a year for the operation to economically sound. Although

installing a small flotation cell (requiring longer residence time) would mean a smaller capital

investment; a larger flotation cell (requiring shorter residence time) proves to be more

economically profitable in the long run as the plant continues to operate. This is because; time

equates money which can take the form of power requirement, labor cost and operating

expenses. Aside from this, the plant has to keep up with the increasing demand of the market

which is time dependent as well.

It must be noted that the results of the actual flotation cell volume in Table 3.1.1 above

are approximately the same. With this, for the purpose of easier and faster fabrication of the

equipment, the average volume of the flotation cells above is taken and a uniform design for all

five cells is also presented along with the designs for each of the five flotation cells using their

calculated actual cell volume respectively.

3.2 Sparger System

3.2.1 Superficial Gas Velocity Requirement

In calculating for the superficial gas velocity that is introduced to the flotation cell to

render the desired mineral floatable, parameters such as collection capability and carrying

capacity are considered.

The cross-sectional area of the flotation cell is used to calculate for the carrying capacity

Ca is given by equation 3.5.

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= where m is the mass flow rate and A is the cross-sectional area of the flotation cell.

The carrying capacity Cais the limiting or maximum concentrate production rate per unit

of area of cell cross-section, usually expressed as concentrate solids rate (kg/min) per unit of

available cell cross-sectional area (m2). The carrying capacity is strongly influenced by the gas

flow rate and the size of the bubbles in the froth. The mass of the hydrophobic particles that can

be carried by the froth varies directly with the surface area. The other important factor is the size

of the particles, because when a layer of particles is adhering to a gas-liquid interface, the mass

of particles per unit of interfacial area varies directly as the mean particle size. The expected

carrying capacity of conventional cells is given by Espinosa-Gomez et al. (1991) in equation 3.6.

This equation is used in calculating for the bubble diameter d80.

Ca=d80p

where: d80 is the bubble diameter at which 80% by mass of the concentrate passes, expressed

in mm, p is the density of the particles (kg/m3) and is a parameter which is 0.05 for flotation

cells that are 1.0 m to 2.0 m in diameter.

The calculated bubble diameter d80 is divided by 0.80 to obtain the bubble diameter d

required for the flotation cell considered. It must be noted that although d80 is the bubble

diameter at which 80% by mass of the concentrate passes, it does not have a bearing on the

material balances. Equation 3.6 above is just a correlation from Espinosa-Gomez et al. which

was established at the said mass percentage of concentrate. With this, the bubble diameter d80

is then used in equation 3.7 to calculate for the superficial gas velocity Jg along with Sb. This

collection capability Sb is obtained by dividing the cross-sectional area of the cell with its

corresponding residence time in seconds.

Jg =Sb

d

where Sb(interfacial area/s) is thecollection capability d is the bubble diameter.

3.2.2 Sparging Hole Diameter

A sparger is necessary to disperse gas into the slurry to facilitate in the formation ofbubbles for the flotation process. The calculated superficial gas velocity requirement is used to

design the sparger for the flotation equipment. The relationship below was used in calculating

for the sparging hole diameter for a given degree of maldistribution.

= 0.95 ()1/2

(3.5)

(3.6)

(3.7)

(3.8)

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where: dP is the pipe diameter, dh is the sparging hole diameter, Nh is the number of holes in the

sparger, CV is the orifice coefficient for sparger hole, Uh is the average velocity through sparger

holes, Uh is the difference between maximum and minimum velocities through sparger holes

and Uh/ Uhaccounts for the fractional maldistribution of flow through sparger holes.

Implementing the calculation process presented in section 3.2, the superficial gas

velocities Jg and the sparging hole diameter for each of the five flotation cell is given in Table

3.2.2.1.

Table 3.2.2.1 Superficial Gas Velocity and Sparging Hole Diameter

Flotation Cell Superficial Gas Velocity, Jg(m/s)

Sparging Hole Diameter, dh(m)

1st Rougher 0.160 0.01042nd Rougher 0.352 0.00473rd Rougher 0.496 0.00341st Cleaner 0.125 0.01402nd Cleaner 0.119 0.0141

Average Volume Flotation Cell

With regards to the average volume flotation cell, although the actual cell volume and

the cross-sectional area A are the same for all the five flotation cell units, the superficial gas

velocity requirement Jg and the sparging hole diameter dh do not have the same value for each

of the flotation unit. This is because; the difference in the density of the particles p and the

mass flow rate that comes in to each flotation cell unit can influence the size of the bubbles.

This in turn affects Jg and dh. With this, the superficial gas velocities Jg and the sparging hole

diameter of the average volume flotation cell for each of the five flotation cell units is given in

Table 3.2.2.2.

Table 3.2.2.2 Superficial Gas Velocity and Sparging Hole Diameter (Average Volume Flotation Cell)

Flotation Cell Unit Superficial Gas Velocity, Jg(m/s)

Sparging Hole Diameter, dh(m)

1st Rougher 0.172 0.00942nd Rougher 0.342 0.00503rd Rougher 0.470 0.00361st Cleaner 0.115 0.01582nd Cleaner 0.133 0.0121

As a generalization for the sparger system, a smaller bubble diameter corresponds to a

smaller sparging hole diameter since superficial gas velocity which is inversely proportional to

the bubble diameter, is also inversely proportional to the sparging hole diameter.

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3.3 Agitation System

3.3.1 Agitator Dimensions

In the froth flotation process, the agitator provides enough turbulence in the pulp phase

to promote collision of particles and bubbles such that the valuable particles attach to the

bubbles for it to be transported into the froth phase for recovery. The agitator that will be used is

a flat-blade turbine impeller with six blades.

L

W

Da

E

A

A

H

Dp

Figure 3.3.1 Agitator Dimension Designations

The impeller diameter, Da is given by McCabe et al. (1993) to be one-thirds of the tank

diameter, Dt.

= 13Since the bottom of the tank is not circular, the tank diameter that will be used is the

hydraulic diameter. From Geankoplis (1993),

= 2 +

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= 222

=The length, L and width, W of the blades is given by McCabe et al(1993) to be one-

fourths and one-fifths of the tank diameter respectively, = 15 = 14Also, from McCabe et al. (1993), the distance of the impeller from the bottom of the tank,

E is one-thirds of the tank diameter,

=1

3

In addition, the diameter of the shaft which holds the impeller dP is 2/95 of the tank diameter Dt, = 295With regards to the average volume flotation cell, the dimensions of the agitator are the

same for each of the five flotation cell unit. With this, the dimensions of the agitator for the five

flotation cells along with the average volume flotation cell are summarized in Table 3.3.1.

Table 3.3.1 Flat-blade Turbine Impeller Dimensions and Shaft Diameter dP (based on Figure 3.3.1)

Flotation CellDimension (m)

Dt Da L W E dp

1st rougher 1.43 0.48 0.12 0.095 0.476 0.030

2nd rougher 1.46 0.49 0.12 0.098 0.488 0.031

3rd rougher 1.47 0.49 0.12 0.098 0.491 0.031

1st cleaner 1.49 0.50 0.12 0.099 0.495 0.031

2nd cleaner 1.41 0.47 0.12 0.094 0.471 0.030

Average Value 1.45 0.48 0.12 0.097 0.484 0.031

3.3.2 Power Requirement

The power requirement in a flotation cell is a function of the Reynolds number. The

power, P delivered to the slurry is given by equation 3.8.

= 35 (3.9)

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where: Np is the power number, n is the rotational speed (rev/s), Da is the impeller diameter (m),

and is the slurry density (kg/m3). The power number is related to the Reynolds number by the

plot in Figure 3.3.2

In Figure 3.2.2, for the dashed portion of curve D, the value of Np from the figure must be

multiplied by NFrm. The Froude number, NFr is given by equation 3.9.

= 2

The exponent m is empirically related to Reynolds number by equation 3.10.

= 10 where a and b are constants and are equal to 1 and 40 respectively, McCabe et al(1993). The

power number, Np is given by equation 3.11.

=

35

and Reynolds number is given by equation 3.12.

= 2 where: (Pa-s) is the viscosity of the slurry.

(3.10)

(3.11)

(3.12)

(3.13)

Figure 3.3.2 Power number, Np vs Reynolds number, NRe, (McCabe et al., 1993)

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The power requirement for the five flotation cells are summarized in Table 3.3.2.

Table 3.3.2 Power Requirement of the Five Flotation Cells

Flotation UnitNumber of Power per Total

Cells per Flotation Unit Flotation cell (W) Power requirement (W)1st rougher 3 4329.57 12988.70

2nd rougher 14 2531.64 35443.02

3rd rougher 1 2699.29 2699.29

1st cleaner 4 1176.74 4706.95

2nd cleaner 4 885.47 3541.89


Although the average volume flotation cell has the same impeller diameter Da, the power

requirement for the average flotation cell in each of the five flotation units differ. These

dissimilarities can be attributed to the difference in the rotational speed n, slurry density and

slurry viscosity for each of the five flotation cell unit. With this, the power requirement for the

average volume flotation cell in each of the five flotation units are summarized in Table 3.3.3.

Table 3.3.3 Power Requirement of the Five Flotation Cell Units (Average Volume Flotation Cell)

Flotation UnitNumber of Power per Total

Cells per Flotation Unit Flotation cell (W) Power requirement (W)

1st rougher 3 4878.83 14636.49

2nd rougher 14 2396.48 33550.743rd rougher 1 2445.25 2445.25

1st cleaner 4 1009.90 4039.61

2nd cleaner 4 1074.40 4297.61

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B

B

C

Section 4

Mechanical Design of Equipment

The equipment designed is a rectangular vertical tank with trapezoidal bottom, an air

pump and an agitator. Stainless steel (AISI 304) is the material of construction which was

selected due to its weldability and high corrosion resistance in handling reagents and feed

materials which has high water content. On the other hand, the equipment has four legs

supports made of the same material which are welded. The sections that follow illustrate in

detail the various aspects of the mechanical engineering design of the designed flotation cell.

4.1 Flotation Cell Dimensions

With the obtained volume requirement presented in Section 3, the dimensions of the

flotation cells in each of the flotation cell unit are then determined. The equations used in

determining these dimensions are presented next. Refer to Figure 4.1.1 below for the

designations of the flotation cell dimensions used in the said equations.

Figure 4.1.1 Flotation Cell Dimension Designations

B

A

C

H

B

A

h

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In determining the dimensions of the flotation cell, the volume requirement obtained in Section 3

is equated to the summation of the volume of each cell sections as shown in equation 4.1.

= 2 + 132 + + 2

The volumes of each cell section are given in equation 4.2 and 4.3 below.

= 132 + + 2 = 2

where: V is the total flotation cell volume, Vt is the volume of the truncated pyramid and Vr is the

volume of the rectangular prism

The dimensions of the flotation cell are related by the equations below.

= + = = 14 = 34Representing the right-hand side of equation 4.1 with a single variable A based on the

dimension equations presented above, the dimension A can be directly obtained and the

determination of the other dimension follows. This single-variable equation is given by equation

4.4 below.

V = 433 + 1

32 +4

3 + 4

32 4

9

A summary of the dimensions of the designed flotation cell for each of the five flotation

cell unit is given in Table 4.1.1 and 4.1.2 below. The calculations carried out are presented in

Appendix B.3.1 and C.1. On the other hand, refer to Appendix C.2 for the calculation of the

flotation cell thickness.

(4.1)

(4.2)

(4.3)

(4.3)

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Table 4.1.1 Flotation Cell Dimensions of the Five Flotation Cells

Dimension

Designation

Flotation Cell Unit Dimension

1st Rougher 2nd Rougher 3rd Rougher 1st Cleaner 2nd Cleaner

Rectangular Tank

B, Length (m)

B, Width (m)C, Height (m)

1.90

1.901.90

1.95

1.951.95

1.96

1.961.96

1.98

1.981.98

1.88

1.881.88

Trapezoidal Bottom

B, Length 1 (m)

A, Length 2 (m)

B, Width 1 (m)

A, Width 2 (m)

h, Height (m)

Thickness (mm)

H, Total Tank Height (m)

1.90

1.43

1.90

1.43

0.63

5.09

2.54

1.95

1.46

1.95

1.46

0.65

5.09

2.60

1.96

1.47

1.96

1.47

0.66

5.09

2.62

1.98

1.49

1.98

1.49

0.66

5.09

2.64

1.88

1.41

1.88

1.41

0.63

5.09

2.51


In the case of the average volume flotation cell (V = 9.1473 m 3), the dimensions are the

same for each of the five flotation cell units. These average dimensions are given in Table 4.1.2.

Table 4.1.2 Flotation Cell Dimensions of the Average Volume Flotation Cell

Dimension Designation Flotation Cell Dimension

Rectangular Tank B, Length (m)

B, Width (m)

C, Height (m)

1.941.94

1.94Trapezoidal Bottom B, Length 1 (m)

A, Length 2 (m)

B, Width 1 (m)

A, Width 2 (m)

h, Height (m)

1.941.451.941.450.65

Thickness (mm)

H, Total Tank Height (m)

5.092.58

Note: The dimensions for the average volume flotation cell are the values obtained after taking theaverage of the dimension presented in Table 4.1.1 for the five flotation cell units.

4.2 Supports

The five flotation cells are set on rectangular leg supports that are made of stainless

steel (AISI 304). The two legs are welded parallel to each other on the trapezoidal bottom of the

flotation cell. See Figure 4.1.1 for the form and exact placement of the rectangular legs in the

equipment. The dimensions of the rectangular leg supports and base plate for the five flotation

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cells are shown in Table 4.2.1 and Table 4.2.2 respectively. Refer to Appendix C.3 for the

details of the calculations made for the support dimensions.

Table 4.2.1 Dimensions of the Support

Flotation Cell AAS (m) AS (m) LS (m) a tS (mm) hS (m)1st Rougher2nd Rougher3rd rougher1st Cleaner2nd CleanerAverage b

5.57 x 10-3

5.71 x 10-3

5.83 x 10-3

5.29 x 10-3

4.30 x 10-3

5.34 x 10-3

1.39 x 10-3

1.43 x 10-3

1.46 x 10-3

1.32 x 10-3

1.07 x 10-3

1.33 x 10-3

0.2270.2320.2340.2360.2240.231

2.632.632.672.412.052.48

0.0450.0460.0470.0470.0450.046

Note:aLs is the length of the support corresponding to the length of the trapezoidal tank bottom; tS is the thickness of

the rectangular support and hS is the height of the support.b

The dimensions of the supports for the average volume flotation cell are the values obtained after

taking the average of the support dimensions for the five flotation cell units.

Table 4.2.2 Dimensions of the Base Plate

Flotation Cell LB (m)a WB (m) tB (mm)

1st Rougher2nd Rougher3rd rougher1st Cleaner2nd CleanerAverage*

0.249370.255710.257330.259310.246750.25369

0.022670.0232460.0233940.0235740.0224320.02306

2.63062.63112.67002.40592.0523

2.47798Note:

aLB is the length of the support corresponding to the length of the trapezoidal tank bottom; tB is the thickness of

the base plate and hS is the height of the base plate.bThe dimensions of the base plate for the average volume flotation cell are the values obtained after

taking the average of the base plate dimensions for the five flotation cell units.

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4.3 Materials of Construction

In the construction of the flotation cell, the following characteristics were considered in

the choice of the construction material: (a) ease of fabrication, (b) ease of cleaning, (c) high

resistance to corrosion, (d) weldability, (e) ductility, and (f) availability. Table 4.3.1 shows the

various materials of construction options for the design project along with their description,

advantages and disadvantages which served as the basis for the selection process.

Table 4.3.1 Comparison of Selected Construction Materials

Material Description Advantages Disadvantages

Carbon Steel makes up 90% of allsteels; contain varyingamounts of carbon and notmore than 1.65 %manganese, 0.60 %silicon, and 0.60 % copper

has the ability to become harderand stronger through heattreating; cheaper compared toother types of steel

the higher carboncontent lowers themelting point andweldability; is lessductile and becomesmalleable whenheated

High-Strength

Low Alloy

Steels

steel containing smallamounts of niobium orvanadium that have acarbon content between0.05 0.25% to retainformability and weldability

cost less than the regular alloysteels; lighter than a carbonsteel with the same strength;more resistant to rust than mostcarbon steels

Expensive comparedto other types of steels

Stainless Steel Contain chromium, nickel,and other alloyingelements

bright and rust resistant in spiteof moisture or the action ofcorrosive acids and gases; highstrength; retain that strength for

long periods at extremely highand low temperatures; canwithstand the action of bodyfluids; can be easily cleaned; lowmaintenance

Expensive comparedto other types of steels

With the criteria kept in mind and based on Table 4.3.1, stainless steel AISI 304 has

been chosen as the major construction material in the design of the flotation cell equipment.

Stainless steel (AISI 304)

Stainless steels are steels possessing high corrosion resistance due to the presence of

substantial amount of chromium. Chromium forms a thin film of chromium oxide on the steel

surface. This film protects the steel from further oxidation, making it stainless. With this,

stainless steels can also be used in severe environments because they are able to resist

oxidation while maintaining their properties (Callister, 2004). The crystallographic structure of

304 stainless steel is austenitic with FCC crystal lattice making it weldable, ductile and highly

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resistant to corrosion. Moreover, this type of stainless steel retains their properties at elevated

temperatures. Although stainless steels are slightly more expensive than other materials, AISI

304 stainless steel is still the least expensive among the other type of stainless steels. Some

properties of AISI 304 stainless steel are given in Table 4.3.2.

Table 4.3.2 Properties of 304 Stainless Steel (AISI 304)

Chemical composition: C=0.08%max, Mn=2%max, Cr=19%, Ni=9.5%

Property Value in metric unit

Density 7.9 x10 kg/m

Modulus of elasticity 193 GPa

Thermal expansion (20 C) 17.2x10-6 C

Specific heat capacity 502 J/(kg.K)

Thermal conductivity 16.2 W/(m.K)

Electric resistivity 7.2x10-7

Ohm.mTensile strength (annealed) 586 MPa

Yield strength (annealed) 241 MPa

Elongation (annealed) 55 %

Hardness (annealed) 80 RB

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4.4 Specifications Summary and Schematic Diagram

A summary of the specifications for each of the five flotation cells is presented in Table

4.4.1 to Table 4.4.5. The schematic diagram for each of the flotation cells with the dimensions is

shown in Figure 4.4.1 to Figure 4.4.5.

Table 4.4.1 First Rougher Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: First Rougher Flotation Cell UnitGeneral Information

FunctionNumber of Flotation Cells% Copper RecoveryWorking Cell Volume (m3)Actual Cell Volume (m3)Gas Velocity Requirement (m/s)Sparging Hole Diameter (cm)

froth flotation of Cu from CuFeS2 ores391.617.238.680.1601.038

Flotation Cell Dimensions Agitator InformationRectangular Tank

Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)

Height of Support (m)

Total Tank Height (m)

1.90

1.90

1.90

1.90

1.43

1.90

1.43

0.64

5.09

0.045

2.54

Type

Number of Blades

Agitator Speed (rpm)

Power Requirement per

Flotation Cell (W)

Total Power Requirement (W)

Dimensions

Shaft Diameter (m)

Impeller diameter (m)

Blade length (m)

Blade width (m)

Impeller distance from

the tank bottom (m)

Flat-blade turbine impeller

6

250

4329.57

12988.70

0.031

0.48

0.12

0.095

0.476

Process ConditionsStream Details Feed Product - Froth Product -Tailings

Temperature (C)

Pressure (kPa)

Pulp Density (kg/m3)

Mass flow rate (kg/min)

pH

Compositionwt% Copper

wt% Iron

wt% Impurities

wt% Process water

30C - 40C

101.325

1561.94

1129.48

8.5 9.5

6.41

23.36

15.29

55.0

30C - 40C

101.325

1561.94

401.21

8.5 9.5

17.90

11.50

16.00

54.60

30C - 40C

101.325

1561.94

728.26

8.5 9.5

0.80

38.90

5.10

55.20

Material of Construction: Stainless Steel (AISI 304)

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1.9143 m

1.9041 m

2.5

388m

2.5

490m

42.4

2cm

23.6

2cm

63.4

7cm

2.5

mm

2.5

mm

30 mm

11.9 cm

9.5

2cm

35.43 cm

47.6 cm

47.6

cm

1.4383 m

1.4281 m

2.6

306.m

m

45.3

4mm

24.94 cm

22.67 mm

24.9

4cm

22.67

mm

47.6

cm

1.9

041m

22.67 cm

2.6

306mm

10.38 mm

Figure 4.4.1 First Rougher Flotation Cell Dimensions and Arrangement

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Table 4.4.2 Second Rougher Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: Second Rougher Flotation Cell UnitGeneral Information

FunctionNumber of Flotation Cells

% Copper RecoveryWorking Cell Volume (m3)Actual Cell Volume (m3)Gas Velocity Requirement (m/s)Sparging Hole Diameter (cm)

froth flotation of Cu from CuFeS2 ores14

92.367.809.360.3520.475


Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)



1.95

1.95

1.95

1.95

1.46

1.95

1.46

0.65

5.09

0.046

2.60

Type

Number of Blades



Flotation Cell (W)


Dimensions

Shaft Diameter (m)


Blade length (m)

Blade width (m)


the tank bottom (m)


6

200

2531.64

35443.02

0.031

0.49

0.12

0.097

0.49


Temperature (C)

Pressure (kPa)Pulp Density (kg/m3)


pH

Composition

wt% Copper

wt% Iron

wt% Impurities

wt% Process water

30C - 40C

101.3251484.54

1157.51

8.5 9.5

2.02

35.20

4.78

58.0

30C - 40C

101.3251484.54

988.59

8.5 9.5

2.70

19.60

3.20

74.50

30C - 40C

101.3251484.54

168.92

8.5 9.5

0.50

40.40

10.78

48.32


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1.9627 m

1.9525 m

2.6

034

2.6

136m

65.0

8cm

2.5

6mm

2.5

6mm

30.76 mm

12.20 cm

9.7

6cm

35.4 cm

47.6 cm

48.8

1cm

1.4746 m

1.4644 m

2.6

311mm

46.4

9mm

25.57 cm

23.25 mm

25.5

7cm

23.2

5mm

48.8

1cm

1.9

525m

23.25 cm

2.6

311mm

42.4

2cm

21.3

6cm

4.75 mm

Figure 4.4.2 Second Rougher Flotation Cell Dimensions and Arrangement

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Table 4.4.3 Third Rougher Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: Third Rougher Flotation Cell UnitGeneral Information




83.027.959.540.4963.373


Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)



1.96

1.96

1.96

1.96

1.47

1.96

1.47

0.66

5.09

0.047

2.620

Type

Number of Blades



Flotation Cell (W)


Dimensions

Shaft Diameter (m)


Blade length (m)

Blade width (m)


the tank bottom (m)


6

200

2699.29

2699.29

0.0310

0.49

0.12

0.098

0.491


Temperature (C)



pH

Composition

wt% Copper

wt% Iron

wt% Impurities

wt% Process water

30C - 40C

101.3251487.95672364.81488.5 9.5

0.5040.4010.7848.32

30C - 40C

101.3251487.9567133.86118.5 9.5

1.5031.2520.7546.50

30C - 40C

101.3251487.95672231.0185198.5 9.5

0.4440.9310.2348.40


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1.9751 m

1.9649 m

2.6

199

m

2.6

301

m

65.5

cm

2.5

8mm

2.5

8mm

30.96 mm

12.28 cm

9.8

2cm

36.84 cm

49.12 cm

47.6

cm

1.4839 m

1.4737 m

2.6

7mm

46.7

9mm

25.73 cm

23.39 mm

25.7

3cm

23.3

9mm

49.1

2cm

1.9

649m

23.39 cm

2.6

7mm

21.3

6cm

27.8

8cm

13.37 mm

Figure 4.4.3 Third Rougher Flotation Cell Dimensions and Arrangement

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Table 4.4.4 First Cleaner Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: First Cleaner Flotation Cell UnitGeneral Information




90.818.139.760.1251.404


Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)



1.98

1.98

1.98

1.98

1.49

1.98

1.49

0.66

5.092

0.0472

2.64

Type

Number of Blades



Flotation Cell (W)


Dimensions

Shaft Diameter (m)


Blade length (m)

Blade width (m)


the tank bottom (m)


6

150

1176.74

4706.95

0.0312

0.495

0.123

0.0990

0.4950


Temperature (C)


Mass flow rate (tons/year)

pH

Composition

wt% Copper

wt% Iron

wt% Impurities

wt% Process water

30C - 40C

101.3251315.46

1069.83

8.5 9.5

8.30

31.23

6.57

53.90

30C - 40C

101.3251315.46

289.35

8.5 9.5

31.50

6.43

4.07

58.30

30C - 40C

101.3251315.46

780.44

8.5 9.5

3.40

32.80

3.30

60.50


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1.9903 m

1.9801 m

2.6

402m

2.6

504m

66.0

cm

2.6

mm

2.6

mm

31.20 mm

12.38 cm

9.9

cm

37.12 cm

49.5 cm

49.5

cm

1.4953 m

1.4851 m

2.4

059mm

47.1

5mm

25.93cm

23.57 mm

25.9

3cm

23.5

7mm

49.5

cm

1.9

801m

23.57 cm

2.4

059mm

27.8

8cm

42.4

2cm

14.04 mm

Figure 4.4.4 First Cleaner Flotation Cell Dimensions and Arrangement

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Table 4.4.5 Second Cleaner Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: Second Cleaner Flotation Cell UnitGeneral Information


% Copper RecoveryWorking Cell Volume (m3)Actual Cell Volume (m3)Gas Velocity Requirement (m/s)Sparging Hole Diameter


63.817.00648.40760.11901.4086


Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)



1.88

1.88

1.88

1.88

1.41

1.88

1.41

0.628

5.090

0.0449

2.5

Type

Number of Blades



Flotation Cell (W)


Dimensions

Shaft Diameter (m)


Blade length (m)

Blade width (m)


the tank bottom (m)


6

150

885.47

3541.89

0.0297

0.47

0.12

0.0942

0.47


Temperature (C)


Mass flow rate (tons/year)

pH

Composition

wt% Copper

wt% Iron

wt% Impurities

wt% Process water

30C - 40C

101.3251234.623460.078.5 9.5

2.7019.603.2074.50

30C - 40C

101.3251234.62768.928.5 9.5

8.3031.256.5753.90

30C - 40C

101.3251234.622691.158.5 9.5

1.1016.315.4977.10


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1.8943 m

1.8841 m

2.5122m

2.5224m

62.8cm

2.47mm

2.47mm

29.69 mm

11.78 cm

9.42cm

35.32 cm

47.1 cm

47.1cm

1.4233 m

1.4131 m

2.0523mm

44.86mm

24.68 cm

22.43 mm

24.68cm

22.43mm

47.1cm

1.8841m

22.43 cm

2.0523mm

42.42cm

42.42cm

14.09 mm

Figure 4.4.5 Second Cleaner Flotation Cell Dimensions and Arrangement

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It must be noted that for this average volume flotation cell, only the agitator, tank and

support type and dimensions are common for each of the five flotation cell units. The superficial

gas velocity requirement, sparging hole diameter and power requirement differ for each flotation

cell unit (refer to Section 4 - Table 3.2.2.2 and Table 3.3.2). Moreover, for this average volume

flotation cell; the material of construction, agitator speed, process conditions, % copper recovery

and number of cells are similar to that presented in the specifications summary of the five

flotation cell units in Table 4.4.1 to Table 4.4.5. With this, a modified format of the specifications

summary for the average volume flotation cell is presented in Table 4.4.6. The schematic

diagram of this flotation cell with the dimensions is shown in Figure 4.4.6.

Table 4.4.6 Average Volume Flotation Cell Specification Summary

EQUIPMENT DESCRIPTION: Average Volume Flotation CellGeneral Information

FunctionWorking Cell Volume (m3)Actual Cell Volume (m3)Gas Velocity Requirement (m/s)Sparging Hole Diameter (cm)

froth flotation of Cu from CuFeS2 ores7.62289.1473(refer to Table 3.2.2.2)(refer to Table 3.2.2.2)


Length (m)

Width (m)

Height (m)

Trapezoidal Bottom

Length 1 (m)

Length 2 (m)

Width 1 (m)

Width 2 (m)

Height (m)

Thickness (mm)



1.88

1.88

1.88

1.88

1.41

1.88

1.41

0.628

5.090

0.045

2.51

Type

Number of Blades


Flotation Cell (W)


Dimensions

Shaft Diameter (m)


Blade length (m)

Blade width (m)


the tank bottom (m)


6

(refer to Table 3.3.2)

(refer to Table 3.3.2)

0.031

0.484

0.121

0.097

0.484

Process Conditions

Stream Details Feed Product - Froth Product -TailingsTemperature (C)

Pressure (kPa)

pH

30C - 40C101.3258.5 9.5

30C - 40C101.3258.5 9.5

30C - 40C101.3258.5 9.5


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1.9143 m

1.9041 m

2.5

388m

2.5

490m

42.4

2cm

23.6

2cm

63.4

7cm

2.5

mm

2.5

mm

30 mm

11.9 cm

9.5

2cm

35.43 cm

47.6 cm

47.6

cm

1.4383 m

1.4281 m

2.6

306.m

m

45.3

4mm

24.94 cm

22.67 mm

24.9

4cm

22.6

7mm

47.6

cm

1.9

041m

22.67 cm

2.6

306mm

Dh

Figure 4.4.6 Average Volume Flotation Cell Dimensions

Note: The sparging hole diameter dh in the figure above differs for the five flotation cell units. Refer toTable 3.2.2.2 for the values of the sparging hole diameters for each flotation cell unit.

Flow of Streams

The actual flow of the incoming and outgoing slurry streams with reference to the design and

the arrangement of the inlet and outlet ports of the flotation cell units is given Figure

Final Design (10!18!10)

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