EXTRACTION EXTRACTION and and

SUGAR INDUSTRY SUGAR INDUSTRY APPLICATIONSAPPLICATIONS

EXTRACTIONEXTRACTION

1-LEACHING(SOLID EXTRACTION)1-LEACHING(SOLID EXTRACTION)

a) GENERAL INFORMATIONa) GENERAL INFORMATION

b) b) FACTORS INFLUENCING THE RATE OFFACTORS INFLUENCING THE RATE OF EXTRACTIONEXTRACTION

c) c) LEACHİNG EQUİPMENTLEACHİNG EQUİPMENT 2- LIQUID-LIQUID EXTRACTION 2- LIQUID-LIQUID EXTRACTION

a) EXTRACTION PROCESS a) EXTRACTION PROCESS

b) CLASSIFICATION OF EXTRACTION EQUIPMENT b) CLASSIFICATION OF EXTRACTION EQUIPMENT

- STAGE-WISE EQUIPMENT FOR EXTRACTION - STAGE-WISE EQUIPMENT FOR EXTRACTION

- DIFFERENTIAL CONTACT EQUIPMENT FOR EXTRACTION- DIFFERENTIAL CONTACT EQUIPMENT FOR EXTRACTION

EXTRACTION IN SUGAR INDUSTRY APPLICATIONSEXTRACTION IN SUGAR INDUSTRY APPLICATIONS 1- 1- THE FİXED-BED OR ROBERT DİFFUSİON BATTERYTHE FİXED-BED OR ROBERT DİFFUSİON BATTERY

2- 2- CONTİNUOUS DİFFUSİON BATTERİESCONTİNUOUS DİFFUSİON BATTERİES

EXTRACTIONEXTRACTION

Extraction is the method of removing one constituent from a Extraction is the method of removing one constituent from a solid or liquid by means of a liquid solvent.Extraction techniques solid or liquid by means of a liquid solvent.Extraction techniques fall into two categories.The first is called leaching or solid fall into two categories.The first is called leaching or solid extraction and the is second called liquid extraction.extraction and the is second called liquid extraction.

LEACHING (SOLID LEACHING (SOLID EXTRACTION)EXTRACTION)

A-GENERAL INFORMATIONA-GENERAL INFORMATION

Leaching is concerned with the extraction of soluble constituent Leaching is concerned with the extraction of soluble constituent from a solid by means of a solvent.The process may be used from a solid by means of a solvent.The process may be used either for the production of a concentrated solution of a valuable either for the production of a concentrated solution of a valuable solid material,or in order to remove an insoluble solid ,such as a solid material,or in order to remove an insoluble solid ,such as a

pigment ,from a soluble material with which it is contaminated.pigment ,from a soluble material with which it is contaminated.

B-FACTORS INFLUENCING THE B-FACTORS INFLUENCING THE RATE OF EXTRACTIONRATE OF EXTRACTION

The selection of the equipment for an extraction process is The selection of the equipment for an extraction process is influenced by the factors which are responsible for limiting the influenced by the factors which are responsible for limiting the extraction rate.There are four important factors to be considered:extraction rate.There are four important factors to be considered:

Particle size:Particle size: The smaller the size ,the greater is the interfacial The smaller the size ,the greater is the interfacial

area between the solid and liquid,and therefore the higher is the area between the solid and liquid,and therefore the higher is the rate of transfer of material and the smaller is the distance the rate of transfer of material and the smaller is the distance the solute must diffuse within the solid. solute must diffuse within the solid.

Solvent:Solvent:The liquid chosen should be a good selective solvent and The liquid chosen should be a good selective solvent and its viscosity should be sufficiently low for it to circulate freely.its viscosity should be sufficiently low for it to circulate freely.

Temperature:Temperature:In most cases,the solubility of the material which is In most cases,the solubility of the material which is being extracted will increase with temperature to give a higher being extracted will increase with temperature to give a higher rate of extraction.Further ,the diffusion coefficient will be expected rate of extraction.Further ,the diffusion coefficient will be expected to increase with rise in temperature and this will also improve the to increase with rise in temperature and this will also improve the rate of extraction.rate of extraction.

Agitation of the fluid:Agitation of the fluid:Agitation of the solvent is important Agitation of the solvent is important because this increases the eddy diffusion and therefore the because this increases the eddy diffusion and therefore the transfer of material from the surface of particles to tha bulk of the transfer of material from the surface of particles to tha bulk of the solution.solution.

LEACHİNG EQUİPMENTLEACHİNG EQUİPMENT

When the solids form an open ,permeable mass When the solids form an open ,permeable mass throughout the leaching operation ,solvent may be throughout the leaching operation ,solvent may be percolated through an unagitated bed of solids.With percolated through an unagitated bed of solids.With impermeable solids or materials that dissintegrate during impermeable solids or materials that dissintegrate during leaching,the solids are dispersed into the solvent and are leaching,the solids are dispersed into the solvent and are later separated from it.Both methods may be either batch later separated from it.Both methods may be either batch or continuous.or continuous.

In some cases the rate of the solution is so rapid that one In some cases the rate of the solution is so rapid that one passage of solvent through the material is sufficient ,but passage of solvent through the material is sufficient ,but countercurrent flow of solvent through a battery of tanks is more countercurrent flow of solvent through a battery of tanks is more common.In this method, fresh solvent is fed to the tank containing common.In this method, fresh solvent is fed to the tank containing the solid that is most nearly extracted;it flows through the several the solid that is most nearly extracted;it flows through the several tanks in series and is finally withdrawn from the tank that has tanks in series and is finally withdrawn from the tank that has been freshly charged.such a series of tanks is called an extraction been freshly charged.such a series of tanks is called an extraction battery.battery.

Leaching by percolation through stationary solid bedsLeaching by percolation through stationary solid beds Stationary solid-bed leaching is done in a tank with a Stationary solid-bed leaching is done in a tank with a perforated false bottom to support the solids and permit perforated false bottom to support the solids and permit drainage of the solvent.Solids are loaded into the drainage of the solvent.Solids are loaded into the tank,sprayed with solvent until their solute content is tank,sprayed with solvent until their solute content is reduced to the economical minimum,and excavatedreduced to the economical minimum,and excavated..

Moving-bed leachingMoving-bed leaching

In the machines that are used for this type of leaching, In the machines that are used for this type of leaching, the solids are moved through the solvent with little or no the solids are moved through the solvent with little or no agitation.The bollman extractor (figure a) contains a agitation.The bollman extractor (figure a) contains a bucket elevator in a closed casing.There are perforations bucket elevator in a closed casing.There are perforations in the bottom of each bucket.At the top right-hand in the bottom of each bucket.At the top right-hand corner of the machine ,the buckets are loaded with corner of the machine ,the buckets are loaded with flaky solids such as soybeans and are sprayed with flaky solids such as soybeans and are sprayed with appropriate amounts of half miscella as they travel appropriate amounts of half miscella as they travel downward.Half miscella is the intermediate solvent downward.Half miscella is the intermediate solvent containing some extracted oil and some small solid containing some extracted oil and some small solid particles.As solids and solvent flow cocurrently down the particles.As solids and solvent flow cocurrently down the right-hand side of the machine ,the solvent extracts right-hand side of the machine ,the solvent extracts

more oil from beans.more oil from beans.

Simultaneously the fine solids are filtered Simultaneously the fine solids are filtered out of the solvent, so thaout of the solvent, so thatt clean full clean full miscella can be pumped from the right –miscella can be pumped from the right –hand sump at the bottom of the hand sump at the bottom of the casing.As the partially extracted beans casing.As the partially extracted beans rise through the left side of the rise through the left side of the machine ,a stream of pure solvent machine ,a stream of pure solvent percolates countercurrently through percolates countercurrently through them.It collects in the left-hand sump them.It collects in the left-hand sump and is pumped to the half-miscella and is pumped to the half-miscella storage tank.Fully extracted beans are storage tank.Fully extracted beans are dumped from the buckets at the top of dumped from the buckets at the top of the elevator into a hopper from which the elevator into a hopper from which they are removed by paddle conveyors.they are removed by paddle conveyors.

Bollman extractor

In the Rotocel extractor,illusrated In the Rotocel extractor,illusrated in figure b, a horizontal basket is in figure b, a horizontal basket is divided into walled compartments divided into walled compartments with a floor that is permeable to the with a floor that is permeable to the liquid.The basket rotates slowly liquid.The basket rotates slowly about a vertical axis.Solids are about a vertical axis.Solids are admitted to each compartment at admitted to each compartment at the feed point;the compartments the feed point;the compartments then successively pass a number of then successively pass a number of solvent sprays, a drainage section, solvent sprays, a drainage section, and a discharge point at which the and a discharge point at which the floor of the compartment opens to floor of the compartment opens to discharge the extracted solids.The discharge the extracted solids.The empty compartment moves to the empty compartment moves to the feed to point to receive its next load feed to point to receive its next load of solids.To give countercurrent of solids.To give countercurrent extraction, fresh solvent is fed only extraction, fresh solvent is fed only to the last compartment before the to the last compartment before the discharge point, and the solids in discharge point, and the solids in each preceeding compartment are each preceeding compartment are washed with the effluent from the washed with the effluent from the succeeding one.succeeding one.

Rotocel extractor

Dispersed –solid leachingDispersed –solid leaching

Solids that form impermeable beds, either before or during Solids that form impermeable beds, either before or during leaching , are treated by dispersing them in the solvent by leaching , are treated by dispersing them in the solvent by mechanical agitation in a tank or flow mixer.The leached residue mechanical agitation in a tank or flow mixer.The leached residue is then separate from the strong solution by settling or filtration. is then separate from the strong solution by settling or filtration. Small quantities can be leached batchwise in this way in an Small quantities can be leached batchwise in this way in an agitated vessel with a bottom drawoff for settled residue.agitated vessel with a bottom drawoff for settled residue.

LIQUID-LIQUID EXTRACTIONLIQUID-LIQUID EXTRACTION

The separation of the components of a liquid mixture by The separation of the components of a liquid mixture by treatment with a solvent in which one or more of the desired treatment with a solvent in which one or more of the desired components is preferentially soluble is known as liquid-liquid components is preferentially soluble is known as liquid-liquid extractextractionion. In this operation, it is essential that the liquid-mixture . In this operation, it is essential that the liquid-mixture feed and solvent are at least partially if not completely immiscible feed and solvent are at least partially if not completely immiscible and, in essence, three stages are involved:and, in essence, three stages are involved:

1-Bringing the feed mixture and the solvent into intimate 1-Bringing the feed mixture and the solvent into intimate

contact,contact, 2-Seperation of the resulting two phases,2-Seperation of the resulting two phases, 3-Removal and recovery of the solvent from each phase.3-Removal and recovery of the solvent from each phase.

It is possible to combine stages 1 and 2 into a single piece It is possible to combine stages 1 and 2 into a single piece of equipment such as a column which is then operated of equipment such as a column which is then operated continuously. Such an operation is known as differential continuously. Such an operation is known as differential contacting. Liquid-liquid extraction is also carried out in contacting. Liquid-liquid extraction is also carried out in stagewise equipment, the prime example being a mixer-stagewise equipment, the prime example being a mixer-settler unit in which the main features are the mixing of the settler unit in which the main features are the mixing of the two liquid phases by agitation, following by settling in a two liquid phases by agitation, following by settling in a separate vessel by gravity.separate vessel by gravity.

Important applications of liquid-liquid extraction Important applications of liquid-liquid extraction include the separation of aromatics from kerosene-based include the separation of aromatics from kerosene-based fuel oils to improve their burning qualities and the fuel oils to improve their burning qualities and the separation of aromatics from paraffin and naphthenic separation of aromatics from paraffin and naphthenic compounds to improve the temperature-viscosity compounds to improve the temperature-viscosity characteristics of lubricating oils. It may also be used to characteristics of lubricating oils. It may also be used to obtain, for example, relatively pure compounds such as obtain, for example, relatively pure compounds such as benzene, toluene, and xylene from catalytically produced benzene, toluene, and xylene from catalytically produced reformates in the oil industry, in the production of reformates in the oil industry, in the production of anhydrous acetic acid in the extraction of phenol from coal anhydrous acetic acid in the extraction of phenol from coal tar liquors, and in the metallurgical and biotechnology tar liquors, and in the metallurgical and biotechnology industries.industries.

EXTRACTION PROCESSEXTRACTION PROCESSESES All liquid-liquid extraction operations, may be carried out either All liquid-liquid extraction operations, may be carried out either

as a batch or continuous process.as a batch or continuous process.

In the single-stage batch process illustrated in In the single-stage batch process illustrated in thethe figure, the figure, the solvent and solution are mixed together and then allowed to solvent and solution are mixed together and then allowed to separate into the two phases-the extract E containing the required separate into the two phases-the extract E containing the required solute in the added solvent and the raffinate R, the weaker solution solute in the added solvent and the raffinate R, the weaker solution with some associated solvent. With this simplewith some associated solvent. With this simple arrangement mixing arrangement mixing and seperation occur in the same vessel.and seperation occur in the same vessel.

Fig.single-stage batch extraction

A continuous two-stage operation is shown in figure, where the A continuous two-stage operation is shown in figure, where the mixers and separators are shown as separate vessels. mixers and separators are shown as separate vessels.

Fig.Multiple-contact system with fresh solvent

CLASSIFICATION OF CLASSIFICATION OF EXTRACTION EQUIPMENTEXTRACTION EQUIPMENT

Essentially there are two types of design by which effective Essentially there are two types of design by which effective multistage operation may be obtained:multistage operation may be obtained:

1-Stage-wise contactors, in which equipment includes a series of 1-Stage-wise contactors, in which equipment includes a series of physical stages physical stages iin which the phasen which the phasess are mixed and separated, are mixed and separated, and;and;

2-2-DDifferential contactors, in which the phase are continuously ifferential contactors, in which the phase are continuously brought into contact with complete phase separation only at the brought into contact with complete phase separation only at the exits from the unit. exits from the unit.

STAGE-WISE EQUIPMENT FOR STAGE-WISE EQUIPMENT FOR EXTRACTIONEXTRACTION

The mixer settlerThe mixer settler

In the mixer-settler, the solution and solvent are mixed by some In the mixer-settler, the solution and solvent are mixed by some form of agitator in the mixer, and then transferred to the settler form of agitator in the mixer, and then transferred to the settler where the two phases separate to give an extract and a where the two phases separate to give an extract and a raffinate. In the settler the separation is often gravity-controlled, raffinate. In the settler the separation is often gravity-controlled, and the liquid densities and the form of the dispersion are and the liquid densities and the form of the dispersion are important parameters. important parameters.

Combined mixer-settler unitsCombined mixer-settler units

Recent work has emphasised the Recent work has emphasised the need to consider the combined mixer-need to consider the combined mixer-settler operationsettler operation..Thus WARWICK and Thus WARWICK and SCUFFHAM give details of a design, SCUFFHAM give details of a design, shown in shown in thethe figure in which the two figure in which the two operations are effected in the one operations are effected in the one combined unit. The impeller has swept-combined unit. The impeller has swept-back vanes with double shrouds, and back vanes with double shrouds, and the two phases meet in the draught the two phases meet in the draught tube. A baffle on the top of the agitator tube. A baffle on the top of the agitator reduces air intake and a baffle on the reduces air intake and a baffle on the inlet to the settler is important in inlet to the settler is important in controlling the flow pattern.controlling the flow pattern.This This arrangement gives a good performance arrangement gives a good performance and is mechanically neat.and is mechanically neat. Figure.Mixer-settler

The segmented mixer-The segmented mixer-

settler.settler.In segmented mixer-In segmented mixer-settlersettler specially designed specially designed KnitMesh pads are used to KnitMesh pads are used to speed up the rate of speed up the rate of coalescence. The centrally coalescence. The centrally situated mixer is designed to situated mixer is designed to give the required hold up, give the required hold up, and the mixer is pumped at and the mixer is pumped at the required rate to the the required rate to the settler which is formed in settler which is formed in segments around the mixer, segments around the mixer, each fed by individual each fed by individual pipework.pipework.

Figure.Segmented mixer-settler

Kuhni have recently Kuhni have recently developed a mixer-developed a mixer-settler column settler column whichwhich is is a series of mixer-a series of mixer-settlers in the form of a settlers in the form of a column. The unit column. The unit consists of a number of consists of a number of stages installed one on stages installed one on the top of another, the top of another, each hydraulically each hydraulically separated, and each separated, and each with a mixing and with a mixing and settling zone as shown settling zone as shown in in the the figure. figure. Fig.Kühni mixer-settles column

Baffle-plate columnsBaffle-plate columns

These are simple cylindrical columns provided with baffles to direct These are simple cylindrical columns provided with baffles to direct the flow of the dispersed phase, as shown in the flow of the dispersed phase, as shown in the the figure. The figure. The efficiency of each plate is very low, though since the baffles can efficiency of each plate is very low, though since the baffles can be positioned very close together at 75-150 mm, it is possible to be positioned very close together at 75-150 mm, it is possible to obtain several theoretical stages in a reasonable height. obtain several theoretical stages in a reasonable height.

Figure.Baffle-plate column

The Scheibel column The Scheibel column

One of the problems with perforated plate and indeed packed One of the problems with perforated plate and indeed packed columns is that redispersion of the liquids after each stage is very columns is that redispersion of the liquids after each stage is very poor. To overcome this, SCHEIBEL and KARR introduced a unit, poor. To overcome this, SCHEIBEL and KARR introduced a unit, shown in shown in thethe figure, in which a series of agitators is mounted on a figure, in which a series of agitators is mounted on a central rotating shaft. Between the agitators is fitted a wire mesh central rotating shaft. Between the agitators is fitted a wire mesh section which successfully breaks up any emulsions.section which successfully breaks up any emulsions.

Figure.Scheibel column

DIFFERENTIAL CONTACT EQUIPMENT FOR DIFFERENTIAL CONTACT EQUIPMENT FOR EXTRACTION EXTRACTION

Spray columnsSpray columns

Two methods of operating spray columns are shown in next Two methods of operating spray columns are shown in next figure. Either the light or heavy phase may be dispersed. In the figure. Either the light or heavy phase may be dispersed. In the former case (a) the light phase enters from a distributor at the former case (a) the light phase enters from a distributor at the bottom of the column and the droplets rise through the heavier bottom of the column and the droplets rise through the heavier phase, finally coalescing to form a liquid-liquid interface at the phase, finally coalescing to form a liquid-liquid interface at the top of the tower. Alternatively the heavier phase may be top of the tower. Alternatively the heavier phase may be dispersed, in which case interface is held at the bottom of the dispersed, in which case interface is held at the bottom of the tower as shown in (b). Although spray towers are simple in tower as shown in (b). Although spray towers are simple in construction, they are inefficient because considerable construction, they are inefficient because considerable recirculation of the continuous phase takes place. As a result recirculation of the continuous phase takes place. As a result true countercurrent flow is not maintained and up to 6 m may true countercurrent flow is not maintained and up to 6 m may be required for the height of one theoretical stage. be required for the height of one theoretical stage.

Figure.Spray towers

Packed columnsPacked columns

The packing increasing the interfacial area, and considerably The packing increasing the interfacial area, and considerably increases mass transfer rates compared with those obtained increases mass transfer rates compared with those obtained with spray columns because of the continuous coalescence and with spray columns because of the continuous coalescence and break-up of the drops. Packed columns are unsuitable for use break-up of the drops. Packed columns are unsuitable for use with dirty liquids, suspensions, or high viscosity liquids. They with dirty liquids, suspensions, or high viscosity liquids. They have proved to be satisfactory in the petroleum industhave proved to be satisfactory in the petroleum industry.ry.

Rotary annular columns and Rotary annular columns and

rotary disc-columnsrotary disc-columns

With these columns With these columns mechanical energy is provided mechanical energy is provided to form the dispersed phase. to form the dispersed phase. The equipment is particularly The equipment is particularly suitable for installations where suitable for installations where a moderate number of stages a moderate number of stages is required, and where the is required, and where the throughput is considerable. A throughput is considerable. A well dispersed system is well dispersed system is obtained with this obtained with this arrangement. arrangement. The fThe figure igure shows a rotary annular column.shows a rotary annular column.

Figure.Rotary annular column

Pulsed columnsPulsed columns

In order to prevent coalescence of the dispersed drops, In order to prevent coalescence of the dispersed drops, VAN DUCK and others have devised methods of providing VAN DUCK and others have devised methods of providing the whole of the continuous phase with a pulsed motion. the whole of the continuous phase with a pulsed motion. This may be done, either by some mechanical device, or by This may be done, either by some mechanical device, or by the introduction of compressed air.the introduction of compressed air.

The pulsation markedly improves performance of packed The pulsation markedly improves performance of packed columns. There are advantages in using gauze-type columns. There are advantages in using gauze-type packings since the pulsation operation often breaks ceramic packings since the pulsation operation often breaks ceramic rings.Pulsed packed columns have been used in the nuclear rings.Pulsed packed columns have been used in the nuclear industryindustry..

Centrifugal extractionCentrifugal extraction

If separation is difficult in a mixer-settler unit, a centrifugal If separation is difficult in a mixer-settler unit, a centrifugal extractor may be used in which the mixing and the separation extractor may be used in which the mixing and the separation stages are contained in the same unit which operates as a stages are contained in the same unit which operates as a differential contactor.differential contactor.

In the Podbielniak contactor,the heavy phase is driven In the Podbielniak contactor,the heavy phase is driven outwards by centrifugal force and the light phase is displaced outwards by centrifugal force and the light phase is displaced inwards. Referring to inwards. Referring to the the next figure, the heavy phases enters next figure, the heavy phases enters at D, passes to J and is driven out at B. The light phase enters at at D, passes to J and is driven out at B. The light phase enters at A and is displaced inwards towards to shaft and leaves at C. The A and is displaced inwards towards to shaft and leaves at C. The two liquids intermix in zone E where they are flowing two liquids intermix in zone E where they are flowing countercurrently through the perforated concentric elements countercurrently through the perforated concentric elements are separated in the spaces between. In zones F and G the are separated in the spaces between. In zones F and G the perforated elements are surfaces on which the small droplets of perforated elements are surfaces on which the small droplets of entrained liquid can coalesce, the large drops then being driven entrained liquid can coalesce, the large drops then being driven out by centrifugal force.out by centrifugal force.

Figure.Podbielniak contactor

The Alfa-Laval contactor shown in The Alfa-Laval contactor shown in thethe

figure, has a vertical spindle and the figure, has a vertical spindle and the rotor is fitted with concentric cylindrical rotor is fitted with concentric cylindrical inserts with helical wings forming a inserts with helical wings forming a series of spiral passages. The two series of spiral passages. The two phases are fed into the bottom, the light phases are fed into the bottom, the light phase being led to the periphery from phase being led to the periphery from which it flows inwards along the spiral, which it flows inwards along the spiral, with the heavy phase flowing with the heavy phase flowing countercurrently. High shear forces are countercurrently. High shear forces are thus generated giving higthus generated giving highh extraction extraction rates. rates.

Fig.Working principle of Alfa-Laval centrifugal extractor

EXTRACTION IN SUGAR EXTRACTION IN SUGAR INDUSTRY APPLICATIONSINDUSTRY APPLICATIONS

Extraction is needed for sucrose extraction from beets and Extraction is needed for sucrose extraction from beets and cane. cane.

Beets are washed and seperated from any remaining beet Beets are washed and seperated from any remaining beet leaves before processing.leaves before processing. The processing starts by slicing the beets into thin chips. The processing starts by slicing the beets into thin chips. The slicing is done with sharp knives which cut a V selection The slicing is done with sharp knives which cut a V selection slice 4 to 5 mm thickness to increase the surface area of the slice 4 to 5 mm thickness to increase the surface area of the beet to make it easier to extract the sugar. beet to make it easier to extract the sugar. The extraction takes place in diffusers. The two well The extraction takes place in diffusers. The two well known diffusers for sucrose extraction are The fixed-bed known diffusers for sucrose extraction are The fixed-bed or Robert diffusion battery and Continuous diffusion or Robert diffusion battery and Continuous diffusion batteries or Silver continuous diffuser.batteries or Silver continuous diffuser.

THE FİXED-BED OR ROBERT THE FİXED-BED OR ROBERT DİFFUSİON BATTERYDİFFUSİON BATTERY

This was developed primarily in the beet-sugar industry, but is This was developed primarily in the beet-sugar industry, but is also used for the extraction of tanning extracts from tanbark, also used for the extraction of tanning extracts from tanbark,

for the extraction of certain pharmaceuticals from barks and for the extraction of certain pharmaceuticals from barks and seeds, and similar processes. It consists of a row of vessels filled seeds, and similar processes. It consists of a row of vessels filled with the material to be extracted and through which water flows in with the material to be extracted and through which water flows in series.The piping is so arranged that the fresh water comes in series.The piping is so arranged that the fresh water comes in contact with the most nearly extracted material, and the strongest contact with the most nearly extracted material, and the strongest solution leaves from contact with the fresh material.Since each solution leaves from contact with the fresh material.Since each cell is filled and discharged completelycell is filled and discharged completely ,,

one at a time, each cell in the battery changes its position in the one at a time, each cell in the battery changes its position in the cycle,and therefore the piping must be so arranged that water can cycle,and therefore the piping must be so arranged that water can be fed to any cell, and the thick liquor drawn off from any cell, as be fed to any cell, and the thick liquor drawn off from any cell, as circumstances may dictate.The arrangement of valves and piping circumstances may dictate.The arrangement of valves and piping became standardized in the beet industry and is generally found became standardized in the beet industry and is generally found an all forms of diffusion battery.an all forms of diffusion battery. Figure shows that is a Figure shows that is a diagrammatic illustration of the principle of a diffusion battery.For diagrammatic illustration of the principle of a diffusion battery.For every vessel or cell there is a heater, because the diffusion every vessel or cell there is a heater, because the diffusion process takes place more rapidly at higher temperatures.Two process takes place more rapidly at higher temperatures.Two main headers are necessary .One handles water and the other main headers are necessary .One handles water and the other handles solution;and for every cell there must be three valves.In handles solution;and for every cell there must be three valves.In figure shows that the valves that are open are shown as circles figure shows that the valves that are open are shown as circles

and the valves that are closed are shown in solidand the valves that are closed are shown in solid black.black.

Fig.Diagram of diffusion batteryFig.Diagram of diffusion battery

Consider figure; Cell 1 is nearly exhausted and the cell 3 has just Consider figure; Cell 1 is nearly exhausted and the cell 3 has just

been charged.The space between the cossettes in cell 3 is been charged.The space between the cossettes in cell 3 is therefore filled with air.Water is introduced into cell 1 and flows therefore filled with air.Water is introduced into cell 1 and flows down through cell 2, and up through its heater.It would not be down through cell 2, and up through its heater.It would not be convenient to pass the solution down through cell 3 because of convenient to pass the solution down through cell 3 because of the air which would be entrapped;and the charge is cold, therefore the air which would be entrapped;and the charge is cold, therefore additional heating is desirable.Consequently, the liquid flows from additional heating is desirable.Consequently, the liquid flows from the heater of the cell 2 through the solution line, down through the the heater of the cell 2 through the solution line, down through the heater of cell 3,and up through cell 3. A vent at the top of this cell heater of cell 3,and up through cell 3. A vent at the top of this cell discharges air.When liquid appears at this vent, the valves are discharges air.When liquid appears at this vent, the valves are quickly changed to the position shown in figure.Liquid now flows quickly changed to the position shown in figure.Liquid now flows down through cell 3, up through its heater, and out tı the down through cell 3, up through its heater, and out tı the process.The operation shown in figure continued until cell 1 is process.The operation shown in figure continued until cell 1 is completely extracted.By this time another cell to the right of those completely extracted.By this time another cell to the right of those shown has been filled, cell 1 is dumped, water is introduced to cell shown has been filled, cell 1 is dumped, water is introduced to cell 2, and the process continued.In a diffusion battery for beet 2, and the process continued.In a diffusion battery for beet cossettes there may be from 10 to 15 cells.cossettes there may be from 10 to 15 cells.

CONTİNUOUS DİFFUSİON CONTİNUOUS DİFFUSİON BATTERİESBATTERİES

The next figure shows the Silver Continuous diffuser.The figure The next figure shows the Silver Continuous diffuser.The figure shows only three units; but actually the battery consists of 20 to 24 shows only three units; but actually the battery consists of 20 to 24 units arranged in two tiers, one above the other.The battery consists units arranged in two tiers, one above the other.The battery consists essentially of a series of closed troughs A,A’,A’’, each provided with a essentially of a series of closed troughs A,A’,A’’, each provided with a helical screw B.Cossettes are intoduced into the battery through helical screw B.Cossettes are intoduced into the battery through chute C and are carried together with the liquid in the direction chute C and are carried together with the liquid in the direction indicated by the arrows.At the end of the first trough is a Wheel D indicated by the arrows.At the end of the first trough is a Wheel D with inclined perforated buckets on the inside.It is so arranged that with inclined perforated buckets on the inside.It is so arranged that the screw B discharges the cossettes into this wheel, where they are the screw B discharges the cossettes into this wheel, where they are picked up by the buckets;drained free from juice lifted, and picked up by the buckets;drained free from juice lifted, and discharged through chute E which takes them into the second trough discharged through chute E which takes them into the second trough A. Here the helix carries them in the opposite direction discharges A. Here the helix carries them in the opposite direction discharges them from this to another wheel which in turn forwards them to them from this to another wheel which in turn forwards them to another trough A’’, and so on until they are exhausted and leave the another trough A’’, and so on until they are exhausted and leave the battery.battery.

Silver continuous diffuser:A,A’,A’’, extraction trougs; Silver continuous diffuser:A,A’,A’’, extraction trougs; B,conveyor for moving cossettes; C, feed chute; D, transfer B,conveyor for moving cossettes; C, feed chute; D, transfer Wheel; E, transfer chute for chips.Wheel; E, transfer chute for chips.