SIT Paper #940

A Comparative Evaluation of Carbonatation and Phosphatation

A. S. Vawda

Savola Sugar Middle East, Avawda@savoia.com

ABSTRACT

Carbonatation and Phosphatation have been in use for many decades and each process has its supporters. In the last decade, changes in the raw sugar quality specification, cost of energy and environmental constraints have transformed the refining landscape.

This paper examines the selection of the most appropriate process on the basis of:

1. Capital cost. 2. Operating cost, 3. Process Capability. 4. Environmental concerns 5. Chemical Aids and Alternate Technologies.

Keywords: Carbonatation, Phosphatation, colour removal, clarification, turbidity removal, lime, filtration, flotation

Introduction

Liquor clarification is essentially a pre-treatment for the decolourization stage of sugar refining where the main objective is the removal of turbidity and colour. The choice of the process, whether carbonatation or Phosphatation is more suitable, is dependent on several criteria: -

Raw Sugar Quality, Turbidity Removal, Colour Removal, Process Capability, Capital cost, Operating costs, Sugar loss, Environmental concerns, Refined sugar quality.

Discussions about the criteria and the respective importance of each element, have in the past, generated numerous papers and discussions. With changes in the raw sugar supply landscape, cost of capital, environmental and energy concerns, a fresh review is needed, to evaluate the technical performance against the criteria mentioned above.

Although both technologies are in current use, there appears to be a trend to move towards Phosphatation in the last ten years with notable exceptions being the two biggest sugar refineries in the Middle East, located in Jeddah and Dubai.

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mailto:Avawda@savoia.com

This paper will attempt to review the advantages and disadvantages of each process and will also attempt to weigh them in order to allow the reader to make a judgement on each. Data has been collected mostly from the carbonatation plant in Jeddah, Saudi Arabia and the Phosphatation plant located in Port Sokna, Egypt. The Sokna plant is new and hence the data is supplemented by phosphatation refineries from around the world.

Description of the Carbonatation Process

The mechanism of carbonatation was described by Bennett 2 in a series of experiments conducted in the 70s.He demonstrated that the impurities are trapped within the growing calcium carbonate crystal. Microscopic examination of the calcium carbonate crystals revealed that the occluded impurities distorted the crystal, rather than being adsorbed onto the surface after precipitation.

Ca(OH) 2 + C 0 2 = CaCC-3 + H 2 0

The process consists of adding milk of lime (an aqueous slurry of calcium hydroxide) to the raw melt solution prior to entering a reaction vessel. The quantity of lime is in the range of 0.2 - 0.8% on sugar solids. Carbon dioxide gas is bubbled into hot liquor (75 -85° C) in saturators, under controlled conditions of pH and temperature. Generally the carbon di-oxide is added to the saturators in two or three stages, with the major part of the gassing carried out in the first saturator. Retention time varies from 45 minutes to 75 minutes. The concentration of the CO2 is about 12% and 30% from scrubbed flue gas and lime kilns respectively. The pH of the liquor leaving the final saturator is between 8.2 and 8.5. The impurities are both absorbed by, and trapped in, the conglomerated particles of the calcium carbonate precipitated by the reaction of the carbon dioxide and calcium hydroxide. The separation of the clear liquor and the calcium carbonate is done by pressure filtration. The filtered liquor is often re-filtered through filter aid as a safety filtration step. A significant portion of the calcium carbonate cake is required to act as a filter aid and growth of a suitable filtering carbonate cake is as important as colour removal. The calcium carbonate precipitate from the primary filtration requires secondary filtration and de-sweetening of the calcium carbonate precipitate, in press filters.

Description of the Phosphatation Process

The mechanism of Phosphatation is primarily the flocculation of impurity particles (Bennett) 2. The majority of colloids by nature are negatively charged and so the addition of cations such as calcium neutralises these charges and allows flocculation to take place. The anionic colour bodies are therefore most effectively removed by this process, and some soluble colours are absorbed by the tri-calcium phosphate. The open and bulky nature of the precipitate allows micro-flocs to be enmeshed in the precipitate mass. Larger particles must be screened because they do not float in the flotation clarifier.

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This process consists of adding phosphoric acid to hot raw melt at 0.015 - 0.025% P2O5 on brix depending on the sugar quality, i.e. colour and suspended solids. Lime in the form of lime sucrate is added almost simultaneously. The reaction produces a precipitate of tri-calcium phosphate, to which is added a flocculent to coagulate it. 1 1 (Davis)

3Ca(OH) 2 + 2 H 3 PO4 = Ca 3 (PO) 4 + H 2 0

The precipitate is very fine and cannot be easily filtered; therefore, the liquor is aerated by dispersed air and subject to flotation in a clarifier. The precipitate and other debris are scraped off as a scum. The scum is de-sweetened in several ways, the most popular of which is a series of two or three counter current clarifiers. The clear liquor underflow is led to one or two filtration processes where any carry over is removed.

Raw Sugar Quality In recent years, raw sugar has assumed increased economic importance with suppliers paying careful attention to the needs of customers. This has become more obvious since the advent of giant destination refineries. Brazil particularly, has stepped up to the challenge to market low colour highly filterable raw sugar, taking VHP into a new league, with the nomenclature W H P . The quality of raw sugar will have a direct impact on the performance of the plant and the refined sugar quality. Traditionally, the major requirements of a refiner are:-

1. Sugar that purges well during affination 2. Sugar that will clarify well, either phosphatation or carbonatation. 3. Sugar that decolourises easily 4. Sugar low in ash.

The raw sugar manufacturer focuses on the following criteria to deliver an acceptable final product

•Pol •Colour •Ash •Reducing sugars •Starch •Filterability •Moisture •Temperature •Insoluble solids

The big destination refineries renewed focus on plant efficiencies began when the LP sugar was dispensed of in favour of VHP. This had the immediate effect of reducing the quantity of recovery house material and increasing the white end capacity. With the increase in white end capacity, the filter station in carbonatation refineries became a

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bottleneck, especially when poor filterable sugars were processed. These filtration problems were communicated to the suppliers who implemented measures to control starch and insoluble solids. All this had the effect of moving from LP and VHP raw materials to products like QHP and W H P as shown in table 1.

Table 1 Comparative Info on Typical Sugar Availa jle in the International Market LP VHP W H P QHP

Pol 98 99.2 99.6 99.6 Colour ICU 3500 1500 450 700 Ash % 0.35 0.20 0.15 0.10 Invert % 0.50 0.25 0.15 0.15 Starch mg/1 300 250 110 50 Insolubles mg/1 NA 250 150 100

VHP is by far the most widely available raw material; W H P and QHP are supplied by two countries only. VHP has a starch content of about 250 ppm and this presents a filtration problem in carbonatation refineries. Phosphatation refineries on the other hand, do not have a tight filtration stage, and therefore are not affected by starch levels mentioned in Table 1.

The quality of raws has improved, notably the colour and turbidity of the sugar has decreased. However, the change in the colour of affinated sugar remained very much the same for all sugars after washing low pol sugar by affination, its quality is improved and the quality gap is narrowed between it and VHP sugar.

LA WHS TÍMATE 0 2 M H

BBH10 1

nano '

Figure 1 High molecular weight colourants in raw and refined sugar. 1 4

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Phosphatation is more flexible than carbonataron with regards to different sugar qualities, because phosphatation is relatively impervious to high starch and turbidity levels. (Mann, Personal communication)

Turbidity Removal Turbidity, often referred as insolubles, in melt is a combination of suspended matter in the sugar, (e.g., clay, silt, rust, bagacillo, and other plant material). The presence of "turbidity" results in the loss of clarity or transparency. Different sugar qualities have different turbidity levels, with VHP and W H P having significant lower insolubles levels. Refer to Table 1 for typical sugar qualities available.

Carbonatation removes turbidity by inclusion into the calcium carbonate crystal matrix. This means that very small particles are able to be occluded into the growing carbonate salt. During the precipitation, some impurities and high molecular compounds in the liquor are removed by co-precipitation . (Bento) The secondary process of turbidity removal is the pressure filtration through calcium carbonate granular media.

Phosphatation removes turbidity by flocculation of insolubles by charge neutralization. Particles without charge will not be targeted directly, but will be entrapped in the polyacrylamide flocculants in use. The secondary removal is the use of deep bed filters comprising of multi media and many refineries also resort to a third stage, generally pre-coated filters to protect the decolourization system.

The introduction of deep bed filters (DBFs) was a significant improvement to the phosphatation process. (Getaz, Personal Communication). Previously, any slight carryover resulted in severe reduction of the cycle time of the filters. Any malfunction of the DBFs or the secondary filter, caused severe pressure drop problems at the ion exchange columns.

A survey of several refineries show that carbonatation performs better than Phosphatation Colour Removal What is colour? Colour is evaluated by measuring absorbency at 420nm following the ICUMSA method which specifies the pH at 7.0.

There are basically four types of colour 1 2 (Davis):

• Plant pigments • Melanoidens • Caramels • Alkaline Degradation Products of Fructose (ADF)

The first originates from the sugar cane while the last three are created in factories and prove to be more difficult to remove in a refinery.

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Table 2 Summary of properties of cane sugar colourants 1 2 (Davis) Property Monomelic Intermediate Polymeric

Composition Mainly flavonoids Factory Colourants eg ADF

Factory colourants e.g. caramels, melanoidins

Molecular Weight (MW)

2500

Ion Neutral at low pH Cationic below pH 5 Anionic above pH 6

Cationic below pH 5 Anionic above pH 6

Polarity Least polar Intermediate Polar Indicator Value 5 - 4 0

Sensitive 3 - 4

Intermediate 1 - 2

Insensitive

Bennett 2 demonstrated that during carbonatation impurities are trapped within the growing calcium carbonate crystal. Bento 3 stated that during the precipitation, some impurities and high molecular compounds are co-precipitated. Chou stated that carbonatation is "particularly effective" in removing HMW colourants. Any kind of colour that has some acidic character and is capable of forming a weak linkage with calcium (i.e. a sparingly soluble calcium salt) will get incorporated into the precipitate. Kennedy et al found that carbonation precipitate had a high affinity for polymeric colourants which are anionic at high pHs. Refer to table 2. Colour removal by carbonatation is in the range 25 - 50%.

Saranin showed that the tri-calcium phosphate precipitate occludes and absorbs colour. Most colloids in nature and in cane sugar are anionic so the addition of a cation like calcium neutralises these charges and allows flocculation to take place. It has also been suggested that phosphatation has a lower removal capacity for flavonoids1 (Bardwell). Colour removal by phosphatation is in the range 20 - 35%. The use of cationic colour précipitants can increase the colour removal to 50%.

Why is carbonatation better at removing colour? The author postulates that it is probably because carbonatation is better in removing HMW colourants. We agree with Bento, that HMW colourants are associated with polysaccharides and the well known phenomenon of affinity of the HMW polysaccharides to sucrose provides the pathway for colour incorporating into the crystal. In a nutshell, what is good for polysaccharide removal is good for colour removal.

Table 3 shows the colour and polysaccharide removal as a function of membrane molecular weight cut off limits 9. (Chou) It should be noted that in general the % removal increase as pore size decreases, i.e. the tighter the filtration, the better the colour removal and carbonatation does indeed provide the tighter filtration.

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Table 3 Colour and polysaccharide residue as a function of membrane pore size. Membrane % % %

Molecular weight Removal Turbidity Removal Colour Removal cut-off Polysaccharide 10,000 99.5 89.0 90.8 35,000 100 85.3 84.0 75,000 88.5 60.8 81.0

Bennett 2 also provided data on TAP (Total Alcohol Precipitation) tests where he presented the following data. At a dosage of 0.5% CaO the polysaccharide removal was about 85% for carbonatation. At a dosage of 0.025% P2O5 the polysaccharide removal was only 40% for phosphatation.

Table 4 Polysaccharides removal of both processes expressed in % (Chen) Product Sample Carbonatation Phosphatation Raw Sugar 100 100 Affinated Sugar 48.4 47.6 Fine Liquor to pans 26.2 31.0 First Strike Sugar 5.4 10.6

Table 4 shows the reduction of polysaccharides of both processes. This example shows that twice the amounts of polysaccharides are left behind in the crystal when comparing both processes.

Process Capability

Removal Table 5. Typical impurity removal information comparing both processes.

Removal % Analysis Carbonatation

0.5% CaO Phosphatation 0.025 % P 2 O s

Colour 55 35 Turbidity 95 88

Starch 93 95 Polysaccharides (TAP) 91 62

Sulphate 86 28 Phosphate 100 88

Magnesium 67 35

The carbonatation process is known to add lactic acid to the process. (Cox et al).Overall, the carbonatation process is a more efficient remover of impurities.

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Colour Transfer The term colour transfer is used to describe the incorporation of colour into the sucrose crystal during crystallization. It can be defined as the ratio of colour of the affinated crystal to the colour of pan feed.

Lionnet (1995) conducted experiments where he used various liquors to boils massecuites and separate the crystals 1 6. The main objective of his work was to investigate the performance of decolourization process used at local refineries. Lionnet reported the results of two refineries operating carbonatation: ion exchange and phosphatation: ion exchange. He reported data that showed that the colour transfer of carbonatation was superior to that of phosphatation as shown in Table 6.

Table ó.Colour transfer comparison carbonatation and phosphatation Feed Colour Crystal Colour

Carbonatation ion exchange

Phosphatation ion exchange

200 12.8 17.1 400 17.4 21.9 600 22.1 26.8 800 26.7 31.6

The Savola Behshahr beet factory in Hamedan, Iran, (carbonatation) uses the Russian boiling scheme for off season refining and a single white sugar of 50 - 80 ICU is produced with a feed colour of 800 - 1000 ICU. This type of colour transfer is typical of beet factories, where the invert is destroyed during carbonatation. Lionnet conducted further work, here he subjected carbonatation liquors to a high pH and boiled the liquors in a pilot pan. The results of the colour transfer may be seen in Table 7.

Table 7. Colour transfer of normal and ADP rich liquors. Feed Colours ITJ Crystal Colours IU

Normal Degraded Normal Degraded 385 614 22 20 586 811 27 28 913 1010 34 27

It is believed that the higher operating pH of liquors reduces inversion. Invert, especially fructose, is one of many pre-cursors of colour. Phosphatation refineries show higher invert gain, about 0.025% compared to carbonatation refinery liquor gain of 0.012%.

Carbonatation is superior to phosphatation with respect to colour transfer,

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Cost of Carbonatation vs Phosphatation

Capital Cost

Carbonatation requires more capital investment than phosphatation due to the type and number of equipment required. Appendix 1 lists most of the equipment required for a carbonatation process and the total installed power for a 2000 tpd factory is about 1.6MW. Appendix lists most of the major equipment in a Phosphatation factory. Both comparisons exclude liquor pumps. The total installed power of a 2000 tpd phosphatation factory is HOkW

An exercise conducted in 2007 provided a stark contrast of the capital cost of both systems, the fully installed costs shown in Table 8. Both plants are fully automated with one attendant per shift.

Table 8 Comparative capii ;al costs of both processes. Carbonatation Phosphatation

Equipment Costs 7.1 1 Installation Cost Total 7.0 1 Total 7.0 1 I.e. carbonatation equipment costs seven times more than phosphatation.

Operational Cost

The costs of both processes are mainly chemicals and power. It must be noted that the price of chemicals and power varies at different locations.

Table 9 Comparative electrical costs Carbonatation Phosphatation

Electrical Consumption kW/h 750 75 Cost of Electricity USD 0.02 0.02 Cost per Ton Sugar USD 0.17 0.02

Table 10 Cost comparison: chemicals, maintenance and steam Units Carbonatation Phosphatation

Installed Electrical kW/RSO 18 1 Chemical Costs USD/Ton RSO 0.85 2.4 Maintenance USD/TRSO/PA 0.4 0.1 Additional Steam Tons/hr 12 Base Case

The Jeddah carbonatation refinery fine liquor operates at 5 brix points less that the Sokna refinery. If we assume the cost of oil at USD90 per barrel, the cost of a ton of steam is somewhere in the region of USD25 per ton. In a conventional 2000 tpd factory without vapour bleeding, this would amount to an additional USD 0.15 per ton refined sugar for a carbonatation refinery.

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Carbonatation factories have an edge with respect to chemical costs. The costs of commodity and speciality chemicals have doubled in the last three years and this has affected phosphatation severely. For the Middle Eastern region, the costs of chemicals for both processes are shown in Table 11

Table 11 Cost comparison: chemicals. Jede ah vs Sokna refineries Units Carbonatation Phosphatation

Chemical Costs USD/Ton RSO 0.85 2.4

The additional cost of phosphatation is USD1.55 per ton refined sugar above that of carbonatation.

Comparing the Jeddah and Sokna refineries; the cost are shown in table 12 together with an international cost

Table 12 Total operational cost, carbonatation vs phosphatation Units Carbonatation Phosphatation

Operating cost Middle East

USD/Ton RSO 1.47 2.81

Operating cost Internationa)

USD/Ton RSO 5.54 2.41

The international operating cost is significantly affected by energy costs. Clearly, in the Middle East, the cheaper energy cost makes carbonatation more cost effective than phosphatation.

Environmental Issues The carbonatation process generates six to seven times more effluent than phosphatation in terms of insolubles by weight. Its de-sweetening therefore produces more sweet water than phosphatation. The use of steam sluice systems in the new generation filters has narrowed the gap between water consumption of phosphatation and carbonatation systems. The carbonate sludge poses a cost and environmental problem except in areas where agricultural requirements utilise it as a soil pH conditioner. Phosphatation sludge, though smaller in quantity, is potentially far more polluting. It needs to be kept dry as possible and deposited at a solid waste disposal site.

Sucrose Losses The brix of effluent from carbonatation is typically 1 degree brix, while for phosphatation it is 0,3 degrees brix. The variance and the difference in volume results in a daily sugar

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loss in carbonatation of some 425 kg while the equivalent figure for phosphatation is 43 kg. (Alder, Personal Communication) Generally, phosphatation refineries show a higher sucrose loss compared to carbonatation factories. It is believed that the reason for this is the lower pH at which the refinery operates. (SIT Symposium SIT628D, 1992). Carbonatation, in this regards has a head start due to the pH being in the region of 8.5.

Chemical Aids and Alternate Technologies. Physical separation of impurities can be the ultimate clarification process and has been used in the past. Due simply to the fact that dead-end filtration can be costly and frustrating, this process is only used in a few refineries whose raw material is of an exceptionally high specification. Figure 2 shows that if one removes insolubles to a pore size of 0.45 microns, most of the insolubles will be removed. Approximately 97% of the material is greater than 0.45um.

Graph showing parBcIa size of Insolublea In Melt.

Partiels Six* (micron)

Figure 2 Particle sizes of impurities in W H P melt, measured by laser diffraction

Membranes Pilot plant work carried out on W H P melt showed promising results on qualitative performance, but the low flux made it financially unfeasible 2 0. The data is shown on Table 13.

Table 13 Results of membrane filtration on W r P melt using polymeric membranes Membrane MWCOorPore Size Flow LMH P Bar PES-20 PVDF-65 0.05 um Teflon 5 um Teflon 0.1 um Teflon

200,00 da 250,00 da 0.05 um

5 um 0.1 um

30.6 31.7 26.3 43.2 37.4

3.5 3.5 3.5 3.5 3.5

cmbrane area 0.5 Sq. ] Ft. Brix 62.3 Temperature 80 deg C. VCF of 90%

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It was seen that when using W H P melt, viscosity was the most significant impediment to flux rate. Diluting the melt was not an option for energy conservation reasons. The 0.1 jam and 0.05 urn membranes performed equally well, indicating that the major foulant particle size was larger than 0.1 um and was not contributing to premature clogging. The turbidity removal was 97.8% and colour removal 42.6%, indicating that membranes can deliver good performance 2 0.

Adsorbents Adsorbents with carbonatation Full scale trials were conducted using adsorbents. The adsorbent product was added to the melter at a rate of 0.50 kg/tonne and the process was carefully monitored. The colour removal of the total carbonatation process improved from 35% to 70%. There was a significant improvement in average filterability from 118 LMH to 142 LMH over an eight hour monitoring period. (Bogari. Personal Communication). However, the costs are only justifiable when the price of sugar is low or when the adsorbent is used to overcome processing difficulties in quality and throughput, i.e. when used as a process aid.

Adsorbents by-passing carbonatation Full scale trials were conducted using adsorbents dosed into melt in parallel with the carbonatation process. The colour removal on the adsorbent line was 52% while the carbonatation line performed at 36%. One of our concerns was the removal of polysaccharides and this was monitored. Polysaccharide in raw sugar was 2800 ppm and the polysaccharide in refined sugar was 1126ppm and 868ppm for carbonatation and adsorbents respectively. Turbidity for both processes was similar. Therefore the adsorbent process was accepted as a suitable alternative to the carbonatation process. However, the cost of the chemicals was deemed to be high and a plan has been envisaged to optimise the cost in the near future.

Conclusion Ten to fifteen years ago, the answer to the question, "which process is better" would have been easy. Carbonatation was the most effective technical and commercial solution in sugar refining. Today, the situation has changed. The costs of energy and chemicals have increased tremendously. Phosphoric acid prices are linked to the price of fertiliser and food; both are expected to remain high in the future. Lime prices are affected by the fuel price due to the energy requirements of the manufacturing process. The quality of raw sugar has improved as well and this trend will continue. The choice of a suitable process would depend on the economics taking into account all factors. In some cases carbonatation would be suitable because of the use of cheaper and freely available chemicals; in other cases Phosphatation would be more appropriate because of local conditions.

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Acknowledgements The author is grateful to the management of Savola for allowing this paper to be published.

Personal communications, data and advice from the following persons are also gratefully acknowledged.

Philip Alder - Tate and Lyle Process Technology. For technical data. Khalid Bahakeem - United Sugar Company. For chemical cost data Ayman Bogari - United Sugar Company. For USC trial data. Dr Luis Bento - Independent Consultant. For inspiration and information. Tom Craig - Independent Consultant. For historical data. TTevor Endres - Booker Tate. For equipment costing and endless proof reading. Mike Getaz - Fives Fletcher Ltd. For case studies. Dr Raoul Lionnet - Tongaat Hulett Sugar. For technical advice. Graham Mann - Illovo Sugar. For technical information. Barry Phillips - Illovo Sugar. For reference material. Mano Moodley- Tongaat Hulett Sugar. Technical advice. Keith Taylor - Illovo Sugar Ltd. For reference material. Faisal Al Wagdani - United Sugar Company. For laboratory analysis.

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REFERENCES 1) Bardwell, D.J, Croker, J.R, and Paton, N.H, (1985). Recent Application of Colour Fractionation in

CSR Refineries, Proceedings of the 44 t h Sugar Industry Technologist Conference.

2) Bennett, MC (1974) Physical chemistry of phosphatation and carbonatation. International Sugar Journal 69, pp 68-73.

3) Bento L.S.M., (1999), Study of colour formation during Carbonatation in Cane Sugar Refining using GPC with a ELS detector, Proc, of A.V.H. Conf.

4) Carpenter, Frank. Bone Char Research Projects, Technical Report No. 69.

5) Clarke, Margret A et al. (1992). Polysaccharide of beet and cane sugar: a progress report. Proceeding of the Sugar Processing Research Conference, pp353-364

6) Chen, J.C.P, Chou, C. (1993) Cane Sugar Handbook, 12 t h Edition. John Wiley and Son,P 457-458

7) Chou, C.C. Sugar Processing- Where are we going? International Sugar Journal, May 2001, pp 216-223

8) Chou, C. C ; Rizzuto, A. E. (1972). The Acidic Nature of Sugar Colorants. Proceedings of the 1972 Technical Session on Cane Sugar Refining Research, pp. 8- 22.

9) Chou, C. C. (2001) Process Development Projects for the New Millennium, Proceeding of the Technical Meeting of Sugar Industry Technologists, Inc. P 163.

10) Chou, C. C. Iqbal, Khalid. (2002) White and Refined sugar production from Cane Sugar Factories. First Biennial World Conference on Recent Development in Sugar Technology.

11) Cox, MGS, Mohabir.K and Bervoets, A (1990) Ash gain due to lactic acid formation during carbonatation. Proceedings of the 66* South African Sugar Technologists Association.

12) Davis, S (2001). The Chemistry of Colour Removal: A processing perspective, Proc S African Sugar Technology Ass 75: 328-336

13) Donovan, M.; Williams, J. C. (1992). The Factors Influencing tiie Transfer of Colour to Sugar Crystals. Proceedings of the 1992 Sugar Processing Research Conference, pp. 31-48.

14) Godshall, M.A. (2005). Understanding and Controlling Color Development in Mills and Refineries. Paper 8 80.Proceedings of the 44 l h Sugar Industry Technologist Conference.

15) Lionnet, G. R. E. (1987). Impurity Transfer During A-Massecuite Boiling. Proceedings of the South African Sugar Technologists Association, pp. 70-75.

16) Lionnet, R. (1995) Colour Transfer in the South African Cane Sugar Industry. Proceedings of the ISSCT XXII Congress.

17) Mersad, A. Lewandroski, R and Decloux, M. (2000).Colorants in Cane Sugar Industry. Proceedings of the 66 t h Sugar Industry Technologist Conference.

18) Saranin, A.P. (1972) The technology of Phosflotation of Sugar Melt. Vol 2. Elsevier Publishing Company. Amsterdam.

19) Shore, M.; Broughton, N. W.; Dutton, J. V.; Sissons, A. (1984). Factors Affecting White Sugar Color. Sugar Technology Reviews, 12: 1-99

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20) Vawda, A.S. (2003) Direct Filtration Development. Internal Memorandum. Al Khaleej Sugar LLC.

Appendix 1

Carbonatation Equipment

No. Description No. Description

1 Lime Vibrator 35 Horizontal Leaf Filters x 9 2 Lime Vibrator 36 Precoat mixing tank mixer

3 Hydrated lime transfer Screw Conveyor 37 Sweet sludge tank agitator

4 Lime Silo 38 Filter acid premix pot mixer 5 MOL storage tank stirrer 39 Filter acid mixing tank mixer 6 MOL storage tank stirrer 40 Filter filling supply tank agitator 7 Liquor/MOL mixing tank mixer 41 Cloudy liquor pump 8 MOL transfer pumps 42 Cloudy liquor pump

9 MOL transfer pump 43 Cloudy liquor pump for vertical filters

10 MOL circulating pump 44 Sweet sludge pump 11 MOL circulating pump 45 Sweet sludge pump 12 Aeration blower 46 Sweet sludge pump 13 Lime sump pump 47 Sluicing water pump 14 MOL mixing tank stirrer 48 Sluicing water pump

15 C 0 2 gas compressors 49 Clear liquor pump

16 C 0 2 gas compressors 50 Clear liquor pump

17 C 0 2 gas compressors 51 Wash water pump

18 CO z gas compressors 52 Wash water pump 19 Saturator 53 Polished Liquor pump 20 Saturator 54 Polished Liquor pump 21 Saturator 55 Precoat mixing pump 22 Saturator 56 Precoat mixing pump 23 Sea water return pump 57 Filter sludge pump 24 Sea water return pump 58 Filter supply tank stirrer 25 Soda ash recirculation pumps 59 New filter supply pump 26 Soda ash recirculation pumps 60 New filter supply pump 27 Soda ash mixing tank stirrer 61 Filter filling pumps 28 Soda supply pumps 62 Filter filling pumps 29 Soda supply pumps 63 Mud filter press 30 Filter supply pumps 64 Mud filter press 31 Filter supply pumps 65 Polishing filters 32 Filter supply pump for vertical filters 66 Polishing filters 33 Filter supply pump for vertical filters 67 Sweet sludge tank stirrer 34 Tanks x 3 68 Cake Conveyor

69 Cake Conveyor

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Appendix 2

Phosphatat ion Equipment

1 Buffer Tank Agitator 22 Deep Bed Filter

2 Reaction Tank Agitator 23 Deep Bed Filter

3 Reaction Tank Agitator 24 Deep Bed Filter

4 Lime Sucrate Prep. Tank Agitator 25 Deep Bed Filter

5 Flocculant Preparation Tank Agitator 26 Deep Bed Filter

6 M.O.L Agitator 27 Dry Cake Filter

7 Scum Holding Tank Agitator 2B M.O.L Preparation Pump

8 Scum Mixing Tank x 3 29 Aeration Pump x 6

9 Decolourised Liquor Tank + Agitator 30 Reaction & Aeration Tank

10 Pre coat Tank + Agitator 31 Lime Sucrate Preparation Tank 11 Syrup Distribution Tank + Agitator 32 Lime Sucrate Holding Tank

12 Slurry Tank + Agitator 33 M.O.L Preparation Tank

13 Flotation Clarifier 34 Scum Feed Tank

14 Flotation Clarifier 35 Low Brix Sweetwater Tank

15 Flotation Clarifier 36 Mid Brix Sweetwater Tank

16 1st Stage Scum Mixing Tank 37 Filter Feed Tank

17 1st Stage Scum Clarifier 38 Cavitation Aerator

18 2nd Stage Scum Mixing Tank 39 Cavitation Aerator

19 2nd Stage Scum Clarifier 40 Cavitation Aerator

20 3rd Stage Scum Mixing Tank 41 Clarifier Gate Arm Drive x 5

21 3nd Stage Scum Clarifier 42 Chemical dosing pumps x 8

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