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APPLICATION OF MEMBRANE FILTRATION TO THE SUGAR ANE FILTRATION TO THE SUGAR

INDUSTRY, STATE OF THE ART

ByEng. Abdul Aziz ABBARA1,*, Dr. Ali K. ABDEL-RAHMAN2,# ,Prof. Dr. Mohamed R. BAYOUMI31 Ph.D. student (on leave) at Sugar Technology Research Institute, Instructor at

Department ofFood Engineering, Al-Baath University, Homs, Syria.Email:abdazizabbara@yahoo.com2 Associate Professor at Mechanical Engineering Department, Assiut University, Egypt.3 Professor of Production Engineering and Mechanical Design, The dean of Sugar TechnologyResearch Institute, Assiut University, Egypt.

Abstract

As we enter the new millennium, the sugar technologists are being under pressureto eliminate

the industrial pollution, upgrading the quality of sugar with optimizing the energyconsumption. This requires modification of the conventional production process using newtechniques such as membrane technology.Membrane technology is currently a standard process in food and dairy industry,waterpurification, treatment of liquid effluent streams, and in the corn refining industry.In the few last years, researches have proven that the membrane technology could

hold greatpromise in reducing energy usage, reduction, or elimination of chemical clarification andimproved final product quality.This paper reviews the potential application of membrane filtration to the sugar

technology.

Keywords: Clarification, raw beet juice, raw cane juice, microfiltration, ultrafiltration.

Introduction

Diffusion beet juice or raw cane juice contains beside sucrose more than 50 nonsugarimpurities, like reducing sugars organic acids and non-organic acid, amino acids, proteins,starches, waxes, gums, minerals (such as potassium, magnesium, calcium, silica),

coloringmatters, and other suspended matters1,2. Separation of these impurities from the

juice as earlyas possible should be done by clarification to avoid the problems of increasingcolor, sucroseinversion, high viscosity, and the generation of excess molasses1. The quality of the productmainly depends on the efficiency of clarification3.

Because conventional clarification methods need heavy equipment and represent high

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operating costs, in addition create environmental problems4, the sugar industryhascontemplated the possible use of advanced technologies which were proven in otherindustries.

Membrane separation is one of such technologies that will compete favorably forreducing energy usage, reducing, or elimination of chemical clarification and improved finalproduct quality. Another promising area of application is in production of new products, suchas organic sugars5.

Today most membrane filtration systems use cross-flow (or tangential flow) filtration,where the feed stream flows across the membrane rather than through it. This helps to preventclogging of the membrane by retained particles6,7 .

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Based on the size (or molecular weight) of the targeted particles, membranes used infiltration are usually classified as reverse osmosis (RO), nanofiltration (NF),ultrafiltration(UF), or microfiltration (MF) filtersfiltration are usually classified as reverse osmosis (RO), nanofiltration (NF), ultrafiltration(UF), or microfiltration (MF) filters7.

The favored configurations for sugar industry applications include tubular for theceramic, carbon and stainless steel membranes, spiral wound and hollow fiber for

thepolymeric membranes6.

In the following paragraphs, the membrane seaparation process to the sugar industrywill be presented.

New Separation Process: Beet Sugar IndustryRaw juice clarification

Clarification of the raw beet juice using carbonation process is used by all sugarfactories worldwide with many modifications8.

Carbonation process is efficient in manufacturing a final sugar from raw beets,itnonetheless creates significant problems in respect of energy, raw material consumption andwater consumption, as well as handling and disposal of carbonatation sludge9,10.

Consequently, several processes using crossflow microfiltration or ultrafiltration havebeen proposed by different researchers as potential routes to reduce or eliminate the use oflime in the beet sugar factory 11-14.

Vaccari et al.11 proposed a method for direct production of commercial white sugarwithout using the traditional clarification process. The process, includes adding sodiumhydroxide to the raw juice to adjust the pH to 7 in order to limit the sucrose inversion bysubsequent steps. Then the raw juice is subjected to microfiltration using an organicmembrane having a pore size of 0.2 m. After that, the microfiltered juice is passed through acationic resin in the sodium form to eliminate the magnesium ion. Finally, the thin juice isconcentrated at low temperatures and three stages cooling crystallization

Results showed that commercial white sugar could be obtained directly without theneed of refining in the first crystallization step. The energy balance is largely in favor of thenew process in comparison with the traditional method 11.

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Clarification of press water

Another encouraging route to improve the quality of diffusion juice, which willbereflected on clarification, is to apply membrane filtration for clarification of

press water8.

Press water is a very dilute stream containing about 3-4% of total sugar entering hefactory. It is recycled back to a diffusion stage after pulp presses. Membrane filtration can beapplied for both press water sterilization and suspended solids removal8,15 .

Thin juice concentration

It was reported that approximately 50% of the energy utilized to produce beet andcane sugar is consumed during the evaporation of water. That is why the highestpotential for

energy reduction is concentration of clarified thin juice from 12 to 14% of refractometric drysubstance (RDS) to a maximum of 30% RDS while osmotic pressure is already about3.5MPa . However, many problems associated with thermal creep within the membrane modulesmust be further solved. Moreover, higher osmotic pressure of concentrated thin juice needshigher energy inputs, what impedes an easy industrial application 13.

Madsen16 has carried out pilot tests on nanofiltration of thin juice. The testsshowedthat it is possible to concentrate thin juice from approximately 14% sucrose content to 1719%sucrose content with an average approximately 30 l/(m2.h) at a filtration pressure of 40bar. The permeate has a sugar content of less than 0.5 %, and the purity of thepermeate isapproximately 60%. The best operating temperature is in the region of 70 oC. During one

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operations are mainly: producing higher quality sugar, increasing sugar recovery, reducingchemical usage in evaporator cleaning and reducing steam consumptionons are mainly: producing higher quality sugar, increasing sugar recovery, reducingchemical usage in evaporator cleaning and reducing steam consumption 24.

Clarification of syrup

During the evaporation of the clarified juice to the syrup, a considerable quantity ofnon-sugars that were soluble in the clarified juice became insoluble in the syrup due to theloss of 80 percent juice original water content. For this reason, evaporator syrup is usuallyalmost opaque.

Phosflotation is used for clarifying syrup as in blanco directo process 17,18. H

owever,the large calcium phosphate precipitates are friable and cannot be subjected tointensiveaeration which can only be obtained by violent mechanical means, if subject to intensiveaeration, a large portion of these precipitates are eroded and again somehow defeat the initial

intent of their optimum utilization25.

Saska7 discovered that nanofiltration of syrup through a membrane with pore sizeon

the order of 20 to 50 ANG. not only decolorizes the solution, but also producesa permeatehaving enhanced crystallization properties.New Separation Process: Raw Sugar Refining

Clarifying of sugar melt

Researches were performed to replace both the affination and clarification process bya single crossflow ultrafiltration4 or microfiltration26. This would simplify the process,eliminate the pollution problem and produce of a retentate, which can be easilyblended withfinal molasses of the refinery27.

Decolorization using ion exchange with brine recovery

The ion exchange resin process is considered as on of the most efficient methodfordecolorization sugar liquor. However, effluents resulting from alkaline brine regenerationcreate some disposal problems. This is due to the regeneration effluent contains

a highconcentration of sodium chloride and colored organics23.

To overcome these problems, Applexion developed a method for brine recovery usinglow cost spiral membrane. The color is concentrated in small volume of retentate, while in the

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permeate the main part of the salt is recovered, re-usable for a further resin regeneration28.Conclusions

Review of data indicated that micro-and ultrafiltration of raw beet, raw cane juicescan provide high quality permeate and therefore, improve sugar quality.

Applying membrane filtration to purify raw juices leads to eliminate or minimize

theconsumption of the lime.

Direct production of refined sugar from raw cane juice could be achieved by applyingmembrane filtration along with softening and chromatographic separation.References

[1] Gil G.E and P.H. Wright (1994). Process for producing refined sugar from raw

juices. USPatent No. 5,281,279.[2] Verma S.K., R. Srikanth, S.K. Das, and G. Venkidachalam (1996). An efficient

and novelapproach for clarification of sugarcane juice by micro-and ultrafiltration method. IndianJournal of chemical Technology, Vol. 3, 136-139.[3] Xian Z.S., Q.T. Qiu, X.X. Fei, and H.S. Qing (1998). Ultrasonic flotationalseparation ofsyrup with polyacrylamide. International Sugar Journal, Vol. 100, No. 1193, 221-222.[4] Lancrenon X., M.A. Theoleyre and G. Kientz (1993). Mineral membranes for the

sugarindustry. Sugar y Azucar, May, 39-45.

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[25] 25] Suzor C.L.N. (1979). Process for the purification of evaporated sugar solutions. USPatent No. 4,234,350.[26] Dornier M., R. Petermann and M. Decloux (1995). Influence of start- up procedure oncrossflow microfiltration of raw cane sugar. Journal of Food Engineering, Vol. 24, 213224.[27] Lancrenon X., D. Herve and F. Roussrt (1998). A new generation of cane sugarrefineries. International Sugar Journal, 100,1189,490-498.[28] Theoleyre M.A. (1999). Recent application of membrane filtration in the cane sugarindustry. New Orleans, Sept. 9-10.

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