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Sugar Industry

Sugar Industry. Dr. S. R. Mane Associate Prof. & Head, Department of Chemistry, Smt. Kusumtai Rajarambapu Patil Kanya Mahavidyalaya , Islampur. Semester-V Paper-XII (Industrial Chemistry) 3. Sugar Industry Lectures- 7 3.1 Introduction

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Sugar Industry

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  1. Sugar Industry Dr. S. R. Mane Associate Prof. & Head, Department of Chemistry, Smt. KusumtaiRajarambapuPatilKanyaMahavidyalaya, Islampur

  2. Semester-VPaper-XII (Industrial Chemistry) 3. Sugar Industry Lectures- 7 3.1 Introduction 3.2 Manufacture of cane sugar, extraction, decolourisation, crystallization and other details of industrial process 3.3 Refining of raw sugar 3.4 Manufacturing of white sugar in India 3.5 Byproducts of sugar industry

  3. Introduction • Cane sugar is chemically known as sucrose. It is an important household commodity. Two majors source of sucrose are sugar cane & beet root . Indian industry is based on sugar cane. In 1747,a German chemist discovered that . Sugar can be crystallized from beet root extracts too. More than half of world sugar produced from sugar cane. Sugar cane is a large perennial tropical grass . It grows to a height varying from 10-15 feet. It has bamboo like stalk whose diameter varies from 2” to3”. The canes are transported into factory.

  4. Manufacture of cane Sugar Production of raw sugar is carried out in following operation 1)Extraction of juice:- The cane is first washed to remove dirt & mud. Then cut diagonal into small pieces by rapidly rotating knives . The cane chips are then send to milling train, consisting of a two rolled crusher followed by three rolled mills. The mill consists of three horizontal rollers arranged in triangular pattern. Only the top roll rotates & the two bottom rollers remain stationary

  5. The pressure on the top roller is maintained at 75-80 tons per meter of roller length . The cane juice collected in the pan . The raw juice is send to boiling house. The 2nd, 3rd & 4th mills are provided with simple containers . When the chips are crushed only about 60-70 % of juice extracted. The bagasse containing the rest of juice is then passed 1st , 2nd , 3rd , 4th mills. So the compound imbibitions technique is used. Hot water is sprayed on the bagasse passing through 3rd mill . The juice from the 3rd mill is sprayed between 1st & 2nd mill . The dilute juice from 4th mill is sprayed between 2nd & 3rd mill .The moistening of bagasse helps efficient extraction of cane juice.

  6. The approximate % of juice extracted by successive mill is as below. • 2] Clarification of juice:- • The cane juice collected from milling house is acidic , opaque and greenish Iiquid . It contain both soluble and insoluble impurities. The process of removing impurities from the cane juice is called clarification. • Lime defication process:- • The pH (5.1 -5.7) of freshly extracted juice increased to 7.5- 8.5 , by adding milk of lime addition of lime reduces loss of sucrose due to hydrolysis , increase in pH also causes coagulation of colloidal particles like proteins , pectin's ,gums,. • At this stage if the juice contains less than 3.0*10 -5 kg of phosphate / 100 ml of juice.

  7. Next, the limed juice is heated to 333K in juice –heaters . These heaters are simple brass tubules , where the cold juice & the high pressure hot steam are travelling in opposite direction . The juice heated to near boiling Heating helps in rapid coagulation of proteins &accelerates the settling process. The hot juice is then sent to settling tanks known as clarifiers.

  8. In the clarifier the hot limed juice separates into three layers. The top layer is of scum consisting of fine fiber particles & the bottom layer is of mud of heavy ppt. Middle layer consist of clear juice. The mud & scum are filtered under pressure to produce cakes , cakes are washed & the washing are send back to clarifier. • Concentration of juice to syrup:- • The clarified juice is dilute & contains about 85 % of water .it conc. In two stages by evaporating water . The first stage conc. Is done in multiple effect evaporators where water content is reduced to35% to form heavy syrup. • An evaporator is a tall (20’*10’) cylindrical bottle necked vessel made off mild steel. The top &bottom chambers are called juice chambers &middle chamber is steam chamber. The juice moves up through to the narrow tubes& comes down through the wider tubes. • The top 1st evaporator is connected to 2nd evaporator & top of 2nd evaporator is connected to the 3rd evaporator by the steam outlet pipe . • The steam outlet pipe of last evaporator is connected to the vacuum pan .

  9. The 1st evaporator is exhausted & it is heated by passing steam. As a result juice is heated &start boiling .Then water is evaporate from juice . The partially conc. Juice is moves to the 2nd Evaporator. It is exhausted to a greater degree than the 1st evaporator .The evaporation is repeated . The syrup of 2nd evaporator is more conc. As the same steam is used for heating the juice in three different evaporators, fuel is saved .Then water content is reduced to 9.11% leading from crystallization of sugar .

  10. Crystallization of sugar :- • The thick syrup is conc. In the single effect vaccum in pan also called as strick pan .It is heated with steam coils ,then it is heated with vaccum gauge ,condenser , thermometer , sampling stick, stirrer & safety device. The crystallization takes place in two stages given below: • Graining :- • It is induced in diff. ways , • 1) Waiting method :- • The syrup is cool down to break super saturation . • 2) Shock treatment method :- • Here super saturation is broken by sudden chilling . If the shining, small crystals are found on the plate , it indicates the break even point then crystals are mixed with the syrup in the pan & gives low grade sugar. • B) Growth of crystals :-

  11. When graining point is reached , more & more syrup is added in lots & mixed thoroughly . The crystal growth is allowed till the required grain size attained . During the growth , falls grains are likely to be formed . Finally same solid mass called as massequite ,consist of sucrose & molasses' . The mass equite containing 9-11% water is sent to crystallizer tank . The crystallizer tank , which has cooling attachment . Cooling reduces sucrose solubility . To attain maximum sugar recovery . Massequites are sent for centrifugation to recover sugar. 5) Centrifugation ( separation of crystals ) The sugar crystals are separated from mother liquor in centrifuge machine . The path followed by cane to raw sugar is given in fig.

  12. Refining of Raw Sugar

  13. Refining of raw sugar • It refers to the decolourisation of light brown raw sugar to produce pure white sugar. • Affination:- • The raw brown sugar is mixed with heavy mother liquor of 600 to800 brix. The mixing is done in special vessel called mingler, provided with a stirrer. This helps to remove molasses film & coloured impurity around the sugar crystals. The coating of impurities is removed & very little of sucrose goes into mother liquor. The mixture is centrifugate to separate the crystals from the mother liquor. Crystals are washed with hot water. Washed sugar are melted in water to a density of 55-60 brix. Potable water steam condensate are used for melting. The vessels used for melting is called Melter. This syrup is sent for defication. • b) Defication:- • The sugar solution at this stage some insoluble impurities are clarification during raw sugar manufacture. They are removed by defication. Liming, sulphitation & carbonation can be used. Liming is simplest chemical treatment. The syrup is limed to a neutral pH & then heated by steam.A flocculent precipitate is formed which carries the suspended impurities & colloids with it. Added the slurry of diatomaceous earth greatly enhances the process of defication. The treated liquor is filtered through a filter press.

  14. c) Decolourisation:- Filtered liquid obtain in step (b) is a clear, dark brown liquid still containing some dissolved impurities. So the liquid passed through beds of bone charcoal, kept in char tanks (12’*3’). When liquid percolates through the charcoal the coloured & some soluble impurities are selectively adsorbed on the charcoal & clear, colourless, pure syrup comes out of the char tanks. The disadvantage of this method is, adsorption cycle takes longer time & inorganic salts are not removed. When the bone charcoal is saturated, the emerging syrup becomes coloured. So, the bonechar is removed & reactivated. Alternative methods used for purifying the syrup are as under. 1)Activated carbon process:- The activated carbon is more effective decolourising agent. It is added to defecated juice & then filteed. Unlike in bonecharfilteration, it is faster & decolourization is more or less complete. 2)Ion exchange process:- It is more recent development, the syrup is passed through two set of ion exchange column & the charged impurity are certain on ion exchange coloum & uncharged sucrose come out. One set is filled with anion exchange resin & it retains the negatively charged impurities. While the other set of column is filled with cation exchange resin & it retains the positively charged impurities.

  15. 3) Sulphitation process:- Sulphur dioxide gas is used for decolourising the syrup. Usually double sulphotation is employed. 4) Carbonation process:- In this process excessive amount of lime is used to precipitate the gums, pectins etc. much more completely. The process is same as that explained in carbanationdefication except that, here the raw sugar syrup is used instead of cane juice. d)Crystallization & centrifugation:- The sugar syrup become, diluted to defication. It is sent to vaccum pan where it is concentrated under reduced pressure. The massecuite so produced is sent to Crystallizer. Then sucrose crystals are separated by centrifugation. It is washed & dumped in the wet sugar container. The mother liquor left after sucrose crystallization, is used for refining fresh batch of raw sugar i.e. in affication process.

  16. e) Drying process:- Sugar thus obtain 1-2 percent moisture is dried in granulator. A granulator is a horizontally rotating drum through which hot air is blown in opposite direction. When wet sugar passes through the hot air, it is dried.

  17. The syrup is decolourised to different degrees. The sugar is finally sieved through different mesh size & packed. • Manufacturing of White Sugar in India: • Manufacturing step involved are follows, • Extraction of juice:- • The cane juice is extracted by compound imbibition process. • 2) Clarification of juice:- • The cane juice containing water (78-86%), sucrose (10-20%), organic matter (0.5-1%), reducing sugar (0.5-2.5%) & ash (0.3-0.77%). Besides these it also contains fine pith, fibre & also some colloidal matter. They affect crystallization of sucrose & impart colour to it. So they removed by two clairification process.

  18. Sulphitation defication process:- • The cane juice is excessively limed (about 1-2 kg per ton cane) & heated to 333K. This increase the pH to alkalinity, as a result the colloidal particals & soluble phosphate salts separate out rapidally. Now sulphur dioxide gas is bubbled from limed juice till the pH is brought to 7. The heavy precipitate of calcium sulphite accelerates the sedimentation of caagulated particals. Sulphur dioxide also helps to bleach the juice o colourless liquid. • b) Carbonation defication process:- • Juice is heated to 328K & then excessively limed with lime water. • When carbon dioxide is bubbled through juice insoluble CaCO3 is formed. These carries with colloidal mass. Juice is filtered to remove precipitate &filtered obtain is heated to boiling. It is resaturated with carbon dioxide to break the bicarbonate formed & to remove any contaminants still remaining in the filtrate.

  19. c) Concentration of juice:- Concentrated to syrup containing 45-50% water in triple effect vaccum evaporator. d) Crystallization of sugar:- The thick sugar obtained from multiple effect evaporator is further concentrated to massecuite containing 9-11% water in strick pan. e) Centrifugation:- The sugar crystals are separated from mother liquor in centrifuge machine.

  20. By- products of Sugar Industry

  21. Growth and economy of any industry depends on the successful and complete utilisation of by products produced by it.This helps to reduce operational cost ,provides additional employment and reduces the risk of waste management. A great deal of attention has been paid to the meaningful utilisation of byproducts of sugar industry are bagasse and molasses. Bagasse:It is the spent cane or cane cane residue expelled from the last mill of mill house after the complete extraction of juice. It contains 52-58%of solid (including some sucrose)and the rest water. The solid is mainly cellulose fibre and pith. It is used for various purposes like; When other sources of energy like coal and electricity are not available, it is used as fuel for raising steam. This practice is most prevalent in our country.

  22. 2. It is used for the manufacture of hard board called celotex. It is stronger than wood. It is a bad conductor of heat so has high insulating value. 3. The pith is pentosan,it is separated from the fibre. Then by acid treatment it is dehydrated to furfural which is an important industrial chemical used in the manufacture of nylon intermediates. 4) After some pretreatment and mixing with nitrogenous nutrines it is used as cattle feed. 5)It may be degummed to manufacture valuable wax and gums.

  23. 6)It is used in the manufacture of paper for news print and also as fertilizer. B)Molasses: It is the mother liquor left behind after the crystallization of sucrose,it is also called as blank strap.Its composition is variable, approximate percentages of major components are given in table. Approximate composition and molasis:-

  24. Though the percentage of sucrose is appreciably high, it cannot be recovered. But it is utilized for following purposes. • In the manufacture of ethyl alcohol: The single most important use of molasses is in the manufacture of ethyl alcohol. The yeast cells are grown in the molasses nutrient medium. They consume the sugars present in molasses (glucose) and oxidize the sugars present in molasses to produce ethyl alcohol. From the culture medium ethyl alcohol is collected by distillation. The yeast residue so obtained is used as cattle feed. • In the production of other chemicals : Ethyl alcohol produced from yeast fermentation is an important raw material for the production of chemicals like acetaldehyde, acetone, acetic acid, butyl alcohol etc. • Molasses is a source of plenty of other rare chemicals like aconitic acid. • Directly molasses can be used as an adjunct in the manufacture of animal feed.

  25. THANK YOU

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