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Sugar refining
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- 2. Types of sugarrefinary 1. Those operating in conjunction with raw sugar house 2. independent refineries – purchase sugar from sugar producers
- 3. Importance of sugarrefining • To remove impurities • To remove colour • To remove non sucrose substances • Consumer acceptability ➢ Refined sugar purity = >99.9 % ➢ ICUMSA Colour <45 ➢ International Commission for Uniform Methods of Sugar Analysis (ICUMSA)
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- 5. AFFINATION • Affination -removing the adhering film of molasses from the surface of the raw sugar crystal • Avg . Purity of film about 70% • purely mechanical process – Softening the adhering molasses film – Rubbing it off with other crystals – Dissolving it in affination greens – Crystal separated by centrifugal forces
- 6. MINGLING:……………Affination • Raw sugarmingled with green syrup forming magma • Then it is purged on batch or continuous centrifugals, and the crystals separated from the film of molasses are washed with water • Discharged sugar – affined sugar / washed sugar
- 7. • Green syrup –Low purity sugar solution (not less than 80% purity) – Has an high affinity towards impurities and non sugars – Capable for dissolving/ softening the adhering film ➢Generally 20 – 30 lb of green s required for 100 lb of raw sugar ➢Temperature = 72 deg.celcius, can obtain magma temperature of 49-60 deg.celcius ➢If adhering film hard magma temperature high, soft- magma temperature low
- 8. MINGLER • U-shaped troughwith a gate at the end • Capacity – 300 tons • Long = 18ft • Width = 3 ft • Shaft – connected to motor 20hp • Speed = 30-40 rpm • Insulation- avoid heat radiation • Arms are attached to shaft – which provide slight rubbing action between crystal
- 10. Affination- Melting • Affinedsugar or washed raw sugar melted before it is pretreated carbonation , lime treatment, etc • Sugar melted using sweet water • Sweet water – clean, free from microbes, neutral, free from inorganic salts • Standard type of melter – shallow wide tank
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- 12. • Each compartmenthas – Axial flow impeller – Draft tube • Over flow from one compartment is flow into next one – eliminate short circuiting • Circulation should be sufficient to keep all crystals in suspension- terminal setting velocity – < o.1 m/s • Heating – direct steam injection or in direct contact heater
- 13. Affination: Screening ofmelt • sugar is melted to the desired Brix , it should be screened before further treatment to eliminate lint, cane fibre, and other large impurities • A stationery rectangular vibrating screen • Mesh size depends on type and size of suspended matter
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- 15. Carbonation • Involves precipitationof calcium carbonate through addition of lime and contacting carbon dioxide gas • Crystalline mass formed , removes impurities followed by filtration to get clear liquid
- 17. Carbonation…………..SATURATORS • Two ormore saturator commonly used • First stage pH- 9.5 and most of gas absorption occur at this stage • Exit liquor pH less than 8.5 • Resistance time – 1 hr • Capacity of saturator vary depends on plant capacity • Gas distribution through nozzle at bottom
- 18. • Flue gasfrom boiler used in saturators • Flue gas pass through the scrub where other gases such as sulphur dioxide, NO2, etc can be removed Carbonation…………..FLUE GAS PRODUCTION
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- 20. Phosphatation • Different fromcarbonation • Phosphatation principle – flocculation • Carbonation – inclusion of impurities within calcium carbonate crystal • Phosphatation- formation of floc formed by addition of lime and phosphoric acid which captures fine colloidal matter and its is separated by flotation with dissolved air
- 21. JACOBS PHOSPHATATION CLARIFIER •Six U shaped trough • 760 mm deep at feed end and 150 mm at outlet end • Heating element – promote formation of small air bubbles • Scum remover running a length of clarifier
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- 24. • Lime density– 7 Baume • Melt liquor : Lime = 7:1 • Phosphoric acid - control pH up to 7.3 • Liquor temperature = 85 Deg. Celcius • Poly acrylamide (Taloflote ) = 10-12 mg/kg will be added • Poly acrylamide (Taloflote )- flocculants TALOFLOC PHOSPHATATION PROCESS contd…….
- 25. Comparison between carbonationand Phosphatation
- 26. SULFITATION • Objective – Eliminatescoloring matter – Reduces colorless compounds ( ferric salts – which formed by contact with mills and tanks) ➢ Treating melt liquor with sulphur dioxide gas
- 28. Sulphitation process • Freshsyrup from the contactor is taken to the ejector • Out going gas is scrubbed with the incoming fresh syrup • Resistance time 8 minutes • System capacity = 150 t/hr • 67 t/h liquid syrup to be treated with 345 m3/ hr
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- 30. INTRODUCTION • Pure sucrose– color less , but may appear colored because of inclusion of small amount of colored material • Objective: – Removal of colour
- 31. Nature and Originof colorants • Color originates from sugar cane – Cane variety , season • Through processing – Caramelization – Alkaline degradation ➢Caramelization – HADP (hexose alkaline degradation Products) at high temperature and melanoids at low temperarture
- 33. Characteristics of differentgroup colorants
- 34. Measurement of colour •Absorbance measure at pH= 7 ICUMSA = (A420 * 10000)/ ( . C) A420 = Absorbance at 420 = Cell Length C= Concentration
- 35. Method of decolorization •Ion Exchange decolorization • Bone Char / Activated carbon system • Use of oxidants
- 36. ION EXCHANGE DECOLORIZATION •Resins are strong base anion exchange resin in chloride form • Resins- Macro reticular resin rather than gel • Resin matrix any one or two types as follow 1. Styrenic resin • Made of styrene polymer • Remove more color but prone to fouling 2. Acrylic resin • Less fouling
- 37. ION EXCHANGE SYSTEM •Fixed bed columns – Volume = 6 and 16 m3 – Volume of vessel higher than resin – accommodate expansion on back washing – Diameter = 2.3 and 3 m – Vessel are rubber or glass lined to protect against corrosion – Flat bottom – Programmable logic controller – control valve operations – System – single stage or two stage – Second stage newer resin
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- 39. RESIN REGENERATION • Styrenicresins are more difficult to regenerate • Acrylic resins regenerated by sodium chloride solution • Regeneration takes place every 18-24 hr operation • Regeneration steps – Sweetening off – Back wash – Regeneration with 100g/L sodium chloride solution – Rinsing with soft water
- 40. BONE CHAR SYSTEM •Bone char- porous, black granular material • Prepared by heating bones in absence of air followed by grinding to a suitable granular condition • Used for decolorization • Composition – Tri calcium phosphate = 57-80% – Calcium carbonate = 6-10% – Carbon = 7-10%
- 41. CHAR SYSTEM • 20t char/ 100 t melt • Column depth 2-3 times of its dia meter • Continuous back wash regeneration draw back : –liquid outflow diverted to various destination, char run off • Regeneration system: ➢ Emptying , washing and refilling the column ➢ System non operational for significant portion of time
- 43. ACTIVAED CARBON SYSTEM •Granular activated carbon – effective color adsorbent • 90% carbon • Powdered carbon also used , its average size = 0.15 – 1 mm
- 44. • Cylindrical column •Liquor flowing downwards at a velocity of 3 – 4.5 m3/hr • Total contact time = 4.5-6 hrs • Bulk density = 450 kg/m3 • Volume = 400 m3 for 1000t/day ACTIVAED CARBON SYSTEM…..PROCESS
- 45. Regeneration of GAC •Regeneration of GAC done at high temperature furnance • Temperature 400- 900 deg.celcius • Thermal reactivation consists of three steps – Drying – Volatilization of impurities - which is adhere on the carbon surface decomposed in to hydro carbon, hydrogen, vapor – Gasification of carbonaceous residue left on the carbon particles
- 46. Pulsed system Activatedcarbon system •Inlet liquor flow is upward direction •Slight expansion , provide more surface area
- 47. OXIDANTS • Less application •Use of – Ozone – Hydrogen peroxide