Sugar refining

Sugar refining steps are elaborately shown in the presentation

1. SUGAR REFINING

2. Types of sugar refinary
1. Those operating in
conjunction with raw
sugar house
2. independent
refineries – purchase
sugar from sugar
producers

3. Importance of sugar refining
•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)

4. SUGAR REFINING PROCESS

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 sugar mingled 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 trough with 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
•Affined sugar 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

11. Four compartment melter

12. •Each compartment has
–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 of melt
•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

14. CARBONATION

15. Carbonation
•Involves precipitation of 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 or more 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 gas from 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

19. PHOSPHATATION

20. Phosphatation
•Different from carbonation
•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

22. JACOBS PHOSPHATATION CLARIFIER

23. TALOFLOC PHOSPHATATION PROCESS

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 carbonation and Phosphatation

26. SULFITATION
•Objective
–Eliminates coloring matter
–Reduces colorless compounds ( ferric salts – which
formed by contact with mills and tanks)



➢Treating melt liquor with sulphur dioxide gas

28. Sulphitation process
•Fresh syrup 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

29. DECOLOURIZTION

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 Origin of 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 different group
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

38. TWO Stage system

39. RESIN REGENERATION
•Styrenic resins 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
•20 t 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 Activated carbon system
•Inlet liquor flow is upward direction
•Slight expansion , provide more surface area

47. OXIDANTS
•Less application
•Use of
–Ozone
–Hydrogen peroxide