1. Soda Recovery on Soda Recovery
Training at
Ballarpur Industries ltd.
Yamunanagar on
Soda Recovery
Resham Kaur

2. ABSTRACT
History-> The word paper derives from the Greek term for the ancient Egyptian writing material called papyrus, which was formed from beaten strips of papyrus plants. The soda process for making pulp from wood was developed by Watt & Burgess in NSSC pulping yields highest fibers up to 65%-80% which results in reduced stream pollution problems. But quality and bleachability is low. Types-> Chemical pulp is of three types 1) Kraft or Sulfate Pulp (Alkaline) 2) Sulfite Pulp (Acid) 3) Neutral Sulfite Semi-Chemical (NSSC) Pulp Density->The density of paper ranges from 250 kgm-3 (16 lbft-3) for tissue paper to 1500 kgm-3 (94 lbft-3) for some specialty paper. Printing paper is about 800 kgm-3 (50 lbft-3). In BILT, Unit: Kraft Process is employed for pulping. Veneer, Veneer chips, Bamboo, Poplar wood and Poplar rulla, Eucalyptus wood & rulla etc. are the raw materials used in that unit due to their easily availability in nearby areas
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3. SODA RECOVERY INTRODUCTION :
Recovery of chemicals has always been considered as the backbone of pulp and paper industry in the phase of increase of pulping chemicals. Strict laws of pollution control and power crisis arising from mushrooming of industries the recovery of pulping chemicals has become more important.

4. THE KRAFT PROCESS INTRODUCTION:
Kraft process is one of the main chemical pulping .
Kraft or sulfate pulping is an alkaline process .
It is cooked with a strong (12%) solution of NaOH and Na2CO The material added to the cooking liquor for the Kraft process is Na2SO4, hence the common name of sulfate process.
The cooking however is done with a solution containing Na2S, NaOH and Na2CO3 formed from the sulfate during preparation and recovery of the cooking liquor.
All sorts of wood can be cooked by the Kraft process and the fibers produced are bleachable and strong.
It is very important that the chemicals used can be recovered and recycled, reducing or even eliminating stream pollution.
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5. Flow sheet of Kraft Process
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6. ABBREVIATIONS USED: To Sewer Chipper House Condensate Chip Silo
To Sewer
Chipper House
Condensate
Chip Silo
Strong B/L Storage
Digester
Recovery Boilers
Blow Tank
ESP & Chimney
Brown Stock Chest
Smelt Dissolving Tanks
Pulp Washers
G/L Storage Tank
Degassing Tank
G/L Clarifier
Stock Tank
Stationary Slaker
Knitters, Rifflers and Screens
Causticizing Tanks
Beater
W/L Clarifier
Jordan
Mud Washers
Head Box
W/L Storage Tank
Fourdrinier
Vacuum Drum Filter
Dryer
Lime Kiln
Calendar Stack
Dregs
Finished Paper Roll
Producer Gas Plant
Weak B/L Storage
Multiple Effect Evaporators
Steam Line
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7. Pulping Procedures in Kraft Process
Cellulosic raw material : Almost any kind of wood,soft/hard
Principal reaction in the digester : Hydrolysis of lignin to alcohols and acids
Composition of cooking liquor : % solution of NaOH, Na2S;
58.6% NaOH, 27.1% Na2S, 14.3% Na2CO3.
Cooking conditions : Time 2-5 hours; Temperature 170 to
176˚C; Pressure kPa.
Chemical Recovery : through burning of organic matter dissolved in the liquor
from the wood.
Material of construction : can be made of mild steel or stainless.
Pulp characteristics : Brown color, difficult to bleach, strong fibers, resistant to mechanical refining.
Paper products : Strong brown bag, gumming paper, building paper, strong white
paper, paperboards and liquid containers.
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8. RECOVERY OF THE BLACK LIQUOR
The B/L removed from the pulp washer contains 95 to 98% of the total chemicals charged to the digester. Organic sulfur compounds are presented in combination with sodium sulfide. Na2CO3 is present as are also small amounts of Na2SO4, salt, silica and traces of lime, Fe2O3, alumina and potash. Total solids usually average about 20%. Then black liquor is concentrated, burned and limed. In the smelting furnace any remaining organic compounds are broken down, the carbon burned away and the inorganic chemicals melted. At the same time the following reaction takes place: Na2SO4 + 2C Na2S + 2CO2 The carbon comes from the organics in the wood.
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9. Soda Recovery-Flow Diagram:

10. Soda Recovery sub-sections:
Evaporator Section
Boiler Section
Causticizing Plant
Lime Kiln
Producer Gas Plant
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11. Evaporator Section :
In this section black liquor is concentrated to a required concentration and sent to the recovery boilers for heat recovery & formation of green liquor. The black liquor is concentrated with the help of evaporators. In this section there are mainly two types of evaporators, one is free flow falling film evaporator (FFFF) and other is short tube vertical effect evaporators (STVE).
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12. FORCED-CIRCULATION EVAPORATORS:
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13. SHORT-TUBE VERTICAL EVAPORATORS:
Principal use :evaporation of cane-sugar juice. Heating surface is induced by boiling in the tubes, which are usually 50.8 to 76.2 mm (2 to 3 in) in diameter by 1.2 to 1.8 m (4 to 6 ft) long. Body: vertical cylinder, usually of cast iron, and tubes are expanded into horizontal tube sheets Circulation rate through the tubes is many times the feed rate; so there must be a return passage from above the top tube sheet to below the bottom tube sheet. Most commonly used :central well or down-take
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14. ROLE OF RECOVERY BOILERS
Soda Recovery
  ROLE OF RECOVERY BOILERS
Feed - concentrated B/L coming from the evaporators. At both of these boilers B/L is fired to recover the heat content of the spent cooking liquor in form of production of high pressure steam. The lignin in the liquor is burnt away and what remain are the chemicals (in the form of smelt). This smelt is then dissolved in weak white liquor coming from Causticizing Plant, which gives a characteristic green color (hence called green liquor; G/L). This G/L contains some solid impurities which are separated out by means of a clarifier. The main aim of these boilers is to recover all unused chemicals from the B/L stream in form of G/L. Chemical composition of G/L is as follows: Na2CO3 (70%); NaOH (15%); Na2S(15%)
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15. Recovery Boilers
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16. RECOVERY BOILERS:
TYPES
ABL boiler
JMW boiler
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17. Differences b/w ABL & JMW Boilers
Points ABL JMW
Firing wall firing centre base
smelt Dissolving at the bottom at the top
tank agitator
FD fan after the ESP & gives fine gases to chimney before the ESP & gives fine gases to
ESP
sump pump used for mixing salt cake for better mixing same mixing tank is used for mixing
of two both ESP ash & salt cake.
soot blowers all are retractable type only 5 are retractable type and
rest of 17 are non-retractable
Automatic soot blowing Soot blowing is done manually
Steam used for taken from the steam produced by itself uses steam produced by other soot-blowing boiler for the same
ESP Two are used one is used
Pumps four pumps being used; two for recirculation two to serve both the purposes
and two for transferring liquor to
Causticizing Plant
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18. CAUSTICIZING PLANT:
Purpose-> To convert available Na2CO3 in useful NaOH by reacting it with Ca(OH)2 thus converting the supplied G/L into W/L in a number of steps.
consists of-> causticizers, clarifiers, mud washers, filters, dreg washers and grit classifiers etc.
Process->
G/L at ˚C from the smelt dissolving tank is pumped to raw G/L storage tank. G/L is screened over the storage tank to separate solids. Screened G/L is allowed to fall in a clarifier to separate out dregs. The temperature is always kept at ˚C so that slaking and causticizing reaction may take place in the causticizer tanks at desired rate. Clarified green liquor from the storage is supplied to splitting box. Lime is introduced in the slaker where G/L meets it from the splitter box in the slaker by two lines one in head and another in tale. Lime is transferred from lime bin. In the slaker causticizing reaction is completed around 80-90%.
The slaking reaction is as follows:-
CaO H2O Ca (OH) Heat (486 Btu/lb)
The resultant Ca(OH)2 reacts with sodium carbonate to form NaOH this reaction is called causticizing reaction:
Ca (OH) Na2CO NaOH CaCO3
Na2CO3(15%); NaOH(70%); Na2S(15%) 
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19. Details of Causticizing Plant
Daily G/L intake (ABL) : 510 m3 (JMW), 810 m3
G/L clarifier capacity : 280 m3 (Both)
Storage tank capacity : 165 m3 (All)
Lime bin capacity : 150 ton
W/L clarifier capacity (Old) : 650 m3(New), 400 m3
New mud washers capacity : 565 m3 (Both)
Steam line used for heating : 3 Kgcm-2 & 7 Kgcm-2
Dryness of mud after filter : 64%
Daily lime consumption : 77 ton
Number of clarifiers : 4
Number of mud washers : 4
Filter type filter : Rotary vacuum drum
Production(W/L ) : 855 m3 per day
Temperature in each step : ˚C
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20. LIME KILN Basically consists of :
mud filters, lime kiln, ESP and chimneys etc
In this unit we have one filter (Rotary Vacuum Drum Filter type), one lime kiln, one ESP and an ID fan.
Basic reaction that takes place inside a lime kiln is as follows:
CaCO CaO H2O Δ
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21. Constructional & working details
Length : 55 m
Diameter : 2.5 m
Feed end temperature : ˚C
Outlet zone temperature : ˚C
Feed rate : 150 ton per day
Average CaO in lime prepared from kin : %
Dryness of mud : %
% CaO in mud at feed end : 0.2 %
% free NaOH in mud at feed end : 0.4 %
Daily oil consumption : m3
Kiln speed : rpm
Kiln motor speed : rpm
Inlet & outlet draught for ESP : 12mmWC
& 120mmWC
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22. PRODUCER GAS PLANT: C + Air CO2 + N2 (ΔH1000˚C= -395.4 MJ/ Kmol)
Producer Gas (PG) is made by passing air stream through a bed of hot coal or coke. Temperature of the fuel bed depends on the fusion point of the fuel ash is to use up as much as possible, the exothermic energy from the reaction between C and O2 to supply the endothermic reaction between the C and steam:
C + Air CO2 + N (ΔH1000˚C= MJ/ Kmol)
CO2 + C CO (ΔH1000˚C= MJ/ Kmol)
C + H2O CO + H (ΔH1000˚C= MJ/ Kmol)
CO + H2O CO2+ H (ΔH1000˚C= MJ/ Kmol)
PG thus produced is used in lime kiln as fuel. Steam pressure helps in maintaining axial flame length while oil atomization controls radial flame spread.
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23. PRODUCER GAS PLANT-Few details
Coal feed rate : 20 ton per day
LCT-1 temperature : 135˚C
LCT-2 temperature : 142˚C
Furnace jacket temperature : 75˚C
Blast Saturation Temperatur : 55˚C
Blast Air pressure : 280 mmWC
Gas flow rate : 2730 m3/hour
Air flow rate : 1170 m3/hour
LCT-2 pressure : 125 mmWC
Steam pressure : 0.4 Kgcm-2
CO leakage level : ppm
Gas outlet temperature : 106˚C
Daily tar production : 1200 liter
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24. Thanks
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