As the name suggests the recovery section was installed to recover the cooking chemicals from the Black liquor received from the Brown Stock Washing section. Although, this section is much cost-intensive it needs to be installed to avoid the use of 100% fresh cooking chemicals. As the losses in the Brown Stock Washing is 8-12%, the requirement of the fresh chemicals will be only 8-12%.

The main subheads in the Recovery plant are,

• Multiple Effect Evaporators
• Low-Temperature Incinerator
• Recaustisicing Plant

Multiple Effect Evaporator Section

The Black Liquor received from Brown Stock Washing Section is having a concentration of 0.8- 1.5% depending upon the use of Raw Material. The Concentration of Black Liquor is increased to 25-30% in the evaporator section. There are different types of evaporators being used in the paper industry depending upon the quality of Black Liquor. These are Long Tube Vertical evaporators, Falling Film Evaporators, Natural Circulation Evaporators, etc.

The most common evaporator being used in the paper industry are Falling Film Evaporators which are having advantages over Long Tube Vertical Evaporators, which are as follows.

• In Falling Film Evaporator, the black Liquor is pumped from the Vapour Head to the Distribution Plates located above the Tubes allowing the liquor to fall down within the tubes.
• The Falling Film Evaporator working at a low Temp. Difference and which allows many effects to be installed in series. It also has a better steam economy than other types of evaporators.

Low-Temperature Incinerator

The basic concept of this system is the use of fluidized bed technique for the treatment of black liquor received from Multiple Effect Evaporator to recover the Pulping chemicals as well as to reduce the pollution load on the environment. The Low-Temperature Incinerator is used in the paper mill, where the Black Liquor solids are less than 300 tons per day.

IN LTI, The solids in the liquid waste containing heat energy are amenable. The advantage of LTI is,

• Elimination of Air as well as Water Pollution.
• Removal of BOD & color, etc. from residual organic products.
• Removal of all particulate matter & gases before discharged into the atmosphere.

The system consists of mainly

• Low-Temperature Incinerator Proper With Accessories
• Venturi Scrubber System with Cyclone Separator
• Attrition Mill and other Accessories
• Air Pre-heater with HSD Burner

The Semi Concentrated Black Liquor from the evaporator is fed to Venturi Scrubber, which works on the Direct Contact Evaporator. The Concentration of Black Liquor is increased to 45%. This Black Liquor is fed to LTI- where the Temp. Is around 600-700 Deg. C is maintained. The water in the Black Liquor is evaporated & the solids are converted to Soda Ash.

The Soda Ash produced is withdrawn from the side of the reactor at a controlled rate by a variable speed Rotary Valve. The Soda Ash is conveyed through Water Cooled Screw Conveyor before being stored in a Silo.

Recaustisizing Plant

The Soda Ash (NA2CO3) produced in the LTI- is further treated with milk of lime (Ca(OH)2) to get Caustic Soda (NaOH) which is used in the Digester for the Cooking of the Raw Material & the Calcium Carbonate (CaCO3) produced is either used as Landfills or sold to Cement Industry.

The Major Equipment in Recaustisicing Section is as below.

• Lime Slurry Preparation
  • Table Feeder: A table Feeder is installed to feed the lime to slaker at a controlled rate.
  • Rotary Drum Slaker: In Drum Slaker, the water is added along with the lime to make the slurry. The slaker rotates at a fixed speed & required time is given to complete the reaction. The grits in the lime are removed from the slaker.
  • Classifier: The green liquor from LTI Section is mixed with Lime Slurry in Rake Classifier. Any grits in the system are removed in the Classifier.
  • Causticizer: The Slurry from Rake Classifier is pumped to Causticizer, which is installed in series to provide the required retention time to complete the reaction. The Causticizer has an agitator & the size depends on the size capacity.
  • White Liquor Clarifier: The slurry from Causticizer is pumped to White Liquor Clarifier, which is provided with a rake mechanism having blades to ring the sludge in the center. The Overflow from the clarifier is taken to the Storage Tank, from where it is pumped to the Digester House to be used as Cooking chemicals.
  • Recausticizers: The underflow from White Liquor Clarifier, is taken to Recausticizers- where it is mixed with Washed Liquor from Ist stage Lime Mud Washer.
  • Lime Mud Washer: Lime Mud Washers are similar to White liquor Clarifier, which are provided with Rake Mechanism. The Lime Mud Washers are provided in Series to recover the chemicals from the Lime Sludge & the wash water is used in the Counter-Current system.
  • Lime Mud Filter: The Sludge from the final Lime Mud Washer is pumped to Lime Mud Filter, which works on the vacuum. The inlet consistency of lime sludge is around 1-1.5% and outlet consistency is around 60%. The lime sludge from the lime mud filter can be used either in landfills can be sold. Lime Mud Filter is provided with a filtrate tank.

The purpose of de-inking is to remove the printing inks and stickies that might affect the paper-making process. In a de-inking process, ink is detached from the fiber. Flotation technology provides a high yield of fibers and simple handling with maximum operating reliability.

Principle Of Operation

The JMC De-inking cell consists of a number of cells in series with an elliptical cross-section with a baffle extending over the entire length to separate the suspension chamber from the foam collecting chamber. Air (at the atmospheric pressure) and pulp stock are introduced into the cell through injectors. Flow-through nozzles generate a vacuum which generates microturbulence resulting in widely ranging bubble sizes enabling efficient removal of ink of particles. This enhances brightness to a high degree and reduces dirt specks and stickies. The injectors optimize the quantity of air injected and the size of the bubbles generated.

The pulp stock freed from the ink is pumped from the bottom of one cell to the next cell. The ink-laden foam overflows into the foam chamber with the help of a motorized paddle. The flotation process is operated in a continuous mode and helps to remove ink particles efficiently. Since the cells are interconnected level is controlled through a level transmitter on the entire flotation machine.
The primary flotation stage ensures the highest possible stock purity and the secondary stage optimizes yield. A Deaerator cyclone removes air from the stock and usable fibers are recovered from the foam.

Salient features of the
JMC De-Inking Cell, Flotation Model

• The highest possible degree of brightness is achieved
• Improved optical cleanliness in recovered paper stock.
• No sizing restrictions
• Single-level control loop operation.
• Optimized flotation yield at the secondary stage without loss of brightness and cleanliness.
• Very low fiber loss in the de-inking process as the foam is treated in a cascade process.

• Most suitable in screening of pulp slurries with high trash and flake content.
• Can be used as a secondary screen.
• Online contaminants removal of both light & heavy reject.
• Sturdy design with S.S. body or M.S. with S.S. linning

• Efficient Separation of Heavy contamination by Centrifugal Force.
• Min. Fiber Loss
• Lighting arrangement for complete visibility of separation Process.
• Clogging free operation.

Salient Features

• Medium consistency pulper -consistency range 4-6.5%
• Slushing of dry or moist pulp
• Slushing of waste paper, broke, in loose or in bales
• Pulley drive
• Higher model on requirement basis
• Material of construction – S.S. or M.S. or M.S. with S.S. lining as per customer choice
• S.S. vane type impeller with hard facing edges
• S.S. perforated screen plate

Installed adjacent to Hi-consistency pulper, the diluted pulp passed through a screen at 4% consistency.

Features

• High Consistency Pulper is suitable for slushing of all type of waste paper at consistancy range of 13-18% with minimum fines generation.
• It is a batch type pulper having very good difibration effect.
• Pulper is provided with a Dilution Pulper with screen plate for removal of non fibrous material, screen plate perforation depending upon the quality of Raw Material.
• Most effcient separation of fibre and Contaminants with breaking them up making their Subsequent removal easier.
• The Quality of disintegrated stock translates in to energy saving in terms by refining power.
• The low peripheral rotor speed promotes an energy transfer exclusively by friction without shocks nor shearing effect.

• Medium Consistency pulper for slushing of all type of waste paper and Machine Broke
• It is a continues type pulper having very good power efficiency.
• Pulper is provided with S.S. perforated screen plate hole diameter depending upon the quality of Raw Material.
• Pulper is available in all sizes suitable for requirement.
• Suitable Belt conveyor is supplied for feeding of the raw material (Optional).

Energy efficient agitators find application in all type of Pulp storage chests, including Hight Density Towers, Mixing Chest & Machine Chest.

The sturdy design incorporate Bearings & Glands. located outside, optimally designed adjustable propeller blades. all parts coming in contact with stock made of stainless Steel, the agitators are highly energy efficient and have the provision for adjusting the vane angle to suit specific process requirement of gentle or strong agitation. 

• Decker Thickener comprising of C.I. I S.S. Moulds and M.S. I S.S. Vat, are best suited for removal of excess water from stock.
• Sizes vary from 2.00 mtrs to 3.00 mtrs depending upon the process capacity.
• In put Consistency 1 % to out put consistency of 4 %
• Minimum fiber loss due to modified sealing arrangement.
• B2 Thickener for Thickening cum washing purpose.
• Constructed in S.S. 304 and S.S. 316 Material.
• Driven with Variable Speed drive for setting the drainage of different freeness of stock.