PULP & PAPER INDUSTRY

BY:- ABHISHEK RAJPUT

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CONTENTS

• REQUIREMENTS• PROCESSES• WASTE GENERATION POINTS• CHARACTERISTICS OF W/W• TREATMENT SCHEMES• CHARACTERISTICS OF TREATED W/W• INNOVATIVE TECHNOLOGY Reff :- S. C. Bhatia

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REQUIREMENTS• Raw Materials-Conventional raw material are rice and wheat, straw, bagasse, jute, cotton rags, grasses, gunny, hessian, etc.

• Chemical Requirements- About 5-12% of NaOH is required per tonne of raw material. Lime is used as supplement to NaOH. Chlorine and calcium hypochlorite are bleaching chemicals. Sizing chemicals and

dyes are also used.19/03/2012 3

Raw materials used in paper industry.

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• Water Requirements- P and P industry’s existence lies on water supply. Constant water supply is required in all processes. Agricultural residue based industries require 200-350 cubic meter per tonne of paper made, however units using waste paper require 100-150 cubic meter per tonne of paper made.

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PROCESSESStep 1 Wood preparation The bark is removed from in-coming logs, and these are

then chipped. Sometimes, the wood arrives at the plant already chipped, meaning that this step is unnecessary.

Step 2 Cooking The wood chips are heated in a solution of NaOH and

Na2S in a pressure cooker, during which time a lot of the lignin is removed from the wood. The pressure is then released suddenly, causing the chips to fly apart into fibres.

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Step 3 Pulp washing The pulp is washed with water to wash out the

cooking chemicals and lignin from the fiber so that they will not interfere with later process steps. A good removal of chemicals

is necessary for several reasons:- * The dissolved chemicals interfere with the

downstream processing of the pulp.* The chemicals are expensive to replace.

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Step 4 Pulp screening Apart from fibres, the cooked pulp also contains partially

uncooked fibre bundles and knots. Modern cooking processes have good control over the delignification and produce less "rejects". Knots and shives are removed by passing the pulp over pulp screens equipped with fine holes or slots.

Step 5 Bleaching This is done in two stages. Firstly the pulp is treated with NaOH

in the presence of O2. The NaOH removes hydrogen ions from the lignin and then the O2 breaks down the polymer. Then, the pulp is treated with ClO2 then a mixture of NaOH, O2 and peroxide and finally with ClO2 again to remove the remaining lignin.

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Step 6 Paper making The fibers are mechanically treated to make them bond

better to each other, chemicals added to provide special properties such as color or water resistance, and then the water is squeezed out and the pulp is rolled smooth and dried.

Various ancillary processes result in the recovery of CaO, NaOH and Na2S, the major chemicals used in the process. Various utilities ensure that such conditions as sufficient reaction times and adequate mixing are met.

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WASTE GENARATION POINTS

• Sources of waste water- i) Black liquor* from cooking section. ii) Pulp wash water from pouchers. iii) Bleaching section. iv) Paper machine.

* Black liquor is the spent cooking liquor from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers.19/03/2012 11

CHARACTERISTICS OF WASTE WATER

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TREATMENT SCHEMES

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CHARACTERISTICS OF TREATED WASTE WATER

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INNOVATIVE TECHNOLOGY

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POLYMER INDUCED FLOCULATION

• Treatment of Pulp and Paper Mill Wastewater by Polyacrylamide (PAM) in Polymer Induced Flocculation.

• Cationic polyacrlyamide Organopol 5415 with very high molecular weight and low charge density is found to give the highest flocculation efficiency in the treatment of the paper mill wastewater.

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• It can achieve 95% of turbidity reduction, 98% of TSS removal, 93% of COD reduction and sludge volume index (SVI) of 14 ml g−1 at the optimum dosage of 5 mg l−1.

• Based on the cost evaluation, the use of the polyacrylamides is economically feasible to treat the pulp and paper mill wastewaters.

• Result suggests that single-polymer system can be used alone in the coagulation–flocculation process due to the efficiency of the polyacrylamide.

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• Sedimentation of the sludge by gravity thickening with settling time of 30 min is possible based on the settling characteristics of the sludge produced by Organopol 5415 that can achieve 91% water recovery and 99% TSS removal after 30 min settling.

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Bio-innovation

• Enzymes offer a simple solution for addressing lignin in effluent. Enzymes oxidize lignin and phenolic compounds to enable and promote separation from effluents and increase capacity.

• Moreover, enzymes can modify the residual lignin in unbleached pulp to improve the physical and mechanical properties of paper and board and the runability of the paper machine.

• Enzymes are a biodegradable alternative to petroleum-based and/or expensive strengthening agents and effluent management additives.

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Bio-innovation contd.

• The application of enzymes directly leads to better paper quality: While the brightness level goes up, the residual dirt level goes down. Saving on bleaching chemicals also means milder process conditions and an accentuated sustainable profile.(deinking)

• The enzymatic treatment can reduce the kappa number and increase pulp brightness when the same bleaching chemical charges are applied. It also allows savings in bleaching chemicals, while the final brightness of the paper is increased.(bleaching)

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THANK

YOU

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ANY QUERRIES??? ?

? ? ?19/03/2012

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