CN1250123A - Black liquor treating and caustic soda recovering method for crop stalk pulping process - Google Patents

Abstract

Concentrated black liquor and dilute washed black liquor are treated separately with lime water. Caustic soda obtained in the treatment of concentrated black liquor is recovered for reuse. Dilute caustic soda solution after the treatment of dilute washed black liquor is fed into one other reactor to add Mn to the power 7 and Mn to the power reagent to reduce chemical oxygen demand before returning to pulp-making inverse washing step or being neutralized for drainage. Compared with available technology, the present invention is simple and effective and can save great amount of washing water.

Description

Crop stalk is made black liquor processing and caustic soda recovery method in the pulping process

The present invention relates to alkali paper-making black liquor and handle and the caustic soda recovery method, relate in particular to crop stalk and make black liquor processing and caustic soda recovery method in the pulping process.

Pulp and paper industry is one of main industries of current domestic serious pollution of water environment, the main cause that causes this situation is because China's forest scarcity, non-wood material is abundant, quite a few pulping and papermaking industry is raw material with the dogstail, and most of dogstail slurry papermaking enterprise small scales, equipment is simple, the material consumption height, blowdown flow rate is big, again almost without any pullution controlling measure, the overwhelming majority alkali and the in line water body of organic pollution (COD), particularly in Huaihe River, Haihe basin, the situation that a river is polluted in paper mill happens occasionally.National alkaline straw-pulp output surpassed 3,400,000 tons in 1997, and a year alkali charge reaches 1,000,000 tons.And reclaim alkali number only about 8000 tons, produce organic pollution (COD) nearly 4,500,000 tons.

Purpose of the present invention is exactly to make black liquor processing and caustic soda recovery method in the pulping process for the defective that overcomes above-mentioned prior art existence provides a kind of crop stalk simple, that save investment.

Purpose of the present invention can be achieved through the following technical solutions:

A kind of crop stalk is made black liquor processing and caustic soda recovery method in the pulping process, it is characterized in that, it comprises following two steps: the first step, the concentrated black liquid of slurrying is fed in the mixing channel, feeding milk of lime then mixes, this mixed liquor is fed in the sedimentation separation groove again and separate, the clarification alkali lye that the upper strata obtains is sent into reuse after the adjustment concentration in the alkali lye storage tank by liquid pump, and lime mud calcium silicates that lower floor produces and lignin precipitation send incinerating kiln to burn to reclaim calcium oxide; Second step, rare black liquor of washing straw pulp is fed mixing channel, feeding milk of lime then mixes, again this mixed liquor is fed in the sedimentation separation groove and separate, lime mud calcium silicates that lower floor produces and lignin precipitation send incinerating kiln to burn to reclaim calcium oxide with step 1 equally, the diluted alkaline clarified solution that the upper strata obtains is sent into by liquid pump and is removed in the aerobic substance reactor, adds Mn to reactor simultaneously ^{+ 7}, Mn ^{+ 6}Reagent is to reduce the chemical aerobic substance in the diluted alkaline clarified solution, and reacted sig water can return slurrying countercurrent washing operation, and reacted sediment is Mn ^{+ 4}, can further be oxidized to Mn ^{+ 7}, Mn ^{+ 6}The reagent reuse.

Compared with prior art, the present invention has the following advantages:

1. technology is simple, effect is obvious, crop stalk is different with timber, it contains more Si oxide, straw particularly, contain more silica, this material forms silicate in aqueous alkali, if black liquor adopts concentration mode in the past, sodium metasilicate can cause operational being the devil in Multi-effect Evaporation Processes.And the present invention utilizes the characteristic that contains more silicate in the straw pulp just, add an amount of milk of lime, silicate is combined with calcium ion, generate water-fast calcium silicates, this new life's calcium silicates particulate, have great specific surface and great adsorption capacity, macromolecular lignin is precipitated rapidly, black liquor is clarified fully.The liquid of this clarification has kept most caustic soda composition, can return in the pulping process after adjusting concentration and use.

2. can save a large amount of slurries, increase the chemical motive force of cleaning solution: the present invention is for rare black liquor that pulp washing produced, the method of taking to feed milk of lime equally makes the black liquor decolouring and clarifies, and resulting diluted alkaline clarified solution can return slurrying countercurrent washing system.This method is killing three birds with one stone, at first, can reduce slurry exponentially; The second, because of clarified solution has alkalescence, to surplus lignin and the leaching of silica, have stronger chemical motive force; The 3rd, improved the NaOH concentration of rare black liquor exponentially, remove lignin and silicate once handling with milk of lime again, can utilize its alkalescence preparation Mn ^{+ 7}, Mn ^{+ 6}Reagent and milk of lime etc., thus its economic worth improved.

3. can reduce chemical aerobic substance (COD), accomplish qualified discharge: the present invention adds " Mn in alkali lye ^{+ 7}, Mn ^{+ 6}Oxidant ", chemical pollutant is wherein further reduced, reach the COD index request, use CO again ₂Neutralization makes liquid be the discharging of neutral back.Perhaps be used for absorbing the acidic materials of flue gas, send the sewage-farm discharging then.

Accompanying drawing is a process chart of the present invention.

The invention will be further described below in conjunction with embodiment.

Embodiment:

Obtain concentrated black liquid and two kinds of samples of rare black liquor in the pulp production, the first step: respectively get above-mentioned style 8cc and be positioned in the graduated test tube, drip milk of lime respectively by certain paper plant to obtain water white transparency clear liquid (caustic soda) degree of being; Add milk of lime 4cc in the concentrated black liquid, observe after one hour, the about 2cc of the beds of precipitation that pine is floating adds milk of lime 2cc in rare black liquor, observe the about 1cc of the beds of precipitation that pine is floating after one hour.In second step, use suction pipe sucking-off supernatant liquid (alkali lye) respectively, with rare KM _nO ₄Drop is gone into, and becomes green by purple rapidly, slowly disappears then, and dripping quantity is with purple disappearance degree of being, after 4 hours, yellowish-brown precipitates (M _nO ₂) make a decision in the test tube bottom, the two consumption difference is not obvious, and precipitation illustrate that the high oxide with manganese can make COD up to standard, and consumption is few all as thin as a wafer.The 3rd step is with above-mentioned yellowish-brown sediment (M _nO ₂) insert in the nickel crucible with 2: 1 (weight ratio) with NaOH, add water a little, make the NaOH dissolving, with MnO ₂Transfer all, heating makes witheredly on low baking temperature, smashs to pieces and still is powder, reach about 400 ℃ in heating on the fire, stir with metal tube, and bubbling air, powder flowbility is very good, do not glue and be not stained with, after reaction in more than hour, slowly put cold, soluble in water, getting green solution is that sodium manganate generates, and it has had oxidisability, can use after demarcation.

Claims (1)

1. a crop stalk is made black liquor processing and caustic soda recovery method in the pulping process, it is characterized in that, it comprises following two steps: the first step, the concentrated black liquid of slurrying is fed in the mixing channel, feeding milk of lime then mixes, this mixed liquor is fed in the sedimentation separation groove again and separate, the alkali lye that the upper strata obtains is sent in the alkali lye storage tank and is reclaimed, and lime mud calcium silicates that lower floor produces and lignin precipitation send incinerating kiln to burn to reclaim calcium oxide; Second step, rare black liquor of washing straw pulp is fed mixing channel, feeding milk of lime then mixes, again this mixed liquor is fed in the sedimentation separation groove and separate, lime mud calcium silicates that lower floor produces and lignin precipitation send incinerating kiln to burn to reclaim calcium oxide with step 1 equally, the diluted alkaline clarified solution that the upper strata obtains feeds and removes in the aerobic substance reactor, adds Mn to reactor simultaneously ^{+ 7}, Mn ^{+ 6}Reagent is to reduce the chemical oxygen consumption thing in the diluted alkaline clarified solution, and reacted sig water can return slurrying countercurrent washing operation, and reacted sediment can further be oxidized to Mn ^{+ 7}, Mn ^{+ 6}The reagent reuse.