CN1070962C - No sewage discharge treatinent method for black liquor in paper making - Google Patents

Abstract

The present invention discloses a method for thoroughly treating black liquor without discharging sewage. The method of the present invention comprises: regulating the pH value of black liquor by sulfuric acid; heating the black liquor; precipitating lignin; adding basic oxide to filter liquor, and heating the filter liquor; removing solid sulfate; electrolyzing the filter liquor in an electrolytic tank which uses a cation exchange membrane as a diaphragm; obtaining sodium hydroxide solution in the cathode; evaporating, concentrating and drying anolyte so as to obtain solid sacchariferous mineral powder. In the method of the present invention, the sulfuric acid is used for acidizing and precipitating the lignin, the technology is simple and convenient, and environment pollution is reduced; sodium hydroxide is electrolytically recovered, and the sacchariferous mineral powder does not contain alkali; the sacchariferous mineral powder can be used as livestock feedstuff; effective ingredients in the black liquor are sufficiently recovered and utilized.

Description

A kind of black liquid without sewage discharge improvement method

The present invention relates to a kind of improvement method of paper waste-black liquor, particularly a kind of improvement method of straw pulp waste water-black liquor.

At present, the improvement method of paper waste-black liquor is a lot, and the wood pulp waste water that with timber is raw material papermaking is because of its calorific value height, mainly administers with firing method, but this method investment cost height, and being only applicable to large-scale is the paper mill of raw material with timber.For being the straw pulp waste water-black liquor of raw material papermaking, because of its calorific value is low, should not adopt firing method, and not find a kind of method of thorough improvement so far as yet with reed, straw, bamboo and straw etc.

The processing method that people such as the Sun Lian of Ecological Envionment Research Centre, Chinese Academy of Sciences behaviour once invented a kind of black liquid of straw pulp paper-making, the patent No. is 89106694.2, this method is earlier alkaline black liquor to be used SO 2 acidifying with the precipitation lignin, filter, then freezing, with the precipitation sodium sulfite, the isolated by filtration sodium sulfite, at last filtrate is evaporated, concentrate, spray drying obtains sugared breeze, and this method remains in many shortcomings: 1, use SO 2 acidifying, the cost height, because of sulfur dioxide is gas, operation is trouble, and more serious to equipment corrosion, is easy to simultaneously escape into and causes environmental pollution in the air.2, it is incomplete to separate sodium sulfite with freezing, still contains more sodium sulfite in the filtrate.3, resulting sugared breeze contains more salt, particularly sodium sulfite, is not suitable for doing animal feeding-stuffs such as ox, sheep.4, the sodium salt in the black liquor does not obtain reclaiming.5, accessory substance sodium sulfite purity is not high, and cost recovery is higher than sale price, and economic benefit is not high.6, the lignin of Hui Shouing contains silica impurity, and color is darker.

Afterwards, people such as Sun Liancao improved on above-mentioned patent basis, improved method be with the filtrate of precipitation behind the lignin with the calcium oxide causticization, filter removing the calcium sulfite precipitation, the filtrate evaporation, concentrate, spray drying obtains sugared breeze.Still there is following shortcoming in this method of having improved: 1, SO 2 acidifying cost height, and corrosive equipment, troublesome poeration escapes into easily and causes environmental pollution in the air simultaneously.2, in the sugared breeze because of containing NaOH, be alkalescence, can not do animal feeding-stuffs such as ox, sheep.3, NaOH in the black liquor and salt do not obtain reclaiming.4, the lignin of Hui Shouing contains silica impurity, and color is darker.

The purpose of this invention is to provide a kind of new method that can administer black liquor, this method easy operating, environmental pollution is little, and each effective ingredient can obtain recycling in the black liquor, after particularly NaOH reclaims, can be back in the paper-making pulping workshop section and re-uses.

For achieving the above object, the present invention by the following technical solutions, the method for administering black liquor comprises following operation:

(1) add the pH value that sulfuric acid is transferred black liquid, transfer pH value to 8-9 earlier, heated solution is when treating that temperature rises to 60-80 ℃, be incubated 1-4 hour, silicon-containing compound is filtered, removes in cooling, again the filtrate pH value is transferred to 2.5-4.5, at 60-80 ℃ of constant temperature 1-4 hour, filter the lignin precipitation;

(2) add basic anhydride in the filtrate, transfer pH value,,, filter, remove solid sulfate salt at 60-80 ℃ of constant temperature 1-4 hour with above-mentioned causticization liquid heating to 12-14;

(3) with the filtrate electrolysis, barrier film is a cation-exchange membrane, and filtrate is positioned at the anode chamber, and water level is in cathode chamber, and at time of staying 5-15 minute of cathode and anode chamber fluid, DC voltage 3-6 lied prostrate, and negative electrode gets sodium hydroxide solution;

(4) with anolyte evaporation, concentrate, drying obtains the sugar cube breeze.

The improvement method of described black liquid, its described causticization basic anhydride are calcium oxide.

Can be in this programme according to what of dioxide-containing silica in the raw black liquid, adopt corresponding operation, when dioxide-containing silica more for a long time, 3-10 grams per liter for example, can be when transferring the black liquor pH value with sulfuric acid, earlier black liquor PH is transferred to 8-9, and with the black liquor heating, to precipitate too much silicon-containing compound, thereby the purity of lignin product in the raising next step, and after removing silicon-containing compound, help next step electrolysis, avoid because of produce the anode poisoning that the precipitation of silica thing causes at anode.

Advantage of the present invention: adopt sulfuric acid acidation with the precipitation lignin, technology is simple, easy to operate, reduce environmental pollution, employing is made the electrolytic method of barrier film with cation-exchange membrane, the sodium hydroxid in the recyclable black liquor, thus reclaimed the effective ingredient in the black liquor, and do not contain alkali in the sugared breeze, can be used as animal feeding-stuff.

The invention will be further described below in conjunction with process flow diagram and embodiment:

Fig. 1: process flow diagram of the present invention

Among Fig. 1,1 for transferring pH value, and pH value is controlled between the 2.5-4.5,2 removes delignification after filtration, filtrate is through causticization 3, causticization can through filtering 4, be removed calcium sulfate with basic anhydride for example magnesia, calcium oxide etc., filtrate is through electrolysis 5, wherein anolyte obtains sugared breeze through evaporation, concentrated, drying 6, and catholyte returns slurrying workshop section.

Embodiment 1:

50 liters of alkaline black liquor are placed porcelain enamel barrel, one side stirs, one side slowly adds sulfuric acid, treat that the solution pH value reaches at 9 o'clock, stop to add acid, heated solution is when treating that temperature rises to 70 ℃, be incubated 2 hours, cooling is filtered, and removes silicon-containing compounds such as metasilicic acid, filtrate places porcelain enamel barrel, another stirring, one side adds acid (sulfuric acid concentration about 30%), treats that pH value reaches at 3.5 o'clock, stop to add acid, heated solution when treating that temperature is raised to 75 ℃, is incubated 4 hours, cooling, filter, reclaim lignin, filtrate is placed porcelain enamel barrel, one side stirs, one side adds the powdery calcium oxide, also can add basic anhydride such as magnesia, filters, reclaim sulfuric acid calcium, above-mentioned filtrate is fed cation-exchange membrane do in the anode chamber of electrolytic cell of barrier film, this cation-exchange membrane trade mark is: YM-3 type homogeneous phase cation exchange film, the specification of electrolytic cell are 800 * 400 * 60mm, cloudy, anode chamber's volume respectively is 7 liters, the negative electrode water flowing of electrolytic cell, sun, voltage is 6 volts between the negative electrode, at the moon, the time of staying 5-15 of anode chamber's fluid minute, in electrolytic process, the pH value of catholyte constantly raises, and reaches 14 very soon, and the anolyte pH value descends, cyclic electrolysis, when the pH value of anolyte reaches 4-5, stop electrolysis, catholyte is light yellow sodium hydroxide solution, concentration reaches 50 grams per liters, can return in slurrying workshop section.The anolyte heating evaporation, concentrate and dry (its process conditions are with identical in the past), obtain the sugar cube breeze, through fragmentation, pulverization process, obtain sugared breeze, this powder is brown, distinguishes the flavor of littlely sweetly to be with saltyly slightly, and the condensed water of evaporation can return slurrying workshop section.

Embodiment 2:

In the porcelain enamel barrel that fills alkaline black liquor, (dioxide-containing silica in the alkaline black liquor (3 grams per liter), stir on one side, slowly add sulfuric acid solution pH value transferred to 3.5 on one side, stop to add acid, heated solution, temperature is raised to 75 ℃, constant temperature 4 hours, cooling, filter and regain lignin, all the other steps are with embodiment 1.

Claims (2)

1, a kind of administration of papermaking black liquid method is characterized in that it comprises following operation:

(1) add the pH value that sulfuric acid is transferred black liquid, transfer pH value to 8-9 earlier, heated solution is when treating that temperature rises to 60-80 ℃, be incubated 1-4 hour, silicon-containing compound is filtered, removes in cooling, again the filtrate pH value is transferred to 2.5-4.5, at 60-80 ℃ of constant temperature 1-4 hour, filter the lignin precipitation;

(2) add basic anhydride in the filtrate, transfer pH value,,, filter, remove solid sulfate salt at 60-80 ℃ of constant temperature 1-4 hour with above-mentioned causticization liquid heating to 12-14;

(3) with the filtrate electrolysis, barrier film is a cation-exchange membrane, and filtrate is positioned at the anode chamber, and water level is in cathode chamber, and at time of staying 5-15 minute of cathode and anode chamber fluid, DC voltage 3-6 lied prostrate, and negative electrode gets sodium hydroxide solution;

(4) with anolyte evaporation, concentrate, drying obtains the sugar cube breeze.

2, by the described administration of papermaking black liquid method of claim 1, it is characterized in that described causticization basic anhydride are calcium oxide.

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