CN1059482C

CN1059482C - Alkali process for treating black liquor

Info

Publication number: CN1059482C
Application number: CN96109733A
Authority: CN
Inventors: 葛道才; 迟仁清; 刘友会
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-09-10
Filing date: 1996-09-10
Publication date: 2000-12-13
Anticipated expiration: 2016-09-10
Also published as: CN1153843A

Abstract

The present invention relates to a method for treating alkaline pulp black liquor, which comprises the steps that the pH value of the black liquor is regulated from 2.5 to 4.5, the black liquor is heated and retains a constant temperature, precipitated lignin is filtered and removed, the filter liquor is transmitted to a middle chamber of a double-membrane three-chamber electrolysis bath composed of an anion exchange membrane and a cation exchange membrane for cyclic electrolysis, the DC voltage is from 3 volts to 6 volts, the distance between the anion membrane and the cation membrane is from 20mm to 50mm, the pH value of xylose mine liquor of the middle chamber of the electrolysis bath is regulated, and xylose mine powder is obtained by evaporation, concentration and drying. The method adopts sulfuric acid to acidify and deposit the lignin, and has the advantages of simple technology and environmental pollution reduction. The black liquor is electrolyzed in a double-membrane three-chamber mode, active substances in the black liquor are sufficiently recovered, the quality of the xylose mine powder is greatly increased, and the treating effect is good.

Description

A kind of improvement method of soda pulping black liquor

The present invention relates to a kind of improvement method of improvement method, particularly a kind of alkaline straw-pulp black liquid of soda pulping black liquor.

At present, a lot of about the improvement method of black paper-making liquid of alkali pulping, be used for the pulp black liquor that timber is pulping raw material, because of the calorific value height, can adopt firing method to handle, but this method investment cost height, be only applicable to large-scale pulping and paper-making factory.For with reed, straw, bamboo and straw etc. are the processing of the straw pulp black liquor of raw material, though some open reports are arranged, but it is all undesirable, for example 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, in the filtrate, still contains more sodium sulfite.3, resulting sugared breeze contains more salt, particularly sodium sulfite and 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, 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 inventor of present patent application not long ago applied for the improvement method of relevant black liquor, application number CN96109531.8.The more existing straw pulp of said method improvement method advanced person, not only reduce environmental pollution, and without sewage discharge, technology is state-of-the-art in the improvement method of present alkaline straw-pulp black liquid, but this method remains in following shortcoming: the filtrate system in (1) this method after the acidifying is precipitated with calcium oxide, the sediment that obtains-crystal of calcium sulfate particle is very thin, and the rate of filtration is slow, influences the processing speed of next process.(2) owing to be single anode membrane electrolytic tank electrolysis, causticization liquid places the anode chamber, and cathode chamber is a water, along with the carrying out of electrolysis, most of sodium ion enters cathode chamber, at this moment, sulfate ion is not removed in the anolyte (sugared ore deposit liquid), so last concentrating in the sugared breeze that obtains still contained a small amount of sodium sulphate.Therefore, be necessary to provide the improvement method of the more advanced soda pulping black liquor of a kind of technology.

The improvement method that the purpose of this invention is to provide a kind of soda pulping black liquor, this method technology is easy, reduces environmental pollution, and regulation effect is good, and speed is fast, and active ingredient is fully reclaimed in the waste liquid, and particularly the quality of sugared breeze improves greatly.

For achieving the above object, the present invention by the following technical solutions: the improvement method may further comprise the steps: (1) regulates the pH value of black liquid between the 2.5-4.5, is heated to 60-98 ℃, constant temperature 0.5-4 hour, filter, remove the lignin of precipitation; (2) will transfer the filtrate of pH value to send into the medial compartment electrolysis of the electrolyzer with dual membranes and three chambers of forming by the yin, yang amberplex, the chamber water flowing of the positive and negative utmost point, the electrolysis direct current Control of Voltage lies prostrate at 3-6, electrolyte time of staying in electrolytic cell is 5-15 minute and carries out cyclic electrolysis, and the intermembranous distance of yin, yang is between 20-50mm; (3) pH value of transferring medial compartment sugar ore deposit liquid is to 4-7, obtains sugared breeze through evaporation, concentrated, drying again.

The operation of above-mentioned accent medial compartment sugar ore deposit liquid pH value also can be placed on and enter before the electrolytic cell, be after black liquor is removed the lignin of precipitation, in filtrate, add NaOH, the pH value of regulating filtrate is between the 4-7, and the medial compartment electrolysis accent pH value purpose of then filtrate being sent into electrolytic cell is to make the favourable livestock of pH value of final sugared breeze product edible.

When dioxide-containing silica in the black liquor during greater than 3 grams per liters, the pH value of alkali paper-making black liquor can be transferred to 8-9 earlier, and be heated to 60-80 ℃, constant temperature 1-4 hour,, transfer pH value to 2.5-4.5 again with sulfuric acid filtrate more subsequently to remove silicon-containing compound in the black liquor.

In precipitation silicon-containing compound or lignin operation, temperature is got high value and the longer precipitation that helps of time, generally is controlled in the above-mentioned scope to get final product.

In electrolysis, DC voltage is controlled between the 3-6 volt, and voltage is low, and energy consumption is little, and the time is long; The voltage height, the time is short, and energy consumption is big.For example DC voltage 3.5-4 lies prostrate, the about 2300-2700 degree of energy consumption/1 ton of solid caustic soda, and during 6 volts of voltages, the about 3000-3500 degree of energy consumption/1 ton of solid caustic soda, the overstand of electrolyte in electrolytic cell, treating capacity is little, generally is controlled at 5-15 minute (during cyclic electrolysis, electrolyte flow rate is to determine in 5-15 minute with the time of staying in electrolytic cell); Generally control between the 20-50mm as for the intermembranous distance of yin, yang, distance is little, and energy consumption is little, but the table of equipment number increases relatively.

The invention will be further described below in conjunction with drawings and Examples

Fig. 1: the present invention administers the process frame chart of method

Among Fig. 1, take alkaline papermaking black liquor as raw material 1, raw material transfers pH value to 2.5-through acidifying 2 4.5, be heated to 60-98 ℃, and constant temperature 0.5-4 hour, after filtration 3, lignin is heavy Remove in the shallow lake, and filtrate enters electrowinning process 4, and this electrolytic cell is for making two films of barrier film with the positive and negative amberplex Three Room electrolytic cells, above-mentioned filtrate places the medial compartment of electrolyzer with dual membranes and three chambers, and water is respectively put by anode chamber, anode chamber, Under the DC electric field effect, sodium ion moves and generates to cathode chamber by cation-exchange membrane in the medial compartment liquid NaOH, sulfate ion moves and generates sulfuric acid by anion-exchange membrane anode chamber, the electrolyte warp Cyclic electrolysis after the NaOH for the treatment of cathode chamber reaches finite concentration, turns back to slurrying workshop section, the anode chamber Sulfuric acid reaches the lignin that returns behind the finite concentration for the precipitation black liquor, medial compartment sugar ore deposit liquid to transfer pH value, Evaporation, concentrated, spray-drying operation 5 obtain sugared breeze.

Advantage of the present invention: precipitate lignin with sulfuric acid acidation, technology is simple, easy to operate; Adopt yin, yang The dual membranes and three chambers electrolysis of amberplex can be reclaimed NaOH and sulfuric acid simultaneously, and utility all obtains reclaiming, And the quality of sugared breeze improves greatly, wherein only contains the sodium salt of trace, and whole service speed is fast, administer effect Fruit is good.

Embodiment 1:

50 liters of alkaline black liquor are placed porcelain enamel barrel (the black liquor dioxide-containing silica is greater than 3 grams per liters), and one side stirs, and one side slowly adds sulfuric acid, treats that 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, silicon-containing compounds such as metasilicic acid are removed in cooling, filtration.Filtrate places porcelain enamel barrel, another stirring, and one side adds sulfuric acid, transfers pH value to reach at 3.5 o'clock, heated solution to 70 ℃, constant temperature 1 hour, filters, reclaims lignin at cooling.Then filtrate is placed porcelain enamel barrel, one side stirs, one side adds 50 grams per liter sodium hydroxide solutions makes PH reach 5-6, filtrate is fed the medial compartment of the electrolyzer with dual membranes and three chambers of forming by IM-2 type homogeneous-phase anion exchange film and YM-3 type homogeneous phase cation exchange film, cloudy, cyclic electrolysis is carried out in anode chamber's water flowing, and the time of staying that the flow velocity of feeding filtrate is controlled in the electrolytic cell is 5 minutes, add DC voltage to 6 volt, at this moment, the PH of catholyte constantly raises, and reaches 14 very soon, the PH of anolyte reduces, reach 1 very soon, the pH value of medial compartment liquid remains unchanged, and catholyte is a sodium hydroxide solution, behind the cyclic electrolysis, when its concentration reaches 50 grams per liters, can return to be used for slurrying workshop section, anolyte is a sulfuric acid, when concentration reaches 60 grams per liters, return the lignin that is used for precipitating black liquor.

With the pH value after the electrolysis is that the medial compartment sugar ore deposit liquid of 5-6 carries out heating evaporation, concentrates and dry, obtains the sugar cube breeze, broken, be ground into powder, obtain sugared breeze and be brown, it is sweet to distinguish the flavor of, and evaporates the condensed water colorless and odorless of gained, can return to be used for slurrying workshop section and to make anode, negative electrode water.In the present embodiment, the energy consumption of electrolysis is/1 ton of solid caustic soda of 3500 degree.

Embodiment 2

With 50 liters of alkaline black liquor (containing silica volume) less than 3 grams per liters, place porcelain enamel barrel, slowly add, sulfuric acid to pH value is 3.5, heated solution to 70 ℃, constant temperature 1 hour, filters, reclaims lignin at cooling, following steps are with embodiment 1, wherein during cyclic electrolysis, feeding the time of staying that the flow velocity of filtrate (electrolyte) is controlled in the electrolytic cell is 15 minutes, and DC voltage is 4 volts, energy consumption under this electrolytic condition is/1 ton of solid caustic soda of 2500 degree

Embodiment 3

The operation that reclaims lignin in the present embodiment is identical with embodiment 2, but the filtrate behind the recovery lignin directly enters electrolyzer with dual membranes and three chambers, medial compartment sugar ore deposit liquid after the electrolysis makes to transfer pH value earlier, and pH value is controlled between the 4-7, carry out evaporation and concentration, drying process subsequently, obtain the sugar cube breeze, through broken, be ground into powder, obtain sugared breeze and be brown, it is sweet to distinguish the flavor of.

In the aforesaid operations, the evaporation of sugared ore deposit liquid, concentrated, the dry or same conventional method of spray-dired process conditions.

Claims

1, a kind of improvement method of soda pulping black liquor is characterized in that it may further comprise the steps:

(1) pH value of regulating black liquid is heated to 60-98 ℃ between the 2.5-4.5, constant temperature 0.5-4 hour, removes by filter the lignin of precipitation;

(2) filtrate is sent into the medial compartment electrolysis of the electrolyzer with dual membranes and three chambers of forming by the yin, yang amberplex, the chamber water flowing of the positive and negative utmost point, decomposition voltage are controlled at the 3-6 volt, and electrolyte time of staying in electrolytic cell is 5-15 minute, carry out cyclic electrolysis, the intermembranous distance of yin, yang is between 20-50mm;

(3) pH value of transferring medial compartment liquid evaporates behind the 4-7 again, concentrates, drying obtains sugared breeze.

2, the improvement method of soda pulping black liquor according to claim 1, it is characterized in that removing by filter the filtrate of the lignin of precipitation, before advancing electrolytic cell, regulate the pH value of filtrate between the 4-7 with NaOH earlier, send into the medial compartment of electrolytic cell subsequently again, the medial compartment sugar ore deposit liquid after the electrolysis is directly delivered to evaporation, concentrated, drying process.

3, the improvement method of soda pulping black liquor according to claim 1, the pH value that it is characterized in that described black liquid transfers to 8-9 earlier, is heated to 60-80 ℃, constant temperature 1-4 hour, to remove silicon-containing compound in the black liquor, transfer pH value to 2.5-4.5 again with sulfuric acid filtrate more subsequently.