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Black liquor treatment method by lignin extraction and alkali recovery

A processing method and technology for black liquor, applied in the field of pulp and paper making, can solve the problems of large evaporation of thin black liquor, large concentration of thin black liquor, inability to recover lignin, etc., and achieve the effects of small investment and reduced energy consumption for evaporation

Active Publication Date: 2013-01-16
GUANGXI UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] Disadvantages of burning black liquor: (1) The concentration of dilute black liquor is large. For every ton of pulp produced, 7-9 tons of dilute black liquor will be produced.
At present, the combined application technology of black liquor gasification and gasification is still in the experimental stage. At the same time, black liquor gasification also has the disadvantages of large evaporation of dilute black liquor and inability to recover lignin in black liquor.

Method used

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  • Black liquor treatment method by lignin extraction and alkali recovery

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Effect test

Embodiment 1

[0045] Such as figure 1 , a black liquor treatment method of lignin extraction combined with alkali recovery, comprising the following steps:

[0046] a. Lignin extraction: extract and separate the slurry produced by cooking in the cooking pot 1 with the black liquor extractor 2 to obtain dilute black liquor and primary color pulp, and import the dilute black liquor with a weight percentage of 30% into the black liquor acidification pool 3. Adding sulfuric acid to adjust the pH value to 3, causing the lignin to precipitate, and filtering with a vacuum filter 4 to obtain the lignin and the acidic filtrate;

[0047] B. Acidic filtrate recycling: a part of the acidic filtrate is imported into the filtrate alkalization pool 5, and its flow rate is equal to the total flow rate of the dilute black liquor and sulfuric acid entering the black liquor acidification pool 3, and after adding alkali lye alkalization (pH is 9) Circularly add cooking pot 1 for cooking, add wood chips, wate...

Embodiment 2

[0055] Such as figure 1 , a black liquor treatment method of lignin extraction combined with alkali recovery, comprising the following steps:

[0056] a. Lignin extraction: extract and separate the slurry produced by cooking in the cooking pot 1 with the black liquor extractor 2 to obtain dilute black liquor and primary color pulp, and import the dilute black liquor with 50% by weight into the black liquor acidification pool 3. Add sulfuric acid to adjust the pH value to 4, precipitate the lignin, and filter it with a vacuum filter 4 to obtain lignin and acidic filtrate;

[0057] B. Acidic filtrate recycling: a part of the acidic filtrate is imported into the filtrate alkalization pool 5, and its flow rate is equal to the total flow rate of the dilute black liquor and sulfuric acid entering the black liquor acidification pool 3, and after adding alkali lye alkalization (pH is 8), circulatingly add cooking pot 1 for cooking, add wood chips, water, recycled lye and anthraquino...

Embodiment 3

[0065] Such as figure 1 , a black liquor treatment method of lignin extraction combined with alkali recovery, comprising the following steps:

[0066] a. Lignin extraction: the slurry produced by cooking in the cooking pot 1 is extracted and separated by the black liquor extractor 2 to obtain dilute black liquor and primary color pulp, and the dilute black liquor with a weight percentage of 40% is introduced into the black liquor acidification pool 3. Adding sulfuric acid to adjust the pH value to 2, causing lignin to precipitate out, and filtering with vacuum filter 4 to obtain lignin and acidic filtrate;

[0067] B. Acidic filtrate recycling: a part of the acidic filtrate is imported into the filtrate alkalization pool 5, and its flow rate is equal to the total flow rate of the dilute black liquor and sulfuric acid entering the black liquor acidification pool 3, and after adding alkali lye alkalization (pH is 10), circulatingly add cooking pot 1 for cooking, add wood chips...

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Abstract

The invention discloses a black liquor treatment method by lignin extraction and alkali recovery. The black liquor treatment method by lignin extraction and alkali recovery includes the steps of extracting lignin, recycling acid filtrate, evaporating and concentrating dilute black liquor, recovering heat, oxidizing alkali fusant, preparing sulfuric acid, dissolving oxidation residue of the alkali fusant, and alkalifying green liquor. The dilute black liquor generated in digestion includes two parts. 30-50% of the dilute black liquor by weight percent is subjected to lignin extraction. Part of the acid filtrate generated in lignin extraction and separation is used for acidifying the dilute black liquor, and the other part of the acid filtrate is used as digestion liquor. 50-70% of the dilute black liquor, by weight percent, is delivered to an evaporator for concentration, and concentrate is sprayed into a soda recovery furnace for combustion, and alkali substances and heat are recovered. By the black liquor treatment method, 30%-50% of lignin and 80%-90% of alkali substances in the black liquor can be recovered, evaporation of the dilute black liquor can be reduced by 30%-50%, and sulfuric acid is generated in a system and is recycled. Based on the existing equipment and techniques of pulp mills, input in process modification is low.

Description

technical field [0001] The invention belongs to the technical field of pulping and papermaking, and relates to papermaking sewage treatment, in particular to a black liquor treatment method of lignin extraction combined with alkali recovery. Background technique [0002] Pulping black liquor is viscous liquor produced by chemical pulping process. Black liquor contains a large amount of organic matter, the organic matter included is mainly alkali lignin, and also includes sodium hexa(or pentanoate), sodium acetate and sodium formate. , corresponding to different concentrations of black liquor, the total amount of COD (chemical oxygen demand, definition: the mass of oxygen element required for the complete oxidation of substances contained in a unit volume of wastewater) reaches 38400-1426000mg -l , is a potential source of water pollution, and any discharge will cause serious pollution. At the same time, the calorific value of black liquor solids is 1.4-1.6MJ / kg, which is a ...

Claims

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Application Information

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IPC IPC(8): D21C11/04D21C5/00
CPCY02P70/10
Inventor 农光再鲁炳辰李世强
Owner GUANGXI UNIV
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