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Paper making pulping black liquid crystallization and evaporation method

A technology for pulping black liquor and black liquor in papermaking, which is applied in the direction of concentrating waste liquid and the like, can solve the problem of inability to effectively avoid the scaling of evaporators, and achieves improved utilization efficiency and economic benefits, increased steam production, and improved thenardite reduction rate. Effect

Inactive Publication Date: 2010-09-15
YUEYANG FOREST & PAPER CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

With the method disclosed in this patent application, when the concentration of the pulping black liquor from the II-effect evaporator reaches about 50wt%, the black liquor is transported out, which will limit the increase of the final black liquor concentration. The amount of soda ash produced by the boiler may not be enough to form enough crystallization nuclei during the black liquor evaporation process, which cannot effectively prevent the evaporator from fouling

Method used

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  • Paper making pulping black liquid crystallization and evaporation method
  • Paper making pulping black liquid crystallization and evaporation method

Examples

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Effect test

Embodiment 1

[0030] In the evaporation process of six-effect plate falling film evaporation plus crystallization evaporation, the black liquor with a solid content concentration of 60wt% from the I-effect evaporator is flashed by the black liquor flash tank and then sent to the black liquor mixing tank. For the calculation of the total amount of black liquor solids in the black liquor mixing tank, add 7wt% of the soda ash collected from the alkali recovery boiler, and mix it with the black liquor evenly to generate mixed black liquor. At this time, the mixed black liquor becomes a supersaturated liquid and produces Crystal precipitation, using the crystal particles as crystal nuclei, so that more crystallization can be carried out on the crystal nuclei, preventing effective crystallization on the heating surface of the evaporator during the subsequent evaporation process, thereby effectively preventing scaling on the heating surface of the evaporator to maintain heat transfer Surface cleani...

Embodiment 2

[0032] In the evaporation process of six-effect plate falling film evaporation plus crystallization evaporation, the black liquor with a solid content concentration of 65wt% is discharged from the I-effect evaporator, and is sent to the black liquor mixing tank after being flashed by the black liquor flash tank. In the black liquor mixing tank, the total amount of black liquor solids is calculated, adding 8wt% of Glauber's salt collected from the alkali recovery alkali furnace, and mixing with the black liquor evenly to generate mixed black liquor. At this time, the mixed black liquor becomes a supersaturated liquid and produces Crystal precipitation, using the crystal particles as crystal nuclei, so that more crystallization can be carried out on the crystal nuclei, preventing effective crystallization on the heating surface of the evaporator during the subsequent evaporation process, thereby effectively preventing scaling on the heating surface of the evaporator to maintain he...

Embodiment 3

[0034] In the evaporation process of six-effect plate falling film evaporation plus crystallization evaporation, the black liquor with a solid content concentration of 58wt% from the I-effect evaporator is flashed by the black liquor flash tank and then sent to the black liquor mixing tank. To calculate the total amount of black liquor solids in the black liquor mixing tank, add 2wt% of soda ash and 2wt% Glauber's salt from the alkali recovery boiler, and mix with the black liquor evenly to generate mixed black liquor. At this time, the mixed black liquor becomes over Saturate the liquid, and produce crystal precipitation, use the crystal particles as crystal nuclei, make more crystallization proceed on the crystal nuclei, prevent the heating surface of the evaporator from crystallization during the subsequent evaporation process, and effectively prevent scaling on the heating surface of the evaporator , to keep the heat transfer surface clean; get the mixed black liquor mixed ...

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Abstract

The invention relates to a paper making pulping black liquid crystallization and evaporation method which comprises the following steps of: sending a black liquid from a first effect evaporator into a black liquid mixing tank, adding alkali ash and / or mirabilite, mixing with the black liquid to generate a mixed black liquid, and enabling the mixed black liquid to contain excess sulfate to become a sulfate supersaturated liquid; sending one part of the obtained mixed black liquid to a crystallization and densification evaporator for evaporation, and sending the evaporated black liquid to a pressure black liquid tank for storage; mixing one part of the black liquid with the black liquid from a second effect evaporator to sequentially enter three chambers of the first effect evaporator for evaporation, and sending into the black liquid mixing tank after evaporation. The invention can effectively avoid the scale formation of the black liquid in the evaporation process, obtains higher concentration of the black liquid, is beneficial to alkali reclamation and has lower energy consumption.

Description

technical field [0001] The invention relates to a method for evaporating papermaking pulping black liquor, in particular to a method for evaporating high-concentration black liquor. Background technique [0002] The current alkali recovery process in the paper industry mostly adopts the combustion method, which is roughly divided into five sections: extraction, evaporation, combustion, causticization and lime recovery. Black liquor evaporation is very important, which is directly related to the production efficiency and energy utilization of alkali recovery. efficiency. The composition of black liquor is more complex, and can be roughly divided into two parts, organic matter and inorganic matter. The composition and proportion of the two parts vary with the pulping raw materials and production process conditions. Among them, organic matter accounts for about two thirds, and inorganic matter accounts for about two thirds. Accounting for one third, the organic matter mainly c...

Claims

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Application Information

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IPC IPC(8): D21C11/10
Inventor 李正国万全满胡先知潘贞叶张彦军朱如意王玲东龙会刚
Owner YUEYANG FOREST & PAPER CO LTD
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