A black liquor crystallization evaporation process

Abstract

The invention discloses a black liquor crystallization evaporation process. The concentration of black liquor in the II effect of the black liquor evaporation station is 40% to 45% of the mass percentage, and the black liquor enters the first evaporator of the I effect multi-body evaporator and the alkali furnace The thick black liquor of soda ash and Glauber's salt is mixed, and at the same time, the concentration of black liquor during crystallization is adjusted by adjusting the amount of thick black liquor returned by the last evaporator of the I-effect multi-body evaporator. Through this process, the crystallization time can be flexibly adjusted and controlled. The concentration of the black liquor can prevent the inorganic salt from crystallizing on the heating plate of the evaporator when the crystal seed is lower than the crystallization point; at the same time, the thick black liquor storage tank is canceled, which is conducive to maintaining the maximum specific surface area of ​​the crystal seed, and the crystallization effect is greatly improved. ;The amount of black liquor used to carry soda ash, Glauber's salt and other crystal seeds can be greatly reduced, which saves energy consumption for transportation, reduces the cooling range of black liquor, is conducive to improving evaporation efficiency and saving steam consumption, and at the same time simplifies the process and reduces equipment investment.

Description

【Technical field】 [0001] The invention relates to a papermaking pulping black liquor evaporation and concentration process, in particular to a black liquor crystallization evaporation process. 【Background technique】 [0002] Black liquor is the waste liquor produced by alkaline pulping in the paper industry. At present, the mature technology for treating black liquor is the combustion method. The main principle is that the black liquor extracted after pulping is concentrated to more than 55% of the solid concentration by mass percentage through the evaporation process. , and then sent to the alkali furnace for combustion. In the alkali furnace, the organic matter in the black liquor is burned to release heat, and the sodium sulfate in the sodium salt is mostly reduced to sodium sulfide under high temperature and reducing conditions, and flows through the chute to be dissolved in a molten state with other inorganic salts such as sodium carbonate. Dissolve in water and dilute...

AI Technical Summary

Problems solved by technology

However, under high concentration conditions, inorganic salts are easy to scale on the heating plate. Once scaled, the evaporation capacity of the evaporation station will drop rapidly because the heat transfer coefficient of the scale layer is much lower than that of metal.

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