Process for acidizing and recycling lignin by using pulping black liquid

A technology of pulping black liquor and lignin, which is applied in the technical field of using pulping black liquor to acidify and recover lignin, which can solve the problems of unqualified discharge of wastewater, low pH value of wastewater, and high suspended solids, so as to achieve low and low suspended solids Waste liquid volume, low COD effect

Active Publication Date: 2011-09-14
TIGER FOREST & PAPER GROUP +1
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Problems solved by technology

After these two methods produce lignin, the pH value of the wastewater is low, the suspended so...
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Abstract

The invention discloses a process for acidizing and recycling lignin by using pulping black liquid. The process is characterized by comprising the following steps of: 1, filling 60 to 80 percent of black liquor until the black liquor is half the volume of a reaction kettle, slowly adding 30 to 40 percent of sulfuric acid solution, and simultaneously starting a stirrer; 2, when the pH value of the final point of the reaction mixture is 3.0 to 5.0, stopping adding sulfuric acid, and then continuously stirring for 5 minutes, wherein the adding of the sulfuric acid is finished in 20 minutes, and the stirring speed of the stirrer is high and then low; 3, after reaction, pumping the reaction mixture into a hot blast stove when the reaction mixture is still hot and drying at the temperature of 140 DEG C; and when the moisture content of the lignin is less than or equal to 5 percent, stopping drying and bagging the lignin; and 4, feeding tail gas produced in a drying process into a soda recovery furnace and combusting. The lignin particles produced by the process are uniform, the waste liquid amount is greatly reduced, and waste water produced after the production of the lignin is neutral and has low content of suspended matter, and low chemical oxygen demand (COD), and can be discharged under the standard.

Technology Topic

Exhaust gasHot blast +7

Examples

  • Experimental program(1)

Example Embodiment

[0013] The present invention will be further explained below in conjunction with specific examples:
[0014] The example of the present invention adopts the following process:
[0015] 1. Acidification of thick black liquor:
[0016] Use a pump to add a certain amount of concentrated black liquor with a concentration of 60-80% to the reactor. When the amount of black liquor is half the volume of the reactor, stop adding the black liquor. Then slowly add 30-40% sulfuric acid solution to the black liquor, and while adding the sulfuric acid solution, turn on the agitator. When the pH value of the reaction mixture in the reaction kettle is in the range of 3-5, stop adding the sulfuric acid solution, and then Continue to stir for 5 minutes, that is, the entire acidification process is completed; the addition of sulfuric acid needs to be added slowly and completed within 20 minutes; the stirring speed is slow at the beginning and then fast, the stirring speed is 500 rpm for the first 15 minutes, and the next 10 minutes The stirring speed is 800-1000 rpm.
[0017] 2. Drying:
[0018] The reacted mixture is pumped to a hot air furnace, and atomized into fine mist particles through a nozzle, and dried to a moisture content of less than 5% through a hot air drying furnace. The hot air source of the hot air drying furnace is the primary and secondary air of the alkali recovery furnace. , The wind temperature is 145±5℃.
[0019] 3. Exhaust combustion of hot air drying furnace
[0020] The tail gas produced when the reacted mixture is dried in a hot air drying furnace includes water vapor, hydrogen sulfide, sulfur dioxide and other gases. These gases are collected by a gas hood and an induced draft fan, enter the odor system of the alkali recovery furnace, and separate water through a mist separator After the steam, the sulfur-containing gas enters the secondary and tertiary air of the alkali furnace for combustion as a combustion-supporting gas.

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