Wheat straw pulp black liquor alkali recovery method

Abstract

The invention discloses a wheat straw pulp black liquor alkali recovery method. The method includes the following steps that firstly, black liquor is evaporated and concentrated, and the concentration of the concentrated black liquor is 40-44% after evaporation; secondly, the concentrated black liquor obtained after evaporation is further evaporated and concentrated through tertiary air by means of a disk evaporator and then enters an alkali furnace to be pyrolysed and combusted, and finally green liquor is prepared in a dissolving tank; thirdly, the green liquor is processed in a causticizing department, the green liquor obtained in the second step and an excessive amount of ash are placed in a causticizing devuce, causticizing temperature is higher than 95 DEG C, and white liquor is obtained after filtration. According to the method, the technological process is simple, investment is small, and lignin is recycled while organic matter dyeing loads are reduced, wherein the concentration of the green liquor is 110-120 g / L, the amount of the excessive amount of ash is 3-5%, the causticizing degree is larger than 85%, the amount of white mud residual alkali is smaller than 2%, the dryness degree of white mud is larger than 50%, and the concentration of the white liquor is larger than 80g / L.

Description

technical field [0001] The invention relates to the field of alkali recovery of papermaking black liquor, in particular to a method for alkali recovery of wheat straw pulp black liquor. Background technique [0002] Environmental pollution caused by the paper industry has long troubled people. In papermaking wastewater, black liquor is the main source of pollution. The direct discharge of papermaking black liquor into rivers and oceans will cause eutrophication in local waters and destroy the original ecological balance. As a result, it has a notorious reputation for polluting the environment. The so-called papermaking black liquor is the alkaline black liquor left after extracting and separating the cellulose that can be used to make paper in plants. Papermaking black liquor is mainly composed of lignin and hemicellulose. These two components function similarly to cellulose, and together they support the plant's cell walls. However, lignin and hemicellulose are far les...

AI Technical Summary

Problems solved by technology

There are certain deficiencies in the existing recovery methods of papermaking black liquor: project investment and operating costs are high, and pulp mills with an annual output of more than 17,000 tons of pulp can realize meager profit operation; wheat straw black liquor has low calorific value, high viscosity, and silicon-containing If the amount is high, the alkali recovery cost is high, the alkali recovery rate is low, and the operation is difficult. The causticization, combustion and other processes still need to be improved, otherwise it will not work normally