Process and equipment for improving concentration of straw pulping black liquor by alkali method

Abstract

The invention relates to a process and equipment for improving the concentration of straw pulping black liquor by an alkali method. The process is characterized by being arranged between a condensing procedure and a burning procedure of the conventional process for alkali recovery of straw pulp by the alkali method and comprising: (1) a step of heat treatment, in which the final pressure of the black liquor is 1.0 to 1.2MPa and the temperature is between 175 and 180 DEG C, so that the polymerized sugar in high molecular weight is decomposed; (2) a step of high-concentration vaporization, in which the final concentration of the black liquor is 55 to 65 percent; and (3) a step of pressurized heat storage, in which the equipment mainly comprises a pre-pressurizing pump, a preheater, a heat mixer, a final pressure pressurizing pump, a heat processor, a flash evaporator, a concentrated black liquor storage tank, A and B vaporization thickeners, E and F circulating / conveying pumps, and a final concentration black liquor pressure storage tank. The process and the equipment have the advantages that: the energy is saved and the energy consumption is reduced; the straw pulping black liquor is good in atomizing dispersibility, is easily burned and does not block an air inlet; the corrosion of the device is reduced; on a basis of the original straw pulp alkali recovery process, the process and the equipment are just added and the original process can be normally operated, so that the energy saving investment cost is lowered.

Description

technical field [0001] The invention relates to an alkaline straw pulp papermaking process, in particular to a process and equipment for increasing the concentration of the straw pulp black liquor through heat treatment, high-concentration evaporation and pressure heat storage of the alkaline straw pulp black liquor. Background technique [0002] In the papermaking industry, wood pulp or straw pulp is generally used for pulp. At present, straw pulp is mostly used in China, that is, grass such as wheat straw is used as raw material through alkaline pulping process; the main process is: firstly, wheat straw is mixed with caustic soda and steam Under the action of cooking and chemical reaction, organic matter such as lignin, polysaccharide carbohydrates and alkali lignin in wheat straw and caustic soda are dissolved in the cooking liquid to become black liquor, and the fibers in wheat straw are freed to become pulp; after separation and bleaching , the pulp is used to make pape...

AI Technical Summary

Problems solved by technology

In summary, how to increase the solid content of straw pulp black liquor, increase its concentration without increasing viscosity, so as to solve the existing problems of non-combustibility and low thermal efficiency of straw pulp black liquor, and make the treatment of straw pulp black liquor still possible Continuing to use traditional alkali recovery equipment has become a topic of concern in the industry

Images