Plate-type down-film evaporator descaling method

Abstract

A descaling method for plate-type falling-film evaporators is provided, which belongs to the technology field of pulp and paper industry. The method includes the following steps: immersing a heat exchange plate of a plate-type falling-film evaporator in a white liquor containing 70-90 g / L of NaOH, boiling under such conditions that the temperature is 110-130 DEG C and the pressure is 0.1-0.15 MPa until the fiber scale is loose; and purging the fibrous scale from the surface of the heat exchange plate by using a high-pressure water gun at a pressure of 400-500 Kg / cm<2>. The method can remove fiber scale efficiently and completely. Compared with the prior art, the method lengthens the descaling period from one month to three months, shorten the descaling time by a half, removes the scale completely, increases the efficiency of the plate-type falling-film evaporator and improves the production capacity of the equipment.

Description

technical field [0001] The invention relates to a descaling method for a plate type falling film evaporator in the pulp and paper industry, in particular to a method for removing fiber scale on the surface of a heat exchange plate in the plate type falling film evaporator. Background technique [0002] At present, in the alkaline pulping and papermaking industry, the combustion method is generally used to recover the alkali in the black liquor produced in the pulping process to solve its environmental pollution problem, and the plate falling film evaporator is the main method for the evaporation and concentration of black liquor. However, due to the problem of a certain amount of fiber in the black liquor itself, the plate type falling film evaporator usually runs for about a month, and the surface of the heat exchange plate is relatively serious with fiber scale, and it is very hard and firm, so that it cannot achieve normal heat exchange. effect, which seriously affects th...

AI Technical Summary

Problems solved by technology

[0002] At present, in the alkaline pulping and papermaking industry, the combustion method is generally used to recover the alkali in the black liquor produced in the pulping process to solve its environmental pollution problem, and the plate falling film evaporator is the main method for the evaporation and concentration of black liquor. However, due to the problem of a certain amount of fiber in the black liquor itself, the plate type falling film evaporator usually runs for about a month, and the surface of the heat exchange plate is relatively serious with fiber scale, and it is very hard and firm, so that it cannot achieve normal heat exchange. effect, which seriously affects the evaporation efficiency. After the above problems occur, it is usually treated by washing with water, directly using a high-pressure water gun or pickling.

[0003] In the above treatment methods, washing with water and directly using high-pressure water guns not only takes a long time to stop, but also cannot effectively remove the fiber scale on the surface of the heat exchange plate, and will also lead to continuous accumulation of scale, resulting in the actual production capacity of the plate falling film evaporator. Gradually reduce, using pickling method to remove the fibrous scale on the surface of the heat exchange plate, not only requires high technical content, but also requires a professional descaling team, and the equipment of the plate falling film evaporator itself is seriously corroded, causing equipment damage