Jinling Machinery analyzes the conditions and solutions of paper machine foam

　　As mentioned in the previous degassing course, when the slurry contains more free air and more surface active substances, stable bubbles are easily formed, which float on the surface of the slurry to form bubbles.

　　The foam overflows when it is severe, causing trouble to the operation. Foam floats on the surface of the container and stays for a long time, which will cause slurries.

　　When the liquid level fluctuates, the floating layer ruptures and becomes a sludge mass that flows down, causing holes in the paper sheet, and even sticking and pressing. When it is not too serious, foam spots or pinholes will be formed when the bubbles are eliminated due to suction at the vacuum box. Therefore, the foam problem often becomes a problem of scratching the head in the wet end operation.

　　1) Conditions for foam generation

　　In addition to the aforementioned problem of air in the slurry, the severity of the foam problem often depends on the amount of surface active substances in the slurry.

　　Many substances in plant fiber raw materials, such as lignin, polysaccharides, resins, a small amount of fat, protein, phenolic substances and pectin, etc., become surface active substances and remain in the pulp after cooking and bleaching. In addition, the rosin gum added in the sizing process, in which sodium rosinate is also a surface active substance, the starch and animal glue used in the surface sizing agent, will also return to the paper machine system with the damaged paper. The increase in the content of these substances in the slurry will easily produce foam.

　　generally have the following reasons:

　　A) The pulp in the pulping part is not cleanly washed, or the bleached pulp is not cleanly washed, and the residual chlorine is high. At this time, a large amount of surface active substances remain in the pulp, which causes the paper machine feeding system to produce foam.

　　b) The amount of sizing is large, so that the slurry contains more rosin acid salts, or the pH value of the slurry is high, so that the sizing material does not settle on the fiber well, and exists in the slurry in the form of rosin acid soap At times, it will lead to an increase in bubbles.

　　2) Solution

　　As mentioned in the section on degassing, degassing can be used to reduce the air in the slurry, thereby reducing foam; or try to avoid mixing air in the slurry. For the increase in foam caused by the above reasons, it can be solved accordingly, that is, strengthen the slurry washing in the pulping workshop; minimize the foaming substances contained in the incoming pulp.