Causes of Foaming in the Pulp and Paper Industry

Since the beginning of the 21st century, with the improvement of people's quality of life and the speed of paper machines, people's requirements for paper quality have continued to increase. Among them, foam is an inconvenient thing in the pulp and paper industry. The operation of the pulping unit discharged from the steam ball has been the coating process (washing, filtering pulp, drifting, dewatering, papermaking, sizing, coating, etc.), and there are different levels of foam. It hinders the execution of process conditions and the normal operation of the equipment, and may become a serious problem in manufacturing papermaking and waste liquid treatment. Therefore, how to effectively control foam in the production process has long been valued by producers.

The formation and danger of foam
In papermaking systems, the gas is usually air or carbon dioxide, and the liquid medium is usually water. In the papermaking process, many operations cause the process water and white water to be mixed with air to form foam. For example, the slurry falls like a waterfall, the air of the slurry pump leaks, the agitator of the slurry tank is too strong or the agitator is exposed to the liquid surface, the pressure of the slagging outlet of the conical slag remover is too low, and the design of the white water or slurry pipeline is not reasonable. Recycling of white water, recycling of damaged paper, etc .; fermentation of pulp and acidification of carbonates will release carbon dioxide and form foam.
The air bubbles in the pulp have an important effect on the operation of the paper machine and the quality of the paper. The high content of air bubbles not only affects the dewatering of the mesh and causes paper disease, but also causes cavitation of air bubbles, which reduces the operating performance of the pulp pump and increases energy consumption; makes the entire sizing system unstable, and even causes the sizing pump to trip and stop; at the same time, Pressures in pulp tubes and other pressure devices also fluctuate. The air bubbles in the pulp do not affect the low speed paper machine very much, but have a significant impact on the high speed paper machine. Therefore, high-speed paper machines must be equipped with a complete defoaming system.
In the process of waste liquid treatment, foam reduces the efficiency of waste liquid treatment, and causes waste water to run off, splash, and pollute the environment. For example, when activated sludge surface accelerated aeration process is used for sewage treatment, a large amount of foam covers the surface during the aeration and oxygenation process. Aeration is not possible. There are two ways to eliminate foam in the paper industry, one is by chemical defoaming, and the other is mechanical defoaming. Chemical defoaming does not require a large amount of equipment investment and maintenance costs, and does not need to change the original process, so it is widely used.