Screening Equipment

Screening Equipment

The function of the screening equipment is to minimize the amount of the impurities in the pulp suspension that do not meet the process requirements, so that clean good pulp can be sent to the next process directly.

There are many types of impurities in the pulp, and there are typically non-fibrous and fibrous impurities suspension such as sand, metal particles, ink, and the like which are mixed into the pulp from the outside and fiber bundles generated during the pulping process. if they are not removed before papermaking, these impurities can cause serious paper problems and even affect production.

One of the methods of removing impurities from the pulp is screening. That is, the pulp goes through screening equipment to achieve the purpose of removing impurities based on the differences in morphology between the impurities and the fibers.

The screening equipment works on the removing principle of coarse impurities, and has a screen plate with a round drum shape, a conical shape or a flat plate shape. The opening of the screen plate can processed into a hole shape (cylindrical, conical, etc.), or can be processed into a long slit shape. The holes or slits are of a moderate size to allow a single fiber to pass while blocking impurities on the surface of the screen. The good pulp flows through the screen holes by means of static position difference on both sides of screen plate and dynamic pressure head generated by the movement of the equipment itself, and the tail pulp or coarse slag blocked by the plate is discharged by axial thrust or gravity. The screen equipment must be equipped with a pulse generating mechanism to prevent screen holes from being blocked by coarse slag. The screen equipment can be divided into centrifugal screen, pressure screen and vibration screen according to different mechanisms.

AGICO can provide high quality screening equipments for clients.

screen equipment

At present, the medium-concentration screening equipment has been widely used in the screening process of mechanical pulp or chemical pulp. It is operated at a concentration of 7-15%. Medium-concentration screening is another important medium-concentration pulping operation technology after medium-concentration storage and transportation, bleaching, washing and the like. Using the principle of “fluidization” of pulp, the fibers and impurities are freely moved each other in the medium-concentration screening equipment, and the effective separation of fibers and impurities is completed under low-concentration conditions.

The effect of the screening equipment is mainly reflected in the separation of coarse slag and good pulp. This effect is usually evaluated in terms of the relationship between the separation achievement and the discharge amount of the tailings.

Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fiber crops, waste paper, or rags. Many kinds of paper are made from wood with nothing else mixed into them. This includes newspapers, magazines and even toilet paper. Pulp is one of the most abundant raw materials.

A pulp mill is a manufacturing facility that converts wood chips or other plant fibre source into a thick fibre board which can be shipped to a paper mill for further processing. Pulp can be manufactured using mechanical, semi-chemical or fully chemical methods (kraft and sulfite processes). The finished product may be either bleached or non-bleached, depending on the customer requirements.

A paper machine (or paper-making machine) is an industrial machine which is used in the pulp and paper industry to create paper in large quantities at high speed. Modern paper-making machines are based on the principles of the Fourdrinier Machine, which uses a moving woven mesh to create a continuous paper web by filtering out the fibres held in a paper stock and producing a continuously moving wet mat of fibre. This is dried in the machine to produce a strong paper web.

The pulp produced up to this point in the process can be bleached to produce a white paper product. The chemicals used to bleach pulp have been a source of environmental concern, and recently the pulp industry has been using alternatives to chlorine, such as chlorine dioxide, oxygen, ozone and hydrogen peroxide.

Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters. There, heat and chemicals break down lignin, which binds cellulose fibres together, without seriously degrading the cellulose fibres. Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics. The kraft process is the dominant chemical pulping method, with the sulfite process second. Historically soda pulping was the first successful chemical pulping method.