What is The Pulp Mill Machine?

paper pulping machine

What is the pulp mill machine? The pulp mill machine (also called paper pulping machine, or paper pulp making machine) refers to the required equipment for separating plant materials into fiber. There are three main paper pulping processes like chemical pulping, mechanical pulping and chemi-mechanical pulping. Relative paper pulp mills include pulp digester, twin roll pressvacuum drum washer, single screw press, pulp washer, blow tank, heat exchange, disc filter, and equipment of waste liquor recovery, etc.

CNBM specialize in paper pulp mill production. We can design a whole set of paper pulp plant for wood, straw, bamboo, rag, bagassewastepaper production, and also provide relative paper pulp machines. Based on 50 years’ experience in the pulping plant project, we’ll analyze these paper pulp mills from three main paper pulp processes of chemical pulping: pulp cooking process, pulp washing process and pulp bleaching process.

Pulp cooking process

The pulp cooking process is a key link of paper pulping. Paper pulp cooking process means a technic that treats fibrous materials with chemical liquor under a certain pressure. It also can be summarized as a kind of complex chemistry and chemical process.

In the pulp cooking process, there are a number of paper pulping machines, such as pulp digester, blow tank, heat exchange, and other accessory equipment.

Pulp digester

pulp digester

The pulp digester is the main equipment of the chemical pulping. It is the container for cooking plant fibers like wood, straw, rag and cooking liquor.  Due to the different cooking liquors and cooking technology, the pulp digester has different structures, shapes, and capacities. The rotary spherical digester and vertical digester are two main types of digester. The most popular type is vertically fixed digester, it applies to wood pulp, straw pulp, waste paper pulp, non-wood pulp making or other fibrous pulp production.

Blow tank

blow tank

The blow tank is designed for storing the pulp blown from the pulp digester. It generally installed with large-scale pulp digester. Flat bottom type and cone bottom type are two common types of blow tank. The flat bottom type blow tank is more popular, typical size include 80m³, 150m³, 500m³.

Pulp washing process and pulp bleaching process

Pulp washing process is used to clean the pulp and reduce the fiber lost. From the view of alkali recovery, paper pulp washing also plays a role in providing black liquor with high concentration and high temperature for the recovery system. Pulp washing process tries to increase the extraction efficiency of black liquor and reduce the use of water, which keep high concentration and high temperature of black liquor.

Pulp bleaching process is used to increase the whiteness and cleanness of paper pulp. After a series of treatment, use bleach to dissolve the colored substances or other things from the pulp. Pulp bleaching process border the range of pulp application, the bleached pulp can be used into fine paper and refine pulp making.

In real pulp process, pulp washing equipment both apply for pulp washing process and pulp bleaching process. Common pulp washing equipment includes twin roll press, disc filter, vacuum drum washer and single screw press, etc.

Twin roll press

twin roll press

Twin roll press is a pulp washing equipment that extrudes waste liquor from pulp with a pair of roll under the mechanical pressure. Main features include well-adapted, easy operation and etc. The twin roll press is easy to be broken by hard materials. It’s concentration of feeding pulp reach 8~12%, pulp concentration is 20~30%. For a single equipment, extraction ratio of waste liquor is 55~65%.

Vacuum drum washer

vacuum drum washer

The vacuum drum washer, also known as rotary drum washer, is washing equipment for straw pulp and wood pulp. Vacuum drum washer is used to solve wastewater pollution and measure alkali recovery project. The vacuum drum washer can be used alone or in series.

  • Concentration of feeding pulp: wood pulp (0.8%~1.5%), straw pulp (1.0%~3.5%)
  • Pulp concentration: 10%~15%
  • Vacuum degree: 26.7~40.0 kPa
  • filtration area: 5㎡ ~ 50㎡ or 100㎡
  • advantage:Easy operation; reliable technology, stable performance, high black liquor extraction rate (wood pulp is 95%, straw pulp is 83%~88%)
  • disadvantage:Complex structure, occupy a large area, easy to scum, high investment.

Disc filter

disc filter

Disc filter is used to recycle whitewater in the papermaking and pulp thickener in the pulp making. According to its functions, disc filter can be divided into disc filter for pulp thickener and disc filter for white water recovery. As the necessary pulp washing equipment, disc filter has a variety of advantages as follows:

  • Decrease the water consumption in the pulp making;
  • Low energy consumption and high fiber recovery;
  • High automatic and easy operation;

Single screw press

single screw press

Single screw press is used for black liquor extraction, chemical pulp bleaching or waste paper pulp concentration. Single screw press is usually installed under the blow tank. It dissolves the black liquor from the paper pulp by mechanical extrusion of radius and pitch screw. Single screw press and double screw press are used for waste liquor extraction in the pulp making process. They are applied to waste liquor extraction of wood pulp or straw pulp.

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