Liquid ring vacuum pump is widely used in vacuum system of paper industry and water removal field of paper machine. Application of vacuum pump in papermaking industry: black liquor evaporation, coarse slurry washer, lime slurry and filter, sediment filter, vacuum dehydrator, degassing system of raw material and white water, mixer compressor, suction tank, couch roll, suction roll and transfer roll, vacuum press.

 

Black liquor evaporation

The black liquor evaporator in the pulp mill is used to concentrate the black liquor produced in the pulp cleaning process, so that these liquids can be recovered in the recovery furnace and reused in the pulp production.

 

Coarse pulp washer

The rougher removes Pulp Chemicals ("black liquor") from the raw material before bleaching or other raw material preparation. The coarse pulp washer is a typical horizontal drum filter. The inner cavity of the drum can produce a vacuum. When the drum rotates in the raw material slurry, the vacuum can make the raw material adhere to the outer surface of the drum and help remove (clean) the black liquor from the raw material.

 

Lime slurry and filter

The lime mud filter in the pulp mill is used to recover the lime in the white water clarification process. Similar to the coarse slurry washer, the lime slurry filter is a typical horizontal drum filter. The inside of the drum creates a vacuum. As a drum rotates in the mud, a lime cake forms on the surface. It is then scraped off and reused in the white water process.

 

Sediment filter

In the pulp mill, the precipitate filter is used to filter the unburned suspended particles, fully burned carbon particles, iron compounds and insoluble furnace body debris in the "green liquid", and remove them before they are scaled. The sediment filter is a typical horizontal drum filter. A vacuum can be generated inside the drum to extract particles from the green liquid.

 

Vacuum dehydrator

The vacuum dehydrator is used to dehydrate in the raw material preparation stage to improve the raw material concentration. The dehydrator is a typical horizontal drum filter, which is used to dehydrate the pulp in proportion to increase the concentration of raw material.

 

Raw material and white water degassing system

The raw material and white water degassing system is used in the raw material preparation stage to remove the air carried by the raw material or the air from the dilution water before the raw material enters the mixing tank. Raw material and white water degassing system is very important, because the removal of air from paper raw materials, which can lead to pinholes on paper, and greatly affect the printing quality, mechanical properties and overall quality.

The degassing system is a typical two-stage vacuum system: the boiling point of raw material at the inlet of the first stage vacuum pump (27-28 ℃) in.HgV ）The inlet pressure compression ratio of two-stage vacuum pump is 4:1. A pre condenser is typically used between the degassing vessel and the primary vacuum pump, and a small interstage separator is required between the two vacuum pumps. Vacuum pumps are made of standard materials.

 

Headbox compressor / vacuum pump

The mixer compressor / vacuum pump is used in the "air cushion" mixer to generate a pressure / vacuum above the level of the raw material in the mixer (or "raw material pool") and to control the discharge speed of the raw material to the maximum extent (the "jet" speed). The pump is usually used as a vacuum pump and compressor through a series of valves to generate vacuum or pressure in the gap volume above the "raw material pool" to control the static head of the mixing box.

 

Suction tank

The water suction tank is a static equipment, which is directly dehydrated from the pulp on the forming section of the paper machine. There are generally 2-10 water suction tanks on the paper machine, which are usually connected to form a main pipe. Because of the large amount of dehydration, it is necessary to set a pre separator between the suction tank and the vacuum tank. The liquid ring pump is used to generate the vacuum in the vacuum tank of the suction tank.

 

Couch roll

In many cases, the couch roll is the last vacuum point on the forming section, which is called the most important dehydration part of the paper machine. When the paper enters the press section after the couch roll, the dryness of the paper affects the dehydration performance of the press section and the steam consumption of the drying section. The couch roll is stationary with a rotating porous shell. The couch roll can have one or two vacuum zones.

 

Suction roll and transfer roll

The suction roller sucks the paper away from the mesh in the forming stage and guides it into the press section. Then, in the press section, the transfer roller transfers the paper from one woolen cloth to another. None of these processes is formally dehydrated, but a small amount of water can be removed from the paper.

 

Vacuum press

Vacuum press uses mechanical method to extract water from paper. In the pressing section, the rollers with granite and hard rubber surface are in close contact, forming a "pressing zone". A typical paper machine may have 1-3 "nips". When the paper passes through the pressing area, the moisture in it is squeezed out and infiltrated into the pressing woolen cloth. When the paper passes through the pressing part, the woolen cloth is used as the transport tool and cushion of the paper. In the dehydration process, there are vacuum and non vacuum rollers in the press section.

 

Wool suction tank

When the pressing part is pressed, the pressed fabric (or "woolen cloth") contains a mixture of water, chemical materials, papermaking materials, soil and filler, sticky residue ("asphalt") produced in papermaking process and glue ("sticky substance") produced by recycled paper. Since each wool cloth is a continuous cycle, it is necessary to remove moisture and contaminants before the next press starts. The vacuum suction tank is a fixed suction tank, which exceeds the width of wool cloth and absorbs the water and pollutants accumulated in the pressing process of wool cloth. Each wool cloth has two vacuum suction tanks. When using the vacuum suction tank, it must be pre separated to avoid carrying water into the vacuum pump.

 

Blow proof box

In the press section, there are some "open" nips, which do not support the paper before entering the nip. The air flow may cause the paper to shake, fold or damage. The blow box is fixed and is used to create a vacuum upstream of the nip before the paper enters. Since the blow box cloth is used for dehydration, it is unnecessary to carry out pre separation treatment.