Vacuum system of paper machine

The equipment and accessory devices of dewatering, drainage and exhaust (steam) in paper workshop can be classified as vacuum system of paper machine. In addition to the vacuum system of the wet part, it also includes the condensate discharge vacuum device at the end of the steam condensate system and the matching vacuum device for the vacuum roller. The wet end vacuum system mainly includes: vacuum components, front stage gas-water separator, vacuum pump (or fan), rear stage gas-water separator, vacuum pipeline and other components.

The installed power of vacuum system is 370 ~ 6000kW. These systems will not affect the papermaking process under low efficiency, but will increase the operating cost.

Paper mills can save energy in many ways, one of which is vacuum system.

The vacuum system of paper machine is a necessary and effective means to help the paper dewatering in the forming and pressing sections. The performance and efficiency of the vacuum system need to be maintained frequently, otherwise the treatment method of permanent cure will make some performance decline continue or be covered up.

Inspection of vacuum system:

The inspection of vacuum system requires a comprehensive and systematic understanding of the whole process of vacuum assisted dehydration (from forming department to pressing department). The items to be inspected include vacuum dehydration element, vacuum roller, suction tank, separator, vacuum control system, discharge pump, air pressure sealing box / pool, vacuum pump, sealing water system, cooling tower and air / water discharge system, and the correct design shall be referred to principle.

Vacuum components should be compared with the current TAPPI standard or similar paper machine manufacturing standards. In addition, it is necessary to find out the reasons that restrict the production and quality.

common problem:

Some problems of vacuum system may cause high energy consumption, high cost and low efficiency of the whole system. These include:

1) Seal water becomes hot. The increase of seal water temperature (higher than 32.2 ~ 37.7 ℃) will reduce the efficiency of vacuum pump and the capacity of vacuum system. The results show that when the temperature of sealing water is reduced from 42.2 ℃ to 32.2 ℃, only 5 vacuum pumps are needed for a new paper machine with 6 pumps, which can significantly reduce the installation and operation costs.

2) As a result of irregular or high sealing water pressure, the sealing water pressure of vacuum pump is usually 30 ~ 40Pa, while the recommended water pressure is 10 ~ 15pa. The practice of “the more the better” for papermaking workers is an example of increasing the cost.

3) Vacuum pump back pressure caused by system design or operation problems. Some old systems will have back pressure on the vacuum pump. If the air and water discharge system is not improved, the back pressure will be enlarged. Theoretically, a vacuum system should not have a back pressure higher than 6.9kpa (in terms of pump discharge) during vacuum drainage.

4) Synchronous or asynchronous motors affect the power factor, including motor and driver and motor type / vacuum pump power.