Frequency conversion control of auxiliary parts of paper machine

Auxiliary parts of paper machine usually include white water system, vacuum system, compressed air system, chilled water system, chemical dosing system, broken paper recovery system, ventilation system, etc. In the actual design of the paper machine, in order to make the paper machine run continuously and evenly, its auxiliary parts generally exceed 15%-35% of the maximum production capacity of the paper machine. Therefore, the use of variable frequency speed regulation and its control technology can effectively reduce auxiliary energy consumption in actual operation, such as fans and water pumps that were originally controlled by adjusting the valve opening, and belt conveyors running at a constant speed. The following describes the extensive use of variable frequency control in typical aspects.

1. Frequency control of chilled water

In the auxiliary equipment of the paper machine, the coating and sizing often require the use of frozen water to treat the coating to maintain the stability of the chemical properties of the coating. Its control principle is to use temperature or temperature difference control, because in a strict sense, the difference between the return water temperature and the outlet water temperature of the refrigeration host indicates the heat taken away by the frozen water from the coating tank, so the temperature difference can be used as a control basis. At the same time, because the outlet water temperature of the refrigeration host is generally relatively stable, in fact, it is only necessary to control the return water temperature in the design.

The frequency conversion speed control selected for the chilled water system should be designed to be PID control, because most of the frequency converters have PID function, so the control loop is very simple, the return water temperature is used as the feedback signal, and the target temperature can be controlled by the frequency converter. Panel setting or upper computer output analog signal setting.

2. Frequency conversion speed regulation of broken paper belt conveyor

The broke belt conveyor is responsible for transporting the broken or processed paper of the dry section to the dry break system, because the speed of the belt is usually designed according to the maximum speed of the paper machine, and usually the speed of the paper machine is 50%-80% of the maximum speed. In between, the constant speed operation of the belt will waste a lot of energy, and it will also generate too much noise. At this time, the frequency conversion speed regulation is adopted to make the speed of the belt conveyor follow the speed of the paper machine, and the starting frequency of the belt conveyor is 20 -30Hz, so that the belt can react quickly to avoid paper jams and reduce energy consumption.

With the development and maturity of the frequency conversion technology, the frequency converter will replace the traditional DC speed regulation system on the paper machine with its excellent speed regulation performance, simple operation, perfect function, easy to realize automatic adjustment and many other advantages, and become a paper machine electrical The best in transmission.