Paper machine auxiliary facilities include the following systems: pulp supply system, white water system, vacuum system, compressed air system, chemical preparation and delivery system, water supply system, steam system, etc. In order to make the paper machine run continuously and evenly, the capacity of its auxiliary facilities should generally exceed the maximum production capacity of the paper machine by 15% to 30%.
Here we take the pulp supply system as an example to show you the effective means and methods of the use value of frequency conversion technology in papermaking.
Application of frequency conversion slurry supply system
The slurry supply system must meet the following conditions:
- (1) The slurry delivered to the paper machine should be stable, and the error should not exceed 5%;
- (2) The ratio and concentration of mud should be stable and uniform;
- (3) Reserve a certain amount of pulp in order to adjust the pulp supply capacity and adapt to changes in the speed and variety of the paper machine;
- (4) Purification and selection of slurry;
- (5) Handle shredded paper in various parts of the paper machine.
Generally, the slurry supply system consists of a slurry pump in the slurry supply pipeline, a slurry flushing pump, a pressure screen and a slag remover in the purification facility. To achieve the above five goals, the most important thing is to transform the slurry pump and flushing pump from full-speed operation to speed-adjustable frequency conversion operation, and finally meet the automation of slurry supply.
Take the slurry pump as an example to illustrate the speed control process of frequency conversion speed regulation: frequency conversion control should adopt the speed control mode of double closed loop system, the outer loop is the speed closed loop, and the inner loop is the current or torque closed loop. On the one hand, the set value of the pulp pump speed is obtained through the change of the pulp speed and the net speed ratio, and on the other hand, it comes from the pressure controller of the headbox. The former is the main tone, and the latter is fine-tuning. The ratio of the pulp speed to the wire speed of the paper machine is basically constant, so once the wire speed of the paper machine changes, the speed of the pulp pump also changes.
At the same time, in order to improve the accuracy of the speed regulator and reflect the actual process of the headbox, it is usually necessary to take the ±5% change of the output value of the headbox pressure PID control as the additional speed setting value of the slurry pump. The actual value of the speed is sampled from the actual speed of the driving motor, which can be obtained by a detection device such as a rotating speed measuring motor or a photoelectric rotary encoder. The setting value of the current is obtained from the output signal of the speed loop, and the actual value of the current is obtained from the measurement value of the AC variable frequency output current transformer of each transmission point.
Therefore, for the frequency conversion speed regulation of the slurry pump, PID control is required, and the speed feedback mode and various parameters of PID need to be correctly selected. Knowing this is very important for choosing the right inverter brand and product type.
Paper machine auxiliary facilities include the following systems: pulp supply system, white water system, vacuum system, compressed air system, chemical preparation and delivery system, water supply system, steam system, etc. In order to make the paper machine run continuously and evenly, the capacity of its auxiliary facilities should generally exceed the maximum production capacity of the paper machine by 15% to 30%.
Here we take the pulp supply system as an example to show you the effective means and methods of the use value of frequency conversion technology in papermaking.
Application of frequency conversion slurry supply system
The slurry supply system must meet the following conditions:
- (1) The slurry delivered to the paper machine should be stable, and the error should not exceed 5%;
- (2) The ratio and concentration of mud should be stable and uniform;
- (3) Reserve a certain amount of pulp in order to adjust the pulp supply capacity and adapt to changes in the speed and variety of the paper machine;
- (4) Purification and selection of slurry;
- (5) Handle shredded paper in various parts of the paper machine.
Generally, the slurry supply system consists of a slurry pump in the slurry supply pipeline, a slurry flushing pump, a pressure screen and a slag remover in the purification facility. To achieve the above five goals, the most important thing is to transform the slurry pump and flushing pump from full-speed operation to speed-adjustable frequency conversion operation, and finally meet the automation of slurry supply.
Take the slurry pump as an example to illustrate the speed control process of frequency conversion speed regulation: frequency conversion control should adopt the speed control mode of double closed loop system, the outer loop is the speed closed loop, and the inner loop is the current or torque closed loop. On the one hand, the set value of the pulp pump speed is obtained through the change of the pulp speed and the net speed ratio, and on the other hand, it comes from the pressure controller of the headbox. The former is the main tone, and the latter is fine-tuning. The ratio of the pulp speed to the wire speed of the paper machine is basically constant, so once the wire speed of the paper machine changes, the speed of the pulp pump also changes.
At the same time, in order to improve the accuracy of the speed regulator and reflect the actual process of the headbox, it is usually necessary to take the ±5% change of the output value of the headbox pressure PID control as the additional speed setting value of the slurry pump. The actual value of the speed is sampled from the actual speed of the driving motor, which can be obtained by a detection device such as a rotating speed measuring motor or a photoelectric rotary encoder. The setting value of the current is obtained from the output signal of the speed loop, and the actual value of the current is obtained from the measurement value of the AC variable frequency output current transformer of each transmission point.
Therefore, for the frequency conversion speed regulation of the slurry pump, PID control is required, and the speed feedback mode and various parameters of PID need to be correctly selected. Knowing this is very important for choosing the right inverter brand and product type.
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