In papermaking production, how to choose a suitable water-ring vacuum pump to match it seems more complex, but as long as we adhere to the following principles, it will be easier to achieve a reasonable configuration of water-ring vacuum pump.
1. Selection of new energy-saving products
At present, there are several series of water-ring vacuum pumps, such as 2BE, CL, which are suitable for paper industry in domestic and foreign markets. Through the development of new products of water-ring vacuum pumps for rough and low vacuum industry in recent years, the efficiency of water-ring vacuum pumps has been greatly improved. The 2BE series water ring vacuum pumps developed by our company in recent years have the highest efficiency of pumping dry air up to 67% under the condition of the experimental station. It will be more efficient for the paper mill to suck wet air. The efficiency of the liquid-ring vacuum pump introduced by many relevant information about water-ring vacuum pump is only 35%~50%. Obviously, these data can not keep up with the new changes brought by the new technology.
2. Selection of Low Speed Water Ring Vacuum Pump
Because the efficiency of water ring vacuum pump is directly related to the speed, the relationship between the pump gas volume and the speed is one-order, but when the speed is high, the relationship between the shaft power and the speed is approximately second-order. When the rotational speed is increased by 10%, the gas volume is also increased by 10%, while the shaft power is increased by about 20%. Therefore, when choosing vacuum pump, the water ring vacuum pump with low rotational speed should be selected as far as possible. It is better to choose the speed corresponding to the linear speed at the end of the impeller blade when it is below 18 m/s. At this time, the efficiency of the pump is usually higher. Of course, relative to the higher speed of the pump will pay more purchase costs, relative to the cumulative increase in energy consumption, in the context of increasing emphasis on energy conservation and consumption reduction, it is obviously worthwhile to choose low-speed energy-saving products.
3. Reasonable combination of vacuum points
Vacuum points with similar vacuum degree and space position should be combined and sucked by a larger vacuum pump. The combination should be considered to be conducive to pipeline layout, and the combination should be different from each functional area. When the gas volume is similar and the vacuum degree is different, the pump with baffle can be selected. For example, between the suction tank of upper and lower wool cloth and between different vacuum suction rollers, the pump with partition can be selected.
4. Combination point gas volume should be converted
Because the gas is compressible, the volume of the gas expands when the high-pressure gas is reduced to the low-pressure gas. If it is necessary to combine the high vacuum chamber and the low vacuum chamber of the vacuum roller, the vacuum degree and the gas volume of the high vacuum chamber are – 65 kPa and 80 m3/min respectively, and the vacuum degree and the gas volume of the low vacuum chamber are – 40 kPa and 50 m3/min respectively, then the gas volume of the low vacuum chamber should be first converted to the gas volume at – 65 kPa, and the converted gas volume is 84.4 m3/min ((101.3-40)/(101.3-65) x5. 0 = 84.4), then the air volume of the pump should be 164.4 m3/min, rather than 130 m3/min.
5. Appropriate consideration should be given to pipeline losses
The gas pumped from each vacuum element will flow in the pipeline with a certain pipeline loss, which will cause the pressure drop and volume expansion of the gas. In the case of reasonable design of pipeline size, the loss of pipeline can be 2-3 kPa (small value for high vacuum and large value for low vacuum).
6. Temperature correction should be appropriate
Because the air pumped by the pump on the paper machine is wet air with higher temperature, and the working fluid of the water ring vacuum pump has higher water temperature due to various restrictions, which is inconsistent with the working condition calibrated on the performance curve of the water ring vacuum pump, so the temperature and water temperature need to be corrected. When the temperature is relatively high and the water temperature is relatively low, the revised air volume will be relatively small, and the selected pump will be relatively small, otherwise the selected pump will be larger. The specific temperature to be taken for correction should be determined by the parameters of the paper machine and the specific conditions of the paper mill. Usually, it is feasible to take the temperature of 45 and water temperature of 35 for correction, the result is safe and reliable.