Control of vacuum degree in vacuum distillation
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In vacuum distillation, vacuum pump sets are commonly used to create a vacuum environment in the system. Generally, the pumping capacity of these vacuum pump sets is greater than the amount of gas generated by the system, which makes it necessary to control the vacuum level in the system. In the past, bypass control valves were used alongside the pipelines to regulate the vacuum level. For example, in a system of rotary vane pump + rotary vane pump + water ring pump, can frequency conversion control be used to regulate the vacuum level? How should the pumping speed ratios of the 3 pumps be selected during frequency modulation control? For example, for a pump with a pumping speed of 600 L/s, one could choose a pumping speed ratio of 600+150+70 in order to control its speed. What are the problems associated with such a choice, or what are the limitations of this configuration?
Generally, a water ring pump combined with two Roots pumps can achieve an ultimate vacuum of around 40 Pa. The selection of components should be based primarily on your operating pressure, the maximum pressure difference that the Roots pumps can handle, and the level of heat generation produced by those pumps.
The water ring and Roots compression ratio (as well as the pumping speed ratio) should be kept as low as possible to prevent excessive pressure differences in the Roots pump and overheating during operation； For 600/150/100 water ring types, the operating pressure should not exceed 1000 Pa when it is within 500 Pa.