IMPROVED APPARATUS FOR CONTROLLING A MASS FLOW RATE OF LIQUID IN A CHEMICAL PROCESS

摘要

1287435 Automatic mass flow control TORAY INDUSTRIES Inc 26 Aug 1969 [29 Aug 1968] 42460/69 Heading G3R In a chemical process, liquid is supplied to a container and removed therefrom under the control of automatically operated on/off and variable control changes in weight controlling the variable control to maintain a constant mass flow. In Fig.1, an on/off valve or pump 1 is operated periodically under the control of a device 7 so that liquid is supplied intermittently to a weighing container 2 from which it flows continuously through a flow regulator 3. A force-balancing electrical or pneumatic transducer associated with container 2 produces a signal W which controls device 7 so that the supply of liquid is stopped when the weight reaches an upper limit and started when it reaches a lower limit. A device 5 associated with a source of timing pulses 4 repeatedly detects either the time taken for the weight in the container to fall from one predetermined value to another or the loss in weight in a given time. This measurement is utilized to calculate the average mass flow which is compared with a desired flow by a unit 6 so that any error is effective to control regulator 3 to restore the desired flow. In one modification, the on/off value or pump 1 is arranged in the outlet from container 2 and the regulator in the inlet. In another modification, the rate of flow is corrected by controlling the datum of an automatic system stabilizing gas pressure in an enclosure surrounding the weighing container. The enclosure may be heated or cooled to achieve a desired temperature.