Material gas concentration control system

Abstract

A material gas concentration control system for keeping a concentration of a material gas in a mixed gas constant comprising a tank to accommodate the material, an inlet line to input a carrier gas for evaporating the accommodated material into the tank, and an outlet line to output the mixed gas consisting of the material gas evaporated in the tank and the carrier gas, and further comprising a first valve arranged in the inlet line, a concentration measuring part that measures the concentration of the material gas in the mixed gas, and a concentration control part that controls an open degree of the first valve so as to make the measured concentration of the material gas measured by the concentration measuring part become the previously determined set concentration.

Description

technical field [0001] The present invention relates to a system for controlling the concentration of the vaporized material gas in a material vaporization system for introducing a carrier gas into a solid or liquid material stored in a storage tank to vaporize the material. Background technique [0002] As the concentration control system of the material gas in this kind of material gasification system, a system disclosed in Patent Documents 1 and 2 can be cited, which includes: a mass flow controller (massflow controller), which is arranged in the introduction tube for introducing the carrier gas ; a constant temperature tank, which is used to keep the storage tank storing the material liquid at a constant temperature; and a manometer (manometer), which is arranged in the outlet pipe for exporting the mixed gas of the material gas and the carrier gas, and is used to measure the pressure of the mixed gas, that is, Measure total pressure. [0003] The system keeps the mater...

AI Technical Summary

Problems solved by technology

[0012] Second, if Figure 8 As shown in the graph of , if the material liquid in the storage tank decreases and the volume of the gas increases, when the set concentration is changed, the control time (permanent time) it takes until the measured concentration reaches the same value will change. long

The reason can be considered that the total pressure in the storage tank changes due to the increase in the volume of the gas in the storage tank, resulting in an increase in the flow rate of the carrier gas necessary for the concentration to reach the desired value. The gas replacement time until the gas is replaced to the required gas concentration becomes longer

[0013] In other words, when the material liquid decreases, the system that has been the control object until then will change to a system that wastes more time. Therefore, when a step such as changing the set concentration is input, the measured concentration that is output Will greatly exceed the limit (overshoot), which will cause hunting (hunting), resulting in longer settling time

[0014] In addition, since the response speed of the concentration measuring unit decreases with changes in various measurement environments, there is also the problem that the settling time becomes longer as described above due to an increase in wasted time.

[0015] For this kind of problem, although it can also be considered to increase the flow rate of the carrier gas and shorten the gas replacement time to shorten the settling time, the flow rate or the total flow rate of the material gas will also change, so it cannot be kept at a constant flow rate

[0016] "Increase in wasted time due to increase in gas volume in the storage tank"

[0017] Third, in this type of control system, when the material liquid decreases and the volume of the gas in the storage tank increases, when changing the set concentration, the mixed gas in the storage tank is completely replaced with the new setting Concentration of gas is more time-consuming

However, this solution becomes a major cause of man-hours or new costs for installing the liquid meter in the tank

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