Application of PID control in gas production
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Our company experiences significant flow fluctuations during gas production; we are wondering whether using POD tuning can help achieve stable operation. I hope experienced seniors can offer some guidance. Our company uses two-stage gas generators. My idea is that the blower adjusts automatically by changing its frequency based on the pressure in the main air duct, while the gas conveyor adjusts the blower’s frequency according to the pressure in the low-pressure main duct. Can this idea ensure the stable operation of gas production? I hope everyone can provide valuable suggestions! Thank you!
If the flow rate itself varies greatly in the process, instrument-based automation cannot solve this issue.
It is controlled directly by the pressure measurement behind the fan; such fluctuations hardly occur, and they are caused by usage downstream. Single-loop control is fine; I’m not sure if there’s any connection between these two sections, as otherwise they might affect each other
From a technical standpoint, I think it’s feasible. The single-stage furnace used in Jinan Huangtai, which we employ, is designed in this way (single-stage furnaces are scheduled to be phased out); a PID regulator is used, based on the pressure in the low-pressure main pipe, to automatically adjust the frequency of the blower’s inverter. The problem is that it has never been put into actual use since the joint commissioning started (with manufacturer personnel involved in the debugging). I think there’s an issue with the adjustment of the proportional parameters; as soon as it starts operating, the frequency increases automatically, causing the outlet disc valve to be overpressured. Worse still, even when it is not in use, accidental pressing of the “automatic” button during operation can lead to repeated breaches in the water seal of the disc valve, resulting in insufficient low pressure and thus the shutdown of the rotary kiln. In the end, I had no choice but to “remove” the button. If the poster is confident in PID control and in the reliability of the pressure sensor measurement points (as an accident can occur if the sampling tube gets blocked), they can give it a try.
Thank you very much for your comment. The two-stage furnace we are using now does not have as good air permeability as a single-stage furnace. The DCS control system we use has never been put into automatic mode. During operation, there were instances of the water seal at the bottom of the furnace being breached, which is also one of the reasons why automatic operation is not feasible. Later, I consulted the maintenance staff; it is possible to limit the pressure in the main air duct to prevent the water seal at the bottom of the furnace from being breached, but this has not been put into practice yet.