The entire plant’s fuel system affects the temperature of the furnace; I would like to ask fellow experts for any good suggestions
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Our plant is involved in catalysis, aromatization, and gas production from steam cracking, providing fuel for the entire plant. However, due to unstable pressure in the gas system, a bypass connection between natural gas and gas has been installed; when the gas pressure is insufficient, natural gas is used to supplement the pressure. However, when supplementary pressure is applied, due to differences in calorific value, does proportional-integral-derivative control need to be adjusted during automatic control by the regulating valve? When there is an ample supply of gas, the pressure also experiences significant fluctuations, which affects operations. Do any of the more experienced colleagues have any good methods for dealing with this? Please give me some advice!
The situation is the same here as well: whenever there is a significant change in the calorific value of the gas, the furnace temperature also fluctuates greatly. In cases of sudden fluctuations, adjusting the PID parameters does not yield very good results; it is better to switch the furnace’s temperature control valve to manual mode and make gradual adjustments. Once the gas composition in the system stabilizes, the system can be switched back to automatic mode. Here, we have a gas liquid separation tank before the gas is fed into the furnace. This tank is equipped with a pressure control valve, which helps to maintain a stable pressure of the gas entering the furnace, thereby preventing fluctuations in furnace temperature caused by unstable pressures in the external gas system. When the calorific value of the gas decreases and the furnace temperature fails to rise, the adjustment method we use is to increase the pressure in the gas liquid separation tank appropriately. At the same time, we adjust the air valves and flue dampers to ensure stable negative pressure and oxygen levels in the furnace. It is possible to gradually figure out the most effective adjustment methods by considering the specific conditions of one’s own installation.
This PID definitely cannot be adjusted; our plant has high, medium, and low levels of gas, and there are multiple pressure control systems in place. The excess gas is first directed to the low-pressure buffer tank, namely the inlet cabinet.
In such a situation, it’s definitely not possible to set the pressure control valve to automatic mode. We also have dry gas cabinets here for storing low-pressure fuel gas, which is then pressurized by screw compressors and fed into the fuel gas network to maintain the desired pressure. Regarding the frequently fluctuating fuel pressure, the furnace previously used gas tanks; moreover, it was difficult to control the furnace temperature, so manual control had to be relied on based on experience
To address this issue, a pressure reducing valve can be installed at the main pipe where the gas enters the device.
Our gas system has a buffer tank and a pressure-controlled regulating valve before it enters each unit device, but it still doesn’t work well; it’s greatly affected by fluctuations in the main pipeline network.
This is indeed quite troublesome. My previous workplace faced the same issue; in order to maintain stability in the properties of the fuel gas, we analyzed the data and adjusted the amount of natural gas used to keep it relatively constant. We then used gas tanks to regulate the pressure of the fuel gas – releasing gas into the tanks when the pressure was high, and sending gas from the tanks back into the fuel gas system when the pressure was low, thereby balancing the usage. Since there is always a shortage of gas, the challenge lies in determining when to replenish it. Adjusting this process is very complicated; it took us almost 2 years to get everyone used to this approach. It required coordination among the power plant, storage and transportation departments, coking plant, and sulfur processing plant – everyone had to work together
Yes, it’s too troublesome to adjust it now.