Is it better to use pressure feedback control for the furnace outlet temperature or flow rate feedback control for the fuel gas?
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Is it better to use cascade control with the outlet temperature of the heating furnace and the pressure of the fuel gas, or with the flow rate of the fuel gas? Does each approach have its own advantages and disadvantages, or can it be chosen arbitrarily? Everyone is welcome to join the discussion.
I’ve changed it to manual mode~~~~ Using the cascade control often leads to problems~~~
Is that coupled to the fuel gas pressure or the flow rate?
May I ask, what kind of device do you have?
Here, we don’t use automatic systems; instead, diesel hydrogenation is employed. In my opinion, a cascade control system based on flow rate is a better approach. The pressure of the fuel gas entering the unit is regulated and stabilized by control valves. Generally, the gas pressure in front of the furnace is kept very low, but the flow rate is high. Since the pressure is already low, if pressure control using a cascade system is employed, even slight fluctuations in pressure can have a significant impact ； If it is cascaded with flow, since the flow rate is high, even slight fluctuations in flow have a much smaller impact.
Our furnace and pressure control are in cascade.
So, are you dealing with hydrogenation units or aromatic units? Hydrogenation units combined with pressure cascade systems are quite rare.
Here we have three controllers in cascade: the main controller for the reactor inlet temperature, the MV for the inlet temperature is the SV for the heater outlet temperature, and the MV for the heater outlet temperature is the SV for the fuel gas flow rate. This allows for effective regulation of temperature fluctuations caused by various factors.
It can’t be generalized. It is necessary to look at specific furnaces. For example, in a converter, the outlet temperature is ultimately controlled through the fuel flow rate. If the composition of the fuel remains stable, its calorific value is also related to the flow rate; by properly controlling the flow rate, it becomes easier to control the temperature as well. However, fuel pressure affects the shape and stiffness of the flame, as well as the temperature distribution within the furnace tubes; therefore, in the design of many conversion furnaces, interlocks for high and low fuel pressures are installed.