Switching between sour gas and fuel gas
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Please discuss: When the unit is shut down, when the amount of acid gas drops to what level can it be switched to fuel gas? Is there any basis for this? I saw a parking plan for a device that said it could not be switched until the amount of acid gas dropped below 35% of the design value. I don’t know the reason for this. Please share your opinions! Thank you!
If the amount of acid gas can maintain the normal temperature of the burner (1250 degrees), there is no need to start the combustion of fuel gas and oxidizing air. Unless the temperature of the burner cannot be maintained, the auxiliary combustion of the fuel gas will be started. Otherwise, the consumption of fuel gas will increase, and the burner will overheat. At this time, cooling steam must be introduced.
Usually during shutdown, if the amount of acid gas is within the normal operating elastic range, the fuel gas does not need to be switched to avoid environmental pollution caused by the acid gas discharge flare. When the acid gas is below the minimum load, the fuel gas should be switched to maintain the reactor temperature.
Reply 3# Clauspolunit makes sense! Switching is not required within the designed operating flexibility range.
Personally, I believe that the purpose of using sour gas to drive out sulfur is to increase the bed temperature of each converter, increase the peroxygen content, and reduce sulfur deposition on the catalyst as much as possible.； If there is enough acidic gas upstream, the time for acid gas to drive out sulfur can be appropriately extended to provide good conditions for the next step of fuel gas or inert gas to drive out sulfur. The less sulfur is deposited on the catalyst, the better the fuel gas to drive out sulfur. Also, if there is a little excess oxygen, it will not easily cause the bed to catch fire. When the acid gas volume is too low, the process gas flow rate of the entire system decreases, and the flow rate decreases, making it inconvenient to carry system heat. As a result, the sulfur drive cannot be complete and thorough. Therefore, the level at which the flow rate is lowered to stop the acid drive depends on the design process of different devices. Generally, if there is a low-flow interlock according to the design, the fuel gas can be switched to catch the sulfur after the interlock.