Pressure issues in transformation
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Our plant uses a process for producing methanol from coke oven gas. In the conversion section, the process requirements specify that the steam pressure must be higher than the oxygen pressure, the oxygen pressure must be higher than the gas pressure, and the gas pressure must be higher than the system pressure. Many people can’t say why. The reason given isn’t very convincing. Additionally, for our steam pressure, we use the pressure in the drum; for system pressure, we use the pressure at the end of the conversion process; and for gas pressure, we use the pressure after precise desulfurization. Is this approach appropriate? I’m a newcomer, so I would appreciate any guidance from the experienced teachers here.
Coke oven gas is converted through catalytic partial oxidation into carbon monoxide and hydrogen, which are the key components for synthesizing methanol; steam is added to prevent carbon deposition. The steam pressure is greater than the oxygen pressure, which is in turn greater than the gas pressure; it’s around 0.2 MPa. As for why, it’s extremely simple: if the steam pressure is lower than the oxygen pressure, can it be added to the oxygen? The measurement points you mentioned for steam pressure, system pressure, and coal gas pressure are reasonable; the pressures at these locations are representative.
Thank you for your explanation. I’m still a bit confused: it’s true that steam is mixed with oxygen, but the oxygen pressure is the pressure before the valve; once it passes through the valve and enters the system, the oxygen pressure behind the valve becomes approximately equal to the system pressure. Steam is introduced into the oxygen pipeline behind the oxygen valve, and enters the system together with oxygen. At this point, it can be said that oxygen can be introduced as long as the steam pressure is higher than the system pressure; in actual production, we have also tried using the highest oxygen pressure followed by the steam pressure. I wonder if this rule was established to prevent accidents caused by steam not being able to reach the oxygen due to pressure buildup in the system? Also, is it appropriate to use the pressure at the end of the conversion as the system pressure? Steam, gas, and oxygen enter the system at the converter; therefore, pressure points should be taken near the converter. At the end of the conversion process, the gas may pass through several devices, resulting in a pressure drop, so the pressure there will be lower than that near the converter. If the resistance of the devices is high, the system pressure readings will not be accurate. I’m not sure if my thoughts are correct; please give me some guidance.
Reply to Floor 1: The operation of the conversion furnace requires that the steam pressure be higher than the oxygen pressure, and the oxygen pressure to be higher than the gas pressure; these values are 2 kilograms respectively. This is done for safety reasons during production. As for steam, there’s no need to explain further. The reason why the oxygen pressure must be higher than the gas pressure is to protect the oxygen nozzles – if the gas pressure is too high, it will enter the oxygen nozzles and cause combustion, thereby shortening their lifespan. Coking gas does not present such a problem with nozzles.