Regarding the issue of large fluctuations in the inlet flow rate for methanol synthesis
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At our plant, the flow rate of the feed gas used in methanol synthesis varies significantly between day and night: it can reach 410,000 units during the day, but drops to 340,000 units at night. The amount of fresh gas at the inlet of the syngas compressor also decreases, yet the amount of gas that undergoes conversion remains unchanged What is the reason for this? ? 、
Are the emissions of synthetic purge gas the same during the day and at night? Is it the issue of lower temperatures at night, which leads to higher consumption of purge gas? For reference only!
During the day, the temperature rises behind the methanol water cooler; the increase in the temperature of the circulating gas leads to an overall rise in the system’s temperature. It seems that the viscosity of the gas increases as the temperature rises, which may result in certain discrepancies in the readings provided by the instruments. The conversion load is fine; if that’s the only reason for the fluctuations. I’m not sure if it’s because the flow meter installed in your plant hasn’t been calibrated for pressure and temperature; I don’t seem to encounter this problem on my end. Although the temperature changes significantly after water cooling during day and night, the inlet flow rate generally fluctuates with the load.
Reply to 2# aiaiqiuqiu: Our amount of vent gas will vary, but the change isn’t significant; it should not have an impact on the volume of gas fed into the synthesis process, right?
Reply to 3# lizhaoye: It’s probably not a problem with the instruments. Based on the overall data from the synthesis system, we observe a decrease in inlet flow, a decrease in circulation volume, a drop in methanol production, poor gas composition, and also a decrease in the inlet flow for the compression stage.
Has there been any change in the system pressure? If there is internal leakage in the anti-surge section of the compressor, the pressure in the synthesis system decreases, and both the flow rate at the inlet of the synthesizer and the flow rate of the recycle gas should change. However, the changes you mentioned seem quite significant; I’m not sure if this is the cause. I think the data you provided is incomplete; it only shows the phenomena, and more data along with a broader range of considerations are needed.
The emissions of synthetic purge gas should be determined based on the operating conditions of the synthesis system and the gas composition. As for whether the emission levels are higher during the day or at night, there is no conclusion, nor is one needed.
Well, I’m wondering about the reasons behind the decline in synthetic inbound traffic? ?
If the consumption during the day is also high. The amount of fresh gas is reduced, resulting in lower production; there is little change in the vent gas volume. Where do the changes in components mainly occur? If the hydrogen level is high, then this is normal: the gas volume readings decrease, the pressure increases, and the production volume drops. Also, check to see if there is less CO2. If there is less CO2, all of these will be normal. I’ve seen a conversion system with CO2 recovery before; it’s normal if there are issues here as well. Go and talk to the person in charge of conversions. We outsiders can only guess, haha
Reply to 9# lizhaoye: During the day, the compression volume of the coke oven gas compressor remains unchanged; however, the flow rate at the inlet of the syngas compressor gradually decreases. The amount of gas entering the synthesis process drops, from 390,000 to as low as 325,000. The amount of fresh gas entering also decreases, resulting in a lower concentration of useful gas components in the syngas and an increased proportion of inert gases. This leads to poor performance of the synthesis reaction, an increase in pressure within the synthesis system, and consequently a decrease in methanol production. (The amount of exhaust gas released will change slightly, but it should not have an impact.)
I asked questions, but you didn’t answer any of them. If there is no CO2 recovery during the conversion process, then this problem doesn’t arise. Given that mass conservation is also satisfied, if everything else is fine, then there’s only one remaining issue: air leakage before the material enters the compressor during the day.