Methanol production cannot be increased
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Colleagues, one of our plants equipped with a 300,000-ton methanol production unit is able to supply the necessary raw materials, but the output of crude methanol does not increase. I would like to know what could be the reason for this At a load of 25,000, with a carbon dioxide addition of around 6,400, the yield of crude methanol was 45 tons; when the load was increased to 29,000, the yield of crude methanol was still only 46.5 tons, at which point the carbon dioxide addition was around 6,800
Hehe, I only have knowledge about catalysts. The situation mentioned by the poster may be related to the catalyst. Based on what you said, 45 tons per hour; assuming 300 days per year, then 24*45*300 equals 320,000 tons as well (hehe, I’m not sure if this calculation is correct). The yield of the catalyst is fixed; in China, it generally ranges from 1.0 Kg/h.l to 1.3 Kg/h.l. Therefore, what the poster is referring to might be the situation where the catalyst has reached its maximum load capacity.
Increasing the volume of circulating gas does not necessarily lead to an unlimited increase in production. On one hand, the catalyst plays a role; on the other hand, the ratio of CO, C2O to hydrogen is important. Another key factor is that an excessive amount of inert gas is also not acceptable.
What is the unit behind this? Original poster, please specify the content of crude alcohol, the system’s synthesis pressure, as well as the gas composition. Of course, please also provide all the parameters related to production, so that it will be easier to analyze the reasons behind the issue. However, if you simply increase the gas volume by a few thousand units, the output will increase by nearly two cubic meters, which is also in line with reality.
1. Adjust the circulation volume; both too high and too low levels are undesirable. 2. Determine an appropriate H/C ratio. 3. Check whether there are any issues with gas quality (toxic substances) exceeding specified limits, and take appropriate action to address them. 4. Verify whether the separator is operating under excessive load, as well as whether the alcohol content at the inlet of the synthesis tower is above the allowed level; if the separator is under too much load, measures should be taken to improve its separation efficiency, either by upgrading it or making improvements. 5. Check for blockages or increased resistance in the separation system/pipes, and conduct tests to determine this.
Question: In China, the values are generally between 1.0 Kg/h.l and 1.3 Kg/h.l. What is the unit behind this? You’re welcome. This is the amount of alcohol produced per liter of catalyst per hour
The designed daily production capacity of a 300,000-ton methanol plant is 300,000/300/24 = 41.66 tons/h; operating at 45 tons/h represents a load of about 8% above this capacity. When the feed gas volume increases from 25,000 to 29,000, there is a 16% increase, yet the methanol production only increases by 3%, which shows that it’s normal for there to be a mismatch between these two factors. This is due to limitations in the synthesis system’s capacity – the catalysts in the synthesis tower are not compatible with the capabilities of the conversion system. We’ve encountered the same issue before: after exceeding the optimal load, the synthesis efficiency drops, the amount of off-gas increases, and methanol production declines. During shutdowns for maintenance, increasing the amount of catalyst used in the synthesis tower can boost production by up to 15%. However, when the load is increased further, the results are still not ideal. To achieve even higher levels of operation, it would be necessary to use imported catalysts, but this isn’t a complete solution either. If a significant increase in production is desired, then a major overhaul of the synthesis system is required! :handshake
I was referring to the production volume of crude methanol; our normal output is around 47 tons. Sorry, I didn’t make that clear enough
I completely agree with this. I’ll go and check the amount of catalyst loaded in our synthesis tower. I started working this year, in the methanol workshop, and I’m not entirely familiar with some aspects of it. I’m sorry for the inconvenience; thank you all
Hydrogen makes up about 72%, while carbon monoxide and carbon dioxide account for around 10–11%. Methane constitutes about 3–4%, with the remainder being nitrogen. The pressure in our synthesis loop is 8.6 MPa, the flow rate is over 650,000, and the inlet pressure is just over 9 MPa. I’m not quite sure about the concentration of crude methanol; I’ll check that when I get back. Sorry
Let’s go over the key points related to the synthesis reaction. There should be one point regarding the impact of space velocity on this reaction. Think about it: if you double the amount of gas used, will the production volume also double? If so, then the size of the methanol plant would depend solely on the amount of syngas used. When more gas is available, one can increase the amount of off-gas and reduce the amount of gas that is recycled in order to boost production, but there is a limit to this. In your case, 46.5 is probably the upper limit.
In this case, could considering raising the active temperature of the catalyst be an option to increase the yield of crude methane?