The condensate from the methanol cracking hydrogen production process contains too much methanol
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We produce hydrogen through methanol catalytic cracking, and the reflux condensate collected by the water scrubber contains too high a concentration of methanol. It was usually around 10 percent, and after one year it rose to over 40 percent; I suspect the catalyst’s activity is poor. I replaced it recently, but it stopped working again after just one month. Tests showed that there are no problems with the raw materials, methanol and water. What other possible influencing factors are there?
What is your raw material ratio? Measure the specific gravity of the residual liquid in the water cooler; if it’s normal, it’s likely that your feed rate is too high!
The alcohol-to-water ratio is not appropriate, and there is a certain discrepancy between theory and practice. The difference here is that the liquid coming out of the wash tower has a higher acidity level; we’re not sure how to adjust it
If there’s nothing wrong with your catalyst, it’s likely that the feed ratio is not appropriate. We currently keep the methanol mass fraction between 45% and 47%, with the hydrogen content in the pyrolysis product ranging from 70% to 72%. The methanol content in the residue is around 2%.
I think it might be because the amount of water used for washing is insufficient. Insufficient washing water leads to an increase in the methanol content in the reflux liquid, and this increased reflux liquid returns to the demineralized water tank, raising the methanol concentration in that tank. As a result, the methanol concentration in the feed mixture also increases, which in turn raises the methanol content in the pyrolysis gas. This creates a vicious cycle: an increase in methanol content leads to catalyst failure
If it’s a new catalyst, there should be no problem; what needs to be checked is whether the ratio of the feed materials falls within the designed range. In China, the mass fraction of methanol is generally kept between 45% and 47%, and the feed volume should correspond to the designed capacity. Secondly, it’s important that there is enough washing water. To find out the cause, start by reducing the feed volume to see if that helps to resolve the issue.
How is methanol wash water recovered? For example: Water contains large amounts of methanol, and this methanol needs to be recovered. How do you handle that? What are the steam consumption and cooling water consumption of your on-site methanol recovery tower? What is the reflux ratio of the tower? What is the number of trays? Where is the feed tray? What are the feeding conditions? What are the conditions at the top and bottom of the tower? Thank you
On the hardware side, it’s necessary to check whether the check valve in the raw material liquid tank (recovery condensate tank) is stuck; I’m not sure if your process is the same as mine
The new catalyst will not have this problem. Also, consider your feed ratio, the cleanliness of the wash tower packing, and check whether there are any leaks in the heat transfer oil system
In fact, catalysts used for hydrogen production through methanol cracking are very fragile; substances such as Cl, F, and S are toxic to these catalysts, and even concentrations in the ppm range can render them inactive, with that inactivity lasting only a few hours. It’s useless to check the raw materials after poisoning has occurred; it is recommended to analyze the Cl and S contents in the catalyst. F is difficult to analyze. PS: If methanol makes up 10% of the normal condensate, is there anything abnormal during the catalyst activation process, such as temperature fluctuations? Could you tell me about your reduction procedure, the heating process, and the amount of reducing agent used? roberhu@qq.com