Residual liquid from methanol-to-hydrogen process is high
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For methanol-to-hydrogen production, the catalyst with a capacity of 12,000 cubic meters per year was used for only 10 months; the concentration of methanol residues increased from around 7% to around 15%. The catalyst was designed to last 48 months. Currently, the feed rate is 9,500 kg/h for acidic water (the design value is over 10,000 kg/h), and 4,500 kg/h for methanol (the design value is 6,300 kg/h). During operation, there were 5 instances of unplanned shutdowns. I would appreciate it if experts could analyze the reasons for this.
First, rule out the possibility that impurities in the raw materials are poisoning the catalyst, and then rule out the cause of catalyst pulverization due to abnormal start-up and shutdown operations.
Is the process methanol steam cracking conversion?
Yes, we contacted the catalyst manufacturer, and he said there was no issue with the catalyst’s activity.
This post was last edited by huwei19890613 on 2018-3-7 08:22. If it’s a domestic catalyst, a design life of 48 months seems a bit exaggerated. Additionally, it appears that there are frequent abnormal shutdowns during operation, which also has an impact on the catalyst. An increase in the concentration of methanol residues indicates a decline in catalyst performance; increasing the temperature of the heat transfer oil may help to address this issue. The most important aspect of a methanol cracking catalyst is its reduction capability. After the reduction process is complete, it is necessary to operate the catalyst at a low load for a period of time before increasing the load again, and then evaluate the catalyst’s performance at full load (key points: 1. Residual concentration at 1%–50% load levels) ； 2. Minimum reaction temperature). If the concentration of methanol residue is also low at a relatively low reaction temperature, it indicates that the catalyst is effective. The lifespan of the catalyst is also related to the operating conditions during normal use; factors such as frequent improper operations, abnormal shutdowns, and high levels of toxic substances in the feedstock can all reduce the catalyst’s lifespan. Another issue is the control of reaction temperature. Some facilities strive too much for high conversion rates and set the initial reaction temperature quite high; this is actually a serious mistake, as it accelerates the aging and deactivation of the catalyst, reduces the range within which the temperature can be increased, and in effect **shortens the catalyst’s lifespan**. The correct approach is to choose a relatively low reaction temperature at the beginning, and to monitor the trend in the increase of residual liquid concentration (with constant load). As operation time progresses, the reaction temperature should be increased gradually, in small steps.
Thank you, I’ve learned something. It seems we have all the factors you mentioned that affect catalyst activity; I was wrong earlier – the design life of the catalyst is 2 years, or 24 months.
Two years is more in line with reality, but with proper handling, it’s possible to use it for three years as well, based on my experience. The restoration process and normal operating procedures are very important; in particular, the restoration process is crucial. If problems such as catalyst pulverization or reduced performance are detected during this process, it becomes difficult to improve the situation through normal operations, ultimately leading to a vicious cycle.
May I ask under what circumstances a reduction process occurs? What is the appearance of our methanol? Its purity is 99.98%, the potassium permanganate treatment time is >50 minutes, and what is the sulfur content?
It is you who, at the initial stage of startup, carry out the reduction process of the catalyst, converting it from its oxidized state to its active form~~
Thank you, I see. I started working with methanol-based hydrogen production quite late in my career, and your explanation has been extremely helpful to me.
Where are your catalysts from? Catalyst manufacturers generally do not admit that there is a problem with their catalysts. I used to operate a set of methanol cracking units, and once the catalyst reduction process was complete, I noticed that the catalyst had begun to powder up; catalyst particles were present in the effluent from the scrubber tower. At first they were red in color, but after a while they turned black – this was due to the oxidation of copper in its reduced state. I heard that the last batch of catalysts was scrapped after less than a year of use.