Reasons for excessive temperature rise during high-hydrogen reduction of catalysts in medium-pressure methanol plants
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Medium-pressure methanol plants often experience runaway temperatures during high-hydrogen reduction of catalysts. What are the causes of these runaway temperatures and what are the preventive measures?
Some medium-pressure methanol units serve as purification methods for ammonia synthesis; they utilize methanol and methane technologies (or methanol and hydrocarbonation) to separate carbon monoxide and carbon dioxide from the process gas, thereby meeting the requirements of the ammonia synthesis process regarding these gases. And these enterprises often lack air separation units and thus no nitrogen. High-hydrogen process gas is used directly during temperature-raising reduction.
In some companies, using high-hydrogen process gas for pressure testing often also leads to excessive temperature rise.
To prevent overheating, low-hydrogen reduction is used during the reduction of medium-pressure methanol catalysts; if nitrogen is not available, liquid nitrogen is purchased.
Another theory is that increasing the physical water content of the medium-pressure methanol catalyst can also resolve the issue of excessive temperature rise. Everyone is welcome to discuss.
The reduction over-temperature is caused by improper hydrogen supply control: hydrogen is added continuously, temperature and hydrogen supply are increased simultaneously, and the circulation volume is low.
It is true that the circulation rate of medium-pressure devices is low, and low-hydrogen reduction is the most effective measure.
With a low circulation rate, the reduction pressure should be increased slightly; unstable control of the high-pressure hydrogen flow rate may cause uneven distribution at the initial stage, leading to overheating.