Selection of reduction medium for medium-temperature shift catalysts
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Dear colleagues, our company is involved in the production of hydrogen from dry gas. We need to replace the medium-pressure shift catalysts, and during startup, natural gas is used to reduce these catalysts; the reducing gas contains hydrogen and carbon monoxide, while the recycle gas consists of a large amount of hydrogen, 10% carbon monoxide, and 10% carbon dioxide. Is this approach feasible? What are the precautions that should be taken?
For the reduction of medium-temperature catalysts, a high water-to-carbon ratio and a low concentration of carbon monoxide are required, as carbon monoxide is a strong reducing agent that causes a much higher temperature rise during reduction compared to hydrogen. Excessively high concentrations can lead to overheating of the medium-temperature catalyst during reduction. It is recommended to maintain a water-to-carbon ratio of more than 10, keep the pressure in the conversion system at around 0.8 MPa, and determine the optimal reduction temperature and space velocity by consulting the catalyst manufacturer (catalysts from different manufacturers require different reduction temperatures). When there is a tendency toward overheating during reduction (1°C per 5 seconds), it is necessary to immediately cut off the feed material being processed and introduce steam at the inlet of the catalyst to cool it down. I hope it will be useful to everyone.