Coal chemical conversion processes and catalyst selection
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The conversion section is a crucial step in the processes of ammonia synthesis and methanol production; the choice of process and catalysts is important for long-term operation and energy savings. There are roughly three types of conversion processes available today: full low conversion, medium-high and low conversion (two stages of medium conversion and one stage of low conversion), and medium-low-low conversion (two stages of medium conversion and two stages of low conversion). For gas production using companies such as Texaco and Shell, the pressure is high, the ratio of gas to water vapor is large, the sulfur content is high, and the carbon monoxide content is also high; this requires catalysts of high quality, and full low-temperature shift processes are commonly used, with wide-temperature shift catalysts being employed ； For fixed-bed batch gas production systems with a shift system pressure of 2.0 MPa or less, all three shift processes are employed due to the oxygen content in the gas; currently, medium-low and low-pressure shift processes are more common. For full-low-pressure shift, an oxygen scavenger must be used, while for low-pressure shift processes, ordinary spherical sulfur-resistant shift catalysts suffice. Both the technology and the products involved are well-developed ； The most controversial option at present is the fixed-bed batch gas production process with a shift system pressure of over 2.0 MPa; if a medium-high-temperature shift process is used, the selection and application of catalysts are somewhat better, but pressure and peak temperature still need to be taken into consideration. If the fully low-temperature shift process is adopted, many problems arise; some use spherical sulfur-resistant shift catalysts, while others use strip-shaped wide-temperature sulfur-resistant shift catalysts. When spherical sulfur-resistant shift catalysts are used, there are issues such as high hotspot temperatures, short catalyst life, high bed resistance, and stringent requirements for production; I am opposed to this approach. I prefer the use of strip-shaped wide-temperature sulfur-resistant shift catalysts, as although they are more expensive and require higher initial investment, their service life is longer. Fluctuations and start-up/shutdown during the production process have little impact on the catalyst. Luhua is an example. I’m just sharing my own opinions; I welcome any criticism and suggestions.
The QCS series of sulfur-resistant shift catalysts were developed by the Qilu Petrochemical Research Institute. Currently, Professor Zhang has moved to Shandong University of Science and Technology, Professor Zong has retired but is serving as an adjunct professor at Qingdao University of Science and Technology, and Professor Zhou has gone to China University of Petroleum. As a result, the Qilu Petrochemical Research Institute no longer has technical support and has essentially withdrawn from the market. QDB is a series of sulfur-resistant shift catalysts developed by Professor Zong from the former Qilu Petrochemical Research Institute in collaboration with Qingdao University of Science and Technology; it now holds an 80% market share. In recent years, companies such as Texaco, Shell, and those involved in the production of gas using space furnace technology have all ordered these catalysts from them. K811 was originally imported from abroad; now it is entirely produced in Qingdao. After Manager Gao, who was responsible for its production at the Qilu Petrochemical Research Institute, retired, it was developed in collaboration with foreign companies based in Shanghai. Currently, it has the highest market share in the high-pressure conversion sector. There are also many manufacturers of low-pressure conversion catalysts; the technology used is mainly based on B303 developed by Hubei Institute of Chemistry. As the technical staff from this institute start their own businesses, such manufacturers have emerged in large numbers.