Comparison of low-pressure methanol synthesis technologies between I.C.I. in the UK and Lurgi in Germany

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The British company I.C.I. and the German company Lurgi are representatives of low-pressure methanol synthesis technology. The main difference between these two low-pressure methods lies in the type of methanol synthesis reactor and the way in which reaction heat is recovered. The I.C.I reactor is of multi-stage quench type, featuring a simple structure and high production capacity per tower. However, since the various sections of the catalyst bed undergo adiabatic reactions, a large temperature difference exists within the catalyst bed; as a result, the axial temperature distribution throughout the reactor is serrated. This leads to an abundance of reaction by-products, a shorter service life for the catalyst, and high compression energy costs for the recycle gas. Moreover, the reaction heat can only be recovered as low-pressure steam using a low-pressure waste boiler at the reactor outlet. The Lurgi reactor is similar to a vertical shell-and-tube heat exchanger with fixed tube sheets; a catalyst is placed inside the tubes, while medium-pressure boiling water surrounds them to absorb the heat generated by the reaction. It has a more complex structure than I.C.I reactors, but its main advantages are a small temperature difference across the catalyst bed, a high one-pass conversion rate, less formation of impurities, low energy consumption for compression during circulation. Moreover, the synthetic reaction generates medium-pressure steam as a by-product, facilitating the comprehensive utilization of waste heat. Among the world’s methanol plants, those using the Lurgi process or processes similar to it account for over 70%. The methanol plants under construction also mainly use Lurgi processes or processes similar to the Lurgi process.