Lurgi recycle operation

Lurgi Recycle Operation for High Gasoline Production... 

The chapter by Eisenlohr et al. deals with the results of large scale pilot operations using a newly developed high-nickel catalyst with hot-gas recycle for temperature control. This and other work, conducted by Lurgi Mineraloeltechnik GmbH, with South African Coal and Oil Limited (SASOL), are the bases of the methanation process which Lurgi is proposing for commercial plants. 

This catalyst is preferably reduced in the synthesis unit with hydrogen at 250-350° C. for 1-4 hours. The rate of hydrogen flow is 1 cubic meter/kg. cataJyst/hour. Reduction with synthesis gas is possible. Synthesis is started at about 180° C., and the temperature is raised to 220° C. in 2 days. The operating pressure was 20 atmospheres. The space velocity (volumes of gas per volume of catalyst per hour) of fresh gas is 100, of recycle gas 300, and the tail-gas volume is 48% of the fresh-gas volume. Over an operating period of 3 months, the temperature is raised from 220 to 230° C. This catalyst has not been run to exhaustion by Lurgi, but it is believed that its life would be about 1 year. Other conditions of the operation and yields are shown in Table VI. 

The Lurgi process is a famous example of a process operating with an isothermal single-bed reactor (50-100 bar, 230-265 °C, copper catalyst). The catalyst is contained in fixed tubes and the tubes are cooled by a continuous boiling water flow. The temperature of the water is controlled by a steam pressure control valve that is adjusted to the pressure corresponding to the set-point temperature in the reactor. The reactor can achieve high syngas conversions and, therefore, the recycle ratio is low. 

Lurgi CFB Process. In this SO2 removal process, hydrated lime is injected into a circulating fluid bed (CFB) reactor located ahead of the particulate removal system. Water is also injected into the reactor to cool and humidify the gas and increase the SO2 removal efficiency. A mixture of fly ash and reacted and unieacted sorbent particulate in the gas from the CFB reactor is collected in a special downstream mechanical dust collector curtain followed by an ESP. Most of the collected particulate is recycled to the CFB reactor (Keetii et al., 1991B). In 1993, eight systems of this type were operating or were under construction in Europe, and two were under construction in the U.S. (Moore, 1993B). 

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