Lurgi process control

If air (or oxygen) and steam are both passed through a high-temperature bed of coal or coke these reactions can be balanced, thus controlling the bed temperature and the fusion of the ash. In the higher pressure Lurgi process the gas obtained is high in methane, formed in reactions such as... 

In order to control heat removal and therefore the catalyst temperature, multiple-tube reactors (Lurgi process) or quench reactors with several catalyst layers and introduction of cold gas (ICI process) are mainly used. Catalyst performance in modern larger reactors is 1.3-1.5 kg of methanol per liter per hour, and large-scale plants have capacities of up to 10 fra, which reflects the position of methanol as a key product of Ci chemistry. 

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. 

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. 

Hydrosulfreen A process for removing sulfur compounds from the tail gas from the Claus process. It combines the Sulfreen process with an upstream hydrolysis/oxidation stage, which improves efficiency and optimizes the emission control. Developed jointly by Lurgi and Societe National Elf Aquitaine, and installed in 1990 in the Mazovian Refining and Petrochemical Works, near Warsaw, Poland. See also Oxysulfreen. 

Tail gas emissions are controlled by improving the S02 conversion efficiency and by scrubbing the tail gas. In a double absorption process plant, a five-bed converter has 0.3 percent unconverted S02, as compared with 0.5 percent for a four-bed converter. A Lurgi Peracidox scrubber may be used to remove up to 90 percent of the residual S02 in the tail gas from a double absorption plant. Hydrogen peroxide or electrolytically produced peroxymonosulfuric acid is used to convert the S02 to H2S04 in the Lurgi scrubber. 

Similar to the Lurgi FBDB process, the control of the BGL gasifier is comparatively easy Care must be taken to keep the reactor full of coal, which is enough for 0.5-1 h of operation or on a constant level in the case of short-bed operation. As coal feeding is accomplished automatically, only the gasifying agent quantity and composition remain to be controlled. 

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