GB980952A - Improvements in or relating to methods of cleaning gases - Google Patents

Abstract

A method of removing droplets, mist and dust particles from a gas-vapour mixture, e.g. one produced by the gasification of liquid and/or solid fuels with an oxygen-containing gas, comprises cooling the gas to below the dew point of contained hydrocarbons, e.g. to 15 DEG C. at 20 atmos. gauge, separating condensate and dust from the gas in a conventional separator, heating the gas through 20 DEG to 50 DEG C. at constant pressure, e.g. indirectly by heat exchange and removing remaining condensates and dust in a second separation stage. The separators may be conventional impingement apparatus and/or filter beds of catalytic or surface-active agents, and the heating stage should be so controlled that higher boiling hydrocarbons do not have time to evaporate, and may thus be removed in the second stage. Lower boiling hydrocarbons are evaporated and pass through the apparatus to subsequent process stages, e.g. for carbon monoxide conversion with entrained steam. The method is intended to prevent corrosion and incrustation of heat exchangers &c. through which the gas is to be passed, by liquids which, due to initial undercooling, escaped the first separator. In an example, a crude gas containing inter alia H2, CO2, and CO is cooled to 180 DEG C. by trickling water to remove tar and dust, passage through the first separator removing mist and more dust. The partly cleaned gas is heated to 210 DEG C. and passed through the second separator to remove further liquids and dust, and then heated to 350 DEG C. for CO conversion. The hot converted gas provides the heat both heating the cleaned gas for conversion and for the heating stage.