GB903930A - Improvements in or relating to processes for the continuous production of combustible gases - Google Patents

Abstract

In a continuous process for the production of a combustible gas, such as fuel gas, synthesis gas and hydrogen from carbonaceous materials, particularly liquid and gaseous hydrocarbons and coal, by reacting them with oxygen or oxygen and steam the hot raw gas is first cooled and then passed in turn through one or more beds, preferably fluidized, of particulate iron and/or manganese oxide maintained at a temperature between 250 DEG and 700 DEG C., preferably between 400 DEG and 600 DEG C., to effect removal of hydrogen sulphide and other sulphur-containing impurities and some conversion of carbon monoxide by reaction with the water vapour present in the gas to carbon dioxide and hydrogen, and through a scrubber where it is scrubbed with an absorbent liquid to remove carbon di-oxide, oxide particles and liquid absorbent being withdrawn from the bed or beds of oxide and the scrubber respectively, regenerated and returned thereto. Three fluidized beds of hot oxide particles arranged one above the other in a single vessel may be employed and steam or condensate may be fed into spaces between the lowest and middle bed and the middle and upper bed. Oxide for regeneration is continuously withdrawn from the bed, or bottom bed and regenerated in a preferably fluidized regeneration zone maintained at a temperature between 400 DEG and 800 DEG C. by contact with air or a mixture of air and hot combustion gases whereby sulphur di-oxide is liberated and the oxide regenerated. The liquid absorbent for carbon di-oxide may be ethanolamine or an aqueous solution of potassium carbonate and regeneration of the used absorbent is effected by steam stripping in a column at a pressure somewhat lower than the pressure in the scrubber. The absorbent being regenerated is withdrawn from a lower portion of the column and heated in a reboiler to provide the steam for stripping and the heated absorbent is fed from the reboiler into the base of the regeneration column to release steam before return to the scrubber. Carbon di-oxide is recovered from the regeneration column. The hot raw gas may be quenched by direct contact with water or cooled by passage through a waste-heat boiler and may be washed with hot water before entry into the bed or beds of oxide. The gas leaving the bed or beds of hot oxide particles may be further treated to reduce its carbon monoxide content. The gas is washed with hot water and passed into a converter containing beds of iron oxide maintained at between 400 DEG and 550 DEG C. wherein most of the remaining carbon monoxide is converted. Steam or condensate may be introduced into the converter. The gas from the converter is then washed to remove carbon di-oxide. Also the gas may be washed to remove carbon di-oxide before entering the converter and the absorbent liquid from both washings may be regenerated in a single regeneration column or each scrubber may be combined with a separate regeneration column.