Patent GB-833551-A (GB)
Title: Production of ammonia synthesis feed gas
Inventor: TFORD WILLIAM MALCOLM STRA
IPC: C01B3/02
Filed: 1957-09-06
Abstract: An hydrogen-nitrogen mixture for the synthesis of ammonia is produced by reacting a carbonaceous fuel in at least one first reaction zone with substantially pure oxygen and optionally steam and/or carbon dioxide at a temperature of above 2000 DEG  F. so as to convert the carbonaceous fuel substantially completely to carbon monoxide, separately reacting further carbonaceous fuel with air or oxygen-enriched air and optionally steam and/or carbon dioxide in at least one second reaction zone at a temperature of above 2000 DEG F., preferably 2500-3200 DEG  F., so as to convert the carbonaceous fuel substantially completely to carbon monoxide, combining the effluent from both zones, converting the carbon monoxide in the combined effluent to carbon dioxide by reaction with steam, removing the resulting carbon dioxide together with residual steam and carbon monoxide and adjusting, if necessary, the nitrogen content of the resulting mixture.  The carbonaceous fuel may be a normally gaseous hydrocarbon, e.g. natural gas or coke-oven gas and normally liquid hydrocarbon or coal or coke. The oxygen may be obtained by the rectification of air as a fraction containing more than 95% of oxygen.  The reaction pressure may be atmospheric or as high as 1000 p.s.i.g. and is preferably 200-600 p.s.i.g.  The reactants may be preheated, e.g. to 600 DEG  F. Steam may be preheated to 1200 DEG F., and a gaseous hydrocarbon to 1400 DEG  F.  Solid fuels may have an average diameter of not more than 150 microns, preferably not greater than 40 microns, and are preferably suspended in steam.  The fuel and combustion-supporting gas may be introduced axially into a reactor through concentric tubes at a velocity of 100-200 ft./sec. The carbon monoxide conversion reaction may be effected at a temperature of 750 DEG  F. over a catalyst comprising iron oxide promoted with chromium, potassium, magnesium and aluminium oxide. After conversion, the gas may be scrubbed with water or an amine, e.g. monoethanolamine to remove carbon dioxide, an aqueous solution of cuprous ammonium chloride to remove carbon monoxide, an aqueous solution of sodium hydroxide to remove residual carbon dioxide, and with liquid nitrogen obtained by the rectification of air as a fraction containing more than 99%, preferably more than 99.5% to remove argon, methane and residual carbon monoxide. Nitrogen may be added to or removed from the gas during the liquid nitrogen washing step.  Gaseous nitrogen from the rectification plant may be added to the resulting gas if necessary.  Two reactors employing oxygen and one employing air may be employed (Fig. 1, not shown).  One reactor may be fed with oxygen and a suspension of coal in steam and another with air and an hydrocarbon oil or natural gas and/or a suspension of coal in steam (Fig. 2, not shown).  Four examples are given.  In the examples, the converted gas is cooled to condense water, is scrubbed successively with an aqueous monoethanolamine solution and a 10% sodium hydroxide solution, is further cooled to about 40 DEG  F. to separate further water, is dried to a water content of less than 2 parts per million by passage over alumina, is further cooled, to about - 315 DEG  F. in a heat-exchanger, and is finally contacted in a multiple-plate wash tower with liquid nitrogen at a pressure of 275 p.s.i.g.