Patent GB-852072-A (GB)
Title: Production of hydrogen cyanide
IPC: C01C3/02
Filed: 1957-07-18
Abstract: <PICT:0852072/IV(b)/1> Acetylene together with HCN is produced by the combustion of a saturated, normally gaseous hydrocarbon, a free oxygen-containing gas and gaseous ammonia in a combustion zone from which the combustion products pass through contiguous convergent and divergent zones, the ratio of absolute pressure in the combustion zone to that at the point of exhaust from the divergent zone being between 2:1 and 10:1.  Passage of the combustion gases through the convergent and divergent zones results in a rapid rate of cooling e.g. of the order 2 X 108 DEG C. free to temperatures below the decomposition temperature of HCN.  Ethane, propane, natural gas or preferably methane may be employed as the gaseous hydrocarbon. Pressures of 18-40 p.s.i.g. in the combustion zone and atmospheric pressure in the divergent zone may be employed with pressures of 25-32 p.s.i.g. in the combustion zone exhausting to atmospheric in the divergent zone, i.e. a pressure ratio of 2,7:1 to 3,1:1 being preferred.  Methane and preferably preheated oxygen are used in volume ratio of 0,5:1 to 1,6:1 preferably 0,7:1 to 1,3:1 but advantageously less than 1:1, with an amount of ammonia not greater than the carbon requirement of the methane.  By decreasing the proportion of ammonia in the gas mixture the amount of acetylene in the combustion products may be increased.  Methane, ammonia gas and free oxygen are introduced into the combustion zone 5 of the refractory, lined steel reactor, 6 through 10.  The refractory lining may be alumina or silicon carbide.  Combustion is initiated by electric spark at 8 and the rates of flow regulated to keep the flame within the combustion zone at 1200-1500 DEG C.  Products pass through the convergent zone 11 and throat 12 to the divergent zone 13 and are exhausted at 14 where expansion causes cooling.  In example (1) a premixed methane/ammonia stream impinges on an oxygen stream in the combustion chamber.  Specification 794,157 is referred to.ALSO:<PICT:0852072/III/1> HCN is produced by the combustion of a saturated, normally gaseous hydrocarbon, a free oxygen - containing gas and gaseous ammonia in a combustion zone from which the combustion products pass through contiguous, convergent and divergent zones, the ratio of absolute pressure in the combustion zone to that at the point of exhaust from the divergent zone being between 2:1 and 10:1.  Passage of the combustion gases through the convergent and divergent zones results in a rapid rate of cooling e.g. 2 X 108 DEG C./second to temperatures below the decomposition temperature of HCN. Ethane, propane, natural gas or preferably methane may be employed as the gaseous hydrocarbon.  Pressures of 18-40 p.s.i.g. in the combustion zone and atmospheric pressure in the divergent zone may be employed with pressures of 25-32 p.s.i.g. in the combustion zone exhausting to atmospheric in the divergent zone i.e. a pressure ratio of 2.7:1 to 3.1:1 being preferred.  Methane and preferably preheated oxygen are used in volume ratio of 0.5:1 to 1.6:1 preferably 0.7:1 to 1.3:1 but advantageously less than 1:1. Methane, ammonia gas and free oxygen are introduced into the combustion zone 5 of the refractory-lined steel reactor, 6 through 10.  The refractory lining may be alumina or silicon carbide. Combustion is initiated by electric sparks at 8 and the rates of flow regulated to keep the flame within the combustion zone at 1200-1500 DEG C.  Products pass through the convergent zone 11 and throat 12 to the divergent zone 13 and are exhausted at 14 where expansion causes cooling.  In Example (1) a premixed methane/ammonia stream impinges on an oxygen stream in the combustion chamber.  Specification 794,157 is referred to.