674082-A is referenced by 259 patents.
674,082. Destructive distillation in situ. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 31, 1950 [June 15, 1949], No. 15989/49. Drawings to Specification. Class 55 (ii). In a system for the underground gasification of coal in which a stream of gasifying medium such as air, air mixed with oxygen, or a mixture of steam and oxygen is passed through a passage in the coal seam, means are provided close to the gasification zone to impart a swirling motion to the gasifying medium so that closer contact between the gasifying medium and the coal face is obtained. The means for imparting the swirling motion may comprise a housing situated at the entrance to the gasification zone and having a number of radially arranged vanes which are set at a suitable angle. In a modification the vanes may be rotated or a number of suitably designed nozzles may be used.