Utilization of Brackish Water in Coal Gasification.

摘要

When coal is utilized for production of synthetic natural gas,approximately 11,000acre feet a year will be required for the daily production of 300million cubic feet (STP) of gas. A major advance would occur in gasification development if part of the required water could be supplied from brackish water sources. The main consideration in the use of brackish water as process water is the deposition of the salts from the brackish water. Three salt systems supplied from a synthetic saline solution were analyzed for salt deposition during the gasification of a coal-salt solution paste. The salts studied were sodium chloride,potassium chloride,and sodium sulfate. The study examined the leachability of these salts from the product coal-ash;most of the salts introduced into the reactor system were leachable either from the product mixture or from the reaction vessel. The salt material balance could be closed by accounting for salts carried from the system either as mist or as particulate. While not a definite deterrent to the use of brackish water in an in-situ gasification process,the leaching of these salts into ground water and subsequent deterioration of the ground water aquifer would have to be considered. In the case of the Lurgi reactor system,brackish water could not be used until corrosion considerations had been examined. Conclusions were:Common brackish water salts are leachable from the spent reaction zone products in a packed bed gasification reactor. Ash fusion may occur at temperatures well below expected high silica ash fusion points. Potential damage to aquifers could result from salt migration from a spent in-situ reaction bed. In a packed bed reactor salts tend to migrate out the bed interior to the reactor wall.