Utilization of Brackish Water in Coal Gasification

One of the major problems in the development of western coal is the availability of the water necessary for processing the coal. When coal is utilized for production of synthetic natural gas, approximately 11,000 acre feet a year will be required for the daily production of 300 million cubic feet (STP) of gas. While the gasification reactions do not consume all this water, 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. This study examined salt deposition in the gasification reaction system.

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 consisted of examining the leach ability of these salts from the product coal-ash. It was found that 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 will have to be considered.In the case of the Lurgi reactor system, brackish water could not be used until corrosion considerations had been examined.

PROJECT NO. A-051-NMEX