99/00843 Recovery and utilization of waste liquids in ultra-clean coal preparation by chemical leaching

Abstract

Coal with ash lower than 1%, being called an ultra-clean coal, has many potential applications, such as a substitute for diesel fuel, production of carbon electrodes, superior activated carbon and other chemical materials. It is difficult to reduce coal ash to such a level by conventional coal preparation technology. By means of chemical leaching with the proper concentration of alkali and acid solutions, any coal can be deeply deashed to 1% ash level. However, the cost of chemical methods is higher than that of physical ones, additionally, the waste liquids would give rise to environmental pollution if used on a large scale. If the waste liquids from chemical preparation of ultra-clean coal can be recovered and utilized, so as to produce salable by-products, the cost of chemical leaching will be reduced. This processing will also solve the pollution problem of these waste liquids. This paper describes recovery and utilization methods for these liquids used in chemical leaching, including the recoveries of alkali, silica, sodium-salt and aluminium-salt. A preliminary estimate was made regarding its economic benefits. It shows that this research solves the two problems in the chemical preparation of ultra-clean coal. One is the high-cost and the other is environmentalmore » pollution. This research demonstrates good potential for the production of ultra-clean coal on an industrial scale.« less