Development and perspective of the technologies for desulfurization of coal before combustion

Coal occupies a dominant position in energy consumption in China. Yet combustion of coal is liable to cause environmental pollution. To vigorously develop clean coal technology is therefore of vital importance. The paper presents an overview of the related technical means for desulfurization of coal before combustion. These include mainly the physical, chemical, physiochemical and biological methods. Among them, the physical method, a widely applied mature and cost-effective technology, is mainly used for removal of inorganic sulfur, but for the removal of organic sulfur, its effect is limited. The physiochemical method is suitable for the treatment of coal with a high content of inorganic sulfur because it is only effective for removal of such sulfur, but it can hardly produce any effect in removal of organic sulfur. The chemical method can be used for the removal of both inorganic and organic sulfur, but its use can affect the structure of coal. The use of some temperate chemical desulfurization methods such as microwave radiation and ultrasonic-electrochemical flotation methods can produce a good desulfurization result with but little adverse effect on coal structure. The biological method, though effective for removal of both organic and inorganic sulfur, needs to have an extended processing time, and only few kinds of flora suitable for desulfurization are currently available. Result of analysis indicates that most of the inorganic sulfur can be effectively removed using either physical or physiochemical method while for the removal of organic sulfur, the chemical or biological method is the only option; and as the biological method needs a relatively long treatment cycle, it is advisable to remove the organic sulfur using some less-intense chemical methods. It is pointed out that endeavors should be made in the future to tackling the key technologies for desulfurization of coal prior to its combustion on the basis of the technologies presently available while making the technologies for desulfurization of coal during and after combustion as auxiliary means, so as to realize clean and high-efficiency utilization of coal.