The common methods for desulfurization taken at home and abroad can be divided into three kinds of methods of desulfurization before combustion,  desulfurization during combustion and desulfurization after combustion. The method of desulfurization before combustion refers to that the coal washing technology is used for coal washing and separating, in order to wash away most of the combustible inorganic sulfur in coal and reduce the sulfur content in the burning of coal, so as to achieve the purpose of reducing pollution. The method of desulfurization during combustion (desulfurization in boiler) refers to that during combustion of pulverized coal, at the same time feed a certain amount of desulfurizer in order to remove the sulfur dioxide during combustion. Typical technology is circulating fluidized bed technology. The method of desulfurization after combustion (flue gas desulfurization) refers to that equipping the desulfurization equipment outside the flue to desulphurize the flue. The typical technologies are limestone-gypsum method, spray drying method, electron beam method and ammonia method etc.. The technology of flue gas desulfurization is the only desulfurization method applied in commerce on a large scale in the world. The desulfurization technology in more than 90% of the coal-fired power plants at home and abroad lags behind, because the limestone-gypsum method is adopted.