During the beneficiation process, a rotary kiln is used to magnetize and roast the lean iron ore, so that the original weak magnetism of the ore is changed to strong magnetism to facilitate magnetic separation. In the chemical industry, rotary kiln is used to produce soda, and active lime manufacturers calcine phosphate fertilizer and barium sulfide. In the 1960s, LapPle and others invented a new process for producing phosphoric acid in a rotary kiln. This method has the advantages of low energy consumption, low power consumption, no sulfuric acid, and the use of low- and medium-grade phosphate ore, and it is quickly popularized. In addition, in terms of environmental protection, developed countries in the world have used cement kilns to incinerate hazardous wastes and garbage for more than 20 years. This not only reduces waste and harms it, but also uses waste as fuel to save coal powder and achieve Recycling of waste.