In the chemical industry, rotary kiln is used to produce soda, calcined phosphate fertilizer, barium sulfide, etc. 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 price of active lime for active lime manufacturers, low sulfuric acid, and the use of low- and medium-grade phosphate ore, and it has been quickly promoted. 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.