Preheater uses the waste heat of rotary kiln and calciner to heat the raw material in the aim of preheating the raw material and decomposing part of carbonate. The main forms of preheaters are cyclone, shaft, and cyclone-shaft compound preheater. The preheater mainly consists of the cyclone (cylinder, cone, inner cylinder, volute, back mixing cone drop Board), links duct, the discharge pipe and flap valve, sprinkle bins, material clearing holes and temperature and press testing devices.
The main role of the cyclone is to separate the gas and solid. Depending on the inertia of dust powder and centrifugal force produced by the rotation of dust stream, dust is separated from the air. The role of the flap valve is to keep the flowing materials even and smooth, to seal and prevent internal leakage. Hopper spreaders disperse the materials to improve the efficiency of heat transfer and to avoid the short circuit of materials.
The materials are fed from the feeding port, spreading and hanging in the air immediately. Heat transference between gas and solid happens immediately in a high speed. 80% heat happens in the connecting pipe, and only less than 20% happens in the cyclone cylinder. Most parts of the preheater is made by metal, and some parts may be made by heat-resistant steel according to the requirements, and the heat-resistant steel can work under 1000~1100 Celsius degree. Besides, the design of refractory break is much novel with good seal, which can make sure the materials can reach their required temperature in the preheater.
During the whole process of preheating, materials move from top to bottom, and the hot air moves from the bottom to top. Full heat transference happens between materials and the hot air, and part of the waste gas will be discharged from the air outlet of cyclone through discharging pipe.