Outline of Ishikawajima-Harima Heavy Industry -- Suspension-Heater Flash-Furnace Clinker Burning Process

The suspension-preheater flash-furnace (SF) process for cement clinkering introduces a calcining flash furnace operating as an integral portion of a suspension preheater, rotary kiln, and clinker cooler system. Preheated raw meal from the suspension preheater is calcined in the flash furnace to 80 to 90 percent decarbonation. The capacity of the SF rotary kiln is increased thereby, since its function is limited to sintering rather than sintering and calcining. The flash furnace incorporates vortex flow to accomplish the mixing of fuel, raw meal, and gases. Effective distribution within the flash furnace limits temperature gradients and eliminates localized elevated temperatures that might otherwise lead to coating and material build-up. Hot combustion gases are recovered from the clinker cooler for use in the flash furnace. An orifice in the kiln gas exit duct serves to balance the parallel gas flows through the kiln and secondary air duct. Operating pressures and temperatures are described. The smaller size of the rotary kiln used in the SF process leads to extended refractory life as demonstrated by operating experience. The SF process is adaptable to the control of internal alkali, sulfur, and chlorine cycles through a gas bypass and through a unique material withdrawal arrangement from the flash furnace. Existing plants may be modified to incorporate the SF process. Nearly 20 commercial scale plants are operating or are being constructed.