Controlling the temperatures during the calcination of aluminum hydroxide in rotary kilns

Abstract

Processing 4.1 to 4.2 tons of nepheline concentrate mixed with limestone produces 1 t of alumina, 0.8 t of sodium carbonate, 0.3 t of potash, and 10 tons of cement. The costs of producing these from nepheline are significantly lower than the costs of individual production from conventional raw materials by conventional technology. Unlike the traditional ammonia-based method, the nepheline technology of producing soda ash is environmentally friendly and does not require costly sludge fields. Using belite sludge as the raw material for making cement improves the performance of kilns and reduces the fuel consumption by over 40% compared to the conventional technology. Making alumina with a specific content of α-Al2O3 and γ-Al2O3 requires an automated process control system (APCS). In an industrial setting, only automatic controls enable maintaining a technologically healthy process. This paper presents a summary of the aluminum hydroxide calcination process that occurs in tubular rotary kilns. The research team has synthesized a dynamic control object model to plot curves of the target-parameter acceleration as induced by stepwise disturbances in air flow, charge flow, and fuel flow in order to compute the basic dynamic characteristics of the control object. A control parameter has been selected for the prospective single-loop control system. On the basis of the obtained characteristics, the research team has selected a controller for their single-loop kiln temperature stabilization system. The paper presents curves of the control-channel and disturbance-channel transients in the target parameter