Raahauge, B.E., Devarajan, N.

FLSmidth has experience with particle breakdown in Gas Suspension Calciners (GSC) over the past 40 years from different hydrate sources calcined in both pilot and full scale Gas Suspension Calciners of various design and capacity. The particle breakdown reported ranges from the low particle breakdown observed in rotary kilns normalized to 100% and upwards. This increase is dependent on hydrate quality/and thus alumina Attrition Index and GSC design and operation. This paper outlines the design changes introduced to minimize the risk of particle breakdown in response to hydrate quality/alumina Attrition Index.

Gas Suspension Calciners (GSC) are designed with four stages of direct heat recovery from hot alumina and this is the most energy efficient heat recovery flow sheet compared to other stationary calciners. Average specific heat consumption below 2700 KJ/kg SGA is reported for GSC units operating with a fluidized holding vessel.

This paper reports analysis of thermal energy consumption of operating GSC units equipped with a fluidized holding vessel providing few minutes of additional retention time. The analysis confirms even lower thermal energy consumption can be achieved for the next generation GSC units by introducing an improved refractory design.