CFD simulation and optimization of an industrial cement gas-solid air classifier

An air classifier is one of the main and effective devices in cement industry.In this study,a three-dimensional,steady and two-phase(solid-gas)computational fluid dynamics(CFD)simulation was performed to optimize the performance of this device in the Kerman Momtazan cement plant,Iran.After the validation of CFD results,the air flow field and air path lines between fixed blades were checked carefully and the non-uniformity in velocity distribution and the formation of vortex flows between the blades close to particle inlets were observed.The study tried to improve the device efficiency by changing the method of entering particles into the device,resulting in a reduction in air classifier electrical energy consumption(from 41 to 35(kW h)/t)and an increase in production rate(from 203 to 214 t/h).Additionally,the study investigated the effects of other modifiable operating conditions like rotary cage rotation speed,pressure difference,and inlet air temperature on the particle size distribution and classifier efficiency.The results showed that increasing the cage rotation speed decreased the product rate and the product particles mean diameter while increasing pressure difference or increasing temperature increased the product rate and the product particles mean diameter.It was concluded that these modifiable operating conditions can significantly affect the performance of the air classifier in the cement industry.

Numerical solution of particle size distribution equation:Rapid expansion of supercritical solution(RESS)process

The present study aimed to numerically simulate the rapid expansion of the supercritical solution(RESS)process including particle generation,hydrodynamics,and solving the population balance equation(PBE)to predict the particle-size distribution(PSD)of solid-supercritical carbon dioxide binary systems.Energy,momentum,and mass equations,in addition to the extended generalized Bender equation of state(EoS),were applied to predict the hydrodynamic behavior of a supercritical solution under several operating conditions using a nozzle and expansion vessel.The tetraphenylporphyrin(TBTPP)solubility in supercritical carbon dioxide was calculated using the Peng-Robinson EoS/Kwak-Mansoori as a mixing rule.Subsequently,TBTPP,aspirin,ibuprofen,and salicylic acid nucleation as well as the supersaturation rate were calculated.Finally,we solved the time dependence of the parameters of the size distribution numerically.The established models are compared over a wide parameter range using a reference model that refers to the method of moment log-normal size distribution functions through the RESS process to predict a solid PSD.The results obtained are presented with and without coagulation phenomena.The average absolute percent deviation of solubility of TBTPP was 3.98,and the hydrodynamic behavior of supercritical carbon dioxide showed a similar trend as the results presented in the published research work.Furthermore,a particle size distribution prediction using coagulation showed acceptable agreement with the experimental PSDs.