An CFD approach to reduce the risk of wall deposition in the milk powder process

The spray drying process stands out in the food industry due to the diversity of desired powder products with long life-storage. During operation, a spray dryer might suffer powder deposition on the walls in response to unexpected changes in the operative conditions and the liquid properties. The literature has analyzed this problem through experimental and theoretical studies and not by considering the geometrical changes of the equipment. This theoretical study applies CFD simulation for the milk powder process in order to predict the risk of wall deposition under diverse geometrical designs. In this approach, the typical CFD methodology applied discrete phase simulation and quantified the risk of wall deposition in the baseline case. Thus, this proposal modified the geometry by rotating the hot air inlet duct and including air sweeping feeds to determine a suitable geometrical design with a low risk of wall deposition. The results presented acceptable geometrical proposals with a reduction of around 75 % of the risk of wall deposition with respect to the baseline case, and otherwise some geometrical proposals with an increment of around 20 %. These results indicated the influence of the geometrical design on the flow pattern inside the chamber, where the hot air inlet duct position in parallel with the outlet distributor duct is convenient to reduce flow instabilities. This study demonstrated the possibility of reducing the risk of wall deposition by design where the low turbulence level is adequate in correspondence with the swirl intensity.