Experimental Investigation into Wall Deposition of Milk Powder in Spray Dryers

This is the authors' abstract. We don't add key points for this paper.

The effect of varying the inlet air swirl, inlet air temperature and liquid feed flowrate on the wall deposition flux of skim milk powder has been investigated in a small‐scale, co‐current spray dryer. The spray dyer was a cylinder‐on‐cone unit with diameter 0.8 m and height 2 m, fitted with adjustable swirl vanes surrounding a Delavan GAI two‐fluid atomizer. In this work, swirl vane angles of 0d̀, 25d̀, and 30d̀, inlet air temperatures of 170d̀C, 200d̀C, and 230d̀C, and feed flowrates of 1.4 kg h.−1, 1.6 kg h−1′ and 1.8 kg h−1 were used. The wall deposition flux was found to be significantly influenced by inlet air swirl, with the highest swirl vane angle of 30d̀ giving rise to the highest wall deposition flux of 13 g m−2 h−1. For the skim milk powder, the difference between the particle temperature and sticky‐point temperature was also found to be important in influencing the wall deposition flux. When the outlet particle temperature was furthest above the sticky‐point temperature and the inlet air temperature was lowest ( 170d̀C), then the wall deposition flux was the highest at 16 g m−2 h−1. It is likely that cohesion is the critical process in the wall deposition of milk powder. The effect of grounding the dryer on the deposition flux did not appear to be very significant. The measured deposition rates appear to be representative of those in industrial equipment.