Effect of rotary valve leakage on pneumatic conveying performance
A new theoretical air leakage model was developed for both conventional and high-pressure rotary valves. Different sizes of rotary valves (D = 250 and 300 mm) and a single-slit apparatus were tested over a wide range of conditions (N = 0 to 30 rpm; Δp v = 0 to 300 kPa; c = 0.10 to 0.25 mm). All the model predictions were found to be within ±6% of the experimental data. This was a dramatic improvement compared with all previous models and even suppliers' curves, where errors were found to be between − 48% and + 39%. A new centrifugal vent hopper also was developed to maximize the removal of air leakage and, hence, feed rate capacity. Based on data from three products (130 µm Poly Powder, fibrous perlite, and 10 µm ground powder), the new vent hopper was found to increase feed rate and conveying capacity by at least a factor of two.