The Effect of Liquid Application Time and Wet Mix Time with Different Mixer Types on Uniformity of Mix

Liquid addition systems are often designed to add liquid ingredients with the shortest application time in order to increase the batching capacity of the mixing process. The quantity of liquid that is added into the mixer affects the batch cycle time, particularly when there is a programmed “wet mix” time or mixing time after liquid application. A shorter application time of liquids typically produces a larger droplet size, which may lead to greater clumping tendencies in the feed and less uniformity of liquid incorporation. Three experiments were conducted to determine the effect of liquid application time and wet mix time on the uniformity of mix with different mixer types. A 230 g/kg NaCl solution was used as a marker to determine mix uniformity. Experiment 1 and 2 treatments were arranged in a 2 × 3 factorial. Experiment 1 treatments were liquid application time (20 and 30s) and wet mix time (15, 30 and 45s) to determine the effect of liquid addition on uniformity of mix using a double ribbon mixer. Experiment 2 treatments were liquid application time (15 and 30s) and wet mix time (10, 20 and 30s) to determine the effect of liquid addition on uniformity of mix using a paddle mixer. Experiment 3 treatments were arranged as a completely randomized design to determine the effect of wet mix time (15, 30 and 45s) on uniformity of mix using a twin shaft counterpoise mixer. There were 3 replicates per treatment and 10 samples per replicate for all experiments. The results of Experiment 1 indicated that wet mix time had a greater effect on percent coefficient of variation (%CV) than application time (P<0.0001 and P=0.6530, respectively) when a 230 g/kg NaCl solution was added to a double ribbon mixer. There was no interaction between application time and wet mix time (P=0.6380). The results of Experiment 2 indicated that both wet mix time and application time affected the %CV (P=0.0009 and P=0.0296, respectively) when a 230 g/kg NaCl solution was added to a paddle mixer. There was no interaction between application time and wet mix time (P=0.2896). The results of Experiment 3 indicated that wet mix time (P=0.5256) did not impact %CV when a 230 g/kg NaCl solution was added to a twin shaft counterpoise mixer. The results of these experiments demonstrated that application time and wet mix time must be determined for each mixer type and size. The data from the experiments suggest that while extended liquid application times are beneficial, there must be a minimum wet mix time after all of the liquids have been added to the mixer.