The effects of different mixing and process parameters on the formation of crystals obtained from semi-batch precipitation are reported. The influence of feed time, feed concentration, feed tube diameter and impeller type on particle morphology of calcium oxalate and calcium carbonate respectively are discussed. In addition, a hybrid mixing-CFD model, the Segregated Feed Model (SFM), is used to predict the influence of process conditions on product particle size via the population balance. Experimental results for the particle size using 1, 5 and 251 reactors show reasonable agreement with model predictions.