Modelling the influence of physicochemical material feed properties on ammonium nitrate product quality

Abstract

In this study the effect of the physicochemical material feed properties of ammonium nitrate on the product granule quality in a fluidised bed granulator was investigated. The effect of atomising air pressure, binder spray concentration, binder spray temperature, binder spray rate and feed particle size on the final particles’ abrasion resistance, size, shape, porosity and flowability was investigated on a production plant using a five factor, five level central composite design. The data obtained from the experimental work was then subjected to regression analysis, where multiple linear regression models with and without two-way interaction effects as well as a second order regression model was obtained for each of the quality parameters. The models obtained were evaluated by using the coefficient of determination (R2), the mean square error (MSr) and the F-test. The models deemed adequate were then validated using a different data set. The abrasion resistance and particle shape was adequately described by multiple linear regression equations with two-way interactions. The identified physicochemical material feed properties of ammonium nitrate therefore successfully describes both the particles’ resistance to abrasion as well as the particle shape. The particle size was positively evaluated during the model development phase but proved to be inadequate during validation. The physicochemical material feed properties of ammonium nitrate and the experimental design alone were unable to describe the particle size adequately. All the regression models obtained for both the particle porosity and flowability were deemed inadequate in describing these two quality parameters during both the model development and validation phases. Both quality parameters are associated with high measurement errors which could explain the complete inefficiency of the models obtained. A further in-depth investigation of the particle size, particle porosity and flowability is needed to quantify the effect of the physicochemical material feed properties of ammonium nitrate on these quality parameters