A mathematical model of the self-heating of spray-dried food powders containing fat, protein, sugar and moisture

Spray drying is a primary process for particulate forming in the food industry. Powders that contain fat, protein and sugar are potentially explosive. The self-heating of milk powders (as typical examples) can become a source for a fire or even dust explosion in dairy powder plants. In order to predict the heating behaviour in milk powder deposits, a mathematical model describing self-heating in low moisture solids has been developed and a numerical simulation program has been written. The program solves the mass and energy balances in the model simultaneously for the dairy powder samples. The model can be shown to be capable of adequately simulating the change in temperature as influenced by evaporation in the samples. Results of the simulation have been compared with measured data. There is good agreement between the predicted and experimental results. It is envisaged that the model will also be useful for other exothermically reactive solids. (C) 1999 Elsevier Science Ltd. All rights reserved.