Calculations of the pulse combustion drying system

The paper describes modelling of spray drying system where valved and valve less pulse combustors were applied as a source of drying agent. Experimenta l analysis of pulse combustors operation was carried out in order to optimi ze their performance to achieve low emission of toxic substances, stable op eration and high and smooth pressure oscillations. Optimized valved and val veless units were applied in the drying system. Extensive drying and evaporation tests were carried out to establish basic data required for modelling of the system. Laser techniques were applied to determine flow field in the drying chamber (LDA) as well as to analyse the structure of disperse phase (PDA). A modified mathematical model of heat, mass and momentum transfer in spray drying, developed earlier, was used to describe the pulse combustion drying system. The model enables to obtain temperatures of continuous and dispers e phases, percent of evaporation and positions of particular fractions in t he dryer. Air velocity profiles in the axial and radial directions in the d rying chamber determined experimentally were substituted to the main progra mme calculating the spray drying process. A comparison of theoretical and experimental results shows good agreement a lso for complex hydrodynamics of pulsating flow in the drying chamber. Experimental investigations and mathematical modelling proved that the puls e combustion spray drying system could be effectively applied in dewatering of solutions with low content of solids, which could be important for wast e disposal. (C) 2001 Elsevier Science Ltd. All rights reserved.