Modern ganulation technique

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The process of fluidized bed spray granulation is widely used to transform solutions, suspensions or melts into free flowing, dustless disperse granules. Beside the intensive solid mixing the combination of different processes such as particle formation, drying and homogenization are the main advantages of the fluidized bed technology. Usually, air is used as fluidization gas and drying agent. For certain applications the fluidization with air is not feasible. In such cases the solvent vapour can be used as fluidization gas. In the framework of this study we will focus on an application that provides the fluidization with superheated steam. The superheated steam technology offers a number of advantages, e.g.: - Energy saving potential up to 50% because of steam gas circulation, - Emission disposal by controlled burning or by condensation with steam, - Increase of plant safety by treatment of explosive products, - Sterilization of harmful biological products (waste water, sewage sludge) The objective of this study is to analyse the technical feasibility of this process. Therefore experimental and theoretical investigations have been carried out. A pilot plant has been constructed and experimental measurements have been done. Besides a theoretical model for the description of heat and mass transfer has been developed. Energy balance of liquid Degree of wetting Energy balance of particles Energy balance of the wall Energy balance of gas phase Temperature of gas phase Mass balance of gas phase Assumption for evaporation flow rate quasi-stationary Pilot plant for granulation: Investigations with air and superheated steam as fluidization gas Measurements of 2-dimensional temperature distribution in water-sprayed steam fluidized beds Experimental set-up: - 250 mm diameter of fluidization chamber - fluidization by steam or air - single component nozzle (hollow cone) - maximal steam flow rate: 550 kg/h - 60 kW heater - batch and continuous processes possible Measurements of 2-dimensional temperature distribution in water-sprayed steam fluidized beds Objective: - liquid deposition in the fluidized bed - temperature gradients - thermal influence of the nozzle Glass beads (d 32 = 2.3 mm) -Al 2 O 3 - particles (d 32 = 1.8 mm) Process parameters: inlet mass flow steam 300 kg/h liquid mass flow 20 kg/h steam inlet temperature 220 °C fluidized bed height 300 mm bed mass (glas beads) 14 kg bed mass (  -Al2O3) 5 kg Measurements and simulation of transient outlet temperature step-response functions for water-sprayed steam fluidized beds Glass beads (d 32 = 2.3 mm) -Al 2 O 3 - particles (d 32 = 1.8 mm) mass flow liquid: 10 kg/h, inlet temperature: 220 °C, mass flow steam: 300 kg/h Batch granulation experiments mass flow liquid: 25 kg/h, inlet temperature: 220 °C, mass flow steam: 300 kg/h, concentration of solid: 31mass-% Experiment Simulation Nuclei Solution of sodium benzoate Granules (coated) One-dimensional population balance for a batch granulation process Kinetics for surface proportional particle growth CONTACT ACKNOWLEDGEMENT The research project "fluidized bed granulation in superheated steam atmosphere" is supported and promoted by the "AiF-Arbeitsgemeinschaft industrieller Forschungsvereinigungen FLT” - project number 14152 B/1. Email: robert.hampel@vst.uni-magdeburg.de stefan.heinrich@vst.uni-magdeburg.de address: Universitätsplatz 2 D-39116 Magdeburg Germany phone: +49-391-6712778 Modeling and experimental analysis of superheated steam granulation R. Hampel a , S. Heinrich a , M. Peglow b , L. Mörl a a Institute of Process Equipment and Environmental Technology b Institute of Process Engineering Otto-von-Guericke University Magdeburg, Germany