Utilization of dust and ammonia from exhaust gases: new solutions for dryers with different types of fluidized bed

BACKGROUND: The article is devoted to the development of new utilization methods of exhaust gases by cleaning them from fine particles, dust and harmful gas components. The basic design solutions, which allow to increase the degree of exhaust gases cleaning, were presented. The effectiveness of design solutions was supported by the results of experimental studies. Analysis of the research results allowed developing of new designs of equipment for dehydration in fluidized bed. The article also presents the calculation algorithm of eco-friendly dryers with fluidized bed. METHODS: Physical modeling was based on methods of similarity theory. In studies in dryers experimental models the installation scale was changed (compared with industrial conditions). Geometric similarity was maintained by equity of constants and invariants of geometric similarity. Always similarity of respective particles movement and their trajectories in industrial design and in experimental models was also maintained. The creation of graphical dependences was carried out by differential methods of mathematical analysis and integral calculus. The reliability of obtained experiment results was caused by the application of time-tested in practice methods. RESULTS AND DISCUSSION: Control of product fractional composition allowed to make a selection of required fractions (including the fine granules) in a certain place of device. This allowed to increase the degree of purification of exhaust gas even before it output from the dryer working space. The process of separating the granules into fractions and the selection of fine fraction can be performed due to structural changes in dryer units and selection of optimal hydrodynamic conditions of fluidizing agent motion. Installation of special units in the dryers allowed to extract other contaminants from the exhaust gases. CONCLUSIONS: Proposed constructive solutions for fluidized bed dryers allowed to: - provided of granules classification to the desired number of fractions with a simultaneous release and discharged of fine fraction from the working volume of dryer without the exhaust gases; - increased the degree of monodispersity of commodity granules on 25–35%; - reduced the amount of dust in the exhaust gases on 35–65%; - reduced the ammonia content in the exhaust gas on 90–95%.