Substantiation of a rational method for drying granules in a fluidized bed and the hydrodynamic regime of their interaction with a fluidizing agent

Abstract

Gluten is produced from wheat grains and is used in the food industry as an improver in flour baking properties. On the basis of a comparative analysis of the methods of dehydration of frozen granules of wheat gluten with a surface dry crust, a rational method of drying them in a fluidized bed has been selected. In the process of calculating units with a fluidized bed, its hydrodynamic parameters have been determined: loss of the pressure of the fluidizing agent; the speed at the transition of the bed from the state of rest to the pseudo-boiling mode; layer porosity; the rate of entrainment of particles in unrestricted conditions roughly corresponding to the rate of soaring, at which a single particle is in equilibrium in the gas flow. During the dewatering operation, the rate of entrainment of the granules varies; therefore, it is advisable to use the passing fluidization mode depending on the decrease in their moisture content. In the variant of the active hydrodynamic regime in the drying unit, the dehydration procedure is intensified without a noticeable decrease in the economic efficiency of its functioning and high quality indicators of the finished product with the given final moisture are provided, which is due to the specific conditions of contact of the granules with the coolant. For granules with a moisture content of 0.19 kg/kg, the values of hydrodynamic characteristics have been determined: the area of critical pseudo-boiling rates is 4.1-5.5 m/s; the carryover rate of the fines is 12.5-14.5 m/s. As a result of the study, the choice has been substantiated in favor of drying the studied granules in a fluidized bed due to the prevalence of its advantages over the dehydration of the object in drum dryers.