Development of procedure for thermohydraulic calculation of heat accumulators of units for complete air purification

Abstract

A procedure for thermohydraulic calculation of heat accumulators used in the loop for regeneration of adsorbers of modern complete-purification units for medium and large air-fractionating plants is described.Recommendations for appropriate designing of heat accumulators can be formulated making use of the proposed procedure.Heat accumulators began to be used relatively recently in loops for regeneration of adsorbers in modern completepurification units for large and medium air-fractionating plants (AFP). A description of the function and operation cyclograms of heat accumulators as well as an example of using such equipment in the complete-purification unit of a currently operating AFP are given in [1,2].Heat accumulator is a typical representative of regenerative type of equipment. For detailed calculation of the operation of a regenerative type of equipment, account must be taken of the unsteady pattern of heat exchange in such equipment.The study of the accumulator operation dynamics, as applied to complete-purification units of AFP, is essential for the following basic reasons: 1) for determining the pattern of packing heating across the equipment height as a function of process time (in the case of heat accumulation);2) for determining the temperature of the regenerating gas at the equipment outlet as a function of process time (in the case heat extraction); and3) for determining the magnitude of hydraulic resistance of the packing bed in the heat extraction process. No thermohydraulic calculation procedure has been developed so far for analysis of the referred parameters for designing heat accumulators for complete-air-purification units.Development of such a procedure will make it possible to conduct computational studies for selecting the optimum design and process parameters of such heat accumulators, followed by their testing and refinement based on start-adjustment operation results.Let us examine the heat exchange between the regenerating gas and the packing within the chosen time length and the volume element (across the packing bed height). Assuming that the thermophysical properties (density, thermal conductivity, heat capacity, viscosity, etc.) of the gas passing through the packing as well as of the packing are constant within this