One-Dimensional Formulation for Heat and Mass Transfer in Solid Desiccant Dehydration of Natural Gas

Abstract

An analysis of heat and mass transfer in the dehydration of natural gas using solid desiccants has been carried out, leading to a mathematical model for the simulation of the dehumidification process of a wet gas stream flowing through a porous bed containing desiccant particles. The process is divided in two periods: one for adsorption, in which the gas stream is actually dehydrated, and another one for the regeneration of the desiccant material, both of which are cyclically applied. The mathematical model considers spatial dependence in the flow direction, such that heat and mass transfer resistances within particles are treated in a lumped capacitance fashion. The resulting formulation constitutes a system of four coupled equations for describing temperature and humidity fields within solid particles and in the gas stream. These equations are normalized in terms of physically meaningful dimensionless groups, and numerically solved for producing simulation results for different configurations. The results suggest that the duration of regeneration periods can be shorter than those for adsorption, and that this dependence is clearly influenced by the regeneration temperature. In addition, it is seen that larger operation pressures can lead to larger water concentration in the adsorbed phase, and hence higher dehumidification levels.