Temperature swing adsorption compression and membrane separations

Abstract

CHEMICAL AND BIOMOLECULAR ENGINEERING TEMPERATURE SWING ADSORPTION COMPRESSION AND MEMBRANE SEPARATIONS JOSEPH R. MOATE Dissertation under the direction of Professor M. Douglas LeVan The feasibility of the capture and pressurization of CO2 from an enclosed environment using an integrated membrane dryer and two-stage temperature swing adsorption compression system is investigated in this work by fundamental research on the operation of temperature swing adsorption (TSA) beds, dispersive flow through packed beds, and dehydration of a process stream using a shell and tube membrane module. The first section of this dissertation focuses on sizing a two-stage TSA compressor that preferentially adsorbs CO2 and analysis of its subsequent performance with the aid of mathematical models. Solutions to the material and energy balances reveal a relationship between the volume of the two stages and the pressures reached within the stages. Also, the method in which the beds are heated, whether uniform or not, is investigated and is found to have a significant impact on the desorption of CO2. Next, a mathematical model that describes nonplug flow through a packed bed of adsorbent in which a constant pattern develops is studied for a slightly favorable isotherm. A generalized perturbation solution of the model that extends to the first and second order is developed that considers both axial and transverse gradients of concentration in the fluid phase. First order corrections to the plug flow model and fluid-phase concentration profiles for two example velocity profiles are formulated that illustrate the influence of the shape of the velocity profile on breakthrough behavior. In the final section, the effects of scale on the dehydration of a process stream is considered for two shell and tube membrane modules, one with a vacuum on the shell side and the other with a purge gas to facilitate water transport. It was determined that special considerations must be made to prevent flow maldistribution within the shell side of the membrane modules as this degrades dehydration performance. Also, the use of a vacuum on the shell side successfully dehydrates a process stream, but water transport through the membrane is overestimated using previously developed relationships for the diffusion coefficient. Approved: Date: