Application of the Carbon Dioxide-Barium Hydroxide Hydrate Gas-Solid Reaction for the Treatment of Dilute Carbon Dioxide-Bearing Gas Streams

摘要

The removal of trace components from gas streams via irreversible gas-solid reactions in an area of interest to the chemical engineering profession. This research effort addresses the use of fixed beds of Ba(OH) sub 2 hydrate flakes for the removal of an acid gas, CO sub 2 , from air that contains approx. 330 ppM/sub v/ CO sub 2 . Areas of investigation encompassed: (1) an extensive literature review of Ba(OH) sub 2 hydrate chemistry, (2) microscale studies on 0.150-g samples to develop a better understanding of the reaction, (3) process studies at the macroscale level with 10.2-cm-ID fixed-bed reactors, and (4) the development of a model for predicting fixed-bed performance. Experimental studies indicated fixed beds of commercial Ba(OH) sub 2 .8H sub 2 O flakes at ambient temperatures to be capable of high CO sub 2 -removal efficiencies (effluent concentrations <100 ppB), high reactant utilization (>99%), and an acceptable pressure drop (1.8 kPa/m at a superficial gas velocity of 13 cm/s). Ba(OH) sub 2 .8H sub 2 O was determined to be more reactive toward CO sub 2 than either Ba(OH) sub 2 .3H sub 2 O or Ba(OH) sub 2 .1H sub 2 O. A key variable in the development of this fixed-bed process was relative humidity. Operation at conditions with effluent relative humidities >60% resulted in significant recrystallization and restructuring of the flake and subsequent pressure-drop problems. (ERA citation 08:055536)