CO2 capture processes using rotary wheel configurations

A method for enhanced control, separation, and/or purification of CO.sub.2 gas from one or more sources having a mixture of gases, the method comprising:

• providing a solid monolithic sorbent material having a thickness and a selectivity for CO.sub.2 sorption in a continuous or semi-continuous sorption-desorption process comprising a CO.sub.2 sorption step, a CO.sub.2 desorption step, and an at most partially cooling step, but not comprising a drying step;
• providing one or more mixed gas sources containing CO.sub.2 gas at a feed temperature, such that the mixed gas source(s) collectively exhibit not more than 70% water vapor saturation;
• adding liquid phase water droplets to the mixed gas source(s) to form a dual phase sorption feedstream containing CO.sub.2 and H.sub.2O at approximately the feed temperature, the amount of liquid phase water being sufficient to cause the dual phase sorption feedstream to have at least 99% water vapor saturation at a desorption temperature, which is higher than the feed temperature, and to have at least gas phase CO.sub.2 and H.sub.2O and liquid phase H.sub.2O components at the desorption temperature;
• in the CO.sub.2 sorption step, exposing the dual phase sorption feedstream at approximately the feed temperature to the solid monolithic sorbent, which is at the desorption temperature, across the thickness of the sorbent under conditions sufficient for the solid monolithic sorbent to selectively sorb the desired CO.sub.2 gas, thus forming a selectively CO.sub.2-sorbed solid monolithic sorbent and a selectively CO.sub.2-depleted product stream;
• in the CO.sub.2 desorption step, exposing the selectively CO.sub.2-sorbed solid monolithic sorbent to a stripping stream, which contains moisture and which is at a stripping temperature that is at least about 20.degree. C. higher than the inlet temperature, across the thickness of the sorbent, thus forming a CO.sub.2-desorbed monolithic sorbent, and a stripped product stream containing desorbed CO.sub.2;
• and in the at most partially cooling step, cooling only a portion of the thickness of the CO.sub.2-desorbed monolithic sorbent by exposing the sorbent to a co-current cooling stream for a time and under conditions sufficient to cool only the portion of the thickness of the solid monolithic sorbent to approximately the feed temperature, wherein the portion of the thickness of the solid monolithic sorbent is less than one half the thickness of the solid monolithic sorbent, wherein the CO.sub.2 sorption step is exothermic and selectively sorptive for CO.sub.2, such that the exposing of the dual phase sorption feedstream to the solid monolithic sorbent results in a thermal wave, having a leading edge, passing across the thickness of the sorbent and simultaneously in a CO.sub.2 sorption wave, having a leading edge, passing across the thickness of the sorbent;
• wherein the at most partial cooling step causes the leading edge of the thermal wave to start at a position within the thickness of the sorbent corresponding to the portion of the thickness of the sorbent that was cooled;
• wherein the thermal wave passes across the thickness of the sorbent only as fast as, or slower than, the CO.sub.2 sorption wave, and yet wherein, due to the partial cooling step, the leading edge of the thermal wave still passes across the thickness of the sorbent in a position downstream from the leading edge of the CO.sub.2 sorption wave;
• and wherein the liquid phase water in the dual phase sorption feed sorbs heat resulting from the desorption temperature being greater than the feed temperature by changing to gas phase water vapor to simultaneously partially cool the sorbent during the sorption step, thus allowing the separate cooling step to be partially eliminated in the continuous or semi-continuous sorption-desorption process.