Continuous autocirculation, multiple zone mass transfer apparatus and

Abstract

An apparatus and method of contacting a liquid with different gases sequentially in separate mass transfer zones within a single vessel, the mass transfer zones operatively connected in liquid communication with each other, including intimately contacting the liquid with a first process gas in cocurrent flow in a first mass transfer zone to effect mass transfer between the first liquid and the process gas, and introducing the liquid into a second mass transfer zone with a second gas, different from the first gas, in cocurrent flow with the second liquid, thereby effecting mass transfer between the second liquid and the second gas. The rate of flow of the liquid from said first mass transfer zone to second mass transfer zone and recirculation to the first mass transfer zone is motivated by the difference in density of the contents of the liquid phase portion of each mass transfer zone and a following liquid downcomer or flow channel connecting it to the next sequential mass transfer zone, such that after passing through the last mass transfer zone, the liquid recirculates to the first mass transfer zone. The apparatus and method are ideally suited to carrying out the process of hydrogen sulfide removal from gases by means of an air-regenerated liquid redox catalyst, such as chelated iron.