The effect of hydrocarbon condensate and anti-foaming agents on the performance of CO_2 absorption with activated MDEA

摘要

The use of aqueous solutions of methyldiethanolamine (MDEA) activated with primary or secondary amines for removal of CO_2 is finding increasing use in gas processing plants. In industrial use, the amine solution is frequently exposed to hydrocarbon condensate and additives such as anti-foaming agents. This paper investigates the effects of the presence of these contaminants in activated MDEA solutions with respect to CCK absorption. The robustness to contamination of activated MDEA-solutions has been studied using the process conditions at the Sleipner Vest CO_2 removal plant in the North Sea as a base case. Solutions of 39% MDEA containing 6% butylethanolamine (BEA) or 6% aminoethylethanolamine (AEEA), in addition to amine samples taken from the Sleipner plant have been investigated with respect to CO_2 absorption rate and heat of reaction. These performance data have been achieved with a specially designed solvent characterisation reactor operated at a CO_2 pressure of 1.5 bar (22 psia) and temperatures between 20 and 50℃ (68 and 122℉). The reactor is designed to mimic typical operating conditions in the absorption tower and to allow the contaminant to be introduced as a homogeneously dispersed liquid. Using AEEA as an activator, the absorption rate decreases approximately linearly with increasing CO_2-loading of the amine, while the BEA-activated solution is less sensitive to the CO_2-loading. The heat of reaction for activated amine and CO_2 is somewhat higher with AEEA than with BEA, and drops slightly with increasing CO_2 -loading. Typically, the measured CO_2 absorption rate is reduced by 40-55% when hydrocarbon condensate or anti-foaming agent are added to the MDEA/BEA mixture, whereas less than 20 % reduction in absorption rate is measured for the MDEA/AEEA solvent.