Advanced configurations for post-combustion CO2 capture processes using an aqueous ammonia solution as absorbent

Abstract

In this work, we have developed advanced process configurations for solvent-based CO2 capture processes that use aqueous ammonia as absorbent. In total, ten different advanced configuration concepts have been optimized and analysed, aiming at: (i) achieving in spec NH3 emissions in a controlled way; (ii) minimizing capital costs by avoiding redundant process components; (iii) minimizing the energy demand of the capture process by minimizing the requirements of high temperature steam and by maximizing the possibilities for the use of excess heat from the CO2 point source. As a result, we propose a new benchmark configuration for NH3-based capture processes that, with proper tuning of the process operating conditions, allows to minimize the specific energy consumption while enhancing the flexibility of the capture process with respect to the type and to the features of the electricity and steam available at the CO2 point source, at the minimum consumption of chemicals and process water. This new benchmark configuration for NH3-based capture processes is built upon the Chilled Ammonia Process, avoids the formation of solids and includes: (i) a multi-pressure desorber with recycled vapour compression that is able to decrease the high temperature steam requirements for solvent regeneration, i.e. at ca. 140–160 °C, to values as low as 1.1 MJthkgCO2captured−1, (ii) a vacuum integrated stripper for the recuperation of the solvent that is able to use low temperature steam instead, i.e. below 100 °C, and (iii) a flue gas water-wash column that is able to reduce the NH3 concentration in the CO2-depleted flue gas to values below 10 ppmv without the need of an acid-wash column before the stack.