Is adsorption a competitive post-combustion CO2 capture technology?
Adsorption is an environmentally benign separation technology with no associated toxic emissions that presents potential to reduce the energy penalty of CO2 capture processes. Several adsorption based post-combustion CO2 capture processes have reached the pilot scale demonstration stage. These adsorption processes differ in the adsorbent used, mainly zeolites, carbon materials, solid amine sorbents, and supported alkali carbonates, but also in the process configuration: the method of regeneration (temperature, vacuum, concentration swing or a mixture of those) and the type of adsorbers used (fixed beds, rotary beds, moving beds, and fluidized beds). However, their lower stage of development compared to the benchmark technology, amine absorption, has prevented up to date their commercial development. In this work, adsorption-based post-combustion CO2 capture processes, based on sustainable carbon adsorbents in a multibed configuration, have been designed and assessed through process simulation in order to compare them to the benchmark technology using a common reference, i.e., an advanced supercritical coal power plant of 800 MWe, and similar specifications to enable a fair comparison. The cyclic adsorption processes have been modelled and simulated up to cyclic steady state (CSS) using a dynamic non-equilibrium non-isothermal mathematical model that takes into consideration competitive adsorption between the main flue gas components: N2, CO2 and H2O. Such model had been previously validated against experimental results. The CSS results entailed assessing the capture rate and the CO2 purity of the product for each particular adsorbent and process configuration combination, allowing identifying those that can meet the minimum capture rate (85%) and CO2 purity specifications (95%). Such processes were then compared to the benchmark technology in terms of overall energy consumption. Among the process configurations evaluated up to date, the configuration that employs a vacuum, temperature and concentration swing regeneration strategy, together with low temperature heat, is the most promising. This process, which makes use of a sustainable biomass based carbon, presents a lower specific energy penalty per avoided CO2 than the benchmark technology. Furthermore, greater energy savings could be expected from the development of adsorbents with superior adsorption performance in terms of working capacity and adsorption kinetics. ; Marta G. Plaza acknowledges the award of a Ramon y Cajal contract (RyC-2015-17516) from the Spanish Government ; Peer reviewed