Demonstration of the Swing Adsorption Reactor Cluster (SARC) for simple and cost effective post combustion CO2 capture

The project main objective is to demonstrate the technical and economic feasibility of the Swing Adsorption Reactor Cluster (SARC) concept through dedicated experimental and modelling studies. The SARC concept consists of a cluster of bubbling/turbulent multistage fluidized bed reactors, which dynamically cycle a solid sorbent between carbonation and regeneration. A synergistic combination of vacuum and temperature swings is employed to ensure high process efficiency. The primary project outcomes will be long-term demonstration of a lab scale Swing Adsorption Reactor and the full scale thermodynamic and economic evaluation of the SARC concept applied to Waste-to-Energy (WTE) and cement plants. Two WTE plant operators and a cement producer are taking part in the project in order to show the industrial relevance of the SARC concept and identify a strong business case for further scale up of the technology. The SARC project carried out an extensive study that combined experimental and simulation investigations. The experimental activities covered i) sorbent screening on two families, Polyethyleneimine (PEI) and alkali-metal sorbents completed in TGA, breakthrough and a bench-scale reactor custom designed to simulate the SARC conditions. The PEI sorbents have shown to perform the best a high cycling stability at reasonable working adsorption capacity, thus it was recommended for use in the demonstration reactor. 20 kg from a PEI sorbent was then supplied by KRICT for further testing in the larger reactor. ii) A pre-pilot 2 m height demonstration reactor, with inbuilt heat transfer surfaces, was constructed, commissioned and thoroughly tested under SARC conditions evaluating the heat transfer characteristics, the rate limiting in the sorbent performance, the cyclic SARC performance and the multistage effect. The simulation activities covered: i) Reactor and power plant simulations of SARC integrated in coal, cement and WTE plants were completed including sensitivity studies to the process operation parameters, thus identifying the conditions that achieve the lowest energy penalties on each application. ii) First economic assessment study that was completed for integration of SARC into a cement plant has shown that SARC achieves CO2 avoidance costs of eur 52/ton in the base case, which is higher than oxyfuel combustion (eur 43/ton), similar to calcium looping and lower than four other technology options. iii) A subsequent study improved the heat integration within the SARC plant to raise vacuum pressure steam for driving additional CO2 release in the desorption step. This modification allowed SARC to compete with the oxyfuel route, achieving eur 38/ton, making it clearly the most attractive option given the simplicity of retrofitting in existing plants. Key results: -- PEI sorbents performed the best exhibiting fast kinetics and reasonably high working adsorption capacity at feasible vacuum levels (0.1 bar) and a 20 °C temperature swing. -- The SARC concept was demonstrated at TRL 4 using a custom-designed reactor at a capacity of ~24 kg-CO2/day. -- Reactor and power plant simulations have shown that SARC operating with sorbents having medium and high regeneration enthalpies (100-150 kJ/mole) can improve the capture energy efficiency on coal power plants by ~2%-points plant efficiency achieving an energy penalty as low as 8%-points. -- The calculations on a cement plant have shown that the energy penalty can achieve a SPECCA as low as 0.88 MJLHV/kgCO2 if renewable electricity is used for powering the heat and vacuum pumps. -- An economic assessment study with improved heat integration has revealed that a CO2 avoidance cost of eur 38/ton-CO2 could be achieved for SARC integrated in a cement plant (instead of eur 52 achieved in the earlier study), while further cost reduction could be achieved in the use of low-cost renewable electricity such as the case of Norway. Eight journal papers have been published and several popular science articles published on multiple platforms in Gemini (https://geminiresearchnews.com/2018/05/capturing-co2-using-heat-pumps/), PhysOrg (https://phys.org/news/2018-05-capturing-co2.html), NorskVVS NEMITEK (https://nemitek.no/vil-fange-co%e2%82%82-med-varmepumper/) and Teknisk Ukebladet (https://www.tu.no/artikler/denne-losningen-gjor-industriell-co-fangst-12-5-prosent-billigere/508168). The results were also disseminated in relevant conferences such as GHGT 15 & 16, PCCC5, ISCRE and Fluidization XVI.

The project has brought the SARC technology to TRL 4 and completed techno-economic assessments have shown that it can achieve CO2 avoidance cost as low as 38 Eur/ton-CO2 for cement beating all bencharmking technologies including oxy-fuel. The easy retrofitting of SARC is another key advantage that will facilitate its fast upscaling and application to different CO2 industrial sources.

The proposed project will demonstrate the technical and economic feasibility of the Swing Adsorption Reactor Cluster (SARC) concept through dedicated experimental and modelling studies. The SARC concept aims to minimize both the energy penalty and process complexity related to post-combustion CO2 capture using low-temperature solid sorbents and brings special advantages to retrofits and industrial applications. Individual standalone reactors in the SARC concept will operate under bubbling/turbulent fluidization using the best performing low-temperature sorbent supplied by the Korean and American partners in this project. Inlet and outlet valves will periodically switch each reactor between carbonation and regeneration, separated by a short temperature/vacuum swing step. Combination of temperature and vacuum swings will minimize the total energy penalty. Dedicated optimization studies will determine the shares of each swing and the interaction between them. In addition to the minimized energy penalty, the SARC concept promises greater process simplicity in terms of reactor design and connection to the CO2 source, leading to faster scale-up and broader deployment possibilities. These advantages stem from the elimination of the solids handling challenges inherent to the conventional solids looping process and the fact that SARC does not require steam for regeneration of the sorbent. The primary project outcomes will be long-term demonstration of a lab scale Swing Adsorption Reactor and the full scale thermodynamic and economic evaluation of the SARC concept applied to Waste-to-Energy (WTE) and cement plants. Two WTE plant operators and a cement producer are taking part in the project in order to show the industrial relevance of the SARC concept and identify a strong business case for further scale up of the technology.