Cryogenic Carbon Capture Development Final/Technical Report (2019)

This project extends and leverages the work completed under funding from ARPA-E and other sources by exploring aspects of the Cryogenic Carbon Capture™ (CCC) process and issues discovered during those projects, but that were not within the scope or budget of previous projects or that became apparent during field tests. Our successful completion of the tasks outlined in this project has increased the reliability, efficiency, and scalability of the CCC process and we are better prepared for pilot-scale testing. The first phase of this project improved key areas of the process through iterative design and experiment, culminating with recommendations for improvements to the existing skid-scale system developed under non-federal funding. The second phase of this project implemented the improved unit operations into the Cryogenic Carbon Capture External Cooling Loop (CCC ECL™) skid and field tests the improved system at a coal-fired power plant. The specific areas of work in this project are: Budget Period 1: Sustainable Energy Solutions, LLC (SES) has successfully demonstrated a dryer that removes bulk water using a low-temperature brine to remove about 99% of the water followed by a mol sieve 3A desiccant dryer to remove the remaining 1% water. SES has tested several commercial heat exchangers that purport to be able to handle fouling issues similar to those experienced in the contact liquid chiller. Replicated tests using the CCC ECL™ skid and dimpled brazed plate heat exchangers demonstrate that quick throttling of refrigerant combined with a burst of clean gas mitigate the fouling caused by CO2 solubility in contact liquid with only minor increases in parasitic load. SES models indicate that parasitic load would increase by approximately 0.0125 GJ/tonne. The screw press technology met or exceeded the 70% solids loading benchmark during several test runs exceeding 24 hours as well as the initial stages of a 50-hour test run while capturing 0.5 tonne/day CO2 on the CCC ECL™ skid. The average solids loading during the entire 50-hour run was 67%. The energy demand for this system is less than 0.1 GJe/tonne of CO2 processed, all of which involves turning the auger. SES designed and built a hybrid spray tower that combines the fast cooling of SES’ patented bubbling desublimating heat exchanger and the efficient heat exchange of a spray tower. The hybrid spray tower/bubbler was tested over many hundreds of hours and a 50-hour continuous test run was completed capturing over 0.5 tonne CO2/day at >90% capture. The AERSCREEN simulator developed by the EPA modeled the dispersion of oxygen-depleted flue gas from the CCC process at a commercial plant. SES performed these simulations with review by Sargent & Lundy. The results indicate that this plan effectively mitigates the flue gas hazards. SES programmed an upgrade to its solid/vapor/liquid equilibrium (SVLE) algorithm, moving from single-component to multi-component modeling. This enables simultaneous modeling of multiple pollutants (i.e., CO2, SOx, NOx, Hg, HCl). The results compare well with experimental data and predict reasonable pollutant concentrations in the outlet streams from the CCC ECL™ process. The Budget Period 1 techno-economic analysis has been completed. It confirms the potential large reduction in energy and cost of the CCC process compared with leading alternatives and that the estimates and estimation techniques are reliable. Budget Period 2: The plans for modifying the CCC ECL™ skid were finalized and put into place. Shakedown testing of the updated CCC ECL™ skid occurred at SES using closed-loop mode (i.e., using a synthetic flue gas consisting of only N2 and CO2) and at the Hunter Power Plant using flue gas from the coal-fired boiler. Shakedown testing took longer than expected due to delays in receiving equipment and unexpected equipment performance in the field. Shakedown testing was completed in May 2019. Longer testing of the CCC ECL™ skid occurred at the Hunter Power Plant. Multiple tests exceeding 35 hours were completed, with a total of over 600 hours of CO2 capture completed using flue gas at the Hunter Power Plant with an average CO2 capture rate of over 91% during those hours. Extensive notes and documentation were acquired informing improved methods for controls, startup, operation, and shut down. SES defined figures of merit for unit operation performance and overall CCC ECL™ process performance. All figures of merit were achieved or surpassed, except for 500 continuous hours of demonstration at the Hunter Power Plant. Tri-State (a third party) completed an Environmental Health and Safety Risk assessment.