Subtask 2.4 – Overcoming Barriers to the Implementation of Postcombustion Carbon Capture
The continued long-term use of North Dakota lignite is likely dependent on creating a business case for carbon capture, utilization, and storage (CCUS) that also addresses society’s desire to reduce carbon emissions. CCUS coupled with enhanced oil recovery (EOR) appears to be the most feasible option for utilities to sustain and grow the lignite industry. Establishing a market where lignite-powered utilities provide carbon dioxide (CO2) to oil producers depends upon a cost-effective method to capture CO2. CO2 capture technology challenges include minimization of the buildup of heat-stable salts, aerosol formation, degradation of solvents or solid sorbents, or subsequent solvent loss. Lignite, especially North Dakota lignite, presents its own set of challenges that include the combination of high sodium, sulfur, and ash contents; NOx reduction; and footprint limitations. This project was designed and carried out to support future commercial demonstration of advanced postcombustion carbon capture (PCCC) systems on lignite-fired units by addressing some of the technical barriers to future commercial demonstrations. Subtask 2.4 consisted of preliminary studies and testing in CO2 capture effectiveness that might be expected at the power plant, identifying potential operational issues with application of a solvent technology, obtaining a better understanding of various aspects of the economics of CO2 capture, and measuring and evaluating the impact of aerosols on amine solvent CO2 capture systems. The Energy & Environmental Research Center’s (EERC’s) pilot-scale solvent capture test system was used to evaluate CO2 capture from a flue gas produced by a lignite-fired cyclone boiler using monoethanolamine (MEA) and two Mitsubishi Heavy Industries’ (MHI’s) solvents: KS-1™ and an advanced solvent. Pilot-scale testing was performed at the EERC as well as at Minnkota Power Cooperative’s Milton R. Young Station Unit 2 (MRY2), where the EERC’s pilot-scale capture system was installed for slipstream testing. Test results indicate that MHI’s KS-1™ solvent captures more CO2 than MEA, while requiring roughly 30% less regeneration energy. The pilot-scale system was not optimized for any of the three solvents that were tested. An optimized system (as would be installed in a commercial-scale setting) would presumably produce even more positive results. Emission testing conducted during pilot-scale testing at both the EERC and at MRY2 showed low emission levels of the solvent itself, indicating that a proprietary emission reduction technology developed by MHI, called the AERU (amine emission reduction unit), could control amine emissions from lignite-fired flue gas. The formation of aerosols during the capture process is of interest, as are approaches for their reduction. Data from pilot-scale tests conducted at the EERC indicate that aerosol concentration and mass concentration decrease after the electrostatic precipitator. When the particles exit the system, the concentrations are below levels that have been identified as detrimental to the amine CO2 capture process. No significant difference in aerosol concentration or behavior was noted between Powder River Basin coal or lignite. Aerosol was reduced in the capture system for larger-size (900-nm to 2-µm) particulate. The very fine aerosol (50–200 nm) appears to be passing through both the emission control devices of MRY2 and the amine capture system. Options for better integration of a capture system into MRY2 were evaluated using Aspen Plus® models developed for the MRY2 combustion and steam cycles. Nine heat integration options were developed and evaluated, with the steam condensate heat recovery option identified as the most attractive and selected for more detailed, pre-FEED (front-end engineering and design) study. The option was less complex and capital-intensive than the alternate approaches. Three pipeline design options were evaluated for transporting CO2 to oil fields in western North Dakota for EOR: 1) a single pipeline sized to transport only CO2 produced by MRY2; 2) a single, larger-diameter pipeline sized to transport CO2 from MRY2 and other power plants; and 3) twin, smaller-diameter pipelines that could transport CO2 from both MRY2 and other power plants. The evaluation showed that, irrespective of approach, the pipeline system would cost hundreds of millions of dollars. The added expense associated with the second and third options must be weighed against the benefits accrued by making additional CO2 available for EOR. Study of fractional capture strategies suggests that the lowest-unit-cost designs do not include the use of an auxiliary boiler for steam and/or power production, while the highest-unit-cost designs do include this feature. In general, capture of at least 95% of the CO2 in the flue gas stream results in a lower unit cost for capture. The economics of CO2 capture, both in terms of the cost to build and operate a full-scale CO2 capture system and the impact on the state, were preliminarily determined. Using U.S. Department of Energy (DOE) capture cost methodology with bituminous coal baseline values, the estimated total project cost for applying capture technology would be $1.939 billion, with a cost to capture CO2 estimated to be $58.2/tonne. Using the same methodology but inputting values for capture costs developed during the pre-FEED study into the DOE bituminous baseline methodology spreadsheets produces an estimated total project cost of $1.576 billion in 2011 dollars at a cost to capture CO2 of $40.4/tonne. DOE also developed a baseline cost estimation methodology for capture at lignite-fired plants. The baseline methodology estimates a total project cost of $1.958 billion and a cost to capture of $40.1/tonne, both in 2007 dollars. When the pre-FEED-derived values are input into the spreadsheets, the estimated total project cost is $1.756 billion, with an estimated cost of CO2 capture of $32.8/tonne. These results indicate that additional study would be useful to better quantify the costs. The addition of full-scale carbon capture with EOR could add more than $1 billion/year in peak economic activity to the local economy. As many as 4000 jobs could be created each year, and North Dakota could see nearly $80 million in additional annual tax revenue from activities associated with and/or supporting CO2 capture and EOR. In conclusion, this project showed that greater than 90% CO2 capture at a lignite-fired power plant was technically feasible, that the majority of solvent and aerosol emissions could be controlled, that options exist for heat integration of a capture system into MRY2, and that a full-scale project could be a boon to the North Dakota State economy. This project was cofunded through the EERC–DOE Joint Program on Research and Development for Fossil Energy-Related Resources Cooperative Agreement No. DE-FE0024233. Nonfederal funding was provided by the North Dakota Industrial Commission, ALLETE, and Minnkota Power Cooperative.
- Research Organization:
- University of North Dakota EERC
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FE0024233
- OSTI ID:
- 1580659
- Report Number(s):
- 2019-EERC-12-14; 2019-EERC-12-14
- Country of Publication:
- United States
- Language:
- English
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