Scale-Up of Coal-Based Supercritical CO<sub>2</sub> cycle technology

Abstract

The Allam Cycle is a transformational technology that enables a step change in the performance, efficiency, and cost of electricity for electrical generating units by using supercritical CO2 (sCO2) as the working fluid in the turbine for power generation. The objectives of this Phase I effort were to select a host site for a large pilot system through a process of down selection, develop a conceptual design, and conduct a pre-front-end engineering design (pre-FEED) study for a sCO2 cycle pilot plant that uses domestic coal reserves as the primary feedstock, thereby furthering technology development of the coal-based Allam Cycle. The project was divided into four main tasks: 1) Project Management and Planning; 2) Conceptual Pilot Plant Definition and Host Site Selection; 3) Preliminary Design, Cost, and Schedule Development; and 4) Commitments and Environmental Information Volume (EIV). All project management activities occurred in Task 1. Host site selection was conducted in Task 2, while conceptual design and pre-FEED activities took place under Task 3. Task 4 enhanced the project by securing commitments for the next phase of the program and completing an initial EIV. The Great Plains Synfuels Plant (GPSP) has been selected as the host site for the large-scale pilot, and its owner, Dakota Gasification Company (DGC), is a committed partner. GPSP was compared to two other host site candidates during Phase I: the existing natural gas Allam Cycle facility in La Porte, Texas, and the Energy & Environmental Research Center’s (EERC) high-bay demonstration facility in Grand Forks, North Dakota. Costs for hosting the pilot plant were estimated for each facility, and those costs are shown in Table ES-1. Based on these estimates, the DGC site was clearly shown to be the lowest cost option and was selected as the host site for the project. Table ES-1. High-Level Cost Estimates for the Potential Host Sites Host Site Option High-Level Construction Cost Budget Estimate NET Power, LLC (NET Power) Demonstration Plant Site in La Porte, Texas $\$$51.4 million EERC Site in North Dakota $\$$43.7 million DGC Site in North Dakota $26.5 million Engineering firm and project partner WSP Engineering (WSP) generated a preliminary capital cost estimate for the pilot plant using the Pre-FEED design basis, as shown in Table ES-2. The accuracy of the capital cost estimate is consistent with the requirements of the Association for the Advancement of Cost Engineering (AACE) Class 4 estimate, i.e., –30%/+50% accuracy range. Operating costs, also presented in Table ES-2, were estimated using WSP cost-estimating practices and were cross-referenced with EERC estimates for operating pilot-scale units. Total cost for construction and installation of the system, 6 months of shakedown testing, and 1.5 years of operation assuming 50% availability was estimated to be $50M. Table ES-2. Preliminary Phase III Cost Estimate for GPSP Allam Cycle Pilot Cost Component Estimated Cost in US$ Detailed Design 5M Installed Equipment Allam Cycle Components Syngas Adjustment System 27M GPSP Interconnections Syngas/O2/CO2 Electrical Cooling Water Waste Gas Wastewater 3M Operational Costs Syngas and Other GPSP Utility Charges Staffing 15M Total Phase III Costs 50M Team commitments were secured for Phase II, which includes industry support from Basin Electric Power Cooperative and ALLETE and up to $2,000,000 cash cost share provided by the North Dakota Industrial Commission. An EIV was completed for the pilot system and no sensitive environmental impacts were identified that might add unexpected risk to the permitting process. Overall, a world-class facility has been secured for hosting the pilot-scale system, and team cost-share commitments for Phase II have been received. An engineering firm, WSP, has committed to performing the FEED study, and technology owner, 8 Rivers, will provide the syngas combustor design. The EIV indicates no significant impacts are expected, and the National Environmental Policy Act process and permitting is expected to be straightforward for this facility.