Combined scCO ₂-EGS IGCC to reduce carbon emissions from power generation in the desert Southwestern United States (New Mexico)

We explore the feasibility of combining integrated gasification combined cycle (IGCC) generation of electricity from the oxy-gasification of coal with the circulation of the resulting supercritical CO ₂ in EGS reservoirs (scCO ₂-EGS). These technologies are symbiotic as the effluent stream from the IGCC may be directly used within the scCO ₂-EGS. The inputs to the IGCC are coal and air that is first separated into nitrogen and oxygen. The coal is gasified in the presence of oxygen alone and used to produce synthesis gas (CO) that is then water-gas shifted to produce CO ₂ and H ₂. Of these two products, the CO ₂ is used as the heat transfer fluid within the EGS and the H ₂ is combusted with air to produce water. The principal benefits of the IGCC plants are its concentrated emission of CO ₂ only, a minor production of water to augment the water used in the reaction and essentially no other effluents. For a proposed plant located near Albuquerque, NM a 550 MW IGCC scales to a CO ₂ output of ∼80 kg/s as make-up fluid for the EGS. For anticipated leak-off rates of the order of 5-10%, this results in reservoir circulation rates of 1600-800 kg/s. For this particular site, with a 5 km deep injector well tapping a 200C reservoir, these circulation rates, at 100 kg/s per well, result in a thermal output of ∼300-150 MW-thermal to augment the 550 MWe from the IGCC. This plant will save emissions of 8,200 tons of NOx, 20,000 tons of SO ₂ and 4.35 million tons of CO ₂ emissions each year compared to a conventional fossil fuel power plant. An economic analysis for the combined scCO ₂-EGS-IGCC system determines the Net Present Value (NPV) of the overall system and establishes probable payback periods based on the cost of electricity, possible electricity inflation rates, and the possibility of governmental funding for carbon capture and storage (CCS). The total capital cost and operational costs for the combined systems are $1.7 billion (IGCC) and $190 million (EGS), respectively. The assessment estimates that in the worst-case scenario (no increase in electricity prices and absent government funds to subsidize CCS) the system will pay for itself in its 8 ^th year of operation. In this case the final present worth of the project over the 30 year lifetime would be $3 billion and have an Return on Investment (ROI) of 91%. The best-case scenario results in a Payback Time (PBT) of 6 years, a $5.5 billion total present worth over 30 years, and an ROI of 223%.