While Petra Nova is the only facility of its kind in the U.S., and only other coal-fired power plant with CCS is the 110 megawatts (MW) Boundary Dam plant in Saskatchewan, Canada, near the border with North Dakota, according to the U.S. Energy Information Agency (EIA).
A third plant in Kemper County, Mississippi, is capable of burning natural gas or lignite coal. The Kemper plant was supposed to be fully operational as a power plant with CCS technologies by mid-2014. But, since 2014, Kemper has operated as a combined-cycle plant.
However, as was reported by Digital Journal in June 2017, Mississippi Power made the decision to suspend operations activities relating to the coal gasification process at Kemper, operating the facility strictly as a natural gas-fired combined-cycle plant.
The decision to abandon CCS technologies at Kemper was actually due to two key problems, one being the project was plagued with leaks and other problems resulting in increased costs of over $7.5 billion. The second problem was President Trump’s budget cuts that called for slashing research and development (R&D) on capturing carbon dioxide from fossil fuel combustion and producing cleaner coal technologies.
The Petra Nova Project
Petra Nova is a 50/50 joint venture between NRG Energy and JX Nippon Oil & Gas Exploration. Petra Nova operates as a commercial-scale post-combustion carbon capture facility at NRG’s W.A. Parish coal-fired generating station southwest of Houston, Texas. The W.A. Parrish facility began operations in 1977 and carbon capture began operations on January 10, 2017.
The project uses a proven carbon capture process, which was jointly developed by Mitsubishi Heavy Industries, Ltd. and the Kansai Electric Power Co., that uses a high-performance solvent for CO2 absorption and desorption.
The facility is capable of removing 90 percent of the carbon dioxide from a 240 MW slipstream of flue gas for the use and ultimate sequestration of 1.6 million tons of this greenhouse gas annually. The captured carbon dioxide is then compressed and piped about 82 miles to West Ranch Oil Field, Texas, which is operated by Hilcorp Energy Company. The nearly 99 percent pure CO2 is then used for enhanced oil recovery.
The CCS technology configerations
You could say there are three different configurations of technologies for capturing carbon dioxide – post-combustion, pre-combustion, and oxyfuel combustion. They are all meant to stop the release of carbon dioxide from the combustion of fossil fuels.
Post-combustion capture involves sending the power plant’s emissions through an absorption process where a solvent captures up to 90 percent of the CO2. The recovered CO2 goes through a regenerator that strips the CO2 from the solvent while the remaining emissions, usually nitrogen, are vented to the atmosphere. This is what Petra Nova uses.
With oxy-combustion capture, the fossil fuel is burned in pure oxygen instead of air. The result of this process captures nearly pure CO2 without the worry over impurities that could corrode pipelines. On the other hand, with pre-combustion capture, the fossil fuel is turned into a synthetic gas consisting of relatively pure hydrogen and CO2.
In Petra Nova’s energy-intensive post-combustion capture process, a dedicated natural gas unit is required to accommodate the energy requirements of the carbon-capture process. It’s interesting to note that the Kemper project in Mississippi was supposed to use a pre-combustion system, that would capture only 65 percent of the plant’s CO2. However, Petra Nova CCS retrofit costs were reported to be $1 billion, or $4,200/kW, and the project was completed on budget and on time, according to Daily Energy. Insider.
