Evaluating fuel diversity
In September 2005, NETL awarded CES $4.5 million to evaluate and develop a coal-based oxy-syngas combustor suitable for a high-efficiency, zero-emissions power plant. Under the same DOE program, Siemens Power Generation received a $14.5 million award to develop high-temperature turbines compatible with the CES combustor. These turbines would be capable of operating at up to 3,200F when fueled by steam/CO2 drive gas.
The three-year CES project will be executed in three phases. In Phase I, CES and Nexant Inc. conducted process modeling to evaluate CES power plant concepts that have the potential to produce power from coal at net cycle efficiencies of >40% (HHV), with CO2 capture by 2015. The models incorporate all major process components depicted in Figure 1, including the combustor, turbines, gasifier, the air separation plant, heat exchangers, and CO2 conditioning unit. The information required to model these components was solicited from Siemens, ConocoPhillips, Air Products and Chemicals Inc., G.C. Broach Co., and Kinder Morgan Inc. CES and its partners modeled and evaluated the potential benefits of integrating subsystems into the overall system to maximize overall plant efficiency and electricity production cost.
CES and Nexant will also investigate power/hydrogen co-production plants. At such plants, hydrogen will be separated from the coal-derived syngas and marketed as a by-product, leaving hydrogen-depleted syngas (HDS) as the fuel for the CES oxy-combustor. This option may be particularly attractive if the objective is to produce hydrogen for off-site use (such as to power fuel cells) while providing a fuel source other than high-value hydrogen for on-site power generation. Although further analysis is required and will be conducted under the aegis of the NETL project, the CES process appears eminently suitable for fueling by HDS.
In conjunction with the Phase I modeling effort, CES operated the existing Kimberlina combustor on simulated coal syngas and HDS. In these tests, a gas blending station was installed at Kimberlina and used to supply the combustor with both fuels. Specifically, the blending station delivered mixtures of CO, H2, CO2, N2, and CH4 to the combustor, which was modified to accommodate the lower-heating-value fuel. Although the tests were limited to firing rates of 5 MWt or less, they enabled CES to assess the performance and combustion/emissions characteristics of the oxy-combustor on coal-derived fuels. Following the tests, CES is exploring options for testing the Kimberlina combustor at a gasification facility, to demonstrate its compatibility with actual coal-derived syngas.
In Phase II of the project, which is currently under way, CES will use data from the 5-MWt tests to design a 50-MWt (nominal) combustor optimized for operation on coal syngas and HDS. In this effort, CES will use its experience and expertise to scale up Kimberlina's existing, 20-MWt natural gas combustor. In Phase III, CES will fabricate the combustor and install and test it either at Kimberlina or at another location.
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