Feasibility of Integrating Carbon Capture and Storage and Desalination into a Natural Gas Fired Power Plant in Wyoming

Abstract

Power plants withdraw huge amounts of fresh water from local sources and emit high levels of greenhouse gases. With increasing uncertainty surrounding fresh water availability and the future of greenhouse gas emissions regulations, power plants are being forced to adapt. Power plants could address both of these problems with the addition of carbon capture and storage (CCS) and desalination. By capturing carbon dioxide and sequestering it in saline aquifers, plants could drastically reduce their carbon emissions. Brine extraction from these aquifers could provide the feed for a desalination system, which could use waste heat from the power plant to produce enough fresh water to cover the plant’s water requirements. This thesis is an analysis of one such plant: a chemically recuperated gas turbine (CRGT) plant integrated with carbon capture and multi-effect desalination (MED). This plant is simulated using Aspen Plus software in order to determine power output, water consumption, and efficiency. Heat integration is performed in order to maximize efficiency while minimizing the need for additional utilities. Several systems are tested, with and without carbon capture and MED, in order to compare the effects of these additions. Each system uses 75,000 kg/hr of natural gas and produces 500-600 MW of electricity. These simulations are also compared to a typical natural gas combined cycle (NGCC) plant to determine the conditions under which a CRGT system is economically feasible. The addition of carbon capture results in a 3.3% decrease in efficiency. The penalty for adding CCS is much smaller for a CRGT than an NGCC system, which has a 14.7% efficiency penalty. In addition, even at high fuel prices and high carbon emissions prices, a CRGT system could be favored economically if the capital cost of the plant was sufficiently lower than that of an NGCC plant. Due to the fact that an NGCC plant cannot integrate desalination without reducing the plant’s efficiency, a CRGT plant with desalination is extremely advantageous in the case of water scarcity, as all systems with MED have no raw water consumption. A more detailed capital cost analysis of a CRGT system with CCS and MED would allow a more definite conclusion to be drawn regarding the economic feasibility of such a plant.