A Low-Energy Low-Cost Process for Stripping Carbon Dioxide from Absorbents

If CO2 could be scrubbed from the flue gas of power plants and safely sequestered, the country¿s most important source of electricity, fossil-fired power plants, could operate without emitting significant amounts of greenhouse gases. Although technology for scrubbing CO2 from the flue gas of a power plant is commercially available, it is far too expensive and requires too much energy to be widely deployed. This project will develop technology to reduce the costs and energy requirements for the stripper of a CO2 scrubber, with the objective of making CO2 scrubbing an affordable technology for controlling emissions. Phase I will study the feasibility of using plastic heat exchangers, which are now being commercialized in HVAC applications, as an internally heated contactor and a cross exchanger in a CO2 stripper. Small-scale bench-top experiments will be conducted to measure the heat and mass transfer coefficients in the internally-heated contactor that forms the core of the stripper. This data will be used to prepare a conceptual design for a large-scale stripper. A plastic-plate heat exchanger, which could be used as the cross exchanger, will be designed. Finally, an engineering analysis will be performed to estimate the impact of the plastic heat exchangers on the cost and energy-use of an advanced CO2 scrubber for a 500 MW pulverized-fuel power plant. Commercial Applications and Other Benefits as described by the awardee: The advanced stripper should limit CO2 emissions at the stack of the power plant, providng: (1) a 32% reduction in the capital cost for the scrubber, (2) much lower maintenance costs (due to the replacement of steel heat transfer surfaces with corrosion-resistant plastic), and (3) when used with advanced solvents, a more than 50% reduction in the thermal energy required to operate the scrubber. In addition, the absorption of acid gases is an important part of many chemical processes, including the cleaning of raw natural gas and the removal of CO2 from synthesis gas; consequently, the plastic heat exchanger technology could become an important part of processes that produce a carbon-free fuel from coal and natural gas.