(646b) Cryogenic Pollutant Balances

A side benefit of cryogenic carbon capture is the removal of other pollutants such as Hg, HCl, SO2, SO3, NO2, and NO. While cryogenic carbon capture alone can be an expensive process, the ability to remove these other pollutants within the same cycle provides an added economic benefit. Although Hg, HCl, SO2, SO3, NO2, and NO are common pollutants, not much is known about their properties at -135 ⁰C. We extrapolated the partial pressures of these pollutants from the data and equations on DIPPR database to predict the remainder of these pollutants in the flue gas. However, these extrapolations may not be very accurate as there is no data for many of these pollutants below 200K and they assume equilibrium.

We are currently running experiments to verify our model and to understand how much SO2 will be removed at these temperatures. A sample of flue gas from a methane and coal reactor is collected and pumped through a desiccant, filter, and a heat exchanger. The flue gas flows through the heat exchanger and to the gas analyzer, which measures the concentration of SO2, NO, CO, CO2, and O2. The system reaches steady state before any cooling has been done to get an accurate measure of the flue gas composition. A computer is hooked up to the gas analyzer and thermocouples, providing accurate data corresponding to temperature and gas composition. Liquid nitrogen is used as a cooling fluid in the heat exchanger. With this set-up temperatures can be brought down to -130°C. The composition of the gas is recorded while the cooling is done for analysis. We have been able to successfully remove SO2 from 250ppm to 17 ppm, or a 90%+ removal. We are also able to consistently remove 99% of the CO2 from the flue gas.

Cryogenic carbon capture is an effective method to remove CO2 with the potential to replace scrubbers and other flue gas treatment methods. This technology becomes much more economically beneficially with its ability to compliment and even replace some flue gas treatments currently employed.