A Test and Demonstration Unit for Concentrating Sulfur Dioxide from Flue Gas

A bench-scale system to continuously separate and concentrate SO2 from flue gas has been developed and tested. The separation is accomplished due to the relative adsorption strengths of SO2 and water on a synthetic mordenite, a phenomenon known as rollup. The continuous concentration system (CCS) is comprised of two pairs of packed beds that cycle between cleaning, roll-up, and regeneration modes. The bed pairs behave identically, with cycles staggered by half of one adsorption−desorption−regeneration period. The cycle for each pair involves regeneration of one bed with dry air, while the other is cleaning the flue gas and subsequently rolling up the SO2. This bench-scale CCS is able to split a 6 standard liters per minute (SLPM) gas stream containing 2000 ppm SO2 into two streams of equal flowrate, one containing 3400 ppm SO2 and the other 70 ppm SO2. The influence of water is strong, with the rollup being optimal at 13% moisture in the flue gas. Adsorption starting with the bed at 75 °C is optimal, and air regeneration at 200 °C and 8 SLPM for 76 min is adequate. An economic analysis of an industrial-scaled CCS capable of treating a 1 000 000 scfm flue gas stream containing 2000 ppm SO2 (typical of a 400-MW coal-fired power plant) was conducted. The CCS installation permits smaller flue gas scrubbers to be installed and can potentially save a 400-MW power plant $2.6 million in annual operating costs.