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ENHANCEMENT OF REACTIVITY IN SURFACTANT-MODIFIED SORBENTS FOR SULFUR DIOXIDE CONTROL
Citation:
Kirchgessner, D. AND W. Jozewicz. ENHANCEMENT OF REACTIVITY IN SURFACTANT-MODIFIED SORBENTS FOR SULFUR DIOXIDE CONTROL. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-89/010.
Description:
The paper discusses the enhancement of reactivity in surfactant-modified sorbents for S02 control. Injecting calcium-based sorbents into the post-flame zone of utility boilers can achieve S02 captures of 50-60% at a stoichiometry of 2. Calcium hydroxide-- Ca(OH)2--appears to be the most effective commercially effective sorbent. Recent attempts to modify Ca(OH)2 by adding calcium lignosulfonate with the water of hydration have succeeded in enhancing its effectiveness. Sulfation experiments in an electrically heated isothermal flow reactor have been used to determine the mechanism of enhancement. Particle size reduction, which in some applications accompanies lignosulfonate addition, does not appear to be required for increased S02 capture. Similarly, the accelerated rate of dehydration observed in modified hydroxides does not appear to be important. The primary cause of increased reactivity in modified sorbents is the ability of the calcium lignosulfonate to retard the rate of sintering, and thus to retain pore volume and reactive surface area. It was also observed that the presence of S02 during calcination affects the structure of sorbents favorably, allowing them to retain higher pore volumes than without S02. This effect may also occur by a slowing of the sintering process, possibly by inhibiting the exchange at pore walls of migrating CaO species with lattice vacancies.