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Spent limestone samples from the bed and baghouse of a 22 MWe circulating fluidized bed (CFB) boiler were hydrated and then sulphated in a thermogravimetric analyzer under conditions similar to those found in CFB combustors (850°C, 0.3% SO2, 9% O2, 9% CO2 and 81.7% N2). Hydration using water gave faster rates and higher levels of conversion of the residual CaO to Ca (OH)2 than immersion in pure steam at 150 and 200°C. The particles expanded during hydration and their internal volume increased from 0.1 cm3/g Ca before hydration to nearly 0.6 cm3/g Ca after dehydration. Hydration rejuvenated the reactivity of the bed material but not that of the baghouse particles. The conversion of Ca to CaSO4, in the treated bed particles increased from 32% to over 80% during re‐sulphation.

Chemical Vapor Deposition ͑CVD͒ of silicon dioxide from tetraethoxysilane ͑TEOS͒ and ozone was modeled using CHEMKIN-III simulation software. Modeling assumed that film growth proceeds via the fast oxidation of silicon-bearing compounds by ozone or atomic oxygen at the substrate surface. The objective of the study was to use kinetic data from the literature to develop a reliable reaction model with no more than one adjustable parameter. The simulations established that direct contribution of TEOS surface reactions to film growth is negligible in TEOS/ozone CVD. Depositions at low TEOS flow rates are controlled by diffusion of intermediate silicon-containing compounds formed in the gas phase by reaction of TEOS with atomic oxygen. The depletion of ozone or atomic oxygen within the reactive boundary layer becomes rate limiting at high TEOS flows, while gas-phase polymerization reactions reduce the rate at high pressures. Close agreement with the published rate data was obtained for reactions at 643 K but discrepancies remain at higher deposition temperatures. It is believed that the model overpredicts the formation rate of intermediates at high temperatures because the mechanism fails to fully account for gas-phase oxidation reactions between atomic oxygen and the organic fragments from TEOS oxidation reactions.