Catalysis of the combustion of synthetic char particles by various forms of calcium additives

Abstract

The reactivity of calcium-laden carbonaceous particles to oxygen was investigated in the range 670-3000 K. The char particles were prepared from poly(furfural alcohol) (PFA) and were spherical and of uniform size. Three different methods were used to introduce the calcium additive: precipitation of calcium carbonate, impregnation with calcium acetate, and calcium ion exchange. Electron microscopy showed that the distribution of calcium was remarkably uniform in particles containing a bimodal distribution of micropores and transitional pores, whereas for particles with micropores only the Ca concentration was high at the surface and low at the center. X-ray analysis indicated that the conversion of the carbonate to the oxide at low temperatures (below 900 K) takes place only after all carbon has been consumed. Combustion studies showed that the calcium catalyzed the oxidation reaction at all temperatures investigated by up to 2 orders of magnitude. The effectiveness of the catalyst introduced by the different methods was comparable, with the calcium ion exchanged chars being, in general, the most reactive.

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