DISPERSION AND COMBUSTION OF A BITUMEN-BASED EMULSION IN BUBBLING FLUIDIZED BED

An experimental program was carried out with ORIMULSION as a part of an R&D project aimed at demonstrating the feasibility of contemporary combustion and desulfurization in atmospheric bubbling fluidized bed. ORIMULSION is a bitumen-based emulsion that is produced in Venezuela's Orinoco region with 30% w/w water and about 3% w/w sulfur content (on a dry basis). Two atmospheric, pre-pilot, bubbling bed units were used: a 140 mm ID reactor and a 370 mm ID combustor. The first one provides qualitative and quantitative information on dispersion and in-bed retention of ORIMULSION: to this end the bed is operated batchwise in hot tests without combustion and the fuel can be injected into the bed with or without a gaseous atomization stream. With the second one, steady-state combustion tests are carried out under typical conditions of bubbling FBC. The outcome of the experiments and the significance of the results are fully discussed in the paper with reference to the ORIMULSION combustion mechanism. Among the other findings, the following ones appear particularly relevant. 1. A carbon "condensed phase" is actually formed with the structure of tiny carbon deposits on bed particles, but at a very low rate; as a consequence, combustion (and pollutant formation) is dominated by homogeneous mechanisms. 2. Combustion efficiency is always very high, with values approaching 100% in those tests with higher excess air. The in-bed combustion efficiency is enhanced by those fuel injection conditions that lead to dispersion into fine droplets and to effective mixing within the bed; therefore, contrarily to the case of water suspensions of solid fuels, intense atomization of ORIMULSION is recommended.