Mixing effects of high-speed jets in gas-solid riser and downer reactors

For the high-temperature and short-contact time gas-solid reaction process, riser and downer are considered appropriate reactors. To realize an intensive and complete mixing of reactants with catalysts, the feed raw is always introduced in the form of high-speed jets. In this study, in order to investigate the mixing effects of different types of high-speed jets in riser and downer, traceable ozone is injected with the high-speed feed jets to react with catalyst particles. By detecting the decomposition of ozone, the gas-solid mixing and reaction in riser and downer under the influence of both co-current and counter-current injections are analyzed. The relative ozone concentration is used to reflect the location reaction extent and its radial nonuniformity index is proposed to compare the results in riser and downer. It is found that the jet influence zone in downer provides a relatively better environment for the mixing of feed jets with catalysts. In the riser, introduction of counter-current injections could improve the uniformity of gas-solid mixing in the initial contact region of feed with catalysts.