This review examines the key features and configurations of short residence time cracking processes from a diverse range of industries that have been developed over the past 25 years. These industries include: bitumen or heavy oil upgrading, biomass pyrolysis, olefin production, catalytic cracking, and coal gasification. Characterization of the gas, liquid, and solid products and feedstock is provided wherever possible. In addition, a description of the source and mechanism of heat transfer, and how the feedstock is brought into contact with and separated from – this source is also given.

There is a strong economic incentive for considering short residence time cracking processes. Not only do such processes increase the yields of the more valuable liquid and gaseous products, but more compact designs would also decrease capital costs. Careful control of the vapour residence times appears to be crucial in order to prevent secondary cracking and yet allow for maximum cracking of the feedstock. Rapid and thorough mixing of the feedstock with the heat source, not just creating a uniform dispersion, is also a key design aspect to consider. Finally, rapid and complete separation must also be carefully considered; again, to help control product residence time and avoid secondary cracking but also from a heat balance point of view.