Abstract: A multi-stage loop reactor, employed in various gas-liquid or gas-liquid-solid chemical reaction systems, which comprises a reactor body, draft tube(s) inside the reactor body, and a gas distributor at the bottom of draft tube. The draft tube can include one or more sections. The multi-stage loop reactor of the present invention has a higher mass transfer rate because the different phases are well mixed throughout the reactor, and the gas bubbles are distributed evenly everywhere. The reactor of this invention can be extensively applied in various gas-liquid or gas-liquid-solid reaction processes including the oxidization process, hydrogenation process, hydrocracking process, coal liquification process, fermentation process, hydrocarbon processing process, and biological treatment of waste water, etc.

Abstract: An apparatus and method are disclosed for environmental applications such as waste water treatment, de-inking of recycled paper, chemical/biochemical waste clean-up, and mineral beneficiation, using a multi-stage flotation column. A series of draft tubes arranged axially and separated by baffles provides individual mixing stages in the flotation column and a special gas distributor generates fine gas bubbles. The draft tubes create repetitive loop flow of the feed fluid in each flotation stage. This provides uniform distribution of the gas bubbles throughout the column and significantly enhances mixing and contacts of the gas bubbles with the impurities to be removed.