Fluid treatment apparatus and process

Fluid treatment apparatus for conducting a physical or chemical reaction in which a slurry and a gas are contacted such that the slurry and at least a component of the gas partake in the physical or chemical reaction, the fluid treatment apparatus comprising at least two chambers being first and second chambers through which a fluid can flow, the two chambers being separated by at least one choke nozzle which has an entrance in the first chamber and an exit in the second chamber, wherein the choke nozzle comprises a converging section at its entrance, a throat section, a backward-facing step immediately after the throat section, and an exit section at its exit which opens into the second chamber wherein the choke nozzle is configured to promote cavitation resulting from choked flow wherein the apparatus includes one or more gas inlets having their axes extending transversely at an offset in a generally tangential direction relative to slurry flow so that a swirling action of diffusing gas in the slurry results, the apparatus being characterized in that mixing nozzles are included in the apparatus for mixing fluids either before they enter a choke nozzle or after they leave a choke nozzle, or both and wherein a mixing nozzle has a converging section at its entrance, a throat section, a backward-facing step immediately after the throat section, and an exit section at its exit which opens into a downstream chamber.