Continuous-flow Stirred Tank Reactor (CSTR): A reaction vessel in which the feed is continuously added, and the products continuously removed. The vessel (tank) is continuously stirred to maintain a uniform concentration within the vessel.
Plug Flow Reactor (PFR): A plug flow reactor is a tubular reactor where the feed is continuously introduced at one end and the products continuously removed from the other end. The concentration/temperature profile in the reactor varies with position.
Batch Reactor: In a batch reactor, the reactants are added to the reactor at the start of the reaction. The reactants are allowed to react in the reactor for a fixed time. No feed is added or product withdrawn during this time. The reaction products are removed at the end of the batch.
Semi-Batch Reactor: In a semi-batch reactor, some reactants are added to the reactor at the start of the batch, while others are fed intermittently or continuously during the course of the reaction.