In chemical engineering it is generally understood to be a process vessel used to carry out a chemical reaction which is one of the classic unit operations in chemical process analysis.
Types: 1) Batch Reactor 2) Continuous Stirred Tank Reactor (CSTR) 3) Catalytic Reactor
The simplest type of reactor is a batch reactor. Materials are loaded into a batch reactor, and the reaction proceeds with time. In a CSTR, one or more fluid reagents are introduced into a tank reactor which is typically stirred with an impeller to ensure proper mixing of the reagents while the reactor effluent is removed.
A tubular reactor can often be a packed bed. In this case, the tube or channel contains particles or pellets, usually a solid catalyst. The reactants, in liquid or gas phase, are pumped through the catalyst bed. It is also be a fluidized bed.