Editing Chemical reactor (section)

==Overview==
[[File:Batch reactor.2.jpg|thumb|left|180px|Cut-away view of a stirred-tank chemical reactor with a cooling jacket]]
[[File:Final half coil vessel.JPG|thumb|left|180px|Chemical reactor with half coils wrapped around it]]
The most common basic types of chemical reactors are tanks (where the reactants mix in the whole volume) and pipes or tubes (for [[laminar flow reactor]]s and [[plug flow reactor]]s)

Both types can be used as continuous reactors or batch reactors, and either may accommodate one or more solids ([[reagent]]s, [[catalyst]]s, or inert materials), but the reagents and products are typically fluids (liquids or gases). Reactors in [[continuous process]]es are typically run at [[steady-state (chemical engineering)|steady-state]], whereas reactors in [[batch production|batch processes]] are necessarily operated in a [[transient state (chemical engineering)|transient state]]. When a reactor is brought into operation, either for the first time or after a shutdown, it is in a transient state, and key [[process variable]]s change with time.

There are three idealised models used to estimate the most important process variables of different chemical reactors:
*[[Batch reactor|Batch reactor model]],
*[[Continuous stirred-tank reactor|Continuous stirred-tank reactor model]] (CSTR), and
*[[Plug flow reactor model]] (PFR).

Many real-world reactors can be modeled as a combination of these basic types.

Key process variables include:
*[[Residence time (fluid dynamics)|Residence time]] (τ, lower case Greek tau)
*Volume (V)
*Temperature (T)
*Pressure (P)
*Concentrations of chemical species (C<sub>1</sub>, C<sub>2</sub>, C<sub>3</sub>, ... C<sub>n</sub>)
*Heat transfer coefficients (h, U)

A tubular reactor can often be a [[packed bed]]. In this case, the tube or channel contains particles or pellets, usually a solid [[Catalysis|catalyst]].<ref name="jakobsen_reactormodeling" /> The reactants, in liquid or gas phase, are pumped through the catalyst bed.<ref name="comsol_packedbed" /> A chemical reactor may also be a [[fluidized bed]]; see [[Fluidized bed reactor]].

Chemical reactions occurring in a reactor may be [[exothermic]], meaning giving off heat, or [[endothermic]], meaning absorbing heat. A tank reactor may have a cooling or heating jacket or cooling or heating coils (tubes) wrapped around the outside of its vessel wall to cool down or heat up the contents, while tubular reactors can be designed like [[heat exchanger]]s if the reaction is strongly [[exothermic process|exothermic]], or like [[Industrial furnace|furnace]]s if the reaction is strongly [[endothermic process|endothermic]].<ref name="peacock_reactors_processcontrol" />