Editing Chemical reactor (section)

===CSTR (continuous stirred-tank reactor)===
{{Main|Continuous stirred-tank reactor}}
[[File:Chemical reactor CSTR AISI 316.JPG|thumb|350px|right|Checking condition inside the case of a [[continuous stirred tank reactor]] (CSTR). The [[impeller]] (or agitator) blades on the shaft aid [[mixing (process engineering)|mixing]].
The [[baffle (in vessel)|baffle]] at the bottom of the image also helps in mixing.]]
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. Dividing the volume of the tank by the average [[volumetric flow rate]] through the tank gives the [[space time (chemical engineering)|space time]], or the time required to process one reactor volume of fluid. Using [[chemical kinetics]], the reaction's expected [[percent]] completion can be calculated. Some important aspects of the CSTR:
*At steady-state, the mass flow rate in must equal the mass flow rate out, otherwise the tank will overflow or go empty (transient state). While the reactor is in a transient state the model equation must be derived from the differential mass and energy balances.
*The reaction proceeds at the reaction rate associated with the final (output) concentration, since the concentration is assumed to be homogenous throughout the reactor.
*Often, it is economically beneficial to operate several CSTRs in series. This allows, for example, the first CSTR to operate at a higher reagent concentration and therefore a higher reaction rate. In these cases, the sizes of the reactors may be varied in order to minimize the total [[capital investment]] required to implement the process.
*It can be demonstrated that an [[infinity|infinite]] number of infinitely small CSTRs operating in series would be equivalent to a PFR.<ref name="ravi_reactioneng" />
The behavior of a CSTR is often approximated or modeled by that of a Continuous Ideally Stirred-Tank Reactor (CISTR). All calculations performed with CISTRs assume [[perfect mixing]]. If the residence time is 5-10 times the mixing time, this approximation is considered valid for engineering purposes. The CISTR model is often used to simplify engineering calculations and can be used to describe research reactors. In practice it can only be approached, particularly in industrial size reactors in which the mixing time may be very large.

A loop reactor is a hybrid type of catalytic reactor that physically resembles a tubular reactor, but operates like a CSTR. The reaction mixture is circulated in a loop of tube, surrounded by a jacket for cooling or heating, and there is a continuous flow of starting material in and product out.