Editing Chemical reactor (section)

===PFR (plug flow reactor)===
[[File:Pipe-PFR.svg|thumb|350px|Simple diagram illustrating [[plug flow reactor model]]]]
{{Main|Plug flow reactor model}}
In a PFR, sometimes called continuous tubular reactor (CTR),<ref name="vapourtec_plugflowreactor" /> one or more fluid reagents are [[pump]]ed through a pipe or tube. The chemical reaction proceeds as the reagents travel through the PFR. In this type of reactor, the changing reaction rate creates a [[gradient]] with respect to distance traversed; at the inlet to the PFR the rate is very high, but as the concentrations of the reagents decrease and the concentration of the product(s) increases the reaction rate slows. Some important aspects of the PFR:
*The idealized PFR model assumes no axial mixing: any element of fluid traveling through the reactor doesn't mix with fluid upstream or downstream from it, as implied by the term "[[plug flow]]".
*Reagents may be introduced into the PFR at locations in the reactor other than the inlet. In this way, a higher efficiency may be obtained, or the size and cost of the PFR may be reduced.
*A PFR has a higher theoretical efficiency than a CSTR of the same volume. That is, given the same space-time (or residence time), a reaction will proceed to a higher percentage completion in a PFR than in a CSTR. This is not always true for reversible reactions.

For most chemical reactions of industrial interest, it is impossible for the reaction to proceed to 100% completion. The rate of reaction decreases as the reactants are consumed until the point where the system reaches dynamic equilibrium (no net reaction, or change in chemical species occurs). The equilibrium point for most systems is less than 100% complete. For this reason a separation process, such as [[distillation]], often follows a chemical reactor in order to separate any remaining reagents or byproducts from the desired product. These reagents may sometimes be reused at the beginning of the process, such as in the [[Haber process]]. In some cases, very large reactors would be necessary to approach equilibrium, and chemical engineers may choose to separate the partially reacted mixture and recycle the leftover reactants.

Under [[laminar flow]] conditions, the assumption of plug flow is highly inaccurate, as the fluid traveling through the center of the tube moves much faster than the fluid at the wall. The continuous [[oscillatory baffled reactor]] (COBR) achieves thorough mixing by the combination of fluid [[oscillation]] and orifice baffles, allowing plug flow to be approximated under [[laminar flow]] conditions.