page_title: Continuous stirred-tank reactor
section_title: Applications
hierarchical_section_title: Continuous stirred-tank reactor / Applications
caption_attribution_description: English: Newtown Creek Wastewater Treatment Plant. Looking west across Kingsland Avenue at three of the eight large sewage digester tanks built at the turn of the century, north of Greenpoint Avenue in Greenpoint, Brooklyn.
context_page_description: The continuous stirred-tank reactor, also known as vat- or backmix reactor, mixed flow reactor, or a continuous-flow stirred-tank reactor, is a common model for a chemical reactor in chemical engineering and environmental engineering. A CSTR often refers to a model used to estimate the key unit operation variables when using a continuous agitated-tank reactor to reach a specified output. The mathematical model works for all fluids: liquids, gases, and slurries.
  The behavior of a CSTR is often approximated or modeled by that of an ideal CSTR, which assumes perfect mixing. In a perfectly mixed reactor, reagent is instantaneously and uniformly mixed throughout the reactor upon entry. Consequently, the output composition is identical to composition of the material inside the reactor, which is a function of residence time and reaction rate. The CSTR is the ideal limit of complete mixing in reactor design, which is the complete opposite of a plug flow reactor. In practice, no reactors behave ideally but instead fall somewhere in between the mixing limits of an ideal CSTR and PFR.
context_section_description: CSTRs facilitate rapid dilution of reagents through mixing. Therefore, for non-zero-order reactions, the low concentration of reagent in the reactor means a CSTR will be less efficient at removing the reagent compared to a PFR with the same residence time. Therefore, CSTRs are typically larger than PFRs, which may be a challenge in applications where space is limited. However, one of the added benefits of dilution in CSTRs is the ability to neutralize shocks to the system. As opposed to PFRs, the performance of CSTRs is less susceptible to changes in the influent composition, which makes it ideal for a variety of industrial applications:
  Environmental engineering
  Activated sludge process for wastewater treatment
  Lagoon treatment systems for natural wastewater treatment
  Anaerobic digesters for the stabilization of wastewater biosolids
  Chemical engineering
  Loop reactor for pharmaceutical production
  Fermentation
  Biogas production
caption: Anaerobic digesters at Newtown Creek Wastewater Treatment Plant in Greenpoint, Brooklyn.
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