Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?
Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur Graph Search.
Concept
Continuous stirred-tank reactor
Résumé
The continuous stirred-tank reactor (CSTR), also known as vat- or backmix reactor, mixed flow reactor (MFR), or a continuous-flow stirred-tank reactor (CFSTR), 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 (PFR). In practice, no reactors behave ideally but instead fall somewhere in between the mixing limits of an ideal CSTR and PFR.
A continuous fluid flow containing non-conservative chemical reactant A enters an ideal CSTR of volume V.
Assumptions:
perfect or ideal mixing
steady state , where NA is the number of moles of species A
closed boundaries
constant fluid density (valid for most liquids; valid for gases only if there is no net change in the number of moles or drastic temperature change)
nth-order reaction (r = kCAn), where k is the reaction rate constant, CA is the concentration of species A, and n is the order of the reaction
isothermal conditions, or constant temperature (k is constant)
single, irreversible reaction (νA = −1)
All reactant A is converted to products via chemical reaction
NA = CA V
Integral mass balance on number of moles NA of species A in a reactor of volume V:
where,
FAo is the molar flow rate inlet of species A
FA is the molar flow rate outlet of species A
vA is the stoichiometric coefficient
rA is the reaction rate
Applying the assumptions of steady state and νA = −1, Equation 2 simplifies to:
The molar flow rates of species A can then be rewritten in terms of the concentration of A and the fluid flow rate (Q):
Equation 4 can then be rearranged to isolate rA and simplified:
where,
is the theoretical residence time ()
CAo is the inlet concentration of species A
CA is the reactor/outlet concentration of species A
Residence time is the total amount of time a discrete quantity of reagent spends inside the reactor.
Source officielle
À propos de ce résultat
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.