Adiabatic Plug Flow Reactor with Recycle

An adiabatic plug flow reactor (PFR) with recycle is used to carry out a first-order reaction. The fresh feed inlet temperature and concentration are known, but the inlet temperature and the inlet concentration to the PFR are not. Since and the inlet concentration are initial conditions needed to solve the differential equations for the mass and energy balances for the PFR, an iterative solution is needed. The value of can be calculated only when the differential equations are solved for . Thus, the value of is guessed using the slider (and the feed concentration to the reactor calculated using the adiabatic relation between temperature and concentration), and the exit temperature from the PFR is then obtained from the solution of the differential equations. The estimated value of is adjusted until the calculated value of (arrow in figure on left) equals the known (the green circle); multiple solutions are possible under some conditions. High recycle ratios approach continuous-stirred tank reactor (CSTR) behavior. A plot of temperature as a function of distance down the PFR is generated. The inlet temperature to the system and the recycle ratio can be varied.


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Mass and energy balance:
is the temperature of reaction ()
is the length down the reactor ()
is the velocity of stream exiting reactor ()
is the concentration of A entering reactor ()
is the volumetric heat capacity ()
is the heat of reaction ()
is the rate constant ()
is the concentration of reactant ()
is the pre-exponential factor ()
is the temperature of stream entering reactor ()
is the activation energy ()
is the ideal gas constant ()
is the temperature of fresh feed calculated from the guess ()
is the recycle ratio
is the temperature of stream exiting reactor ()
is the velocity of fresh feed ()
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