The industrial production of styrene from vinylacetylene is essentially an irrev
ID: 530586 • Letter: T
Question
The industrial production of styrene from vinylacetylene is essentially an irreversible reaction that follows an elementary rate law : 2 vinylacetylene styrene As a newly assigned engineer, you were asked by the plant manager to provide all of these information within two working weeks : a. Calculate the conversion that can be achieved if the reaction if it is carried out in a readily available PFR reactor having a volume of 10dm3 . The entering temperature is fixed at 400 oC. Feed flow is being heated using a heat exchanger. b. Analyse the performance of the reactor by plotting graphs of temperature and conversion along the length of the reactor. c. Vary the entering temperature and plot the conversion as a function of entering temperature. d. Vary the ambient temperature of the heat exchanger and find the maximum ambient temperature for the reaction to take place in the reactor. e. Please provide (a) to (d) information with the case when the reaction is carried out adiabatically. Compare and discuss on the differences between these information. f. Repeat part (b) assuming that the reaction is reversible, having Kc = 100,000 at 400oC. In addition, a stream of inerts (CA = 100 J/mol.oC) with FI = 3FA0 enters the reactor. Plot the conversion as a function of the entering temperature. Additional information : CA0 = 1 mol/dm3 Ua = 5.0 kJ/s.dm3 /K FA0 = 5 mol/s Ta = 700 K HRX = -231- 0.012(T-298) kJ/mol T0 = 673 K CPA = 0.1222 kJ/mol.K k = 1.48 x 1011 exp (-19,124/T) dm3 /mol.s
Explanation / Answer
DHRx4T = -30,000 kJ kmole toluene Heat capacity of propylene = 120 J mole K-r4T = r(1- f) exp 10.4 - 12000K T é ë ù û PC2H4 PT in kmol toluene m3
Mole Balance: dX
dV = -rA FAo
Rate Law : - rA =- kCA 2
Stoichiometry: CA =
CAo(1-X)
(1+ eX)
where =y Aod = 1* (0.5 -1) = -0.5
Energy Equation :
dT dV = Ua(Ta - T) + (-rA ) -DHrx ( )
åFiC Pi
CPA = 0.12222 kJ/mol K
DHrx = -231-0.012(T-298)
DCP =- 0.012
CPB = CPA +DCP
Note : DCP is an order of magnitude lower than CPA
Therefore, CPA @ CPB
Hence, åFiC
Pi= FACPA + FBCPB @ FAoCPA (as used in the code below)
Or åFiC
Pi = FAo åQiC Pi ( + DCPX) = FAo (FAoCPi + DCPX ·
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