You are an engineer who is to design a CSTR for the elementary consecutive gas-p
ID: 535364 • Letter: Y
Question
You are an engineer who is to design a CSTR for the elementary consecutive gas-phase reactions The feed conditions and desired product specifications are known, together with the temperature of the heating medium. It is your job to design the reactor, that is, to specify the reactor volume and the area of the heating co inside the reactor. Calculate the desired operating temperature inside the reactor. (ANS: 269 degree F) Calculate the volume of the reactor. (ANS: 6.58 ft^3) Calculate the area of the heating coil. (ANS: 18.1 ft^2) Find a set of conditions that will give multiple steady states if reaction 1 is exothermic rather than endothermic. How many steady states can you find? (ANS: 5) Make a plot of G(T) vs. R(T) and of T_s vs. T_0. Additional Information Product: The ratio C_B/C_C is equal to 10. 50% of A in the feed is converted. Feed: The feed is gas-phase and pure A. The molar flow rate is 0.05 lb mol/s. The volumetric flow rate is 7.85 ft^3/s. The temperature is 400 degree F The pressure in the reactor is 4 atm. Heat Capacities: C_ps of A, B, and C are all 25 Btu/(lb mol degree F) Reaction 1: Reaction 2: A_1 = 2 times 10^9 s^-1 A_2 = 1 times 10^11 s^-1 E_1 = 31,000 Btu/lb mol E_2 = 40,000 Btu/lb mol Delta H_ = 15,000 Btu/lb mol A reacted Delta H_ = -20,000 Btu/lb mol C reacted Heat transfer: The heating medium is saturated high-pressure steam at 350 degree F. The overall heat-transfer coefficient between the heating medium and the reaction mixture is 400 Btu/(h ft^2 degree F).Explanation / Answer
Answer:
Assuming that:
a) both the reaction in series are first order reaction
b) B is the desired product,
we will calculate some basics:
Initial conc. of A, CAo= molar feed rate/ vol. feed rate = 0.05/7.85 = 0.0064 lbmol/ft3
As given only 50% of A is converted
CA = CAo (1-XA) = 0.0032 lbmol/ft3
Also
CA + CB +Cc = CA0
And CB/ Cc = 10
Using them we have
CB = 0.0029 lbmol/ft3
Cc = 0.00029 lbmol/ft3
The optimum space time m = 1/(k1 k2)^1/2)
B) Volume of the CSTR = m X vo X (fraction conversion)
=5.6 ft3
A) operating temperature of the reactor
the overall heat of reaction can be calculated
Hr = Hof react - H of products
=5000 btu /lbmol = C (t - tr)
= 200 F
Remark: I have doubts with the k values of the ques.
C) Area of the heating coil
UA(t-tr) = XHr -cp(t-tr)
A = 6.25 ft3
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