Page 58 - Elements of Chemical Reaction Engineering Ebook

Chap. 1 Questions and Problems 29

Pl-11, The reaction
A+B

is to be carried out isothermally in a continuous-flow reactor. Calculate both
the CSTR and PFR reactor volumes necessary to consume 99% of A i(i.e.,
CA = o.cl1cAQ) when the entering molar flow rate is 5 moVh, assuming the
reaction rate -rA is:
mol
(Ans.: V = 99 dm3)
(a) -rA = k with k = 0.05 -
hedm3
(b) -rA = kCA with k = 0.0001 s-'
dm3
(e) -rA = kCi with k = 3 - (Am.: V,,,, = 66,000 dm3)
mol. h
The entering volumetric flow rate is 10 dm3/h. [Note: FA = CAu. For a con-
stant volumetric flow rate u = uo, then FA = CAu,. Also, cAo = FAOIuO =
(5 mol/h)/(lO dm3/h) = 0.5 mol/dm3 .]
P1-12c The gas-phase reaction
A --+ B+C
is carried out isothermally in a 20-dm3 constant-volume batch reactor. Twenty
moles of pure A is initially placed in the reactor. The reactor is well mixed
(a) If the reaction is first order:
-]'a = kCA with k = 0.865 min-I
calculate the time necessary to reduce the number of moles of A in the
reactor to 0.2 mol. (Note: NA = CAY) (Ans.: t = 5.3 min)
(b) If the reaction is second order.
2 dm3
-rA = kCi with k = --
mol . min
calcuKate the time necessary to consume 19.0 mol of A.
(c) If the temperature is 127"C, what is the initial total pressure? What IS the
final total pressure assuming the reaction goes to completion?
P1-13, (a) How many cubic feet (at STP) enter the packed-bed reactor descnbedl in
Example 1-5 every second? How lon'g does a molecule spend, on the
average, in the reactor? [Hint: What is the gas velocity in each tube
assuming a 30% porosity (volume of gasIvolume of reactor) for the
packed bed?]
(b) Estimate the time that a catalyst particle and a gas-phase molecule spend
in the Sasol straight-through transport reactor (STTR). What is the bulk
density of the catalyst (kg cat/m3) in the STTR?
P1-14, Write a one-paragraph summary of a journal article on Ghemical kinetics or
reaction engineering. The article must have been published within the last five
years4 What did you learn from this article? Why is the article important?
P1-15, (a) What journals, books, or papers give you costs of industrial (not labora-
tory, e.g., Fisher catalog) chemicals and catalysts?
([b) List various journals, books, or other sources where you will find details
about the construction and safety of industrial reactors.

See the Supplementary Reading list at the end of the chapter, particularly item 4.