課程名稱︰質能平衡甲
課程性質︰系定必修
課程教師︰蔡偉博
開課系所︰化學工程學系
考試時間︰2006/04/06 晚上
試題 :
(total points:110)
1.(20 points) The rate at which a substance passes through a semi-permeable
membrane is determined by the diffusivity D(cm^2/s) of the gas. D varies with
the membrane temperture T(K) according to the Arrhenius equation:
D = D0 exp(-E/RT)
Where D0 = the pre-exponential factor
E = the activation energy for diffusion
R = 1.987cal/(mol˙K)
Diffusivities of SO2 in a fluorosilicone rubber tube are measured at several
tempertures, with the following results:
T(K) D(cm^2/s)*10^6
______________________________________________________________
347.0 1.34<=(so that D = 1.34*10^-6 cm^2/s)
374.2 2.50
396.2 4.55
420.7 8.52
447.7 14.07
471.2 19.99
(a) What are the units of D0 and E?(5 points)
(b) How should the data be plotted to obtain a straight line on rectangular
coordinates?(5 points)
(c) Plot the data in the manner indicated in part(b), and determine D0 and E
from the resulting line.(10 points)
2.(10 points) A fluid of unknown density is used in two manometers─one seal-
end, the other across an orifice in a water pipeline. The readings shown here
are obtained on a day when barometric pressure in 756 mm-Hg. What is the
pressure drop (mm-Hg) from point(a) to point(b)?
3.(10 points) A plot of F versus t yields a line that passes through the points
(t1=15,F1=0.298) and (t2=30,F2=0.0527) on (1) a semi-log plot and (2) a log
plot. For each case, calculate the equation that relates F and t.
4.(30 points) Methanol is synthesized from carbon monoxide and hydrogen in a
catalytic reactor. The fresh feed to the process contains 32.0 mol% CO, 64% H2,
and 4.0% N2. This stream is mixed with a recycle stream in a ratio 5 mol
recycle/1 mol fresh feed to produce the feed to the reactor, which contains
13.0 mol% N2. A low single-pass conversion is attained in the reactor. The
reactor effluent goes to a condenser from two streams emerge: a liquid product
stream containing essentially all the methanol formed in the reactor, and a gas
stream containing all the CO, H2 and N2 leaving the reactor. The gas stream is
split into two fractions: one is removed from the process as a purge stream,
and the other is the recycle stream that combines with the fresh feed to the
reactor.
(a) For a basis of 100 mol fresh feed/h, calculate the production rate of
methanol (mol/h), the molar flow rate and composition of the purge gas, and the
overall and the single-pass conversions.(22 points)
(b) Briefy explain in your own words the reasons for including (i) the recycle
stream and (ii) the purge stream in the process design.(8 points)
5.(15 points) Three hundred gallons of a mixture containing 75 wt% ethanol
(ethyl alcohol) and 25 wt% water (mixture specific gravity = 0.877) and a
quantity of a 40 wt% ethanol─60 wt% water (SG = 0.952) and blended to produce
a mixture containing 60 wt% ethanol. The object of this problem is to determine
V40, the require volume of the 40% mixture.
(a) Draw and label a flowchart of the mixing process and do the degree-of-
freedom analysis.
(b) Calculate V40.
6.(25 points) A hydrocarbon gas is burned with air. The dry-basis product gas
composition is 1.5 mol% CO, 6.0% CO2, 8.2% O2, and 84.3% N2. There is no atomic
oxygen in the fuel. Calculate the ratio of hydrogen to carbon in the fuel gas
and speculate on what the fuel might be. Then calculate the present excess air
fed to the reactor.
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 140.112.240.230
※ 編輯: amnotu 來自: 140.112.240.230 (06/22 21:26)