Page 62 - Plant design and economics for chemical engineers

PROCESS DESIGN DEVELOPMENT 45

13. Synthesis gas may be prepared by a continuous, noncatalytic conversion of any
hydrocarbon by means of controlled partial combustion in a fire-brick lined reactor.
In the basic form of this process, the hydrocarbon and oxidant (oxygen or air) are
separately preheated and charged to the reactor. Before entering the reaction zone,
the two feed stocks are intimately mixed in a combustion chamber. The heat
produced by combustion of part. of the hydrocarbon pyrolyzes the remaining hydro-
carbons into gas and a small amount of carbon in the reaction zone. The reactor
effluent then passes through a waste-heat boiler, a water-wash carbon-removal unit,
and a water cooler-scrubber. Carbon is recovered in equipment of simple design in a
form which can be used as fuel or in ordinary carbon products.
Prepare a simplified equipment flow sheet for the process, with temperatures
and pressure conditions at each piece of equipment.
14. Make a material balance and a qualitative flow sheet for the synthesis gas process
described in Prob. 13. Assume an operating factor of 95 percent and a feed stock
with an analysis of 84.6 percent C, 11.3 percent Hz, 3.5 percent S, 0.13 percent O,,
0.4 percent N,, and 0.07 percent ash (all on a weight basis). The oxidant in this
process will be oxygen having a purity of 95 percent. Production is to be 8.2 m3/s.
15. Prepare an energy balance and a suitable flow sheet for the synthesis gas production
requested in Prob. 14.
16. Size the equipment that is necessary for the synthesis gas production outlined in
Probs. 13 and 14.
17. Estimate the required utilities for the synthesis gas plant described in the previous
four problems.
18. Repeat the calculations of Probs. 14 to 17 by substituting air as the oxidant in place
of the 95 percent purity oxygen.
19. In the face of world food shortages accompanying an exploding world population,
many engineers have suggested that the world look to crude oil as a new source of
food. Explore this possibility and prepare a flow sheet which utilizes the conversion
of petroleum to food by organic microorganisms. What are the problems that must
be overcome to make this possibility an economic reality?
20. A chemical engineering consultant for a large refinery complex has been asked to
investigate the feasibility of manufacturing 1.44 x lo-* kg/s of thiophane, an
odorant made from a combination of tetrahydrofuran (THF) and hydragen sulfide.
The essential reaction is given below: .

CH,-CH, CH,-CH,
I 1 +H,Sc-= I I + H,O
“9 5H2 “HI 732
0 S
\
The process consists essentially of the following steps:
(al THF is vaporized and mixed with H,S in a ratio of 1.5 moles H,S to one mole of
THF and reacted over an alumina catalyst at an average temperature of 672 K
and 207 kPa.
(b) Reactor vapors are cooled to 300 K and phase separated.
(cl The noncondensable gases are removed and burned in a fume furnace while the *
crude thiophane is caustic washed in a batch operation.