Assignment 1 Q

CHBE 457 Process Synthesis Department of Chemical and Biological Engineering The University of British Columbia Assignment 1

Due: Friday, 26 September 2014, 4:30pm CHBE Main Office

1. Nitrobenze Nitrobenzene ne (a precursor precursor for aniline) is made by nitration nitration of benzene in the presence of sulfuric sulfuric acid: + HNO3

[H2SO4]

NO2 + H2O

(R1)

US Patent 4,772,757 describes a process with recycle of nitrating acid. (a) Search the literature literature and prepare a qualitative qualitative flowsheet flowsheet for the nitrobenze nitrobenzene ne plant. Explain Explain the plant operation. (b) Create a preliminary database, with the following following parameters for all major components: Density, sity, Normal Boiling Point, Heat Capacity, Capacity, Heat Conductivity, and Critical properties. List your sources (Perry’s Chemical Engineers’ Handbook, process simulators, the Internet, etc.). (c) Show an input-output diagram for this process with with capacity of 100 000 (tonnes/yr). (d) What is the maximum maximum gross profit profit attainable? attainable? Source of prices of commodity chemicals: a weekly publication ICIS Chemical Business at http://www.icis.com/StaticPages/Students.htm

(Reported prices are mostly from 2006.) Reports (~6 months old) available at http://www.icispricing.com/il_shared/il_splash/chemicals.asp?llink%

2. Consider the flowsheet flowsheet for the manufacture of vinyl vinyl chloride in Figure 4.8 of our textbook: textbook:

Figure 1: Flowsheet showing task integration for the vinylchloride process

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(a) If the pyrolysis furnace and the distillation towers are operated at the same pressure as the chlorination reactor (1.5 atm), what are the principal disadvantages? Hint: Check the boiling points and critical constants for the major chemicals, Table 1. (b) Is it possible to use some of the heat of condensation from the C 2 H4 Cl2  condenser to drive the reboiler of the first distillation column? Explain your response. (c) Consider the first reaction to make dichloroethane. Show the distribution of chemicals when ethylene is 25% in excess of the stoichiometric amount and the chlorine is entirely converted. Assume that 100 000 lb/hr of vinyl chloride are produced.

Table 1: Boiling points and critical constants Normal Boiling Point Boiling point ( C) at 1 atm ( C) 4.8 atm 12 atm 26 atm 0 −84.8 −51.7 −26.2 33.1 70.5 110 −13.8 83.7 146 193 242 ◦

Chemical HCl C2 H3 Cl C2 H4 Cl2

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Critical constants T c ( C) Pc  (atm) 51.4 82.1 159 56 250 50 ◦

3. It is desired to produce a hot vapour stream of benzene to feed a reactor for a certain petrochemical process. The benzene is available from an off-site storage facility at 1 atm and 25 C. The reactor requires the benzene to be at 250 C and 10 atm. Two possible process schemes are being considered to heat and pressurize the feed: (1) pump the liquid benzene to 10 atm and then heat it up/vapourize in a heat exchanger, or (2) vapourize the benzene first and then compress it to the desired pressure. Use a process simulator to compare the cost of the two proposed schemes to feed 1000 kg/h of benzene to the reactor. Assume that the cost of heating is $15/GJ and that the electricity cost (to power the pump or the compressor) is $0.10/kWh. ◦

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4. The production of ammonia using the Haber process takes place at temperatures of around 500 C and pressures of 250 atm using a porous iron catalyst according to the following highly exothermic reaction: ◦

N2 (g) + 3 H2 (g)  2 NH3 (g) (a) Give possible reasons for the high temperature and pressure used for this reaction. (b) Use a process simulator to determine the equilibrium conversion obtained in the reactor for the given conditions. The feed is a mixture of N 2  and H2  in stoichiometric proportion. (c) Explain how the temperature and pressure should be adjusted to increase the conversion and the penalties for making these changes. Support your explanations with the simulation results.

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