Page 28 - The engineering of chemical reactions

12 Introduction

We try to make calculations come out in round numbers; so in many problems the feed
concentrations are 2 moles/liter, conversions are 90%, reactor volumes 100 liters, and feed
temperatures 300 or 400 K. We further assume that all heats of reaction and heat capacities
are independent of temperature, pressure, and composition. We sometimes even assume
the ideal gas constant R=2 Cal/mole K, just because it makes it easier to remember than
1.98.. . .
We can then work out many numerical answers without even using a calculator, al-
though several problems distributed throughout the course will be assigned where computer
solutions and graphics are required. Some problems (the most interesting ones) cannot be
worked so simply, and we must resort to numerical solutions. There are computer problems
interspersed throughout the text, and your instructor will tell you exactly what programs
and methods you should use to solve them.

SOURCES

The “game” is thus to make chemicals that can be sold for high prices from inexpensive raw
materials. This involves finding a chemical reactor system that will do this better than the
competition, finding cheap and abundant raw materials, finding a good and reliable market
for the product, and disposing of byproducts.
A working chemical engineer needs continuous information on prices, markets, and
processes on which to base calculations and estimations. A readily accessible source is
Chemical and Engineering News, a weekly magazine published by the American Chemical
Society that contains the latest gossip in chemistry and chemical engineering and some
information about trends. Much more reliable are Chemical Marketing Reporter and
Chemical Weekly. These magazines provide considerable and reliable information on prices
and markets for industrial chemicals. Table l-3 lists the top 50 chemicals in the country
from Chemical and Engineering News and a list of wholesale prices of chemicals in August
1995 taken from a many-page list in Chemical Marketing Reporter. Some of these are listed
in Table l-4.

TABLE l-4
Commodity Chemical prices
Chemical Description Price Price/lb

crude oil $15-26Axurel
sweet light 22hrrel $0.076
heavy sour 1 Ubarrel 0.056
diesel fuel 0.05% s 0.59/gal 0.083
gasoline unleaded regular 0.62&l 0.087
propane fuel 0.38/gal 0.078
methane 2.0/MMBtu 0.046
coal 1.6IMMBtu 0.020
oxygen 0.015
hydrogen
c o
chlorine 200/tori 0.10

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