Page 107 - Plant design and economics for chemical engineers

GENERAL DESIGN CONSIDERATIONS 83

selection. Costs for much of the equipment considered in this section are given
in Chap. 14 (Materials Transfer, Handling, and Treatment Equipment).

NOXIOUS GAS REMOVAL. Gaseous pollutants can be removed from air streams
either by absorption, adsorption, condensation, or incineration. A list of typical
gaseous pollutants that can be treated with these four methods is given in Table
9. Generally, condensation is not utilized as a method for removing a solvent
vapor from air or other carrier gas unless the concentration of the solvent in the
gas is high and the solvent is worth recovery. Since condensation cannot remove
all of the solvent, it can only be used to reduce the solvent concentration in the
carrier gas.

TABLE 9
‘ljpical gaseous pollutants and their sources
Key
element Pollutant Source

so2 Boiler, flue gas
so3 Sulfuric acid manufacture
HzS Natural gas processing, sewage treat-
ment, paper and pulp industry
R-SH (mercaptans) Petroleum refining, pulp and paper
NO, NO, Nitric acid manufacturing, high-
temperature oxidation processes,
nitration processes
Ammonia manufacturing
NH3
Other basic N compounds, pyridines, Sewage, rendering, pyridine base,
amines solvent processes
Halogen:
F H F Phosphate fertilizer, aluminum
SiF, Ceramics, fertilizers
CFC Cleaning operations, refri-
geration and air conditioning
systems, insulation foams
Cl HCI HCI mfg., PVC combustion, organic
chlorination processes
a2 Chlorine manufacturing
c Inorganic
c o Incomplete combustion processes
co2 Combustion processes (not generally
considered a pollutant)
Organic
Hydrocarbons-paraffins, ohfins, Solvent operations, gasoline, petro-
and aromatics chemical operations, solvents
Oxygenated hydrocarbons-aldehydes Partial oxidation processes, surface
ketones, alcohols, phenols, and coating operations, petroleum
oxides processing, plastics, ethylene oxide
Chlorinated solvents Dry-cleaning, degreasing operations