Environmental Engineering Reference
In-Depth Information
process, the reaction products obtained are removed from the vessel and extraneous by-
products and unreacted inputs removed (USEPA, 2002). This step is identiied as product
separation or puriication. The techniques used involve iltration, distillation, and extrac-
tion either singly or in combination. The continuous reactions method, as the procedure
implies, is a continuous reaction process technique and is suited more for greater produc-
tion of reaction products, in comparison to the batch reaction method, which is used for
production of smaller quantities of reaction products. As in the case of the batch method,
the reaction products of the continuous reaction technique require product separation.
The feedstock obtained includes alkanes, benzene, butane, butadiene, butylenes, ethane,
ethylene, methane, propane, propylene, toluene, and xylene. The feedstock organic chemi-
cals are both end-use products and also intermediate chemicals, i.e., they serve as feedstock
for production (generally by conversion processes) into other end-use organic chemicals
or products. Typical end-use products include the various pesticides and fertilizers used
in agriculture, the various forms and types of plastics, textiles, solvents, detergents, phar-
maceuticals, appliances, synthetic lubricants, nylon, plumbing, and even chewing gum. By
and large, the various kinds of plastics are perhaps the largest and most important product
group emanating from petrochemical industries.
4.6.2 Chemical Industries
By deinition, inorganic chemical industries manufacture chemicals that do not contain
the carbon molecule. To a large extent, the feedstock or raw materials for the inorganic
chemicals are mineral in origin and the products manufactured are acids, alkalis, salts,
and chemicals that are used as aids in producing other products, especially fertilizers.
Ammonium nitrate (NH
4
NO
3
), ammonium sulfate ([NH
4
]
2
SO
4
), urea (CO[NH
2
]
2
), and
superphosphates are some of the fertilizers manufactured. The processes involved for
production or manufacture of the fertilizers, for example, vary depending on the type of
fertilizer. Neutralization of nitric acid (HNO
3
) with ammonia (NH
3
) will yield ammonium
nitrate (NH
4
NO
3
) through the simple reaction
NH
3
+ HNO
3
→ NH
4
NO
3
Meanwhile, there are at least three different ways or sources to obtain ammonium sul-
fate (USEPA, 1979). These include (a) combining anhydrous ammonia and sulfuric acid in a
reactor to obtain synthetic ammonium sulfate, (b) as a by-product from production of cap-
rolac t a m [(CH
2
)
5
COHN], and (c) as a coke oven by-product obtained by reacting ammonia
from coke oven offgas with sulfuric acid.
The acids produced are to a large extent mainly utilized as intermediates in indus-
trial and manufacturing activities. The fertilizer industry is a big beneiciary. Nitric acid
(HNO
3
) and sulfuric acid (H
2
SO
4
) contribute signiicantly to the production of ammonium
nitrate and phosphate, respectively. Hydrochloric acid (HCl) is used in steel pickling, etch-
ing and metal cleaning, and hydrometallurgical production.
Perhaps one of the largest groupings of inorganic chemical industries is the chlorine-alkali
group. This group produces chlorine, sodium hydroxide, sodium carbonate and bicarbonate,
and potassium hydroxide. Their products are greatly utilized as intermediates in the organic
chemical manufacturing industries (USEPA, 1995) ranging from (a) vinyl chloride monomer,
ethylene dichloride, glycols, chlorinated solvents, and methanes for chlorine and (b) pro-
pylene oxide, polycarbonate resin, epoxies, synthetic ibers, soaps, detergents, and rayon for
caustic soda. The raw or source material for the industry is both natural salt deposits and
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