Page 201 - Chemical and process design handbook

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CARBON

Carbon exists in several forms: lampblack, carbon black, activated carbon,
graphite, and industrial diamonds. The first three types of carbon are
examples of amorphous carbon.
The term carbon black includes furnace black, colloidal black, ther-
mal black, channel black, and acetylene black. Carbon black is mostly
derived from petroleum and involves partial combustion or a combina-
tion of combustion and thermal cracking of hydrocarbons, and to a
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lesser extent natural gas, at 1200 to1400 C.
Lampblack, is soot formed by the incomplete burning of carbonaceous
solids or liquids. It is gradually being replaced in most uses by carbon black
that is the product of incomplete combustion. Activated carbon is amor-
phous carbon that has been treated with steam and heat until it has a very
great affinity for adsorbing many materials. Graphite is a soft, crystalline
modification of carbon that differs greatly in properties from amorphous
carbon and from diamond. Industrial diamonds, both natural and synthetic,
are used for drill points, special tools, glass cutters, wire-drawing dies, dia-
mond saws. and many other applications where this hardest of all sub-
stances is essential.
Lampblack, or soot, is an old product and is manufactured by the
combustion of petroleum or coal-tar by-products in an oxygen-diminished
atmosphere. In the process, the soot is collected in large chambers from
which the raw lampblack is removed, mixed with tar, molded into bricks,
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or pugs, and calcined up to about 1000 C, after which the product is
ground to a fine powder.
The four basic carbon black manufacturing processes are either of the
partial combustion type (the channel, oil furnace, or gas furnace process)
or of the cracking type (the thermal process).
The oil furnace process uses aromatic petroleum oils and residues as feed-
stock and in the oil furnace process (Fig. 1), a highly aromatic feedstock oil
(usually a refinery catalytic cracker residue or coal tar-derived material) is con-
verted to the desired grade of carbon black by partial combustion and pyroly-
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sis at 1400 to 1650 C in a refractory (mainly alumina) -lined steel reactor.

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