Apparatus for forming carbon fibers

An apparatus for forming carbon fibers by a continuous gas phase process comprising thermal decomposition of a gaseous hydrocarbon compound in the presence of metal nuclei entrained in a gas stream, said apparatus comprising:

• (a) a tubular thermal reactor defining a thermal decomposition chamber having a vertical axis, a closed upper end and a lower outlet,
• (b) a reactant feed tube having an opening adjacent to and spaced from the reactor closed end, said feed tube extending axially upwardly within the reactor and radially spaced therefrom, whereupon said feed tube and said reactor cooperate to define a gas flow path that extends axially upward through the feed tube into the reactor chamber adjacent the reactor closed end and thereafter axially downward through the chamber about the feed tube,
• (c) means for heating the reactor to establish a hot zone within the chamber adjacent the closed end at a temperature sufficient to sustain carbon fiber growth and a relatively cool zone adjacent the reactor outlet, thereby establishing a thermal gradient within the reactor that minimizes convective currents within the reactor chamber and feed tube,
• (d) means for continuously supplying a gaseous reactant stream comprising a metal compound thermally decomposable to produce submicron metal nuclei into the feed tube at a rate sufficient to entrain the nascent metal nuclei within the gas stream for dispersion into the reactor hot zone, said reactor chamber having a cross sectional area substantially greater than the cross sectional area of said feed tube to accommodate said gas stream at a reduced downward flow rate suitable for sustained fiber growth, and
• (e) means for collecting carbon fibers from exhaust gas exiting the reactor outlet.

An apparatus for forming carbon fibers by a continuous gas phase process comprising pyrolytic decomposition of a gaseous hydrocarbon compound in the presence of iron nuclei entrained in a gas stream, said apparatus comprising:

• (a) an axially elongate tubular thermal reactor defining a hydrocarbon pyrolysis chamber having a closed upper end and a lower outlet,
• (b) an axially elongate reactant feed tube having an inlet and an opening adjacent the reactor closed end, said feed tube extending axially upwardly within the reactor at least three-fourths of the axial length of the reactor and radially spaced therefrom, whereupon said feed tube and said reactor cooperate to define a gas flow path extending axially upward through the feed tube into the reactor chamber adjacent the reactor closed end and thereafter extending axially downward through the chamber about the feed tube,
• (c) means for heating the reactor to establish a hot zone within the chamber adjacent the closed end at a temperature sufficient to sustain carbon fiber growth and a relatively cool zone adjacent the reactor outlet, thereby providing a first temperature adjacent said inlet, a second temperature greater than said first temperature within said hot zone and a third temperature less than said second temperature adjacent said outlet to minimize convective currents within the reactor chamber and feed tube,
• (d) means for continuously supplying a gaseous reactant stream comprising an iron compound thermally decomposable to produce submicron iron nuclei into the feed tube at a rate sufficient to entrain the nascent iron nuclei within the gas stream for dispersion into the reactor hot zone, said reactor chamber being generally concentric with said feed tube along the axial extent thereof and having a diameter at least three times greater than said feed tube to accommodate said gas stream at a reduced downward flow rate suitable for sustained fiber growth, and
• (e) means for collecting carbon fibers from exhaust gas exiting the reactor outlet.