Vertical pyrolysis furnace for use in the production of carbon fibers

Abstract

A vertical pyrolysis furnace used in the carbonization or high temperature heat treatment of a continuous length of organic fibrous material is disclosed. The oven includes a central conduit or passage having a plurality of independently controlled heating zones disposed circumferentially therearound and spaced axially therealong. The conduit and heating elements are surrounded by suitable insulating material and a gas-tight shell. At the top of the furnace an exhaust manifold is provided which communicates with the central conduit. An environmental seal is provided at the upper end of the exhaust manifold and at the bottom of the conduit. Suitable gaseous inlets communicate with the furnace for an inert gaseous atmosphere which is controlled such that free convection causes the gaseous atmosphere to rise vertically through the central conduit to the exhaust chamber located at the upper end thereof. A continuous length of organic fibrous material moves vertically downwardly through the central conduit from the upper environmental seal to the lower environmental seal. The independently controlled heating zones provide a vertically downwardly increasing temperature gradient, up to a desired maximum value which extends over a prescribed length, which drives off toxic gaseous by-products from the continuous length of organic fibrous material. The heating zone placement and lower environmental seal permit the continuous length of organic fibrous material to cool substantially before exiting to the atmosphere.