Oxidation heat treatment oven and method for manufacturing oxidized fiber bundle and carbon fiber bundle

An oxidation heat treatment oven comprising:

• a heat treatment chamber configured to heat-treat a fiber bundle that is an aligned acrylic fiber bundle in an oxidizing atmosphere to form an oxidized fiber bundle;
• a slit-shaped opening configured to take the fiber bundle in and out of the heat treatment chamber;
• guide rollers installed at both ends of the heat treatment chamber and configured to turn the fiber bundle back;
• a hot air supply nozzle that has a longitudinal axis along a width of the fiber bundle and that blows out hot air, in a direction substantially parallel to a traveling direction of the fiber bundle, above and/or below the fiber bundle traveling in the heat treatment chamber;
• and
• a suction nozzle configured to suck the hot air blown out from the hot air supply nozzle,
• wherein the hot air supply nozzle satisfies conditions (1) to (3) described below:
• (1) The hot air supply nozzle comprises a hot air introduction port configured to supply hot air along the longitudinal axis of the hot air supply nozzle;
• a hot air supply port configured to blow out the hot air in the direction substantially parallel to the traveling direction of the fiber bundle;
• and one or more stabilization chambers located between the hot air introduction port and the hot air supply port, wherein the hot air introduction port and the hot air supply port communicate with each other via the one or more stabilization chambers;
• (2) At least one of the stabilization chambers comprises a partition plate provided on a downstream side of a hot air flow path;
• a plurality of cylindrical bodies each having openings at both ends and connected to a surface of the partition plate on an upstream side of the hot air flow path such that an axis orientation of each of the cylindrical bodies is perpendicular to the longitudinal axis of the hot air supply nozzle;
• and a gas flow hole provided at a surface of the each of the cylindrical bodies in contact with the partition plate and configured to penetrate through the partition plate;
• and
• (3) In the cylindrical bodies, an angle θ formed by the partition plate and a wall that is one of walls rising from the partition plate and on a side close to the hot air introduction port is in a range of 60° or more and 110° or less as an internal angle in a cross-sectional shape of the cylindrical bodies.