GRAPHITE HEATING FURNACE

Abstract

A gas supplying unit supplies a nitrogen gas into a furnace body of a graphite heating furnace in which at least a part of the furnace body is formed with a graphite. An exhausting unit exhausts a gas inside the furnace body to outside the furnace body. A dew-point temperature of the nitrogen gas supplied into the furnace body is equal to or lower than −80° C. A pressure inside the furnace body is equal to or higher than 140 Pa with respect to an atmospheric pressure outside the furnace body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for explaining a structure of a graphite heating furnace according to a first embodiment of the present invention;

FIG. 2 is a graph for explaining a relation between a furnace body pressure of the graphite heating furnace and an HCN concentration inside the furnace body;

FIG. 3 is a graph for explaining a relation between a dew-point temperature of a nitrogen gas supplied into the graphite heating furnace and the HCN concentration inside the furnace body;

FIG. 4 is a schematic diagram for explaining a structure of a graphite heating furnace according to a second embodiment of the present invention;

FIG. 5 is a schematic diagram for explaining a structure of a graphite heating furnace according to a third embodiment of the present invention;

FIG. 6 is a schematic diagram for explaining a structure of a graphite heating furnace according to a fourth embodiment of the present invention;

FIG. 7 is a schematic diagram for explaining a structure of a graphite heating furnace according to a fifth embodiment of the present invention; and

FIG. 8 is a schematic diagram for explaining a structure of a graphite heating furnace according to a sixth embodiment of the present invention.

Claims

1. A graphite heating furnace of which at least a part of a furnace body is formed with a graphite, the graphite heating furnace comprising: a gas supplying unit that supplies a nitrogen gas into the furnace body; andan exhausting unit that exhausts a gas inside the furnace body to outside the furnace body, whereina dew-point temperature of the nitrogen gas supplied into the furnace body is equal to or lower than −80 degrees Celsius, anda pressure inside the furnace body is equal to or higher than 140 pascals with respect to an atmospheric pressure outside the furnace body.

2. The graphite heating furnace according to claim 1, wherein the exhausting unit includes a discharging unit that discharges at least a part of the gas inside the furnace body to atmosphere.

3. The graphite heating furnace according to claim 1, further comprising: a pressure detecting unit that detects the pressure inside the furnace body; anda control unit that controls at least one of an amount of supplying the nitrogen gas by the gas supplying unit and an amount exhausting the gas inside the furnace body by the exhausting unit, based detected pressure inside the furnace body.

4. The graphite heating furnace according to claim 1, further comprising: a concentration detecting unit that detects a concentration of a hydrogen-cyanide gas inside the furnace body; anda control unit that controls at least one of an amount of supplying the nitrogen gas by the gas supplying unit and an amount exhausting the gas inside the furnace body by the exhausting unit, based detected concentration of the hydrogen-cyanide gas inside the furnace body.

5. The graphite heating furnace according to claim 1, wherein a temperature inside the furnace body is equal to or lower than 2200 degrees Kelvin.

6. The graphite heating furnace according to claim 1, wherein the graphite heating furnace is one of a dehydration-sintering furnace that dehydrates and sinters an optical fiber porous preform, an elongation-heating furnace that elongates the optical fiber porous preform, and a drawing-heating furnace that draws the optical fiber porous preform.