Apparatus for producing polycrystalline silicon

An apparatus for producing polycrystalline silicon in which raw gas including silicon compounds is introduced into a reactor, in which electric current is supplied to silicon seed rods in the reactor so as to heat the silicon seed rods, and in which polycrystalline silicon is deposited on surfaces of the silicon seed rods and grown to rods, the apparatus comprising:

• a bell jar having a circumferential wall forming a chamber of the reactor and a jacket covering the circumferential wall, and in which a cooling path formed between the circumferential wall and the jacket that allows a cooling medium including water to flow therethrough;
• a coolant feeding system which is connected to the bell jar so as to feed the cooling medium to the cooling path;
• a coolant recovering system which is connected to the bell jar so as to recover the cooling medium from the cooling path;
• a pressure control part controlling a pressure in the cooling path;
• and
• a flow-rate control part controlling a flow rate of the cooling medium
• wherein by maintaining the pressure in the cooling path to a prescribed high pressure and introducing the cooling medium into the cooling path in a state of liquid of nearly saturated temperature, the cooling medium flows as a boiling two-phase flow having a heat transfer coefficient larger than that of a single-phase flow of water, so that the circumferential wall is cooled by the boiling two-phase flow of the cooling medium,
• wherein the circumferential wall is made of carbon steel having thermal conductivity of 35 W/(m·K) or more,
• wherein the coolant feeding system is connected to a plurality of coolant inlets that are provided on a lower part of the jacket with intervals along a circumferential direction so as to introduce the cooling medium to the cooling path, and connected to a plurality of upper coolant inlets that are provided on an upper part of the jacket with intervals along the circumferential direction so as to introduce the cooling medium to the cooling path, and
• wherein the coolant recovering system is connected to a coolant outlet that is provided on an upper part of the jacket so as to discharge the cooling medium from the cooling path.