Method for controlling a flow rate of gas for prereducing ore and apparatus therefor

A method for controlling a flow rate of gas for prereducing ore, comprising the steps of:

• feeding substantially all of a gas generated in a smelting reduction furnace to a prereduction furnace through a first gas flow passage, said first gas flow passage coupling said smelting reduction furnace to said prereduction furnace;
• prereducing ore in said prereduction furnace having a fluidized bed of ore, with the gas fed to said prereduction furnace through the first gas flow passage;
• exhausting said gas used for prereducing ore from said prereduction furnace through a second gas flow passage;
• smelting and reducing prereduced ore in said smelting reduction furnace;
• controlling an actual flow rate and a pressure of said gas generated in said smelting reduction furnace and fed to said prereduction furnace through said first gas flow passage with a gas pressure control valve positioned in said first gas flow passage, the pressure of said gas fed to said prereduction furnace being controlled on the basis of a pressure value detected by a pressure detector positioned at a gas inlet port positioned in said prereduction furnace;
• and
• controlling said flow rate of said gas exhausted from the prereduction furnace with a gas flow rate control device positioned in the second gas flow passage, said pressure of said gas fed into the preduction furnace through the first gas flow passage and said flow rate of said gas exhausted from the prereduction furnace being controlled with said gas pressure control valve positioned in said first gas flow passage, and said gas flow rate control device being positioned in said second gas flow passage so as to maintain the pressure in the prereduction furnace between a preselected minimum value and a maximum value by controlling the gas flow rates of said gas into and out of said prereduction furnace.

An apparatus for controlling a flow rate of gas for prereducing ore, in a system comprising a smelting reduction furnace coupled to a prereduction furnace having an ore in the form of a fluidized ore bed, the apparatus comprising:

• a first gas flow passage for feeding substantially all of a gas generated in said smelting reduction furnace to said prereduction furnace having the fluidized bed;
• a second gas flow passage for exhausting the gas used for prereducing ore;
• a gas pressure control valve positioned in said first gas flow passage for controlling an actual flow rate and pressure of said gas fed to said prereduction furnace by controlling the pressure of said gas generated in said smelting reduction furnace and fed into said prereduction furnace;
• a gas flow rate control device positioned in said second gas flow passage for controlling said flow rate of said gas exhausted from said prereduction furnace;
• a gas pressure detector for detecting a pressure of said gas at an inlet port positioned in said prereduction furnace, said gas pressure at said inlet port being controlled with said gas pressure control valve positioned in said first gas flow passage;
• a gas flow rate detector positioned in said second gas flow passage for measuring the flow rate of said gas exhausted from said prereduction furnace, said thus measured flow rate of said gas being exhausted from said prereduction furnace being controlled with said gas flow rate control device positioned in said second gas flow passage;
• an arithmetic control unit for processing said detected pressure at said inlet port of said prereduction furnace and a measured flow rate of said gas exhausted from said prereduction furnace, and for transmitting a control command to said gas pressure control valve and to said gas flow rate control device to thereby control the gas flow into and out of said prereduction furnace.