System and method for fluidized bed reduction of powdered iron ore

A system for reducing powdery iron ore on a fluidized bed, comprising:

• a bin, a screw feeder, a bubbling fluidized bed, a primary feeder, a primary circulating fluidized bed, a secondary feeder, a secondary circulating fluidized bed, a tertiary feeder, a tertiary circulating fluidized bed, a discharger, a product bin, a pipeline burner, a primary coal gas preheater, a secondary coal gas preheater, and a tertiary coal gas preheater;
• wherein the bubbling fluidized bed comprises a fluidized bed body, a first cyclone separator, a second cyclone separator, a third cyclone separator and a feeder;
• the primary circulating fluidized bed comprises a primary riser, a fourth cyclone separator, a fifth cyclone separator and a primary circulating dipleg;
• the secondary circulating fluidized bed comprises a secondary riser, a sixth cyclone separator, a seventh cyclone separator and a secondary circulating dipleg;
• the tertiary circulating fluidized bed comprises a tertiary riser, an eighth cyclone separator, a ninth cyclone separator and a tertiary circulating dipleg;
• a feed outlet of the bin is connected to a feed inlet of the screw feeder, and a feed outlet of the screw feeder is connected to a gas outlet of the first cyclone separator and an inlet of the second cyclone separator, respectively, through a pipeline;
• an inlet of the first cyclone separator is connected to a feed outlet of the second cyclone separator, a feed outlet of the third cyclone separator and a gas outlet of the fluidized bed body, respectively, through a pipeline, a feed outlet of the first cyclone separator is connected to a feed inlet of the feeder, and a gas outlet of the first cyclone separator is connected to an inlet of the second cyclone separator;
• a gas outlet of the second cyclone separator is connected to an inlet of the third cyclone separator, and a gas outlet of the third cyclone separator is connected to a reduction exhaust gas treatment system;
• a gas inlet of the feeder is connected to a coal gas main pipe, and a feed outlet of the feeder is connected to a feed inlet of the fluidized bed body through a pipeline;
• a feed outlet of the fluidized bed body is connected to a feed inlet of the primary feeder through a pipeline, a gas inlet of the fluidized bed body is connected to a gas outlet of the fifth cyclone separator through a pipeline which is provided with the pipeline burner, wherein the pipeline burner is provided with a nozzle which is connected to an air main pipe, and is configured such that part of coal gas is burned in the pipeline burner by passing air for increasing the temperature of the coal gas, so as to provide heat for pre-reduction in the fluidized bed body;
• a gas inlet of the primary feeder is connected to the coal gas main pipe, and a feed outlet of the primary feeder is connected to a feed inlet of the primary riser through a pipeline;
• a gas outlet of the primary riser is connected to an inlet of the fourth cyclone separator, a gas inlet of the primary riser is connected to a coal gas outlet of the primary coal gas preheater through a pipeline, and a circulating return port of the primary riser is connected to a return port of the primary circulating dipleg;
• a gas outlet of the fourth cyclone separator is connected to an inlet of the fifth cyclone separator, and a discharge port of the fourth cyclone separator is connected to the primary circulating dipleg;
• a discharge port of the primary circulating dipleg is connected to a lower feed inlet of the secondary riser, and a gas inlet of the primary circulating dipleg is connected to the coal gas main pipe;
• a gas outlet of the fifth cyclone separator is connected to a gas inlet of the fluidized bed body through a pipeline, and a discharge port of the fifth cyclone separator is connected to a feed inlet of the secondary feeder through a pipeline;
• a gas inlet of the secondary feeder is connected to the coal gas main pipe, and a feed outlet of the secondary feeder is connected to an upper feed inlet of the secondary riser through a pipeline;
• a gas outlet of the secondary riser is connected to an inlet of the sixth cyclone separator, a gas inlet of the secondary riser is connected to a coal gas outlet of the secondary coal gas preheater through a pipeline, and a circulating return port of the secondary riser is connected to a return port of the secondary circulating dipleg;
• a gas outlet of the sixth cyclone separator is connected to an inlet of the seventh cyclone separator, and a discharge port of the sixth cyclone separator is connected to the secondary circulating dipleg;
• a discharge port of the secondary circulating dipleg is connected to a lower feed inlet of the tertiary riser, and a gas inlet of the secondary circulating dipleg is connected to the coal gas main pipe;
• a gas outlet of the seventh cyclone separator is connected to an inlet of the reduction exhaust gas treatment system, and a discharge port of the seventh cyclone separator is connected to a feed inlet of the tertiary feeder through a pipeline;
• a gas inlet of the tertiary feeder is connected to the coal gas main pipe, and a feed outlet of the tertiary feeder is connected to an upper feed inlet of the tertiary riser through a pipeline;
• a gas outlet of the tertiary riser is connected to an inlet of the eighth cyclone separator, a gas inlet of the tertiary riser is connected to a coal gas outlet of the tertiary coal gas preheater through a pipeline, and a circulating return port of the tertiary riser is connected to a return port of the tertiary circulating dipleg;
• a gas outlet of the eighth cyclone separator is connected to an inlet of the ninth cyclone separator, and a discharge port of the eighth cyclone separator is connected to the tertiary circulating dipleg;
• a discharge port of the tertiary circulating dipleg is connected to the product bin through a pipeline, and a gas inlet of the tertiary circulating dipleg is connected to the coal gas main pipe;
• a gas outlet of the ninth cyclone separator is connected to the inlet of the reduction exhaust gas treatment system, and a discharge port of the ninth cyclone separator is connected to a feed inlet of the discharger through a pipeline;
• a gas inlet of the discharger is connected to the coal gas main pipe, and a feed outlet of the discharger is connected to the product bin through a pipeline;
• a nozzle of any one of the primary coal gas preheater, the secondary coal gas preheater and the tertiary coal gas preheater is connected to the air main pipe and the coal gas main pipe through a pipeline, a high temperature flue gas is generated by burning the coal gas for preheating a reducing coal gas, a flue gas outlet of any one of the coal gas preheaters is connected to a flue gas main pipe, and a discharged flue gas enters into a flue gas treatment system via the flue gas main pipe for heat recovery, a coal gas inlet of any one of the coal gas preheaters is connected to the coal gas main pipe, and the coal gas outlet of any one of the coal gas preheaters is connected to the gas inlets at the bottom of the primary riser, the secondary riser and the tertiary riser, respectively.