Method and apparatus for producing direct reduced iron utilizing a source of reducing gas comprising hydrogen and carbon monoxide

Patent metadata

Field	Value
Publication number	US-9328395-B2
Application number	US-201113824648-A
Country	US
Kind code	B2
Filing date	Sep 28, 2011
Priority date	Sep 29, 2010
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

The present invention concerns a method and an apparatus for producing DRI (Direct Reduced Iron) utilizing a high-oxidation reducing gas containing carbon monoxide and hydrogen, derived directly or indirectly from the gasification of hydrocarbons or coal, with a high content of oxidants (H 2 O and CO 2 ). The invention provides a more efficient method and plant comprising a reactor in which particulate material of iron ore comes into contact with a high temperature reducing gas to produce DRI, with lower investment and operating costs, avoiding the need for a fired heater for the reducing gas fed into the reduction reactor. The reducing gas is heated to a temperature above 700° C. in two steps, a first step at a temperature below about 400° C. to prevent the phenomenon of metal dusting, by exchange of sensible heat supplied by the stream of hot spent gas removed from the reduction reactor; and a second step by means of partial or total combustion with oxygen, maintaining the temperature of the combustion gas below the limits established by the construction materials of the combustion chamber.

First claim

The invention claimed is:

1. A method for producing DRI (Direct Reduced Iron) utilizing a source of make-up reducing gas containing carbon monoxide and hydrogen in a reduction plant comprising a reduction reactor having an upper reduction zone where iron-oxides are reduced and transformed to DRI containing metallic iron by a high-temperature reducing gas, mainly composed of hydrogen and carbon monoxide, and a lower discharge zone, said method comprising:
withdrawing a stream of hot spent reducing gas from said reduction zone of the reduction reactor, at a temperature between 300° C. and 600° C.;
passing said stream of hot spent reducing gas through a heat exchanger where its temperature is reduced to a level from 200° C. to 400° C. and then through a cooling station where its temperature is lowered to a level below 100° C. resulting in a cold spent recycle gas stream;
mixing said make-up reducing gas stream with at least a portion of said cold spent reducing gas stream, to produce a mixed gas stream;
passing said mixed gas stream through a CO 2 separation unit whereby a CO 2 lean gas stream and a CO 2 laden gas stream are formed;
passing said CO 2 lean gas stream through said heat exchanger wherein heat is recovered from said hot spent reducing gas withdrawn from the reduction reactor and is used to raise the temperature of said CO 2 lean gas stream to a level lower than 450° C. in a first heating stage without any fuel combustion, to form a heated CO 2 lean gas stream;
splitting the heated CO 2 lean gas stream in at least two portions; raising the temperature of a first portion of said heated CO 2 lean gas stream to above 700° C. by partial combustion in a combustion chamber with a stream of a molecular-oxygen-containing gas, or by total combustion of the first portion of said heated CO 2 lean gas stream, wherein the combustion produces combustion products, and combining the combustion products with a second portion of said heated CO 2 lean gas stream to form a hot reducing gas stream;
feeding said hot reducing gas stream after said combustion to the reduction zone of said reactor; and
discharging DRI from a lower part of the reduction reactor.

2. The method for producing DRI according to claim 1 , in which the ratio of reducing agents to oxidant agents in the reducing gas stream fed to said reduction reactor, defined as (H2+CO)/(H 2 +CO 2 ) in percent volume is at least 7.

3. The method for producing DRI according to claim 1 , in which the reducing index in the reducing gas stream fed to said reduction reactor, defined as (H2+CO)/(H2+CO +H 2 +CO 2 ) in percent volume is at least 0.87.

4. The method for producing DRI according to claim 1 , in which said reduction reactor is a moving bed reactor.

5. The method for producing DRI according to claim 1 , in which said CO 2 separation unit is a pressure swing adsorption (PSA) or a vacuum pressure swing adsorption (VPSA) unit.

6. The method for producing DRI according to claim 5 , wherein said molecular-oxygen-containing gas is oxygen of industrial purity.

7. The method for producing DRI according to claim 5 , wherein said molecular-oxygen-containing gas is oxygen-enriched air.

8. The method for producing DRI according to claim 5 , wherein the portion of the CO 2 lean gas fed to the combustion chamber is between 50% and 70% by volume of the total CO 2 lean gas stream.

9. The method for producing DRI according to claim 1 , in which said CO 2 separation unit is a chemical absorption unit.

10. The method for producing DRI according to claim 1 , wherein the flow rates of the CO 2 lean gas and of the molecular-oxygen-containing gas are controlled in such a manner that the partial or total combustion in said combustion chamber is carried out without any significant formation of soot.

11. The method for producing DRI according to claim 1 , where said DRI is cooled inside the lower discharge zone of the reactor by circulating a cooling gas that is recycled in a closed cooling circuit.

12. The method for producing DRI according to claim 11 , further comprising feeding, to said closed cooling circuit, a non-oxidant cooling gas containing hydrocarbons for increasing the carbon content of said DRI.

13. The method for producing DRI according to claim 12 , wherein said non-oxidant cooling gas containing hydrocarbons is fed directly to the lower discharge zone of said reduction reactor.

14. The method for producing DRI according to claim 11 , wherein said cooling gas is Coke Oven Gas.

15. An apparatus for producing DRI (Direct Reduced Iron) utilizing as a reducing gas sourc; a gas stream containing carbon monoxide and hydrogen in a reduction plant comprising:
a reduction reactor having a reduction zone, where iron-oxides are reduced and transformed to DRI containing metallic iron by a high-temperature reducing gas mainly composed of hydrogen and carbon monoxide, and a discharge zone, said reduction zone having a gas inlet and a gas outlet, the apparatus further including a gas-gas heat exchanger for preheating reducing gas without any combustion by exploiting heat provided from hot spent gas effluent from said reduction reactor and for cooling said hot spent gas effluent from said reduction reactor;
a gas compressor;
a CO 2 separation unit; and
a combustion chamber having a combustion zone and a mixing zone;
a first conduit connecting the gas outlet of said reduction zone of the reduction reactor with the heat exchanger; a second conduit connecting the outlet of said heat exchanger for cooling said hot spent gas effluent from said reduction reactor;
a third conduit connecting the heat exchanger for cooling said hot spent gas effluent from said reduction reactor with the compressor;
a fourth conduit connecting the compressor with said CO 2 separation unit;
a fifth conduit connecting the CO 2 separation unit with said heat exchanger;
a sixth conduit directly connecting said heat exchanger with the combustion chamber without any gas heating between said heat exchanger and said combustion chamber;
a seventh conduit connecting the combustion chamber with said gas inlet of the reduction zone;
a tenth conduit for introducing oxygen or a molecular-oxygen-containing gas into said combustion chamber and control for controlling the amount of molecular-oxygen-containing gas in response to the desired temperature of the gas stream at the gas inlet of said reduction zone, the apparatus further comprising control for controlling an amount of reducing gas by-passing said combustion chamber, wherein said gas is combined with a hot gas that flows from said combustion chamber.

16. The apparatus for producing DRI according to claim 15 , further comprising an eighth conduit for introducing and directing a hydrocarbon-containing cooling gas to a lower discharge zone of the reduction reactor.

17. The apparatus for producing DRI according to claim 15 , further comprising a ninth conduit for introducing and directing coke oven gas to a lower discharge zone of the reduction reactor.

18. The apparatus for producing DRI according to claim 15 , wherein said reduction reactor is adapted for selectively operating a cooling gas circulation system for cooling said DRI allowing for optionally discharging hot or cold DRI.

Assignees

• Martinis Alessandro
• Condosta Michele
• ZENDEJAS MARTÍNEZ Eugenio
• Duarte Escareño Pablo Enrique
• Danieli Off Mecc
• Hyl Technologies Sa De Cv

Inventors

• Martinis Alessandro
• Condosta Michele
• ZENDEJAS MARTÍNEZ Eugenio
• Duarte Escareño Pablo Enrique

Classifications

• Y02P10/265

  Cross-Sectional Technologies · mapped topic

• Y02P10/283

  Cross-Sectional Technologies · mapped topic

• B01D53/1475

  Removing carbon dioxide · CPC title

• Y02P10/136

  Cross-Sectional Technologies · mapped topic

• Y02P10/128

  Cross-Sectional Technologies · mapped topic