EA028730B1 - Method and apparatus for sequestering carbon dioxide from a spent gas - Google Patents

Abstract

A method and apparatus for sequestering carbon dioxide from a waste gas and reusing it as a recycled gas without emissions concerns, including: given a gas source divided into a process gas and a waste gas: mixing the process gas with a hydrocarbon and feeding a resulting feed gas into a reformer for reforming the feed gas and forming a reducing gas; and feeding at least a portion of the waste gas into a carbon dioxide scrubber for removing at least some carbon dioxide from the waste gas and forming a carbon dioxide lean gas that is mixed with the reducing gas. Optionally, the method also includes feeding at least a portion of the waste gas into the carbon dioxide scrubber for removing at least some carbon dioxide from the waste gas and forming a fuel gas after the addition of a hydrocarbon that is fed into the reformer. Optionally, the gas source and the reducing gas are associated with a direct reduction process for converting iron oxide to metallic iron in a reduction furnace that utilizes the reducing gas, optionally after some modification, and produces the gas source.

Description

This patent application / patent is a partial continuation of the simultaneously pending application for US patent No. 12/762618, filed April 19, 2010 and entitled Method and device for sequestration of carbon dioxide from the exhaust gas, claiming the priority of provisional application for US patent No. 61/170999, filed April 20, 2009 and entitled Method and device for sequestration of carbon dioxide from combustible blast furnace gas, the contents of both applications are fully incorporated into this application by reference.

The technical field of the invention

The present invention relates generally to a method and apparatus for the direct reduction of iron oxide to metallic iron, among other processes. In particular, the present invention relates to a method and apparatus for sequestering carbon dioxide from exhaust gas in conjunction with such processes.

BACKGROUND OF THE INVENTION

In many industrial processes, there is a need for an efficient and cost-effective method of removing carbon dioxide from a source of secondary fuel, such as a source of combustible blast furnace gas, in a direct reduction process. In other words, in many industrial processes there is a need for an efficient and cost-effective way of removing carbon dioxide from a source, otherwise a source of fuel waste, allowing it to be used as the main source of fuel without emission problems. In some cases, government policies require this removal of carbon dioxide, and the need to control carbon dioxide emissions will only increase in the future. Direct reduction involves the reduction of ores containing iron oxide into granules, ingots or pressed briquettes of metallized iron, where iron oxide is reduced by a gas containing hydrogen and / or carbon monoxide, resulting in the formation of carbon dioxide as a by-product.

Summary of the invention

In one exemplary embodiment of the present invention, a method for sequestering carbon dioxide from combustible blast furnace gas includes, provided that the blast furnace gas is divided into process gas and combustible blast furnace gas: mixing the process gas with hydrocarbon and supplying the resulting feed gas for reforming to the reforming unit carbon dioxide and steam for reforming a feed gas for a reforming unit and generating a reducing gas; and supplying combustible blast furnace gas to a carbon dioxide scrubber to remove at least some of the carbon dioxide from the combustible blast furnace gas and generating fuel gas for the reforming unit after adding the hydrocarbon fed to the carbon dioxide and steam reforming unit. The method also includes compressing the process gas and combustible blast furnace gas. The method further includes generating steam from the blast furnace gas. The method also further includes scrubbing the blast furnace gas to remove dust. Optionally, blast furnace gas is obtained from a reduction furnace. Optionally, the method also further includes mixing the reducing gas with oxygen and hydrocarbon to form gas from the annular pipeline and supplying gas from the annular pipeline to the reducing furnace. The carbon dioxide scrubber also produces a carbon dioxide-poor gas. The method also further comprises mixing a carbon dioxide poor gas with a reducing gas. Optionally, the method also further includes preheating the carbon dioxide poor gas before mixing it with the reducing gas or using it as a fuel. A carbon dioxide and steam reforming unit also produces flue gas. The method also further includes generating steam from the flue gas. Optionally, the method also further includes using flue gas to preheat another gas. Optionally, the blast furnace gas and gas from the annular pipeline are associated with a direct reduction process for converting iron oxide to metallic iron.

In another exemplary embodiment of the present invention, a device for sequestering carbon dioxide from combustible blast furnace gas comprises one or more pipelines for separating blast furnace gas into process gas and combustible blast furnace gas; one or more pipelines for mixing the process gas with the hydrocarbon and supplying the resulting feed gas for the reforming unit to the carbon dioxide reforming unit and steam for reforming the feed gas for the reforming unit and generating a reducing gas; and one or more pipelines for supplying combustible blast furnace gas to a carbon dioxide scrubber to remove at least some carbon dioxide from the combustible blast furnace gas and generating fuel gas for the reforming unit after adding hydrocarbon supplied to the carbon dioxide reforming unit and couple. The device also contains one or more gas compressors for compressing process gas and combustible blast furnace gas. The device further comprises a low pressure steam boiler for generating steam from the blast furnace gas. The device also further comprises a wet scrubber for scrubbing the blast furnace gas to remove dust. Optionally, blast furnace gas is obtained from a reduction furnace. Optionally, the device also further comprises one or more pipelines for mixing the reducing

- 1 028730 gas with oxygen and hydrocarbon to form gas from the annular pipeline and supply gas from the annular pipeline to the reduction furnace. The carbon dioxide scrubber also produces a carbon dioxide-poor gas. The device also further comprises one or more pipelines for mixing the carbon dioxide poor gas with the reducing gas. Optionally, the device also further comprises a pre-heating device for pre-heating the carbon dioxide poor gas before mixing it with the reducing gas or using it as fuel. A carbon dioxide and steam reforming unit also produces flue gas. The device also further comprises a low pressure steam boiler for generating steam from the flue gas. Optionally, the device also further comprises one or more pipelines for using flue gas to preheat another gas. Optionally, the blast furnace gas and gas from the annular pipeline are associated with a direct reduction process for converting iron oxide to metallic iron.

In a further exemplary embodiment of the present invention, a method for sequestering carbon dioxide from an exhaust gas and reusing it as a recycle gas without emission-related complications includes, provided that the gas source is separated into the process gas and the exhaust gas: mixing the process gas with a hydrocarbon and supplying the resulting feed gas to a reforming unit for reforming the feed gas and forming a reducing gas; and supplying at least a portion of the exhaust gas to a carbon dioxide scrubber to remove at least some of the carbon dioxide from the exhaust gas and form a carbon dioxide poor gas miscible with the reducing gas. Optionally, the method also includes supplying at least a portion of the exhaust gas to a carbon dioxide scrubber to remove at least some carbon dioxide from the exhaust gas and generating fuel gas after adding the hydrocarbon fed to the reforming unit.

The carbon dioxide sequestration processes of the present invention provide an efficient closed loop through which carbon monoxide and hydrogen not used in the primary process and removed as waste gas can be recaptured while minimizing undesired emissions.

A brief description of the graphic materials

The present invention is depicted and described herein with reference to various graphic materials in which similar reference numbers are used to indicate similar steps of the method / components of the device, if necessary, and in which in FIG. 1 shows a process diagram / flowchart of a method / apparatus for sequestering carbon dioxide from combustible blast furnace gas according to the present invention, and FIG. 2 shows a process diagram / flowchart of a direct reduction process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, in one exemplary embodiment of the present invention, the apparatus 10 for sequestering carbon dioxide from combustible blast furnace gas comprises a vertical shaft reduction furnace 12 or the like. In this example, the reduction furnace 12 comprises a loading hopper (not shown) into which granules, blanks or pressed briquettes of iron oxide are fed at a predetermined speed. Granules, blanks or pressed briquettes of iron oxide are lowered by gravity into the reduction furnace 12 from the feed hopper through a feed pipe (not shown), which also serves as a gas-tight pipe. In the lower part of the reduction furnace 12 there is a discharge pipe (not shown), additionally serving as a gas-tight pipe. An unloading feeder (not shown), such as an electric vibrating feeder or the like, is located under the unloading tube and receives granules, blanks or pressed briquettes of metallic iron, thereby forming a system for lowering the charge by gravity through a reduction furnace 12.

Approximately in the middle of the reduction furnace 12 is a ring pipe and tuyere system (not shown) through which the reducing gas is introduced at a temperature in the range of from about 700 to about 1050 ° C. Hot reducing gas flows upward through the reducing region of the reducing furnace 12 in the opposite direction to the flow of pellets, blanks or pressed briquettes, and exits the reducing furnace 12 through a gas exhaust pipe (not shown) located in the upper part of the reducing furnace 12. The supply pipe passes under the gas exhaust pipe, while this geometric arrangement creates a chamber for exhaust gas, allowing the exhaust gas to exit the level of the mound and flow freely to the exhaust one pipe. The hot reducing gas flowing from the ring pipe system and the tuyeres to the gas outlet pipe is used to heat pellets, blanks or pressed briquettes of iron oxide and to reduce them into pellets, blanks or pressed briquettes of metallic iron (i.e., through direct reduction). Hot reducing gas contains hydrogen, nitrogen, carbon monoxide, carbon dioxide, methane and water vapor, reducing granules, pigs or

- 2 028730 compressed briquettes of iron oxide and generating exhaust gas or blast furnace gas containing carbon dioxide and water vapor.

As shown in FIG. 2, the direct reduction processes used here control the reduction conditions, temperatures and chemical compositions at the point where the gas from the annular pipe enters the reduction furnace 12 by adjusting the addition of carbon dioxide-poor gas, natural gas and oxygen to the reducing gas immediately before point. These direct reduction processes are described generally in US Pat. No. 3,748,120, entitled Method for Reducing Iron Oxide to Metallic Iron, US Pat. No. 3,749,386, entitled Method for Reducing Iron Oxides in a Gas Recovery Process, US Pat. No. 3,764,123, entitled Device for Reducing Iron Oxide to Metallic iron, US patent No. 3816101, entitled Method for the reduction of iron oxides in the process of gas recovery, US patent No. 4046557, entitled Method for producing metal particles Lez № and U.S. Patent 5437708 entitled Preparation of iron carbide in a shaft furnace, the contents of all these patents are incorporated herein by reference.

The reduction furnace charge acts as an adiabatic reactor and promotes equilibrium reactions in the zone of gas injection from the annular pipeline. When gas from the annular pipeline enters the reduction furnace 12 and passes through the charge, the gas reacts to its equilibrium composition and temperature, which is observed on the thermocouples of the charge in the upper part of the reduction furnace 12.

The following factors of the flow of reducing gas influence the carburization reaction:

1. The initial ratio of hydrogen: carbon monoxide is a reducing gas.

2. The initial methane content in the reducing gas.

3. The initial temperature of the reducing gas.

4. Adding natural gas to the reducing gas.

5. Adding oxygen to the reducing gas.

6. Adding a carbon dioxide poor gas to a reducing gas.

7. The final ratio of reducing agent and oxidizing agent in the gas from the annular pipeline.

8. The final gas pressure from the annular pipeline.

Under normal operating conditions, the initial quality of the reducing gas is carefully monitored and becomes the main stability factor for the direct reduction process. As the reducing gas flows to the reducing furnace 12, natural gas is added based on an analysis of the methane content of the resulting gas from the ring pipe. This provides a stabilizing adjustment for any change in the methane content in the initial reducing gas and affects the carbonization potential of the resulting gas from the annular pipeline. Oxygen is added to the reducing gas to increase the temperature of the resulting gas from the annular pipeline and improve the dynamics of the iron ore reduction process.

Optionally, the operating conditions used include preheating the added natural gas, a methane content of the reducing gas of about 12 percent or less, and a stream / ton of added oxygen of 30 Nm ³ / t or less. In the operation of the direct reduction device, the gas leaves the source 40 of reducing gas and the first sensor performs gas analyzes and measures the temperature of the gas. Natural gas is then mixed with the gas at the inlet of the natural gas. Then, oxygen is mixed with a mixture of gas and natural gas at the oxygen inlet, thereby forming gas from the annular pipeline. The second sensor performs gas analysis and measures the temperature of the gas from the annular pipeline, before the gas enters from the annular pipeline into the reduction furnace 12.

As also shown in FIG. 1, in accordance with the present invention, blast furnace gas from a vent pipe of a reduction furnace 12 flows through yet another pipe (not shown) to a low pressure steam boiler 14. This makes it possible to efficiently generate steam for use elsewhere in the process, for example, in the carbon dioxide removal step described in more detail below. Boiler feed water is supplied to the low pressure steam boiler 14 and, as mentioned above in this application, the generated steam is recycled during the process or used elsewhere.

The blast furnace gas is then sent to a wet scrubber 20 provided to cool the blast furnace gas and remove dust with escaping water. The wet scrubber 20 may be of any conventional type known to those skilled in the art, such as a venturi scrubber with a nozzle tower (not shown), with blast furnace gas flowing down through the venturi scrubber and then up through the condensation counter stream to cooling water.

Blast furnace gas exits the wet scrubber 20 in the form of two streams under the influence of a valve (not shown). The first stream is a process gas and the second gas is a combustible blast furnace gas (i.e. waste). The ratio of these streams is determined by the available heat in the carbon dioxide and steam reforming unit 24 connected to the first stream, which is usually constant, resulting in an approximate ratio of 1: 1 (using a recycled carbon dioxide poor gas), 2: 1 ( without using recycled carbon dioxide poor gas), etc.

- 3,028,730

The process gas from the wet scrubber 20 is supplied to the compressor 22, compressed to the desired pressure, and then fed to a mixer (not shown), where the process gas is mixed with natural gas. This feed gas for the reforming unit is then supplied to the carbon dioxide and steam reforming unit 24. The carbon dioxide and steam reforming unit 24 includes fuel burners (not shown) that produce heated flue gas containing nitrogen, carbon dioxide and water by combustion, and a plurality of catalytic reforming unit pipes (not shown), wherein said pipes use feed gas for reforming units and combustion heat to form a reducing gas fed back to the reducing furnace 12 after introducing oxygen, natural gas and a carbon dioxide-poor gas, forming There is gas from the ring pipe.

Combustible blast furnace gas from the wet scrubber 20 is also supplied to the compressor 26 and compressed to the desired pressure before entering the scrubber 28 to remove carbon dioxide. The carbon dioxide scrubber 28 comprises a low pressure steam inlet, optionally obtained from any of the low pressure steam boilers 14, 32 of the carbon dioxide sequestration apparatus 10 from combustible blast furnace gas, and the discharge of feed water for the boiler, sulfur and carbon dioxide. Boiler feed water can be supplied to any of the low pressure steam boilers 14, 32 of the carbon dioxide sequestration device 10 from combustible blast furnace gas. Another product discharged from the carbon dioxide scrubber 28 is a carbon dioxide poor gas which, when mixed with natural gas, is partially converted into fuel gas for a reforming unit, fed to the carbon dioxide and steam reforming unit 24.

The carbon dioxide scrubber 28 may comprise any type of alkanolamine gas purification system such as MEA,, or the like, or any type of hot potassium gas purification system known to those skilled in the art. Low pressure steam is used to regenerate the solution used in the scrubber 28 for cleaning carbon dioxide, and comes out as feed water for the boiler. During the carbon dioxide removal process, sulfur and carbon dioxide are sequestered from combustible blast furnace gas in a scrubber. A combustible blast furnace gas without sulfur and carbon dioxide exits the scrubber 28 for purification of carbon dioxide in the form of a carbon dioxide-poor gas. As previously, a portion of the carbon dioxide-poor gas is mixed with natural gas to form fuel gas for the reforming unit and fed to the carbon dioxide and steam reforming unit 24 via fuel burners. The remainder of the carbon dioxide-poor gas is recycled and mixed with the reducing gas fed back to the reducing furnace 12 after supplying oxygen and natural gas, thereby forming gas from the ring pipe. Optionally, a subsequent portion of the carbon dioxide-poor gas, or the entire stream, is supplied to the preheater 30 before mixing with the existing reducing gas or using it as fuel.

In one exemplary embodiment of the present invention, this carbon dioxide-poor gas / reducing gas stream results in approximately 20 percent of the gas from the annular pipe supplied to the reduction furnace 12, while the reducing gas stream of the carbon dioxide reforming unit and steam ultimately amounts to approximately 80 percent of the gas from the annular pipe supplied to the reduction furnace 12, although other percentages are provided in this application.

A flue gas exhaust pipe (not shown) is located in a carbon dioxide and steam reforming unit 24 for removing flue gas containing nitrogen, carbon dioxide and water after combustion. The flue gas flows through one or more heat exchangers, including a low pressure steam boiler 32. As before, this allows steam to be efficiently generated for use elsewhere in the process, for example, in the carbon dioxide removal step described in more detail above. Boiler feed water is supplied to a low pressure steam boiler 32, optionally from a carbon dioxide scrubber 28, and, as mentioned above in this application, the generated steam is recycled during the process or used elsewhere. Thus, the low pressure steam boiler 32 can be connected to an optional preheater 30.

Variants of the above processes and devices can also be implemented within the basic ideas of the present invention. For example, the used carbon dioxide scrubber 28 may be an alternating pressure adsorption device (Ρ8Α), an alternating pressure adsorption device in vacuum (UR8A), or a membrane separator, as appropriate. The device ΜΌΕΑ can be used without steam, and can be directly heated by natural gas and / or export fuel, forming a device ΜΌΕΑ with direct heat exchange with blast furnace gas and / or flue gas. Captured carbon dioxide can be used for secondary methods of oil production, improved biofuel for the production of biofuels, production of building bricks from iron carbonate / iron silicate (small particles of Fe + CO ₂ + crushed steel slag), etc. The trapped carbon dioxide can also be reformed, and the resulting reformed gas can be used in the direct reduction process. A reformer / oxy-fuel heater may be used for the concentration of carbon dioxide in the flue gas. The conversion reactor can be used to convert carbon monoxide and water to carbon dioxide and H ₂ , then H ₂ can be fed as fuel to a reforming unit to create water. Carbon dioxide of flue gas can be captured from concentrated flue gas. Water can be trapped from flue gas for use in dry areas. Finally, a direct heating heater can be used to re-heat the depleted (purified) combustible blast furnace gas and / or process gases.

Although the present invention has been depicted and described herein with reference to preferred embodiments and specific examples thereof, it will be apparent to those skilled in the art that other embodiments and examples can perform similar functions and / or achieve similar results. All of these equivalent embodiments and examples are within the scope and concept of the present invention, are contemplated by the present invention, and are intended to be included in the following claims. In this regard, the foregoing description of the present invention should be considered non-limiting and comprehensive to the extent possible.

Claims (24)

CLAIM 1. The method of trapping carbon dioxide from combustible blast furnace gas in the direct reduction of iron oxide to metallic iron, comprising the separation of blast furnace gas into process gas and combustible blast furnace gas; mixing the process gas with hydrocarbon and supplying the resulting feed gas to a reforming unit for reforming the feed gas and forming a reducing gas; and supplying at least a portion of the combustible blast furnace gas to a carbon dioxide scrubber to remove at least some carbon dioxide from the combustible blast furnace gas and form a carbon dioxide poor gas at least partially miscible with the reducing gas; wherein the removed carbon dioxide is reformed and the resulting reformed gas is used in the direct reduction process. 2. The method according to claim 1, characterized in that it further comprises adding a hydrocarbon to a portion of the carbon dioxide poor gas that was not mixed with the reducing gas, and generating fuel gas for the reforming unit fed to the reforming unit. 3. The method according to claim 2, characterized in that it further includes compressing the process gas before mixing it with hydrocarbon and compressing the combustible blast furnace gas before feeding it to the scrubber for purification of carbon dioxide. 4. The method according to claim 1, characterized in that it further includes the formation of steam from a blast furnace gas. 5. The method according to claim 4, characterized in that it further includes scrubbing the blast furnace gas to remove dust. 6. The method according to claim 1, characterized in that the blast furnace gas is obtained from a reduction furnace. 7. The method according to claim 1, characterized in that it further comprises mixing the reducing gas with oxygen and hydrocarbon to form gas from the annular pipeline and supplying gas from the annular pipeline to the reduction furnace. 8. The method according to claim 1, characterized in that it further includes preheating the carbon dioxide poor gas before mixing it with the reducing gas. 9. The method according to claim 1, characterized in that the reforming unit also produces flue gas. 10. The method according to claim 9, characterized in that it further includes the formation of steam from the flue gas. 11. The method according to claim 10, characterized in that it further includes the use of flue gas for preheating another gas. 12. The method according to claim 1, characterized in that the blast furnace gas and reducing gas are used in the direct reduction process to convert iron oxide to metallic iron. 13. A device for implementing the method according to claim 1, comprising a reforming unit; carbon dioxide scrubber; one or more pipelines for separating blast furnace gas into process gas and combustible blast furnace gas; one or more pipelines for mixing the process gas with the hydrocarbon and supplying the resulting feed gas to a reforming unit for reforming the feed gas and generating a reducing gas; and one or more pipelines for supplying at least a portion of the combustible blast furnace gas to a carbon dioxide scrubber to remove at least some of the carbon dioxide from the combustible blast furnace gas and form a carbon dioxide poor gas mixed with reducing gas, and for supplying the removed carbon dioxide to the reforming unit for reforming the removed carbon dioxide and using the resulting reformed gas in a direct recovery process Lenia. 14. The device according to p. 13, characterized in that it further comprises one or more pipelines for mixing part of the carbon dioxide poor gas, which was not mixed with the reducing gas, with hydrocarbon and supplying the resulting fuel gas to the reforming unit. 15. The device according to 14, characterized in that it further comprises one or more gas compressors for compressing the process gas before mixing it with hydrocarbon and compressing the combustible blast furnace gas before feeding it to the scrubber for cleaning carbon dioxide. 16. The device according to item 13, characterized in that it further comprises a low pressure steam boiler for generating steam from blast furnace gas. 17. The device according to clause 16, characterized in that it further comprises a wet scrubber for scrubbing the blast furnace gas to remove dust. 18. The device according to p. 13, characterized in that it further comprises a reduction furnace for producing blast furnace gas. 19. The device according to item 13, characterized in that it further comprises one or more pipelines for mixing the reducing gas with oxygen and hydrocarbon to form gas from the annular pipeline and supply gas from the annular pipeline to the recovery furnace. 20. The device according to item 13, characterized in that it further comprises a device for preheating for preheating the carbon dioxide poor gas before mixing it with the reducing gas and using it as fuel. 21. The device according to item 13, wherein the installation of reforming carbon dioxide and steam also produces flue gas. 22. The device according to item 21, characterized in that it further comprises a low pressure steam boiler for generating steam from the flue gas. 23. The device according to p. 22, characterized in that it further comprises one or more pipelines for using flue gas to preheat another gas. 24. The device according to p. 13, characterized in that it is further configured to use blast furnace gas and reducing gas in the direct reduction process for converting iron oxide to metallic iron.