TWI576313B - Method and apparatus for sequestering carbon dioxide from a spent gas - Google Patents

Description

Method and device for isolating carbon dioxide from exhaust gas [Reciprocal Reference of Related Applications]

This patent application/patent is a continuation of the co-pending U.S. Patent Application Serial No. 12/762,618, entitled "Method and Apparatus for Isolating Carbon Dioxide from Exhaust Gases", which claims 2009 The priority of U.S. Provisional Patent Application Serial No. 61/170,999, entitled "Method and Apparatus for Isolating Carbon Dioxide from Top Gas Fuels", is incorporated herein by reference.

In other processes, the present invention is primarily directed to methods and apparatus for the direct reduction of iron oxide to metallic iron. In particular, the present invention relates to a method and apparatus for isolating carbon dioxide from an exhaust gas and joining the process.

In many industrial processes, there is a need for a cost effective and efficient method of removing carbon dioxide from a secondary fuel source, such as a top gaseous fuel source, in a direct reduction process. In other words, in many industrial processes, there is a benefit of removing carbon dioxide from other sources of waste fuel. The need for a performance method is used as a primary fuel source without emissions issues. In some cases, government policies need to remove this carbon dioxide, and the demand for carbon dioxide emissions control will only increase in the future. Direct reduction involves reduction of iron oxide ore into metallized iron pellets, agglomerates, or compacts in which iron oxide is reduced by a gas containing hydrogen and/or carbon monoxide to form carbon dioxide by-products.

In an exemplary embodiment of the invention, a method of isolating carbon dioxide from a top gaseous fuel, comprising: separating a top gas into a process gas and a top gas fuel: mixing process gas with a hydrocarbon and feeding the resulting reformer The gas is sent to a reformer of carbon dioxide and steam to recombine the reformer feed gas and form a reducing gas; and the top gaseous fuel is fed to the carbon dioxide scrubber to remove at least some carbon dioxide from the top gaseous fuel, and A reformer fuel gas is formed after the addition of hydrocarbons to the carbon dioxide and steam reformers. The method also includes compressing the process gas and the top gaseous fuel. The method also includes generating steam from the top gas. The method still further includes washing the top gas to remove dust. Optionally, the overhead gas system is obtained from a reduction furnace. Optionally, the method further comprises mixing the reducing gas with oxygen and a hydrocarbon to form a bustle gas and feeding the loop gas to the reduction furnace. Carbon dioxide scrubbers also produce carbon dioxide lean gas. The method still further includes mixing the carbon dioxide lean gas with the reducing gas. Optionally, the method further comprises preheating the carbon dioxide lean gas and the reducing gas prior to mixing it or using it as a fuel. Carbon dioxide and steam recombiners can also produce flue gas. The method further includes generating from the flue gas steam. Optionally, the method further comprises preheating the other gas using the flue gas. Optionally, the top gas and loop gas are combined with a direct reduction process to convert the iron oxide to metallic iron.

In another exemplary embodiment of the invention, an apparatus for isolating carbon dioxide from a top gaseous fuel, comprising: one or more conduits for separating a top gas into a process gas and a top gaseous fuel; one or more Mixing process gas with hydrocarbons and sending the resulting reformer feed gas to a reactor of carbon dioxide and steam to recombine the reformer feed gas and forming a conduit for reducing gas; and one or more for introducing the top gaseous fuel The carbon dioxide scrubber is fed to form a conduit for recombiner fuel gas after at least some of the carbon dioxide is removed from the overhead gas fuel and after the hydrocarbons fed to the carbon dioxide and steam reformer are added. The apparatus also includes one or more gas compressors for compressing the process gas and the top gaseous fuel. The apparatus still further includes a low pressure steam boiler for generating steam from the overhead gas. The apparatus still further includes a wet scrubber for scrubbing the top gas to remove dust. Optionally, the overhead gas system is obtained from a reduction furnace. Optionally, the apparatus further includes one or more conduits for mixing the reducing gas with oxygen and hydrocarbons to form a loop gas and feeding the loop gas to the reduction furnace. Carbon dioxide scrubbers also produce carbon dioxide lean gas. The apparatus still further includes one or more conduits for mixing the carbon dioxide lean gas with the reducing gas. Optionally, the apparatus further includes a preheater that preheats the carbon dioxide lean gas and the reducing gas before they are used as a fuel. Carbon dioxide and steam recombiners also produce flue gas. The apparatus still further includes a low pressure steam boiler for generating steam from the flue gas. Selectively, this dress The return further includes one or more conduits that preheat the other gas with the flue gas. Optionally, the top gas and loop gas are combined with a direct reduction process to convert the iron oxide to metallic iron.

In another exemplary embodiment of the present invention, a method of sequestering carbon dioxide from an exhaust gas and recycling it into a recycle gas that does not need to be discharged includes: separating the gas source into a process gas and an exhaust gas: mixing the process gas with a hydrocarbon and The resulting feed gas is sent to a reformer to recombine the feed gas and form a reducing gas; and at least a portion of the exhaust gas is fed to the carbon dioxide scrubber to remove at least some of the carbon dioxide from the exhaust gas and form a carbon dioxide mixed with the reducing gas Poor. Optionally, the method further comprises feeding at least a portion of the off-gas to the carbon dioxide scrubber to remove at least some of the carbon dioxide from the exhaust gas and forming a fuel gas after the addition of hydrocarbons fed to the reformer.

The carbon dioxide sequestration process of the present invention provides an efficient loop in which carbon monoxide and hydrogen are not used in the main process and the exhaust gases can be recaptured while minimizing unnecessary emissions.

10‧‧‧ top gas fuel

12‧‧‧Reduction furnace

14‧‧‧Low-pressure steam boiler

20‧‧‧ Wet scrubber

22‧‧‧Compressor

24‧‧‧Carbon dioxide and steam recombiner

26‧‧‧Compressor

28‧‧‧CO2 scrubber

30‧‧‧Selected preheater

32‧‧‧Low-pressure steam boiler

40‧‧‧Reducing gas source

The description and illustration of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals are used to identify the same method steps, apparatus, and components, and wherein: Figure 1 is the gas from the top of the present invention. Process/schematic diagram of a method/device for isolating carbon dioxide in a fuel; and Figure 2 is a process/schematic diagram of a direct reduction process of the present invention.

Referring to Figure 1, in an exemplary embodiment of the invention, the means for isolating carbon dioxide from the top gaseous fuel 10 includes essentially a shaft type reduction furnace 12 or the like. In this example, the reduction furnace 12 includes a feed hopper (not shown) into which iron oxide pellets, agglomerates or compacts are fed at a predetermined rate. These iron oxide pellets, agglomerates or pressed products are subjected to gravity and fall from the feed hopper through a feed pipe (not shown) into the reduction furnace 12, which can also be used as a gas seal pipe. The bottom of the reduction furnace 12 is a discharge pipe (not shown) which can be further used as a gas seal pipe. A discharge feeder (not shown), such as an electric vibrating feeder, is disposed under the discharge tube and receives metal iron pellets, agglomerates or pressed products, thereby establishing a charge through the reduction furnace 12. A system in which gravity falls.

The approximate midpoint of the reduction furnace 12 is a loop and tuyere system (not shown) through which the hot reducing gas is introduced at a temperature between about 700 ° C and about 1050 ° C. The hot reducing gas flows upward through the reducing zone of the reduction furnace 12, opposite to the flow direction of the pellets, agglomerates or compacts, and exits the reduction furnace 12 via an exhaust pipe (not shown) located at the top of the reduction furnace 12. The feed tube extends below the exhaust pipe, and such a geometric configuration creates an exhaust gas release space that allows the exhaust gas to be detached from the charge line and free to flow to the exhaust pipe. a hot reducing gas that flows from the loop and tuyere system to the exhaust pipe to heat the iron oxide pellets, agglomerates or compacts and to form them into metal iron pellets, briquettes or pressed products (ie via Direct restore). The hot reducing gas comprises hydrogen, nitrogen, carbon monoxide, carbon dioxide, methane and water vapor, which can reduce iron oxide pellets, agglomerates or pressed products, and Produce exhaust gas containing carbon dioxide and water vapor, or top gas.

Referring to Figure 2, the direct reduction process used herein controls the reduction conditions, temperature, and chemistry by adjusting the carbon dioxide lean, natural gas, and oxygen previously added to the reducing gas to the location where the loop gas enters the reduction furnace 12. behavior. For the direct reduction process, reference is made to U.S. Patent No. 3,748,120, entitled "Method for Reduction of Iron Oxide in a Gas Phase Reduction Process", entitled "Method for Reducing Iron Oxide to Metal Iron", entitled "Iron Oxide" U.S. Patent No. 3,764,123, the disclosure of which is incorporated herein by reference to U.S. Pat. U.S. Patent No. 5,437,708, the disclosure of which is incorporated herein by reference in its entirety in its entirety in its entirety in its entirety in its entirety in

The reduction charge is used as a large adiabatic reactor and promotes an equilibrium reaction in the gas injection zone of the loop. As the loop gas enters the reduction furnace 12 and passes through the charge, the gas reacts to reach equilibrium composition and temperature, while the temperature is observed by the charge thermocouple located in the upper half of the reduction furnace 12.

The carburization reaction will be affected by the following reduction gas flow factors: 1. hydrogen in the initial reducing gas: carbon monoxide ratio; 2. methane content of the initial reducing gas; 3. initial reducing gas temperature; 4. natural gas added to the reducing gas ; 5. oxygen added to the reducing gas; 6. carbon dioxide lean gas added to the reducing gas; 7. Reducing agent in the final loop gas: oxidant ratio; and 8. Final loop gas pressure

Under normal operating conditions, the quality of the initial reducing gas is tightly controlled and is a major stabilizing factor in the direct reduction process. When the reducing gas flows to the reduction furnace 12, natural gas is added based on the analysis of the methane content of the final loop gas. This provides a stability adjustment for any change in the methane content of the initial reducing gas and affects the carburizing ability of the final loop gas. Oxygen is added to the reducing gas to increase the temperature of the final loop gas and improve the kinetics of the iron ore reduction process.

Optionally, the operating conditions employed include preheating the added natural gas, the reducing gas methane content being equal to or less than about 12%, and the oxygen addition flow rate per ton being equal to or less than about 30 standard cubic meters per ton.

During use of the direct reduction device, the gas exits the reducing gas source 40 and gas analysis is performed with the first sensor while measuring the gas temperature. The natural gas is then mixed with the gas at the natural gas inlet. A mixture of oxygen and the gas and natural gas is then mixed at the oxygen inlet to form a loop gas. Before the loop gas enters the reduction furnace 12, gas analysis is performed with a second sensor and the temperature of the loop gas is measured.

Referring again to Figure 1, in accordance with the present invention, the overhead gas from the exhaust pipe of the reduction furnace 12 flows to the low pressure steam boiler 14 via another line (not shown). This will enable steam to be efficiently produced for use elsewhere in the process, such as the carbon dioxide removal step as described in more detail below. The boiler feed water is sent to the low pressure steam boiler 14, and as previously described herein, the generated steam is recirculated through the process or used elsewhere.

The top gas is then directed to a wet scrubber 20 which is used to cool the overhead gas and remove dust. The wet scrubber 20 can be of any conventional type known to those skilled in the art, such as a venturi (not shown) with a packed column, with the overhead gas flowing down the Buchrich scrubber and It then flows upward through the packed bed and flows countercurrently to the cooling water.

The top gas is discharged into the wet scrubber 20 by two streams by the effect of a valve (not shown). The first gas stream represents the process gas and the second gas stream represents the top gas fuel (ie, the exhaust gas). The ratio of these gas streams is determined by the amount of heat available in the carbon dioxide and steam reformer 24 coupled to the first gas stream, which is typically fixed, an exemplary example of which is 1:1 (using recycled carbon dioxide lean gas), 2:1 (not using recycled carbon dioxide lean gas) and so on.

The process gas from the wet scrubber 20 is sent to the compressor 22 and compressed to the desired pressure and then fed to a mixer (not shown) where the process gas is mixed with the natural gas system. The reformer feed gas is then passed to a carbon dioxide and steam reformer 24. The carbon dioxide and steam reformer 24 includes a burner for burning fuel (not shown) to produce heated flue gas containing nitrogen, carbon dioxide, and water via combustion, and a plurality of catalytic reforming tubes (not shown) for catalysis. The recombination tube will use the reformer feed gas and the heat from the combustion to form a reducing gas. After the oxygen, natural gas, and carbon dioxide lean gas are introduced into the reduction furnace 12, the reducing gas will be sent back to the reduction furnace 12, resulting in a loop gas.

The top gaseous fuel from the wet scrubber 20 is also sent to the compressor 26 prior to being fed to the carbon dioxide scrubber 28, and is pressurized Retract to the required pressure. The carbon dioxide scrubber 28 has an input of low pressure steam that is selectively obtained from any of the low pressure steam boilers 14, 32 for the apparatus for isolating carbon dioxide from the overhead gas fuel 10, as well as the output of boiler feed water, sulfur, and carbon dioxide. The boiler feed water can be fed to any of the low pressure steam boilers 14, 32 for the means for isolating carbon dioxide from the overhead gaseous fuel 10. Another output of carbon dioxide scrubber 28 is carbon dioxide lean, which, when mixed with natural gas, partially becomes recombiner fuel gas and is fed to carbon dioxide and steam reformer 24.

Carbon dioxide scrubber 28 can include any type of alkanolamine such as MEA, MDEA, etc., or any type of hot potassium scrubbing system known to those skilled in the art. Low pressure steam is used to regenerate the solution used in the carbon dioxide scrubber 28 and to be discharged from the boiler feed water. During the carbon dioxide scrubbing process, sulfur and carbon dioxide are separated from the top gaseous fuel. The top gaseous fuel after deducting sulfur and carbon dioxide will be depleted of carbon dioxide by the carbon dioxide scrubber 28. Again, a portion of the carbon dioxide lean gas is mixed with natural gas to form a reformer fuel gas and introduced into the carbon dioxide and steam reformer 24 via a burner that combusts the fuel. The remaining carbon dioxide lean gas is recovered and mixed with the reducing gas, and after the oxygen and natural gas are introduced into the reduction furnace 12, they are returned to the reduction furnace 12, thereby forming a loop gas. Alternatively, the second half of the carbon dioxide lean gas or the entire gas stream may be fed to the preheater 30 prior to mixing with the existing reducing gas or using it as a fuel.

In an exemplary embodiment of the present invention, the carbon dioxide lean/reduced gas stream finally accounts for about the loop gas supplied to the reduction furnace 12. The 20%, while the carbon dioxide and steam reformer reduction gas stream is about 80% of the loop gas supplied to the reduction furnace 12, although other percentages are also taken into account.

A flue gas exhaust pipe (not shown) is provided to the carbon dioxide and steam reformer 24 to remove flue gas containing nitrogen, carbon dioxide and water after combustion. The flue gas will flow through one or several heat exchangers, including a low pressure steam boiler 32. Again, this will enable steam to be efficiently produced for use elsewhere in the process, such as the carbon dioxide removal step as described in more detail below. The boiler feed water is sent to a low pressure steam boiler 32, which is selectively from the carbon dioxide scrubber 28, and as previously described herein, the steam produced may be recycled via the process or used elsewhere. Therefore, the low pressure steam boiler 32 can be coupled to the optional preheater 30.

The above processes and apparatus may also be implemented with variations without departing from the basic concepts of the invention. For example, the carbon dioxide scrubber 28 used may be a pressure swing adsorption (PSA) unit, a vacuum pressure swing adsorption (VPSA) unit, or a membrane separator, as desired. It is also possible to use MDEA units without steam and direct ignition with natural gas and/or outlet fuel to provide direct heat exchange of the MDEA with the overhead gas and/or flue gas. The captured carbon dioxide can be used to improve oil recovery, enhance biological growth of biofuel production, and produce carbonic acid/iron silicate bricks (iron powder + CO2+ floor steel slag). The captured carbon dioxide can also be recombined and the resulting reformed gas used in the direct reduction process. An oxygen-fired reformer/heater can be used to concentrate the flue gas carbon dioxide. Using the shift reactor carbon monoxide and water into carbon dioxide and hydrogen, and H ₂ can be burned to produce a recombinant heated water. The flue gas carbon dioxide can be captured from the concentrated flue gas. Water can be captured from the flue gas for use in the drying area. Finally, a lean-fired heater can be used to reheat the lean (washed) top gaseous fuel and/or process gas.

Although the present invention has been illustrated and described with respect to the preferred embodiments and specific examples thereof, those skilled in the art will readily appreciate that other embodiments and embodiments can perform similar functions and/or Achieve similar results. All such equivalent embodiments and examples are considered to be within the spirit and scope of the invention and are therefore intended to be included within the scope of the appended claims. Accordingly, the above detailed description of the present invention should be considered as non-limiting and the maximum possibility is included as much as possible.

10‧‧‧ top gas fuel

12‧‧‧Reduction furnace

14‧‧‧Low-pressure steam boiler

20‧‧‧ Wet scrubber

22‧‧‧Compressor

24‧‧‧Carbon dioxide and steam recombiner

26‧‧‧Compressor

28‧‧‧CO2 scrubber

30‧‧‧Selected preheater

32‧‧‧Low-pressure steam boiler

Claims (26)

A method of isolating carbon dioxide from a top gaseous fuel, comprising: separating a top gas into a process gas and a top gas fuel: mixing a hydrocarbon with the process gas and sending the resulting reformer feed gas to a reformer to recombine the recombination Feeding gas and forming a reducing gas; and feeding at least a portion of the overhead gas fuel to the carbon dioxide scrubber to remove at least some of the carbon dioxide from the top gaseous fuel and forming selectively with the reducing gas a mixed carbon dioxide lean gas; wherein the carbon dioxide scrubber is one of a pressure swing adsorption (PSA) unit, a vacuum pressure swing adsorption (VPSA) unit, and a membrane separator; wherein the ratio of the process gas phase to the top gas fuel is Retrieving the heat available in the reformer fed by the reformer feed gas; wherein the ratio of the process gas phase to the top gas fuel is when the carbon dioxide lean gas is completely used to mix with the reducing gas Is a first relatively low ratio, and when the carbon dioxide lean gas is not used to mix with the reducing gas, the process gas phase is for the top The proportion of the second fuel body is a relatively high proportion; and wherein the carbon dioxide is captured and reused to recombinant direct reduction process. The method of claim 1, further comprising feeding at least a portion of the overhead gas fuel to the carbon dioxide scrubber to remove at least some carbon dioxide from the top gaseous fuel, and adding Recombiner fuel gas is formed after the hydrocarbons in the reformer are fed. The method of claim 2, further comprising compressing the process gas and the top gaseous fuel. The method of claim 1, further comprising generating steam from the top gas. The method of claim 4, further comprising washing the top gas to remove dust. The method of claim 1, wherein the top gas system is obtained from a reduction furnace. The method of claim 1, further comprising mixing the reducing gas with oxygen and a hydrocarbon to form a bustle gas, and feeding the loop gas to the reduction furnace. The method of claim 1, further comprising preheating the carbon dioxide lean gas prior to mixing the carbon dioxide lean gas with the reducing gas. The method of claim 1, wherein the carbon dioxide and steam reformer also produces flue gas. The method of claim 9, further comprising generating steam from the flue gas. The method of claim 10, further comprising preheating the other gas using the flue gas. The method of claim 1, wherein the top gas and the reducing gas are combined with a direct reduction process to convert the iron oxide to metallic iron. An apparatus for isolating carbon dioxide from a top gaseous fuel, comprising: one or more conduits for separating a top gas into a process gas and a top gaseous fuel; one or more for mixing the process gas with a hydrocarbon and the resulting Reactor feed gas is sent to the reformer to recombine the reformer feed gas and form a conduit for reducing gas; and one or more for feeding at least a portion of the overhead gas fuel to the carbon dioxide scrubber At least some carbon dioxide is removed from the top gaseous fuel, and a carbon dioxide lean gas conduit is formed that is mixed with the reducing gas; wherein the carbon dioxide scrubber is a pressure swing adsorption (PSA) unit, a vacuum pressure swing adsorption (VPSA) unit, and a membrane. One of the separators; wherein the ratio of the process gas phase to the top gas fuel is back to the heat that can be obtained in the reformer fed by the reformer feed gas; wherein, when the carbon dioxide lean gas is completely used When mixed with the reducing gas, the ratio of the process gas phase to the top gas fuel is a first relatively low ratio, and when the carbon dioxide lean gas is not used to mix with the reducing gas, the process gas phase is The ratio of the top gaseous fuel is a second relatively high ratio; and the carbon dioxide captured therein is recombined and reused to a direct reduction process. The apparatus of claim 13 further comprising one or more for feeding at least a portion of the overhead gas fuel to the carbon dioxide scrubber to remove at least some carbon dioxide from the top gaseous fuel and to add a feedstock A conduit to the reformer fuel gas is formed after the hydrocarbons in the reformer. The apparatus of claim 14, further comprising one or more gas compressors for compressing the process gas and the top gaseous fuel. The apparatus of claim 13 further comprising a low pressure steam boiler for generating steam from the overhead gas. The apparatus of claim 16, further comprising a wet scrubber for washing the top gas to remove dust. The apparatus of claim 13 wherein the top gas system is obtained from a reduction furnace. The apparatus of claim 13 further comprising one or more conduits for mixing the reducing gas with oxygen and hydrocarbons to form a loop gas and feeding the loop gas to the reduction furnace. The apparatus of claim 13, further comprising a preheater that preheats the carbon dioxide lean gas before mixing the carbon dioxide lean gas with the reducing gas or before using the carbon dioxide lean gas as a fuel. The apparatus of claim 13 wherein the carbon dioxide and steam reformer also produces flue gas. The apparatus of claim 21, further comprising a low pressure steam boiler for generating steam from the flue gas. The apparatus of claim 22, further comprising one or more conduits for preheating the other gas with the flue gas. The apparatus of claim 13 wherein the top gas and the reducing gas are combined with a direct reduction process to convert the iron oxide to metallic iron. A method of sequestering carbon dioxide from exhaust gas and recycling it into a recycle gas that does not need to be discharged, comprising: separating a gas source into a process gas and an exhaust gas: mixing the process gas with a hydrocarbon and feeding the resulting feed gas to a recombiner Recombining the feed gas and forming a reducing gas; and feeding at least a portion of the exhaust gas to the carbon dioxide scrubber, Reducing at least some carbon dioxide from the exhaust gas and forming a carbon dioxide lean gas selectively mixed with the reducing gas; wherein the carbon dioxide scrubber is a pressure swing adsorption (PSA) unit, a vacuum pressure swing adsorption (VPSA) unit, and a membrane separation One of the processes; wherein the ratio of the process gas phase to the exhaust gas is back to the heat that can be obtained in the reformer to which the feed gas is fed; wherein, when the carbon dioxide lean gas is completely used with the reducing gas When mixing, the ratio of the process gas phase to the exhaust gas is a first relatively low ratio, and when the carbon dioxide lean gas is not used for mixing with the reducing gas, the ratio of the process gas phase to the exhaust gas is the second relative A higher ratio; and the carbon dioxide captured therein is recombined and reused to a direct reduction process. The method of claim 25, further comprising feeding at least a portion of the off-gas to the carbon dioxide scrubber to remove at least some carbon dioxide from the exhaust gas and forming after adding hydrocarbons fed to the reformer Fuel gas.