Method and system for preparing gas-based shaft furnace reducing gas from converter gas

Abstract

The invention relates to the technical field of iron and steel smelting, and provides a method and a system for preparing gas-based shaft furnace reducing gas from converter gas, the method comprises the following steps: respectively pretreating converter gas generated by a converter and top gas generated by a shaft furnace to recover waste heat in the gas and remove impurities in the gas; and introducing the pretreated converter gas, the pretreated top gas, carbon dioxide, oxygen and natural gas into a reforming furnace for catalytic reforming to generate reducing gas, and introducing the reducing gas into the shaft furnace for smelting the direct reduction iron. The method can solve the problem that the current converter gas resource recovery effect is relatively low, utilizes the sensible heat and reducing capacity of the converter gas, combines a catalytic reforming technology, catalyzes and reforms the converter gas, the top gas and other gases into the reducing gas, reduces the preparation cost of the gas-based shaft furnace reducing gas, and realizes efficient utilization of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular to a method and system for preparing gas-based shaft furnace reducing gas by utilizing converter gas. Background Art

[0002] With increasing demands for environmental protection and energy efficiency, the steel industry, a typical industry with high energy consumption and emissions, faces tremendous pressure to transform and upgrade. Traditional blast furnace ironmaking processes, due to their high carbon dioxide emissions, are no longer able to meet modern environmental standards. Therefore, developing efficient and low-pollution iron ore reduction technologies has become a key research focus in the industry. Gas-based shaft furnace reduction technology, an advanced alternative to blast furnace ironmaking, utilizes clean gases such as natural gas and hydrogen as reducing agents, significantly reducing carbon emissions and improving iron ore reduction efficiency. The resulting direct reduced iron (DRI), with its pure quality and stable composition, is an ideal raw material for replacing scrap steel and smelting high-quality and specialty steels. However, the high cost of natural gas or hydrogen limits the widespread application of this technology. Furthermore, when pure hydrogen is used as a reducing agent, the reduction reaction is endothermic, resulting in a heat balance requirement far exceeding the chemical balance requirement. This results in lower furnace temperatures, low hydrogen utilization, and the need for additional heat. Therefore, direct reduction smelting technologies using hydrogen-rich gas (H2 + CO) as the reducing gas are gaining popularity. The most common process flows for hydrogen-rich (H2+CO) direct reduction smelting technology are MIDREX and HYL, both of which use carbon monoxide (CO) and hydrogen (H2) generated by natural gas reforming as reducing gases.

[0003] As a by-product of the converter steelmaking process, converter gas mainly contains carbon monoxide (CO) (about 45% to 55%), carbon dioxide (CO2), oxygen (O2), nitrogen (N2) and argon (Ar), as well as FeO, Fe2O3, CaO, SiO2 and other dust carried by the gas. Its total dust content is 80g / Nm 3 ~150g / Nm 3 If directly discharged into the atmosphere, it not only pollutes the environment but also underutilizes the sensible heat of 1400°C to 1500°C carried by converter gas, resulting in significant energy waste. Furthermore, if converter gas is used solely for combustion to generate electricity, its potential chemical energy and reducing capacity are not fully utilized. Therefore, current converter gas treatment methods are relatively limited, limited to simple heat recovery and utilization in waste heat boilers, resulting in low resource recovery efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for preparing gas-based shaft furnace reducing gas from converter gas, so as to solve the problem of low recovery efficiency of converter gas resources. By utilizing the sensible heat and reducing capacity of converter gas and combining it with catalytic reforming technology, converter gas and top gas and other gases are catalytically reformed into reducing gas, thereby reducing the preparation cost of gas-based shaft furnace reducing gas and achieving efficient utilization of resources.

[0005] The above technical objectives of the present invention are mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a method for preparing gas-based vertical furnace reducing gas from converter gas, which includes pretreating the converter gas generated by the converter and the top gas generated by the vertical furnace respectively to recover waste heat in the gas and remove impurities in the gas, passing the pretreated converter gas, the pretreated top gas, carbon dioxide, oxygen and natural gas into a reforming furnace for catalytic reforming to generate reducing gas, and passing the reducing gas into the vertical furnace for smelting direct reduced iron.

[0007] In a preferred embodiment of the present invention, the pretreatment process of the converter gas includes cooling, impurity removal and preheating in sequence; the pretreatment process of the top gas includes cooling, impurity removal and preheating in sequence;

[0008] The cooling treatment of the converter gas and the preheating treatment of the top gas are achieved through convection heat exchange between the two; the preheating treatment of the converter gas and the cooling treatment of the top gas are also achieved through convection heat exchange between the two.

[0009] In a preferred embodiment of the present invention, the impurity removal process of the converter gas includes dust removal and desulfurization performed in sequence; the impurity removal process of the top gas includes dust removal, desulfurization and dehydration performed in sequence.

[0010] In a preferred embodiment of the present invention, the converter gas that has undergone impurity removal is divided into two parts, and the top gas flowing out of the vertical furnace outlet is also divided into two parts. The two parts of the converter gas are subjected to convection heat exchange with the two parts of the top gas respectively to achieve preheating of the converter gas and cooling of the top gas; after being preheated, the two parts of the converter gas are respectively introduced into the reforming furnace as combustion gas and raw gas, and the two parts of the top gas are merged after heat exchange and cooling for impurity removal.

[0011] In a preferred embodiment of the present invention, the converter gas flowing out of the converter outlet is divided into two parts, one part of the converter gas is subjected to convection heat exchange with the top gas after impurity removal to achieve cooling of the converter gas and preheating of the top gas, and the other part of the converter gas is subjected to convection heat exchange with the natural gas to achieve cooling of the converter gas and preheating of the natural gas before it is introduced into the reforming furnace; the two parts of the converter gas are merged after heat exchange and cooling for impurity removal.

[0012] In a preferred embodiment of the present invention, the preheated top gas is mixed with the carbon dioxide and then introduced into the reforming furnace.

[0013] On the other hand, the present invention also provides a system for preparing gas-based shaft furnace reducing gas from converter gas, comprising:

[0014] A converter gas processing unit, comprising a converter, a first heat exchanger, a first impurity removal device, and a second heat exchanger connected in sequence via pipelines;

[0015] a top gas processing unit, the top gas processing unit comprising a vertical furnace, the second heat exchanger, a second impurity removal device, and the first heat exchanger sequentially connected via a pipeline;

[0016] A reducing gas preparation unit, comprising a carbon dioxide supply device, an oxygen supply device, a natural gas supply device, and a reforming furnace. The carbon dioxide supply device, the oxygen supply device, the natural gas supply device, the outlet of the second heat exchanger in the converter gas treatment unit, and the outlet of the first heat exchanger in the top gas treatment unit are all connected to the reforming furnace through pipelines, and the outlet of the reforming furnace is connected to the inlet of the vertical furnace.

[0017] In a preferred embodiment of the present invention, the outlet of the first impurity removal device is connected to two converter gas outlet pipes arranged in parallel, the two converter gas outlet pipes are respectively provided with the second heat exchanger and the third heat exchanger, and the outlets of the two converter gas outlet pipes are both connected to the reforming furnace; the outlet of the vertical furnace is connected to two top gas inlet pipes arranged in parallel, the second heat exchanger and the third heat exchanger are respectively provided on the two top gas inlet pipes, and the outlets of the two top gas inlet pipes are converged and connected to the second impurity removal device.

[0018] In a preferred embodiment of the present invention, the outlet of the converter is connected to two converter gas inlet pipes arranged in parallel, and the two converter gas inlet pipes are respectively provided with the first heat exchanger and the fourth heat exchanger, and the two converter gas inlet pipes are connected to the first impurity removal device after being converged; the outlet of the second impurity removal device is connected to a furnace top gas outlet pipe, the first heat exchanger is provided on the furnace top gas outlet pipe, a natural gas supply pipe is connected between the natural gas supply device and the reforming furnace, and the fourth heat exchanger is provided on the natural gas supply pipe.

[0019] In a preferred embodiment of the present invention, the first impurity removal device includes a first dust collector and a first desulfurizer connected in sequence through pipelines; and / or the second impurity removal device includes a second dust collector, a second desulfurizer and a dehydrator connected in sequence through pipelines.

[0020] Compared with the prior art, the technical solution of the present invention has the following characteristics and advantages:

[0021] The method and system for preparing gas-based shaft furnace reducing gas from converter gas disclosed in the present invention fully utilize the sensible heat of converter flue gas for heat exchange treatment, thereby achieving preheating of natural gas and treated gas-based shaft furnace top gas. At the same time, the main components in the converter gas are recovered and used as fuel gas and raw gas for the reformer, respectively. The main component, CO, provides energy for the reformer reaction, and CO2 serves as a raw material for the reformer reaction, thereby achieving full utilization of the thermal energy and chemical energy in the converter gas, reducing the preparation cost of the gas-based shaft furnace reducing gas, achieving efficient resource utilization, and having significant economic and environmental benefits.

[0022] The method and system for preparing gas-based vertical furnace reducing gas from converter gas disclosed in the present invention recover the heat of the gas-based vertical furnace top gas, and respectively exchange heat with the reforming furnace fuel gas and raw gas output from the converter gas through two heat exchangers, thereby reducing the temperature of the top gas, facilitating dust removal and subsequent process treatment, and simultaneously increasing the temperature of the fuel gas and raw gas, thereby preventing energy consumption caused by the addition of cold materials to the reforming furnace. At the same time, the gas-based vertical furnace is subjected to processes such as impurity removal, so that the gas obtained has a high CO2 content and can be used as a supplementary gas for the CO2 of the reforming furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0024] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the drawings are merely illustrative and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to specific circumstances under the guidance of the present invention.

[0025] Figure 1 This is a schematic structural diagram of the system for preparing gas-based shaft furnace reducing gas from converter gas according to the present invention.

[0026] Description of reference numerals:

[0027] 10. Converter; 11. First heat exchanger; 12. Second heat exchanger; 13. Third heat exchanger; 14. Fourth heat exchanger; 15. First dust collector; 16. First desulfurizer; 17. Converter gas inlet pipe; 18. Converter gas outlet pipe;

[0028] 20. Vertical furnace; 21. Second dust collector; 22. Second desulfurizer; 23. Dehydrator; 24. Top gas inlet pipe; 25. Top gas outlet pipe;

[0029] 30. Reforming furnace; 31. Carbon dioxide supply device; 32. Oxygen supply device; 33. Natural gas supply device; 34. Natural gas supply pipe; 35. Carbon dioxide supply pipe. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0031] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an element centered thereon. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Implementation method one:

[0034] like Figure 1 As shown, the present invention provides a method for preparing gas-based shaft furnace reducing gas from converter gas, which comprises the following steps:

[0035] The converter gas produced by the converter 10 and the top gas produced by the shaft furnace 20 are pre-treated to recover waste heat and remove impurities in the gas;

[0036] The pre-treated converter gas, pre-treated top gas, carbon dioxide, oxygen and natural gas are introduced into the reforming furnace 30 for catalytic reforming to generate reducing gas;

[0037] The reducing gas is introduced into the vertical furnace 20 for smelting direct reduced iron.

[0038] The method for preparing gas-based shaft furnace reducing gas from converter gas disclosed in the present invention recovers the main components in the converter gas, utilizes the sensible heat and reducing capacity of the converter gas, and combines catalytic reforming technology to catalytically reform converter gas and top gas into reducing gas, thereby reducing the production cost of the gas-based shaft furnace reducing gas, achieving efficient resource utilization, and having significant economic and environmental benefits.

[0039] The following describes the detailed preparation process of the method for preparing gas-based shaft furnace reducing gas from converter gas according to the present invention.

[0040] The preparation method of the present invention comprises a gas pretreatment step taking converter gas as the treatment object, a top gas pretreatment step taking top gas as the treatment object, and a catalytic reforming step using a catalytic reforming method.

[0041] like Figure 1 As shown in the gas pretreatment step, the converter gas produced by the converter 10 is treated. The converter gas produced by the converter 10 contains a large amount of carbon monoxide, carbon dioxide, oxygen, water vapor, dust and other components, with a temperature of about 1500°C and a calorific value of 7500kJ / m 3 ~8000kJ / m 3 The main components of converter gas are: CO 86%, CO2 10%, N2 3.5%, O2 0.5%, and smoke content 80g / m 3 ~150g / m3 The pretreatment process of the converter gas includes but is not limited to heat exchange, dust removal, desulfurization, dehydration, denitrification and other operations, so that the waste heat in the converter gas can be recovered and the converter gas can be purified at the same time.

[0042] like Figure 1 As shown, in the top gas pretreatment step, the top gas generated by the vertical furnace 20 is treated. The top gas is mainly composed of carbon dioxide, hydrogen and carbon monoxide, and a small amount of water. The CO2 content is relatively high. The temperature of the top gas is about 450°C, and the dust content is about 10g / Nm 3 ~16g / Nm 3 Although the temperature of the top gas is not high, its flow rate is large, usually reaching 1500m 3 The pretreatment process of the top gas includes, but is not limited to, heat exchange, dust removal, desulfurization, dehydration, denitrification, and other operations, so that the waste heat in the top gas is recovered and the top gas is purified.

[0043] The coal gas pretreatment step and the top gas pretreatment step are performed simultaneously, that is, the converter gas and the top gas are pretreated simultaneously to obtain the treated converter gas and the top gas.

[0044] like Figure 1 As shown, in the catalytic reforming step, a reformer 30 is provided. The treated converter gas produced in the gas pretreatment step and the treated top gas produced in the top gas pretreatment step are introduced into the reformer 30. Natural gas is introduced into the reformer 30, using methane in the natural gas as the primary reactant. Carbon dioxide and oxygen are also added to the reformer 30. Within the reformer 30, a catalytic reforming reaction occurs in the mixture of the treated converter gas, the top gas, the natural gas, oxygen, and carbon dioxide. The reforming method is dry reforming, where CH4 reacts with CO2 to produce CO and H2. The catalyst used is a nickel-based catalyst or an iron-based catalyst. After reforming in the reformer 30, a reducing gas primarily composed of CO is generated. This reducing gas is then introduced into the shaft furnace 20 for the smelting of direct reduced iron.

[0045] The structure and technical effects of a preferred embodiment of the method for preparing gas-based shaft furnace reducing gas from converter gas according to the present invention will be further described below.

[0046] According to one embodiment of the present invention, Figure 1As shown, the pretreatment process of the converter gas includes cooling, impurity removal and preheating in sequence; the pretreatment process of the top gas includes cooling, impurity removal and preheating in sequence; wherein, the cooling treatment of the converter gas and the preheating treatment of the top gas are achieved through convection heat exchange between the two; the preheating treatment of the converter gas and the cooling treatment of the top gas are also achieved through convection heat exchange between the two.

[0047] Performing heat exchange between the high-temperature converter gas before pretreatment and the low-temperature top gas after impurity removal not only lowers the converter gas temperature, facilitating subsequent converter gas impurity removal, but also increases the temperature of the top gas input to the reforming furnace 30, allowing for sufficient preheating of the top gas and reducing energy consumption in the reforming furnace 30. Performing heat exchange between the high-temperature converter gas before pretreatment and the low-temperature converter gas after impurity removal not only lowers the top gas temperature, facilitating subsequent converter gas impurity removal, but also increases the temperature of the converter gas input to the reforming furnace 30, allowing for sufficient preheating of the converter gas and reducing energy consumption in the reforming furnace 30. Heat exchange between the converter gas and the top gas can be achieved using a heat exchanger.

[0048] Specifically, such as Figure 1 As shown, the flue gas LDG_1 (untreated converter gas, the composition and temperature of which have been described above) generated at the outlet of the converter 10 is first heat exchanged with the flue gas SFG_5 (top gas after impurity removal) through a heat exchanger to produce flue gas LDG_2; compared with the flue gas LDG_1, the composition of the flue gas LDG_2 is basically unchanged, and the temperature is reduced to 750℃~850℃. The flue gas LDG_2 is then subjected to a dust removal operation to remove dust and other particulate impurities in the flue gas. A dry bag dust removal process can be used, which has the characteristics of low water resource consumption and high waste heat recovery efficiency; after dust removal, flue gas LDG_3 is produced. Compared with the flue gas LDG_2, the temperature of the flue gas LDG_3 is reduced to 70℃~80℃, the composition is basically unchanged, and the dust content is reduced to 20mg / m 3Because the total iron content in the dust ash is relatively high, about 60%, it can be subsequently cold-pressed and pelletized to produce dust ash balls for smelting in the converter 10, thereby realizing the recycling of the iron element in the dust ash. The flue gas LDG_3 is then desulfurized to remove sulfur-containing impurities (SO2) in the flue gas. Desulfurization can be achieved using stone slurry (CaCO3) or calcium hydroxide slurry (Ca(OH)2), which reacts with sulfides to form gypsum (CaSO4·2H2O), which can be used in building materials or cement production. After desulfurization, flue gas LDG_4 is generated. The CO and CO2 contents in the flue gas LDG_4 are relatively high, with a CO content of 90% and a CO2 content of 10%. The CO therein can react with oxygen to release energy, providing energy for the reaction in the reforming furnace 30. The CO2 therein can be used as a reaction raw material in the reforming furnace 30 to replenish the CO2 in the reforming furnace 30. Flue gas LDG_4 is then exchanged with flue gas SFG_1 (untreated top gas, whose composition and temperature are described above) at the outlet of shaft furnace 20 through a heat exchanger to produce flue gas LDG_5 / LDG_6. Compared to flue gas LDG_4, flue gas LDG_5 / LDG_6 has no change in composition, but its temperature has increased to approximately 150°C. Flue gas LDG_5 / LDG_6 is then introduced into reformer 30 for catalytic reforming. The relatively high temperature of flue gas LDG_5 / LDG_6 reduces energy consumption in reformer 30 and improves reaction efficiency.

[0049] Specifically, such as Figure 1 As shown, the flue gas SFG_1 (untreated top gas, the composition and temperature of which have been described above) generated at the outlet of the vertical furnace 20 is first heat exchanged with the flue gas LDG_4 (converter gas after impurity removal) through a heat exchanger to produce flue gas SFG_2. Compared with the flue gas SFG_1, the temperature of the flue gas SFG_2 drops to about 200°C, and the composition is basically unchanged. The flue gas SFG_2 is then subjected to a dust removal operation to remove dust and other particulate impurities in the flue gas. A dry bag dust removal process can be used, which has the characteristics of low water resource consumption and high waste heat recovery efficiency. After dust removal, flue gas SFG_3 is produced. Compared with the flue gas SFG_2, the temperature of the flue gas SFG_3 drops to 50°C to 60°C, the composition is basically unchanged, and the dust content is reduced to 20mg / m 3. The flue gas SFG_3 is then desulfurized to remove sulfur-containing impurities (SO2) from the flue gas. Desulfurization can be achieved using stone slurry (CaCO3) or calcium hydroxide slurry (Ca(OH)2), which reacts with sulfides to produce gypsum (CaSO4·2H2O), which can be used in building materials or cement production. After desulfurization, flue gas SFG_4 is produced. The flue gas SFG_4 is then dehydrated to produce flue gas SFG_5. The main component of the flue gas at this time is CO2, accounting for approximately 80%, which can be used as a supplement to the high-temperature CO2 of the feed gas of the reformer 30. The flue gas SFG_5 is then heat exchanged with the flue gas LDG_1 (untreated converter gas, the composition and temperature of which have been described above) produced at the outlet of the converter 10 through a heat exchanger to produce flue gas SFG_6. Compared with the flue gas SFG_5, the composition of the flue gas SFG_6 has basically not changed, and the temperature has increased to approximately 150°C. The flue gas SFG_6 is then introduced into the reforming furnace 30 for catalytic reforming reaction. The flue gas SFG_6 with a relatively high temperature can reduce the energy consumption of the reforming furnace 30 and improve the reaction efficiency therein.

[0050] Specifically, such as Figure 1 As shown, in the reformer 30, oxygen reacts with CO in the flue gas LDG_5 / LDG_6 to provide energy for the reformer 30 reaction. The CO2 in the flue gas LDG_5 / LDG_6 serves as a supplementary gas to provide CO2, and the flue gas SFG_6 provides high-temperature CO2. Under the action of the high-temperature environment and the catalyst, CH4 reacts with CO2 to generate CO and H2, thereby generating reducing gas in the reformer 30. The temperature of the generated reducing gas is about 850℃~930℃, the pressure is 0.1Mpa~0.3Mpa, and the flow rate is 1800m 3 / t, which can be directly input into the vertical furnace 20 for direct reduction ironmaking reaction.

[0051] According to one embodiment of the present invention, Figure 1 As shown, the converter gas after impurity removal is divided into two parts, and the top gas flowing out of the outlet of the vertical furnace 20 is also divided into two parts. The two parts of converter gas are subjected to convection heat exchange with the two parts of top gas respectively to achieve preheating of the converter gas and cooling of the top gas; after being preheated, the two parts of converter gas are respectively introduced into the reforming furnace 30 as combustion gas and feed gas. After heat exchange and cooling, the two parts of top gas are merged for impurity removal.

[0052] The flue gas LDG_4 after impurity removal is divided into two parts and respectively undergoes heat exchange treatment with the top gas (flue gas SFG_1), and is respectively introduced into the reforming furnace 30. The flue gas LDG_5 generated after heat exchange serves as fuel gas, which can be understood as the coal gas used in daily life. The CO in it can react with oxygen to release energy, providing energy for the reaction of the reforming furnace 30, while the flue gas LDG_6 serves as raw gas, that is, the CO2 in it is needed as the raw material (reactant) of the reforming furnace 30 to achieve CO2 replenishment.

[0053] According to one embodiment of the present invention, Figure 1 As shown, the converter gas flowing out of the outlet of the converter 10 is divided into two parts, one part of the converter gas is subjected to convection heat exchange with the top gas after impurity removal to achieve cooling of this part of the converter gas and preheating of the top gas, and the other part of the converter gas is subjected to convection heat exchange with natural gas to achieve cooling of this part of the converter gas and preheating of the natural gas before it is introduced into the reforming furnace 30; the two parts of converter gas are merged after heat exchange and cooling for impurity removal.

[0054] The flue gas LDG_1 at the outlet of the converter 10 is divided into two parts and respectively exchanges heat with the flue gas SFG_5 after impurities are removed and the natural gas, so as to preheat the flue gas SFG_5 and the natural gas to be introduced into the reforming furnace 30. The natural gas is heated to about 200°C. The natural gas with a relatively high temperature is introduced into the reforming furnace 30, which reduces the temperature rise process of the natural gas in the reforming furnace 30, can reduce the energy consumption of the reforming furnace 30, and improve the reaction efficiency therein.

[0055] According to one embodiment of the present invention, Figure 1 As shown, the preheated top gas (flue gas SFG_6) is mixed with carbon dioxide and then introduced into the reforming furnace 30.

[0056] Implementation method 2:

[0057] like Figure 1 As shown, the present invention also provides a system for preparing gas-based shaft furnace reducing gas from converter gas, which includes a converter gas treatment unit, a top gas treatment unit, and a reducing gas preparation unit. The converter gas treatment unit includes a converter 10, a first heat exchanger 11, a first impurity removal device, and a second heat exchanger 12, which are sequentially connected by pipelines. The top gas treatment unit includes a shaft furnace 20, a second heat exchanger 12, a second impurity removal device, and the first heat exchanger 11, which are sequentially connected by pipelines. The reducing gas preparation unit includes a carbon dioxide supply device 31, an oxygen supply device 32, a natural gas supply device 33, and a reforming furnace 30. The carbon dioxide supply device 31, the oxygen supply device 32, the natural gas supply device 33, the outlet of the second heat exchanger 12 in the converter gas treatment unit, and the outlet of the first heat exchanger 11 in the top gas treatment unit are all connected to the reforming furnace 30 via pipelines, and the outlet of the reforming furnace 30 is connected to the inlet of the shaft furnace 20.

[0058] The device for preparing gas-based shaft furnace reducing gas from converter gas of the present invention recovers waste heat from the converter gas through a converter gas treatment unit and recovers waste heat from the top gas through a top gas treatment unit. Simultaneously, the reducing capacity of the converter gas is utilized to catalytically reform converter gas and top gas into reducing gas in a reforming furnace 30, thereby reducing the cost of preparing gas-based shaft furnace reducing gas, achieving efficient resource utilization, and having significant economic and environmental benefits.

[0059] The specific structures of the various parts of the device for preparing gas-based shaft furnace reducing gas from converter gas according to the present invention, as well as the pipeline connection relationship between the various parts, will be described in detail below.

[0060] like Figure 1 As shown, in the converter gas processing unit, the outlet of converter 10 is connected to a first dust collector 15 via a converter gas inlet pipe 17. Converter gas inlet pipe 17 is equipped with a first heat exchanger 11. Flue gas LDG_1 flowing through first heat exchanger 11 undergoes heat exchange to produce flue gas LDG_2 with a reduced temperature. Flue gas LDG_2 then passes through first dust collector 15 to remove dust, producing flue gas LDG_3 with a reduced dust content. First dust collector 15 is connected to a first desulfurizer 16 via a pipeline. Flue gas LDG_3, after passing through first desulfurizer 16, produces flue gas LDG_4 with a reduced sulfur content. The first desulfurizer 16 is connected to the reforming furnace 30 via a converter gas outlet pipe 18. A second heat exchanger 12 is installed on the converter gas outlet pipe 18. Flue gas LDG_4 flowing from the second heat exchanger 12 undergoes heat exchange to produce elevated flue gas LDG_5 / LDG_6, which then flows into the reforming furnace 30. The first dust collector 15 can use a dry bag filter process to remove dust from the flue gas, while the first desulfurizer 16 can use a stone slurry (CaCO3) or a calcium hydroxide slurry (Ca(OH)2) to desulfurize the flue gas. The first dust collector 15 and the first desulfurizer 16 together form a first impurity removal device.

[0061] like Figure 1As shown, in the top gas processing unit, the outlet of the vertical furnace 20 is connected to the second dust collector 21 via a top gas inlet pipe 24. The second heat exchanger 12, described above, is installed on the top gas inlet pipe 24. Specifically, the second heat exchanger 12 is connected between the converter gas outlet pipe 18 and the top gas inlet pipe 24, enabling heat exchange between the gases in the two pipes. Flue gas SFG_1 flowing through the second heat exchanger 12 undergoes heat exchange to produce flue gas SFG_2 with a reduced temperature. After dust removal by the second dust collector 21, the flue gas SFG_2 produces flue gas SFG_3 with a reduced dust content. The second dust collector 21 is connected to a second desulfurizer 22 via a pipe. After passing through the second desulfurizer 22, the flue gas SFG_3 produces flue gas SFG_4 with a reduced sulfur content. The second desulfurizer 22 is also connected to a dehydrator 23 via a pipe. After passing through the dehydrator 23, the flue gas SFG_4 produces flue gas SFG_5 with a reduced moisture content. The dehydrator 23 is connected to the reforming furnace 30 through the top gas outlet pipe 25. The top gas outlet pipe 25 is provided with the first heat exchanger 11 mentioned above, that is, the first heat exchanger 11 is connected between the converter gas inlet pipe 17 and the top gas outlet pipe 25, and is used to realize heat exchange of gases in the two pipelines. The flue gas SFG_5 on the front side of the first heat exchanger 11 produces flue gas SFG_6 with increased temperature after heat exchange, and the flue gas SFG_6 flows into the reforming furnace 30. The second dust collector 21 can use a dry bag dust removal process to remove dust from the flue gas, and the second desulfurizer 22 can use stone slurry (CaCO3) or calcium hydroxide slurry (Ca(OH)2) to desulfurize the flue gas; the second dust collector 21, the second desulfurizer 22 and the dehydrator 23 are combined to form a second impurity removal device. Figure 1 In order to simplify the structure, the first dust collector 15 and the second dust collector 21 are combined, and the first desulfurizer 16 and the second desulfurizer 22 are combined; those skilled in the art should understand that as long as the dust removal and desulfurization operations of the flue gas in the two pipelines can be achieved separately, there is no need to divide the dust collectors and desulfurizers in terms of quantity.

[0062] like Figure 1As shown, in the reducing gas preparation unit, an oxygen supply device 32 is connected to the reformer 30 via a pipeline for supplying oxygen into the reformer 30. A carbon dioxide supply device 31 is connected to the reformer 30 via a carbon dioxide supply pipe 35 for supplying carbon dioxide into the reformer 30. Furthermore, the outlet of the top gas outlet pipe 25 is connected to the carbon dioxide supply pipe 35. Pretreated flue gas SFG_6 in the top gas outlet pipe 25 is mixed with CO2 in the carbon dioxide supply pipe 35 and then passed into the reformer 30. A natural gas supply device 33 is connected to the reformer 30 via a natural gas supply pipe 34 for supplying methane into the reformer 30. Within reformer 30, oxygen reacts with CO in the flue gases LDG_5 / LDG_6, providing energy for the reformer 30 reaction. CO2 in the flue gases LDG_5 / LDG_6 serves as supplemental gas to provide CO2, while flue gas SFG_6 provides high-temperature CO2. Under the influence of the high temperature and catalyst, CH4 and CO2 react to produce CO and H2, generating reducing gas within reformer 30. Reformer 30 is connected to shaft furnace 20 via a pipeline, allowing the reducing gas to flow to shaft furnace 20 for the smelting of direct reduced iron.

[0063] According to one embodiment of the present invention, Figure 1 As shown, the outlet of the first impurity removal device is connected to two converter gas outlet pipes 18 arranged in parallel, on which the second heat exchanger 12 and the third heat exchanger 13 are respectively provided, and the outlets of the two converter gas outlet pipes 18 are both connected to the reforming furnace 30; the outlet of the vertical furnace 20 is connected to two top gas inlet pipes 24 arranged in parallel, on which the second heat exchanger 12 and the third heat exchanger 13 are respectively provided, and the outlets of the two top gas inlet pipes 24 are connected after converging to the second impurity removal device.

[0064] Specifically, at the second heat exchanger 12, the flue gas LDG_4 in the converter gas outlet pipe 18 undergoes heat exchange to produce flue gas LDG_6 at an elevated temperature, while the flue gas SFG_1 in the top gas inlet pipe 24 undergoes heat exchange to produce flue gas SFG_2 at a lowered temperature. At the third heat exchanger 13, the flue gas LDG_4 in the converter gas outlet pipe 18 undergoes heat exchange to produce flue gas LDG_5 at an elevated temperature, while the flue gas SFG_1 in the top gas inlet pipe 24 undergoes heat exchange to produce flue gas SFG_2 at a lowered temperature.

[0065] The flue gas LDG_4 after impurity removal is divided into two parts and respectively undergoes heat exchange treatment with the furnace top gas (flue gas SFG_1), and is respectively introduced into the reforming furnace 30. The flue gas LDG_5 after heat exchange and temperature increase is used as fuel gas, and the CO in it can react with oxygen to release energy, providing energy for the reaction of the reforming furnace 30, while the flue gas LDG_6 is used as raw gas, that is, the CO2 in it is needed as the raw material (reactant) of the reforming furnace 30 to achieve CO2 replenishment.

[0066] According to one embodiment of the present invention, Figure 1 As shown, the outlet of the converter 10 is connected to two converter gas inlet pipes 17 arranged in parallel, and the two converter gas inlet pipes 17 are respectively provided with a first heat exchanger 11 and a fourth heat exchanger 14. The two converter gas inlet pipes 17 are connected to the first impurity removal device after being converged; the outlet of the second impurity removal device is connected to a furnace top gas outlet pipe 25, the first heat exchanger 11 is provided on the furnace top gas outlet pipe 25, a natural gas supply pipe 34 is connected between the natural gas supply device 33 and the reforming furnace 30, and the fourth heat exchanger 14 is provided on the natural gas supply pipe 34.

[0067] Specifically, at the first heat exchanger 11, the flue gas LDG_1 in the converter gas outlet pipe 18 undergoes heat exchange to produce flue gas LDG_2 at a lower temperature, and the flue gas SFG_5 in the top gas outlet pipe 25 undergoes heat exchange to produce flue gas SFG_6 at a higher temperature. At the fourth heat exchanger 14, the flue gas LDG_1 in the converter gas outlet pipe 18 undergoes heat exchange to produce flue gas LDG_2 at a lower temperature, and the natural gas in the natural gas supply pipe 34 undergoes heat exchange to produce natural gas at a higher temperature. The relatively high-temperature natural gas is introduced into the reformer 30, reducing the natural gas's temperature rise within the reformer 30, thereby lowering the reformer 30's energy consumption and improving its reaction efficiency.

[0068] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing gas-based shaft furnace reducing gas from converter gas, characterized in that: The following steps are involved: Pre-treating the converter gas generated by the converter (10) and the top gas generated by the shaft furnace (20) to recover waste heat in the gas and remove impurities in the gas; The pre-treated converter gas, the pre-treated top gas, carbon dioxide, oxygen and natural gas are introduced into a reforming furnace (30) for catalytic reforming to generate reducing gas; The reducing gas is introduced into the vertical furnace (20) for smelting direct reduced iron.

2. The method for preparing gas-based shaft furnace reducing gas from converter gas according to claim 1, characterized in that: The pretreatment process of the converter gas includes cooling, impurity removal and preheating in sequence; the pretreatment process of the top gas includes cooling, impurity removal and preheating in sequence; The cooling treatment of the converter gas and the preheating treatment of the top gas are achieved through convection heat exchange between the two; the preheating treatment of the converter gas and the cooling treatment of the top gas are also achieved through convection heat exchange between the two.

3. The method for preparing gas-based shaft furnace reducing gas from converter gas according to claim 2, characterized in that: The impurity removal process of the converter gas includes dust removal and desulfurization performed in sequence; the impurity removal process of the top gas includes dust removal, desulfurization and dehydration performed in sequence.

4. The method for preparing gas-based shaft furnace reducing gas from converter gas according to claim 2, characterized in that: The converter gas after impurity removal is divided into two parts, and the top gas flowing out of the outlet of the vertical furnace (20) is also divided into two parts. The two parts of the converter gas are respectively subjected to convection heat exchange with the two parts of the top gas to achieve preheating of the converter gas and cooling of the top gas; after being preheated, the two parts of the converter gas are respectively introduced into the reforming furnace (30) as combustion gas and raw gas, and the two parts of the top gas are combined after heat exchange and cooling for impurity removal.

5. The method for preparing gas-based shaft furnace reducing gas from converter gas according to claim 2 or 4, characterized in that: The converter gas flowing out of the converter (10) outlet is divided into two parts, one part of the converter gas is subjected to convection heat exchange with the top gas after impurity removal to achieve cooling of the converter gas and preheating of the top gas, and the other part of the converter gas is subjected to convection heat exchange with the natural gas to achieve cooling of the converter gas and preheating of the natural gas before it is introduced into the reforming furnace (30); the two parts of the converter gas are combined after heat exchange and cooling to perform impurity removal.

6. The method for preparing gas-based shaft furnace reducing gas from converter gas according to claim 2, characterized in that: The preheated top gas is mixed with the carbon dioxide and then introduced into the reforming furnace (30).

7. A system for preparing gas-based shaft furnace reducing gas from converter gas, characterized in that: include: A converter gas processing unit, comprising a converter (10), a first heat exchanger (11), a first impurity removal device, and a second heat exchanger (12) connected in sequence via pipelines; A top gas processing unit, comprising a vertical furnace (20), the second heat exchanger (12), a second impurity removal device and the first heat exchanger (11) connected in sequence via a pipeline; A reducing gas preparation unit, the reducing gas preparation unit comprising a carbon dioxide supply device (31), an oxygen supply device (32), a natural gas supply device (33) and a reforming furnace (30), wherein the carbon dioxide supply device (31), the oxygen supply device (32), the natural gas supply device (33), the outlet of the second heat exchanger (12) in the converter gas treatment unit, and the outlet of the first heat exchanger (11) in the top gas treatment unit are all connected to the reforming furnace (30) through pipelines, and the outlet of the reforming furnace (30) is connected to the inlet of the vertical furnace (20).

8. The system for preparing gas-based shaft furnace reducing gas from converter gas according to claim 7, characterized in that: The outlet of the first impurity removal device is connected to two converter gas outlet pipes (18) arranged in parallel, the second heat exchanger (12) and the third heat exchanger (13) are respectively provided on the two converter gas outlet pipes (18), and the outlets of the two converter gas outlet pipes (18) are both connected to the reforming furnace (30); the outlet of the vertical furnace (20) is connected to two top gas inlet pipes (24) arranged in parallel, the second heat exchanger (12) and the third heat exchanger (13) are respectively provided on the two top gas inlet pipes (24), and the outlets of the two top gas inlet pipes (24) are connected to the second impurity removal device after converging.

9. The system for preparing gas-based shaft furnace reducing gas from converter gas according to claim 7, characterized in that: The outlet of the converter (10) is connected to two converter gas inlet pipes (17) arranged in parallel, and the two converter gas inlet pipes (17) are respectively provided with the first heat exchanger (11) and the fourth heat exchanger (14). The two converter gas inlet pipes (17) are connected to the first impurity removal device after being converged; the outlet of the second impurity removal device is connected to a top gas outlet pipe (25), and the first heat exchanger (11) is provided on the top gas outlet pipe (25). A natural gas supply pipe (34) is connected between the natural gas supply device (33) and the reforming furnace (30), and the fourth heat exchanger (14) is provided on the natural gas supply pipe (34).

10. The system for preparing gas-based shaft furnace reducing gas from converter gas according to claim 7, characterized in that: The first impurity removal device comprises a first dust collector (15) and a first desulfurizer (16) connected in sequence through a pipeline; and / or, The second impurity removal device comprises a second dust collector (21), a second desulfurizer (22) and a dehydrator (23) which are sequentially connected via pipelines.

Images