Method and system for recovering waste heat of hydrogen-based shaft furnace process

Abstract

The invention relates to a hydrogen-based shaft furnace process waste heat recovery method and system in the technical field of hydrogen-based shaft furnace direct reduction. The method comprises the following steps: heating total natural gas to obtain second natural gas and high-temperature carburizing gas; the second natural gas and oxygen are converted to obtain first reducing gas; the first nitrogen is heated and then exchanges heat with the cold-state pellets to obtain hot-state pellets; adding the hot pellets, first reducing gas and high-temperature carburizing gas into a hydrogen-based shaft furnace to obtain hot sponge iron and top gas; the top gas is sequentially subjected to dust removal, heat exchange, washing, pressurization and decarburization to obtain first decarburized gas and second decarburized gas; heating the first decarburization furnace to obtain second reducing gas which is sprayed back to the hydrogen-based shaft furnace; and the hot sponge iron is conveyed to the buffer tank through second nitrogen, and then is subjected to dust removal, heat exchange, washing and pressurization in sequence, and then the hot sponge iron is cyclically conveyed. The sensible heat of the top gas and the thermal sponge iron is fully recovered, and the problem of sensible heat waste of the hydrogen-based shaft furnace is solved, so that the process energy consumption and CO2 emission can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen-based shaft furnace direct reduction, and in particular to a method and system for recovering waste heat from a hydrogen-based shaft furnace process. Background Art

[0002] The main processes for producing sponge iron by direct reduction in existing hydrogen-based vertical furnaces are the MIDREX process and the HYL-ZR process. Top gas is generated during the reduction process of sponge iron. The top gas contains a large amount of sensible heat. If this heat can be fully utilized, it will help significantly reduce the energy consumption and carbon emissions of the hydrogen-based vertical furnace process.

[0003] Currently, the top gas temperature produced by the MIDREX process is approximately 411°C. After wet dust removal, the top gas temperature is reduced to 50°C, wasting a significant amount of sensible heat and generating a large amount of sludge that requires treatment, which increases the burden on the water system. The top gas temperature produced by the HYL-ZR process is approximately 500°C. After heat exchange, the top gas is fed into the decarbonization system by steam generated by the waste heat boiler. After heat exchange, the top gas temperature is reduced to 195°C before entering the quenching orifice plate for water spray scrubbing. However, some sensible heat is not fully utilized.

[0004] In addition, the hot sponge iron in the hydrogen-based vertical furnace needs to be transported to the electric furnace through nitrogen. Inevitably, the temperature of the nitrogen used to transport the hot sponge iron will rise from room temperature to about 400°C during the transportation process. The HYL-ZR process uses a quenching orifice plate to spray water for cooling the nitrogen used for transportation, wasting a lot of sensible heat.

[0005] Therefore, how to recover the sensible heat of top gas and nitrogen used to transport hot sponge iron to reduce the energy consumption and CO2 emissions of the hydrogen-based vertical furnace process has become a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method and system for recovering waste heat from a hydrogen-based shaft furnace process, so as to address the problem of low sensible heat recovery efficiency of top gas and nitrogen used to transport hot sponge iron in the prior art, thereby reducing energy consumption and CO2 emissions in the hydrogen-based shaft furnace process.

[0007] To achieve the above-mentioned and other related objectives, the present invention provides a method for recovering waste heat from a hydrogen-based shaft furnace process, comprising:

[0008] passing the total natural gas through a first heat exchanger to heat up the temperature to obtain a first natural gas and a second natural gas, wherein the first natural gas is formed into a high-temperature carburized gas;

[0009] Converting the second natural gas and the oxygen heated by the second heat exchanger in a converter to obtain a first reducing gas;

[0010] The first nitrogen is sequentially passed through the third heat exchanger for primary heat exchange and the fourth heat exchanger for secondary heat exchange, and then heat-exchanged with the cold pellets to obtain hot pellets;

[0011] adding the hot pellets, the first reducing gas and the high-temperature carburizing gas into a hydrogen-based shaft furnace, and subjecting the hot pellets to reduction and carburizing treatment in the hydrogen-based shaft furnace to obtain hot sponge iron and top gas;

[0012] The top coal gas is sequentially subjected to dust removal by a first dry dust collector, primary heat exchange and cooling by a fifth heat exchanger, secondary heat exchange and cooling by the first heat exchanger, tertiary heat exchange and cooling by the third heat exchanger, washing by a first washing tower, pressurizing by a first compressor, and decarbonization by a decarbonization system to obtain a total decarbonized gas, a portion of which is formed into a first decarbonized gas, and the other portion is formed into a second decarbonized gas;

[0013] The first decarbonized gas is sequentially passed through the fifth heat exchanger for heat exchange and heated in the heating furnace to obtain the second reducing gas which is sprayed back into the hydrogen-based vertical furnace; the second decarbonized gas is burned to heat the heating furnace;

[0014] The hot sponge iron is transported to an intermediate tank, and the hot sponge iron in the intermediate tank is transported to a buffer tank connected to an electric furnace through a second nitrogen gas. The second nitrogen gas is discharged from the buffer tank and sequentially passes through a second dry dust collector for dust removal, a fourth heat exchanger for primary heat exchange and cooling, a second heat exchanger for secondary heat exchange and cooling, a second washing tower for washing, and a second pressurizer for pressurizing, and then circulates the hot sponge iron in the intermediate tank.

[0015] Optionally, the hot pellets are fed from above, the hot sponge iron is discharged from below, and the first reducing gas and the second reducing gas are fed from the middle and discharged from above.

[0016] Optionally, the first reducing gas and the second reducing gas are mixed to form a total reducing gas and introduced into the hydrogen-based vertical furnace;

[0017] The total reducing gas consists of CO, H2, N2, CO2, H2O and CH4, the content of CO and H2 is greater than or equal to 80% of the total reducing gas, the content of N2, CO2 and H2O is less than or equal to 10% of the total reducing gas, and the content of CH4 is less than or equal to 10% of the total reducing gas;

[0018] And / or, the temperature of the total reducing gas is 850° C. to 1050° C., and the pressure of the total reducing gas is 0.25 MPa to 0.55 MPa.

[0019] Optionally, the metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 650° C. to 800° C.;

[0020] And / or, the temperature of the hot pellets is 100°C to 117°C, the gas volume of the first nitrogen is 300Nm 3 / tDRI~700Nm 3 / tDRI;

[0021] And / or, the temperature of the top gas is 395° C. to 455° C., and the pressure of the top gas is 0.15 MPa to 0.45 MPa.

[0022] Optionally, the dust content of the second nitrogen after dust removal by the second dry dust collector is 8 mg / Nm 3 ~12mg / Nm 3 After the second nitrogen is washed by the second washing tower, the temperature is reduced to 35°C to 45°C, and after the second nitrogen is pressurized by the second compressor, the pressure is 0.25MPa to 0.55MPa;

[0023] and / or, the molar ratio of the first decarbonized gas to the second decarbonized gas is 10.9 to 18.7; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger, and the first decarbonized gas and the top gas exchange heat in the fifth heat exchanger until the temperature of the top gas decreases by 153° C. to 150° C. and the temperature of the first decarbonized gas increases by 270° C. to 329° C.;

[0024] and / or, before the total natural gas and the top gas pass through the first heat exchanger for heat exchange, the temperature of the total natural gas is 20° C. to 30° C., which is lower than the temperature of the top gas passing through the first heat exchanger, and the total natural gas and the top gas exchange heat in the first heat exchanger until the temperature of the top gas decreases by 23° C. to 37° C. and the temperature of the total natural gas increases to 151° C. to 209° C.;

[0025] and / or, before the first nitrogen and the top gas pass through the third heat exchanger for heat exchange, the temperature of the first nitrogen is 35° C. to 45° C., which is lower than the temperature of the top gas passing through the third heat exchanger, and the first nitrogen exchanges heat with the top gas in the third heat exchanger until the temperature of the top gas decreases by 8° C. to 30° C. and the temperature of the first nitrogen increases to 104° C. to 150° C.;

[0026] and / or, before the second nitrogen gas and the first nitrogen gas pass through the fourth heat exchanger for heat exchange, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger, and the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger until the temperature of the second nitrogen gas decreases by 244° C. to 160° C. and the temperature of the first nitrogen gas increases to 176° C. to 260° C.;

[0027] and / or, before the cold pellets are heat-exchanged with the first nitrogen, the temperature of the cold pellets is 20° C. to 30° C., which is lower than the temperature of the first nitrogen; after the cold pellets are heat-exchanged with the first nitrogen, the temperature of the first nitrogen is reduced to 102° C. to 120° C., and the temperature of the cold pellets is increased to 100° C. to 117° C.;

[0028] And / or, before the oxygen and the second nitrogen pass through the second heat exchanger for heat exchange, the temperature of the oxygen is 35° C. to 45° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger, and the oxygen and the second nitrogen exchange heat in the second heat exchanger until the temperature of the second nitrogen decreases by 59° C. to 96° C. and the temperature of the oxygen increases to 117° C. to 164° C.

[0029] Optionally, the cold pellets are transported to the hydrogen-based vertical furnace via a vertical belt conveyor, and the cold pellets exchange heat with the first nitrogen on the vertical belt conveyor; the vertical belt conveyor has multiple gas introduction points for inputting the first nitrogen, and the multiple gas introduction points are distributed along the conveying direction of the cold pellets, and the amount of the first nitrogen input to the gas introduction points close to the hydrogen-based vertical furnace is less than the amount of the first nitrogen input to the gas introduction points far from the hydrogen-based vertical furnace.

[0030] Optionally, the number of the gas introduction positions is 8 to 10, and the amount of the first nitrogen gas input from the gas introduction position far from the hydrogen-based vertical furnace to the gas introduction position close to the hydrogen-based vertical furnace decreases by 20%.

[0031] To achieve the above-mentioned and other related objectives, the present invention further provides a system for recovering waste heat from a hydrogen-based shaft furnace process, comprising:

[0032] A vertical belt conveyor is used to convey cold pellets, where the cold pellets are heat-exchanged with the first nitrogen to obtain hot pellets;

[0033] Hydrogen-based shaft furnace for hot pellet reduction and carburizing to obtain hot sponge iron and top gas;

[0034] a tundish connected to the hydrogen-based vertical furnace and receiving the hot sponge iron discharged from the hydrogen-based vertical furnace;

[0035] a buffer tank connected to the intermediate tank and receiving the hot sponge iron discharged from the intermediate tank;

[0036] an electric furnace connected to the buffer tank and receiving the hot sponge iron discharged from the buffer tank;

[0037] Heating furnace, used for heating;

[0038] a top gas recovery unit, the top gas recovery unit comprising a first dry dust collector, a fifth heat exchanger, a first heat exchanger, a third heat exchanger, a first scrubber, a first compressor, and a decarbonization system connected in sequence, the first dry dust collector being connected to the hydrogen-based vertical furnace, and an output end of the decarbonization system being connected to the fifth heat exchanger and the heating furnace, respectively;

[0039] a reformer connected to the hydrogen-based vertical furnace, for performing a second natural gas and oxygen reforming process to obtain a first reducing gas fed into the hydrogen-based vertical furnace;

[0040] A nitrogen recovery unit includes a second dry dust collector, a fourth heat exchanger, a second heat exchanger, a second washing tower, and a second compressor connected in sequence. The second dry dust collector and the second compressor are respectively connected to the buffer tank to form a nitrogen circulation loop. The first pipe section connecting the second compressor and the buffer tank is also connected to the intermediate tank to transport the hot sponge iron. The fourth heat exchanger is connected to the second pipe section for transporting the first nitrogen. The second heat exchanger is connected to the oxygen pipeline for transporting the oxygen.

[0041] Optionally, a hot pellet inlet and a top gas outlet are provided at the top of the hydrogen-based vertical furnace, the top gas outlet is connected to the first dry dust collector, a reducing gas inlet and a high-temperature carburizing gas inlet are provided in the middle of the hydrogen-based vertical furnace, the converter and the heating furnace are both connected to the reducing gas inlet, the first heat exchanger is connected to the high-temperature carburizing gas inlet, a hot sponge iron outlet is provided at the lower part of the hydrogen-based vertical furnace, and the intermediate tank is connected to the hot sponge iron outlet.

[0042] Optionally, the discharge end of the vertical belt conveyor is close to the end of the hydrogen-based vertical furnace, and the discharge end of the vertical belt conveyor, the hydrogen-based vertical furnace and the intermediate tank are arranged vertically from top to bottom.

[0043] As described above, the method and system for recovering waste heat from a hydrogen-based shaft furnace process of the present invention have at least the following beneficial effects:

[0044] 1) The heat recovery of the high-temperature section of the top gas is realized, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 5.2% to 5.7%;

[0045] 2) The heat recovery of the second nitrogen used to transport hot sponge iron is achieved, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by approximately 0.41% to 0.6%;

[0046] 3) In the first heat exchanger, part of the heat of the top gas is exchanged with the total natural gas. This, on the one hand, increases the temperature of the high-temperature carburizing gas, reduces the temperature drop of the first reducing gas and the second reducing gas, and improves the carburizing effect, thereby increasing the DRI carburizing amount by approximately 0.8% to 1.05%. On the other hand, it increases the temperature of the second natural gas entering the reformer, reducing the second natural gas consumption and oxygen consumption of the reformer by 4.7% to 7.3%.

[0047] 4) The first nitrogen gas passes through the third heat exchanger and the fourth heat exchanger in sequence to absorb part of the heat of the top gas and part of the heat of the second nitrogen gas. The heat absorbed by the first nitrogen gas can be used to preheat the cold pellets to increase the temperature of the cold pellets and reduce the risk of the feed tank sticking and making it difficult to discharge the pellets;

[0048] 5) In the second heat exchanger, part of the heat of the second nitrogen is exchanged with oxygen, which can increase the temperature of the oxygen entering the reformer, thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 1.4% to 2.2%.

[0049] In summary, the present invention fully recycles and utilizes the heat of top gas and hot pellets, solves the problem of sensible heat waste in the hydrogen-based shaft furnace process, and is of great significance for reducing energy consumption and CO2 emissions in the hydrogen-based shaft furnace process. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shown is a simplified structural diagram of an embodiment of a system for recovering waste heat from a hydrogen-based vertical furnace process according to the present invention.

[0051] Part Number Description

[0052] Hydrogen-based vertical furnace 1, hot pellet inlet 11, top gas outlet 12, reducing gas inlet 13, high-temperature carburizing gas inlet 14, hot sponge iron outlet 15, intermediate tank 2, first dry dust collector 31, fifth heat exchanger 32, first heat exchanger 33, main natural gas pipeline 331, first natural gas pipeline 332, second natural gas pipeline 333, third heat exchanger 34, first nitrogen pipeline 341, first pipeline section 3411, second pipeline section 3412, first washing tower 35, first A compressor 36, a decarbonization system 37, a first decarbonization gas pipeline 371, a second decarbonization gas pipeline 372, a desorption gas pipeline 373, a heating furnace 4, a converter 5, a second dry dust collector 61, a fourth heat exchanger 62, a second heat exchanger 63, an oxygen pipeline 631, a second washing tower 64, a second compressor 65, a buffer tank 7, a second nitrogen pipeline 71, an electric furnace 8, a vertical belt conveyor 91, a feed end 911, a discharge end 912, a gas inlet position 913, and a top dust collector 92. DETAILED DESCRIPTION

[0053] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] It should be noted that the diagrams provided in the present embodiment are only schematic illustrations of the basic concept of the present invention. The diagrams only show the components related to the present invention and are not drawn according to the number, shape and size of the components during actual implementation. The type, quantity and ratio of each component during actual implementation can be changed at will, and the component layout type may also be more complex. The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read. They are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they have no technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be considered as the scope of the implementation of the present invention without substantially changing the technical content.

[0055] Before describing the embodiments of the present invention in detail, the application environment of the present invention will be described. The technology of the present invention is primarily applicable to the field of hydrogen-based shaft furnaces, particularly to the reduction of hot pellets in hydrogen-based shaft furnaces. The present invention addresses the problem of low sensible heat recovery efficiency of top gas and hot sponge iron generated during the reduction of hot pellets in hydrogen-based shaft furnaces. The present invention recovers the sensible heat of the top gas and hot sponge iron and utilizes this heat to heat the cold pellets, oxygen, and total natural gas required in the hydrogen-based shaft furnace process, thereby reducing energy consumption and CO2 emissions.

[0056] See also Figure 1In an optional embodiment, the present invention provides a method for recovering waste heat from a hydrogen-based vertical furnace process, comprising: heating total natural gas, subjecting the total natural gas to heat exchange and temperature increase through a first heat exchanger 33 to obtain first natural gas and second natural gas, wherein the first natural gas is formed into high-temperature carburizing gas. The increase in the temperature of the total natural gas is conducive to increasing the temperature of the first natural gas, thereby facilitating an increase in the temperature of the high-temperature carburizing gas entering the hydrogen-based vertical furnace 1, thereby increasing the sensible heat entering the furnace; converting the second natural gas and the oxygen heated by heat exchange through a second heat exchanger 63 in a reformer 5 to obtain a first reducing gas; subjecting the first nitrogen to heat exchange and temperature increase through a third heat exchanger 34, The fourth heat exchanger 62 heats up the pellets twice and exchanges heat with the cold pellets to obtain hot pellets; the hot pellets, the first reducing gas and the high-temperature carburizing gas are added to the hydrogen-based vertical furnace 1, and the hot pellets are reduced and carburized in the hydrogen-based vertical furnace 1 to obtain hot sponge iron and top gas; the top gas is sequentially subjected to the first dry dust collector 31 for dust removal, the fifth heat exchanger 32 for primary heat exchange and cooling, the first heat exchanger 33 for secondary heat exchange and cooling, the third heat exchanger 34 for tertiary heat exchange and cooling, the first washing tower 35 for washing, the first compressor 36 for pressurization and the decarburization system 37 for decarburization to obtain total decarburized gas, a part of which forms the first decarburizing gas. The first decarbonized gas is heated in the fifth heat exchanger 32 and heated in the heating furnace 4 to obtain the second reducing gas that is sprayed back into the hydrogen-based vertical furnace 1, so that the second reducing gas can absorb the heat released by the top coal gas in the fifth heat exchanger 32; the second decarbonized gas is burned to heat the heating furnace 4, that is, the heat obtained by the heating furnace 4 to heat the first decarbonized gas is at least partially derived from the heat obtained by the combustion of the second decarbonized gas; the hot sponge iron is transported to the intermediate tank 2, and the hot sponge iron in the intermediate tank 2 is transported to the buffer tank 7 connected to the electric furnace 8 through the second nitrogen, and the second nitrogen is taken from the buffer The hot sponge iron discharged from the tank 7 passes through the second dry dust collector 61 for dust removal, the fourth heat exchanger 62 for primary heat exchange and cooling, the second heat exchanger 63 for secondary heat exchange and cooling, the second washing tower 64 for washing, and the second pressurizing machine 65 for pressurizing before being circulated to the hot sponge iron in the intermediate tank 2. In other words, the heat absorbed by the second nitrogen from the hot sponge iron can be used to heat the first nitrogen in the fourth heat exchanger 62 and to heat the oxygen in the second heat exchanger 63, thereby realizing the sensible heat recovery of the hot sponge iron. The heated oxygen and the second natural gas are converted in the reformer 5, which is beneficial to reducing the heat required for the conversion of the second natural gas and thus reducing energy consumption.

[0057] In the method for recovering waste heat from the hydrogen-based vertical furnace process of the above embodiment, dry dust removal is adopted for both the top gas and the second nitrogen that has absorbed the heat from the hot sponge iron, so that the top gas and the second nitrogen lose less heat after dust removal, thereby facilitating heat recovery and utilization. Based on this, the top gas is heat-exchanged through the fifth heat exchanger 32, the first heat exchanger 33, and the third heat exchanger 34 to heat the first decarbonized gas, the total natural gas, and the first nitrogen, and the second nitrogen is heat-exchanged through the fourth heat exchanger 62 and the second heat exchanger 63 to heat the first nitrogen and oxygen, thereby fully utilizing the heat transferred from the top gas and the hot sponge iron to the second nitrogen and reducing energy consumption.

[0058] See also Figure 1 In an optional embodiment, the hot pellets are fed from above, the hot sponge iron is discharged from below, and the first and second reducing gases are fed from the center and discharged from above. The pellet flow and the reducing gas flow are in opposite directions, forming a countercurrent flow. This increases the gas-solid contact area, improves reaction efficiency and heat exchange, and increases the metallization rate by 5% to 10%.

[0059] See also Figure 1 In an optional embodiment, the first reducing gas and the second reducing gas are mixed to form a total reducing gas and introduced into the hydrogen-based vertical furnace, thereby making full use of the unused reducing gas in the top gas, thereby reducing the consumption of the second natural gas by 50% to 70%.

[0060] Optionally, the total reducing gas comprises CO, H2, N2, CO2, H2O, and CH4, with the CO and H2 content being greater than or equal to 80% of the total reducing gas, and the N2, CO2, and H2O content being less than or equal to 10% of the total reducing gas. This increases the content of reducing gases in the total reducing gas, reduces the content of oxidizing gases and inert gases, and improves the reducing capacity of the total reducing gas. The CH4 content being less than or equal to 10% of the total reducing gas ensures that the temperature drop of the total reducing gas caused by the in-situ reforming reaction of CH4 with H2O and CO2 under the catalysis of the hot sponge iron is controlled to be within 10%.

[0061] Optionally, the temperature of the total reducing gas is 850°C to 1050°C, and the pressure of the total reducing gas is 0.25 MPa to 0.55 MPa. Furthermore, the temperature of the total reducing gas can be any value among 850°C, 900°C, 950°C, 1000°C, or 1050°C; and the pressure of the total reducing gas can be any value among 0.25 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or 0.55 MPa.

[0062] See also Figure 1 In an optional embodiment, the metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 650°C to 800°C.

[0063] Optionally, the temperature of the hot sponge iron may be any one of 650°C, 700°C, 750°C, 780°C or 800°C.

[0064] See also Figure 1 In an optional embodiment, the temperature of the hot pellets is 100°C to 117°C, and the gas volume of the first nitrogen is 300Nm 3 / tDRI~700Nm 3 / tDRI.

[0065] Optionally, the temperature of the hot pellets can be any value among 100°C, 107°C, 110°C or 117°C, and the gas volume of the first nitrogen can be 300Nm 3 / tDRI, 400Nm 3 / tDRI, 500Nm 3 / tDRI, 600Nm 3 / tDRI or 700Nm 3 / tDRI and other values.

[0066] See also Figure 1 In an optional embodiment, the temperature of the top gas is 395° C. to 455° C., and the pressure of the top gas is 0.15 MPa to 0.45 MPa.

[0067] Optionally, the temperature of the top gas can be any value among 395°C, 415°C, 435°C, 445°C or 455°C; the pressure of the top gas can be any value among 0.15MPa, 0.2MPa, 0.3MPa, 0.4MPa or 0.45MPa.

[0068] See also Figure 1 In an optional embodiment, the dust content of the second nitrogen after the second dry dust collector 61 is 8 mg / Nm 3 ~12mg / Nm 3 , for example, it can be 8mg / Nm 3 , 9mg / Nm 3 、10mg / Nm 3 、11mg / Nm 3 or 12 mg / Nm 3After the second nitrogen passes through the second dry dust collector 61, the temperature is 430°C to 450°C; after the second nitrogen passes through the second washing tower 64, the temperature is reduced to 35°C to 45°C, for example, it can be any value among 35°C, 38°C, 40°C, 42°C or 45°C; after the second nitrogen is pressurized by the second compressor 65, the pressure is 0.25MPa to 0.55MPa, for example, it can be any value among 0.25MPa, 0.3MPa, 0.4MPa, 0.5MPa or 0.55MPa.

[0069] Specifically, in this embodiment, after the second nitrogen passes through the second dry dust collector 61 to remove dust, the dust content is reduced to 10 mg / Nm 3 After the second nitrogen is washed by the second washing tower 64, the temperature is reduced to 40°C. After the second nitrogen is pressurized by the second compressor 65, the pressure is 0.25MPa to 0.55MPa.

[0070] See also Figure 1 In an optional embodiment, the molar ratio of the first decarbonized gas to the second decarbonized gas is 10.9 to 18.7, for example, it can be any value among 10.9, 13.9 or 18.9; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top gas are heat exchanged in the fifth heat exchanger 32 until the temperature of the top gas is reduced by 153°C to 150°C, for example, it can be any value among 153°C, 151°C or 150°C; the temperature of the first decarbonized gas is increased by 270°C to 329°C, for example, it can be any value among 270°C, 300°C, 310°C, 320°C or 329°C.

[0071] Optionally, the temperature of the top gas passing through the fifth heat exchanger is 322℃~379℃, and the temperature of the first decarbonized gas passing through the fifth heat exchanger 32 is 25℃~35℃. After the first decarbonized gas and the top gas complete heat exchange in the fifth heat exchanger, the temperature of the top gas is 171℃~229℃, and the temperature of the first decarbonized gas is 302℃~359℃.

[0072] See also Figure 1In an optional embodiment, before the total natural gas and top gas pass through the first heat exchanger 33 for heat exchange, the total natural gas has a temperature of 20°C to 30°C, for example, 20°C, 22°C, 25°C, 28°C, or 30°C. The total natural gas has a lower temperature than the top gas passing through the first heat exchanger 33, and heat exchange with the top gas in the first heat exchanger 33 continues until the top gas temperature decreases by 23°C to 37°C, for example, 23°C, 28°C, 32°C, 34°C, or 37°C, and the total natural gas temperature increases to 151°C to 209°C, for example, 151°C, 160°C, 170°C, 190°C, or 209°C. This increases the carbon content of the hot sponge iron in the hydrogen-based shaft furnace by 0.8% to 1.05%, and reduces the second natural gas consumption and oxygen consumption of the reformer by 4.7% to 7.3%.

[0073] Optionally, the temperature of the top gas before passing through the first heat exchanger 33 is 166°C to 224°C, the temperature of the total natural gas before passing through the first heat exchanger 33 is 20°C to 30°C, and the temperature of the top gas after passing through the first heat exchanger 33 is 143°C to 187°C.

[0074] See also Figure 1 In an optional embodiment, before the first nitrogen and the top gas undergo heat exchange through the third heat exchanger 34, the temperature of the first nitrogen is 35°C to 45°C, for example, 35°C, 36°C, 40°C, 42°C, or 45°C. The temperature of the first nitrogen passing through the third heat exchanger 34 is lower than the temperature of the top gas passing through the third heat exchanger 34, and the first nitrogen undergoes heat exchange with the top gas in the third heat exchanger 34 until the temperature of the top gas decreases by 8°C to 30°C, for example, 8°C, 15°C, 17°C, 20°C, or 30°C, and the temperature of the first nitrogen increases to 104°C to 150°C, for example, 104°C, 110°C, 120°C, 135°C, or 150°C.

[0075] Optionally, the temperature of the top gas before passing through the third heat exchanger 34 is 141°C to 185°C, the temperature of the first nitrogen before passing through the third heat exchanger 34 is 35°C to 45°C, and the temperature of the top gas after passing through the third heat exchanger 34 is 124°C to 170°C.

[0076] The three-stage heat exchange process of top gas can recover the high-temperature heat of top gas, reducing the energy consumption of the vertical furnace process and CO2 emissions by 5.7% to 5.2%.

[0077] See also Figure 1In an optional embodiment, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 244° C. to 160° C., for example, 160° C., 180° C., 200° C., 220° C., or 244° C., and the temperature of the first nitrogen gas increases to 176° C. to 260° C., for example, 176° C., 200° C., 220° C., 240° C., or 260° C.

[0078] Optionally, the temperature of the first nitrogen before passing through the fourth heat exchanger 62 is 104°C to 150°C, the temperature of the second nitrogen before passing through the fourth heat exchanger 62 is 430°C to 450°C, and the temperature of the second nitrogen after passing through the fourth heat exchanger 62 is 196°C to 280°C.

[0079] See also Figure 1 In an optional embodiment, before the cold pellets are heat exchanged with the first nitrogen, the cold pellets are at room temperature. The temperature of the cold pellets may be 20°C to 30°C, for example, any value among 20°C, 22°C, 25°C, 28°C, or 30°C. The temperature of the cold pellets is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen decreases to 102°C to 120°C, for example, any value among 102°C, 105°C, 110°C, or 120°C. The temperature of the cold pellets increases to 100°C to 117°C, for example, any value among 100°C, 105°C, 110°C, or 117°C. After the temperature of the cold pellets increases, the liquid water carried by them turns into water vapor and evaporates.

[0080] See also Figure 1 In an optional embodiment, before the oxygen and the second nitrogen pass through the second heat exchanger 63 for heat exchange, the temperature of the oxygen is 35°C to 45°C, for example, 35°C, 37°C, 40°C, 42°C, or 45°C. The temperature of the oxygen passing through the second heat exchanger 63 is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen exchanges heat with the second nitrogen in the second heat exchanger 63 until the temperature of the second nitrogen decreases by 59°C to 96°C, for example, 59°C, 69°C, 75°C, 86°C, or 96°C, and the temperature of the oxygen increases to 117°C to 164°C, for example, 117°C, 131°C, 140°C, 152°C, or 164°C. This reduces the second natural gas consumption and oxygen consumption of the reformer by 1.4% to 2.2%.

[0081] Optionally, the temperature of the second nitrogen before passing through the second heat exchanger 63 is 196° C. to 280° C., and the temperature of the second nitrogen after passing through the second heat exchanger 63 is 137° C. to 184° C.

[0082] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to convey the hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.5% to 0.9%.

[0083] See also Figure 1 In an optional embodiment, cold pellets are transported to the hydrogen-based shaft furnace 1 via a vertical belt conveyor 91, where they exchange heat with the first nitrogen. Hot pellets are typically stored in a tank before being added to the hydrogen-based shaft furnace 1. The vertical belt conveyor 91 transports the hot pellets to the tank buffer. When hot pellets are needed, they are added to the hydrogen-based shaft furnace 1. Heating the cold pellets produces hot pellets, which have a lower viscosity. This reduces the risk of hot pellets adhering to the tank wall and improves the smoothness and reliability of material discharge.

[0084] Optionally, the vertical belt conveyor 91 is a semi-enclosed vertical belt conveyor 91.

[0085] Optionally, the vertical belt conveyor 91 has multiple gas introduction points 913 for inputting the first nitrogen gas. The multiple gas introduction points 913 are distributed along the conveying direction of the cold pellets, and the amount of the first nitrogen gas inputted into the gas introduction points 913 near the hydrogen-based vertical furnace 1 is less than the amount of the first nitrogen gas inputted into the gas introduction points 913 far from the hydrogen-based vertical furnace 1. Furthermore, the number of gas introduction points 913 is 8 to 10, and the amount of the first nitrogen gas inputted decreases by 20% from the gas introduction points 913 far from the hydrogen-based vertical furnace 1 to the gas introduction points 913 near the hydrogen-based vertical furnace 1. Specifically, the vertical belt conveyor 91 has a feeding end 911 and a discharging end 912. The feeding end 911 is farther away from the hot pellet inlet 11 of the hydrogen-based vertical furnace 1 than the discharging end 912. The feeding end 911 is provided with a tail wheel, and the discharging end 912 is provided with a head wheel. A plurality of gas introduction positions 913 are arranged at intervals on the vertical belt conveyor 91, located between the tail wheel and the head wheel. The vertical belt conveyor 91 transports the cold pellets to the material tank. Since the flow direction of the first nitrogen is the same as the flow direction of the cold pellets, the first nitrogen input from the gas introduction position 913 far away from the hydrogen-based vertical furnace 1 will be transported together with the cold pellets through the gas introduction position 913 close to the hydrogen-based vertical furnace 1. The temperature of the cold pellets gradually increases during the transportation process. The closer the cold pellets are to the hydrogen-based vertical furnace 1, the higher the temperature, and the smaller the amount of the first nitrogen input into the corresponding gas introduction position 913, which is beneficial to improving the heat exchange efficiency of the cold pellets. Due to the chimney effect, the gas introduced from the lower part of the vertical belt conveyor 91 flows upward, and a "heat storage" phenomenon occurs in the upper part of the vertical belt conveyor 91. The stepped introduction of gas volume can fully utilize the "heat storage" phenomenon and improve the heat exchange efficiency between the first nitrogen and the cold pellets.

[0086] Optionally, the first nitrogen is extracted from the head wheel of the vertical belt conveyor 91 after heat exchange with the cold pellets to be discharged after dust removal in the top dust collector 92 .

[0087] Optionally, the method for recovering waste heat from a hydrogen-based vertical furnace process in any of the above embodiments is applied to the field of hydrogen-based vertical furnaces.

[0088] The following further illustrates the method for recovering waste heat from a hydrogen-based shaft furnace process with reference to specific examples. It should be understood that the present invention is not limited to the following examples.

[0089] Example 1

[0090] The total natural gas is heated by heat exchange in the first heat exchanger 33 to obtain the first natural gas and the second natural gas, and the first natural gas is converted into high-temperature carburizing gas; the second natural gas and the oxygen heated by heat exchange in the second heat exchanger 63 are converted in the reformer 5 to obtain the first reducing gas; the first nitrogen is heated by heat exchange in the third heat exchanger 34 once and heated by heat exchange in the fourth heat exchanger 62 twice, and then heat-exchanged with the cold pellets to obtain hot pellets; the hot pellets, the first reducing gas and the high-temperature carburizing gas are added to the hydrogen-based vertical furnace 1, and the hot pellets are reduced and carburized in the hydrogen-based vertical furnace 1 to obtain hot sponge iron and top gas; the top gas is sequentially subjected to dust removal in the first dry dust collector 31, primary heat exchange cooling in the fifth heat exchanger 32, secondary heat exchange cooling in the first heat exchanger 33, tertiary heat exchange cooling in the third heat exchanger 34, and the first The washing tower 35 washes, the first compressor 36 pressurizes and the decarburization system 37 decarburizes to obtain a total decarburized gas, a part of the total decarburized gas forms a first decarburized gas, and the other part forms a second decarburized gas; the first decarburized gas is sequentially passed through the fifth heat exchanger 32 for heat exchange and the heating furnace 4 for heating to obtain a second reducing gas that is sprayed back into the hydrogen-based vertical furnace 1; the second decarburized gas is burned for heating in the heating furnace 4; the hot sponge iron is transported to the intermediate tank 2, and the hot sponge iron in the intermediate tank 2 is transported to the buffer tank 7 connected to the electric furnace 8 through the second nitrogen, the second nitrogen is discharged from the buffer tank 7 and sequentially passes through the second dry dust collector 61 for dust removal, the fourth heat exchanger 62 for primary heat exchange and cooling, the second heat exchanger 63 for secondary heat exchange and cooling, the second washing tower 64 for washing and the second compressor 65 for pressurization, and then circulated to transport the hot sponge iron in the intermediate tank 2.

[0091] Furthermore, the hot pellets are fed from the top, the hot sponge iron is discharged from the bottom, and the first reducing gas and the second reducing gas are fed from the middle and discharged from the top.

[0092] Furthermore, the first reducing gas and the second reducing gas are mixed to form a total reducing gas and introduced into the hydrogen-based vertical furnace 1; the total reducing gas is composed of CO, H2, N2, CO2, H2O and CH4, the content of CO and H2 is greater than or equal to 80% of the total reducing gas, the content of N2, CO2, and H2O is less than or equal to 10% of the total reducing gas, and the content of CH4 is less than or equal to 10% of the total reducing gas.

[0093] Furthermore, the temperature of the total reducing gas is 850° C., and the pressure of the total reducing gas is 0.25 MPa.

[0094] Furthermore, the metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 650°C.

[0095] Furthermore, the temperature of the hot pellets is 100°C, and the gas volume of the first nitrogen is 300 Nm 3 / tDRI.

[0096] Furthermore, the temperature of the top gas is 395° C., and the pressure of the top gas is 0.15 MPa.

[0097] Furthermore, the dust content of the second nitrogen after the second dry dust collector 61 is 10 mg / Nm 3 After the second nitrogen is washed by the second washing tower 64, the temperature is reduced to 40°C. After the second nitrogen is pressurized by the second compressor 65, the pressure is increased to 0.25MPa to 0.55MPa.

[0098] Furthermore, the molar ratio of the first decarbonized gas to the second decarbonized gas is 18.7; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top gas exchange heat in the fifth heat exchanger 32 until the temperature of the top gas decreases by 151°C and the temperature of the first decarbonized gas increases by 270°C.

[0099] Furthermore, before the total natural gas and the top gas undergo heat exchange through the first heat exchanger 33 , the temperature of the total natural gas is 30° C., which is lower than the temperature of the top gas passing through the first heat exchanger 33 . The total natural gas undergoes heat exchange with the top gas through the first heat exchanger 33 until the temperature of the top gas decreases by 23° C. and the temperature of the total natural gas increases to 151° C., thereby increasing the carbon content of the hot sponge iron in the shaft furnace by 0.8% and reducing the second natural gas consumption and oxygen consumption of the reformer by 4.7%.

[0100] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 8°C and the temperature of the first nitrogen is increased to 113°C.

[0101] The three-stage heat exchange process of top gas can recover the high-temperature heat of top gas, reducing the energy consumption of the vertical furnace process and CO2 emissions by 5.7%.

[0102] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 182° C. and the temperature of the first nitrogen gas increases to 238° C.

[0103] Furthermore, before the cold pellets are heat exchanged with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen drops to 102° C., and the temperature of the cold pellets rises to 100° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0104] Furthermore, before the oxygen and the second nitrogen are heat exchanged through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen and the second nitrogen are heat exchanged through the second heat exchanger 63 until the temperature of the second nitrogen is reduced by 86° C. and the temperature of the oxygen is increased to 152° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 2.0%.

[0105] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.45%.

[0106] Furthermore, the cold pellets are transported to the hydrogen-based vertical furnace 1 through a vertical belt conveyor 91, and the cold pellets exchange heat with the first nitrogen on the vertical belt conveyor 91. The vertical belt conveyor 91 has 8 to 10 gas introduction positions 913 for inputting the first nitrogen. The multiple gas introduction positions 913 are distributed along the conveying direction of the cold pellets. The amount of the first nitrogen input decreases by 20% from the gas introduction position 913 away from the hydrogen-based vertical furnace 1 to the gas introduction position 913 close to the hydrogen-based vertical furnace 1.

[0107] Example 2

[0108] The difference between this embodiment and Example 1 is that the temperature of the hot pellets is 106°C, the gas volume of the first nitrogen is 700Nm 3 / tDRI.

[0109] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 17°C and the temperature of the first nitrogen is increased to 104°C.

[0110] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 244° C. and the temperature of the first nitrogen gas increases to 176° C.

[0111] Furthermore, before the cold pellets are heat exchanged with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen drops to 108° C., and the temperature of the cold pellets rises to 106° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0112] Furthermore, before the oxygen and the second nitrogen undergo heat exchange through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen undergoes heat exchange with the second nitrogen through the second heat exchanger 63 until the temperature of the second nitrogen decreases by 59° C. and the temperature of the oxygen increases to 117° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer 5 by 1.4%.

[0113] The two-stage heat exchange of the second nitrogen realizes heat recovery of the conveying gas used to convey the hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace 1 by about 0.6%.

[0114] Example 3

[0115] The difference between this embodiment and embodiment 1 is that the temperature of the total reducing gas is 950° C. and the pressure of the total reducing gas is 0.25 MPa.

[0116] Furthermore, the metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 730° C.

[0117] Furthermore, the temperature of the hot pellets is 100°C, and the gas volume of the first nitrogen is 300 Nm 3 / tDRI.

[0118] Furthermore, the temperature of the top gas is 425° C., and the pressure of the top gas is 0.15 MPa.

[0119] Furthermore, the molar ratio of the first decarbonized gas to the second decarbonized gas is 13.9; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top gas exchange heat in the fifth heat exchanger 32 until the temperature of the top gas decreases by 153°C and the temperature of the first decarbonized gas increases by 300°C.

[0120] Furthermore, before the total natural gas and the top gas undergo heat exchange in the first heat exchanger 33, the temperature of the total natural gas is 30° C., which is lower than the temperature of the top gas passing through the first heat exchanger 33. The total natural gas undergoes heat exchange with the top gas in the first heat exchanger 33 until the temperature of the top gas decreases by 28° C. and the temperature of the total natural gas increases to 179° C., thereby increasing the carbon content of the hot sponge iron in the hydrogen-based vertical furnace 1 by 0.95% and reducing the second natural gas consumption and oxygen consumption of the reformer by 6.0%.

[0121] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 12°C and the temperature of the first nitrogen is increased to 132°C.

[0122] The three-stage heat exchange process of top gas can recover the high-temperature heat of top gas, reducing the energy consumption of the vertical furnace process and CO2 emissions by 5.6%.

[0123] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 172° C. and the temperature of the first nitrogen gas increases to 248° C.

[0124] Furthermore, before the cold pellets are heat exchanged with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen drops to 102° C., and the temperature of the cold pellets rises to 100° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0125] Furthermore, before the oxygen and the second nitrogen undergo heat exchange through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen undergoes heat exchange with the second nitrogen through the second heat exchanger 63 until the temperature of the second nitrogen decreases by 90° C. and the temperature of the oxygen increases to 158° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 2.2%.

[0126] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.45%.

[0127] Example 4

[0128] The difference between this embodiment and Example 3 is that the temperature of the hot pellets is 111°C. The gas volume of the first nitrogen is 700Nm 3 / tDRI.

[0129] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 24°C and the temperature of the first nitrogen is increased to 120°C.

[0130] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 232° C. and the temperature of the first nitrogen gas increases to 188° C.

[0131] Furthermore, before the cold pellets exchange heat with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets exchange heat with the first nitrogen, the temperature of the first nitrogen drops to 113° C., and the temperature of the cold pellets rises to 111° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0132] Furthermore, before the oxygen and the second nitrogen undergo heat exchange through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen undergoes heat exchange with the second nitrogen through the second heat exchanger 63 until the temperature of the second nitrogen decreases by 64° C. and the temperature of the oxygen increases to 124° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 1.6%.

[0133] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.6%.

[0134] Example 5

[0135] The difference between this embodiment and embodiment 1 is that the temperature of the total reducing gas is 1050° C. and the pressure of the total reducing gas is 0.25 MPa.

[0136] Furthermore, the metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 800°C.

[0137] Furthermore, the temperature of the hot pellets is 103°C, and the gas volume of the first nitrogen is 300 Nm 3 / tDRI.

[0138] Furthermore, the temperature of the top gas is 455° C., and the pressure of the top gas is 0.15 MPa.

[0139] Furthermore, the molar ratio of the first decarbonized gas to the second decarbonized gas is 10.9; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top gas exchange heat in the fifth heat exchanger 32 until the temperature of the top gas decreases by 150°C and the temperature of the first decarbonized gas increases by 329°C.

[0140] Furthermore, before the total natural gas and the top gas undergo heat exchange through the first heat exchanger 33, the temperature of the total natural gas is 30° C., which is lower than the temperature of the top gas passing through the first heat exchanger 33. The total natural gas undergoes heat exchange with the top gas in the first heat exchanger 33 until the temperature of the top gas decreases by 37° C. and the temperature of the total natural gas increases to 209° C., thereby increasing the carbon content of the hot sponge iron in the hydrogen-based vertical furnace 1 by 1.05% and reducing the second natural gas consumption and oxygen consumption of the reformer by 7.3%.

[0141] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 15°C and the temperature of the first nitrogen is increased to 150°C.

[0142] The three-stage heat exchange process of top gas can recover the high-temperature heat of top gas, reducing the energy consumption of the vertical furnace process and CO2 emissions by 5.2%.

[0143] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 62, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 160° C. and the temperature of the first nitrogen gas increases to 260° C.

[0144] Furthermore, before the cold pellets are heat exchanged with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen drops to 105° C., and the temperature of the cold pellets rises to 103° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0145] Furthermore, before the oxygen and the second nitrogen undergo heat exchange through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen undergoes heat exchange with the second nitrogen through the second heat exchanger 63 until the temperature of the second nitrogen decreases by 96° C. and the temperature of the oxygen increases to 164° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 2.2%.

[0146] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.41%.

[0147] Example 6

[0148] The difference between this embodiment and Example 5 is that the temperature of the hot pellets is 117°C, the gas volume of the first nitrogen is 700Nm 3 / tDRI.

[0149] Furthermore, before the first nitrogen and the top coal gas are heat exchanged through the third heat exchanger 34, the temperature of the first nitrogen is 40°C, which is lower than the temperature of the top coal gas passing through the third heat exchanger 34, and the first nitrogen and the top coal gas are heat exchanged in the third heat exchanger 34 until the temperature of the top coal gas is reduced by 30°C and the temperature of the first nitrogen is increased to 135°C.

[0150] Furthermore, before the second nitrogen gas exchanges heat with the first nitrogen gas through the fourth heat exchanger 34, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger 34, and the second nitrogen gas exchanges heat with the first nitrogen gas in the fourth heat exchanger 34 until the temperature of the second nitrogen gas decreases by 220° C. and the temperature of the first nitrogen gas increases to 200° C.

[0151] Furthermore, before the cold pellets are heat exchanged with the first nitrogen, the temperature of the cold pellets is 30° C., which is lower than the temperature of the first nitrogen. After the cold pellets are heat exchanged with the first nitrogen, the temperature of the first nitrogen drops to 120° C., and the temperature of the cold pellets rises to 117° C., and the water brought into the cold pellets evaporates from liquid to gas.

[0152] Furthermore, before the oxygen and the second nitrogen undergo heat exchange through the second heat exchanger 63, the temperature of the oxygen is 40° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger 63. The oxygen undergoes heat exchange with the second nitrogen through the second heat exchanger 63 until the temperature of the second nitrogen decreases by 69° C. and the temperature of the oxygen increases to 131° C., thereby reducing the second natural gas consumption and oxygen consumption of the reformer by 1.6%.

[0153] The two-stage heat exchange of the second nitrogen realizes the heat recovery of the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based vertical furnace by about 0.57%.

[0154] See also Figure 1In an optional embodiment, the present invention provides a system for recovering waste heat from a hydrogen-based vertical furnace process, which is used to implement the method for recovering waste heat from a hydrogen-based vertical furnace process of any of the above-mentioned embodiments. The system for recovering waste heat from a hydrogen-based vertical furnace process includes a vertical belt conveyor 91, a hydrogen-based vertical furnace 1, an intermediate tank 2, a buffer tank 7, an electric furnace 8, a heating furnace 4, a top gas recovery unit, a converter 5, and a nitrogen recovery unit. The vertical belt conveyor 91 is used to transport cold pellets. The cold pellets are heat-exchanged with the first nitrogen on the vertical belt conveyor 91 to obtain hot pellets. The discharge end 912 of the vertical belt conveyor 91 is connected to a material tank. The vertical belt conveyor 91 transports the hot pellets to the material tank for centralized buffering. The hydrogen-based vertical furnace 1 is used for reducing and carburizing the hot pellets to obtain hot sponge iron and top gas. The intermediate tank 2 is connected to the hydrogen-based vertical furnace 1 and receives the hot sponge iron discharged from the hydrogen-based vertical furnace 1. The hot sponge iron can be buffered. The hot sponge iron discharged from the intermediate tank 2 is stored in the intermediate tank 2; the buffer tank 7 is connected to the intermediate tank 2 and receives the hot sponge iron discharged from the intermediate tank 2. The hot sponge iron discharged from the intermediate tank 2 is transported to the buffer tank by pneumatic conveying; the electric furnace 8 is connected to the buffer tank 7 and receives the hot sponge iron discharged from the buffer tank 7. The hot sponge iron in the intermediate tank 2 is transported to the electric furnace 8 after passing through the buffer tank 7; the heating furnace 4 is used for heating; the top gas recovery unit includes a first dry dust collector 31, a fifth heat exchanger 32, a first heat exchanger 33 and a second heat exchanger 34 connected in sequence. The first dry dust collector 31 is connected to the hydrogen-based vertical furnace 1, and the output end of the decarbonization system 37 is connected to the fifth heat exchanger 32 and the heating furnace 4 respectively; the reformer 5 is connected to the hydrogen-based vertical furnace 1 for the second natural gas and oxygen conversion process to obtain the first reducing gas fed into the hydrogen-based vertical furnace 1; the nitrogen recovery unit includes the second dry dust collector 61, the fourth heat exchanger 62, the second heat exchanger 63 and the second heat exchanger 64 connected in sequence. 63, the second washing tower 64 and the second compressor 65, the second dry dust collector 61 and the second compressor 65 are respectively connected to the buffer tank 7 to form a nitrogen circulation loop, so that the nitrogen can be recycled and reused, the first pipe section 3411 connecting the second compressor 65 and the buffer tank 7 is also connected to the intermediate tank 2 to transport hot sponge iron, the fourth heat exchanger 62 is connected to the second pipe section 3412 for transporting the first nitrogen, and the second heat exchanger 63 is connected to the oxygen pipeline 631 for transporting oxygen.

[0155] Optionally, the discharge end 912 of the vertical belt conveyor 91 is connected to a top dust collector 92 , and the first nitrogen is discharged after completing heat exchange with the cold pellets through the top dust collector 92 for dust removal.

[0156] Optionally, the pipeline for conveying the first nitrogen is the first nitrogen pipeline 341, and the pipeline for conveying the second nitrogen is the second nitrogen pipeline 71; the first pipeline 341 includes a first pipeline section 3411 and a second pipeline section 3412, the first nitrogen pipeline 341 is connected to the nitrogen pipeline network, and the pressure of the first nitrogen is 0.1 MPa.

[0157] Optionally, a hot pellet inlet 11 and a top gas outlet 12 are provided at the top of the hydrogen-based vertical furnace 1, and the top gas outlet 12 is connected to the first dry dust collector 31. A reducing gas inlet 13 and a high-temperature carburizing gas inlet 14 are provided at the middle and lower part of the hydrogen-based vertical furnace 1. The converter 5 and the heating furnace 4 are both connected to the reducing gas inlet 13, and the first heat exchanger 33 is connected to the high-temperature carburizing gas inlet 14. A hot sponge iron outlet 15 is provided at the lower part of the hydrogen-based vertical furnace 1, and the intermediate tank 2 is connected to the hot sponge iron outlet 15.

[0158] Optionally, the discharge end 912 of the vertical belt conveyor 91 is close to one end of the hydrogen-based vertical furnace 1 and the material tank, and the material tank and the hydrogen-based vertical furnace 1 are arranged vertically from top to bottom. The discharge end 912 of the vertical belt conveyor 91, the hydrogen-based vertical furnace 1 and the intermediate tank 2 are arranged vertically from top to bottom, so that the hot pellets in the vertical belt conveyor 91 or the material tank can be transported to the hydrogen-based vertical furnace 1 under the action of its own gravity, and the hot sponge iron in the hydrogen-based vertical furnace 1 can be transported to the intermediate tank 2 under the action of its own gravity, without the need for additional conveying equipment, which is beneficial to reducing energy consumption; the buffer tank 7 and the electric furnace 8 are arranged vertically from top to bottom, and the hot sponge iron in the intermediate tank 2 can be transported to the electric furnace 8 under the action of its own gravity, without the need for additional conveying equipment, which is beneficial to reducing energy consumption.

[0159] See also Figure 1In a specific embodiment, hot pellets are added to the hydrogen-based vertical furnace 1 through the hot pellet inlet 11, and are reduced and carburized in the hydrogen-based vertical furnace 1 to generate hot sponge iron and top gas. The top gas passes through the first dry dust collector 31, the fifth heat exchanger 32, the first heat exchanger 33, the third heat exchanger 34, the first scrubber 35, the first compressor 36, and the decarburization system 37 in sequence to obtain total decarburization gas and desorption gas. The desorption gas is discharged through the desorption gas pipeline 373. The total decarburization gas is divided into first decarburization gas and second decarburization gas. The first decarburization gas passes through the first decarburization gas pipeline 371 and the fifth heat exchanger 32 to exchange heat with the top gas that has passed through the fifth heat exchanger 32. The first decarburization gas then enters the heating furnace 4 for heating to form the second reducing gas. The second decarburization gas is then injected into the hydrogen-based vertical furnace 1 through the reducing gas inlet 13. The second decarburization gas is transported to the heating furnace 4 through the second decarburization gas pipeline 372 to be burned and provide heat for heating the heating furnace 4. The first heat exchanger 33 is connected to the natural gas network via a main natural gas pipeline 331. The total natural gas has a pressure of 0.5 MPa. After heat exchange with the top gas in the first heat exchanger 33, the total natural gas is divided into the first natural gas and the second natural gas. The first natural gas and the second natural gas are respectively delivered to the high-temperature carburizing gas inlet 14 and the reformer 5 via the first natural gas pipeline 332 and the second natural gas pipeline 333. The second heat exchanger 63 is connected to the oxygen network via an oxygen pipeline 631. The oxygen has a pressure of 0.6 MPa. After heat exchange with the second nitrogen gas in the second heat exchanger 63, the oxygen is delivered to the reformer 5, where it is converted with the second natural gas to produce the first reducing gas. The first reducing gas is then injected into the hydrogen-based vertical furnace 1 through the reducing gas inlet 13. The hot sponge iron is discharged from the hot sponge iron outlet 15 to the intermediate tank 2, and is transported to the buffer tank 7 and then into the electric furnace 8 through the second nitrogen in the second nitrogen pipeline 71. The second nitrogen absorbs the heat of the hot sponge iron in the process of transporting the hot sponge iron to the buffer tank 7. After completing the transportation of the hot sponge iron, the second nitrogen is discharged from the buffer tank 7 and passes through the second dry dust collector 61, the fourth heat exchanger 62, the second heat exchanger 63, the second washing tower 64 and the second compressor 65 in sequence, and then circulates to the intermediate tank 2 to transport the hot sponge iron to the buffer tank 7. The heat absorbed by the second nitrogen from the hot sponge iron is used for heat exchange with the first nitrogen in the fourth heat exchanger 62 and for heat exchange with oxygen in the second heat exchanger 63, thereby making full use of the heat absorbed by the second nitrogen from the hot sponge iron.

[0160] Optionally, the system for recovering waste heat from the hydrogen-based vertical furnace process of any of the above embodiments is applied to the field of hydrogen-based vertical furnaces.

[0161] The method and system for recovering waste heat from a hydrogen-based vertical furnace process of the present invention fully recycles and utilizes the sensible heat of the top gas and the second nitrogen gas that has absorbed hot sponge iron. Specifically, the top gas generated during the reduction treatment of hot pellets has a large amount of sensible heat after undergoing a first dry dust removal process. The sensible heat of the top gas is recovered and reused in the reduction treatment of the hot pellets. The top gas undergoes staged heat exchange through multiple heat exchangers, which can fully realize heat recovery and utilization while meeting the different heat requirements of various processes. The second nitrogen gas that has absorbed the heat of the hot sponge iron has a large amount of sensible heat after undergoing a second dry dust removal process. The second nitrogen gas passes through multiple heat exchangers to recover the sensible heat of the second nitrogen gas and use it to heat the cold pellets and oxygen, further improving the recovery and utilization of sensible heat. This helps reduce the process energy consumption of the hydrogen-based vertical furnace in the production of hot sponge iron, which is of great significance for reducing CO2 emissions.

[0162] Throughout this specification, references to terms such as "this embodiment," "example," and "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0163] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for recovering waste heat from a hydrogen-based shaft furnace process, characterized in that: include: passing the total natural gas through a first heat exchanger to heat up the temperature to obtain a first natural gas and a second natural gas, wherein the first natural gas is formed into a high-temperature carburized gas; Converting the second natural gas and the oxygen heated by the second heat exchanger in a converter to obtain a first reducing gas; The first nitrogen is sequentially passed through the third heat exchanger for primary heat exchange and the fourth heat exchanger for secondary heat exchange, and then heat-exchanged with the cold pellets to obtain hot pellets; adding the hot pellets, the first reducing gas and the high-temperature carburizing gas into a hydrogen-based shaft furnace, and subjecting the hot pellets to reduction and carburizing treatment in the hydrogen-based shaft furnace to obtain hot sponge iron and top gas; The top coal gas is sequentially subjected to dust removal by a first dry dust collector, primary heat exchange and cooling by a fifth heat exchanger, secondary heat exchange and cooling by the first heat exchanger, tertiary heat exchange and cooling by the third heat exchanger, washing by a first washing tower, pressurizing by a first compressor, and decarbonization by a decarbonization system to obtain a total decarbonized gas, a portion of which is formed into a first decarbonized gas, and the other portion is formed into a second decarbonized gas; The first decarbonized gas is sequentially passed through the fifth heat exchanger for heat exchange and heated in the heating furnace to obtain the second reducing gas which is sprayed back into the hydrogen-based vertical furnace; the second decarbonized gas is burned to heat the heating furnace; The hot sponge iron is transported to an intermediate tank, and the hot sponge iron in the intermediate tank is transported to a buffer tank connected to an electric furnace through a second nitrogen gas. The second nitrogen gas is discharged from the buffer tank and sequentially passes through a second dry dust collector for dust removal, a fourth heat exchanger for primary heat exchange and cooling, a second heat exchanger for secondary heat exchange and cooling, a second washing tower for washing, and a second pressurizer for pressurizing, and then circulates the hot sponge iron in the intermediate tank.

2. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 1, characterized in that: The hot pellets are fed from above, the hot sponge iron is discharged from below, and the first reducing gas and the second reducing gas are fed from the middle and discharged from above.

3. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 1, characterized in that: The first reducing gas and the second reducing gas are mixed to form a total reducing gas and introduced into the hydrogen-based vertical furnace; The total reducing gas consists of CO, H2, N2, CO2, H2O and CH4, the content of CO and H2 is greater than or equal to 80% of the total reducing gas, the content of N2, CO2 and H2O is less than or equal to 10% of the total reducing gas, and the content of CH4 is less than or equal to 10% of the total reducing gas; And / or, the temperature of the total reducing gas is 850° C. to 1050° C., and the pressure of the total reducing gas is 0.25 MPa to 0.55 MPa.

4. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 1, characterized in that: The metallization rate of the hot sponge iron is greater than 92%, and the temperature of the hot sponge iron is 650° C. to 800° C.; And / or, the temperature of the hot pellets is 100°C to 117°C, the gas volume of the first nitrogen is 300Nm 3 / tDRI~700Nm 3 / tDRI; And / or, the temperature of the top gas is 395° C. to 455° C., and the pressure of the top gas is 0.15 MPa to 0.45 MPa.

5. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 1, characterized in that: The dust content of the second nitrogen after the second dry dust collector is 8 mg / Nm 3 ~12mg / Nm 3 After the second nitrogen is washed by the second washing tower, the temperature is reduced to 35°C to 45°C, and after the second nitrogen is pressurized by the second compressor, the pressure is 0.25MPa to 0.55MPa; and / or, the molar ratio of the first decarbonized gas to the second decarbonized gas is 10.9 to 18.7; the temperature of the first decarbonized gas is lower than the temperature of the top gas passing through the fifth heat exchanger, and the first decarbonized gas and the top gas exchange heat in the fifth heat exchanger until the temperature of the top gas decreases by 153° C. to 150° C. and the temperature of the first decarbonized gas increases by 270° C. to 329° C.; and / or, before the total natural gas and the top gas pass through the first heat exchanger for heat exchange, the temperature of the total natural gas is 20° C. to 30° C., which is lower than the temperature of the top gas passing through the first heat exchanger, and the total natural gas and the top gas exchange heat in the first heat exchanger until the temperature of the top gas decreases by 23° C. to 37° C. and the temperature of the total natural gas increases to 151° C. to 209° C.; and / or, before the first nitrogen and the top gas pass through the third heat exchanger for heat exchange, the temperature of the first nitrogen is 35° C. to 45° C., which is lower than the temperature of the top gas passing through the third heat exchanger, and the first nitrogen exchanges heat with the top gas in the third heat exchanger until the temperature of the top gas decreases by 8° C. to 30° C. and the temperature of the first nitrogen increases to 104° C. to 150° C.; and / or, before the second nitrogen gas and the first nitrogen gas pass through the fourth heat exchanger for heat exchange, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas passing through the fourth heat exchanger, and the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger until the temperature of the second nitrogen gas decreases by 244° C. to 160° C. and the temperature of the first nitrogen gas increases to 176° C. to 260° C.; and / or, before the cold pellets are heat-exchanged with the first nitrogen, the temperature of the cold pellets is 20° C. to 30° C., which is lower than the temperature of the first nitrogen; after the cold pellets are heat-exchanged with the first nitrogen, the temperature of the first nitrogen is reduced to 102° C. to 120° C., and the temperature of the cold pellets is increased to 100° C. to 117° C.; And / or, before the oxygen and the second nitrogen pass through the second heat exchanger for heat exchange, the temperature of the oxygen is 35° C. to 45° C., which is lower than the temperature of the second nitrogen passing through the second heat exchanger, and the oxygen and the second nitrogen exchange heat in the second heat exchanger until the temperature of the second nitrogen decreases by 59° C. to 96° C. and the temperature of the oxygen increases to 117° C. to 164° C.

6. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 1, characterized in that: The cold pellets are transported to the hydrogen-based vertical furnace via a vertical belt conveyor, and the cold pellets exchange heat with the first nitrogen on the vertical belt conveyor; the vertical belt conveyor has a plurality of gas introduction points for inputting the first nitrogen, and the plurality of gas introduction points are distributed along the conveying direction of the cold pellets, and the amount of the first nitrogen inputted into the gas introduction points close to the hydrogen-based vertical furnace is less than the amount of the first nitrogen inputted into the gas introduction points far from the hydrogen-based vertical furnace.

7. The method for recovering waste heat from a hydrogen-based shaft furnace process according to claim 6, characterized in that: The number of the gas introduction positions is 8 to 10, and the amount of the first nitrogen gas input from the gas introduction position far from the hydrogen-based vertical furnace to the gas introduction position close to the hydrogen-based vertical furnace decreases by 20%.

8. A system for recovering waste heat from a hydrogen-based shaft furnace process, characterized in that: include: A vertical belt conveyor is used to convey cold pellets, where the cold pellets are heat-exchanged with the first nitrogen to obtain hot pellets; Hydrogen-based shaft furnace for hot pellet reduction and carburizing to obtain hot sponge iron and top gas; a tundish connected to the hydrogen-based vertical furnace and receiving the hot sponge iron discharged from the hydrogen-based vertical furnace; a buffer tank connected to the intermediate tank and receiving the hot sponge iron discharged from the intermediate tank; an electric furnace connected to the buffer tank and receiving the hot sponge iron discharged from the buffer tank; Heating furnace, used for heating; a top gas recovery unit, the top gas recovery unit comprising a first dry dust collector, a fifth heat exchanger, a first heat exchanger, a third heat exchanger, a first scrubber, a first compressor, and a decarbonization system connected in sequence, the first dry dust collector being connected to the hydrogen-based vertical furnace, and an output end of the decarbonization system being connected to the fifth heat exchanger and the heating furnace, respectively; a reformer connected to the hydrogen-based vertical furnace, for performing a second natural gas and oxygen reforming process to obtain a first reducing gas fed into the hydrogen-based vertical furnace; A nitrogen recovery unit includes a second dry dust collector, a fourth heat exchanger, a second heat exchanger, a second washing tower, and a second compressor connected in sequence. The second dry dust collector and the second compressor are respectively connected to the buffer tank to form a nitrogen circulation loop. The first pipe section connecting the second compressor and the buffer tank is also connected to the intermediate tank to transport the hot sponge iron. The fourth heat exchanger is connected to the second pipe section for transporting the first nitrogen. The second heat exchanger is connected to the oxygen pipeline for transporting the oxygen.

9. The system for recovering waste heat from a hydrogen-based shaft furnace process according to claim 8, characterized in that: The top of the hydrogen-based vertical furnace is provided with a hot pellet inlet and a top gas outlet, and the top gas outlet is connected to the first dry dust collector. The middle of the hydrogen-based vertical furnace is provided with a reducing gas inlet and a high-temperature carburizing gas inlet, the converter and the heating furnace are both connected to the reducing gas inlet, the first heat exchanger is connected to the high-temperature carburizing gas inlet, and the lower part of the hydrogen-based vertical furnace is provided with a hot sponge iron outlet, and the intermediate tank is connected to the hot sponge iron outlet.

10. The system for recovering waste heat from a hydrogen-based shaft furnace process according to claim 8, characterized in that: The discharge end of the vertical belt conveyor is close to the end of the hydrogen-based vertical furnace. The discharge end of the vertical belt conveyor, the hydrogen-based vertical furnace and the intermediate tank are arranged vertically from top to bottom.

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