Method and system for recovering waste heat from hydrogen-based shaft furnace processes

Abstract

The present application relates to a hydrogen-based shaft furnace direct reduction technology field, and relates to a hydrogen-based shaft furnace process waste heat recovery method and system. The method comprises the following steps: heating total natural gas to obtain second natural gas and high-temperature carburizing gas; converting the second natural gas and oxygen to obtain first reduction gas; heating first nitrogen gas and exchanging heat with cold balling to obtain hot balling; adding the hot balling, the first reduction gas and the high-temperature carburizing gas into a hydrogen-based shaft furnace to obtain hot sponge iron and top coal gas; sequentially performing dust removal, heat exchange, washing, pressurization and decarburization on the top coal gas to obtain first decarburization gas and second decarburization gas; heating the first decarburization gas to obtain second reduction gas which is sprayed back to the hydrogen-based shaft furnace; and sequentially performing dust removal, heat exchange, washing and pressurization on the hot sponge iron which is transported to a buffer tank through second nitrogen gas, and then recycling the hot sponge iron. The sensible heat of the top coal gas and the hot sponge iron is fully recovered, the problem of sensible heat waste of the hydrogen-based shaft furnace is reduced, and thus the process energy consumption and CO2 emission are reduced.

Description

Technical Field

[0001] This invention relates to the field of hydrogen-based vertical furnace direct reduction technology, and in particular to a method and system for recovering waste heat from hydrogen-based vertical furnace processes. Background Technology

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

[0003] Currently, the temperature of the top gas produced by the MIDREX process is around 411℃. After wet dust removal, the temperature of the top gas drops to 50℃, wasting a significant amount of sensible heat and generating a large amount of sludge that needs to be treated, thus increasing the burden on the water system. The temperature of the top gas produced by the HYL-ZR process is around 500℃. The top gas passes through a waste heat boiler to generate steam, which is then used in the decarbonization system. After heat exchange, the temperature of the top gas drops to 195℃, and it then enters a quench orifice plate for water spray washing. However, some of the sensible heat is still not fully utilized.

[0004] In addition, the hot sponge iron in the hydrogen-based shaft furnace needs to be transported to the electric furnace via 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 transport process. The HYL-ZR process uses water spray to cool the nitrogen used for transport through a quench plate, which wastes a lot of sensible heat.

[0005] Therefore, how to recover the sensible heat of top coal gas and nitrogen used to transport hot sponge iron in order to reduce energy consumption and CO2 emissions in the hydrogen-based shaft furnace process has become an urgent technical problem to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method and system for waste heat recovery in a hydrogen-based vertical shaft furnace process, which solves the problem of low sensible heat recovery and utilization rate of top gas and nitrogen used to transport hot sponge iron in the prior art, so as to reduce energy consumption and CO2 emissions in the hydrogen-based vertical shaft furnace process.

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

[0008] The total natural gas is heated by passing it through a first heat exchanger to obtain first natural gas and second natural gas. The first natural gas is formed as high-temperature carburized gas.

[0009] The second natural gas and oxygen, which have been heated by heat exchange in the second heat exchanger, are converted in a converter to obtain the first reducing gas.

[0010] The first nitrogen gas is heated by passing through the third heat exchanger once and the fourth heat exchanger twice before exchanging heat with the cold pellets to obtain hot pellets.

[0011] The hot pellets, the first reducing gas, and the high-temperature carburizing gas are added to a hydrogen-based vertical shaft furnace, and the hot pellets are reduced and carburized in the hydrogen-based vertical shaft furnace to obtain hot sponge iron and top coal gas.

[0012] The top coal gas is sequentially passed through a first dry dust collector for dust removal, a fifth heat exchanger for primary heat exchange and cooling, a first heat exchanger for secondary heat exchange and cooling, a third heat exchanger for tertiary heat exchange and cooling, a first scrubbing tower for washing, a first pressurizer for pressurization, and a decarbonization system for decarbonization to obtain total decarbonized gas. A portion of the total decarbonized gas is formed as first decarbonized gas, and another portion is formed as second decarbonized gas.

[0013] The first decarbonized gas is sequentially heated by the fifth heat exchanger and heated by the furnace to obtain the second reducing gas that is injected back into the hydrogen-based vertical furnace; the second decarbonized gas is then burned to heat the furnace.

[0014] The hot sponge iron is transported to an intermediate tank, and then transported to a buffer tank connected to an electric furnace by 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 pressurization before being circulated back to the hot sponge iron in the intermediate tank.

[0015] Optionally, the hot pellets are fed from the top, the hot sponge iron is discharged from the bottom, and the first and second reducing gases are fed from the middle and discharged from the top.

[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 is composed of CO, H2, N2, CO2, H2O and CH4, wherein 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℃~1050℃, and the pressure of the total reducing gas is 0.25MPa~0.55MPa.

[0019] Optionally, the metallization rate of the hot-state sponge iron is greater than 92%, and the temperature of the hot-state sponge iron is 650℃~800℃;

[0020] And / or, the temperature of the hot pellet is 100℃~117℃, and the flow rate of the first nitrogen gas is 300Nm³. 3 / tDRI~700Nm 3 / tDRI;

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

[0022] Optionally, the dust content of the second nitrogen gas after passing through the second dry dust collector is 8 mg / Nm³. 3 ~12mg / Nm 3 After being washed by the second scrubbing tower, the temperature of the second nitrogen gas is reduced to 35℃~45℃. After being pressurized by the second compressor, the pressure of the second nitrogen gas is 0.25MPa~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 coal gas passing through the fifth heat exchanger, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger until the temperature of the top coal 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 coal gas exchange heat in the first heat exchanger, the temperature of the total natural gas is 20°C to 30°C, which is lower than the temperature of the top coal gas after passing through the first heat exchanger, and the total natural gas exchanges heat with the top coal gas in the first heat exchanger until the temperature of the top coal 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 gas and the top coal gas exchange heat in the third heat exchanger, the temperature of the first nitrogen gas is 35°C to 45°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger, and the first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger until the temperature of the top coal gas decreases by 8°C to 30°C, and the temperature of the first nitrogen gas increases to 104°C to 150°C.

[0026] And / or, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger, and they 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 20℃~30℃, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 102℃~120℃, and the temperature of the cold pellets increases to 100℃~117℃.

[0028] And / or, before the oxygen and the second nitrogen exchange heat in the second heat exchanger, the temperature of the oxygen is 35°C to 45°C, which is lower than the temperature of the second nitrogen after 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 conveyed to a hydrogen-based vertical shaft furnace via a vertical conveyor belt, and the cold pellets exchange heat with the first nitrogen gas on the vertical conveyor belt. The vertical conveyor belt has multiple gas inlets for inputting the first nitrogen gas, and the multiple gas inlets are distributed along the conveying direction of the cold pellets. The amount of the first nitrogen gas input at the gas inlet closer to the hydrogen-based vertical shaft furnace is less than the amount of the first nitrogen gas input at the gas inlet farther away from the hydrogen-based vertical shaft furnace.

[0030] Optionally, the number of gas inlets is 8 to 10, and the amount of the first nitrogen gas input from the gas inlet farthest from the hydrogen-based vertical furnace to the gas inlet closest to the hydrogen-based vertical furnace decreases by 20% sequentially.

[0031] To achieve the above and other related objectives, the present invention also provides a system for waste heat recovery in a hydrogen-based vertical shaft furnace process, comprising:

[0032] A vertical belt conveyor is used to transport cold pellets, wherein the cold pellets are heat-exchanged with a first nitrogen gas on the vertical belt conveyor to obtain hot pellets.

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

[0034] An intermediate tank is connected to the hydrogen-based vertical furnace and receives the hot sponge iron discharged from the hydrogen-based vertical furnace.

[0035] A buffer tank, connected to the intermediate tank, receives the hot sponge iron discharged from the intermediate tank;

[0036] An electric furnace is connected to the buffer tank and receives the hot sponge iron discharged from the buffer tank.

[0037] A heating furnace, used for heating;

[0038] The top gas recovery unit includes a first dry dust collector, a fifth heat exchanger, a first heat exchanger, a third heat exchanger, a first scrubbing tower, a first compressor, and a decarbonization system connected in sequence. The first dry dust collector is connected to the hydrogen-based vertical furnace, and the output end of the decarbonization system is connected to the fifth heat exchanger and the heating furnace, respectively.

[0039] A converter, connected to the hydrogen-based vertical furnace, is used for a second natural gas and oxygen conversion process to obtain a first reducing gas fed into the hydrogen-based vertical furnace;

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

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

[0042] Optionally, the discharge end of the vertical conveyor belt is located near the end of the hydrogen-based vertical furnace, and the discharge end of the vertical conveyor belt, 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 waste heat recovery in the hydrogen-based vertical furnace process of the present invention have at least the following beneficial effects:

[0044] 1) It realizes the recovery of heat in the high-temperature section of the top gas, 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) It realizes the heat recovery of the second nitrogen gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of hydrogen-based shaft furnace by about 0.41% to 0.6%;

[0046] 3) In the first heat exchanger, part of the heat from the top gas is exchanged to the total natural gas. On the one hand, this can increase the temperature of the high-temperature carburizing gas, reduce the temperature drop of the first and second reducing gases, and improve the carburizing effect, so that the DRI carburizing amount can be increased by about 0.8% to 1.05%. On the other hand, it can increase the temperature of the second natural gas entering the converter, so that the consumption of the second natural gas and oxygen in the converter can be reduced by 4.7% to 7.3%.

[0047] 4) The first nitrogen gas absorbs part of the heat from the top coal gas and part of the heat from the second nitrogen gas in sequence through the third and fourth heat exchangers. 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 pellets sticking together and being difficult to discharge.

[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 converter, thereby reducing the second natural gas consumption and oxygen consumption of the converter by 1.4% to 2.2%.

[0049] In summary, this invention fully recovers and utilizes the heat from top coal gas and hot pellets, solving the problem of sensible heat waste in hydrogen-based vertical shaft furnace processes. It is of great significance for reducing energy consumption and CO2 emissions in hydrogen-based vertical shaft furnace processes. Attached Figure Description

[0050] Figure 1 The diagram shown is a simplified structural schematic of an embodiment of a system for waste heat recovery in a hydrogen-based vertical furnace process according to the present invention.

[0051] Part Number Explanation

[0052] Hydrogen-based vertical shaft 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 scrubbing tower 35, the... A press 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 conversion furnace 5, a second dry dust collector 61, a fourth heat exchanger 62, a second heat exchanger 63, an oxygen pipeline 631, a second scrubbing tower 64, a second press 65, a buffer tank 7, a second nitrogen pipeline 71, an electric furnace 8, a vertical conveyor belt 91, a feed end 911, a discharge end 912, a gas inlet 913, and a top dust collector 92. Detailed Implementation

[0053] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show components relevant to the present invention and are not drawn according to the actual number, shape, and size of components in implementation. In actual implementation, the form, quantity, and proportion of each component can be arbitrarily changed, and the component layout may be more complex. The structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effects and objectives of the present invention, should still fall within the scope of the technical content disclosed in the present invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are only for clarity of description and are not intended to limit the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0055] Before describing the embodiments of the present invention in detail, the application environment of the present invention will be described first. The technology of the present invention is mainly applied to the field of hydrogen-based shaft furnaces, especially to the reduction of hot pellets in hydrogen-based shaft furnaces. The present invention solves the problem of low sensible heat recovery and utilization rate of top gas and hot sponge iron generated during the reduction of hot pellets in hydrogen-based shaft furnaces. Therefore, the present invention recovers the sensible heat of top gas and hot sponge iron, and uses the sensible heat of top gas and hot sponge iron to heat the cold pellets, oxygen, and total natural gas required in the hydrogen-based shaft furnace process, which is beneficial to reducing energy consumption and CO2 emissions.

[0056] See Figure 1In an optional embodiment, the present invention provides a method for waste heat recovery in a hydrogen-based vertical shaft furnace process, comprising: heating total natural gas; passing the total natural gas through a first heat exchanger 33 to obtain first natural gas and second natural gas; the first natural gas being formed into high-temperature carburizing gas; the increase in the temperature of the total natural gas is beneficial to increasing the temperature of the first natural gas, thereby beneficial to increasing the temperature of the high-temperature carburizing gas entering the hydrogen-based vertical shaft furnace 1, increasing the sensible heat entering the furnace; converting the second natural gas and oxygen that have been heated by the second heat exchanger 63 in a conversion furnace 5 to obtain first reducing gas; and sequentially passing the first nitrogen gas through a third heat exchanger 34 for one heat exchange to increase its temperature. After secondary heat exchange in the fourth heat exchanger 62, the ore is heated and then exchanged with 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 shaft furnace 1, where the hot pellets are reduced and carburized to obtain hot sponge iron and top coal gas. The top coal gas is then passed sequentially through 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 scrubbing tower 35 for washing, the first pressurizer 36 for pressurization, and the decarbonization system 37 for decarbonization to obtain total decarbonized gas. A portion of the total decarbonized gas forms the first decarbonization gas. The carbon gas is partially converted into a second decarburized gas. The first decarburized gas is then heated by passing it through a fifth heat exchanger 32 and a heating furnace 4 to obtain a second reducing gas that is injected back into the hydrogen-based vertical shaft furnace 1. This allows the second reducing gas to absorb and utilize the heat released by the top coal gas in the fifth heat exchanger 32. The second decarburized gas is then burned to heat the heating furnace 4. In other words, the heat used by the heating furnace 4 to heat the first decarburized gas comes at least partially from the heat obtained from the combustion of the second decarburized gas. The hot sponge iron is then transported to an intermediate tank 2, and the hot sponge iron in the intermediate tank 2 is transported to a buffer tank 7 connected to the electric furnace 8 via a second nitrogen gas. The second nitrogen gas is then transferred from the buffer tank 7 to the buffer tank 7. The wastewater discharged from 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 scrubbing tower 64 for washing, and the second pressurizer 65 for pressurization before being circulated back to the hot sponge iron in 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 recovery and utilization of the sensible heat of the hot sponge iron. The heated oxygen and the second natural gas are converted in the converter 5, which helps to reduce the heat required for the conversion of the second natural gas and helps to reduce energy consumption.

[0057] In the above embodiment of the waste heat recovery method for hydrogen-based vertical shaft furnace process, both the top coal gas and the second nitrogen gas that has absorbed the heat from the hot sponge iron are subjected to dry dust removal, so that the heat loss of the top coal gas and the second nitrogen gas after dust removal is less, so as to recover and utilize the heat. Based on this, the top coal 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, total natural gas and the first nitrogen gas. The second nitrogen gas is heat-exchanged through the fourth heat exchanger 62 and the second heat exchanger 63 to heat the first nitrogen gas and oxygen gas. This fully utilizes the heat transferred from the top coal gas and the hot sponge iron to the second nitrogen gas, which is beneficial to reducing energy consumption.

[0058] See Figure 1 In one optional embodiment, the hot pellets are fed from the top, the hot sponge iron is discharged from the bottom, and the first and second reducing gases are fed from the middle and discharged from the top. The flow direction of the pellets and the reducing gas is opposite, forming a counter-current, which increases the gas-solid contact area, improves the reaction efficiency and heat exchange efficiency, and increases the metallization rate by 5% to 10%.

[0059] See 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 a hydrogen-based vertical shaft furnace, which makes full use of the unused reducing gas in the top coal gas, thereby reducing the consumption of the second natural gas by 50% to 70%.

[0060] Optionally, 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, while the content of N2, CO2, and H2O is less than or equal to 10%. This increases the content of reducing gases and decreases the content of oxidizing and inert gases in the total reducing gas, thereby improving its reducing capacity. The CH4 content being less than or equal to 10% ensures that the decrease in the temperature of the total reducing gas caused by the in-situ reforming reaction of CH4 with H2O and CO2 under the catalysis of hot sponge iron is controlled within 10%.

[0061] Optionally, the temperature of the total reducing gas is 850℃~1050℃, and the pressure of the total reducing gas is 0.25MPa~0.55MPa. Further, the temperature of the total reducing gas can be any value from 850℃, 900℃, 950℃, 1000℃, or 1050℃; and the pressure of the total reducing gas can be any value from 0.25MPa, 0.3MPa, 0.4MPa, 0.5MPa, or 0.55MPa.

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

[0063] Optionally, the temperature of the hot sponge iron can be any value among 650℃, 700℃, 750℃, 780℃ or 800℃.

[0064] See Figure 1 In one optional embodiment, the temperature of the hot pellets is 100°C to 117°C, and the flow rate of the first nitrogen gas is 300 Nm³. 3 / tDRI~700Nm 3 / tDRI.

[0065] Optionally, the temperature of the hot pellets can be any value among 100℃, 107℃, 110℃, or 117℃, and the flow rate of the first nitrogen gas can be 300 Nm³. 3 / tDRI, 400Nm 3 / tDRI、500Nm 3 / tDRI、600Nm 3 / tDRI or 700Nm 3 Any value among / tDRI and other values.

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

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

[0068] See Figure 1 In an optional embodiment, the dust content of the second nitrogen gas after passing through the second dry dust collector 61 is 8 mg / Nm³. 3 ~12mg / Nm 3 For example, it can be 8mg / Nm 3 9mg / Nm 3 10mg / Nm 3 11mg / Nm 3 Or 12mg / Nm 3The temperature of the second nitrogen gas after passing through the second dry dust collector 61 is 430℃~450℃; after being washed by the second scrubbing tower 64, the temperature of the second nitrogen gas is reduced to 35℃~45℃, for example, any one of the values ​​of 35℃, 38℃, 40℃, 42℃ or 45℃; after being pressurized by the second pressurizer 65, the pressure of the second nitrogen gas is 0.25MPa~0.55MPa, for example, any one of the values ​​of 0.25MPa, 0.3MPa, 0.4MPa, 0.5MPa or 0.55MPa.

[0069] Specifically, in this embodiment, after the second nitrogen gas passes through the second dry dust collector 61, the dust content is reduced to 10 mg / Nm³. 3 After the second nitrogen gas is washed in the second scrubbing tower 64, its temperature is reduced to 40°C. After being pressurized by the second pressurizer 65, the pressure of the second nitrogen gas is 0.25MPa~0.55MPa.

[0070] See 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, 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 coal gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger 32 until the temperature of the top coal gas decreases by 153°C to 150°C, for example, any value among 153°C, 151°C, or 150°C; the temperature of the first decarbonized gas increases by 270°C to 329°C, for example, any value among 270°C, 300°C, 310°C, 320°C, or 329°C.

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

[0072] See Figure 1In one optional embodiment, before the total natural gas and top coal gas exchange heat with each other in the first heat exchanger 33, the temperature of the total natural gas is 20°C to 30°C, for example, any value among 20°C, 22°C, 25°C, 28°C, or 30°C. After passing through the first heat exchanger 33, the temperature of the total natural gas is lower than the temperature of the top coal gas passing through the first heat exchanger 33, and they exchange heat in the first heat exchanger 33 until the temperature of the top coal gas decreases by 23°C to 37°C, for example, any value among 23°C, 28°C, 32°C, 34°C, or 37°C, and the temperature of the total natural gas increases to 151°C to 209°C, for example, any value among 151°C, 160°C, 170°C, 190°C, or 209°C. This results in an increase of 0.8% to 1.05% in the carbon content of the hot sponge iron in the hydrogen-based shaft furnace, and a decrease of 4.7% to 7.3% in the second natural gas consumption and oxygen consumption of the converter.

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

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

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

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

[0077] See Figure 1In one optional embodiment, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat in the fourth heat exchanger 62 until the temperature of the second nitrogen gas decreases by 244°C to 160°C, for example, it can be any value among 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, it can be any value among 176°C, 200°C, 220°C, 240°C or 260°C.

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

[0079] See Figure 1 In one optional embodiment, before the cold pellets exchange heat with the first nitrogen gas, the cold pellets are at room temperature. The temperature of the cold pellets can be 20℃ to 30℃, for example, any value among 20℃, 22℃, 25℃, 28℃, or 30℃. The temperature of the cold pellets is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 102℃ to 120℃, for example, any value among 102℃, 105℃, 110℃, or 120℃. The temperature of the cold pellets increases to 100℃ to 117℃, for example, any value among 100℃, 105℃, 110℃, or 117℃. After the temperature of the cold pellets increases, the liquid water carried by them evaporates as water vapor.

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

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

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

[0083] See Figure 1 In one optional embodiment, cold pellets are conveyed to the hydrogen-based vertical shaft furnace 1 via a vertical conveyor belt 91, and the cold pellets exchange heat with the first nitrogen gas on the vertical conveyor belt 91. Hot pellets are generally buffered in a storage tank before being added to the hydrogen-based vertical shaft furnace 1. The vertical conveyor belt 91 conveys the hot pellets to the storage tank. When hot pellets need to be added, they are added to the hydrogen-based vertical shaft furnace 1. Heating the cold pellets results in hot pellets, which have reduced viscosity, thus reducing the risk of the hot pellets sticking to the tank wall and improving the smoothness and reliability of the feeding process.

[0084] Optionally, the vertical tape machine 91 is a semi-enclosed vertical tape machine 91.

[0085] Optionally, the vertical conveyor belt 91 has multiple gas inlet positions 913 for inputting first nitrogen gas. These gas inlet positions 913 are distributed along the conveying direction of the cold pellets, and the amount of first nitrogen gas input at the gas inlet position 913 closest to the hydrogen-based vertical furnace 1 is less than the amount input at the gas inlet position 913 furthest from the hydrogen-based vertical furnace 1. Further, the number of gas inlet positions 913 is 8 to 10, and the amount of first nitrogen gas input at the gas inlet positions 913 furthest from the hydrogen-based vertical furnace 1 to closest to the hydrogen-based vertical furnace 1 decreases by 20% sequentially. Specifically, the vertical belt conveyor 91 has a feed end 911 and a discharge end 912. The feed end 911 is farther away from the hot pellet inlet 11 of the hydrogen-based vertical furnace 1 than the discharge end 912. The feed end 911 is equipped with a tail pulley, and the discharge end 912 is equipped with a head pulley. Multiple gas inlet positions 913 are arranged at intervals on the vertical belt conveyor 91, located between the tail pulley and the head pulley. The vertical belt conveyor 91 transports the cold pellets to the tank. Since the flow direction of the first nitrogen gas is the same as the flow direction of the cold pellets, the first nitrogen gas input from the gas inlet position 913 far away from the hydrogen-based vertical furnace 1 will be transported along with the cold pellets through the gas inlet position 913 close to the hydrogen-based vertical furnace 1. During the transport process, the temperature of the cold pellets gradually increases. The closer the cold pellets are to the hydrogen-based vertical furnace 1, the higher the temperature, and the smaller the amount of first nitrogen gas input from the corresponding gas inlet 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 conveyor belt 91 flows upward, resulting in a "heat storage" phenomenon at the upper part of the vertical conveyor belt 91. The tiered introduction of gas can fully utilize this "heat storage" phenomenon and improve the heat exchange efficiency between the first nitrogen gas and the cold pellets.

[0086] Optionally, after exchanging heat with the cold pellets, the first nitrogen gas is drawn from the head pulley of the vertical belt conveyor 91 to the top dust collector 92 for dust removal and then discharged.

[0087] Optionally, the waste heat recovery method of any of the above embodiments of the hydrogen-based vertical shaft furnace process can be applied to the field of hydrogen-based vertical shaft furnaces.

[0088] The method for waste heat recovery in hydrogen-based vertical furnace processes is further illustrated below with specific embodiments. It should be understood that the present invention is not limited to the following embodiments.

[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. The first natural gas is formed into high-temperature carburizing gas. The second natural gas and oxygen heated by heat exchange in the second heat exchanger 63 are converted in the converter 5 to obtain the first reducing gas. The first nitrogen is heated by heat exchange in the third heat exchanger 34 for the first time and by heat exchange in the fourth heat exchanger 62 for the second time, and then heated by heat exchange with 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 shaft furnace 1, and the hot pellets are reduced and carburized in the hydrogen-based vertical shaft furnace 1 to obtain hot sponge iron and top coal gas. The top coal gas is heated by dust removal in the first dry dust collector 31, by heat exchange in the fifth heat exchanger 32 for the first time, by heat exchange in the first heat exchanger 33 for the second time, by heat exchange in the third heat exchanger 34 for the third time, and by the first... The system consists of a washing tower 35 for washing, a first pressurizer 36 for pressurization, and a decarbonization system 37 for decarbonization to obtain total decarbonized gas. Part of the total decarbonized gas is formed as first decarbonized gas, and the other part is formed as second decarbonized gas. The first decarbonized gas is then passed through a fifth heat exchanger 32 for heat exchange and heating furnace 4 for heating to obtain second reducing gas that is injected back into the hydrogen-based vertical furnace 1. The second decarbonized gas is then burned to heat the furnace 4. The hot sponge iron is then transported to an intermediate tank 2, and the hot sponge iron in the intermediate tank 2 is transported to a buffer tank 7 connected to an electric furnace 8 by a second nitrogen gas. The second nitrogen gas is discharged from the buffer tank 7 and passes through a second dry dust collector 61 for dust removal, a fourth heat exchanger 62 for primary heat exchange and cooling, a second heat exchanger 63 for secondary heat exchange and cooling, a second washing tower 64 for washing, and a second pressurizer 65 for pressurization before being circulated back to 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 and second reducing gases 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 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.

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

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

[0095] Furthermore, the temperature of the hot pellets is 100℃, and the flow rate of the first nitrogen gas is 300 Nm³. 3 / tDRI.

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

[0097] Furthermore, the dust content of the second nitrogen gas after passing through the second dry dust collector 61 is 10 mg / Nm³. 3 After the second nitrogen gas is washed by the second scrubbing tower 64, its temperature drops to 40°C. After the second nitrogen gas is pressurized by the second pressurizer 65, its pressure increases to 0.25MPa~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 coal gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger 32 until the temperature of the top coal 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 top coal gas exchange heat 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 coal gas after passing through the first heat exchanger 33. The total natural gas exchanges heat with the top coal gas in the first heat exchanger 33 until the temperature of the top coal gas decreases by 23°C and the temperature of the total natural gas increases to 151°C. This results in an increase of 0.8% in the carbon content of the hot sponge iron in the vertical shaft furnace, and a decrease of 4.7% in the second natural gas consumption and oxygen consumption of the converter.

[0100] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 8°C and the temperature of the first nitrogen gas increases to 113°C.

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

[0102] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 102°C, and the temperature of the cold pellets increases to 100°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0104] Furthermore, before the oxygen and the second nitrogen pass through the second heat exchanger 63, the oxygen temperature 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 exchange in the second heat exchanger 63 until the temperature of the second nitrogen drops by 86°C and the temperature of the oxygen rises to 152°C, thereby reducing the second natural gas consumption and oxygen consumption of the converter by 2.0%.

[0105] The two-stage heat exchange of the second nitrogen gas enables the recovery of heat from 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 shaft furnace by about 0.45%.

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

[0107] Example 2

[0108] The difference between this implementation and Example 1 is that the temperature of the hot pellet is 106°C and the flow rate of the first nitrogen gas is 700 Nm³. 3 / tDRI.

[0109] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 17°C and the temperature of the first nitrogen gas increases to 104°C.

[0110] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 108°C, and the temperature of the cold pellets increases to 106°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0112] Furthermore, before the oxygen and the second nitrogen exchange through the second heat exchanger 63, the oxygen temperature is 40°C, which is lower than the temperature of the second nitrogen after passing through the second heat exchanger 63. The oxygen and the second nitrogen exchange 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 consumption of the second natural gas and oxygen in the converter 5 by 1.4%.

[0113] The two-stage heat exchange of the second nitrogen gas enables the recovery of heat from the conveying gas used to transport hot sponge iron, which can effectively reduce the process energy consumption and CO2 emissions of the hydrogen-based shaft 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-state sponge iron is greater than 92%, and the temperature of the hot-state sponge iron is 730℃;

[0117] Furthermore, the temperature of the hot pellets is 100℃, and the flow rate of the first nitrogen gas is 300 Nm³. 3 / tDRI.

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

[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 coal gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger 32 until the temperature of the top coal 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 top coal gas exchange heat 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 coal gas passing through the first heat exchanger 33. The total natural gas exchanges heat with the top coal gas in the first heat exchanger 33 until the temperature of the top coal gas decreases by 28°C and the temperature of the total natural gas increases to 179°C. This results in an increase of 0.95% in the carbon content of the hot sponge iron in the hydrogen-based shaft furnace 1, and a decrease of 6.0% in the second natural gas consumption and oxygen consumption of the converter.

[0121] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 12°C and the temperature of the first nitrogen gas increases to 132°C.

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

[0123] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 102°C, and the temperature of the cold pellets increases to 100°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0125] Furthermore, before the oxygen and the second nitrogen pass through the second heat exchanger 63, the oxygen temperature 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 exchange in the second heat exchanger 63 until the temperature of the second nitrogen drops by 90°C and the temperature of the oxygen rises to 158°C, thereby reducing the second natural gas consumption and oxygen consumption of the converter by 2.2%.

[0126] The two-stage heat exchange of the second nitrogen gas enables the recovery of heat from 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 shaft furnace by about 0.45%.

[0127] Example 4

[0128] The difference between this implementation and Example 3 is that the temperature of the hot pellet is 111°C. The flow rate of the first nitrogen gas is 700 Nm³. 3 / tDRI.

[0129] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 24°C and the temperature of the first nitrogen gas increases to 120°C.

[0130] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat 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 gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 113°C, and the temperature of the cold pellets increases to 111°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0132] Furthermore, before the oxygen and the second nitrogen pass through the second heat exchanger 63, the oxygen temperature 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 exchange in 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 converter by 1.6%.

[0133] The two-stage heat exchange of the second nitrogen gas enables the recovery of heat from 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 shaft 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℃ and the pressure of the total reducing gas is 0.25MPa.

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

[0137] Furthermore, the temperature of the hot pellets is 103℃, and the flow rate of the first nitrogen gas is 300 Nm³. 3 / tDRI.

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

[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 coal gas passing through the fifth heat exchanger 32, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger 32 until the temperature of the top coal 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 top coal gas exchange heat 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 coal gas passing through the first heat exchanger 33. The total natural gas exchanges heat with the top coal gas in the first heat exchanger 33 until the temperature of the top coal gas decreases by 37°C and the temperature of the total natural gas increases to 209°C. This results in an increase of 1.05% in the carbon content of the hot sponge iron in the hydrogen-based shaft furnace 1, and a decrease of 7.3% in the second natural gas consumption and oxygen consumption of the converter.

[0141] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 15°C and the temperature of the first nitrogen gas increases to 150°C.

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

[0143] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 62, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 62, and they exchange heat 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 105°C, and the temperature of the cold pellets increases to 103°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0145] Furthermore, before the oxygen and the second nitrogen pass through the second heat exchanger 63, the oxygen temperature 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 exchange in the second heat exchanger 63 until the temperature of the second nitrogen drops by 96°C and the temperature of the oxygen rises to 164°C, thereby reducing the second natural gas consumption and oxygen consumption of the converter by 2.2%.

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

[0147] Example 6

[0148] The difference between this implementation and Example 5 is that the temperature of the hot pellet is 117°C and the flow rate of the first nitrogen gas is 700 Nm³. 3 / tDRI.

[0149] Furthermore, before the first nitrogen gas and the top coal gas exchange heat in the third heat exchanger 34, the temperature of the first nitrogen gas is 40°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger 34. The first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger 34 until the temperature of the top coal gas decreases by 30°C and the temperature of the first nitrogen gas increases to 135°C.

[0150] Furthermore, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger 34, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger 34, and they exchange heat 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 30°C, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 120°C, and the temperature of the cold pellets increases to 117°C. The water introduced into the cold pellets changes from liquid to gas and evaporates.

[0152] Furthermore, before the oxygen and the second nitrogen pass through the second heat exchanger 63, the oxygen temperature 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 exchange in the second heat exchanger 63 until the temperature of the second nitrogen drops by 69°C and the temperature of the oxygen rises to 131°C, thereby reducing the second natural gas consumption and oxygen consumption of the converter by 1.6%.

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

[0154] See Figure 1In an optional embodiment, the present invention provides a system for waste heat recovery in a hydrogen-based vertical shaft furnace process, used to implement the method for waste heat recovery in a hydrogen-based vertical shaft furnace process according to any of the above embodiments. The system includes a vertical belt conveyor 91, a hydrogen-based vertical shaft 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, which exchange heat with a first nitrogen gas on the vertical belt conveyor 91 to obtain hot pellets. A material tank is connected to the discharge end 912 of the vertical belt conveyor 91, and the vertical belt conveyor 91 transports the hot pellets to the material tank for centralized buffering. The hydrogen-based vertical shaft furnace 1 is used for the reduction and carburizing treatment of the hot pellets to obtain hot sponge iron and top gas. The intermediate tank 2 is connected to the hydrogen-based vertical shaft furnace 1 and receives the hot sponge iron discharged from the hydrogen-based vertical shaft furnace 1. The hot sponge iron can be buffered... The hot sponge iron in intermediate tank 2 is stored in intermediate tank 2; buffer tank 7 is connected to intermediate tank 2 and receives the hot sponge iron discharged from intermediate tank 2. The hot sponge iron discharged from intermediate tank 2 is transported to buffer tank 7 by pneumatic conveying; electric furnace 8 is connected to buffer tank 7 and receives the hot sponge iron discharged from buffer tank 7. The hot sponge iron in intermediate tank 2 is transported to electric furnace 8 after passing through buffer tank 7; heating furnace 4 is used for heating; top gas recovery unit includes a first dry dust collector 31, a fifth heat exchanger 32, and a first heat exchanger connected in sequence. The system comprises a heat exchanger 33, a third heat exchanger 34, a first scrubbing tower 35, a first pressurizer 36, and a decarbonization system 37. A first dry dust collector 31 is connected to the hydrogen-based vertical shaft furnace 1. The output of the decarbonization system 37 is connected to the fifth heat exchanger 32 and the heating furnace 4, respectively. A conversion furnace 5 is connected to the hydrogen-based vertical shaft furnace 1 and is used for the second natural gas and oxygen conversion treatment to obtain the first reducing gas introduced into the hydrogen-based vertical shaft furnace 1. The nitrogen recovery unit includes a second dry dust collector 61, a fourth heat exchanger 62, and a second heat exchanger connected in sequence. 63. The second scrubbing tower 64 and the second pressurizer 65, the second dry dust collector 61 and the second pressurizer 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 pipeline section 3411 connecting the second pressurizer 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 pipeline 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. After the first nitrogen gas completes heat exchange with the cold pellets, it passes through the top dust collector 92 for dust removal and is then discharged.

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

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

[0158] Optionally, the discharge end 912 of the vertical conveyor belt 91 is located near the hydrogen-based vertical furnace 1 and the material tank. The material tank and the hydrogen-based vertical furnace 1 are arranged vertically from top to bottom. The discharge end 912 of the vertical conveyor belt 91, the hydrogen-based vertical furnace 1, and the intermediate tank 2 are arranged vertically from top to bottom. This allows the hot pellets in the vertical conveyor belt 91 or the material tank to be transported into the hydrogen-based vertical furnace 1 under their own gravity. The hot sponge iron in the hydrogen-based vertical furnace 1 can be transported into the intermediate tank 2 under its own gravity. No additional conveying equipment is required, which helps to reduce energy consumption. The buffer tank 7 and the electric furnace 8 are arranged vertically from top to bottom. The hot sponge iron in the intermediate tank 2 can be transported into the electric furnace 8 under its own gravity. No additional conveying equipment is required, which helps to reduce energy consumption.

[0159] See Figure 1In one specific embodiment, hot pellets are added to the hydrogen-based shaft furnace 1 through the hot pellet inlet 11. The furnace undergoes reduction and carburizing treatment to generate hot sponge iron and top coal gas. The top coal gas passes sequentially through a first dry dust collector 31, a fifth heat exchanger 32, a first heat exchanger 33, a third heat exchanger 34, a first scrubbing tower 35, a first pressurizer 36, and a decarbonization system 37 to obtain total decarbonization gas and desorbed gas. The desorbed gas is discharged through the desorbed gas pipeline 373. The total decarbonization gas is divided into first decarbonization gas and second decarbonization gas. The first decarbonization gas passes through the first decarbonization gas pipeline 371 through the fifth heat exchanger 32, exchanges heat with the top coal gas passing through the fifth heat exchanger 32, and then enters the heating furnace 4 for heating to form second reducing gas. This second reducing gas is injected into the hydrogen-based shaft furnace 1 through the reducing gas inlet 13. The second decarbonization gas is transported to the heating furnace 4 through the second decarbonization gas pipeline 372 for combustion to provide heat for heating the furnace 4. The first heat exchanger 33 is connected to the natural gas network via the main natural gas pipeline 331. The pressure of the main natural gas is 0.5 MPa. After the main natural gas passes through the first heat exchanger 33 and exchanges heat with the top coal gas, it is divided into first natural gas and second natural gas. The first natural gas and second natural gas are respectively transported 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 the oxygen pipeline 631. The pressure of the oxygen is 0.6 MPa. After the oxygen passes through the second heat exchanger 63 and exchanges heat with the second nitrogen, it is transported to the reformer 5 and converted with the second natural gas to obtain the first reducing gas. The first reducing gas is injected into the hydrogen-based vertical shaft furnace 1 from the reducing gas inlet 13. Hot sponge iron is discharged from hot sponge iron outlet 15 to intermediate tank 2, and then transported to buffer tank 7 and then into electric furnace 8 through second nitrogen in second nitrogen pipeline 71. During the process of transporting hot sponge iron to buffer tank 7, the second nitrogen absorbs heat from the hot sponge iron. After completing the transport of hot sponge iron, the second nitrogen is discharged from buffer tank 7 and passes through second dry dust collector 61, fourth heat exchanger 62, second heat exchanger 63, second scrubbing tower 64 and second pressurizer 65 in sequence before circulating back to intermediate tank 2 to transport hot sponge iron to buffer tank 7. The heat absorbed by the second nitrogen from the hot sponge iron is used for heat exchange with first nitrogen in fourth heat exchanger 62 and for heat exchange with oxygen in second heat exchanger 63, making full use of the heat absorbed by the second nitrogen from the hot sponge iron.

[0160] Optionally, the waste heat recovery system of any of the above embodiments of the hydrogen-based vertical shaft furnace process is applied in the field of hydrogen-based vertical shaft furnaces.

[0161] The method and system for waste heat recovery in a hydrogen-based vertical shaft furnace process of the present invention fully recovers and utilizes the sensible heat of the top coal gas and the second nitrogen gas that has absorbed the heat of hot sponge iron. Specifically, the top coal gas generated during the reduction process of hot pellets has a large amount of sensible heat after passing through a first dry dust removal process. The sensible heat of the top coal gas is recovered and reused in the reduction process of hot pellets. The top coal gas undergoes staged heat exchange through multiple heat exchangers, which can not only fully realize the recovery and utilization of heat, but also meet the different heat requirements of each process. The second nitrogen gas that has absorbed the heat of hot sponge iron has a large amount of sensible heat after passing through 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 is used for heating cold pellets and oxygen, further improving the recovery and utilization of sensible heat. This is beneficial to reducing the process energy consumption of the hydrogen-based vertical shaft furnace in the production of hot sponge iron, and is of great significance for reducing CO2 emissions.

[0162] In the description of this specification, the references to terms such as "this embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above 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 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 invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for waste heat recovery in a hydrogen-based vertical shaft furnace process, characterized in that, include: The total natural gas is heated by passing it through a first heat exchanger to obtain first natural gas and second natural gas. The first natural gas is formed as high-temperature carburized gas. The second natural gas and oxygen, which have been heated by heat exchange in the second heat exchanger, are converted in a converter to obtain the first reducing gas. The first nitrogen gas is heated by passing through the third heat exchanger once and the fourth heat exchanger twice, and then heats the cold pellets to obtain hot pellets. The hot pellets, the first reducing gas, and the high-temperature carburizing gas are added to a hydrogen-based vertical shaft furnace, and the hot pellets are reduced and carburized in the hydrogen-based vertical shaft furnace to obtain hot sponge iron and top coal gas. The top coal gas is sequentially passed through a first dry dust collector for dust removal, a fifth heat exchanger for primary heat exchange and cooling, a first heat exchanger for secondary heat exchange and cooling, a third heat exchanger for tertiary heat exchange and cooling, a first scrubbing tower for washing, a first pressurizer for pressurization, and a decarbonization system for decarbonization to obtain total decarbonized gas. A portion of the total decarbonized gas is formed as first decarbonized gas, and another portion is formed as second decarbonized gas. The first decarbonized gas is sequentially heated by the fifth heat exchanger and heated by the furnace to obtain the second reducing gas that is injected back into the hydrogen-based vertical furnace; the second decarbonized gas is then burned to heat the furnace. The hot sponge iron is transported to an intermediate tank, and then transported to a buffer tank connected to an electric furnace by 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 pressurization before being circulated back to the hot sponge iron in the intermediate tank.

2. The method for waste heat recovery in a hydrogen-based vertical shaft furnace process according to claim 1, characterized in that, The hot pellets are fed from the top, the hot sponge iron is discharged from the bottom, and the first and second reducing gases are fed from the middle and discharged from the top.

3. The method for waste heat recovery in a hydrogen-based vertical 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 then introduced into the hydrogen-based vertical furnace; The total reducing gas is composed of CO, H2, N2, CO2, H2O and CH4, wherein 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℃~1050℃, and the pressure of the total reducing gas is 0.25MPa~0.55MPa.

4. The method for waste heat recovery in a hydrogen-based vertical shaft furnace process according to claim 1, characterized in that, The metallization rate of the hot-state sponge iron is greater than 92%, and the temperature of the hot-state sponge iron is 650℃~800℃. And / or, the temperature of the hot pellet is 100℃~117℃, and the flow rate of the first nitrogen gas is 300Nm³. 3 / tDRI~700Nm 3 / tDRI; And / or, the temperature of the top gas is 395℃~455℃, and the pressure of the top gas is 0.15MPa~0.45MPa.

5. The method for waste heat recovery in a hydrogen-based vertical shaft furnace process according to claim 1, characterized in that, The dust content of the second nitrogen gas after passing through the second dry dust collector is 8 mg / Nm³. 3 ~12mg / Nm 3 After being washed by the second scrubbing tower, the temperature of the second nitrogen gas is reduced to 35℃~45℃. After being pressurized by the second compressor, the pressure of the second nitrogen gas is 0.25MPa~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 coal gas passing through the fifth heat exchanger, and the first decarbonized gas and the top coal gas exchange heat in the fifth heat exchanger until the temperature of the top coal 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 coal gas exchange heat in the first heat exchanger, the temperature of the total natural gas is 20°C to 30°C, which is lower than the temperature of the top coal gas after passing through the first heat exchanger, and the total natural gas exchanges heat with the top coal gas in the first heat exchanger until the temperature of the top coal 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 gas and the top coal gas exchange heat in the third heat exchanger, the temperature of the first nitrogen gas is 35°C to 45°C, which is lower than the temperature of the top coal gas after passing through the third heat exchanger, and the first nitrogen gas exchanges heat with the top coal gas in the third heat exchanger until the temperature of the top coal gas decreases by 8°C to 30°C, and the temperature of the first nitrogen gas increases to 104°C to 150°C. And / or, before the second nitrogen gas and the first nitrogen gas exchange heat in the fourth heat exchanger, the temperature of the second nitrogen gas is higher than the temperature of the first nitrogen gas after passing through the fourth heat exchanger, and they 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 exchange heat with the first nitrogen gas, the temperature of the cold pellets is 20℃~30℃, which is lower than the temperature of the first nitrogen gas. After the cold pellets exchange heat with the first nitrogen gas, the temperature of the first nitrogen gas decreases to 102℃~120℃, and the temperature of the cold pellets increases to 100℃~117℃. And / or, before the oxygen and the second nitrogen exchange heat in the second heat exchanger, the temperature of the oxygen is 35°C to 45°C, which is lower than the temperature of the second nitrogen after 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 waste heat recovery in a hydrogen-based vertical shaft furnace process according to claim 1, characterized in that, The cold pellets are conveyed to the hydrogen-based vertical shaft furnace via a vertical conveyor belt, and the cold pellets exchange heat with the first nitrogen gas on the vertical conveyor belt. The vertical conveyor belt has multiple gas inlets for inputting the first nitrogen gas, and the multiple gas inlets are distributed along the conveying direction of the cold pellets. The amount of the first nitrogen gas input at the gas inlet closer to the hydrogen-based vertical shaft furnace is less than the amount of the first nitrogen gas input at the gas inlet farther away from the hydrogen-based vertical shaft furnace.

7. The method for waste heat recovery in a hydrogen-based vertical shaft furnace process according to claim 6, characterized in that, The number of gas inlets is 8 to 10, and the amount of the first nitrogen gas input from the gas inlet farthest from the hydrogen-based vertical furnace to the gas inlet closest to the hydrogen-based vertical furnace decreases by 20% sequentially.

8. A system for waste heat recovery in a hydrogen-based vertical shaft furnace process, characterized in that, include: A vertical belt conveyor is used to transport cold pellets, wherein the cold pellets are heat-exchanged with a first nitrogen gas on the vertical belt conveyor to obtain hot pellets. Hydrogen-based vertical shaft furnace, used for hot pellet reduction and carburizing treatment to obtain hot sponge iron and top gas; An intermediate tank is connected to the hydrogen-based vertical furnace and receives the hot sponge iron discharged from the hydrogen-based vertical furnace. A buffer tank, connected to the intermediate tank, receives the hot sponge iron discharged from the intermediate tank; An electric furnace is connected to the buffer tank and receives the hot sponge iron discharged from the buffer tank. A heating furnace, used for heating; The top gas recovery unit includes a first dry dust collector, a fifth heat exchanger, a first heat exchanger, a third heat exchanger, a first scrubbing tower, a first compressor, and a decarbonization system connected in sequence. The first dry dust collector is connected to the hydrogen-based vertical furnace, and the output end of the decarbonization system is connected to the fifth heat exchanger and the heating furnace, respectively. A converter, connected to the hydrogen-based vertical furnace, is used for a second natural gas and oxygen conversion process to obtain a first reducing gas fed into the hydrogen-based vertical furnace; The nitrogen recovery unit includes a second dry dust collector, a fourth heat exchanger, a second heat exchanger, a second scrubbing tower, and a second pressurizer connected in sequence. The second dry dust collector and the second pressurizer are respectively connected to the buffer tank to form a nitrogen circulation loop. A first pipeline section connecting the second pressurizer and the buffer tank is also connected to the intermediate tank to transport the hot sponge iron. The fourth heat exchanger is connected to a second pipeline section for transporting the first nitrogen, and the second heat exchanger is connected to an oxygen pipeline for transporting the oxygen.

9. The system for waste heat recovery in a hydrogen-based vertical furnace process according to claim 8, characterized in that, The top of the hydrogen-based vertical shaft furnace is provided with a hot pellet inlet and a top gas outlet. The top gas outlet is connected to the first dry dust collector. The middle part of the hydrogen-based vertical shaft 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. The lower part of the hydrogen-based vertical shaft furnace is provided with a hot sponge iron outlet. The intermediate tank is connected to the hot sponge iron outlet.

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

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