Gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking

Abstract

The application provides a gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking, which comprises the following steps: introducing cooling hydrogen into the lower part of a cooling zone in a circumferential spraying manner and leading out cooling tail gas generated after heat exchange from the upper part of the cooling zone to form a first-stage gradient gas distribution; introducing first high-temperature reduction hydrogen into the lower part of a high-temperature reduction zone in a circumferential spraying manner to form a second-stage gradient gas distribution; introducing second high-temperature reduction hydrogen into the middle and upper part of the high-temperature reduction zone in a circumferential spraying manner to form a third-stage gradient gas distribution; introducing preheated hydrogen into a preheating reduction zone in a circumferential spraying manner to form a fourth-stage gradient gas distribution; and taking the cooling tail gas generated in the first-stage gradient gas distribution as a gas source for at least one of the second-stage gradient gas distribution, the third-stage gradient gas distribution and the fourth-stage gradient gas distribution. The application can solve the problems of uneven distribution of hydrogen, large fluctuation of reduction atmosphere and temperature field and low energy utilization efficiency in the current hydrogen-based reduction process.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking technology, and in particular to a gradient gas distribution and multi-stage utilization method for hydrogen-rich direct reduction ironmaking. Background Technology

[0002] Against the backdrop of the global steel industry's accelerated green and low-carbon transformation, hydrogen-based direct reduction technology has become a key development direction due to its significant carbon emission reduction potential. Pure hydrogen, as a reducing agent, can completely avoid carbon dioxide emissions during ironmaking, making it one of the core pathways for future zero-carbon steel production. With the continuous decline in the cost of hydrogen production from renewable energy sources and the ongoing improvement of hydrogen energy infrastructure, hydrogen-rich direct reduction processes are gradually moving from experimental research to industrial application.

[0003] However, existing hydrogen metallurgical technologies, especially in terms of gas inlet structure and comprehensive energy utilization, still have significant limitations. Most current processes employ single-point or localized gas inlet modes, leading to uneven hydrogen distribution within the furnace, poor stability of the reducing atmosphere, and large temperature fluctuations. These problems severely affect the efficiency of heat and mass transfer between the gas and solid phases, resulting in low metallization rates, long reduction cycles, and excessively high hydrogen consumption per ton of iron. Particularly in large vertical shaft furnaces, uneven gas distribution easily creates flow dead zones and concentration polarization, further reducing reaction efficiency.

[0004] Furthermore, existing technologies generally fall short in recovering and utilizing waste heat from cooling exhaust gases. A significant amount of medium- and low-temperature thermal energy is wasted without being efficiently utilized in a cascade manner, resulting in energy waste and increased system operating costs. The degree of exhaust gas purification and recycling is low, and an economical, efficient, and closed-loop hydrogen resource utilization pathway has not yet been established.

[0005] Therefore, there is an urgent need for a method for hydrogen-rich metallurgical gas distribution and waste heat utilization that can be systematically optimized in terms of gas intake organization, atmosphere control, thermal management and gas circulation, so as to achieve the goals of uniform gas distribution in the furnace, efficient and stable reduction reaction, and maximization of comprehensive energy utilization, and promote the development of hydrogen-based direct reduction technology towards true industrialization, low energy consumption and high efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a gradient gas distribution and multi-stage waste heat utilization method for direct reduction ironmaking with hydrogen-rich materials, which solves the problems of uneven hydrogen distribution, large fluctuations in reducing atmosphere and temperature field, and low energy utilization efficiency in current hydrogen-based reduction processes. Through the synergistic effect of four-stage gradient gas distribution and uniform circumferential injection, the reduction efficiency and energy utilization level of iron-containing furnace charge are improved.

[0007] The above-mentioned technical objectives of the present invention are mainly achieved through the following technical solutions.

[0008] This invention provides a gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking, realizing gas distribution and waste heat recovery and utilization among the preheating reduction zone, high-temperature reduction zone, constant pressure zone and cooling zone arranged sequentially from top to bottom in a vertical shaft furnace. The gradient gas distribution and multi-stage waste heat utilization method includes: Cooling hydrogen is introduced into the lower part of the cooling zone in a circumferential jet to cool the generated direct reduced iron, and the cooling exhaust gas generated after heat exchange is discharged from the upper part of the cooling zone to form a first-stage gradient gas distribution. The first high-temperature reducing hydrogen gas is introduced into the lower part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a second-stage gradient gas distribution. The second high-temperature reducing hydrogen gas is introduced into the upper middle part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a third-level gradient gas distribution. Preheated hydrogen gas is introduced into the preheating reduction zone in a circumferential injection manner to preheat the furnace charge, thereby forming a fourth-level gradient gas distribution. The cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for at least one of the second-stage gradient gas distribution, the third-stage gradient gas distribution, and the fourth-stage gradient gas distribution.

[0009] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas from the furnace top, and then introduced into the lower part of the high-temperature reduction zone after dust removal, dehydration, pressurization, purification and heating treatment.

[0010] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the third-stage gradient gas distribution, the cooling exhaust gas is introduced into the upper middle part of the high-temperature reduction zone after dust removal and heating treatment.

[0011] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the fourth-stage gradient gas distribution, the cooling exhaust gas is introduced into the preheating reduction zone after dust removal treatment.

[0012] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution and the third-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas at the top of the furnace, and after being treated by dust removal, dehydration, pressurization, purification and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and heating and then introduced into the middle and upper part of the high-temperature reduction zone.

[0013] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution and the fourth-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas at the top of the furnace, and after being treated by dust removal, dehydration, pressurization, purification and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and then introduced into the preheating reduction zone.

[0014] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the third-stage and fourth-stage gradient gas distribution, the cooling exhaust gas is introduced into the upper middle part of the high-temperature reduction zone after being treated by dust removal and heating, and at the same time, the cooling exhaust gas is introduced into the preheating reduction zone after being treated by dust removal.

[0015] In a preferred embodiment of the present invention, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution, the third-stage gradient gas distribution, and the fourth-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas from the furnace top, and after being treated by dust removal, dehydration, pressurization, purification, and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and heating and then introduced into the upper middle part of the high-temperature reduction zone. Simultaneously, the cooling exhaust gas is treated by dust removal and then introduced into the preheating reduction zone.

[0016] In a preferred embodiment of the present invention, after the cooling exhaust gas and the flue gas from the furnace top are mixed, a heat exchanger is used to exchange heat between the gas before dust removal and the purified gas.

[0017] In a preferred embodiment of the present invention, the temperature of the cooling hydrogen gas introduced into the cooling zone is room temperature; the temperature of the first high-temperature reducing hydrogen gas and the second high-temperature reducing hydrogen gas introduced into the high-temperature reducing zone is 950°C to 1050°C; and the temperature of the preheating hydrogen gas introduced into the preheating reducing zone is 400°C to 750°C.

[0018] Compared with the prior art, the technical solution of the present invention has the following characteristics and advantages: The gradient gas distribution and multi-stage utilization of waste heat method for direct reduction ironmaking with hydrogen-rich gas described in this invention significantly improves the reduction efficiency and energy utilization level of iron-containing raw materials by integrating a four-stage gradient gas distribution, uniformly distributed circumferential injection gas inlet and multi-stage utilization of cooling tail gas.

[0019] First, the four-stage gradient gas distribution method achieves a scientific distribution of hydrogen along the axial direction in the furnace by setting gas distribution points in different functional areas along the vertical furnace axis. This strengthens the thermodynamic and kinetic conditions of the gas-solid countercurrent reaction, which helps to improve the metallization rate while reducing hydrogen consumption per ton of iron.

[0020] Secondly, the use of a circumferentially uniformly arranged injection gas intake system achieves uniform distribution of hydrogen in the furnace, improves heat and mass transfer efficiency, eliminates local concentration deviations, and thus enhances reaction uniformity and operational stability.

[0021] Finally, the multi-stage utilization process for cooling exhaust gas achieves tiered heat recovery and gas circulation through multiple pathways, using waste heat for regional supplementary heating, raw material preheating, and gas heat exchange, significantly reducing external energy input and improving system thermal efficiency. This process, in synergy with gradient gas distribution, constructs a hydrogen complementary cycle and graded thermal energy utilization system, comprehensively improving hydrogen energy utilization, production efficiency, and economic benefits.

[0022] In summary, this invention solves the problems of uneven hydrogen distribution, large fluctuations in reducing atmosphere and temperature field, and low waste heat utilization, providing reliable methodological support for achieving efficient, stable, and low-carbon operation of hydrogen-rich metallurgical processes. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0024] Figure 1 This is a process flow diagram of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking as described in this invention. Figure 2 This is a process flow diagram of the first embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to the present invention. Figure 3 This is a process flow diagram of the second embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to the present invention. Figure 4 This is a process flow diagram of the third embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking described in this invention. Figure 5 This is a process flow diagram of the fourth embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking described in this invention. Figure 6 This is a process flow diagram of the fifth embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking described in this invention. Figure 7 This is a process flow diagram of the sixth embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking described in this invention. Figure 8 This is a process flow diagram of the seventh embodiment of the gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0026] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] This invention provides a gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking, realizing gas distribution and waste heat recovery and utilization among the preheating reduction zone, high-temperature reduction zone, constant pressure zone and cooling zone arranged sequentially from top to bottom in a vertical shaft furnace. The gradient gas distribution and multi-stage waste heat utilization method includes: Cooling hydrogen is introduced into the lower part of the cooling zone in a circumferential injection manner to cool the generated direct reduced iron, and the cooling exhaust gas generated after heat exchange is discharged from the upper part of the cooling zone to form the first-stage gradient gas distribution. The first high-temperature reducing hydrogen gas is introduced into the lower part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a second-stage gradient gas distribution. The second high-temperature reducing hydrogen is introduced into the upper part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a third-stage gradient gas distribution. Preheated hydrogen is introduced into the preheating reduction zone in a circumferential injection manner to preheat the furnace charge, thereby forming a fourth-stage gradient gas distribution. Specifically, the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for at least one of the second-stage, third-stage, and fourth-stage gradient gas distributions.

[0029] The gradient gas distribution and multi-stage utilization of waste heat method for direct reduction ironmaking with hydrogen-rich gas described in this invention significantly improves the reduction efficiency and energy utilization level of iron-containing raw materials by integrating a four-stage gradient gas distribution, uniform circumferential injection and multi-stage utilization of cooling tail gas.

[0030] Specifically, such as Figure 1 As shown, the interior of the vertical furnace is divided into five functional sections along the axial direction, from top to bottom: preheating reduction zone, high-temperature reduction zone, constant pressure zone, cooling zone, and discharge zone.

[0031] The core of the process method described in this invention lies in the four-stage gradient gas distribution method, which specifically includes: first-stage gradient gas distribution - lower gas distribution in the cooling zone, second-stage gradient gas distribution - lower gas distribution in the high-temperature reduction zone, third-stage gradient gas distribution - upper gas distribution in the high-temperature reduction zone, and fourth-stage gradient gas distribution - lower gas distribution in the preheating reduction zone.

[0032] First-stage gradient gas distribution: The cooling hydrogen is unheated pure hydrogen, supplied directly from the hydrogen source. A cooling gas inlet is located on the lower part of the furnace wall corresponding to the cooling zone of the vertical shaft furnace. After the furnace starts operating, cooling hydrogen is introduced into the cooling zone through this inlet, forming the first-stage gradient gas distribution in the furnace. The cooling hydrogen exchanges heat with the high-temperature direct reduced iron (DRI) generated by the reduction reaction in a countercurrent manner, carrying dust during the heating process. A cooling gas outlet is located on the upper part of the furnace wall corresponding to the cooling zone. The cooled hydrogen, after heat exchange and heating, forms cooling tail gas and is discharged from the furnace through the cooling gas outlet.

[0033] Preferably, the temperature of the cooling hydrogen introduced into the cooling zone is around room temperature (around 25°C), and the temperature of the cooling exhaust gas discharged from the cooling zone is 400°C to 750°C.

[0034] Second-stage gradient gas distribution: The vertical furnace has a reducing gas inlet on the furnace wall corresponding to the lower part of the high-temperature reduction zone. After the vertical furnace starts working, the first high-temperature reducing hydrogen is introduced into the high-temperature reduction zone through the reducing gas inlet, thereby forming a high-temperature hydrogen field in the lower and upper parts of the high-temperature reduction zone, constituting the second-stage gradient gas distribution on the vertical furnace, and participating in the gas-solid countercurrent reduction reaction process in this region.

[0035] Preferably, the temperature of the first high-temperature reducing hydrogen gas introduced into the high-temperature reduction zone is 950℃~1050℃.

[0036] Third-stage gradient gas distribution: The vertical furnace also has a reducing gas inlet on the furnace wall in the upper part of the high-temperature reduction zone. After the vertical furnace starts working, the second high-temperature reducing hydrogen is introduced into the high-temperature reduction zone through the reducing gas inlet, thereby forming a high-temperature hydrogen field in the upper part of the high-temperature reduction zone, which constitutes the third-level gradient gas distribution on the vertical furnace. This replenishes heat and reducing gas to the area, improves the metallization rate of the product, and reduces energy consumption.

[0037] Preferably, the temperature of the second high-temperature reducing hydrogen gas introduced into the high-temperature reduction zone is 950℃~1050℃.

[0038] Fourth-stage gradient gas distribution: A preheating hydrogen inlet is provided on the furnace wall corresponding to the preheating reduction zone of the vertical furnace. After the vertical furnace starts working, preheating hydrogen is introduced into the preheating reduction zone through the preheating hydrogen inlet, forming the fourth-stage gradient gas distribution on the vertical furnace. This achieves preheating and pre-reduction of the material entering the furnace, making the temperature transition between the preheating reduction zone and the high-temperature reduction zone smooth, avoiding obvious temperature fluctuations in the high-temperature reduction zone, thereby improving the reduction rate and reduction effect of the furnace charge in the vertical furnace.

[0039] Preferably, the temperature of the preheated hydrogen gas introduced into the preheating reduction zone is 400℃~750℃.

[0040] Furthermore, the process method described in this invention also includes a circumferential injection gas inlet method; this injection method is specifically applied to the process of cooling hydrogen, first high-temperature reducing hydrogen, second high-temperature reducing hydrogen and preheating hydrogen entering the vertical furnace in the four-stage gradient gas distribution.

[0041] Specifically, this circumferential gas injection method can be achieved by installing one less ring of injection pipes on the inner wall or inside the corresponding position of the vertical furnace. This uniform circumferential injection method allows for a diffuse and uniform distribution of hydrogen within the furnace, improving heat and mass transfer efficiency, shortening the reduction time of oxidized pellets, and effectively reducing hydrogen consumption per ton of iron.

[0042] Furthermore, the process method described in this invention also employs a gas circulation method to achieve multi-stage utilization of heat; that is, the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for at least one of the second-stage gradient gas distribution, the third-stage gradient gas distribution, and the fourth-stage gradient gas distribution.

[0043] In an alternative embodiment, such as Figure 2As shown, when all the cooling exhaust gas generated in the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas from the furnace top. After heat exchange and cooling, dust removal, dehydration, pressurization, purification, heat exchange and heating, it is finally reintroduced into the high-temperature reduction zone as the first high-temperature reduced hydrogen, thus forming a complete closed-loop gas cycle. The heat energy carried in the cooling exhaust gas and the flue gas from the furnace top is recovered, and the recovered heat is used to form a high-temperature reaction field in the high-temperature reduction zone.

[0044] In an alternative embodiment, such as Figure 3 As shown, when all the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the third-stage gradient gas distribution, the cooling exhaust gas is passed through dust removal and heating treatment and then introduced into the upper middle part of the high-temperature reduction zone as the second high-temperature reducing hydrogen to supplement the heat and reducing gas for the reduction reaction in this zone, which helps to improve energy utilization efficiency and reduce the overall process energy consumption. Then, it enters the preheating reduction zone with the rising gas flow and performs countercurrent heat exchange with the oxidized pellets. The gas after heat exchange becomes the furnace top flue gas, which is then processed and finally reintroduced into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0045] In an alternative embodiment, such as Figure 4 As shown, when all the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the fourth-stage gradient gas distribution, the cooling exhaust gas is treated with dust removal and then introduced into the preheating reduction zone as preheated hydrogen. During the upward movement of the gas, it exchanges heat with the downward oxidized pellets in a countercurrent manner, thereby achieving preheating and pre-reduction of the materials entering the furnace, thus reducing the system's process energy consumption. The gas after heat exchange is used as the furnace top flue gas, and after treatment, it is finally introduced back into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0046] In an alternative embodiment, such as Figure 5 As shown, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for both the second-stage and third-stage gradient gas distribution, the cooling exhaust gas is divided into two parts.

[0047] After a portion of the cooling exhaust gas is mixed with the flue gas from the furnace top, it undergoes heat exchange and cooling, dust removal, dehydration, pressurization, purification, heat exchange and heating treatments before being reintroduced into the high-temperature reduction zone as the first high-temperature reduced hydrogen gas, thus forming a complete closed-loop gas cycle.

[0048] Meanwhile, another portion of the cooled exhaust gas, after being treated by dust removal and heating, is introduced into the upper middle part of the high-temperature reduction zone as the second high-temperature reducing hydrogen to supplement the heat and reducing gas for the reduction reaction in this zone, which helps to improve energy utilization efficiency and reduce overall process energy consumption. Then, it enters the preheating reduction zone with the rising airflow and undergoes countercurrent heat exchange with the oxidized pellets. The gas after heat exchange becomes the furnace top flue gas, which, after treatment, is finally reintroduced into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0049] This embodiment enhances the reduction process in the high-temperature zone while improving the overall thermal efficiency of the system and optimizing the energy utilization structure.

[0050] In an alternative embodiment, such as Figure 6 As shown, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for both the second-stage and fourth-stage gradient gas distribution, the cooling exhaust gas is divided into two parts.

[0051] After a portion of the cooling exhaust gas is mixed with the flue gas from the furnace top, it undergoes heat exchange and cooling, dust removal, dehydration, pressurization, purification, heat exchange and heating treatments before being reintroduced into the high-temperature reduction zone as the first high-temperature reduced hydrogen gas, thus forming a complete closed-loop gas cycle.

[0052] Meanwhile, another portion of the cooling exhaust gas is treated with dust removal and then introduced into the preheating reduction zone as preheated hydrogen. As the gas moves upward, it exchanges heat with the downward-moving oxidized pellets in a countercurrent manner, thereby preheating and pre-reducing the materials entering the furnace and reducing the system's process energy consumption. The gas after heat exchange is used as flue gas at the furnace top, and after treatment, it is finally introduced back into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0053] This embodiment allows for flexible control of the proportion of gases participating in the reduction reaction and waste heat recovery, enabling proactive adjustment of the furnace's thermal balance and enhancing process controllability.

[0054] In an alternative embodiment, such as Figure 7 As shown, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for both the third-stage and fourth-stage gradient gas distribution, the cooling exhaust gas is divided into two parts.

[0055] A portion of the cooled exhaust gas is fed into the upper part of the high-temperature reduction zone after dust removal and heating treatment. It serves as the second high-temperature reducing hydrogen to supplement the heat and reducing gas for the reduction reaction in this zone, which helps to improve energy utilization efficiency and reduce the overall process energy consumption. Then, it enters the preheating reduction zone with the rising airflow and exchanges heat with the oxidized pellets in a countercurrent manner. The gas after heat exchange becomes the flue gas at the top of the furnace. After treatment, it is finally fed back into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0056] Meanwhile, another portion of the cooling exhaust gas is treated with dust removal and then introduced into the preheating reduction zone as preheated hydrogen. As the gas moves upward, it exchanges heat with the downward-moving oxidized pellets in a countercurrent manner, thereby preheating and pre-reducing the materials entering the furnace and reducing the system's process energy consumption. The gas after heat exchange is used as flue gas at the furnace top, and after treatment, it is finally introduced back into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0057] This embodiment can coordinate the gas distribution and thermal field state of different functional areas by adjusting the gas distribution ratio, thereby improving the reaction conditions in the preheating and reduction stages, increasing the metallization rate and reducing hydrogen consumption.

[0058] In an alternative embodiment, such as Figure 8 As shown, when the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage, third-stage, and fourth-stage gradient gas distribution, the cooling exhaust gas is divided into three parts.

[0059] After the first part of the cooling exhaust gas is mixed with the flue gas from the furnace top, it undergoes heat exchange and cooling, dust removal, dehydration, pressurization, purification, heat exchange and heating treatment, and is then reintroduced into the high-temperature reduction zone as the first high-temperature reduced hydrogen gas, thus forming a complete closed-loop gas cycle.

[0060] The second part of the cooling exhaust gas, after being treated by dust removal and heating, is introduced into the upper middle part of the high-temperature reduction zone as the second high-temperature reducing hydrogen to supplement the heat and reducing gas for the reduction reaction in this zone, which helps to improve energy utilization efficiency and reduce the overall process energy consumption. Then, it enters the preheating reduction zone with the rising airflow and performs countercurrent heat exchange with the oxidized pellets. The gas after heat exchange becomes the furnace top flue gas, which, after treatment, is finally reintroduced into the high-temperature reduction zone as the first high-temperature reducing hydrogen, thus forming a complete closed-loop gas cycle.

[0061] The third part of the cooling exhaust gas is treated with dust removal and then used as preheated hydrogen gas and introduced into the preheating reduction zone. During the upward movement of the gas, it exchanges heat with the downward oxidized pellets in a countercurrent manner, thereby preheating and pre-reducing the materials entering the furnace and reducing the system's process energy consumption. The gas after heat exchange is used as the furnace top flue gas. After treatment, it is finally used as the first high-temperature reducing hydrogen gas and reintroduced into the high-temperature reduction zone, thus forming a complete closed-loop gas cycle.

[0062] This embodiment comprehensively regulates the distribution of the three gases, achieving integrated control of reducing atmosphere distribution, heat replenishment, and waste heat recovery. This can improve the thermodynamic efficiency and operational economy of the process system while comprehensively optimizing the gas-solid reaction efficiency.

[0063] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking, characterized in that it realizes gas distribution and waste heat recovery and utilization between the preheating reduction zone, high-temperature reduction zone, constant pressure zone and cooling zone arranged sequentially from top to bottom in a vertical shaft furnace, and is further characterized in that... The gradient gas distribution and multi-stage waste heat utilization method includes: Cooling hydrogen is introduced into the lower part of the cooling zone in a circumferential jet to cool the generated direct reduced iron, and the cooling exhaust gas generated after heat exchange is discharged from the upper part of the cooling zone to form a first-stage gradient gas distribution. The first high-temperature reducing hydrogen gas is introduced into the lower part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a second-stage gradient gas distribution. The second high-temperature reducing hydrogen gas is introduced into the upper middle part of the high-temperature reduction zone in a circumferential injection manner to reduce the furnace charge, so as to form a third-level gradient gas distribution. Preheated hydrogen gas is introduced into the preheating reduction zone in a circumferential injection manner to preheat the furnace charge, thereby forming a fourth-level gradient gas distribution. The cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for at least one of the second-stage gradient gas distribution, the third-stage gradient gas distribution, and the fourth-stage gradient gas distribution.

2. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas from the furnace top, and then introduced into the lower part of the high-temperature reduction zone after dust removal, dehydration, pressurization, purification and heating treatment.

3. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the third-stage gradient gas distribution, the cooling exhaust gas is introduced into the upper middle part of the high-temperature reduction zone after dust removal and heating treatment.

4. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the fourth-stage gradient gas distribution, the cooling exhaust gas is introduced into the preheating reduction zone after dust removal treatment.

5. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution and the third-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas at the top of the furnace, and after being treated by dust removal, dehydration, pressurization, purification and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and heating and then introduced into the middle and upper part of the high-temperature reduction zone.

6. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution and the fourth-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas at the top of the furnace, and after being treated by dust removal, dehydration, pressurization, purification and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and then introduced into the preheating reduction zone.

7. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the third-stage and fourth-stage gradient gas distribution, the cooling exhaust gas is introduced into the upper middle part of the high-temperature reduction zone after dust removal and heating treatment, and at the same time, the cooling exhaust gas is introduced into the preheating reduction zone after dust removal treatment.

8. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, When the cooling exhaust gas generated by the first-stage gradient gas distribution is used as the gas source for the second-stage gradient gas distribution, the third-stage gradient gas distribution, and the fourth-stage gradient gas distribution, the cooling exhaust gas is mixed with the flue gas from the furnace top, and after being treated by dust removal, dehydration, pressurization, purification, and heating, it is introduced into the lower part of the high-temperature reduction zone. At the same time, the cooling exhaust gas is treated by dust removal and heating and then introduced into the upper middle part of the high-temperature reduction zone. Simultaneously, the cooling exhaust gas is treated by dust removal and then introduced into the preheating reduction zone.

9. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to any one of claims 2, 5, 6, and 8, characterized in that, After the cooling exhaust gas is mixed with the flue gas from the furnace top, a heat exchanger is used to exchange heat between the gas before dust removal and the purified gas.

10. The gradient gas distribution and multi-stage waste heat utilization method for hydrogen-rich direct reduction ironmaking according to claim 1, characterized in that, The temperature of the cooling hydrogen gas introduced into the cooling zone is room temperature; The temperature of the first high-temperature reducing hydrogen gas and the second high-temperature reducing hydrogen gas introduced into the high-temperature reduction zone is 950℃~1050℃; the temperature of the preheating hydrogen gas introduced into the preheating reduction zone is 400℃~750℃.

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