A gas preheating system for a metallurgical process gas combustion device

Abstract

This invention belongs to the field of gas preheating technology in the metallurgical industry, and relates to a gas preheating system for a coal gas combustion device in a metallurgical process. This system uses heat transfer oil as the heat medium and forms a closed-loop system at a pressure below 1.0 MPa. It includes: a flue gas heat exchanger, a preheated gas heat exchanger, a first heat medium delivery pipeline, a second heat medium delivery pipeline, and a heat medium bypass pipeline. The heat medium output end of the flue gas heat exchanger is connected to the heat medium input end of the preheated gas heat exchanger through the first heat medium delivery pipeline. The heat medium output end of the preheated gas heat exchanger is connected to the heat medium input end of the flue gas heat exchanger through the second heat medium delivery pipeline. The first heat medium delivery pipeline is connected to the second heat medium delivery pipeline through the heat medium bypass pipeline. A bypass regulating device for adjusting the oil inlet temperature of the flue gas heat exchanger is installed on the heat medium bypass pipeline. This invention solves the safety risks and control dilemmas caused by indirect water-based heat exchange when dealing with drastic fluctuations in flue gas conditions.

Description

Technical Field

[0001] This invention belongs to the field of gas preheating technology in the metallurgical industry, and particularly relates to a gas preheating system for a coal gas combustion device in a metallurgical process. Background Technology

[0002] In metallurgical production, gas combustion devices such as blast furnace hot blast stoves and blast furnace gas power generation boilers are core links in energy conversion. These devices typically use blast furnace gas, converter gas, coke oven gas, or mixtures thereof as their main fuel. Directly feeding ambient-temperature gas and combustion air into the device for combustion not only results in low combustion efficiency but also low overall thermal efficiency of the furnace process, leading to significant energy waste. To improve the thermal efficiency of gas combustion devices, the flue gas discharged from the device is typically used to preheat the gas and combustion air before they enter the device, raising their temperature to 180-250°C. For example, the flue gas discharged from the hot blast stove can be used to preheat the gas and combustion air before they enter the furnace.

[0003] Currently, direct or indirect heat exchange is generally used to preheat the gas.

[0004] In direct heat exchange technology, plate, tube, and heat pipe heat exchangers are usually used to allow the flue gas discharged from the furnace to directly exchange heat with the gas to be preheated and the combustion air. This technical route has obvious drawbacks: (1) There is a risk of acid dew point corrosion on the flue gas side. When the heat exchange surface on the flue gas side is lower than the acid dew point temperature, the heat exchange surface is exposed to a corrosive environment, resulting in severe equipment corrosion and a short service life. (2) The hot blast stove of the blast furnace in metallurgical enterprises is usually composed of 3 to 4 furnace bodies. According to the process requirements, each furnace body is divided into combustion, waiting, and air supply states during operation and switches between them. Therefore, the flue gas discharged from the hot blast stove is the overall combination of these 3 to 4 furnace bodies, which causes the temperature and flow rate of the total flue gas to fluctuate drastically. The temperature can instantly jump from about 300°C to about 450°C, and the flue gas flow rate may also suddenly increase, resulting in a surge in heat load. The above-mentioned direct heat exchangers are difficult to adapt to such fluctuations and are prone to damage due to uneven thermal stress, overheating and tube rupture. (3) All of the above heat exchangers are fixed heat exchange devices. Once the heat exchange surface is set, there are no adjustment measures for the operation of the equipment. They cannot adapt to corrosion problems caused by drastic load fluctuations and seasonal changes, as well as problems such as flue gas overheating. (4) Heat pipe heat exchangers also suffer from the presence of air easily remaining in the tube cavity of the heat pipe, and non-condensable gases such as hydrogen produced by the chemical reaction between the medium water and the carbon steel tube wall in ordinary water-carbon steel heat pipes, which causes the heat exchange performance to decline year by year. (5) The service life of the above direct heat exchanger devices is generally only 3 to 5 years.

[0005] To circumvent the aforementioned problems of direct heat exchange in metallurgical gas preheating systems, an indirect water-based heat exchanger technology has been proposed. This technology uses water as an intermediate heat medium, establishing a closed-loop circulation between the flue gas heat exchanger and the gas preheater. A water bypass connects the two heat medium pipelines between the flue gas heat exchanger and the gas preheater, allowing the heat released from the flue gas to be indirectly transferred to the coal gas and air via the water medium. By controlling the water bypass, the corrosive environment on the flue gas side can be isolated. The gas preheater preheats both the coal gas and air using the water medium. However, when this technology is applied to the aforementioned metallurgical coal gas combustion device to preheat the coal gas and combustion air using flue gas, its inherent technical bottlenecks become apparent, even leading to more serious systemic safety risks:

[0006] 1. To preheat the gas and air to 180-250℃, the water medium at the gas preheater outlet temperature needs to reach approximately 260℃. At this temperature, to prevent water vaporization, the operating pressure of the water medium in the system must be maintained above 4.7MPa. This necessitates that the entire gas preheating system be designed according to high-pressure (approximately 10MPa) standards, including pipes, valves, pumps, heat exchangers, etc., resulting in high costs and a significant risk of leakage. More critically, when flue gas fluctuates, with the temperature abruptly changing from around 300℃ to around 450℃ and the flue gas flow rate also increasing, the sudden surge in heat load can cause a rapid rise in local water temperature. Under high pressure, this water is highly susceptible to instantaneous vaporization, forming a "vapor plug," leading to fluid blockage, deteriorated heat transfer, and ultimately, overheating of the heating surface, causing localized pipe rupture and posing a devastating threat to the entire high-pressure system.

[0007] 2. The heating surface is generally a multi-tube parallel structure. Water has a large specific heat capacity, which means that a smaller water flow rate is required to absorb the same amount of heat. In parallel heat exchange pipelines, uneven flow rate can easily lead to local overheating, which exacerbates the risk of steam lock and corrosion.

[0008] 3. The highest principle for regulating the hot water preheating system is "anti-vaporization". Its safe operating temperature / pressure window is very narrow, making it difficult to flexibly optimize for "anti-corrosion" and to actively avoid the acid dew point temperature of flue gas and the acid condensation temperature range of coal gas by precisely controlling the wall temperature.

[0009] 4. A chemical reaction occurs between the heat transfer medium water and the heat exchange tube wall to some extent, producing hydrogen gas, which corrodes the tube wall and shortens the service life of the heat exchange device.

[0010] In summary, those skilled in the art face a dilemma when confronted with the technical requirement of "providing an efficient, safe, and long-life gas preheating system for metallurgical gas combustion devices": direct heat exchange technology has a precarious lifespan due to corrosion and load fluctuations; while indirect water-based heat transfer technology, due to the physical properties of water, places the system in a sharp contradiction between high-pressure danger and instantaneous thermal shock, resulting in complex systems, high costs, and low safety. The industry urgently needs a new type of gas preheating system that can fundamentally reconstruct the system's operating logic to simultaneously meet the stringent requirements of withstanding operating condition fluctuations, resisting dual corrosion, and ensuring operational safety. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a gas preheating system for a coal gas combustion device in a metallurgical process, which solves the systemic safety risks and control dilemmas caused by indirect water-based heat exchange when dealing with drastic fluctuations in heat exchange load.

[0012] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0013] This invention provides a gas preheating system for a gas combustion device in a metallurgical process. The system uses heat transfer oil as the heat medium, and the heat transfer oil operates at a pressure below 1.0 MPa, forming a closed-loop system. The system includes:

[0014] A flue gas heat exchanger is used to connect to the flue gas discharge pipe of a gas combustion device.

[0015] A heat exchange device for preheating gas is used to preheat the combustion air and fuel gas entering the gas combustion device.

[0016] The system comprises a first heat medium conveying pipeline, a second heat medium conveying pipeline, and a heat medium bypass pipeline. The heat medium output end of the flue gas heat exchanger is connected to the heat medium input end of the preheated gas heat exchanger via the first heat medium conveying pipeline. The heat medium output end of the preheated gas heat exchanger is connected to the heat medium input end of the flue gas heat exchanger via the second heat medium conveying pipeline. The first heat medium conveying pipeline is connected to the second heat medium conveying pipeline via the heat medium bypass pipeline. The heat medium bypass pipeline is equipped with a bypass regulating device for adjusting the oil inlet temperature of the flue gas heat exchanger.

[0017] Optionally, the heat exchange device for the preheated gas includes a first preheater and a second preheater suitable for the sequential passage of low-temperature corrosive gas, and the first preheater and the second preheater are sequentially connected along the direction of heat medium transport. In the device of the first preheater, the gas and the heat medium flow in the same direction as each other, and in the device of the second preheater, the gas and the heat medium flow in opposite directions as each other.

[0018] Optionally, the heat exchange device for the preheated gas includes multiple preheating units, which are adapted to be supplied with independent gases; among the multiple preheating units, the preheating unit configured for preheating low-temperature corrosive gases includes a first preheater and a second preheater.

[0019] Optionally, among the multiple preheating units, a heat exchange unit configured for preheating non-low-temperature corrosive gases includes a third preheater, in which the gas and heat medium flow in generally opposite directions to each other.

[0020] Optionally, a first temperature sensor is installed at one end of the second heat medium conveying pipeline near the heat medium inlet of the flue gas heat exchanger, and the first temperature sensor is communicatively connected to the bypass regulating device.

[0021] Optionally, multiple preheating units are configured to be connected in parallel or in series between the first heat medium delivery pipeline and the second heat medium delivery pipeline via heat medium pipelines.

[0022] Optionally, multiple preheating units are configured to be connected in parallel between a first heat medium conveying pipe and a second heat medium conveying pipe via heat medium pipelines; the output end of the first heat medium conveying pipe is provided with a heat medium distribution device for distributing heat medium to each of the parallel preheating units.

[0023] Optionally, at least one preheating unit has a second temperature sensor installed at its gas outlet, and the second temperature sensor is communicatively connected to the heat medium distribution device.

[0024] Optionally, the preheated gas heat exchanger includes two preheating units: a first preheating unit and a second preheating unit. The first preheating unit is used to introduce fuel gas into the blast furnace hot blast stove, and the second preheating unit is used to introduce combustion air into the blast furnace hot blast stove. The flue gas heat exchanger is used to introduce flue gas emitted from the blast furnace hot blast stove; or...

[0025] The first preheating unit is used to introduce fuel gas into the gas-fired power generation boiler, the second preheating unit is used to introduce combustion air into the power generation boiler, and the flue gas heat exchange device is used to introduce flue gas emitted from the power generation boiler.

[0026] Optionally, the heat exchanger used in the flue gas heat exchange device and the heat exchanger used in the preheated gas heat exchange device both include a shell and several U-shaped tubes for heat exchange. The two ends of the shell are respectively provided with a first perforated plate as the shell end plate and a second perforated plate located inside the shell. The straight tube end of each U-shaped tube passes through the second perforated plate and the first perforated plate in sequence. The bent end of each U-shaped tube is located inside the shell, and the open end of each U-shaped tube extends out of the shell. Each U-shaped tube is fixedly connected to the first perforated plate, and each U-shaped tube is clearance-fitted with the second perforated plate. Each U-shaped tube is an integrally formed structure.

[0027] Several U-shaped tubes are configured as multiple parallel heat exchanger tube groups. Each heat exchanger tube group consists of multiple U-shaped tubes connected in series outside the shell through connecting elbows. The inlet and outlet of each heat exchanger tube group extend outside the shell.

[0028] The beneficial effects of this invention are:

[0029] The gas preheating system for metallurgical process gas combustion devices proposed in this invention firstly benefits from the high boiling point characteristics of the heat transfer oil. This allows the oil to operate safely at low pressures below 1.0 MPa, completely eliminating the systemic risk of "vapor plug" pipe rupture caused by vaporization of the heat transfer medium due to instantaneous overheating of the flue gas, and significantly reducing equipment manufacturing costs and leakage risks. Secondly, based on this platform of safe low-pressure operation of the heat transfer oil, combined with the setting of the heat transfer medium bypass pipeline, there is no need to consider "vaporization prevention," only "corrosion prevention" needs to be controlled. The system gains greater controllability, and can actively and precisely control the oil temperature entering the flue gas heat exchanger by adjusting the bypass flow rate, ensuring that its wall temperature is always higher than the acid dew point temperature of the flue gas. This achieves excellent protection against low-temperature corrosion under fluctuating operating conditions, significantly extending equipment life. Ultimately, the gas preheating system for metallurgical process gas combustion devices proposed in this invention successfully integrates high-efficiency heat exchange, intrinsic safety, and active corrosion prevention, forming a highly efficient, safe, and long-life gas preheating system that is particularly suitable for demanding operating conditions of metallurgical process gas combustion devices, such as blast furnace hot blast stoves and power generation boilers. Attached Figure Description

[0030] The present invention is described with reference to the following figures:

[0031] Figure 1 This is a schematic diagram of the gas preheating system for a metallurgical process gas combustion device according to Embodiment 1, wherein the dashed lines are used to indicate communication connections.

[0032] Figure 2 This is a schematic diagram of the gas preheating system for a metallurgical process gas combustion device according to Embodiment 2, wherein the dashed lines are used to indicate communication connections.

[0033] Figure 3 This is a schematic diagram of the gas preheating system for a metallurgical process gas combustion device according to Example 3, wherein the dashed lines are used to indicate communication connections.

[0034] Figure 4 This is a schematic diagram of the gas preheating system for a metallurgical process gas combustion device according to Example 4, wherein the dashed lines are used to indicate communication connections.

[0035] Figure 5This is a schematic diagram of the gas preheating system for a metallurgical process gas combustion device according to Example 5, wherein the dashed lines are used to indicate communication connections.

[0036] Figure 6 This is a front view of the heat exchanger according to Embodiment 6;

[0037] Figure 7 This is a left view of the heat exchanger according to Embodiment 6;

[0038] Figure 8 This is a top view of the heat exchanger according to Example 6.

[0039] [Explanation of Labels in the Attached Image]

[0040] 1: First heat medium transportation pipeline;

[0041] 11: Proportional regulating valve;

[0042] 2: Second heat medium transportation pipeline;

[0043] 21: First temperature sensor; 22: Oil-gas separator; 23: Circulation pump;

[0044] 31: First preheating unit; 32: Second preheating unit;

[0045] 331: First preheater; 332: Second preheater; 333: Second temperature sensor; 334: Third preheater;

[0046] 341: Shell; 342: U-shaped tube; 343: First orifice plate; 344: Second orifice plate; 345: Connecting elbow; 346: Heat transfer oil outlet header; 347: Heat transfer oil inlet header;

[0047] 41: Fourth heat exchanger;

[0048] 5: Heat medium bypass pipeline;

[0049] 51: Flow regulating valve;

[0050] 6: Expansion tank;

[0051] 7: Oil storage tank;

[0052] 8: Oil pump;

[0053] 91: First drain valve; 92: Second drain valve; 93: Third drain valve. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects, not to describe a particular order or hierarchy.

[0056] In this invention, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments.

[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this invention, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0059] In the embodiments of the present invention, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of the present invention shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on the present invention.

[0060] In this invention, "multiple" refers to two or more, including two.

[0061] like Figures 1 to 5 As shown, this invention provides a gas preheating system for a metallurgical process gas combustion device. The system uses heat transfer oil as the heat medium, and the heat transfer oil forms a closed-loop system at a working pressure below 1.0 MPa. It includes: a flue gas heat exchanger for connecting to the flue gas discharge pipe of the gas combustion device; a preheated gas heat exchanger for preheating the combustion air and fuel gas entering the gas combustion device; a first heat medium conveying pipe, a second heat medium conveying pipe, and a heat medium bypass pipe. The heat medium output end of the flue gas heat exchanger is connected to the heat medium input end of the preheated gas heat exchanger via the first heat medium conveying pipe. The heat medium output end of the preheated gas heat exchanger is connected to the heat medium input end of the flue gas heat exchanger via the second heat medium conveying pipe. The first heat medium conveying pipe is connected to the second heat medium conveying pipe via the heat medium bypass pipe. A bypass regulating device for adjusting the oil inlet temperature of the flue gas heat exchanger is provided on the heat medium bypass pipe.

[0062] This gas preheating system benefits from the high boiling point of the heat transfer oil, allowing it to operate safely at pressures below 1.0 MPa. This completely eliminates the systemic risk of vaporization of the water-heating medium due to instantaneous overheating of flue gas, leading to pipe bursts and significantly reducing equipment manufacturing costs and leakage risks. Furthermore, on this low-pressure, safe platform, combined with the bypass pipeline, there's no need to consider vaporization prevention; only corrosion prevention needs to be addressed. This provides greater controllability, allowing for proactive and precise control of the oil temperature entering the flue gas heat exchanger by adjusting the bypass flow rate. This ensures the wall temperature remains above the acid dew point, providing excellent protection against low-temperature corrosion under fluctuating conditions and significantly extending equipment lifespan. Ultimately, the gas preheating system for metallurgical process gas combustion devices proposed in this invention successfully integrates high-efficiency heat exchange, intrinsic safety, and proactive corrosion prevention, forming a highly efficient, safe, and long-life gas preheating system particularly suitable for demanding conditions in metallurgical process gas combustion devices such as blast furnace hot blast stoves and power generation boilers.

[0063] In preheated gas heat exchangers, the gas side, especially the blast furnace gas produced from iron ore imported by sea, often contains corrosive components such as chloride ions, hydrogen sulfide, elemental sulfur, and water vapor. These components will condense to form highly corrosive acid when the wall temperature of the heated surface is lower than the acid dew point of the gas.

[0064] Therefore, the heat exchange device for the preheated gas includes a first preheater 331 and a second preheater 332 suitable for the sequential passage of low-temperature corrosive gases, and the first preheater 331 and the second preheater 332 are sequentially connected along the direction of heat medium transport. In the device of the first preheater 331, the gas and the heat medium flow in the same direction as each other, and in the device of the second preheater 332, the gas and the heat medium flow in opposite directions as each other.

[0065] In this context, "gas and heat medium flowing in the same direction overall" means that their primary flow directions are the same; they both enter the preheater from the same end and exit from opposite ends. Although the preheater may have heat exchange surface bends, baffles, or other flow-guiding structures that cause changes in the flow direction of the gas or heat medium in local areas, the overall flow directions of the gas and heat medium are consistent. "Gas and heat medium flowing in opposite directions overall" means that their primary flow directions are opposite; the gas enters from one end of the preheater and exits from the other, while the heat medium enters from the gas exit end and exits from the gas inlet end, thus forming a counter-current flow pattern. Similarly, due to the presence of baffle structures, the local flow direction may not be completely consistent with the overall direction, but the two fluids flow in opposite directions overall.

[0066] This heat exchange system employs a two-stage heat exchange design with the preheated gas heat exchanger connected in series and flowing in a specific direction, offering the dual advantages of corrosion resistance and high heat exchange efficiency. Specifically, the low-temperature corrosive gas first enters the first preheater 331, where it flows in a generally co-current manner with the heat medium. This arrangement ensures that the highest-temperature heat medium first contacts the lowest-temperature gas, which has the highest risk of corrosion, rapidly raising the gas temperature and quickly evaporating any moisture or acidic water, significantly mitigating low-temperature acid dew point corrosion or low-temperature water dew point corrosion of the heated gas, thus ensuring the long-term stability of the heat exchange system. Furthermore, the first preheater 331 provides primary preheating of the heated gas, typically heating it above its low-temperature acid dew point or low-temperature water dew point temperature to prevent low-temperature acid dew point corrosion or low-temperature water dew point corrosion in the second preheater 332. The gas treated by the first preheater 331 then enters the second preheater 332, where it flows in a generally counter-current manner with the heat medium. Countercurrent heat exchange, with its high average heat exchange temperature difference, can achieve deep and efficient heat transfer, greatly improving heat exchange efficiency and ensuring that the gas is preheated to the required final temperature.

[0067] The heat exchange system proposed in this invention cleverly solves the two major problems of corrosion control and energy efficiency improvement in the gas preheating process by using a series two-stage design of "co-current anti-corrosion pretreatment + counter-current deep and efficient heat exchange", thus ensuring the long-term stable operation of the system.

[0068] It should be noted that the low-temperature corrosive gas can be either a low-temperature acid dew point corrosive gas or a low-temperature water dew point corrosive gas, and the heat exchange system of this invention is applicable to any of these low-temperature corrosive gases. Common low-temperature acid dew point corrosive gases include fuel gases from blast furnace hot blast stoves and plant gas-fired power generation boilers, such as blast furnace gas, coke oven gas, converter gas, or mixed gas; common low-temperature water dew point corrosive gases include combustion air from blast furnace hot blast stoves and plant gas-fired power generation boilers during winter. The listed gases are merely examples and are not intended to limit the invention.

[0069] It is important to emphasize that this invention is applied to heat exchange of medium-low temperature flue gas in the range of 120℃-450℃. Conventional heat exchange designs within this temperature range generally pursue counter-current arrangement to achieve high heat exchange efficiency. This invention breaks with this conventional approach, innovatively transforming the co-current heat exchange method, which is prone to efficiency loss, into a corrosion prevention measure. It proposes a two-stage design in series: "co-current stage corrosion prevention pretreatment + counter-current stage deep and efficient heat exchange." This design, through functional decomposition, allows the co-current stage to focus on solving the low-temperature corrosion problem, while the counter-current stage is dedicated to ensuring the final heat exchange efficiency. Thus, it simultaneously overcomes the two major technical bottlenecks of corrosion control and efficient energy recovery, achieving a balance between long-term equipment safety and operational economy.

[0070] Preferably, the first preheater 331 is configured to heat the low-temperature corrosive gas to above its acid dew point temperature or water dew point temperature under set heat medium input conditions; the second preheater 332 is configured to heat the low-temperature corrosive gas to the target temperature under set heat medium input conditions. Thus, through the first-stage preheating of the first preheater 331, the moisture or acidic moisture in the gas can be rapidly evaporated using the maximum initial temperature difference, while simultaneously heating the gas to above its acid dew point temperature or water dew point temperature. This avoids low-temperature acid dew point corrosion or low-temperature water dew point corrosion of the low-temperature corrosive gas within the second preheater 332, allowing the gas to be deeply heated to the target temperature via the second preheater 332.

[0071] The first preheater 331 and the second preheater 332 can be plate heat exchangers, shell-and-tube heat exchangers, or tubular heat exchangers. The heat exchanger types listed are merely examples and are not intended to limit the invention.

[0072] Preferably, the preheated gas heat exchange device includes multiple preheating units, each adapted to be supplied with independent gases. Among the multiple preheating units, the preheating unit configured for preheating low-temperature corrosive gases includes a first preheater 331 and a second preheater 332. Through modular design, the heat exchange system provided by this invention can preheat multiple independent gases in parallel. By customizing a two-stage preheating unit of "co-current anti-corrosion pretreatment + counter-current deep and efficient heat exchange" for the low-temperature corrosive gas passage, corrosion prevention and long-term stable heat exchange are achieved in the low-temperature corrosive gas passage while providing preheating for multiple gases.

[0073] Of course, among the multiple preheating units, there is also a preheating unit configured for preheating gases without low-temperature corrosiveness. This preheating unit includes a third preheater 334, in which the gas and the heat transfer medium flow in generally opposite directions. In this way, a highly efficient counter-current heat exchange scheme is precisely applied to preheating gases without corrosive risks, thereby ensuring the overall energy efficiency of the system while avoiding over-design and reducing costs.

[0074] Preferably, multiple preheating units are configured to be connected in parallel between the first heat medium delivery pipe 1 and the second heat medium delivery pipe 2 via heat medium pipelines. This achieves preheating of multiple gases while providing a structural basis for independently controlling the heating conditions of each gas passage in the heat exchange system.

[0075] More preferably, a proportional regulating valve 11 is provided at the output end of the first heat medium conveying pipeline 1, which is suitable for distributing heat medium to each parallel preheating unit. In this way, the proportional regulating valve 11 ensures that the system can provide differentiated heating according to actual process requirements and effectively cope with fluctuations in operating conditions.

[0076] More preferably, at least one preheating unit has a second temperature sensor 333 installed at its gas outlet, and the second temperature sensor 333 is communicatively connected to the proportional control valve 11. This introduces a closed-loop control mechanism based on the gas outlet temperature feedback of the preheating unit into the heat exchange system, thereby achieving real-time, accurate, and adaptive adjustment of the preheating temperature, ensuring process stability, and improving system energy efficiency.

[0077] Of course, it is preferred that multiple preheating units are configured to be connected in parallel between the first heat medium conveying pipe 1 and the second heat medium conveying pipe 2 via heat medium pipes; alternatively, multiple preheating units can be configured to be connected in series between the first heat medium conveying pipe 1 and the second heat medium conveying pipe 2 via heat medium pipes, which can also achieve the preheating of various gases.

[0078] It should be noted that the heat exchange device for the preheated gas includes multiple preheating units, which is only one embodiment. Optionally, the heat exchange device for the preheated gas may also include a single preheating unit configured for preheating low-temperature corrosive gases.

[0079] Preferably, the flue gas heat exchange device includes a plurality of fourth heat exchangers 41, in which the flue gas and the heat medium flow in opposite directions. This improves the heat exchange efficiency between the flue gas and the heat medium. More preferably, the plurality of fourth heat exchangers 41 are configured to be connected in series between the second heat medium delivery pipe 2 and the first heat medium delivery pipe 1 via heat medium pipelines, and also connected in series via flue gas pipelines. By adopting a modular design with multi-stage counter-current series connection, the heat exchange process is highly enhanced and the thermal energy is utilized in stages on both the flue gas and heat medium sides, thereby maximizing the heat exchange efficiency of the entire system for medium and low temperature flue gas.

[0080] Preferably, a first temperature sensor 21 is installed on the second heat medium conveying pipeline 2 near the heat medium inlet of the flue gas heat exchanger, and the first temperature sensor 21 is communicatively connected to the flow regulating valve 51. In this way, by monitoring the temperature of key nodes and implementing closed-loop control, the minimum limit protection of the heat medium temperature at the inlet of the flue gas heat exchanger is achieved, fundamentally eliminating the risk of low-temperature corrosion on the flue gas side.

[0081] Preferably, the heat exchange system provided by the present invention further includes an expansion tank 6 for accommodating the expansion of the heat transfer medium; an oil-gas separator 22 is provided on the second heat transfer medium conveying pipeline 2, the first heat transfer medium outlet of the oil-gas separator 22 is connected to the expansion tank 6, and the heat transfer medium inlet and the second heat transfer medium outlet of the oil-gas separator 22 are both connected to the second heat transfer medium conveying pipeline 2; the connection position of the heat transfer medium bypass pipeline 5 and the second heat transfer medium conveying pipeline 2 is located between the oil-gas separator 22 and the preheated gas heat exchange device. Thus, by setting up the expansion tank 6 and the oil-gas separator 22, a pressure stabilization and venting subsystem working in concert is formed. By connecting the heat transfer medium bypass pipeline 5 between the oil-gas separator 22 and the preheated gas heat exchange device, it is ensured that all heat transfer medium participating in the circulation, including the portion returning from the bypass pipeline, must be processed by the oil-gas separator 22, thereby ensuring the gas-liquid separation effect, pressure stability, integrity, and reliability of the heat transfer oil medium within the entire heat exchange system. The pressure stabilization and exhaust subsystem consisting of expansion tank 6 and oil-gas separator 22 can not only safely accommodate the volume expansion of the heat medium caused by temperature changes and maintain the stability of the system pressure, but also effectively separate and remove light component gases and water vapors released in the circulating heat medium, thereby ensuring the stable operation of the heat exchange circuit, eliminating the increase in heat transfer resistance caused by the presence of dissolved gases in the heat transfer oil, and ensuring that the entire heat exchange system can work efficiently and reliably for a long time.

[0082] Specifically, the heat exchange system provided by the present invention also includes a circulation pump 23 installed on the second heat medium conveying pipeline 2, and the circulation pump 23 is located between the oil-gas separator 22 and the flue gas heat exchange device.

[0083] Specifically, the heat exchange system provided by this invention further includes an oil storage tank 7 and an oil injection pump 8; the outlet of the oil injection pump 8 is connected to the oil injection port of the expansion tank 6 via an oil injection pipe, and the outlet of the oil injection pump 8 is connected to the oil storage tank 7 via a first oil drain pipe, on which a first oil drain valve 91 is installed; the oil drain port of the second heat medium conveying pipeline 2 is connected to the oil storage tank 7 via a second oil drain pipe, and the oil drain port is located between the oil-gas separator 22 and the circulating pump 23, on which a second oil drain valve 92 is installed; the overflow port of the expansion tank 6 is connected to the oil storage tank 7 via an overflow pipe, and the oil drain port of the expansion tank 6 is connected to the oil storage tank 7 via a third oil drain pipe, on which a third oil drain valve 93 is installed. Thus, a comprehensive heat medium management system integrating automatic liquid replenishment, overflow protection, and controllable venting functions is constructed, thereby ensuring the long-term self-sustaining stable operation and operational safety of the heat exchange system under various operating conditions.

[0084] The following examples illustrate different forms of the heat exchange system proposed in this invention.

[0085] Example 1

[0086] like Figure 1 As shown, the gas preheating system for a metallurgical process gas combustion device provided in this embodiment includes a first heat medium conveying pipeline 1, a second heat medium conveying pipeline 2, a flue gas heat exchange device, and a preheated gas heat exchange device. The heat medium output end of the flue gas heat exchange device is connected to the heat medium input end of the preheated gas heat exchange device through the first heat medium conveying pipeline 1, and the heat medium output end of the preheated gas heat exchange device is connected to the heat medium input end of the flue gas heat exchange device through the second heat medium conveying pipeline 2. The preheated gas heat exchange device includes a preheating unit configured for preheating low-temperature corrosive gases. This preheating unit includes a first preheater 331 and a second preheater 332 suitable for the sequential passage of low-temperature corrosive gases. The first preheater 331 and the second preheater 332 are sequentially connected along the heat medium conveying direction. In the first preheater 331, the gas and heat medium flow in the same direction overall, while in the second preheater 332, the gas and heat medium flow in opposite directions overall.

[0087] It should be noted that the low-temperature corrosive gas introduced into the preheating unit can be either a gas with low-temperature acid dew point corrosivity or a gas with low-temperature water dew point corrosivity. Specifically, the low-temperature acid dew point corrosive gas can be the fuel gas from the blast furnace hot blast stove and the plant's power generation boilers, such as blast furnace gas, coke oven gas, or a mixture of gases; the low-temperature water dew point corrosive gas can be the combustion air from the blast furnace hot blast stove and the plant's power generation boilers, where the water content is higher than the set value in winter.

[0088] It should be noted that the flue gas can be the flue gas emitted from the blast furnace hot blast stove and the power generation boiler in the plant.

[0089] Preferably, the heat exchange system proposed in this invention further includes a heat medium bypass pipe 5, the first heat medium conveying pipe 1 is connected to the second heat medium conveying pipe 2 through the heat medium bypass pipe 5, and a flow regulating valve 51 is provided on the heat medium bypass pipe 5.

[0090] Specifically, in this embodiment, the flue gas heat exchange device includes two heat exchangers, which are configured to be connected in series between the second heat medium conveying pipe 2 and the first heat medium conveying pipe 1 via heat medium pipes, and also connected in series via flue gas pipes; the flue gas and heat medium in the channels of each heat exchanger flow in generally opposite directions to each other.

[0091] It should be noted that the above-described flue gas heat exchange device, which includes two heat exchangers, is merely an example. Of course, the flue gas heat exchange device may also include one heat exchanger or three or more heat exchangers. This invention is not limited herein.

[0092] Preferably, a first temperature sensor 21 is provided at one end of the second heat medium conveying pipeline 2 near the heat medium inlet of the flue gas heat exchange device, and the first temperature sensor 21 is communicatively connected to the flow regulating valve 51.

[0093] Specifically, in this embodiment, the heat transfer medium is heat transfer oil.

[0094] Specifically, in this embodiment, the heat exchange system further includes an expansion tank 6 for accommodating the expansion of the heat medium; an oil-gas separator 22 is provided on the second heat medium conveying pipeline 2, the first heat medium outlet of the oil-gas separator 22 is connected to the expansion tank 6, and the heat medium inlet and the second heat medium outlet of the oil-gas separator 22 are both connected to the second heat medium conveying pipeline 2; the connection position of the heat medium bypass pipeline 5 and the second heat medium conveying pipeline 2 is located between the oil-gas separator 22 and the preheated gas heat exchange device.

[0095] Specifically, in this embodiment, the heat exchange system further includes a circulation pump 23 disposed on the second heat medium conveying pipeline 2, and the circulation pump 23 is located between the oil-gas separator 22 and the flue gas heat exchange device.

[0096] Specifically, in this embodiment, the heat exchange system further includes an oil storage tank 7 and an oil injection pump 8; the outlet of the oil injection pump 8 is connected to the oil injection port of the expansion tank 6 through an oil injection pipe, and the outlet of the oil injection pump 8 is connected to the oil storage tank 7 through a first oil drain pipe, on which a first oil drain valve 91 is provided; the oil drain port of the second heat medium conveying pipeline 2 is connected to the oil storage tank 7 through a second oil drain pipe, and the oil drain port is located between the oil-gas separator 22 and the circulating pump 23, on which a second oil drain valve 92 is provided; the overflow port of the expansion tank 6 is connected to the oil storage tank 7 through an overflow pipe, and the oil drain port of the expansion tank 6 is connected to the oil storage tank 7 through a third oil drain pipe, on which a third oil drain valve 93 is provided.

[0097] Example 2

[0098] The main difference between this embodiment and Embodiment 1 is:

[0099] like Figure 2 As shown, the preheated gas heat exchange device includes two preheating units, namely a first preheating unit 31 and a second preheating unit 32, which are adapted to be supplied with independent gases. Both the first preheating unit 31 and the second preheating unit 32 are configured as preheating units for preheating low-temperature corrosive gases. Specifically, both the first preheating unit 31 and the second preheating unit 32 include a first preheater 331 and a second preheater 332 adapted for the sequential passage of low-temperature corrosive gases. The first preheater 331 and the second preheater 332 are sequentially connected along the direction of heat transfer. Within the device of the first preheater 331, the gas and heat transfer medium flow in the same direction overall, while within the device of the second preheater 332, the gas and heat transfer medium flow in opposite directions overall.

[0100] It should be noted that the low-temperature corrosive gas introduced into the first preheating unit 31 and the second preheating unit 32 can be either a low-temperature acid dew point corrosive gas or a low-temperature water dew point corrosive gas. Specifically, the low-temperature acid dew point corrosive gas can be fuel gas from the blast furnace hot blast stove and the plant's power generation boilers, such as blast furnace gas, coke oven gas, or mixed gas; the low-temperature water dew point corrosive gas can be combustion air from the blast furnace hot blast stove and the plant's power generation boilers with a water content higher than a set value. It should also be noted that the flue gas can be the flue gas emitted from the blast furnace hot blast stove and the plant's power generation boilers.

[0101] As an example, the first preheating unit 31 is supplied with fuel gas from the blast furnace hot blast stove, the second preheating unit 32 is supplied with combustion air from the blast furnace hot blast stove, and the flue gas heat exchange device is supplied with flue gas emitted from the blast furnace hot blast stove.

[0102] Preferably, the first preheating unit 31 and the second preheating unit 32 are configured to be connected in parallel between the first heat medium conveying pipe 1 and the second heat medium conveying pipe 2 via heat medium pipelines. Further, a proportional regulating valve 11 is provided at the output end of the first heat medium conveying pipe 1, suitable for distributing heat medium to the parallel first preheating unit 31 and the second preheating unit 32.

[0103] Preferably, in this embodiment, a second temperature sensor 333 is provided at the gas outlet of the first preheating unit 31, and the second temperature sensor 333 is communicatively connected to the proportional regulating valve 11. This enables real-time, precise, and adaptive adjustment of the fuel gas preheating temperature.

[0104] The remaining contents are the same as in Example 1, and will not be repeated here.

[0105] Example 3

[0106] The main difference between this embodiment and Embodiment 2 is:

[0107] like Figure 3 As shown, the first preheating unit 31 is configured for preheating low-temperature corrosive gases. Specifically, the first preheating unit 31 includes a first preheater 331 and a second preheater 332, suitable for the sequential passage of low-temperature corrosive gases. The first preheater 331 and the second preheater 332 are sequentially connected along the heat transfer medium direction. Within the device of the first preheater 331, the gas and heat transfer medium flow in generally the same direction, while within the device of the second preheater 332, the gas and heat transfer medium flow in generally opposite directions. The second preheating unit 32 is configured for preheating gases without low-temperature corrosiveness. Specifically, the second preheating unit 32 includes a third preheater 334, within which the gas and heat transfer medium flow in generally opposite directions.

[0108] It should be noted that the low-temperature corrosive gas introduced into the first preheating unit 31 can be either a low-temperature acid dew point corrosive gas or a low-temperature water dew point corrosive gas. Specifically, the low-temperature acid dew point corrosive gas can be fuel gas from the blast furnace hot blast stove and the plant's power generation boiler, such as blast furnace gas, coke oven gas, or mixed gas; the low-temperature water dew point corrosive gas can be combustion air from the blast furnace hot blast stove and the plant's power generation boiler with a water content higher than a set value. The low-temperature corrosive gas introduced into the second preheating unit 32 can be combustion air from the blast furnace hot blast stove and the plant's power generation boiler with a water content lower than a set value. It should also be noted that the flue gas can be the flue gas emitted from the blast furnace hot blast stove and the plant's power generation boiler.

[0109] As an example, the first preheating unit 31 is supplied with fuel gas from the blast furnace hot blast stove, the second preheating unit 32 is supplied with combustion air from the blast furnace hot blast stove with a moisture content lower than the set value, and the flue gas heat exchange device is supplied with flue gas emitted from the blast furnace hot blast stove.

[0110] The remaining contents are the same as in Example 2, and will not be repeated here.

[0111] Example 4

[0112] The main difference between this embodiment and Embodiment 2 is:

[0113] like Figure 4 As shown, the first preheating unit 31 and the second preheating unit 32 are configured to be connected in series between the first heat medium delivery pipe 1 and the second heat medium delivery pipe 2 via heat medium pipelines. In this case, there is no need to install the second temperature sensor 333 and the proportional regulating valve 11.

[0114] It should be noted that the low-temperature corrosive gas introduced into the first preheating unit 31 and the second preheating unit 32 can be either a low-temperature acid dew point corrosive gas or a low-temperature water dew point corrosive gas. Specifically, the low-temperature acid dew point corrosive gas can be fuel gas from the blast furnace hot blast stove and the plant's power generation boilers, such as blast furnace gas, coke oven gas, or mixed gas; the low-temperature water dew point corrosive gas can be combustion air from the blast furnace hot blast stove and the plant's power generation boilers with a water content higher than a set value. It should also be noted that the flue gas can be the flue gas emitted from the blast furnace hot blast stove and the plant's power generation boilers.

[0115] As an example, the first preheating unit 31 and the second preheating unit 32 are connected in series via heat medium pipelines. The first preheating unit 31 is supplied with combustion air from the blast furnace hot blast stove, the second preheating unit 32 is supplied with fuel gas from the blast furnace hot blast stove, and the flue gas heat exchange device is supplied with flue gas emitted from the blast furnace hot blast stove.

[0116] The remaining contents are the same as in Example 2, and will not be repeated here.

[0117] Example 5

[0118] The main difference between this embodiment and Embodiment 4 is:

[0119] like Figure 5As shown, the second preheating unit 32 is configured as a heat exchange unit for preheating low-temperature corrosive gases. Specifically, the second preheating unit 32 includes a first preheater 331 and a second preheater 332, suitable for the sequential passage of low-temperature corrosive gases. The first preheater 331 and the second preheater 332 are sequentially connected along the heat medium conveying direction. Within the device of the first preheater 331, the gas and heat medium flow in generally the same direction, while within the device of the second preheater 332, the gas and heat medium flow in generally opposite directions. The first preheating unit 31 is also configured as a preheating unit for preheating gases without low-temperature corrosiveness. Specifically, the first preheating unit 31 includes a third preheater 334, within which the gas and heat medium flow in generally opposite directions.

[0120] It should be noted that the low-temperature corrosive gas introduced into the second preheating unit 32 can be either a low-temperature acid dew point corrosive gas or a low-temperature water dew point corrosive gas. Specifically, the low-temperature acid dew point corrosive gas can be fuel gas from the blast furnace hot blast stove and the plant's power generation boiler, such as blast furnace gas, coke oven gas, or mixed gas; the low-temperature water dew point corrosive gas can be combustion air from the blast furnace hot blast stove and the plant's power generation boiler with a water content higher than a set value. The non-low-temperature corrosive gas introduced into the first preheating unit 31 can be combustion air from the blast furnace hot blast stove and the plant's power generation boiler with a water content lower than a set value. It should also be noted that the flue gas can be the flue gas emitted from the blast furnace hot blast stove and the plant's power generation boiler.

[0121] As an example, the second preheating unit 32 is supplied with fuel gas from the blast furnace hot blast stove, the first preheating unit 31 is supplied with combustion air from the blast furnace hot blast stove with a moisture content lower than the set value, and the flue gas heat exchange device is supplied with flue gas emitted from the blast furnace hot blast stove.

[0122] The remaining contents are the same as in Example 4, and will not be repeated here.

[0123] Example 6

[0124] This embodiment provides a heat exchanger that can be used as a heat exchanger in a flue gas heat exchange device or as a preheater in a preheated gas heat exchange device.

[0125] The heat exchanger includes a shell 341 and a plurality of U-shaped tubes 342 for heat exchange. The shell 341 has a first perforated plate 343 serving as end plates at both ends and a second perforated plate 344 located inside the shell 341. The straight end of each U-shaped tube 342 passes through the second perforated plate 344 and the first perforated plate 343 in sequence. The elbow end of each U-shaped tube 342 is located inside the shell 341, and the open end of each U-shaped tube 342 extends outside the shell 341. Each U-shaped tube 342 is fixedly connected to the first perforated plate 343 and is clearance-fitted to the second perforated plate 344. Each U-shaped tube 342 is an integrally formed structure. The plurality of U-shaped tubes 342 are configured into multiple parallel heat exchange tube groups. Each heat exchange tube group is formed by multiple U-shaped tubes 342 connected in series outside the shell 341 through connecting elbows 345. The inlet and outlet of each heat exchange tube group extend outside the shell 341.

[0126] This heat exchanger design, using one-piece molded U-shaped heat exchange tubes, eliminates all weld seams in the heat exchange tube sections within the shell 341. This fundamentally eliminates the main failure risk of heat transfer oil leakage caused by heat exchange tube damage due to weld seam cracking and limited thermal expansion of the heat exchange tubes in traditional heat exchangers. It greatly improves the operational reliability and lifespan of the equipment under high-temperature and thermal stress conditions. At the same time, all the connecting elbows 345 connecting each U-shaped tube 342 are located outside the shell 341, so that the connecting weld seams between the connecting elbows 345 and the U-shaped tubes 342 are also located outside the shell 341. This allows for the inspection and replacement of individual heat exchange tubes without cutting the shell 341 or removing the entire tube bundle, thus achieving convenient and low-cost maintenance and significantly reducing the total life cycle cost of the equipment.

[0127] When the heat exchanger is used as a heat exchanger in a flue gas heat exchange device, each heat exchange tube assembly is used to introduce heat transfer oil, and the shell 341 is used to introduce flue gas, so that heat exchange occurs between the flue gas and the heat transfer oil. Figure 6 , Figure 7 and Figure 8 The example shown is of flue gas being introduced into the heat exchanger shell 341. When the heat exchanger is used as a heat exchanger for a preheated gas, each heat exchange tube group is used to introduce heat transfer oil, and the shell 341 is used to introduce the preheated gas, so that heat exchange occurs between the preheated gas and the heat transfer oil.

[0128] Specifically, the heat exchanger also includes a heat transfer oil inlet header 347 and a heat transfer oil outlet header 346. The heat transfer oil inlet header 347 is connected to the inlet of each heat exchange tube group, and the heat transfer oil outlet header 346 is connected to the outlet of each heat exchange tube group.

[0129] It should be noted that the number of second perforated plates 344 provided in the housing 341 is at least one, and the specific number is set according to the length of the U-shaped tube 342 and the support requirements. This invention does not limit this number.

[0130] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gas preheating system for a metallurgical process gas combustion device, characterized in that, The system uses heat transfer oil as the heat medium and the heat transfer oil forms a closed-loop system at a working pressure below 1.0 MPa. It includes: a flue gas heat exchange device for connecting to the flue gas discharge pipe of the gas combustion device, wherein the flue gas discharged from the flue gas discharge pipe is medium and low temperature flue gas with a temperature of 120-450℃; a preheated gas heat exchange device for preheating the combustion air and fuel gas entering the gas combustion device; a first heat medium conveying pipe (1), a second heat medium conveying pipe (2) and a heat medium bypass pipe (5). The heat medium output end of the flue gas heat exchange device is connected to the heat medium input end of the preheated gas heat exchange device through the first heat medium conveying pipe (1), and the heat medium output end of the preheated gas heat exchange device is connected to the heat medium input end of the flue gas heat exchange device through the second heat medium conveying pipe (2). The first heat medium conveying pipe (1) is connected to the second heat medium conveying pipe (2) through the heat medium bypass pipe (5). The heat medium bypass pipe (5) is equipped with a bypass regulating device for regulating the oil inlet temperature of the flue gas heat exchange device. The preheated gas heat exchanger includes multiple preheating units suitable for introducing independent gases. These preheating units are connected in parallel between a first heat medium conveying pipe (1) and a second heat medium conveying pipe (2) via heat medium pipelines. The preheating unit for preheating low-temperature corrosive gases includes a first preheater (331) and a second preheater (332) through which the gas passes sequentially. The first preheater (331) and the second preheater (332) are separately arranged, and are sequentially connected along the heat medium conveying direction. Within the device of the first preheater (331), the gas and heat medium move along each other. In the second preheater (332), the gas and heat medium flow in the same direction, generally in opposite directions. Both the first preheater (331) and the second preheater (332) include a shell (341) and multiple heat exchange tube groups. Each heat exchange tube group is used to introduce heat transfer oil, and the shell (341) is used to introduce the gas to be preheated. The output end of the first heat medium conveying pipe (1) is provided with a proportional regulating valve (11) suitable for distributing heat medium to each parallel preheating unit. The gas outlet of the second preheater (332) is provided with a second temperature sensor (333), which is communicatively connected to the proportional regulating valve (11).

2. The gas preheating system for a metallurgical process gas combustion device according to claim 1, characterized in that, Among the multiple preheating units, a heat exchange unit configured for preheating non-low-temperature corrosive gases includes a third preheater (334), in which the gas and heat medium flow in generally opposite directions to each other.

3. The gas preheating system for a metallurgical process gas combustion device according to claim 1, characterized in that, A first temperature sensor (21) is installed at one end of the second heat medium conveying pipeline (2) near the heat medium inlet of the flue gas heat exchange device. The first temperature sensor (21) is connected in communication with the bypass regulating device.

4. The gas preheating system for a metallurgical process gas combustion device according to claim 1, characterized in that, The preheated gas heat exchanger includes two preheating units: a first preheating unit (31) and a second preheating unit (32). The first preheating unit (31) is used to introduce fuel gas into the blast furnace hot blast stove, and the second preheating unit (32) is used to introduce combustion air into the blast furnace hot blast stove. The flue gas heat exchanger is used to introduce flue gas discharged from the blast furnace hot blast stove; or, The first preheating unit (31) is used to introduce blast furnace gas into the power generation boiler, the second preheating unit (32) is used to introduce combustion air into the power generation boiler, and the flue gas heat exchange device is used to introduce flue gas discharged from the power generation boiler.

5. The gas preheating system for a metallurgical process gas combustion device according to claim 1, characterized in that, The heat exchanger used in the flue gas heat exchange device and the heat exchanger used in the preheated gas heat exchange device both include a shell (341) and a number of U-shaped tubes (342) for heat exchange. The two ends of the shell (341) are respectively provided with a first perforated plate (343) as the shell end plate and a second perforated plate (344) located inside the shell (341). The straight end of each U-shaped tube (342) passes through the second perforated plate (344) and the first perforated plate (343) in sequence. The bent end of each U-shaped tube (342) is located inside the shell (341), and the open end of each U-shaped tube (342) extends out of the shell (341). Each U-shaped tube (342) is fixedly connected to the first perforated plate (343), and each U-shaped tube (342) is clearance-fitted with the second perforated plate (344). Each U-shaped tube (342) is an integrally formed structure. Several U-shaped tubes (342) are configured as multiple parallel heat exchanger tube groups. Each heat exchanger tube group consists of multiple U-shaped tubes connected in series outside the shell through connecting elbows. The inlet and outlet of each heat exchanger tube group extend outside the shell.

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