Waste heat recovery method and system for multi-stage utilization of flue gas heat of tilting furnace

Abstract

The invention discloses a waste heat recovery method and system for multi-stage utilization of flue gas heat of a tilting furnace, and the waste heat recovery method comprises the following steps: main flue gas of a waste heat boiler exchanges heat with main flue gas heated by a GGH heat exchanger through a first gas-gas heat exchanger to obtain first-stage heat exchange gas, and the first-stage heat exchange gas exchanges heat with circulating water to obtain second-stage heat exchange gas; the second-stage heat exchange gas exchanges heat with combustion-supporting air to obtain third-stage heat exchange gas; and the third-stage heat exchange gas exchanges heat with air to obtain fourth-stage heat exchange gas. High-temperature flue gas in a flue of the tilting furnace is subjected to multi-stage utilization, and an efficient waste heat recovery system is constructed. Flue gas of the tilting furnace is subjected to heat exchange through the waste heat boiler and then is subjected to efficient heat exchange with different medium and low temperature gases through the multi-stage series main heat exchanger. The device has the advantages of being simple in process, diversified in function, efficient in heat utilization and the like, and has popularization and reference significance for high-temperature flue gas waste heat utilization of other metallurgical furnaces.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology in metallurgical furnaces and kilns, and more specifically, to a waste heat recovery method and system for multi-stage utilization of flue gas heat from a tilting furnace. Background Technology

[0002] Metallurgical furnaces and kilns constantly undergo exothermic combustion reactions, generating large quantities of high-temperature flue gas. This flue gas is characterized by its high temperature and large volume. Currently, heat recovery from this high-temperature flue gas in metallurgical furnaces and kilns is generally achieved through heat exchange with the boiler tube walls. The resulting steam is typically used for power generation and heating / drying materials, resulting in a relatively singular heat utilization pathway. To meet the operating temperature requirements of downstream equipment, the high-temperature flue gas, after being cooled by the boiler, may need further mixing with cold outdoor air for further cooling. This undoubtedly reduces heat utilization efficiency and increases the burden on flue gas treatment.

[0003] High-temperature flue gas in metallurgical furnaces generally contains soot and harmful components such as sulfur dioxide, nitrogen oxides, and dioxins. Dust removal equipment usually requires the flue gas temperature to be reduced to a certain range, while equipment for harmless treatment of flue gas usually requires a certain operating temperature range and cleanliness. Therefore, flue gas needs to be cooled and dust removed before being heated and treated to render it harmless, which places strict requirements on flue gas heat management.

[0004] Chinese patent document (application number: 202411086684.1, application date: 2024.08.08) discloses a method and apparatus for recovering and utilizing the heat energy of high-temperature flue gas in metallurgical furnaces, comprising: the high-temperature flue gas discharged from the furnace first enters a waste heat boiler, the waste heat boiler is equipped with boiler tubes, the boiler tubes are connected to an upstream water pump for pumping cooling water into the system to complete the circulation; under the convection and radiation heating of the high-temperature flue gas, the liquid water in the boiler tube boils to form superheated steam, the superheated steam is introduced into a preheater through a pipeline for heating the low-temperature gas phase feed; the upstream of the low-temperature gas phase feed is connected to a compressor, and the downstream is connected to a spray gun to directly spray the preheated high-temperature gas phase into the furnace, at which time the high-temperature steam is still in a supersaturated state, used to drive the downstream generator to generate electricity; after the high-temperature steam releases heat energy, it turns into liquid and finally flows back into the water tank, and is pumped back into the waste heat boiler by the water pump to form a complete cycle. The scheme uses simulation software to achieve heat exchange, but it does not take into account the heat characteristics of high-temperature flue gas for targeted multi-stage utilization.

[0005] At present, there are the following problems in the treatment of high-temperature flue gas in metallurgical furnaces: (1) Flue gas cooling is generally carried out by drawing in cold air, which leads to heat loss; (2) Flue gas heating is generally carried out by heating and combustion, which wastes fuel and increases the production cost burden; (3) The temperature of the combustion air and oxidation air used for fuel combustion is room temperature. When they enter the furnace, they absorb some of the heat in the furnace, causing local thermal imbalance and oscillation in the furnace.

[0006] Therefore, there is an urgent need to propose a waste heat recovery method and system with efficient management of flue gas heat and high heat utilization rate. Summary of the Invention

[0007] In view of this, in order to achieve efficient management of flue gas heat and make effective use of flue gas heat, the present invention provides a waste heat recovery system for multi-stage utilization of high-temperature flue gas heat in a tilting furnace. This system has the characteristics of high heat utilization rate, simple process and multiple functions.

[0008] The first aspect of this application provides a waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace, comprising:

[0009] Hot flue gas and cooling gas undergo multi-stage heat exchange through a waste heat recovery system to recover waste heat. The hot flue gas includes the main flue gas from the waste heat boiler and the main flue gas heated by the GGH heat exchanger. The cooling gas includes combustion air, oxidation miscellaneous air, cooling protection air, and outdoor cold air.

[0010] The waste heat recovery method includes:

[0011] The main flue gas from the waste heat boiler enters the first gas-to-gas heat exchanger through the hot-side flue gas inlet. It exchanges heat with the main flue gas heated by the GGH heat exchanger, which enters the first gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in a first-stage heat exchange gas from the main flue gas from the waste heat boiler, exiting through the hot-side flue gas outlet of the first gas-to-gas heat exchanger, and a heat exchange gas from the main flue gas heated by the GGH heat exchanger, exiting through the cold-side flue gas outlet of the first gas-to-gas heat exchanger. This heat exchange gas from the main flue gas heated by the GGH heat exchanger is then input into the SCR denitrification reactor. The temperature of the main flue gas from the waste heat boiler is 450℃-700℃, and the flue gas flow rate is 11000 Nm³. 3 / h-22000Nm 3 / h, the temperature of the main flue gas after the GGH heat exchanger is heated is 190℃-360℃, and the flue gas flow rate of the main flue gas after the GGH heat exchanger is 23000Nm³. 3 / h-37000Nm 3 / h;

[0012] The first-stage heat exchange gas of the main flue gas of the waste heat boiler enters the first gas-water heat exchanger through the hot-side flue gas inlet and exchanges heat with the circulating water that enters the first gas-water heat exchanger through the cold-side flue gas inlet, thereby obtaining the second-stage heat exchange gas of the main flue gas of the waste heat boiler that is discharged through the hot-side flue gas outlet of the first gas-water heat exchanger and the heat exchange circulating water that is discharged through the cold-side flue gas outlet of the first gas-water heat exchanger.

[0013] The second-stage heat exchange gas of the main flue gas from the waste heat boiler enters the second gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the combustion air preheating gas that enters the second gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the third-stage heat exchange gas of the main flue gas from the waste heat boiler that exits through the hot-side flue gas outlet of the second gas-to-gas heat exchanger, and the combustion air heat exchange gas that exits through the cold-side flue gas outlet of the second gas-to-gas heat exchanger. The combustion air heat exchange gas is then input into the secondary combustion chamber. The combustion air preheating gas is obtained by preheating the combustion air through the second gas-water heat exchanger.

[0014] The third-stage heat exchange gas of the main flue gas from the waste heat boiler enters the third gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the outdoor cold air preheating gas that enters the third gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the fourth-stage heat exchange gas of the main flue gas from the waste heat boiler, which exits through the hot-side flue gas outlet of the third gas-to-gas heat exchanger, and the outdoor cold air heat exchange gas, which exits through the cold-side flue gas outlet of the third gas-to-gas heat exchanger. The outdoor cold air heat exchange gas, after heat exchange in the fourth gas-to-gas heat exchanger, exits through the hot-side flue gas outlet of the fourth gas-to-gas heat exchanger and is input into the workshop's cold material storage area. The fourth-stage heat exchange gas of the main flue gas from the waste heat boiler is input into a bag filter dust collector. The outdoor cold air preheating gas is obtained by preheating the outdoor cold air through the fourth gas-to-gas heat exchanger with the outdoor cold air heat exchange gas.

[0015] The heat exchange circulating water enters the second gas-water heat exchanger through the hot side flue gas inlet and exchanges heat with the combustion air. After heat exchange, the second hot circulating water is obtained. The second hot circulating water is discharged through the hot side flue gas outlet of the second gas-water heat exchanger and then enters the first gas-water heat exchanger for circulating heat exchange.

[0016] The heat exchange circulating water enters the third gas-water heat exchanger through the hot-side flue gas inlet and preheats with the oxidation mixed air or the cooling protection air. After heat exchange, the third hot circulating water and the oxidation mixed air preheated gas or the cooling protection air preheated gas are obtained. The third hot circulating water is discharged through the hot-side flue gas outlet of the third gas-water heat exchanger and then circulates in the first gas-water heat exchanger for heat exchange. The oxidation mixed air and the cooling protection air enter the third gas-water heat exchanger respectively.

[0017] Optionally, the temperature of the main flue gas from the waste heat boiler is independently selected from any value among 450℃, 475℃, 500℃, 550℃, 600℃, 650℃, and 700℃, or any range between any two of the above.

[0018] Optionally, the flue gas volume of the main flue gas from the waste heat boiler is independently selected from 11000 Nm³.3 / h, 11560Nm 3 / h, 12970Nm 3 / h、15225Nm 3 / h, 16500Nm 3 / h, 17500Nm 3 / h, 20000Nm 3 / h, 21000Nm 3 / h, 22000Nm 3 / h can be any value or any range between any two of the above points.

[0019] The temperature of the main flue gas after the GGH heat exchanger is heated is independently selected from any value among 190℃, 220℃, 240℃, 270℃, 273℃, 285℃, 300℃, 315℃, 345℃, and 360℃, or any range between any two of the above points.

[0020] After the GGH heat exchanger is heated, the flue gas volume of the main flue gas is independently selected from 23000 Nm³. 3 / h、24368Nm 3 / h、28605Nm 3 / h, 31000Nm 3 / h, 34500Nm 3 / h, 37000Nm 3 / h can be any value or any range between any two of the above points.

[0021] Optionally, the temperature of the oxidizing air is -10℃ to 45℃;

[0022] And / or, the temperature of the cooling protective air is -10℃ to 45℃;

[0023] And / or, the temperature of the outdoor cold air is -10℃ to 45℃;

[0024] And / or, the temperature of the combustion air is 40℃-75℃;

[0025] And / or, the temperatures of the oxidation-resistant preheating gas, the cooling-protection preheating gas, the outdoor cold air preheating gas, and the combustion-supporting preheating gas are independently 80°C-90°C;

[0026] And / or, the temperature of the outdoor cold air heat exchanger is 90℃-120℃;

[0027] And / or, the temperature of the combustion air heat exchanger is 90℃-400℃.

[0028] Optionally, the combustion-supporting air volume is 500 Nm³. 3 / h-4000Nm3 / h;

[0029] And / or, the volume of the oxidation-related air is 1200 Nm³. 3 / h-3300Nm 3 / h;

[0030] And / or, the airflow of the cooling protection air is 380 Nm³. 3 / h-600Nm 3 / h;

[0031] And / or, the outdoor cold air volume is 150 Nm³. 3 / h-400Nm 3 / h.

[0032] Optionally, the intake pressure of the combustion air is 0.1 MPa to 0.6 MPa;

[0033] And / or, the inlet pressure of the oxidizing air is 0.4 MPa-0.6 MPa;

[0034] And / or, the intake pressure of the cooling protection air is 0.4 MPa-0.6 MPa;

[0035] And / or, the intake pressure of the outdoor cold air is 0.1 MPa-0.3 MPa.

[0036] Optionally, in the first gas-water heat exchanger, the temperature of the circulating water entering from the cold-side flue gas inlet of the first gas-water heat exchanger is 75℃-85℃, and the temperature of the heat exchange circulating water exiting from the cold-side flue gas outlet of the first gas-water heat exchanger is 85℃-100℃.

[0037] Optionally, in the waste heat recovery method, the heat exchange method is cross-flow heat exchange or counter-current convection heat exchange.

[0038] A second aspect of this application provides a waste heat recovery system for multi-stage utilization of heat from tilting furnace flue gas, used to implement the aforementioned waste heat recovery method for multi-stage utilization of heat from tilting furnace flue gas, the waste heat recovery system comprising:

[0039] The main heat exchange module includes a first gas-to-gas heat exchanger, a second gas-to-gas heat exchanger, and a third gas-to-gas heat exchanger, which are connected in series on the main pipeline of the waste heat recovery system. The hot-side flue gas outlet of the first gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the second gas-to-gas heat exchanger, and the hot-side flue gas outlet of the second gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the third gas-to-gas heat exchanger.

[0040] A preheating heat exchanger module includes a first gas-water heat exchanger, a second gas-water heat exchanger, a third gas-water heat exchanger, and a fourth gas-gas heat exchanger. The first gas-water heat exchanger is connected in series on the main pipeline connecting the first gas-gas heat exchanger and the second gas-gas heat exchanger. The hot-side flue gas inlet of the first gas-water heat exchanger is connected to the hot-side flue gas outlet of the first gas-gas heat exchanger, and the hot-side flue gas outlet of the first gas-water heat exchanger is connected to the hot-side flue gas inlet of the second gas-gas heat exchanger. The second gas-water heat exchanger is connected in series with the second gas-gas heat exchanger on a first branch pipeline. The cold-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the second gas-gas heat exchanger. The fourth gas-gas heat exchanger and the third gas-gas heat exchanger are connected on a second branch pipeline. The cold-side flue gas outlet of the fourth gas-gas heat exchanger is connected to the cold-side flue gas inlet of the third gas-gas heat exchanger, and the cold-side flue gas outlet of the third gas-gas heat exchanger is connected to the hot-side flue gas inlet of the fourth gas-gas heat exchanger.

[0041] The second gas-water heat exchanger is connected in series with the first gas-water heat exchanger, wherein the hot-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger; and the hot-side flue gas inlet of the second gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger.

[0042] The third gas-water heat exchanger is connected in series with the first gas-water heat exchanger, wherein the hot-side flue gas inlet of the third gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger; and the hot-side flue gas outlet of the third gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger.

[0043] Optionally, the heat exchangers in the waste heat recovery system are all micro heat pipe array heat exchangers.

[0044] Optionally, the heat exchangers in the waste heat recovery system all contain a vibration cleaning device.

[0045] Compared with the prior art, the waste heat recovery method and system for multi-stage utilization of flue gas heat in a tilting furnace provided by the present invention achieves at least the following beneficial effects:

[0046] First, the heat of the high-temperature flue gas in the tilting furnace is effectively utilized through multiple stages, reducing heat loss;

[0047] Secondly, after the GGH heat exchanger is heated, the main flue gas exchanges heat with the high-temperature flue gas of the tilting furnace. After the GGH heat exchanger is heated, the main flue gas enters the SCR denitrification system, reducing production costs.

[0048] Third, the combustion air and oxidation air used for fuel combustion are preheated before entering the furnace, which can reduce the heat loss caused by unheated gas entering the furnace and avoid the problem of local thermal imbalance and oscillation caused by absorbing heat from the furnace.

[0049] Fourth, the heat from the high-temperature flue gas in the tilting furnace is effectively utilized in multiple stages, which not only achieves energy conservation and emission reduction, but also reduces the heat load of environmental protection equipment such as dust removal and desulfurization. At the same time, it can be applied to the smelting industry and other high-temperature flue gas treatment.

[0050] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0051] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0052] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0053] Figure 1 This application provides a waste heat recovery system for multi-stage utilization of high-temperature flue gas heat from a tilting furnace, and the heat transfer path of the gas medium within the system. Detailed Implementation

[0054] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0055] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0056] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0057] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0058] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0059] In existing technologies, high-temperature flue gas in metallurgical furnaces is generally cooled by drawing in cold air, resulting in heat loss. Furthermore, the flue gas is typically heated and burned, wasting fuel and increasing production costs. In addition, the combustion air and oxidizing air used for fuel combustion are at room temperature; these airs enter the furnace and absorb some of the heat, causing localized thermal imbalances and oscillations within the furnace.

[0060] To address the aforementioned technical problems and achieve efficient management and effective utilization of flue gas heat, this invention provides a waste heat recovery method for multi-stage utilization of flue gas heat in a tilting furnace. This method features high heat utilization rate, simple process, and diverse functions.

[0061] like Figure 1 As shown, Figure 1 This application provides a waste heat recovery system for multi-stage utilization of high-temperature flue gas heat from a tilting furnace, and the heat transfer path of the gas medium within the system.

[0062] The waste heat recovery method provided by this invention includes: the gaseous medium involved includes hot flue gas and cooling gas, and the waste heat is recovered through multi-stage heat exchange in a waste heat recovery system. The hot flue gas includes the main flue gas of the waste heat boiler and the main flue gas after heating by the GGH heat exchanger. The cooling gas includes combustion air, oxidation miscellaneous air, cooling protection air, and outdoor cold air. It should be noted that the main flue gas of the waste heat boiler and the main flue gas after heating by the GGH heat exchanger are medium-high temperature flue gas.

[0063] The heat transfer path of the gaseous medium in the waste heat recovery system is as follows:

[0064] The main flue gas from the waste heat boiler enters the first gas-to-gas heat exchanger through the hot-side inlet. It exchanges heat with the main flue gas heated by the GGH heat exchanger, which enters the first gas-to-gas heat exchanger through the cold-side inlet. This results in a first-stage heat exchange gas (the main flue gas from the waste heat boiler discharged through the hot-side outlet of the first gas-to-gas heat exchanger) and a heat exchange gas (the main flue gas heated by the GGH heat exchanger discharged through the cold-side outlet of the first gas-to-gas heat exchanger). This heat exchange gas is then fed into the SCR denitrification reactor. The temperature of the main flue gas from the waste heat boiler is 450℃-700℃, and its flow rate is 11000 Nm³. 3 / h-22000Nm 3 / h, after the GGH heat exchanger is heated, the temperature of the main flue gas is 190℃-360℃, and the flue gas flow rate is 23000Nm³. 3 / h-37000Nm 3 / h;

[0065] The first-stage heat exchange gas of the main flue gas of the waste heat boiler enters the first gas-water heat exchanger through the hot-side flue gas inlet and exchanges heat with the circulating water that enters the first gas-water heat exchanger through the cold-side flue gas inlet. This results in the second-stage heat exchange gas of the main flue gas of the waste heat boiler that is discharged through the hot-side flue gas outlet of the first gas-water heat exchanger and the heat exchange circulating water that is discharged through the cold-side flue gas outlet of the first gas-water heat exchanger.

[0066] The second-stage heat exchange gas of the main flue gas from the waste heat boiler enters the second gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the combustion air preheating gas that enters the second gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the third-stage heat exchange gas of the main flue gas from the waste heat boiler that exits through the hot-side flue gas outlet of the second gas-to-gas heat exchanger, and the combustion air heat exchange gas that exits through the cold-side flue gas outlet of the second gas-to-gas heat exchanger. The combustion air heat exchange gas is then input into the secondary combustion chamber. The combustion air preheating gas is obtained by preheating the combustion air through the second gas-water heat exchanger.

[0067] The third-stage heat exchange gas of the main flue gas from the waste heat boiler enters the third gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the outdoor cold air preheating gas that enters the third gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the fourth-stage heat exchange gas of the main flue gas from the waste heat boiler that exits through the hot-side flue gas outlet of the third gas-to-gas heat exchanger, and the outdoor cold air heat exchange gas that exits through the cold-side flue gas outlet of the third gas-to-gas heat exchanger. After heat exchange in the fourth gas-to-gas heat exchanger, the outdoor cold air heat exchange gas exits through the hot-side flue gas outlet of the fourth gas-to-gas heat exchanger and is fed into the cold material storage area of ​​the workshop. The fourth-stage heat exchange gas of the main flue gas from the waste heat boiler is fed into the bag filter dust collector. The outdoor cold air preheating gas is obtained by preheating the outdoor cold air through the fourth gas-to-gas heat exchanger with the outdoor cold air heat exchange gas.

[0068] The heat exchange circulating water enters the second gas-water heat exchanger through the hot side flue gas inlet and exchanges heat with the combustion air. After heat exchange, the second hot circulating water is obtained. The second hot circulating water is discharged through the hot side flue gas outlet of the second gas-water heat exchanger and then enters the first gas-water heat exchanger for circulating heat exchange.

[0069] The heat exchange circulating water enters the third gas-water heat exchanger through the hot-side flue gas inlet and preheats with the oxidation mixed air or cooling protection air. After heat exchange, the third hot circulating water and the oxidation mixed air preheated gas or cooling protection air preheated gas are obtained. The third hot circulating water is discharged through the hot-side flue gas outlet of the third gas-water heat exchanger and then circulates in the first gas-water heat exchanger for heat exchange. The oxidation mixed air and the cooling protection air enter the third gas-water heat exchanger respectively.

[0070] It should be noted that in this invention, the main flue gas after the GGH heat exchanger is heated is the flue gas after the main flue gas of the waste heat boiler has been purified and desulfurized, and has the characteristics of large flue gas volume and good heat transfer effect.

[0071] In this invention, the combustion air comes from a mixture of flue gas overflowing from the tilting furnace and outdoor air. This ensures that combustible organic matter escaping from the tilting furnace is fully combusted in the secondary combustion chamber, preventing flash explosions in the flue, avoiding low-altitude pollution and improving production safety, while also saving energy consumption of the secondary combustion chamber fan.

[0072] In this invention, the oxidation mixed air and cooling protection air are heated before being sent into the furnace, which can reduce the heat loss caused by unheated gas entering the furnace.

[0073] In this invention, the cooling gas is preheated before heat exchange, which can prevent the combination of acidic and other corrosive gases and water vapor in the flue gas, thus avoiding the generation or aggravation of low-temperature corrosion on the heat exchanger equipment.

[0074] In some optional embodiments provided by the present invention, the cooling gas must be preheated and then reheated before entering the main heat exchanger pipeline (such as the second gas-to-gas heat exchanger or the third gas-to-gas heat exchanger). Specifically, the temperature of the oxidation-mixed air is -10℃ to 45℃; and / or the temperature of the cooling protection air is -10℃ to 45℃; and / or the temperature of the outdoor cold air is -10℃ to 45℃; and / or the temperature of the combustion-supporting air is 40℃ to 75℃; and / or the temperature of the oxidation-mixed air preheating gas is 80℃ to 90℃; and / or the temperature of the cooling protection air preheating gas is 80℃ to 90℃; and / or the temperature of the outdoor cold air preheating gas is 80℃ to 90℃; and / or the temperature of the combustion-supporting air preheating gas is 80℃ to 90℃; and / or the temperature of the outdoor cold air heat exchange gas is 90℃ to 120℃; and / or the temperature of the combustion-supporting air heat exchange gas is 90℃ to 400℃.

[0075] In some optional embodiments provided by the present invention, the combustion air volume is 500 Nm³. 3 / h-4000Nm 3 / h; and / or the volume of the oxidizing air is 1200Nm 3 / h-3300Nm 3 / h; and / or the airflow of the cooling protection air is 380Nm 3 / h-600Nm 3 / h; and / or the airflow of cold outdoor air is 150Nm 3 / h-400Nm 3 / h.

[0076] In some optional embodiments provided by the present invention, the intake pressure of the combustion-supporting air is 0.1 MPa-0.6 MPa; and / or the intake pressure of the oxidation-mixed air is 0.4 MPa-0.6 MPa; and / or the intake pressure of the cooling protection air is 0.4 MPa-0.6 MPa; and / or the intake pressure of the outdoor cold air is 0.1 MPa-0.3 MPa.

[0077] In some optional embodiments provided by the present invention, the temperature of the circulating water entering from the cold side flue gas inlet of the first gas-water heat exchanger is 75°C-85°C, and the temperature of the heat exchange circulating water exiting from the cold side flue gas outlet of the first gas-water heat exchanger is 85°C-100°C.

[0078] It should be noted that the first gas-water heat exchanger is connected to the second and third gas-water heat exchangers respectively, and performs cyclical heat exchange. The process is that the circulating water of the first gas-water heat exchanger, after heat exchange, flows through the second and third gas-water heat exchangers respectively. After preheating the cooling gas, it flows back into the first gas-water heat exchanger for heat exchange. The inlet circulating water temperature of the first gas-water heat exchanger is 75℃-85℃, and the outlet temperature is 85℃-100℃. That is, the second and third gas-water heat exchangers are set independently and connected to the first gas-water heat exchanger respectively, which can ensure that the preheating efficiency of the second and third gas-water heat exchangers meets the requirements of the present invention.

[0079] In some optional embodiments provided by this invention, the waste heat recovery method employs either cross-flow heat exchange or counter-current convection heat exchange. Specifically, the heat exchanger has two inlets (hot-side flue gas inlet and cold-side flue gas inlet) and two outlets (hot-side flue gas outlet and cold-side flue gas outlet). The hot-side flue gas inlets and outlets are arranged along the gas flow direction, and the cold-side flue gas inlets and outlets are similarly arranged. The heat exchange method in this invention features a large heat exchange area, which facilitates rapid heat transfer and results in a significant heat exchange effect.

[0080] like Figure 1 As shown in the embodiment of this application, a waste heat recovery system for multi-stage utilization of high-temperature flue gas heat from a tilting furnace is provided, which consists of heat exchange gas modules with different functions, including:

[0081] The main heat exchange module includes a first gas-to-gas heat exchanger, a second gas-to-gas heat exchanger, and a third gas-to-gas heat exchanger, which are connected in series on the main pipeline of the waste heat recovery system. The hot-side flue gas outlet of the first gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the second gas-to-gas heat exchanger, and the hot-side flue gas outlet of the second gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the third gas-to-gas heat exchanger.

[0082] The preheating heat exchanger module includes a first gas-water heat exchanger, a second gas-water heat exchanger, a third gas-water heat exchanger, and a fourth gas-gas heat exchanger. The first gas-water heat exchanger is connected in series on the main pipeline connecting the first gas-gas heat exchanger and the second gas-gas heat exchanger. The hot-side flue gas inlet of the first gas-water heat exchanger is connected to the hot-side flue gas outlet of the first gas-gas heat exchanger, and the hot-side flue gas outlet of the first gas-water heat exchanger is connected to the hot-side flue gas inlet of the second gas-gas heat exchanger. The second gas-water heat exchanger and the second gas-gas heat exchanger are connected in series on a first branch pipeline. The cold-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the second gas-gas heat exchanger. The fourth gas-gas heat exchanger and the third gas-gas heat exchanger are connected on a second branch pipeline. The cold-side flue gas outlet of the fourth gas-gas heat exchanger is connected to the cold-side flue gas inlet of the third gas-gas heat exchanger, and the cold-side flue gas outlet of the third gas-gas heat exchanger is connected to the hot-side flue gas inlet of the fourth gas-gas heat exchanger.

[0083] The second gas-water heat exchanger is connected in series with the first gas-water heat exchanger. The hot-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger. The hot-side flue gas inlet of the second gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger.

[0084] The third gas-water heat exchanger is connected in series with the first gas-water heat exchanger. The hot-side flue gas inlet of the third gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger; the hot-side flue gas outlet of the third gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger.

[0085] In some optional embodiments provided by the present invention, the heat exchangers in the waste heat recovery system are all micro heat pipe array heat exchangers.

[0086] In some optional embodiments provided by the present invention, the heat exchangers in the waste heat recovery system all include a vibration cleaning device. Specifically, the vibration cleaning device includes, but is not limited to, ultrasonic cleaning, mechanical vibration cleaning, and airflow purging.

[0087] The heat exchanger of this invention contains a powerful dust removal device, which can prevent the heat exchange efficiency from decreasing due to the accumulation of dust on the heat exchanger wall tubes, and can ensure efficient heat exchange.

[0088] Example

[0089] This embodiment illustrates the application of the method and system of the present invention in the multi-stage utilization of high-temperature flue gas heat from a tilting furnace at the Guixi Smelter of Jiangxi Copper Corporation. The energy-saving details of the tilting furnace heat exchange system at different cycles are shown in the table below.

[0090] Table 1 Feeding Period

[0091]

[0092]

[0093] Table 2 Oxidation period

[0094]

[0095] Table 3 Reduction Period

[0096]

[0097]

[0098] Table 4 Casting Period

[0099]

[0100] Saves heat and energy:

[0101] (1) Combustion air heating saves energy (including the second gas-to-gas heat exchanger and the second gas-to-water heat exchanger):

[0102] (219 x 11 + 253 x 5 + 272 x 2.0 + 96 x 4.5 + 25 x 11 + 25 x 5 + 43 x 2 + 12 x 4.5) x 3600 = 1.87 x 10 4 MJ;

[0103] (2) Energy saving through heating of mixed oxidation air and cooling protection air (third gas-water heat exchanger):

[0104] (11 x 11 + 66 x 5 + 11 x 2 + 11 x 4.5) x 3600 = 1.88 x 10 3 MJ;

[0105] (3) After the air is heated by the third air-to-air heat exchanger, it is sent to the cold material zone. Considering the heat loss, it is estimated to be 20% of the calculated heating amount. The energy saved by heating (third air-to-air heat exchanger):

[0106] (976 x 11 + 1185 x 5 + 596 x 2 + 606 x 4.5) x 3600 x 20% = 1.48 x 10 4 MJ;

[0107] (4) Therefore, the total energy saving of the heat exchange system during a complete furnace cycle (22.5h) is:

[0108] 1.87 x 10 4 +1.88 x 10 3 +1.48 x 10 4 =3.538 x 10 4 MJ, calculated based on the calorific value of natural gas 36506 KJ / Nm3, is equivalent to approximately 969 Nm3 of natural gas.

[0109] Assuming the system operates for 340 days a year, 24 hours a day, and considering actual fluctuations, with an annual energy saving of 62% for the heat exchanger, the annual fuel saving for the heat exchange system is:

[0110] 950 x 24 / 22.5 x 340 x 0.62 = 2.18 x 10 5 m 3 .

[0111] The functions of each heat exchanger in the waste heat recovery system for multi-stage utilization of high-temperature flue gas heat in a tilting furnace provided in this embodiment are summarized in Table 5 below:

[0112] Table 5

[0113]

[0114]

[0115] As can be seen from the above embodiments, the waste heat recovery method and system for multi-stage utilization of flue gas heat in a tilting furnace provided by the present invention achieves at least the following beneficial effects:

[0116] In this invention, the flue gas from the tilting furnace undergoes heat exchange in a waste heat boiler, and then efficiently exchanges heat with different medium- and low-temperature gases through a multi-stage series main heat exchanger. This invention has advantages such as simple process, diverse functions, and efficient heat utilization, and can be applied to the utilization of high-temperature flue gas waste heat in other metallurgical furnaces and kilns. Specifically, after the main flue gas from the waste heat boiler at the boiler outlet undergoes multi-stage cooling, the final heat exchanger ensures the temperature drops below 200℃. Each stage of cooling transfers heat to other gaseous media, which are then used in production. The heat exchange system can save up to 2.18 x 10 times the amount of fuel gas annually. 5 m3.

[0117] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A method for multi-stage utilization of waste heat from flue gas in a tilting furnace, characterized in that, include: Hot flue gas and cooling gas undergo multi-stage heat exchange through a waste heat recovery system to recover waste heat. The hot flue gas includes the main flue gas from the waste heat boiler and the main flue gas heated by the GGH heat exchanger. The cooling gas includes combustion air, oxidation miscellaneous air, cooling protection air, and outdoor cold air. The waste heat recovery method includes: The main flue gas from the waste heat boiler enters the first gas-to-gas heat exchanger through the hot-side flue gas inlet. It exchanges heat with the main flue gas heated by the GGH heat exchanger, which enters the first gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in a first-stage heat exchange gas from the main flue gas from the waste heat boiler, exiting through the hot-side flue gas outlet of the first gas-to-gas heat exchanger, and a heat exchange gas from the main flue gas heated by the GGH heat exchanger, exiting through the cold-side flue gas outlet of the first gas-to-gas heat exchanger. This heat exchange gas from the main flue gas heated by the GGH heat exchanger is then input into the SCR denitrification reactor. The temperature of the main flue gas from the waste heat boiler is 450℃-700℃, and the flue gas flow rate is 11000 Nm³. 3 / h-22000Nm 3 / h, the temperature of the main flue gas after the GGH heat exchanger is heated is 190℃-360℃, and the flue gas flow rate of the main flue gas after the GGH heat exchanger is 23000Nm³. 3 / h-37000Nm 3 / h; The first-stage heat exchange gas of the main flue gas of the waste heat boiler enters the first gas-water heat exchanger through the hot-side flue gas inlet and exchanges heat with the circulating water that enters the first gas-water heat exchanger through the cold-side flue gas inlet, thereby obtaining the second-stage heat exchange gas of the main flue gas of the waste heat boiler that is discharged through the hot-side flue gas outlet of the first gas-water heat exchanger and the heat exchange circulating water that is discharged through the cold-side flue gas outlet of the first gas-water heat exchanger. The second-stage heat exchange gas of the main flue gas from the waste heat boiler enters the second gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the combustion air preheating gas that enters the second gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the third-stage heat exchange gas of the main flue gas from the waste heat boiler that exits through the hot-side flue gas outlet of the second gas-to-gas heat exchanger, and the combustion air heat exchange gas that exits through the cold-side flue gas outlet of the second gas-to-gas heat exchanger. The combustion air heat exchange gas is then input into the secondary combustion chamber. The combustion air preheating gas is obtained by preheating the combustion air through the second gas-water heat exchanger. The third-stage heat exchange gas of the main flue gas from the waste heat boiler enters the third gas-to-gas heat exchanger through the hot-side flue gas inlet, and exchanges heat with the outdoor cold air preheating gas that enters the third gas-to-gas heat exchanger through the cold-side flue gas inlet. This results in the fourth-stage heat exchange gas of the main flue gas from the waste heat boiler, which exits through the hot-side flue gas outlet of the third gas-to-gas heat exchanger, and the outdoor cold air heat exchange gas, which exits through the cold-side flue gas outlet of the third gas-to-gas heat exchanger. The outdoor cold air heat exchange gas, after heat exchange in the fourth gas-to-gas heat exchanger, exits through the hot-side flue gas outlet of the fourth gas-to-gas heat exchanger and is input into the workshop's cold material storage area. The fourth-stage heat exchange gas of the main flue gas from the waste heat boiler is input into a bag filter dust collector. The outdoor cold air preheating gas is obtained by preheating the outdoor cold air through the fourth gas-to-gas heat exchanger with the outdoor cold air heat exchange gas. The heat exchange circulating water enters the second gas-water heat exchanger through the hot side flue gas inlet and exchanges heat with the combustion air. After heat exchange, the second hot circulating water is obtained. The second hot circulating water is discharged through the hot side flue gas outlet of the second gas-water heat exchanger and then enters the first gas-water heat exchanger for circulating heat exchange. The heat exchange circulating water enters the third gas-water heat exchanger through the hot-side flue gas inlet and preheats with the oxidation mixed air or the cooling protection air. After heat exchange, the third hot circulating water and the oxidation mixed air preheated gas or the cooling protection air preheated gas are obtained. The third hot circulating water is discharged through the hot-side flue gas outlet of the third gas-water heat exchanger and then circulates in the first gas-water heat exchanger for heat exchange. The oxidation mixed air and the cooling protection air enter the third gas-water heat exchanger respectively.

2. The waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace according to claim 1, characterized in that, The temperature of the oxidizing air is -10℃ to 45℃; And / or, the temperature of the cooling protective air is -10℃ to 45℃; And / or, the temperature of the outdoor cold air is -10℃ to 45℃; And / or, the temperature of the combustion air is 40℃-75℃; And / or, the temperatures of the oxidation-resistant preheating gas, the cooling-protection preheating gas, the outdoor cold air preheating gas, and the combustion-supporting preheating gas are independently 80°C-90°C; And / or, the temperature of the outdoor cold air heat exchanger is 90℃-120℃; And / or, the temperature of the combustion air heat exchanger is 90℃-400℃.

3. The waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace according to claim 1, characterized in that, The volume of the combustion-supporting air is 500 Nm³. 3 / h-4000Nm 3 / h; And / or, the volume of the oxidation-related air is 1200 Nm³. 3 / h-3300Nm 3 / h; And / or, the airflow of the cooling protection air is 380 Nm³. 3 / h-600Nm 3 / h; And / or, the outdoor cold air volume is 150 Nm³. 3 / h-400Nm 3 / h.

4. The waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace according to claim 1, characterized in that, The intake pressure of the combustion air is 0.1 MPa to 0.6 MPa; And / or, the inlet pressure of the oxidizing air is 0.4 MPa-0.6 MPa; And / or, the intake pressure of the cooling protection air is 0.4 MPa-0.6 MPa; And / or, the intake pressure of the outdoor cold air is 0.1 MPa-0.3 MPa.

5. The waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace according to claim 1, characterized in that, Inside the first gas-water heat exchanger, the temperature of the circulating water entering from the cold-side flue gas inlet of the first gas-water heat exchanger is 75℃-85℃, and the temperature of the heat exchange circulating water exiting from the cold-side flue gas outlet of the first gas-water heat exchanger is 85℃-100℃.

6. The waste heat recovery method for multi-stage utilization of flue gas heat from a tilting furnace according to claim 1, characterized in that, In the waste heat recovery method, the heat exchange method is cross-flow heat exchange or counter-current convection heat exchange.

7. A waste heat recovery system for multi-stage utilization of flue gas heat from a tilting furnace, characterized in that, A waste heat recovery method for realizing multi-stage utilization of flue gas heat from a tilting furnace as described in any one of claims 1-6; the waste heat recovery system includes: The main heat exchange module includes a first gas-to-gas heat exchanger, a second gas-to-gas heat exchanger, and a third gas-to-gas heat exchanger, which are connected in series on the main pipeline of the waste heat recovery system. The hot-side flue gas outlet of the first gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the second gas-to-gas heat exchanger, and the hot-side flue gas outlet of the second gas-to-gas heat exchanger is connected to the hot-side flue gas inlet of the third gas-to-gas heat exchanger. The preheating heat exchanger module includes a first gas-water heat exchanger, a second gas-water heat exchanger, a third gas-water heat exchanger, and a fourth gas-gas heat exchanger. The first gas-water heat exchanger is connected in series on the main pipeline connecting the first gas-gas heat exchanger and the second gas-gas heat exchanger. The hot-side flue gas inlet of the first gas-water heat exchanger is connected to the hot-side flue gas outlet of the first gas-gas heat exchanger, and the hot-side flue gas outlet of the first gas-water heat exchanger is connected to the hot-side flue gas inlet of the second gas-gas heat exchanger. The second gas-water heat exchanger is connected in series with the second gas-gas heat exchanger on a first branch pipeline. The cold-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the second gas-gas heat exchanger. The fourth gas-gas heat exchanger and the third gas-gas heat exchanger are connected on a second branch pipeline. The cold-side flue gas outlet of the fourth gas-gas heat exchanger is connected to the cold-side flue gas inlet of the third gas-gas heat exchanger, and the cold-side flue gas outlet of the third gas-gas heat exchanger is connected to the hot-side flue gas inlet of the fourth gas-gas heat exchanger. The second gas-water heat exchanger is connected in series with the first gas-water heat exchanger, wherein the hot-side flue gas outlet of the second gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger; and the hot-side flue gas inlet of the second gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger. The third gas-water heat exchanger is connected in series with the first gas-water heat exchanger, wherein the hot-side flue gas inlet of the third gas-water heat exchanger is connected to the cold-side flue gas outlet of the first gas-water heat exchanger; and the hot-side flue gas outlet of the third gas-water heat exchanger is connected to the cold-side flue gas inlet of the first gas-water heat exchanger.

8. The waste heat recovery system according to claim 7, characterized in that, The heat exchangers in the waste heat recovery system are all micro heat pipe array heat exchangers.

9. The waste heat recovery system according to claim 7, characterized in that, The heat exchangers in the waste heat recovery system all contain a vibration cleaning device.

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