High-efficiency and energy-saving type aluminum melting furnace external SCR (Selective Catalytic Reduction) denitration system

Abstract

The utility model belongs to the technical field of metallurgical flue gas treatment, and particularly discloses a high-efficiency energy-saving aluminum melting furnace external SCR (Selective Catalytic Reduction) denitration system which comprises an aluminum melting furnace, a heat accumulator, a flue gas direct combustion heating device, a urea pyrolysis device, an ammonia spraying and mixing device and an SCR denitration reactor, flue gas generated by the aluminum melting furnace is heated by the flue gas direct-combustion heating device after being subjected to temperature stabilization through the heat accumulator, the flue gas and ammonia gas generated by the urea pyrolysis device are mixed in the ammonia spraying and mixing device and enter the SCR denitration reactor for reaction, and an integrated design is adopted. The system further comprises an ammonia flow adjusting device for adjusting the ammonia amount, a flue gas / air heat exchanger and the like. The SCR denitration system disclosed by the utility model can effectively solve the problems of large temperature fluctuation of the flue gas outlet of the aluminum melting furnace, high nitrogen oxide concentration, large fluctuation and the like, energy consumption, operation cost and occupied area of a plant are reduced while high-efficiency denitration is ensured, the utilization rate of equipment is improved, and the influence on production is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of metallurgical fume treatment, and in particular relates to a high-efficiency and energy-saving SCR denitration system outside an aluminum melting furnace. Background Art

[0002] As is known in the industry, aluminum melting furnaces, as key metallurgical equipment in the aluminum product manufacturing industry, typically consist of a furnace body, heating elements, insulation materials, and a control system. The furnace body is constructed of high-temperature refractory materials. The furnace heats the aluminum material contained within the furnace to a molten state by burning fuel or utilizing electricity to generate high temperatures. In other words, the primary function of an aluminum melting furnace is to melt the aluminum material at high temperatures and control the composition of the molten aluminum to meet the requirements of subsequent processing.

[0003] During the aluminum liquid production process, the temperature of the aluminum melting furnace is typically between 700°C and 740°C, with the highest temperature inside the furnace even exceeding 1000°C. In such a high-temperature environment, nitrogen oxides (NOx) that do not meet environmental protection requirements are easily generated, and therefore need to be treated. Furthermore, because the aluminum melting furnace operates intermittently, with frequent starts and stops, flue gas of varying temperatures and concentrations is emitted during different production periods. This results in flue gas with large outlet temperature fluctuations (less than 150°C at low temperatures and greater than 300°C at high temperatures), high NOx concentrations, and significant volatility. Therefore, achieving ultra-low and stable NOx emissions in the flue gas is quite challenging.

[0004] Currently, denitrification treatment methods for aluminum smelting furnace flue gas are mainly divided into two types: in-furnace denitrification and off-furnace denitrification. The advantage of in-furnace denitrification is its relatively simple equipment and minimal furnace modification requirements. However, its disadvantages are also significant: relatively low denitrification efficiency and poor stability. The high temperature in the furnace makes it difficult to precisely control reaction conditions, and it may also affect the smelting process. Furthermore, the high temperature in the furnace can easily cause explosions and other safety hazards, making denitrification technologies using ammonia or urea solutions as reducing agents unusable. Off-furnace denitrification has the advantage of precise control of reaction temperature and the use of mature technologies such as SCR, which can achieve high and stable denitrification efficiency. However, the exhaust temperature of aluminum smelting furnaces is below 150°C at low temperatures. To maintain the stable operation of the SCR denitrification system, the flue gas must be heated (because the catalyst in the SCR denitrification reactor only efficiently reacts with ammonia and nitrogen oxides at 230°C). This significantly increases energy consumption and operating costs. Furthermore, the existing, established ammonia production stations, reducing agent storage stations, and denitrification reactors—a series of independent and complex equipment—occupy large areas and incur high investment and operating costs. Furthermore, the aluminum melting furnace production system operates cyclically and intermittently, and the high-cost retrofit of denitrification equipment results in low utilization rates, resulting in a waste of resources and a serious impact on the company's economic performance.

[0005] In summary, the existing SCR denitrification technology has many problems when applied to the flue gas treatment of aluminum melting furnaces. Therefore, there is an urgent need to develop an efficient, economical, practical denitrification system that is specifically tailored to the characteristics of aluminum melting furnace flue gas and has less impact on production.

[0006] In view of this, this utility model is proposed. Utility Model Content

[0007] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace, which is mainly used to solve the problems of large outlet temperature fluctuations, high and fluctuating nitrogen oxide concentrations of the flue gas generated by the aluminum melting furnace, which makes it difficult for existing mature denitrification technologies to achieve high and stable denitrification efficiency. The SCR denitrification system can reduce energy consumption and operating costs while ensuring efficient denitrification, improve equipment utilization, and reduce the impact on production.

[0008] The purpose of this utility model is to solve the problem through the following technical solutions:

[0009] The utility model provides a high-efficiency and energy-saving SCR denitration system outside an aluminum melting furnace, which includes a base, an aluminum melting furnace, a heat storage body, a flue gas direct-fired heating device, a urea pyrolysis device, an ammonia injection mixing device and an SCR denitration reactor;

[0010] The air outlet of the aluminum melting furnace is connected to the air inlet of the thermal storage body through a first pipeline, which is used to stabilize the temperature fluctuation of the flue gas generated by the aluminum melting furnace. The air outlet of the thermal storage body is connected to the flue gas direct-fired heating device through a second pipeline. The flue gas direct-fired heating device heats the flue gas that has been treated by the thermal storage body and has not reached the set temperature, and mixes it with the ammonia generated by the pyrolysis of the urea device in an ammonia injection mixing device to form an ammonia / flue gas mixture. The air outlet of the ammonia injection mixing device is connected to the SCR denitration reactor through a third pipeline. Under the action of the catalyst, the ammonia and nitrogen oxides undergo an oxidation-reduction reaction to generate nitrogen and water.

[0011] The flue gas direct combustion heating device, urea thermal decomposition device and ammonia injection mixing device adopt an integrated design.

[0012] Furthermore, the flue gas direct combustion heating device includes a vertically arranged cylinder and a first burner;

[0013] The cylinder body is composed of an inner cylinder and an outer cylinder which is sleeved on the outer cylinder and located below the inner cylinder. The upper portion of the outer cylinder is provided with a flue gas interface connected to a second pipeline. A monitoring meter for monitoring flue gas temperature and nitrogen oxide concentration is installed on the second pipeline. The top end of the outer cylinder is sealed with the outer wall of the inner cylinder, and the bottom end of the outer cylinder is sealed.

[0014] The first burner is fixedly installed at the bottom seal of the outer tube. The first fire tube of the first burner passes through the bottom seal of the outer tube and extends into the bottom of the inner tube, and is used to preheat the flue gas between the outer tube and the inner tube and heat the flue gas entering the inner tube.

[0015] Furthermore, the first fire tube is provided with a first interface and a second interface at a distance from one side of the first fire tube that is exposed to the seal at the bottom end of the outer tube. The first interface is connected to the natural gas pipeline and is equipped with a control valve for controlling the natural gas flow. The second interface is connected to the compressed air pipeline.

[0016] Furthermore, the urea pyrolysis device includes a combustion chamber with a cylindrical structure, a second burner is fixedly installed at the bottom end of the combustion chamber, one end of the second fire barrel of the second burner extends into the interior of the combustion chamber from the bottom end, and a urea solution injection port is provided on the cylinder wall of the combustion chamber and above the second fire barrel.

[0017] Furthermore, the ammonia injection mixing device includes a cylinder shell having an annular accommodating cavity, the cylinder shell is fixedly arranged on one side of the smoke outlet of the inner cylinder and is communicated with the inner cylinder;

[0018] Among them, an ammonia interface is provided on the outer ring wall of the cylinder shell, and the ammonia interface is connected to the urea pyrolysis device. A plurality of injection holes are provided on the inner ring wall of the cylinder shell, and the injection holes are used to evenly inject the ammonia temporarily stored in the annular accommodating cavity and enter the inner cylinder to mix with the heated flue gas.

[0019] Furthermore, the diameter of each of the injection holes is different, and they are arranged regularly with the diameter gradually decreasing near the ammonia interface and gradually increasing away from the ammonia interface, so that the ammonia temporarily stored in the annular accommodating cavity at the same time can enter the inner cylinder in equal amounts from different directions.

[0020] Furthermore, the SCR denitrification system also includes an ammonia flow regulating device, which is arranged at the connection between the urea pyrolysis device and the ammonia injection mixing device. The ammonia flow regulating device is a temperature control regulating device. According to the correlation between the nitrogen oxide concentration of the flue gas entering the inner cylinder and the urea solution injected into the combustion chamber on the ammonia outlet temperature, the ammonia flow entering the ammonia injection mixing device is regulated by the ammonia temperature.

[0021] Furthermore, the ammonia flow regulating device includes a conical air outlet provided at the ammonia outlet of the urea pyrolysis device, wherein one end of the conical air outlet close to the ammonia spray mixing device is closed and the other end is open;

[0022] The ammonia flow regulating device also includes a conical plug placed inside the conical air outlet, the taper of the conical plug is the same as the taper of the conical air outlet, and a temperature control driving mechanism for driving the conical plug to move horizontally is provided in the ammonia interface channel. The temperature control driving mechanism is used to control the conical plug to approach or move away from the conical air outlet to regulate the flow rate of ammonia entering the ammonia injection mixing device.

[0023] Furthermore, the temperature control drive mechanism includes a metal disc that is temperature-controlled and deformable and is fixed in the air inlet channel of the ammonia interface through a fixed bracket. A cross bar is horizontally fixed at the center of the metal disc. The cross bar can cause horizontal displacement through the temperature-controlled deformation of the metal disc. The end of the cross bar away from the metal disc is fixed to the conical plug. A sliding bracket is fixed in the air inlet channel of the ammonia interface for allowing the cross bar to pass through and supporting its horizontal sliding.

[0024] Furthermore, the SCR denitration system further includes a flue gas / air heat exchanger connected to the SCR denitration reactor. The flue gas after denitration and purification by the SCR denitration reactor enters the flue gas / air heat exchanger, and the purified high-temperature flue gas exchanges heat with the ambient air. After the heat exchange, the flue gas is discharged into the main flue through the induced draft fan, and the ambient air is heated and enters the heat storage body of the aluminum melting furnace through the combustion-supporting fan.

[0025] The SCR denitrification system also includes a control device, which is connected to a monitoring meter on the second pipeline for monitoring the flue gas temperature and nitrogen oxide concentration, a flue gas direct combustion heating device, a urea pyrolysis device, an SCR denitrification reactor, and an ammonia flow regulating device for coordinated control of the flue gas denitrification operation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The SCR denitrification system provided by this utility model mainly consists of an aluminum melting furnace, a heat storage body, a flue gas direct-fired heating device, a urea pyrolysis device, an ammonia spray mixing device, an ammonia flow control device, an SCR denitrification reactor, and a control device. Compared with existing technologies, it has at least the following advantages:

[0028] First, the denitrification efficiency is high. The thermal storage body stabilizes the temperature fluctuations of the flue gas generated by the aluminum melting furnace. The flue gas direct-fired heating device heats the flue gas that does not reach the set temperature, ensuring that the flue gas temperature entering the SCR denitrification reactor meets the catalyst's efficient reaction requirements (usually 230°C). Combined with the ammonia injection mixing device, ammonia and flue gas are fully mixed, thus achieving a high and stable denitrification efficiency.

[0029] The second is adaptive processing of flue gas with different nitrogen oxide concentrations. This is because in the process of treating flue gas, the amount of urea solution injected into the combustion chamber is generally regulated according to the nitrogen oxide concentration of the flue gas. Under the condition of a certain burner power, the change in the amount of urea solution will inevitably lead to a corresponding change in the ammonia outlet temperature (the more urea solution is injected, the lower the temperature, and vice versa). For this reason, the SCR denitrification system is equipped with an ammonia flow regulating device at the ammonia outlet to regulate the ammonia flow rate entering the ammonia injection mixing device according to the temperature. The ammonia and flue gas are fully and evenly mixed through specially designed injection holes, creating favorable conditions for the SCR denitrification reactor to efficiently treat flue gas, and can effectively deal with flue gas with high and fluctuating nitrogen oxide concentrations and different flow rates.

[0030] Third, it saves energy, reduces consumption, and saves space. The flue gas direct-fired heating unit, urea pyrolysis unit, ammonia injection and mixing unit, and ammonia flow control unit are integrated into a vertical, integrated design. This not only significantly saves plant space, but also significantly reduces heat loss between units, significantly improving energy efficiency. Furthermore, the SCR denitrification system recovers heat from the denitrified flue gas through a heat exchanger. This heat is then heated and passed through the combustion-supporting blower into the aluminum melting furnace's heat storage chamber. Field verification has demonstrated a heat recovery rate of up to 50%.

[0031] In addition, from a safety perspective, the SCR denitrification system avoids safety accidents such as explosions that may be caused by denitrification in the furnace, and at the same time improves the safety and reliability of the system by precisely controlling the reaction conditions.

[0032] In summary, the SCR denitrification system has the advantages of small footprint, low investment and operating costs. The control device coordinates the control of the flue gas denitrification operation, realizes the automatic operation of the system, and further improves the stability and reliability of the system. In addition, a flue gas / air heat exchanger is provided to achieve efficient energy recovery and utilization, effectively reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are incorporated into and constitute a part of this specification and, together with the description, are used to explain the principles of the present invention.

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1 This is a schematic diagram of the connection structure of the SCR denitrification system outside the high-efficiency and energy-saving aluminum melting furnace;

[0036] Figure 2 This is a schematic diagram of the integrated design structure of the four devices (flue gas direct combustion heating, urea pyrolysis, ammonia flow regulation, and ammonia injection mixing) in the SCR denitrification system of the utility model;

[0037] Figure 3 This utility model Figure 2 Schematic diagram of the main view structure;

[0038] Figure 4 This utility model Figure 2 A side view structural diagram of the invention;

[0039] Figure 5 This utility model Figure 3 AA cross-sectional structural diagram;

[0040] Figure 6 This utility model Figure 4 Schematic diagram of the cross-sectional structure of the middle BB;

[0041] Figure 7 This utility model Figure 6 Schematic diagram of the enlarged structure of part C in the middle.

[0042] in:

[0043] 1 is an aluminum melting furnace;

[0044] 2 is the heat storage body;

[0045] 3 is a flue gas direct-fired heating device; 31 is a cylinder; 32 is a first burner; 311 is an inner cylinder; 312 is an outer cylinder; 321 is a first fire cylinder; 322 is an air compression pump; 3121 is a flue gas interface; 3211 is a first interface; 3212 is a second interface;

[0046] 4 is a urea pyrolysis device; 41 is a combustion chamber; 42 is a second burner; 411 is a urea solution injection port; 421 is a second fire tube;

[0047] 5 is an ammonia spray mixing device; 51 is a cylinder shell; 511 is an outer ring wall; 512 is an inner ring wall; 5111 is an ammonia interface; 5121 is an injection hole;

[0048] 6 is an SCR denitrification reactor;

[0049] 7 is the first pipeline;

[0050] 8 is the second pipeline;

[0051] 9 is the third pipeline.

[0052] 10 is an ammonia flow regulating device; 101 is a conical air outlet; 102 is a conical plug; 103 is a temperature control drive mechanism; 1031 is a fixed bracket; 1032 is a metal disc; 1033 is a cross bar; 1034 is a sliding bracket. DETAILED DESCRIPTION

[0053] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of devices consistent with certain aspects of the present invention as detailed in the appended claims.

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0055] See also Figures 1 to 7 The embodiment of the present invention provides a high-efficiency and energy-saving SCR denitration system outside an aluminum melting furnace, which is mainly composed of an aluminum melting furnace 1, a heat storage body 2, a flue gas direct-fired heating device 3, a urea pyrolysis device 4, an ammonia injection mixing device 5, and an SCR denitration reactor 6. The gas outlet of the aluminum melting furnace 1 is connected to the gas inlet of the heat storage body 2 through a first pipeline 7, and the gas outlet of the heat storage body 2 is connected to the flue gas direct-fired heating device 3 through a second pipeline 8. The flue gas direct-fired heating device 3 heats the flue gas that has been treated by the heat storage body 2 and has not reached the set temperature, and mixes it with the ammonia generated by the pyrolysis of the urea pyrolysis device 4 at the ammonia injection mixing device 5 to form an ammonia / flue gas mixture. The gas outlet of the ammonia injection mixing device 5 is connected to the SCR denitration reactor 6 through a third pipeline 9. Under the action of the catalyst, ammonia and nitrogen oxides undergo an oxidation-reduction reaction to generate nitrogen and water. Through the above settings, it can be seen that even if the aluminum melting furnace 1 produces flue gas with large temperature fluctuations, it is treated by the heat storage body 2, which can make the high-temperature flue gas store heat and the low-temperature flue gas absorb heat, thereby stabilizing the original flue gas temperature. Then, the flue gas with a relatively low temperature enters the flue gas direct-fired heating device 3. At this time, if the flue gas temperature meets the set threshold temperature (generally set at 230°C), the flue gas direct-fired heating device 3 is not started. On the contrary, when the flue gas temperature is less than 230°C, the flue gas direct-fired heating device 3 is started to heat the low-temperature flue gas to 230°C; at the same time, according to the flow rate and concentration of the pretreated flue gas obtained by monitoring, ammonia is pyrolyzed in the urea pyrolysis device 4 to produce ammonia, and then the ammonia is allowed to enter the ammonia injection mixing device 5 and is fully mixed with the flue gas that has been heated to the set temperature to form an ammonia / flue gas mixture; finally, the mixed gas enters the SCR denitrification reactor 6. Under the action of the catalyst, ammonia and nitrogen oxides undergo an oxidation-reduction reaction to achieve efficient denitrification and generate nitrogen and water, thereby meeting the requirements of environmentally friendly emissions.

[0056] Preferably, the embodiment of the present invention is further provided with a heat exchanger and an induced draft fan, which is connected to the SCR denitration reactor 6. When the flue gas after denitration and purification by the SCR denitration reactor 6 enters the heat exchanger, the purified high-temperature flue gas transfers heat to the ambient air. The heated ambient air enters the heat storage body of the aluminum melting furnace through the combustion-supporting fan, realizing heat recovery and utilization. The purified flue gas after cooling is pressurized by the induced draft fan and enters the underground flue for collection. It is then connected to the original dust collector. After being processed by the dust collector, the flue gas is connected to the original main induced draft fan and finally discharged into the air through the chimney. Through this arrangement, heat recovery is effectively achieved and energy utilization efficiency is improved.

[0057] In the embodiment of the present utility model, Figure 2 As shown, the flue gas direct-fired heating device 3, urea pyrolysis device 4, and ammonia injection mixing device 5 adopt an integrated design. This design has many advantages: on the one hand, it can reduce heat loss between the devices, improve energy efficiency, and reduce operating costs. This is because the integrated design makes the connections between the devices closer, heat transfer more efficient, and reduces heat loss during the transmission process. On the other hand, it saves plant space. In actual production, plant space is often a limited resource. The integrated design can make the equipment layout more compact, saving valuable space resources for enterprises and facilitating production management and equipment maintenance.

[0058] Specifically, such as Figure 5 As shown, in the embodiment of the present utility model, the flue gas direct-fired heating device 3 includes a vertically arranged cylinder 31 and a first burner 32 located at the bottom of the cylinder 31. The cylinder 31 is composed of an inner cylinder 311 and an outer cylinder 312 which is sleeved on the outside and located at the lower part of the inner cylinder 311. The height of the inner cylinder 311 is greater than that of the outer cylinder 312, and the diameter is smaller than that of the outer cylinder 312. A flue gas interface 3121 connected to the second pipeline 8 is provided on the upper part of the outer cylinder 312. The top of the outer cylinder 312 is sealed and connected to the outer wall of the inner cylinder 311, and the bottom of the outer cylinder 312 is sealed. In this way, a sandwich channel is formed between the outer cylinder 312 and the inner cylinder 311. After the flue gas enters the sandwich channel from the flue gas interface 3121 on the upper part of the outer cylinder 312, it can only move downward along the sandwich channel until it reaches the bottom and then enters the inner cylinder 311. The first burner 32 is fixedly installed at the bottom seal of the outer tube 312. The first fire tube 321 of the first burner 32 passes through the bottom seal of the outer tube 312 and extends into the bottom of the inner tube 311. This design can first preheat the flue gas between the interlayer channel of the outer tube 312 and the inner tube 311, and then directly heat the flue gas entering the inner tube 311, thereby greatly improving the energy utilization rate.

[0059] Furthermore, the first flame tube 321 is provided with a first port 3211 and a second port 3212 spaced apart on one side of the first flame tube 321, which is exposed from the bottom seal of the outer tube 312. The first port 3211 is connected to the natural gas pipeline and is equipped with a control valve for controlling the natural gas flow. The second port 3212 is connected to the compressed air pipeline. Preferably, the compressed air is generated by an air compression pump 322, which uses mechanical principles to suck in and compress air at normal pressure.

[0060] The urea pyrolysis device 4 of the present embodiment includes a combustion chamber 41 having a cylindrical structure, with a second burner 42 fixedly mounted at the bottom end of the combustion chamber 41. Preferably, the structure of the second burner 42 is the same as that of the first burner 32. One end of a second flame barrel 421 of the second burner 42 extends from the bottom end of the combustion chamber 41 into the combustion chamber 41. A urea solution injection port 411 is provided on the wall of the combustion chamber 41, above the second flame barrel 421.

[0061] It should be noted that in the embodiment of the present invention, a monitoring meter for monitoring the flue gas temperature and nitrogen oxide concentration is installed on the second pipeline 8, near the side where the flue gas enters the direct-fired heating device 3, and the monitoring meter is linked to the urea solution spraying device through a control device (existing technology, which will not be repeated here). Specifically, when the nitrogen oxide concentration of the flue gas increases, the urea solution injected from the urea solution injection port 411 increases; conversely, when the nitrogen oxide concentration of the flue gas decreases, the urea solution injected decreases, thereby achieving the ability to treat flue gases with different nitrogen oxide concentrations. However, the above-mentioned control can only achieve coarse adjustment. According to the power rating of the second burner 42, the temperature of the ammonia generated by pyrolysis in the combustion chamber 41 will inevitably change accordingly. Therefore, in the embodiment of the utility model, a fine-tuning ammonia flow regulating device 10 is provided at the connection between the urea pyrolysis device 4 and the ammonia injection mixing device 5, and close to the side of the ammonia injection mixing device 5. The ammonia flow regulating device 10 is a temperature control regulating device, that is, the ammonia flow rate entering the ammonia injection mixing device 5 is further accurately regulated by comparing the ammonia temperature with the standard.

[0062] Specifically, such as Figure 6 、 7As shown, in an embodiment of the present utility model, the ammonia flow regulating device 10 includes a conical air outlet 101 arranged at the ammonia outlet of the urea pyrolysis device 4, and the conical air outlet 101 is closed at one end close to the ammonia injection mixing device 5, and the other end is open; it also includes a conical plug 102 placed inside the conical air outlet 101, and the taper of the conical plug 102 is the same as the taper of the conical air outlet 101. A temperature control driving mechanism 103 for driving the conical plug 102 to move horizontally is provided in the ammonia interface 5111 channel, and the temperature control driving mechanism 103 is used to control the conical plug 102 to approach or move away from the conical air outlet 101 to regulate the flow rate of ammonia entering the ammonia injection mixing device 5.

[0063] Furthermore, the temperature control drive mechanism 103 includes a temperature-controlled deformable metal disc 1032 fixed in the air inlet channel of the ammonia interface 5111 through a fixed bracket 1031. A cross bar 1033 is horizontally fixed at the center of the metal disc 1032. The cross bar 1033 can cause horizontal displacement through the temperature-controlled deformation of the metal disc 1032. The end of the cross bar 1033 away from the metal disc 1032 is fixed to the conical plug 102. A sliding bracket 1034 is fixed in the air inlet channel of the ammonia interface 5111 for allowing the cross bar 1033 to pass through and supporting its horizontal sliding. That is to say, when the nitrogen oxides in the flue gas increase, the amount of urea solution sprayed into the combustion chamber 41 will increase accordingly. At this time, the temperature of the ammonia in the combustion chamber 41 will be lower than normal, and the metal disc 1032 will shrink toward the side of the combustion chamber 41, thereby driving the cross bar 1033 and the sliding bracket 1034 to move horizontally toward the side of the combustion chamber 41, and simultaneously driving the conical plug 102 away from the conical air outlet 101, even if the ammonia outlet is slightly increased, thereby increasing the amount of ammonia entering the ammonia injection mixing device 5 to accurately match the nitrogen oxide concentration of the pretreated flue gas.

[0064] In this embodiment of the present invention, the ammonia spray mixing device 5 includes a shell 51 having an annular accommodating chamber. The shell 51 is fixedly mounted on one side of the flue gas outlet of the inner cylinder 311 and is in communication with the inner cylinder 311. An ammonia port 5111 is provided on the outer annular wall 511 of the shell 51, which is connected to the urea pyrolysis device 4. A plurality of injection holes 5121 are provided on the inner annular wall 512 of the shell 51. These injection holes 5121 are used to uniformly spray the ammonia temporarily stored in the annular accommodating chamber and allow it to enter the inner cylinder 311 and mix with the heated flue gas.

[0065] Furthermore, the diameters of the injection holes 5121 are different, and their arrangement is as follows: the diameters of the injection holes closer to the ammonia port 5111 gradually decrease, while the diameters of the injection holes farther from the ammonia port 5111 gradually increase. This design ensures that ammonia temporarily stored in the annular accommodation chamber enters the inner cylinder 311 from different directions in equal amounts at the same time, thereby ensuring thorough and even mixing of the ammonia and flue gas.

[0066] In addition, an embodiment of the present invention also includes a control device, which is connected to a monitoring meter on the second pipeline 8 for monitoring the flue gas temperature and nitrogen oxide concentration, a flue gas direct-fired heating device 3, a urea pyrolysis device 4, an SCR denitrification reactor 6, and an ammonia flow regulating device 10. Its main function is to coordinate the control of the flue gas denitrification operation, especially for the large fluctuations in the flue gas temperature and nitrogen oxide concentration of the aluminum melting furnace, and can achieve precise control to ensure stable and efficient operation of the entire denitrification system.

[0067] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0068] It should be understood that the present invention is not limited to the above description and that various modifications and changes can be made without departing from the scope of the present invention. The scope of the present invention is limited only by the appended claims.

Claims

1. A high-efficiency and energy-saving SCR denitrification system outside an aluminum melting furnace, characterized in that: It comprises an aluminum melting furnace (1), a heat storage body (2), a flue gas direct combustion heating device (3), a urea pyrolysis device (4), an ammonia injection mixing device (5), and an SCR denitration reactor (6); The air outlet of the aluminum melting furnace (1) is connected to the air inlet of the heat storage body (2) through a first pipeline (7) to stabilize the temperature fluctuation of the flue gas generated by the aluminum melting furnace (1). The air outlet of the heat storage body (2) is connected to the flue gas direct-fired heating device (3) through a second pipeline (8). The flue gas direct-fired heating device (3) heats the flue gas that has been treated by the heat storage body (2) and has not reached the set temperature, and mixes it with the ammonia generated by the pyrolysis of the urea pyrolysis device (4) at the ammonia spray mixing device (5) to form an ammonia / flue gas mixture. The air outlet of the ammonia spray mixing device (5) is connected to the SCR denitration reactor (6) through a third pipeline (9). Under the action of the catalyst, the ammonia and the nitrogen oxides undergo an oxidation-reduction reaction to generate nitrogen and water. The flue gas direct combustion heating device (3), the urea pyrolysis device (4) and the ammonia injection mixing device (5) adopt an integrated design.

2. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 1 is characterized in that: The flue gas direct combustion heating device (3) comprises a vertically arranged cylinder (31) and a first burner (32); The cylinder (31) is composed of an inner cylinder (311) and an outer cylinder (312) sleeved on the outer portion of the inner cylinder (311) and located at the lower portion of the inner cylinder (311). A flue gas interface (3121) connected to a second pipeline (8) is provided on the upper portion of the outer cylinder (312). A monitoring meter for monitoring flue gas temperature and nitrogen oxide concentration is installed on the second pipeline (8). The top end of the outer cylinder (312) is sealed and connected to the outer wall of the inner cylinder (311), and the bottom end of the outer cylinder (312) is sealed. The first burner (32) is fixedly mounted at the bottom seal of the outer cylinder (312). The first fire tube (321) of the first burner (32) passes through the bottom seal of the outer cylinder (312) and extends into the bottom of the inner cylinder (311), and is used to preheat the flue gas between the outer cylinder (312) and the inner cylinder (311), and to heat the flue gas entering the inner cylinder (311).

3. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 2 is characterized in that: The first fire tube (321) is provided with a first interface (3211) and a second interface (3212) at a distance from one side of the first fire tube (321) which is exposed to the bottom seal of the outer tube (312). The first interface (3211) is connected to a natural gas pipeline and is equipped with a control valve for controlling the flow of natural gas. The second interface (3212) is connected to a compressed air pipeline.

4. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 2 is characterized in that: The urea pyrolysis device (4) comprises a combustion chamber (41) with a cylindrical structure, a second burner (42) is fixedly installed at the bottom end of the combustion chamber (41), one end of a second fire tube (421) of the second burner (42) extends from the bottom end of the combustion chamber (41) into the interior thereof, and a urea solution injection port (411) is provided on the cylinder wall of the combustion chamber (41) and above the second fire tube (421).

5. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 2 is characterized in that: The ammonia spray mixing device (5) comprises a cylinder shell (51) having an annular accommodating cavity, wherein the cylinder shell (51) is fixedly arranged on one side of the smoke outlet of the inner cylinder (311) and is in communication with the inner cylinder (311); The outer ring wall (511) of the cylinder shell (51) is provided with an ammonia interface (5111), and the ammonia interface (5111) is connected to the urea pyrolysis device (4). The inner ring wall (512) of the cylinder shell (51) is provided with a plurality of injection holes (5121), and the injection holes (5121) are used to uniformly inject the ammonia temporarily stored in the annular accommodating cavity and enter the inner cylinder (311) to mix with the heated flue gas.

6. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 5 is characterized in that: The diameter of each of the injection holes (5121) is different, and they are arranged regularly with the diameter gradually decreasing as they approach the ammonia interface (5111) and gradually increasing as they move away from the ammonia interface (5111), so as to allow equal amounts of ammonia temporarily stored in the annular accommodating cavity to enter the inner cylinder (311) from different directions at the same time.

7. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 5 is characterized in that: The SCR denitration system further comprises an ammonia flow regulating device (10), which is arranged at the connection between the urea pyrolysis device (4) and the ammonia spray mixing device (5). The ammonia flow regulating device (10) is a temperature control regulating device, which regulates the flow of ammonia entering the ammonia spray mixing device (5) by adjusting the temperature of the ammonia according to the correlation between the nitrogen oxide concentration of the flue gas entering the inner cylinder (311) and the urea solution sprayed into the combustion chamber (41) on the ammonia outlet temperature.

8. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 7 is characterized in that: The ammonia flow regulating device (10) comprises a conical gas outlet (101) provided at the ammonia outlet of the urea pyrolysis device (4), wherein one end of the conical gas outlet (101) close to the ammonia spray mixing device (5) is closed, and the other end is open; The ammonia flow regulating device (10) further comprises a conical plug (102) disposed inside the conical air outlet (101), wherein the taper of the conical plug (102) is the same as the taper of the conical air outlet (101), and a temperature control driving mechanism (103) for driving the conical plug (102) to move horizontally is provided in the channel of the ammonia interface (5111), wherein the temperature control driving mechanism (103) is used to control the conical plug (102) to move closer to or further away from the conical air outlet (101) to regulate the flow rate of ammonia entering the ammonia injection mixing device (5).

9. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to claim 8 is characterized in that: The temperature control drive mechanism (103) comprises a metal disc (1032) which is temperature-controlled and deformable and is fixed in the air inlet channel of the ammonia interface (5111) via a fixed bracket (1031); a cross bar (1033) is fixed horizontally at the center of the metal disc (1032); the cross bar (1033) can cause horizontal displacement through the temperature-controlled deformation of the metal disc (1032); one end of the cross bar (1033) away from the metal disc (1032) is fixedly connected to the conical plug (102); and a sliding bracket (1034) is fixed in the air inlet channel of the ammonia interface (5111) for allowing the cross bar (1033) to pass through and supporting its horizontal sliding.

10. The high-efficiency and energy-saving SCR denitrification system outside the aluminum melting furnace according to any one of claims 7 to 9, characterized in that: The SCR denitration system further comprises a flue gas / air heat exchanger connected to the SCR denitration reactor (6); the flue gas purified by denitration in the SCR denitration reactor (6) enters the flue gas / air heat exchanger; the purified high-temperature flue gas exchanges heat with ambient air; after the heat exchange, the flue gas is discharged into the main flue through the induced draft fan; and the ambient air is heated and enters the heat storage body of the aluminum melting furnace through the combustion-supporting fan.

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