Double-nozzle type dispersion burner and using method

Abstract

The double-nozzle type dispersion burner comprises a gas pipe, a flue gas spray pipe and an air spray pipe, the gas pipe penetrates through the flue gas cavity and extends into the flue gas throat pipe, the flue gas spray pipe penetrates through the air cavity and extends into the air throat pipe, and the central axis of the air discharge channel, the central axis of the flue gas discharge channel, the central axis of the flue gas throat pipe and the central axis of the gas pipe are collinear. Smoke of 10 kPaG or above enters the smoke cavity, fuel gas of 10 kPaG to 20 kPaG enters the fuel gas pipe, air of 800 DEG C or above enters the air cavity, the air jet flow core comprises smoke jet flow cores, the smoke jet flow cores comprise fuel gas jet flow cores, initial sections of smoke jet flow and air jet flow are equal, and smoke standard state flow is 1-2.33 times of fuel gas standard state flow. The method can be applied to waste aluminum ingot melting and casting, aluminum alloy refining devices and the like in the nonferrous metallurgy field. The method can quickly melt and cast aluminum materials, combustion is complete, the overall furnace temperature level is high, furnace temperature distribution is uniform, and NOx emission is smaller than or equal to 50 mg / m < 3 >.

Description

Technical Field

[0001] The invention relates to a dual-nozzle type dispersion burner that uses an air nozzle and a flue gas nozzle, where a medium-low pressure flue gas jet separates the gas jet and the air jet, carrying the gas jet rapidly through the core area of ​​the air jet. After diluting the gas, the gas enters the main section of the air jet, where low-oxygen dispersion combustion is organized. It is suitable for use in industrial furnaces such as smelting furnaces, aluminum melting furnaces, melting furnaces, casting furnaces, heating furnaces, holding furnaces, aging furnaces, quenching furnaces, homogenizing furnaces, annealing furnaces, tempering furnaces, and heat treatment furnaces, as well as industrial furnaces such as ceramic furnaces (building ceramics, household ceramics, etc.), melting furnaces (glass furnaces, refractory materials, etc.), chemical pyrolysis furnaces, decomposition furnaces, and drying furnaces. Background Technology

[0002] Based on China's 2016 aluminum production of 57.96 million tons and aluminum alloy production of 7 million tons, totaling 64 million tons, it is estimated that there were 10,000 aluminum melting furnaces. Aluminum melting furnaces are the main energy-consuming equipment in aluminum processing enterprises, accounting for a large proportion of production energy consumption.

[0003] Currently, domestic aluminum processing enterprises generally use premixed regenerative combustion energy-saving technology in aluminum melting furnaces, which features energy saving, rapid melting, and high NO content. x Characteristics such as emissions. The premixed regenerative combustion aluminum melting furnace uses paired regenerative burners, increasing the combustion air inlet temperature to 800–1000℃ and reducing the exhaust gas temperature to below 180℃, resulting in natural gas consumption per unit product as low as 53–61 m³. 3 / t. Additionally, the high-temperature flame continuously washes over the heated surfaces, giving the aluminum melting furnace a rapid melting characteristic. However, because the oxygen concentration in the combustion zone remains constant at 21%, the combustion flame is small and bright, resulting in high NO content in the flue gas. x Emissions can reach 500–2000 mg / m³ 3 The NO levels far exceed the "Emission Standard of Air Pollutants for Industrial Furnaces and Kilns" (GB9078-1996), the "Emission Standard of Pollutants for Recycled Copper, Aluminum, Lead and Zinc Industries" (GB31574-2015), or the acceptance requirements of local environmental protection management departments. x Emissions 50mg / m³ 3 There are reports on the research and development of low-NOx combustion technology by domestic aluminum processing companies, which includes energy-saving and low-NOx technologies. x While emission test data was presented, the issue of slow melting was overlooked. It is precisely this slow melting defect that limits the widespread application of low-NOx aluminum melting furnaces. Currently, the application of low-NOx combustion technology in aluminum processing enterprises is limited to the aluminum melting and holding stage or the holding furnace, failing to meet the requirements of "energy saving, rapid melting, and extremely low NOx." x Reports on low-nitrogen aluminum melting technology that meets melting and casting requirements such as "emissions" are extremely rare.

[0004] While maintaining the energy-saving advantages of premixed regenerative combustion aluminum melting furnaces, we will develop ultra-low NO₂ levels in flue gas to meet the needs of melting and casting.x emissions (≤50mg / m 3 ) and fast melting of the double nozzle type diffusion burner, can promote the green and clean production requirements of aluminum ingot waste aluminum melting and casting processing industry, reduce the flue gas NO x emission intensity, total amount of reduction and environmental protection cost, and further promote the sustainable development of aluminum processing industry. SUMMARY

[0005] In view of the problems of premix regenerative combustion aluminum melting furnace, such as peak combustion temperature, high concentration of flue gas NO x emission, etc., a double nozzle type diffusion burner is designed, which uses a flue gas nozzle and an air nozzle, a low pressure flue gas jet separates the gas jet and the air jet, and carries the gas jet to quickly pass through the core area of the air jet, dilutes the gas, and then enters the main section of the air jet, and organizes low oxygen diffusion combustion in this area.

[0006] The double nozzle type diffusion burner includes a gas pipe, a flue gas nozzle and an air nozzle, the air nozzle includes an air cavity and an air throat pipe, the air cavity includes a tapered conical frustum cylindrical air exhaust passage, the flue gas nozzle includes a flue gas cavity and a flue gas throat pipe, the flue gas cavity includes a tapered conical frustum cylindrical flue gas exhaust passage, the gas pipe extends into the flue gas throat pipe through the flue gas cavity, the flue gas nozzle extends into the air throat pipe through the air cavity, the air exhaust passage, the air throat pipe, the flue gas exhaust passage, the flue gas throat pipe and the central axis of the gas pipe are collinear, the outlet end face of the gas pipe, the outlet end face of the flue gas throat pipe, the outlet end face of the air throat pipe and the inner wall surface of the furnace wall are coplanar, the outer wall surface of the furnace wall, the inlet end face of the air throat pipe and the inlet end face of the flue gas throat pipe are coplanar, the small end face of the flue gas exhaust passage, the small end face of the air exhaust passage and the outer wall surface of the furnace wall are coplanar, the large end faces of the air exhaust passage and the flue gas exhaust passage are coplanar, the air throat pipe is embedded in the air inlet hole of the furnace wall, and the small end face of the air exhaust passage and the outer wall surface of the furnace wall are flange connected.

[0007] When the double nozzle type diffusion burner is used, 10kPaG and above flue gas enters the flue gas cavity, 10kPaG-20kPaG gas enters the gas pipe, 800℃ and above air enters the air cavity, the air jet core of the air nozzle contains the flue gas jet core of the flue gas nozzle, the flue gas jet core contains the gas jet core of the gas pipe, the initial section of the flue gas jet and the air jet is equal, the flue gas jet core contains the gas jet core, the flue gas standard state flow is 1-2.33 times the gas standard state flow, when the burner is installed obliquely downward, the angle between the central axis of the air jet and the ground surface is maintained in the range of 6°-20°, the turning point of the air jet intersects the top surface of the aluminum liquid, and the length of the initial section of the air jet is 0.45-0.75 times the length of the aluminum liquid line where the aluminum liquid surface projection is located.

[0008] The non-ferrous metallurgical smelting field waste aluminum melting, aluminum ingot melting and casting and aluminum alloy refining device, automobile hub company, aluminum company, automobile aluminum product production, aluminum alloy manufacturing company, motorcycle hub company, non-ferrous metal smelting and other units of smelting furnace, aluminum melting furnace, melting furnace, melting furnace, heating furnace, holding furnace, aging furnace, quenching furnace, homogenizing furnace, annealing furnace, tempering furnace, hot heat treatment furnace and other industrial furnaces, ceramic furnaces (building ceramics, household ceramics, etc.), melting furnaces (glass furnaces, refractory materials, etc.), chemical cracking furnaces, decomposition furnaces, drying furnaces and other industrial furnaces can use the present application.

[0009] The application can low-nitrogen melting and casting, rapid melting and casting and energy-saving melting and casting, and can safely and stably melt and cast. The application has low air consumption coefficient, complete combustion, low carbon monoxide emission concentration of flue gas, high utilization rate of fuel gas, high overall level of furnace temperature, good uniformity of furnace temperature, fast melting and casting rate, less oxidation loss, high efficiency and energy saving, the exhaust gas temperature reaches the access level (≤180 DEG C) of "Iron and Steel Industry Regenerative Combustion Technology Standard" (YB / T4209-2020), and the flue gas nitrogen oxide emission concentration reaches the special emission limit value of 50mg / m 3 The level, promotes the green upgrading and clean production of waste aluminum melting and casting, aluminum ingot melting and casting and aluminum alloy refining enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 And Figure 2 It is respectively the vertical section view and airflow organization diagram of double-nozzle type dispersion burner.

[0011] Figure 1 And Figure 2In the figure, 1 is a gas pipe, 2 is a flue gas nozzle, 21 is a flue gas cavity, 211 is a flue gas discharge channel, 22 is a flue gas throat pipe, 3 is an air nozzle, 31 is an air cavity, 311 is an air discharge channel, 32 is an air throat pipe, 4, 5, 6, 7 and 8 are positioning rings; A is gas, B is molten aluminum low-temperature flue gas, C is high-temperature air, D, E and F are air jet flow, flue gas jet flow and gas jet flow pole point (intersection of jet boundary layer outer boundary reverse extension line and central axis), L and G are upper and lower vertices of high-temperature air nozzle exit surface, K and H are upper and lower vertices of flue gas nozzle exit surface, J and I are upper and lower vertices of gas nozzle exit, M and N are upper and lower intersection points of flue gas jet flow boundary layer outer boundary and flue gas jet flow boundary layer inner boundary, M' and N' are upper and lower intersection points of flue gas jet flow boundary layer outer boundary and air jet flow boundary layer inner boundary, M" and N" are upper and lower intersection points of air jet flow boundary layer inner boundary and gas jet flow boundary layer outer boundary, Q and V are upper and lower intersection points of air jet flow boundary layer outer boundary and turning line (connecting line of position point where air speed decays to 0), R and U are upper and lower intersection points of flue gas jet flow boundary layer outer boundary and turning line (connecting line of position point where flue gas speed decays to 0), S and T are upper and lower intersection points of flue gas jet flow boundary layer outer boundary and flue gas jet flow turning line, W, X and Y are outer boundary points of air jet flow, flue gas jet flow and gas jet flow central axis direction, P is a gas jet flow turning point (position point where gas speed decays to 0), O is an air jet flow turning point (position point where air speed decays to 0), which is also a flue gas jet flow turning point (position point where flue gas speed decays to 0). DETAILED DESCRIPTION

[0012] The application will be further described below with reference to the accompanying drawings.

[0013] As Figure 1As shown, the double-nozzle type diffusion burner includes a gas tube 1, a flue gas nozzle 2, an air nozzle 3, a positioning ring 4, a positioning ring 5, a positioning ring 6, a positioning ring 7 and a positioning ring 8. The air nozzle 3 includes an air cavity 31 and an air throat 32, and the air cavity 31 includes a tapered conical frustum cylindrical air discharge passage 311. The flue gas nozzle 2 includes a flue gas cavity 21 and a flue gas throat 22, and the flue gas cavity 21 includes a tapered conical frustum cylindrical flue gas discharge passage 211. The gas tube 1 extends into the flue gas throat 22 through the flue gas cavity 21, and the flue gas nozzle 2 extends into the air throat 32 through the air cavity 31. The center axes of the air discharge passage 311, the air throat 32, the flue gas discharge passage 211, the flue gas throat 22 and the gas tube 1 are collinear. The outlet end face of the gas tube 1, the outlet end face of the flue gas throat 22, the outlet end face of the air throat 32 and the inner wall face of the furnace wall are coplanar, the outer wall face of the furnace wall, the inlet end face of the air throat 32 and the inlet end face of the flue gas throat 22 are coplanar, the small end face of the flue gas discharge passage 22, the small end face of the air discharge passage 311 and the outer wall face of the furnace wall are coplanar, and the large end faces of the air discharge passage 311 and the flue gas discharge passage 211 are coplanar. The air throat 32 is embedded in the air inlet hole of the furnace wall, and the small end face of the air discharge passage 311 and the outer wall face of the furnace wall are flange-connected.

[0014] The gas tube 1 extends into the flue gas cavity 21, and the positioning ring 4 fixes the middle end of the gas tube 1 in the flue gas discharge passage 211. The flue gas cavity 21 extends into the air cavity 31, and the positioning ring 5 fixes the flue gas discharge passage 211 in the air discharge passage 311. The large end faces of the flue gas discharge passage 211 and the air discharge passage 311 are coplanar, the small end face of the air discharge passage 311, the small end face of the flue gas discharge passage 211 and the outer wall face of the furnace wall are coplanar, and the inlet end face of the air throat 32, the inlet end face of the flue gas throat 22 and the outer wall face of the furnace wall are coplanar. The flue gas throat 22 is fixed in the air throat 32, the positioning ring 6 fixes the inlet end of the flue gas throat 22 in the inlet end of the air throat 32, the positioning ring 7 fixes the middle end of the gas tube 1 in the inlet end of the flue gas throat 22, the positioning ring 8 fixes the outlet end of the gas tube 1 in the outlet end of the flue gas throat 22, and the positioning ring 9 fixes the outlet end of the flue gas throat 22 in the outlet end of the air throat 32. The length of the flue gas throat 22 is shorter than the thickness of the furnace wall, and the outlet end of the flue gas throat 22 is in the air inlet hole of the furnace wall. The center axes of the flue gas discharge passage 211 and the flue gas throat 22, the air discharge passage 311 and the air throat 32, and the gas tube 1 are collinear. The air throat 32 is embedded in the air inlet hole of the furnace wall, and the small end face of the air discharge passage 311 and the outer wall face of the furnace wall are flange-connected. The air throat 32 contains the flue gas throat 22, the flue gas throat 22 contains the rear half of the gas tube 1, the air throat 32, the flue gas throat 22 and the rear half of the gas tube 1 are of an integrated structure, the front half of the gas tube 1 extends through the flue gas cavity 21, the flue gas cavity 21 extends through the air cavity 31, and the air cavity 31, the flue gas cavity 21 and the front half of the gas tube 1 are of an integrated structure.

[0015] The inner wall surface of the air discharge passage 311 of the air nozzle 3 and the inner wall surface of the air throat 32 are smooth, reducing the resistance loss during the high-temperature air flowing from the air discharge passage 311 into the air throat 32. The inner wall surface of the flue gas discharge passage 211 of the flue gas nozzle 2 and the inner wall surface of the inlet section of the flue gas throat 22 are smooth, reducing the resistance loss during the flue gas flowing from the flue gas discharge passage 22 into the flue gas throat 22.

[0016] There is no leakage of air between the connection of the flue gas discharge passage 211 and the flue gas throat 22, and there is no leakage of air between the connection of the air discharge passage 311 and the air throat 32.

[0017] The outer shell of the air cavity 31 of the air nozzle 3 is made of stainless steel 20g, and is lined with refractory castable. The air throat 32 is a refractory cast pipe, and the lining of the air cavity 31 and the air throat 32 can withstand a temperature of 1200℃ or above for a long time. The flue gas injector 2 can withstand a temperature of 1200℃ or above for a long time, and is made of high-temperature alloy steel 309S, high-temperature alloy steel 310S, or corundum.

[0018] The positioning rings 4, 5, 6, 7, 8, and 9 are evenly provided with a plurality of ventilation holes. The airflow flowing through the ventilation holes has small resistance loss, which can be ignored. The positioning ring 4 is evenly provided with a plurality of ventilation holes, without hindering the flow of flue gas in the flue gas discharge passage 211. The gas pipe 1 passes through the center hole of the positioning ring 4, and the outer circumference of the positioning ring 4 tightly contacts the inner wall surface of the flue gas discharge passage 211. The positioning ring 5 does not hinder the flow of high-temperature air out of the air discharge passage 311. The high-temperature air leaving the outlet of the air discharge passage 311 passes through the center hole of the positioning ring 5, and the outer circumference of the positioning ring 5 tightly contacts the inner wall surface of the air discharge passage 311. The positioning ring 5 and the positioning ring 6 do not hinder the flow of high-temperature air into the air throat 32. The inlet of the flue gas throat 22 passes through the center hole of the positioning ring 6, and the outer circumference of the positioning ring 6 tightly contacts the inner wall surface of the inlet of the air throat 32. The positioning ring 7 does not hinder the flow of flue gas out of the flue gas throat 22. The outlet of the flue gas pipe 1 passes through the center hole of the positioning ring 8, and the outer circumference of the positioning ring 8 tightly contacts the inner wall surface of the outlet of the flue gas throat 22. The outlet of the flue gas throat 22 passes through the center hole of the positioning ring 9, and the outer circumference of the positioning ring 9 tightly contacts the inner wall surface of the outlet of the air throat 32. The positioning ring 4, the positioning ring 5, the positioning ring 6, the positioning ring 7, the positioning ring 8, and the positioning ring 9 are evenly provided with a plurality of ventilation holes, can withstand a temperature of 1200℃ or above for a long time, and are made of high-temperature alloy steel 309S, high-temperature alloy steel 310S, or corundum.

[0019] When the double-nozzle type diffusion burner is used, 10 kPaG and above flue gas enters the flue gas chamber, 10 kPaG-20 kPaG fuel gas enters the fuel gas pipe, 800℃ and above air enters the air chamber, the air jet stream nucleus of the air jet stream of the air nozzle contains the flue gas jet stream nucleus of the flue gas nozzle, and the flue gas jet stream nucleus contains the fuel gas jet stream nucleus of the fuel gas pipe 1. The initial section of the flue gas jet stream is equal to that of the air jet stream, the flue gas jet stream nucleus contains the fuel gas jet stream nucleus, and the flue gas standard state flow rate is 1-2.33 times the fuel gas standard state flow rate.

[0020] The flue gas nozzle, the air nozzle and the fuel gas pipe are used to form the flue gas jet stream, the air jet stream and the fuel gas jet stream. The flue gas jet stream has three functions: the low-temperature flue gas jet stream separates the fuel gas jet stream and the air jet stream, carries the fuel gas jet stream to quickly pass through the core area of the air jet stream, dilutes the fuel gas and enters the main section area of the air jet stream, and establishes the low fuel gas molecular concentration condition required for low-oxygen diffusion combustion in this area.

[0021] The flue gas in the flue gas chamber 21 comes from the low-temperature (150℃-250℃) exhaust gas of the aluminum melting furnace. The flue gas is taken from the exhaust pipe of the aluminum melting furnace, pressurized to 10 kPaG-100 kPaG by a Roots blower or pressurized to 0.1 MPaG and above by an air compressor, and then sent to the flue gas chamber 21.

[0022] After the air (800℃ and above) enters the air chamber 31, it flows through the air nozzle 32 and is quickly sprayed out to form a ring-shaped air jet stream. After the flue gas (10 kPaG and above) enters the flue gas chamber 21, it flows through the flue gas nozzle 22 and is sprayed out at high speed to form a ring-shaped flue gas jet stream. The fuel gas (10 kPaG-20 kPaG) flows through the fuel gas pipe 1 to form a conical fuel gas jet stream. The air jet stream contains the flue gas jet stream, the turning point of the central axis of the flue gas jet stream and the air jet stream (the intersection of the central axis and the initial section change to the turning surface of the main section, and the speed of the flue gas and the air is 0), the vertex of the flue gas jet stream nucleus and the air jet stream nucleus coincide, the initial section length of the flue gas jet stream and the air jet stream is equal, the flue gas jet stream contains the fuel gas jet stream, and the initial section length of the flue gas jet stream is longer than that of the fuel gas jet stream. The flue gas standard state flow rate is 1-2.33 times the fuel gas standard state flow rate, and the fuel gas volume concentration of the fuel gas and flue gas mixed gas stream entering the main section area of the air jet stream decreases from 100% of the fuel gas pipe 1 to 30%-50%. According to the low calorific value of the fuel gas 8500 kCal / m 3 It is estimated that the low calorific value of the fuel gas and flue gas mixed gas stream decreases to 2550 kCal / m 3 -4250 kCal / m 3 .

[0023] There is an air jet flow behind the outlet of air throat pipe 32, a flue gas jet flow behind the outlet of flue gas throat pipe 22, and a fuel gas jet flow behind the outlet of fuel gas pipe. According to jet boundary layer theory, a free jet has a jet core zone and a jet boundary layer phenomenon. The central part of the jet is not affected by mixing and still maintains the original outlet velocity, which is called the jet core zone. The jet section between the outlet of the pipe and the end section of the core zone (the spatial curved surface formed by connecting the points where the air flow velocity decays to 0) is called the initial section of the jet. The jet boundary layer continuously spreads outward from the outlet of the pipe along the range, bringing the surrounding medium into the boundary layer and expanding to the jet axis at a certain distance. The core zone disappears, and this section of the jet is called the turning surface (the spatial curved surface formed by connecting the points where the air flow velocity decays to 0). When the outlet turbulence intensity is low, the initial section length is about 6.2 times the outlet inner diameter of the pipe. Figure 2 In the figure, D, E, F are the extreme points of the air jet flow, flue gas jet flow and fuel gas jet flow respectively, L, G are the upper and lower vertices of the high-temperature air injection outlet surface respectively, K, H are the upper and lower vertices of the flue gas injection outlet surface respectively, J, I are the upper and lower vertices of the fuel gas injection outlet respectively, M, N are the upper and lower intersection points of the outer boundary of the flue gas jet flow boundary layer and the inner boundary of the flue gas jet flow boundary layer, the upper and lower intersection points of the turning surface, M, N are the upper and lower intersection points of the outer boundary of the flue gas jet flow boundary layer and the turning surface, Q, V are the upper and lower intersection points of the outer boundary of the air jet flow boundary layer and the turning line, R, U are the upper and lower intersection points of the outer boundary of the flue gas jet flow boundary layer and the turning line, S, T are the upper and lower intersection points of the outer boundary of the fuel gas jet flow boundary layer and the turning line of the flue gas jet flow, W, X, Y are the outer boundary points in the direction of the central axis of the air jet flow, flue gas jet flow and fuel gas jet flow respectively, P is the turning point of the fuel gas jet flow, and O is the turning point of the air jet flow, which is also the turning point of the flue gas jet flow. Increase the flue gas pressure or flow rate to extend the initial section length of the flue gas jet flow to the same degree as the initial section length of the air jet flow, i.e. the bottom surface of the flue gas jet flow core zone corresponding to the outlet of the flue gas injection pipe 2 coincides with the bottom surface of the air jet flow core zone corresponding to the outlet of the air injection pipe 1.

[0024] Figure 2In the figure, ΔLOG is the core area of the air jet, LQ, VG are the upper and lower boundaries of the outer boundary layer of the air jet, LO, GO are the upper and lower boundaries of the inner boundary layer of the air jet. ΔKOH is the core area of the flue gas jet, KR, HU are the upper and lower boundaries of the outer boundary layer of the flue gas jet, KO, HO are the upper and lower boundaries of the inner boundary layer of the flue gas jet. ΔJPI is the core area of the fuel gas jet, JS, IT are the upper and lower boundaries of the outer boundary layer of the fuel gas jet, JP, IP are the upper and lower boundaries of the inner boundary layer of the fuel gas jet. M is the intersection of the upper outer boundary JS of the fuel gas jet boundary layer and the upper inner boundary KO of the flue gas jet boundary layer, N is the intersection of the lower outer boundary IT of the fuel gas jet boundary layer and the lower inner boundary HO of the flue gas jet boundary layer. M' is the intersection of the upper inner boundary LO of the air jet boundary layer and the upper outer boundary KR of the flue gas jet boundary layer, N' is the intersection of the lower inner boundary GO of the air jet boundary layer and the lower outer boundary HU of the flue gas jet boundary layer. M" is the intersection of the upper inner boundary LO of the air jet boundary layer and the upper outer boundary JS of the fuel gas jet boundary layer, N" is the intersection of the lower inner boundary GO of the air jet boundary layer and the lower outer boundary IT of the fuel gas jet boundary layer. QWV is the outer boundary of the air jet center axis direction, RXU is the outer boundary of the flue gas jet center axis direction, SYT is the outer boundary of the center axis direction after the fuel gas jet mixes into the flue gas jet. According to the jet boundary layer theory, the area outside the boundary LQWVG has neither oxygen molecules nor fuel gas molecules, which is a non-reaction zone. ΔLM'K, ΔGN'H are high-temperature air zones, which are non-reaction zones. The area LM'RXUN'GVWQL has low-concentration oxygen molecules (oxygen is diluted based on 21%, and oxygen molecules account for no more than 5%-10% in the total oxygen supply) but no fuel gas molecules, which is a non-reaction zone. The area KRXUHNTYSMK has low-concentration (flue gas is diluted based on the concentration in the flue gas chamber) flue gas conditions, but no fuel gas concentration conditions, which is a non-reaction zone. The area M"SYTN"OM" has low fuel flue gas concentration (fuel flue gas is further diluted after mixing) conditions and low oxygen concentration (oxygen is diluted based on 21%) conditions, and can occur low-oxygen dispersion combustion. The area MM"OM and the area NN"ON have high-oxygen concentration (oxygen 21%) conditions and low fuel flue gas concentration (fuel flue gas is further diluted by the flue gas in the furnace) conditions, but the oxygen molecules are not diluted, and whether low-oxygen dispersion combustion can occur depends on the degree of flue gas dilution of fuel gas. When the flue gas accounts for a small proportion in the fuel flue gas mixed gas flow, high-temperature air combustion may still occur. The boundary KOHK encloses an area with high flue gas concentration conditions, but no oxygen concentration conditions, which is a non-reaction zone. The boundary JPIJ encloses an area with high fuel gas concentration conditions, but no oxygen concentration conditions, which is a non-reaction zone. The boundary M"SYTN"OM" realizes low-oxygen dispersion combustion, and requires that the fuel gas entering the main section of the air jet be diluted by the flue gas jet to a fuel gas volume concentration of 30%-50%, at which time the flue gas standard state flow is 1-2.33 times the fuel gas standard state flow. According to the low heat value of fuel gas 8500kCal / m 3The low heat value of the mixed gas stream of the combustion fume is estimated to be reduced to 2550 kCal / m 3 ~ 4250 kCal / m 3 .

[0025] As shown in Figure 1 , the double-nozzle type dispersion burner can be used horizontally, in which case the central axis of the burner is parallel to the ground and perpendicular to the outer wall of the furnace. The burner can also be used obliquely, in which case the central axis of the air jet is maintained at an angle of 6°~20° to the ground, the turning point of the air jet intersects the top surface of the molten aluminum, and the length of the initial section of the air jet is 0.45~0.75 times the length of the projection of the molten aluminum surface on the aluminum line (the intersection line of the vertical plane passing through the central axis of the air jet and the top surface of the molten aluminum).

[0026] The structural features, technical features and resulting technical effects of the invention are described in detail as follows:

[0027] The invention includes a gas tube, a flue gas nozzle and an air nozzle, the gas tube extends into the flue gas throat through the flue gas cavity, the flue gas nozzle extends into the air throat through the air cavity, the air exhaust channel, the air throat, the flue gas exhaust channel and the flue gas throat are collinear with the central axis of the gas tube. The flue gas nozzle 2 improves the gas diffusion capacity in the furnace, that is, prolongs the travel distance or time. Compared with pure gas jet, the flue gas jet of the flue gas nozzle 2 makes the gas not decay too fast, stays longer in the furnace and travels deeper, so that the gas molecules have more opportunities to travel to the deep part of the furnace to find low-concentration oxygen molecules, which is more conducive to organizing low-oxygen diffusion combustion. The flue gas jet surrounds the gas jet and carries the gas molecules to quickly pass through the high-oxygen concentration area near the outlet of the air nozzle 1 (the core area of the air jet), and after the turning point of the central axis of the flue gas jet, the gas molecules have been diluted to 30% to 50% by the flue gas jet, entering the main section area of the air jet (the main section area of the flue gas jet or the space above the heating surface), where the low-concentration gas molecules meet high-temperature low-concentration oxygen molecules to realize low-oxygen diffusion combustion, the combustion reaction zone has small heat release intensity and the temperature rises by 300°C to 600°C, taking the inlet air temperature of 800°C to 1000°C as an example, the highest temperature in the furnace is lower than 1350°C, and the temperature distribution in the furnace is uniform. The invention has the ignition and combustion delay required by the expansion of the combustion flame volume, prevents high-concentration gas molecules (100%) from prematurely merging with high-concentration oxygen (21%) to ignite and burn, and prevents high-heat-intensity high-temperature air combustion conditions. The air throat 32 contains the flue gas throat 22 and the two have a common central axis, the air jet, the flue gas jet, the gas jet and the low-oxygen diffusion combustion gas flow have the same flow direction, and are combined into the same jet, which ensures the strong convective heat transfer capacity of low-oxygen diffusion combustion. The invention sends the combustion air into the furnace from the same vent in the furnace wall, and arranges the gas flow in the center of the high-temperature air flow to realize the surrounding of the gas flow by the high-temperature air flow, which ensures complete combustion and high gas utilization rate. The invention "combustion air double-dilution low-heat-release zone, strong convective heat transfer zone and strong radiation heat transfer zone" three zones overlap, and simultaneously meets the multiple production requirements of "energy saving, rapid melting and low nitrogen oxide emission".

[0028] The invention has adjustable performance. By adjusting the flue gas pressure of the flue gas cavity 21, the position, temperature and area of the low-oxygen diffusion combustion zone can be changed. The flue gas jet is a high-speed jet, and the core area length (initial section length) is more than 6.2 times the inner diameter of the tube outlet, which is equal to the core area length of the air jet. The higher the flue gas pressure of the flue gas cavity 21, the greater the flue gas flow injected into the furnace, the lower the gas concentration of the gas and flue gas mixed gas flow entering the main section area of the air jet, and the lower the low heat value, which is more conducive to organizing low-oxygen diffusion combustion.

[0029] The invention is characterized in that the furnace temperature is uniform. The smoke nozzle 2 promotes the uniform mixing of the combustion smoke. The smoke standard flow is 1-2.33 times the combustion gas standard flow, and the combustion gas volume concentration of the mixed gas flow entering the main section of the air injection flow decreases from 100% of the combustion gas pipe 1 to 30%-50%. The overall temperature level of the aluminum melting furnace is high, the highest temperature in the furnace is lower than 1350℃, the furnace temperature is uniform, the melting aluminum thermal efficiency and heat transfer rate are improved. The dilution of the combustion gas concentration uses low-temperature smoke, avoids using air, does not affect the control of the air consumption coefficient, the oxygen volume concentration of the exhaust smoke of the melting aluminum furnace is unchanged, and the smoke dilution coefficient involved in the conversion of the measured concentration of the atmospheric pollutants in the smoke into the standard concentration is unchanged.

Claims

1. A double-nozzle type diffusion burner, comprising a gas tube, a flue gas nozzle and an air nozzle, the air nozzle comprising an air cavity and an air throat pipe, the air cavity comprising a tapered frustum cone cylindrical air discharge passage, the flue gas nozzle comprising a flue gas cavity and a flue gas throat pipe, the flue gas cavity comprising a tapered frustum cone cylindrical flue gas discharge passage, the air throat pipe being embedded in a furnace wall air inlet hole, and a small end surface of the air discharge passage being connected to a furnace wall outer wall surface flange, characterized in that: The gas pipe extends into the flue gas throat pipe through the flue gas cavity, the flue gas nozzle extends into the air throat pipe through the air cavity, the air exhaust passage, the air throat pipe, the flue gas exhaust passage, the flue gas throat pipe and the central axis of the gas pipe are collinear, the outlet end face of the gas pipe, the outlet end face of the flue gas throat pipe, the outlet end face of the air throat pipe and the inner wall face of the furnace wall are coplanar, the outer wall face of the furnace wall, the inlet end face of the air throat pipe and the inlet end face of the flue gas throat pipe are coplanar, the small end face of the flue gas exhaust passage, the small end face of the air exhaust passage and the outer wall face of the furnace wall are coplanar, and the large end faces of the air exhaust passage and the flue gas exhaust passage are coplanar.

2. When the double-nozzle type diffusion burner is used, 10 kPaG and above flue gas enters the flue gas cavity, 10 kPaG-20 kPaG fuel gas enters the gas pipe, 800℃ and above air enters the air cavity, the air jet flow core of the air nozzle includes the flue gas jet flow core of the flue gas nozzle, the flue gas jet flow core includes the fuel gas jet core of the gas pipe, the initial segment of the flue gas jet flow and the air jet flow is equal, the flue gas jet flow core includes the fuel gas jet core, the flue gas standard state flow is 1-2.33 times the fuel gas standard state flow, the angle between the central axis of the air jet flow and the ground plane is maintained in the range of 6°-20° when the burner is installed downwardly, the air jet flow turning point intersects the top surface of the aluminum liquid, and the length of the initial segment of the air jet flow is 0.45-0.75 times the length of the aluminum liquid line on which the projection of the aluminum liquid surface is located.

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