An enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace

Abstract

The present invention provides a strengthened hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace, which includes a burner body. The burner body is fixed on the furnace wall through flange one. The burner body includes a burner barrel and a burner tip. The end of the burner barrel is communicated with the fuel gas supply pipe through flange two. The head end of the burner barrel is fixedly connected with the burner tip. The burner tip extends into the furnace wall. A number of gas spray holes are arranged on the spherical surface of the burner tip, and the total area of the gas spray holes at the center position of the spherical surface is larger than the total area of the gas spray holes at the non-center position of the spherical surface. And extending from the center position of the spherical surface to both sides, the total area of the gas spray holes gradually decreases. The present invention realizes the non-uniform distribution of the fuel gas, increases the flow rate of the fuel gas shooting towards the center of the furnace chamber, reduces the amount of fuel shooting towards the vicinity of the furnace wall, strengthens the mixing effect of the fuel gas and the air flowing vertically from bottom to top, and reduces the generation of thermal NOx.

Description

Technical Field

[0001] The invention belongs to the technical field of low - nitrogen combustion, and particularly relates to an enhanced hybrid gas low - nitrogen burner for an aluminum hydroxide roasting furnace. Background Art

[0002] The existing domestic production capacity of aluminum hydroxide roasting furnaces is 90 million tons per year, accounting for more than half of the world's output. The number of roasting furnaces is about 100 or more. At present, domestic aluminum hydroxide roasting furnaces are mainly suspended roasting furnaces. Natural gas and low - calorific - value coal gas are diffusely burned under the condition that the pre - heated air temperature is 600 - 750°C. The temperature of the flue gas after combustion is 950 - 1100°C. The high - temperature flue gas removes the attached water and crystal water of aluminum hydroxide to produce alumina that meets the requirements of electrolysis and other uses. Due to the use of high - temperature roasting technology, although the temperature of the flue gas after combustion is only 950 - 1100°C, the local high - temperature area in the combustion zone is as high as 1700°C, and a large amount of thermal - type nitrogen oxides are generated, making the NOx emissions of the roasting furnace range from 150 to 300 mg / m 3 , which is a key part of NOx emissions in the aluminum industry.

[0003] Since the NOx emissions of the roasting furnace are much higher than the current "Emission Standards for Pollutants in the Aluminum Industry" (GB25465 - 2010) (Revised in 2013), which requires NOx to be below 100 mg / m 3 The main methods to control NOx emissions at present are to carry out selective catalytic reduction (SCR) or selective non - catalytic reduction (SNCR) on the flue gas after combustion for denitrification, but there are problems such as high cost and secondary environmental pollution caused by ammonia slip. At present, the application of low - nitrogen burners has not been carried out in domestic aluminum hydroxide roasting furnaces, and most are single - channel burners. Therefore, there is an urgent need for a low - nitrogen burner to solve the above problems and achieve the goal of low - cost nitrogen oxide reduction in aluminum hydroxide roasting furnaces. Summary of the Invention

[0004] In view of this, the present invention aims to provide an enhanced hybrid gas low - nitrogen burner for an aluminum hydroxide roasting furnace. By means of non - uniform hole opening, the non - uniform distribution of fuel gas is realized, the flow rate of fuel gas injected towards the center of the furnace is increased, and the fuel amount injected towards the vicinity of the furnace wall is reduced. Thus, the mixing effect of fuel gas and the air flowing vertically upward is strengthened, the mixing of fuel gas and air on the horizontal cross - section of the furnace is more uniform, the temperature distribution in the furnace after combustion is more uniform, the high - temperature hot - spot area is reduced, and the generation of thermal - type NOx is reduced, achieving the purpose of low - nitrogen combustion.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] A reinforced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace, comprising a burner body, the burner body is fixed on the furnace wall through flange one, the burner body includes a burner barrel and a burner head, the end of the burner barrel is communicated with the fuel gas supply pipe through flange two, the head end of the burner barrel is fixedly connected with the burner head, the burner head extends into the furnace wall, a number of gas spray holes are opened on the spherical surface of the burner head, and the total area of the gas spray holes at the center position of the spherical surface is larger than the total area of the gas spray holes at the non-center position of the spherical surface, and extending from the center position of the spherical surface to both sides, the total area of the gas spray holes gradually decreases.

[0007] Further, two longitudinal gas spray holes are arranged on the circumference of the longitudinal great circle of the spherical surface of the burner head, and a plurality of horizontal gas spray holes are evenly arranged on the circumference of the horizontal great circle of the spherical surface. A number of horizontal gas spray holes and two longitudinal gas spray holes are symmetrically arranged along the top end of the spherical surface, and the aperture of the horizontal gas spray holes gradually decreases from the top end of the spherical surface to both sides. The total area of the two longitudinal gas spray holes is larger than the area of the largest horizontal gas spray hole.

[0008] Further, a number of gas spray holes are evenly opened on the circumference of the transverse great circle of the spherical surface of the burner head, and the gas spray holes at the center are opened along the circumference direction of the longitudinal great circle of the spherical surface of the burner head, which is a central long circular hole. The gas spray holes on both sides of the central long circular hole are side long circular holes. The gas spray holes adjacent to each side long circular hole are large circular holes. The gas spray holes adjacent to the large circular holes are small circular holes. The area of the central long circular hole is larger than the area of the two side long circular holes. The areas of the two side long circular holes are the same and larger than the area of the large circular holes. The areas of the two large circular holes are the same and larger than the area of the small circular holes.

[0009] Further, the number of gas spray holes is determined by the matching relationship between the flow rate of the fuel gas flowing through the gas spray holes and the air flow rate in the furnace wall.

[0010] Further, a plurality of the low-nitrogen burners are provided and are arranged in two staggered upper and lower layers on the furnace wall.

[0011] Further, the included angle between two adjacent low-nitrogen burners in the upper and lower layers is 10°-90°.

[0012] Further, a number of low-nitrogen burners are arranged in the upper middle part of the furnace chamber, and the combustion gas sprayed into the furnace chamber from the low-nitrogen burners is mixed with the air flowing vertically upward in the furnace chamber.

[0013] Further, the top ends of the burner heads of all the low-nitrogen burners are flush with or slightly retracted from the inner surface of the furnace wall.

[0014] Compared with the prior art, the enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace of the present invention has the following advantages:

[0015] (1) The enhanced hybrid gas low-nitrogen burner can achieve rapid and uniform mixing of fuel gas and high-temperature air. The area-weighted uniformity of fuel gas and high-temperature air can be increased by 25% compared with the existing burner, which can significantly reduce the local high-temperature points in the combustion zone and reduce the adverse effect of the diffusion combustion "hot spot" on NOx generation.

[0016] (2) The enhanced hybrid gas low-nitrogen burner adopts a modular integration method, with a small workload during the construction process, convenient maintenance and replacement, small system modification, low project implementation cost, low technical risk, and easy maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 is a schematic diagram of the layout of several enhanced hybrid gas low-nitrogen burners for an aluminum hydroxide roasting furnace according to an embodiment of the present invention;

[0019] Figure 2 is an installation schematic diagram of an enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace;

[0020] Figure 3 is a schematic diagram of one of the burner tips;

[0021] Figure 4 is a schematic diagram of another burner tip;

[0022] Figure 5 is a fuel distribution diagram of the existing burner;

[0023] Figure 6 is a fuel distribution diagram of the burner of the present application.

[0024] DESCRIPTION OF THE REFERENCE NUMERALS

[0025] 1 - Burner body, 2 - Furnace wall, 3 - First flange, 4 - Burner barrel, 5 - Burner tip, 6 - Second flange, 7 - Fuel gas supply pipe, 8 - Horizontal gas injection hole five, 9 - Horizontal gas injection hole three, 10 - Horizontal gas injection hole one, 11 - Longitudinal gas injection hole one, 12 - Horizontal gas injection hole six, 13 - Horizontal gas injection hole four, 14 - Horizontal gas injection hole two, 15 - Longitudinal gas injection hole two, 16 - Central long circular hole, 17 - Side long circular hole, 18 - Large circular hole, 19 - Small circular hole. DETAILED DESCRIPTION OF THE INVENTION

[0026] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0028] As Figures 1 - 3 shown, a strengthened hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace includes a burner body 1. The burner body 1 is fixed on a furnace wall 2 through a first flange 3. The burner body 1 includes a burner barrel 4 and a burner tip 5. The end of the burner barrel 4 is communicated with a fuel gas supply pipe 7 through a second flange 6. The head end of the burner barrel 4 is fixedly connected to the burner tip 5. The burner tip 5 extends into the furnace wall 2. A number of gas spray holes are formed on the spherical surface of the burner tip 2, and the total area of the gas spray holes located at the center position of the spherical surface is larger than the total area of the gas spray holes at the non-center position of the spherical surface. And extending from the center position of the spherical surface to both sides, the total area of the gas spray holes gradually decreases.

[0029] One of the structural forms is: two longitudinal gas spray holes are arranged on the circumference of the longitudinal great circle of the spherical surface of the burner tip 2, and a plurality of horizontal gas spray holes are uniformly arranged on the circumference of the horizontal great circle of the spherical surface. A number of horizontal gas spray holes and two longitudinal gas spray holes are symmetrically arranged along the top end of the spherical surface, and the aperture of the horizontal gas spray holes gradually decreases from the topmost end of the spherical surface to both sides. The total area of the two longitudinal gas spray holes is larger than the area of the largest horizontal gas spray hole. The number of gas spray holes is determined by the matching relationship between the flow velocity of the fuel gas flowing through the gas spray holes and the air flow velocity in the furnace wall 2. Specifically, it can be: six horizontal gas spray holes are provided, namely horizontal gas spray hole five 8, horizontal gas spray hole three 9, horizontal gas spray hole one 10, horizontal gas spray hole six 12, horizontal gas spray hole four 13 and horizontal gas spray hole two 14; the two longitudinal gas spray holes are respectively: longitudinal gas spray hole one 11 and longitudinal gas spray hole two 15. Longitudinal gas spray hole one 11, longitudinal gas spray hole two 15 and horizontal gas spray hole one 10, horizontal gas spray hole two 14 have the same aperture and hole pitch. The aperture of horizontal gas spray hole five 8 is the same as that of horizontal gas spray hole six 12 and is the smallest. The aperture of horizontal gas spray hole three 9 is the same as that of horizontal gas spray hole four 13 and is slightly larger. The aperture of horizontal gas spray hole one 10 and horizontal gas spray hole two 14 is the same and is the largest. Specifically, it can be that the outer diameter of the ball head is 273 mm, the wall thickness is 20 mm, and the aperture distribution is from left to right. The left one is 35.6 mm, the left two is 39.2 mm, the left three is 46.6 mm, each of the two central longitudinal holes is 45.4 mm, the right three is 46.6 mm, the right two is 39.2 mm, and the right one is 35.6 mm.

[0030] As Figure 4As shown in the figure, another structural form is as follows: a number of gas injection holes are evenly arranged on the circumference of the lateral great circle of the spherical surface of the burner tip 2, and the gas injection hole located at the center is arranged along the circumference direction of the longitudinal great circle of the spherical surface of the burner tip 2, which is the central long circular hole 16. The gas injection holes on both sides of the central long circular hole 16 are the side long circular holes 17. The gas injection holes adjacent to each side long circular hole 17 are the large circular holes 18. The gas injection holes adjacent to the large circular holes 18 are the small circular holes 19. The area of the central long circular hole 16 is larger than the area of the two side long circular holes 17. The areas of the two side long circular holes 17 are the same and larger than the area of the large circular holes 18. The areas of the two large circular holes 18 are the same and larger than the area of the small circular holes 19. The aperture of the large circular holes 18 is 28mm, the aperture of the small circular holes 19 is 27mm, the aperture of the side long circular holes 17 is 28mm, the straight edge length is 10.4mm, the aperture of the central long circular hole 16 is 28mm, the straight edge length is 59mm, the outer diameter of the ball head is 219mm, the wall thickness is 20mm, and the clamping angle of the center connection line of adjacent two gas injection holes and the spherical center of the spherical surface of the burner tip 2 is 21°.

[0031] Multiple low-nitrogen burners are provided and are arranged in two staggered upper and lower layers on the furnace wall 2. The number of low-nitrogen burners is 4 - 36, and the included angle between two adjacent low-nitrogen burners in the upper and lower layers is 10° - 90°. Specifically, it can be: 12 low-nitrogen burners are provided, and the included angle between two adjacent low-nitrogen burners in the upper and lower layers is 30°. The number of low-nitrogen burners is adjusted accordingly according to the power. A number of low-nitrogen burners are arranged in the upper-middle part of the furnace chamber 2. The combustion gas sprayed into the furnace chamber 2 from the low-nitrogen burners is mixed with the air flowing vertically upward in the furnace chamber 2. The top ends of the burner tips 2 of all low-nitrogen burners are flush with the inner surface of the furnace wall 2 or slightly retracted to prevent the wear of the burner tips by the pulverized coal flow in the furnace.

[0032] The fuel gas passes through the fuel gas supply pipe 7, passes through the burner barrel 4, and is sprayed into the roasting furnace from a number of gas injection holes on the burner tip 5, and is mixed with the preheated air at 600 - 750°C flowing vertically upward. After diffusion combustion, it is mixed with the alumina material fed into the furnace, removes the crystal water of the material, completes the crystal form transformation, and obtains the target product alumina. In this application, the non-uniform distribution of the fuel gas is realized through the opening mode and the gradual change of the aperture of a number of gas injection holes on the burner tip 5, increasing the flow rate of the fuel gas shooting towards the center of the furnace chamber and reducing the fuel amount shooting towards the vicinity of the furnace wall. Thereby, the mixing effect of the fuel gas and the air flowing vertically upward is strengthened, the fuel gas and the air are more uniformly mixed in the horizontal cross-section of the furnace chamber, the temperature distribution in the furnace after the fuel gas combustion is more uniform, the high-temperature hot spot area is reduced, and thus the generation of thermal NOx is reduced, achieving the purpose of low-nitrogen combustion.

[0033] Through cold-state simulation by computer, the existing fuel distribution in the burner area is as Figure 5As shown, the fuel distribution of the burner structure of the present application is as follows Figure 6 As shown, through Figure 5 and Figure 6 comparison, it can be clearly seen that the fuel concentration in the central area of the furnace of the new burner of the present application is significantly higher than that in the central area of the furnace of the existing widely used original burner. Moreover, in terms of the fuel distribution uniformity, it can also be seen that after modifying the burner head, the penetration performance of the fuel has been significantly improved; numerically, the fuel mixing uniformity has also increased from 0.6055 of the prototype burner to 0.7582. Whether in the observation of the cloud map or the manifestation of the data, after changing the burner structure, the fuel distribution has been significantly improved. The area-weighted uniformity of the fuel gas and the high-temperature air can be increased by 25% compared with the existing burner, which can significantly reduce the local high-temperature points in the combustion zone and reduce the adverse effects of the diffusion combustion "hot spots" on the formation of NOx.

[0034] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A strengthened hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace, characterized in that: It includes a burner body (1), and the burner body (1) is fixed on the furnace wall (2) through a first flange (3). The burner body (1) includes a burner barrel (4) and a burner tip (5). The end of the burner barrel (4) is communicated with a fuel gas supply pipe (7) through a second flange (6). The head end of the burner barrel (4) is fixedly connected to the burner tip (5). The burner tip (5) extends into the furnace wall (2). A number of gas spray holes are formed on the spherical surface of the burner tip (5), and the total area of the gas spray holes located at the center position of the spherical surface is larger than the area of any gas spray hole at the non-center position of the spherical surface, and extends from the center position of the spherical surface to both sides. The total area of the gas spray holes at the same latitude gradually decreases. The number of the gas spray holes is determined by the matching relationship between the flow rate of the fuel gas flowing through the gas spray holes and the air flow rate in the furnace wall (2). A plurality of low-nitrogen burners are provided and are arranged in two staggered upper and lower layers on the furnace wall (2). The included angle between two adjacent low-nitrogen burners in the upper and lower layers is 10°-90°.

2. The enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace according to claim 1, characterized in that: Two longitudinal gas spray holes are arranged on the circumference of the longitudinal great circle of the spherical surface of the burner tip (5), and a plurality of horizontal gas spray holes are evenly arranged on the circumference of the horizontal great circle of the spherical surface. A number of horizontal gas spray holes and two longitudinal gas spray holes are symmetrically arranged along the top end of the spherical surface, and the aperture of the horizontal gas spray holes gradually decreases from the topmost end of the spherical surface to both sides. The total area of the two longitudinal gas spray holes is larger than the area of the largest horizontal gas spray hole.

3. The enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace according to claim 1, wherein: A number of gas spray holes are evenly formed on the circumference of the transverse great circle of the spherical surface of the burner tip (5). The gas spray hole located at the center is formed along the circumference direction of the longitudinal great circle of the spherical surface of the burner tip (5) as a central long circular hole (16). The gas spray holes on both sides of the central long circular hole (16) are side long circular holes (17). The gas spray holes adjacent to each side long circular hole (17) are large circular holes (18). The gas spray holes adjacent to the large circular holes (18) are small circular holes (19). The area of the central long circular hole (16) is larger than the area of the two side long circular holes (17). The areas of the two side long circular holes (17) are the same and larger than the area of the large circular hole (18). The areas of the two large circular holes (18) are the same and larger than the area of the small circular hole (19).

4. The enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace according to claim 1, wherein: A number of low-nitrogen burners are arranged in the upper middle part of the furnace wall (2). The combustion gas sprayed into the furnace wall (2) from the low-nitrogen burners is mixed with the air flowing vertically upward in the furnace wall (2).

5. The enhanced hybrid gas low-nitrogen burner for an aluminum hydroxide roasting furnace according to claim 1, wherein: The top ends of the burner tips (5) of all the low-nitrogen burners are flush with or slightly retracted from the inner surface of the furnace wall (2).

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