A multi-stage air mixing device and method for a sintering flue gas denitration system

Abstract

The present invention discloses a multi-stage air mixing device and method for a sintering flue gas denitration system, including an air mixing structure, a primary air mixing structure, a secondary air mixing structure and a tertiary air mixing structure; the present invention conducts preliminary air mixing on the high-temperature flue gas at the outlet of the hot blast furnace after passing through the primary and secondary air mixing structures, and ensures that the flue gas temperature is reduced to a temperature range that the material can withstand, and uniformly injects it into the flue gas inlet of the denitration, and then passes through a three-stage mixer arranged downstream of the flue, and conducts local turbulence and overall swirl to fully and uniformly mix it with the sintering flue gas. The present invention uses a multi-stage air mixing device to increase the temperature of the sintering flue gas on the basis of ensuring that the flue gas temperature at the outlet of the hot blast furnace is within the temperature range that the material can withstand, so that the temperature of the sintering flue gas reaches a temperature range suitable for the SCR denitration system, and at the same time, the temperature of the final mixed flue gas is uniformly distributed over the entire flue cross section, thereby achieving the purpose of ultra-low emissions of the denitration system.

Description

[Technical field]

[0001] The invention relates to a multi-stage air mixing device and method for a sintering flue gas denitration system. [Background technology]

[0002] According to statistics, the steel industry ranks third, third, and first in all industries in terms of sulfur dioxide, nitrogen oxides, and particulate matter emissions. By implementing ultra-low emission transformation, the steel industry can rationally allocate resources, reduce environmental load, and control environmental pollution. According to the emission characteristics of the industry, it is proposed that the hourly average concentrations of particulate matter, sulfur dioxide, and nitrogen oxide emissions from sintering machine heads and pellet roasting flue gas should not exceed 10, 35, and 50 mg / m 3 .

[0003] Among ultra-low emission transformation technologies, SCR denitrification technology is currently the most widely used denitrification technology. At present, SCR denitrification technology has become the most extensive and mature flue gas purification technology for coal-fired power plants in the comprehensive implementation of ultra-low emission of atmospheric pollutants. SCR denitrification technology has the advantages of high denitrification efficiency (up to 90%), low secondary pollution, mature and reliable technology, etc. The technical advantages of SCR denitrification have been fully verified in the thermal power generation industry.

[0004] Temperature is an important factor affecting the denitration efficiency of SCR reaction. The optimal reaction temperature range of conventional SCR denitration is 320℃ to 360℃. When the SCR reaction temperature is lower than the lower limit of the applicable temperature range of the catalyst, the SCR reaction reductant NH3 reacts with SO2 and H2O in the atmosphere on the catalyst surface, reducing the reaction between NH3 and NO. x The catalytic reduction reaction, while the side reaction products (NH4)2SO4 and NH4HSO4 are attached to the catalyst surface, blocking the effective pores of the catalyst and accelerating the deactivation of the catalyst. If the reaction temperature is higher than the upper limit of the applicable temperature range of the catalyst, the catalyst channels and micropores are easily deformed under the action of high-temperature sintering, causing the effective reaction pores and area to be greatly reduced, resulting in a significant reduction in catalyst activity. The sintering flue gas temperature (<160°C) in the steel industry cannot reach the temperature of the conventional SCR denitrification reaction. The conventional heating method of the existing sintering flue gas is to pass the high-temperature flue gas (≥1000°C) produced by the hot blast furnace into the vertical flue at the entrance of the SCR reactor. In the actual operation process, there is a general problem of excessive temperature deviation, and the flue gas temperature in the local area of ​​the SCR reactor is too high or lower than the design temperature of the denitrification reaction, resulting in a decrease in denitrification efficiency and an increase in ammonia escape. In addition, the local high temperature caused by uneven air mixing can easily exceed the temperature tolerance range of general high-temperature resistant materials, resulting in insufficient structural strength and even the risk of burn-through. [Summary of the invention]

[0005] The purpose of the present invention is to solve the problems in the prior art and provide a multi-stage air mixing device and method for a sintering flue gas denitration system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A multi-stage air mixing device for a sintering flue gas denitration system, comprising:

[0008] An air mixing inlet, the air mixing inlet is connected to the air mixing distribution box;

[0009] An air mixing distribution box, wherein a first-stage air mixing box is arranged in the air mixing distribution box;

[0010] A first-stage air mixing box, which is arranged downstream of the hot air furnace outlet; the first-stage air mixing box is connected to the second-stage air mixing box through a flow guide device;

[0011] A secondary air mixing box, wherein a plurality of secondary air mixing distribution pipes are evenly arranged at the outlet of the secondary air mixing box;

[0012] A secondary air mixing distribution duct, the end of which extends into the flue, and a plurality of secondary air mixing nozzles are arranged on the portion of the secondary air mixing distribution duct located in the flue;

[0013] A two-stage air mixing nozzle, wherein a three-stage mixer is arranged correspondingly downstream of the two-stage air mixing nozzle.

[0014] The present invention is further improved in that:

[0015] The low-temperature sintering flue gas at the air mixing inlet enters the air mixing distribution box in two ways. The air mixing distribution box includes air mixing distribution pipes arranged on both sides of the primary air mixing box.

[0016] The air mixing distribution pipes on both sides of the first-stage air mixing box are of equal size and have equal spacing between them. The two sides are crossed and evenly arranged on the flue cross-section on both sides of the air mixing box.

[0017] The guide device includes several groups of guide plates, and the guide angle of each group of guide plates is determined according to the position of the secondary mixed air distribution duct, so that the airflow under each group of guide channels is evenly distributed to each group of secondary mixed air distribution ducts.

[0018] The portion of the secondary air mixing distribution duct extending into the flue is a tapered structure, so that the flow rate entering each group of secondary air mixing nozzles is the same.

[0019] The arrangement of the three-stage mixer matches the arrangement of the nozzles.

[0020] A multi-stage air mixing method for a sintering flue gas denitration system comprises the following steps:

[0021] Step 1: The low-temperature flue gas at the air inlet enters the air distribution boxes on both sides in two ways. The air distribution boxes are designed with a flow field structure to make the air flow rate from the air mixing box to the air distribution pipe the same; the low-temperature flue gas is fully and evenly mixed with the high-temperature flue gas at the hot blast furnace outlet through the air distribution pipe, and the high-temperature flue gas at the hot blast furnace outlet is preliminarily cooled so that the mixed temperature can be within the temperature range allowed by common high-temperature resistant materials;

[0022] Step 2, the high-temperature flue gas of the hot blast furnace after mixed air cooling enters the guide device. After the guide angle of each group of guide plates of the guide device is determined according to the position of the secondary mixed air distribution pipe, the flue gas is evenly divided under each group of guide channels, and enters the mixed air distribution pipe after being mixed again by the secondary mixed air box; the part of the secondary mixed air distribution pipe extending into the flue adopts a tapered type, so that the flow rate of each group of secondary mixed air nozzles entering is the same, and the secondary mixed air nozzles are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail flue of the sintering machine;

[0023] Step 3, the tail sintering flue gas enters the flue through the flue gas inlet, and is fully mixed with the air flow at the outlet of the secondary mixing nozzle through the third-stage mixer, and the sintering flue gas is heated up, and finally the temperature of the sintering flue gas reaches the temperature range required for SCR denitrification, and the mixed flue gas temperature is evenly distributed in the first layer catalyst inlet cross section.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention adopts a primary mixing method to ensure that the flue gas temperature at the hot blast furnace outlet is within the temperature range that commonly used high-temperature resistant materials can withstand, saving the high cost caused by the use of special high-temperature resistant materials in the flue. The present invention utilizes the mixing effect of the local vortex and the overall swirl of the three-stage mixer to make the sintering flue gas temperature more evenly distributed over the entire flue cross section, thereby improving the denitrification efficiency and reducing ammonia escape. The present invention adopts a multi-stage mixing structure and mixes step by step to ensure that the flue gas temperature deviation on the flue cross section after mixing is within ±10°C, meeting the temperature deviation range required by the SCR denitrification reactor. The present invention gives full play to the advantage of sufficient heat sources in the steel industry, and uses the high-temperature flue gas of the hot blast furnace to heat the sintering flue gas, so that the sintering flue gas temperature reaches the temperature range suitable for the SCR denitrification system, thereby achieving the purpose of ultra-low emissions of the denitrification system. Finally, the scheme of the present invention is reasonable, and ultra-low emissions of sintering flue gas denitrification in the steel industry are achieved without the need to add additional regulating valves and some complex heating equipment.

Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 It is a front view structural schematic diagram of the present invention;

[0028] Figure 2 It is a schematic diagram of the top view structure of the present invention;

[0029] Figure 3 It is a right view structural schematic diagram of the present invention.

[0030] Among them: 1-air mixing inlet, 2-air mixing distribution box, 3-air mixing distribution pipeline, 4-hot blast furnace outlet, 5-first-stage air mixing box, 6-flow guide device, 7-second-stage air mixing box, 8-second-stage air mixing distribution pipeline, 9-second-stage air mixing nozzle, 10-smoke inlet, 11-third-stage mixer, 12-smoke outlet. [Specific implementation method]

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0034] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0035] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0036] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0038] See also Figure 1-3 , this embodiment provides a multi-stage air mixing device of a sintering flue gas denitration system, including an air mixing structure, a primary air mixing structure, a secondary air mixing structure, and a tertiary air mixing structure;

[0039] The air mixing structure includes an air mixing inlet 1, an air mixing distribution box 2 and an air mixing distribution pipe 3. The low-temperature flue gas from the air mixing inlet 1 enters the air mixing distribution boxes 2 on both sides in two ways; the air mixing distribution pipes 3 on both sides are equal in size and have equal spacing between them. The two sides are crossed and evenly arranged on the flue cross section of the air mixing box 2 to ensure that the airflow is evenly distributed after the air mixing enters the entire hot blast furnace outlet flue.

[0040] The primary air mixing structure includes a hot blast stove outlet 4 and a primary air mixing box 5 . The primary air mixing box 5 is arranged downstream of the hot blast stove outlet 4 . The mixed air at the outlet of the mixed air distribution pipe 3 and the flue gas at the hot blast stove outlet 4 are fully mixed in the primary mixing box 5 .

[0041] The secondary air mixing structure includes a guide device 6, a secondary air mixing box 7, a secondary air mixing distribution pipe 8 and a secondary air mixing nozzle 9. The guide device 6 is evenly arranged at the inlet of the secondary mixing box 7, and the guide angle of each group of guide plates of the guide device 6 is determined according to the position of the secondary air mixing distribution pipe 8, and finally ensures that the airflow under each group of guide channels is evenly distributed to each group of secondary air mixing distribution pipes 8; the secondary air mixing distribution pipes 8 are evenly arranged at the outlet of the secondary mixing box 7; the part of the secondary air mixing distribution pipe 8 extending into the flue adopts a tapered type to ensure that the flow entering each group of secondary air mixing nozzles 9 is basically consistent; the secondary air mixing nozzles 9 are evenly arranged in the tail flue, and the number of the secondary air mixing nozzles 9 is determined according to the flue size design.

[0042] The three-stage air mixing structure includes a smoke inlet 10, a three-stage mixer 11 and a smoke outlet 12. The three-stage mixer 11 is arranged downstream of the two-stage air mixing nozzle 9. The arrangement of the three-stage mixer 11 matches the arrangement of the nozzle 9. The shape and arrangement of the three-stage mixer 11 are not limited to Figure 1 As shown, the tail flue gas enters the flue through the flue gas inlet 10 and is fully and evenly mixed with the outlet airflow of the secondary air mixing nozzle 9. The flue temperature cross-section is evenly distributed, and the sintering flue gas is heated to reach the temperature range required for SCR denitrification.

[0043] The present invention also discloses a multi-stage air mixing method for a sintering flue gas denitration system, comprising the following steps:

[0044] Step 1: The low-temperature flue gas from the air inlet 1 is divided into two paths and enters the two sides of the air distribution box 2. The air distribution box 2 is designed with a flow field structure to ensure that the air flow rate from the air mixing box 2 to the air distribution pipe 3 is basically the same. The low-temperature flue gas is fully and evenly mixed with the high-temperature flue gas from the hot blast furnace outlet 4 through the air distribution pipe 3, and the high-temperature flue gas from the hot blast furnace outlet 4 is preliminarily cooled to ensure that the mixed temperature can be within the temperature range allowed by common high-temperature resistant materials.

[0045] Step 2, the hot blast furnace high-temperature flue gas after mixed air cooling enters the guide device 6. After the guide angle of each group of guide plates of the guide device 6 is determined according to the position of the secondary mixed air distribution pipe 8, the flue gas is evenly distributed under each group of guide channels, and enters the mixed air distribution pipe 8 after being mixed again by the secondary mixed air box 7. The part of the secondary mixed air distribution pipe 8 extending into the flue adopts a tapered type to ensure that the flow rate entering each group of secondary mixed air nozzles 9 is basically the same. The secondary mixed air nozzles 9 are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail flue of the sintering machine.

[0046] Step 3, the tail sintering flue gas enters the flue through the flue gas inlet 10, and is fully mixed with the outlet airflow of the secondary mixing nozzle 9 through the third-stage mixer 11, and the sintering flue gas is heated up, and finally the temperature of the sintering flue gas reaches the temperature range required for SCR denitrification, and the mixed flue gas temperature is evenly distributed in the first layer catalyst inlet cross section.

[0047] Principle of the present invention:

[0048] In the present invention, when the flue gas temperature at the tail end of the sintering flue gas is relatively low, the high-temperature flue gas at the outlet of the hot blast furnace is first mixed with air step by step to cool it down, ensuring that the temperature is within the temperature allowable range of general high-temperature resistant materials, and then mixed with the sintering flue gas, and finally the temperature of the sintering flue gas is raised to the temperature range required for SCR denitration. Specifically, the present invention conducts preliminary air mixing on the high-temperature flue gas at the outlet of the hot blast furnace through the first and second air mixing structures, and ensures that the flue gas temperature is reduced to the temperature range that the material can withstand, and evenly injects it into the flue at the end of the sintering, and then passes through the three-stage mixer arranged downstream of the flue, and through the local turbulence and overall swirl effect, it is fully and evenly mixed with the sintering flue gas. In this way, the temperature of the sintering flue gas is stably maintained in a temperature range suitable for the SCR denitration catalyst. The present invention arranges a multi-stage air mixing device of the sintering flue gas denitrification system to increase the sintering flue gas temperature on the basis of ensuring that the flue gas temperature at the hot blast furnace outlet is within the temperature range that the material can withstand, so that the sintering flue gas temperature reaches a temperature range suitable for the SCR denitrification system, and at the same time makes the final mixed flue gas temperature evenly distributed in the entire catalyst inlet flue cross-section, thereby achieving the purpose of ultra-low emission of the denitrification system.

[0049] The working process of the present invention is as follows:

[0050] When the multi-stage air mixing device equipped with the sintering flue gas denitrification system is working, the low-temperature flue gas at the air inlet 1 is divided into two paths and enters the air distribution boxes 2 on both sides. The air distribution boxes 2 are designed with a flow field structure to ensure that the air flow from the air mixing box 2 to the air distribution pipe 3 is basically consistent. The low-temperature flue gas is fully and evenly mixed with the high-temperature flue gas at the hot blast furnace outlet 4 through the air distribution pipe 3, and the high-temperature flue gas at the hot blast furnace outlet 4 is preliminarily cooled to ensure that the mixed temperature can be within the temperature range allowed by common high-temperature resistant materials, and then enters the secondary air mixing structure.

[0051] After the mixed air is cooled, the high-temperature flue gas of the hot blast furnace enters the guide device 6. After the guide angle of each group of guide plates of the guide device 6 is determined according to the position of the secondary mixed air distribution pipe 8, the flue gas is evenly distributed under each group of guide channels, and then mixed again by the secondary mixed air box 7 and enters the mixed air distribution pipe 8. The part of the secondary mixed air distribution pipe 8 extending into the flue adopts a tapered type to ensure that the flow rate entering each group of secondary mixed air nozzles 9 is the same. The secondary mixed air nozzles 9 are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail flue of the sintering machine.

[0052] The tail sintering flue gas enters the flue through the flue gas inlet 10, and passes through the three-stage mixer with the outlet airflow of the secondary mixing nozzle 9. The local swirl and overall turbulence of the three-stage mixer fully mix the sintering flue gas, and finally the temperature of the sintering flue gas reaches the temperature range required for SCR denitrification, and the mixed flue gas temperature is evenly distributed in the first-layer catalyst inlet cross section.

[0053] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, 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 multi-stage air mixing device for a sintering flue gas denitration system, characterized in that: include: An air mixing inlet (1), the air mixing inlet (1) being connected to an air mixing distribution box (2); An air mixing distribution box (2), wherein a first-stage air mixing box (5) is arranged in the air mixing distribution box (2); the low-temperature sintering flue gas from the air mixing inlet (1) enters the air mixing distribution box (2) in two ways, and the air mixing distribution box (2) comprises air mixing distribution pipes (3) arranged on both sides of the first-stage air mixing box (5); the air mixing distribution pipes (3) on both sides of the first-stage air mixing box (5) are of equal size and have equal spacing between them, and are cross-arranged on both sides and evenly arranged on the flue cross section on both sides of the air mixing distribution box (2); A first-stage air mixing box (5), the first-stage air mixing box (5) being arranged downstream of the hot air furnace outlet (4); the first-stage air mixing box (5) being connected to the second-stage air mixing box (7) via a flow guide device (6); A secondary air mixing box (7), wherein a plurality of secondary air mixing distribution pipes (8) are evenly arranged at the outlet of the secondary air mixing box (7); A secondary air mixing distribution pipe (8), the end of which extends into the flue, and a plurality of secondary air mixing nozzles (9) are provided on the portion of the secondary air mixing distribution pipe (8) located in the flue; A secondary air mixing nozzle (9), wherein a tertiary mixer (11) is arranged downstream of the secondary air mixing nozzle (9); the flow guide device (6) comprises a plurality of groups of flow guide plates, wherein the flow guide angle of each group of flow guide plates is determined according to the position of the secondary air mixing distribution pipe (8), so that the airflow under each group of flow guide channels is evenly distributed to each group of secondary air mixing distribution pipes (8); the portion of the secondary air mixing distribution pipe (8) extending into the flue is a tapered structure, so that the flow rate entering each group of secondary air mixing nozzles (9) is the same; and the arrangement of the tertiary mixer (11) matches the arrangement of the secondary air mixing nozzles (9).

2. A multi-stage air mixing method for a sintering flue gas denitration system using the device of claim 1, characterized in that: The following steps are involved: Step 1, the low-temperature flue gas from the air inlet (1) is divided into two paths and enters the air distribution boxes (2) on both sides. The air distribution boxes (2) are designed with a flow field structure so that the air flow rates from the air distribution boxes (2) to the air distribution pipe (3) are the same; the low-temperature flue gas is fully and evenly mixed with the high-temperature flue gas from the hot blast furnace outlet (4) through the air distribution pipe (3), and the high-temperature flue gas from the hot blast furnace outlet (4) is preliminarily cooled so that the temperature after mixing is within the temperature range allowed by common high-temperature resistant materials; Step 2, the high-temperature flue gas of the hot blast furnace after mixed air cooling enters the guide device (6), and the guide angle of each group of guide plates of the guide device (6) is determined according to the position of the secondary mixed air distribution pipe (8), and the flue gas is evenly distributed under each group of guide channels, and is mixed again by the secondary mixed air box (7) and enters the secondary mixed air distribution pipe (8); the part of the secondary mixed air distribution pipe (8) extending into the flue adopts a tapered type, so that the flow rate of each group of secondary mixed air nozzles (9) entering is the same, and the secondary mixed air nozzles (9) are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail flue of the sintering machine; In step 3, the tail sintering flue gas enters the flue through the flue gas inlet (10), and is fully and evenly mixed with the outlet airflow of the secondary air mixing nozzle (9) through the third-stage mixer, so that the sintering flue gas is heated up, and finally the temperature of the sintering flue gas in the tail flue reaches the temperature range required for SCR denitrification, and the temperature of the mixed flue gas is evenly distributed in the cross section of the first catalyst inlet.

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