CN111545056A - Multistage air mixing device and method of sintering flue gas denitration system - Google Patents

Abstract

The invention discloses a multi-stage air mixing device and method for a sintering flue gas denitrification system, including an air mixing structure, a primary air mixing structure, a secondary air mixing structure and a tertiary air mixing structure; After the flue gas passes through the primary and secondary air mixing structures, preliminary air mixing is carried out, and the flue gas temperature is guaranteed to be lowered to the temperature range that the material can withstand, and the flue gas is uniformly injected into the denitration inlet flue, and then passes through the three-stage mixer arranged downstream of the flue. , perform local turbulence and overall swirl, so that it can be fully and evenly mixed with sintering flue gas. The invention uses the multi-stage air mixing device to increase the temperature of the sintering flue gas on the basis of ensuring that the temperature of the flue gas at the outlet of the hot blast furnace is within the temperature range that the material can bear, so that the temperature of the sintering flue gas reaches the suitable temperature range of the SCR denitration system, and at the same time, the temperature of the sintering flue gas is increased. The temperature of the final mixed flue gas is evenly distributed across the entire flue section, thereby realizing the ultra-low emission of the denitrification system.

Description

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

【Technical field】

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

【Background technique】

According to statistics, the emissions of sulfur dioxide, nitrogen oxides and particulate matter in the iron and steel industry are ranked 3rd, 3rd and 1st respectively among all industries. Through the implementation of ultra-low emission transformation, the iron and steel industry can reasonably allocate resources, reduce environmental load and control environmental pollution. According to the emission characteristics of the industry, it is proposed that the hourly average emission concentrations of sintering machine head, pellet roasting flue gas particulate matter, sulfur dioxide and nitrogen oxides should not be higher than 10, 35 and 50 mg/m ³ , respectively.

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

Temperature is an important factor affecting the denitration efficiency of SCR reaction. The optimal reaction temperature range for conventional SCR denitration is 320°C to 360°C. When the SCR reaction temperature is lower than the lower limit of the applicable temperature range of the catalyst, the SCR reaction reducing agent NH ₃ reacts with SO ₂ and H ₂ O in the atmosphere on the surface of the catalyst, reducing the catalytic reduction reaction of NH ₃ and NO _x , and at the same time The products of the side reaction (NH ₄ ) ₂ SO ₄ and NH ₄ HSO ₄ adhere to the surface of the catalyst, block the effective pores of the catalyst, and accelerate 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, which greatly reduces the effective reaction channel and area, resulting in a significant decrease in catalyst activity. The temperature of the sintering flue gas (<160℃) in the iron and steel industry cannot reach the temperature of the conventional SCR denitration reaction. The conventional heating method of the existing sintering flue gas is to pass the high-temperature flue gas (≥1000℃) produced by the hot blast furnace into the inlet of the SCR reactor vertically. For the straight flue, the temperature deviation is generally too large in the actual operation process, and the flue gas temperature in the local area of the SCR reactor is too high or lower than the design temperature of the denitration reaction, resulting in a decrease in denitration 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.

[Content of the invention]

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

To achieve the above object, the present invention adopts the following technical solutions to realize:

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

an air-mixing inlet, the air-mixing inlet is communicated with the air-mixing distribution box;

an air mixing distribution box, wherein a first-level air mixing box is arranged in the air mixing distribution box;

a first-level air mixing box, the first-level air mixing box is arranged downstream of the outlet of the hot blast stove; the first-level air mixing box is communicated with the second-level air mixing box through a flow guiding device;

A secondary air mixing box, the outlet of the secondary air mixing box is evenly arranged with several secondary air mixing distribution pipes;

a secondary air mixing distribution pipe, the end of the secondary air mixing distribution pipe extends into the flue, and a plurality of secondary air mixing nozzles are arranged on the part of the secondary air mixing distribution pipe located in the flue;

A secondary air mixing nozzle, and a tertiary mixer is correspondingly arranged downstream of the secondary air mixing nozzle.

The further improvement of the present invention is:

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

The air mixing distribution pipes on both sides of the first-stage air mixing box are equal in size and spaced equally, and the two sides are crossed and evenly arranged on the flue sections on both sides of the air mixing air box.

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 air mixing distribution pipe, so that the airflow under each group of guide channels is evenly distributed to each group of secondary mixed air distribution. in the pipeline.

The part of the secondary air mixing distribution pipe extending into the flue is a tapered structure, so that the flow rate entering each group of secondary air mixing nozzles is the same.

The arrangement of the three-stage mixers matches that of the nozzles.

A multi-stage air mixing method for a sintering flue gas denitrification system, comprising the following steps:

Step 1. The low-temperature flue gas at the air-mixing inlet enters the air-mixing distribution box on both sides in two ways. The air-mixing distribution box is designed through the flow field structure, so that the air flow from the air-mixing air-mixing box into the air-mixing distribution pipeline is the same; the low-temperature flue gas The high temperature flue gas at the outlet of the hot blast stove is fully and uniformly mixed through the air mixing distribution pipe, and the high temperature flue gas at the outlet of the hot blast stove is preliminarily cooled, so that the mixed temperature can be within the allowable temperature range of common high temperature resistant materials;

In step 2, the high-temperature flue gas of the hot blast stove after being cooled by the mixed air enters the diversion device. The air flow is evenly divided under the channel, and then mixed again by the secondary air mixing box, and then enters the air mixing distribution pipe; The flow rate is the same, and the secondary air mixing nozzles are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail flue of the sintering machine;

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 air mixing nozzle through the tertiary mixer. The temperature range required for denitration, and the temperature of the mixed flue gas is evenly distributed on the inlet section of the first layer catalyst.

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

The invention adopts the method of primary and primary mixing to ensure that the flue gas temperature at the outlet of the hot blast stove is within the temperature range that common high temperature resistant materials can bear, and saves the high cost caused by the use of special high temperature resistant materials for the flue. The invention utilizes the mixing effect of the local vortex flow and the overall swirl flow of the three-stage mixer, so that the temperature distribution of the sintering flue gas is more uniform in the entire flue duct section, the denitration efficiency is improved, and the ammonia escape is reduced. The invention adopts a multi-stage mixing structure and mixes step by step to ensure that the temperature deviation of flue gas on the cross section of the flue after mixing is within ±10°C, which meets the temperature deviation range required by the SCR denitration reactor. The invention makes full use of the advantages of sufficient heat sources in the iron and steel industry, and uses the high-temperature flue gas of the hot blast furnace to heat the sintering flue gas, so that the temperature of the sintering flue gas reaches a suitable temperature range of the SCR denitration system, thereby realizing the purpose of ultra-low emission of the denitration system. Finally, the present invention has a reasonable solution, and realizes ultra-low emission of denitrification of sintering flue gas in the iron and steel industry, without the need for additional adjustment valves and some complicated heating equipment.

【Description of drawings】

In order to describe the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the front view structure schematic diagram of the present invention;

Fig. 2 is the top view structure schematic diagram of the present invention;

FIG. 3 is a schematic view of the structure of the present invention from the right side.

Among them: 1- air inlet, 2- air distribution box, 3- air distribution pipeline, 4- hot blast stove outlet, 5- primary air mixing box, 6- diversion device, 7- secondary air mixing box, 8- Secondary air mixing distribution pipe, 9- secondary air mixing nozzle, 10- flue gas inlet, 11- tertiary mixer, 12- flue gas outlet.

【Detailed ways】

In order to make the purposes, 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inside", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings , or the orientation or positional relationship that the product of the invention is usually placed in use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are only used to differentiate the description and should not be construed to indicate or imply relative importance.

Furthermore, the presence of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather may be tilted slightly. For example, "horizontal" only means that its direction is more horizontal than "vertical", it does not mean that the structure must be completely horizontal, but can be slightly inclined.

In the description of the embodiments of the present invention, it should also be noted that, unless otherwise expressly specified and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. 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 an indirect connection through an intermediate medium, and it can be internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

Below in conjunction with accompanying drawing, the present invention is described in further detail:

1-3, the present embodiment provides a multi-stage air mixing device for a sintering flue gas denitrification system, including an air mixing structure, a primary air mixing structure, a secondary air mixing structure, and a tertiary air mixing structure;

The mixing structure includes the mixing inlet 1, the mixing distribution box 2 and the mixing distribution pipe 3. The low-temperature flue gas from the mixing inlet 1 enters the mixing distribution box 2 on both sides in two ways; the size of the mixing distribution pipe 3 on both sides is The size is equal and the distance between them is equal, and the two sides are crossed and evenly arranged on the flue section of the air mixing box 2 to ensure that the air flow is evenly distributed after entering the entire hot blast stove outlet flue.

The primary air mixing structure includes the hot blast stove outlet 4 and the primary air mixing box 5. The primary air mixing box 5 is arranged at the downstream position of the hot blast stove outlet 4, and the mixed air at the outlet of the air mixing distribution pipe 3 is in the same line with the flue gas at the hot blast stove outlet 4. Mix well in stage mixing box 5.

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

The three-stage air mixing structure includes a flue gas inlet 10 , a three-stage mixer 11 and a flue gas outlet 12 . The three-stage mixer 11 is arranged downstream of the two-stage air mixing nozzle 9 , and the arrangement of the three-stage mixer 11 is the same as that of the nozzle 9 . The shape and arrangement of the third-stage mixer 11 are not limited to those shown in Figure 1. The tail flue gas enters the flue through the flue gas inlet 10, and is fully mixed with the outlet air flow of the second-stage mixing nozzle 9. The cross-section distribution is uniform, and the sintering flue gas realizes the heating process and reaches the temperature range required for SCR denitration.

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

Step 1, the low-temperature flue gas from the air mixing inlet 1 enters both sides of the air mixing distribution box 2 in two ways. The air mixing distribution box 2 is designed through the flow field structure to ensure that the air mixing distribution box 2 enters the air mixing distribution pipeline 3 from the air mixing and air mixing box 2. The air flow rate is basically the same, the low temperature flue gas is fully and evenly mixed with the high temperature flue gas at the outlet 4 of the hot blast stove through the air mixing distribution pipe 3, and the high temperature flue gas at the outlet 4 of the hot blast stove is preliminarily cooled to ensure that the temperature after mixing can be within the normal range. Within the allowable temperature range of common high temperature resistant materials

In step 2, the high-temperature flue gas of the hot blast stove after being cooled by the mixed air enters the diversion device 6, and the diversion angle of each group of deflectors of the diversion device 6 is determined according to the position of the secondary mixed air distribution pipe 8, and the flue gas is The air flow is evenly divided under the group diversion channel, and after being mixed again by the secondary air mixing box 7, it enters the mixed air distribution pipe 8. The part of the secondary air mixing distribution pipe 8 extending into the flue adopts a tapered type to ensure that the flow rate entering each group of secondary air mixing nozzles 9 is basically the same. The flue gas evenly enters the tail flue of the sintering machine.

Step 3, the tail sintering flue gas enters the flue through the flue gas inlet 10, and is fully mixed with the outlet air flow of the secondary air mixing nozzle 9 through the tertiary mixer 11, and the sintering flue gas realizes the heating process, and finally makes the tail flue sintering flue gas. The temperature reaches the temperature range required for SCR denitration, and the temperature of the mixed flue gas is evenly distributed on the inlet section of the first layer catalyst.

Principle of the present invention:

In the present invention, when the smoke temperature at the tail of the sintering flue gas is relatively low, the high-temperature flue gas at the outlet of the hot blast furnace is firstly cooled by mixing air step by step to ensure that the temperature is within the temperature allowable range of general high-temperature resistant materials, and then mixed with the sintering flue gas. Raise the temperature of sintering flue gas to the temperature range required for SCR denitration. Specifically, in the present invention, the high-temperature flue gas at the outlet of the hot blast stove passes through the primary and secondary air mixing structures to perform preliminary air mixing, and ensures that the temperature of the flue gas is lowered to the temperature range that the material can withstand, and is uniformly injected into the flue at the end of the combustion. After the three-stage mixer arranged downstream of the flue, it is fully and evenly mixed with the sintering flue gas through the action of local turbulence and overall swirl. Then, the temperature of the sintering flue gas is stably maintained in the suitable temperature range of the SCR denitration catalyst. By arranging the multi-stage air mixing device of the sintering flue gas denitration system, the invention increases the sintering flue gas temperature on the basis of ensuring that the temperature of the flue gas at the outlet of the hot blast stove is within the temperature range that the material can bear, so that the sintering flue gas temperature reaches the SCR denitration system. At the same time, the temperature of the final mixed flue gas is evenly distributed in the entire catalyst inlet flue section, thereby achieving the purpose of ultra-low emission of the denitration system.

The working process of the present invention is as follows:

When the multi-stage air mixing device installed with the sintering flue gas denitration system works, the low-temperature flue gas from the air mixing inlet 1 enters the air mixing distribution box 2 on both sides in two ways. The air mixing distribution box 2 is designed through the flow field structure to ensure that The air flow from the mixed air box 2 into the mixed 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 stove outlet 4 through the mixed air distribution pipe 3, and the high temperature smoke from the hot blast stove outlet 4 is mixed. The air is initially cooled to ensure that the temperature after mixing can be within the allowable temperature range of common high temperature resistant materials, and then enters the secondary air mixing structure.

The high-temperature flue gas of the hot blast stove after being cooled by the mixed air enters the diversion device 6. After the diversion angle of each group of deflectors of the diversion device 6 is determined according to the position of the secondary mixed air distribution pipe 8, the flue gas flows through each set of diversion channels. The air flow is evenly distributed under the air, and it enters the mixed air distribution pipeline 8 after being mixed again by the secondary air 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 rate entering each group of secondary air mixing nozzles 9 is the same. The gas evenly enters the tail flue of the sintering machine.

The tail sintering flue gas enters the flue through the flue gas inlet 10, and passes through the tertiary mixer with the outlet air flow of the secondary air mixing nozzle 9, and is fully mixed by the local swirling flow and the overall turbulence of the tertiary mixer. The heating process is realized, and finally the temperature of the sintered flue gas of the tail flue reaches the temperature range required for SCR denitration, and the temperature of the mixed flue gas is evenly distributed on the inlet section of the first layer catalyst.

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 changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. a multi-stage air mixing device of a sintering flue gas denitration system, is characterized in that, comprises: an air-mixing inlet (1), the air-mixing inlet (1) is communicated with the air-mixing distribution box (2); an air mixing distribution box (2), wherein a first-level air mixing box (5) is arranged in the air mixing distribution box (2); A first-stage air mixing box (5), the first-stage air mixing box (5) is arranged downstream of the outlet (4) of the hot blast stove; connected; 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 duct (8), the end of the secondary air mixing distribution duct (8) protrudes into the flue, and the part of the secondary air mixing distribution duct (8) located in the flue is provided with several secondary air mixing nozzle (9); A secondary air mixing nozzle (9), a tertiary mixer (11) is correspondingly arranged downstream of the secondary air mixing nozzle (9). 2. The multi-stage air mixing device of the sintering flue gas denitration system according to claim 1, wherein the low-temperature sintering flue gas of the air mixing inlet (1) enters the air mixing distribution box (2) in two ways, The air mixing distribution box (2) includes air mixing distribution pipes (3) arranged on both sides of the primary air mixing box (5). 3. The multi-stage air mixing device of the sintering flue gas denitration system according to claim 1, wherein the air mixing distribution pipes (3) on both sides of the first-stage air mixing box (5) are equal in size, and two The distance between the two is equal, and the two sides are crossed and evenly arranged on the flue section on both sides of the air mixing box (2). 4. The multi-stage air mixing device of the sintering flue gas denitration system according to claim 1, characterized in that, the guide device (6) comprises several groups of guide plates, and the drainage angle of each group of guide plates is based on two The positions of the first-stage mixed air distribution pipes (8) are determined so that the airflow under each group of diversion channels is evenly distributed to each group of secondary mixed-air distribution pipes (8). 5. The multi-stage air mixing device of the sintering flue gas denitrification system according to claim 1, characterized in that, the part of the secondary air mixing distribution pipe (8) extending into the flue is a tapered structure, so that the parts entering each The flow rates of the second-stage air mixing nozzles (9) are the same. 6 . The multi-stage air mixing device of the sintering flue gas denitration system according to claim 1 , wherein the arrangement of the three-stage mixer ( 11 ) matches the arrangement of the nozzles ( 9 ). 7 . 7. A multi-stage air mixing method adopting the sintering flue gas denitrification system of any one of claims 1-6, characterized in that, comprising the following steps: Step 1, the low-temperature flue gas from the air mixing inlet (1) enters the air mixing distribution box (2) on both sides in two ways. The air flow of the mixed air distribution pipe (3) is the same; the low temperature flue gas is fully and evenly mixed with the high temperature flue gas from the hot blast stove outlet (4) through the mixed air distribution pipe (3), and the high temperature flue gas from the hot blast stove outlet (4) is mixed. Preliminary cooling, so that the temperature after mixing can be within the allowable temperature range of common high temperature resistant materials; In step 2, the high-temperature flue gas of the hot blast stove after being cooled by the mixed air 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). After that, the flue gas is divided into the air flow under each group of diversion channels, and is mixed again by the secondary air mixing box (7) and then enters the air mixing distribution pipe (8); the secondary air mixing distribution pipe (8) extends into the flue Part of the type adopts a tapered type, so that the flow rate of each group of secondary air mixing nozzles (9) is the same, and the secondary air mixing nozzles (9) are evenly arranged in the tail flue, so that the mixed flue gas evenly enters the tail smoke of the sintering machine. road; Step 3, the tail sintering flue gas enters the flue through the flue gas inlet (10), and is fully mixed with the air flow at the outlet of the secondary air mixing nozzle (9) through the tertiary mixer. The temperature of the sintering flue gas reaches the temperature range required for SCR denitration, and the temperature of the mixed flue gas is evenly distributed on the inlet section of the first layer catalyst.

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