CN110841475A - A cement kiln SCR denitration system and its technological process - Google Patents

Abstract

The invention discloses a cement kiln SCR denitration system, comprising a preheater, an ammonia water conveying and spraying device, an SCR reaction tower, a power generation boiler, an ash return conveying device and a high temperature fan. The outlet of the preheater passes through a pipeline I and an SCR reaction tower. The inlet of the SCR reaction tower is connected to the inlet of the ammonia water conveying and injection device, and the injection port of the ammonia water conveying and injection device is sealed and connected to the pipeline I. The ammonia water and the waste gas are mixed into the SCR reaction tower. The boiler is connected, the ash outlet of the power boiler is connected with the ash return conveying device, and the gas outlet of the power boiler is connected with the high temperature fan. The exhaust gas after SCR denitration is sent to the next process by the high temperature fan. The invention makes full use of the technological characteristics of the cement sintering system, and a set of SCR denitration system is arranged at the outlet of the preheater at the kiln end. In order to reduce NOx emission, improve denitration reaction efficiency, and reduce ammonia escape.

Description

A cement kiln SCR denitration system and its technological process

technical field

The invention belongs to the technical field of cement production equipment, and particularly relates to a cement kiln SCR denitration system and its technological process.

Background technique

By the end of 2018, there were a total of 1,680 new dry-process cement production lines nationwide, and the actual clinker production capacity exceeded 2 billion tons. A large amount of NOx is generated during the production of cement clinker. According to statistics, NOx emissions from cement enterprises account for about 7% of the total NOx emissions in the country, which seriously affects the development of the national economy. At present, the most widely used denitrification technologies in the cement industry mainly include staged combustion denitrification and SNCR denitrification. The staged combustion denitrification method has no operating cost and does not affect the normal operation of the firing system. The denitration efficiency is about 30%, and the effect is stable, but it cannot meet the NOx The current national environmental protection standards for emissions can be used as the first step for denitrification measures; and the SNCR denitrification method, as a measure to further reduce the concentration of NOx emissions, has been widely used in the cement industry because of its simple system process and low investment. The method has problems such as low utilization efficiency, large consumption of ammonia water as a reducing agent, high ammonia escape, corrosion of pipes and equipment, and secondary pollution.

The technology that can effectively control NOx emissions, improve the efficiency of ammonia water utilization, and reduce ammonia escape is SCR denitrification technology, which is rarely used in cement kiln flue gas denitrification projects and is still in its infancy.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a cement kiln SCR denitration system and its technological process, which are used to promote the progress of domestic denitration environmental protection technology.

In order to achieve the above purpose, the technical scheme of the present invention is: a cement kiln SCR denitration system, characterized in that it includes a preheater, an ammonia water conveying and injection device, an SCR reaction tower, a power generation boiler, an ash return conveying device and a high-temperature fan, The outlet of the preheater is connected with the inlet of the SCR reaction tower through the pipeline I, the injection port of the ammonia water conveying and injection device is sealed and connected to the pipeline I, the ammonia water and the waste gas are mixed into the SCR reaction tower, and an outlet of the SCR reaction tower is connected to the return. The ash conveying device is connected, the other outlet of the SCR reaction tower is connected with the power generation boiler, the ash outlet of the power generation boiler is connected with the ash return conveying device, and the gas outlet of the power boiler is connected with the high temperature fan.

Further, the outlet of the preheater is connected with the power generation boiler through the pipeline II, the pipeline II is provided with a valve II, the pipeline I is provided with a valve I, and the pipeline of the preheater is also provided with an injection port for injecting ammonia water, Ammonia water is injected into the preheater through the injection port.

Further, the SCR reaction tower is provided with a diversion uniform distribution plate, a catalyst and an ash cleaning device, the diversion uniform distribution plate is arranged at the entrance of the reaction tower, and the diversion uniform distribution plate is connected to the tower body of the SCR reaction tower. , the catalyst is connected to the tower body of the SCR reaction tower and located below the diversion uniform distribution plate, and a ash cleaning device is arranged above the catalyst.

Further, the guide uniform distribution plate is made of inverted angle steel, a gap is provided between two adjacent angle steels, and the gas passes through the gap between the adjacent two angle steels.

Further, the SCR reaction tower is provided with multiple layers of flow-guiding uniform distribution plates, and the distance between two adjacent layers of the flow-guiding and uniform distribution plates increases sequentially.

Further, the SCR reaction tower is provided with multi-layer catalysts, and a ash cleaning device is arranged above each layer of the catalyst, and the gas enters the catalyst through the ash cleaning device for reaction, and the catalyst is a honeycomb catalyst or a plate catalyst.

Further, the catalyst is arranged obliquely or the longitudinal section of the catalyst is a triangular structure. When the catalyst is arranged at an inclination, the catalysts between the layers are parallel to each other. The thickest part of the upper layer catalyst corresponds to the thinnest part of the lower layer catalyst.

Further, the bottom of the SCR reaction tower is provided with an outlet I for ash discharge and an outlet II for gas discharge, the outlet II forms a U-shaped structure with the SCR reaction tower through a pipeline, the outlet I is connected with the ash return conveying device, and the outlet II is connected with the power generation. Boiler connection.

Further, the ash cleaning device includes a rake-type ash cleaner, a motor, a push rod and a hanging rail, the suspension rail is fixedly connected to the side wall of the SCR reaction tower body, and the rake-type ash cleaner is slidably connected to the SCR reaction tower through a pulley. On the hanging rail, one end of the push rod is connected with the rake type ash cleaner, and the other end of the push rod is connected with the motor, and the rotation of the motor drives the push rod to push the rake type ash cleaner to slide on the hanging rail.

The invention also relates to a technological process of a cement kiln SCR denitration system, characterized in that: the technological process is:

a) The waste gas containing NOx enters the preheater from the kiln end. After being preheated by the preheater, the waste gas containing NOx at 300-400℃ is introduced into the SCR reaction tower from the outlet of the preheater through pipeline I; at the same time, ammonia water is transported and injected The device injects ammonia water to pipeline I to mix with the exhaust gas containing NOx;

b) When ammonia water encounters high temperature waste gas, it is gasified into ammonia gas. The gasified ammonia water is mixed with NOx-containing waste gas and then enters the SCR reaction tower. Ammonia is the reducing agent. When the mixed gas passes through the catalyst in the SCR reaction tower, the ash cleaning device The dust in the exhaust gas is raised all the time in the blowing state, and the NOx is reduced to N ₂ and H ₂ O through the catalytic action of the catalyst to complete the denitration;

c) The generated N ₂ and H ₂ O are in a high temperature state, the exhaust gas after denitration enters the power generation boiler, uses the waste heat to generate electricity, and then enters the high temperature fan, and the exhaust gas after denitrification by the SCR reaction tower enters the next process from the high temperature fan.

The advantages of adopting the technical solution of the present invention are:

1. The present invention makes full use of the technical characteristics of the cement sintering system. A set of SCR denitration system is arranged at the outlet of the preheater at the kiln end. After the NOx in the preheater exhaust gas passes through the SCR denitration system, under the action of a catalyst, the ammonia water and NO are promoted. reaction to reduce NOx emissions, improve denitration reaction efficiency, and reduce ammonia escape.

2. The present invention adopts a high-temperature arrangement and an efficient rake-type dust-cleaning system to ensure the stable operation of the system without setting up a separate dust-collecting device.

3. The present invention can arrange catalysts with different layers as required, effectively ensure the denitration efficiency (up to 95%), and can effectively control the ammonia escape ≤ 10mg/Nm ³ (10% O ₂ content), and the NOx emission concentration can be controlled At 50 mg/Nm ³ (10% O ₂ content).

4. The present invention controls the temperature difference between the inlet and outlet of the SCR reaction system within 10°C, effectively reducing the impact on the power generation of the power generation boiler.

5. The arrangement of the diversion and uniform distribution plate of the present invention has a diversion effect on the exhaust gas entering the reaction tower, and makes the exhaust gas evenly distributed in the reaction tower, effectively ensuring the uniformity of the exhaust gas entering the catalyst reaction tower.

6. The present invention sets the ammonia water injection port on the preheater. First, it can prolong the mixing time of the gas and the ammonia water, so that the reducing medium ammonia and the gas are mixed more fully; second, it is beneficial to the temperature of the ammonia water, and the gas temperature at the preheater position is 500 ° C. At the same time, the ammonia water is quickly dehydrated and vaporized, which is beneficial to the reaction of ammonia and NO.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:

FIG. 1 is a schematic diagram of the overall structure of the SCR denitration system of the cement kiln of the present invention.

FIG. 2 is a schematic diagram of the overall structure of the SCR denitration reaction tower of the present invention.

FIG. 3 is a schematic structural diagram of a flow-guiding uniform distribution plate of the present invention.

FIG. 4 is a schematic cross-sectional view of the diversion uniform distribution plate of the present invention.

Figure 5 is a schematic diagram of the inclined arrangement of the catalyst of the present invention.

FIG. 6 is a schematic diagram of the triangular structure arrangement of the catalyst of the present invention.

The marks in the above figures are: 1, preheater; 11, pipeline I; 12, pipeline II; 13, valve I; 14, valve II; 2, ammonia water conveying and injection device; 21, injection port; 3, SCR Reaction tower; 31, inlet of reaction tower; 4, power generation boiler; 41, ash outlet; 42, gas outlet; 5, ash return conveying device.

Detailed ways

In the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal" ", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "planar direction", "circumferential", etc. indicated the orientation or position relationship is based on The orientation or positional relationship shown in the drawings is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as Limitations of the present invention.

As shown in Figures 1 to 6, a cement kiln SCR denitration system includes a preheater 1, an ammonia water conveying and injection device 2, an SCR reaction tower 3, a power generation boiler 4, an ash return conveying device 5 and a high temperature fan 6. The outlet of the preheater 1 is connected to the inlet of the SCR reaction tower 3 through the pipeline I11, the injection port 21 of the ammonia water conveying and injection device 2 is sealed and connected to the pipeline I11, and the ammonia water and the waste gas are mixed into the SCR reaction tower 3, and the SCR reaction tower 3 One outlet of the SCR reaction tower 3 is connected to the power generation boiler 4, the ash outlet 41 of the power generation boiler 4 is connected to the ash return conveying device 5, and the gas outlet 42 of the power generation boiler 4 is connected to the power generation boiler 4. The high temperature fan 6 is connected. The exhaust gas after SCR denitration is sent to the next process by the high temperature fan 6 .

The outlet of the preheater 1 is connected to the power generation boiler 4 through the pipeline II12, the pipeline II12 is provided with a valve II14, and the pipeline I11 is provided with a valve I13. When valve I13 and valve II14 are both open, SCR reaction tower 3 is connected in parallel with preheater 1 and then connected in series with power boiler 4; under normal circumstances, valve I13 is normally open, valve II14 is normally closed, and preheater 1 , SCR reaction tower 3 and power generation boiler 4 are connected in series; if the SCR system fails, the SCR reaction tower 3 can be withdrawn separately through the inlet and outlet valves of the SCR reaction tower 3, and the preheater and the power generation boiler 4 operate normally, that is, The failure of the SCR reaction system will not affect the operation of the kiln tail waste heat power generation system.

The pipeline of the preheater 1 is also provided with an injection port 21 for injecting ammonia water, and the ammonia water is injected into the preheater 1 through the injection port 21 . The ammonia water injection port is arranged on the preheater. First, it can prolong the mixing time of the gas and ammonia water, so that the reducing medium ammonia and the gas can be mixed more fully; second, it is beneficial to the temperature of the ammonia water. Rapid dehydration and vaporization, which is beneficial to the reaction of ammonia and NO.

The SCR denitration reaction tower is the core component of the SCR denitration system. The SCR reaction tower 3 is provided with a diversion uniform distribution plate 32, a catalyst 33 and an ash cleaning device 34. The diversion uniform distribution plate 32 is arranged at the inlet 31 of the reaction tower. The uniform distribution plate 32 is connected to the tower body of the SCR reaction tower 3, and the catalyst 33 is connected to the tower body of the SCR reaction tower 3 and is located below the diversion uniform distribution plate 32. Above the catalyst 33, a dust cleaning device 34 is arranged to remove dust. The device 34 is connected to the tower body of the SCR reaction tower 3 and located below the flow guide uniform distribution plate 32 .

The diversion uniform distribution plate 32 is made of inverted angle steel 321, a gap is provided between two adjacent angle steels, and the gas passes through the gap between the adjacent two angle steels. In order to prevent the diversion uniform distribution plate 32 from being blocked by the dust in the exhaust gas, and to avoid the accumulation of dust on the surface of the diversion uniform distribution plate 32, the inclination of the angle steel plate and the distance between the two adjacent angle steels are limited. The distance between the two adjacent angle steels is 50-150mm, and the included angle of the angle steels is 70-110°. The setting of the guide uniform distribution plate 32 plays a guiding role for the exhaust gas entering the SCR reaction tower 3, and makes the exhaust gas evenly distributed in the SCR reaction tower 3, effectively ensuring the uniformity of the exhaust gas entering the catalyst reaction tower. If the SCR reaction tower 3 is not provided with the diversion uniform distribution plate 32, after the exhaust gas enters the reaction tower, there will be more exhaust gas in the middle of the reaction tower and less exhaust gas around, resulting in more exhaust gas passing through the middle of the catalyst and less exhaust gas passing through the positions around the catalyst. In this way, there will be insufficient catalysts in the middle position, resulting in insufficient exhaust gas reaction, which affects the denitration reaction and cannot meet the denitration requirements; and the catalysts in the surrounding positions cannot be fully used, resulting in waste of catalysts.

The SCR reaction tower 3 is provided with a multi-layer flow-guiding and uniform distribution plate 32, and the distance between two adjacent layers of the flow-guiding and uniform distribution plate 2 increases sequentially.

由于从上到下导流均布板32的面积依次增大，导流均布板2对气流的阻力f依次增大，为保证通过相邻两层导流均布板32气体的速度相差尽可能的小，所以设计Δh依次增大，即相邻两层导流均布板32之间的距离依次增大。优选的，SCR反应塔3中设有三层导流均布板32，第一层导流均布板32与第二层导流均布板32之间的距离小于第二层导流均布板32与第三层导流均布板32之间的距离，由于层间距变大，可使气体从上一层到下一层时扩散面积变大，所以在导流均布板32面积依次增大的同时，为保证气体有尽可能大的扩散面积，层间的间距要变大。Suppose the distance between the two adjacent layers of diversion and uniform distribution plates 32 is Δh, the resistance of the diversion and uniform distribution plates 32 to the gas is f, and the velocity of the gas passing through the two adjacent layers of diversion and uniform distribution plates 32 is ν ₁ , ν ₂ , according to the law of conservation of mechanical energy:

Since the area of the uniform distribution plate 32 increases sequentially from top to bottom, the resistance f of the uniform distribution plate 2 to the air flow increases sequentially. In order to ensure that the speed difference of the gas passing through the adjacent two layers of uniform distribution plate 32 is as small as possible The possibility is small, so the design Δh increases sequentially, that is, the distance between the two adjacent layers of the flow guide uniform distribution plates 32 increases sequentially. Preferably, the SCR reaction tower 3 is provided with three layers of diversion and distribution plates 32, and the distance between the first layer of diversion and distribution plates 32 and the second layer of diversion and distribution plates 32 is smaller than that of the second layer of diversion and distribution plates The distance between 32 and the third-layer diversion uniform distribution plate 32, because the layer spacing becomes larger, the diffusion area of the gas can be increased from the upper layer to the next layer, so the area of the diversion uniform distribution plate 32 increases in turn. At the same time, in order to ensure that the gas has as large a diffusion area as possible, the spacing between the layers should be larger.

The SCR reaction tower 3 is provided with multi-layer catalysts 33, and a cleaning device 34 is arranged above each layer of catalyst 33. The gas enters the catalyst 33 through the cleaning device 34 for reaction, and the catalyst 33 is a honeycomb catalyst or a plate catalyst.

Generally, the catalysts 33 are arranged horizontally. When the catalysts 33 are arranged horizontally, the catalysts 33 between the layers are parallel to each other, and the catalysts in the same layer have the same thickness. Preferably, the catalyst 33 can also be inclined to increase the contact area of the catalyst to make the reaction more thorough, or the longitudinal section of the catalyst 33 is a triangular structure. One is that the triangular structure itself has stability, and the other is that it can increase the contact between the gas and the catalyst. time. When the catalysts 33 are arranged obliquely, the catalysts 33 between the layers are parallel to each other. When the longitudinal section of the catalysts 33 is a triangular structure, the two adjacent layers of the triangular catalysts are arranged opposite each other, that is, the thickest part of the upper catalyst 33 and the thinnest part of the lower catalyst 33 Correspondingly, as shown in Fig. 6, it is preferable that the number of layers of the catalyst with triangular structure is even, which can ensure that the contact time between all the exhaust gas and the catalyst becomes longer, and the reaction is more thorough.

Different layers of catalysts can be arranged as needed to effectively ensure the denitration efficiency (up to 95%), and can effectively control the ammonia escape ≤10mg/Nm ³ (10% O ₂ content), and the NOx emission concentration can be controlled at 50mg/Nm ³ ( ₁₀ % O content).

The catalyst 33 has many small holes through which the exhaust gas passes. Because during cement production, there will be a lot of dust in the exhaust gas. If the exhaust gas is directly passed through the catalyst 33, the dust in the exhaust gas will accumulate on the surface of the catalyst due to the action of gravity, so that the pores on the catalyst are blocked, and the gas cannot be pass. Therefore, a ash cleaning device 34 is arranged above each layer of catalyst 33, and the ash cleaning device 34 can lift up the dust in the exhaust gas and pass through the small holes of the catalyst to prevent dust from accumulating on the surface of the catalyst.

The ash cleaning device 34 includes a rake-type ash cleaner, a motor, a push rod and a hanging rail. The rake-type ash cleaner is located above the catalyst, and the hanging rail is fixedly connected to the side wall of the SCR reaction tower 3. The ash cleaner is slidably connected to the hanging rail through a pulley, one end of the push rod is connected to the rake ash cleaner, the other end of the push rod is connected to the motor, and the motor rotates to drive the push rod to push the rake ash cleaner to slide on the hanging rail. The rake ash cleaner is a rake structure. There are many small holes on the rake. The rake is connected with the compressed air. When the rake ash cleaner slides back and forth on the hanging rail, the compressed air will lift up the dust, so that the dust follows the exhaust gas through the catalyst. , to avoid the accumulation of dust on the catalyst surface. The rake cleaner can run along the track according to the set program and frequency to ensure that the catalyst is not blocked.

The bottom of the SCR reaction tower 3 is provided with an outlet I35 for ash and an outlet II36 for gas outlet. The outlet II36 forms a U-shaped structure with the SCR reaction tower 3 through a pipeline. The outlet I35 is connected to the ash return conveying device 5, and the outlet II36 is connected to the power generation boiler 4. connect. The bottom of outlet I35 is provided with an ash return conveying device 5. The ash return conveying device 5 includes a chute 51, a conveyor belt 52 and a motor 53. The motor 53 is installed at both ends of the chute 51, and the conveyor belt 52 is arranged on the motor 53. Rotate in the groove. The gas outlet and the ash outlet are designed separately. The outlet II36 forms a U-shaped structure with the SCR reaction tower 3 through the pipeline, so that the gas outlet is higher than the ash outlet, so that the gas and dust can be separated, and the dust will come out from the outlet I35 and be transported through the ash return. The device is transported away, which purifies the gas from the outlet Ⅱ36 to a certain extent, and avoids the secondary pollution of the air caused by the dust.

The ammonia water conveying and spraying device 2 includes an ammonia water tanker 22 for providing ammonia water, a discharge pump 23, an ammonia water storage tank 24, and an ammonia water conveying pump 25. The ammonia water tanker 22 is connected to the discharge pump 23, and the discharge pump 23 is connected to the ammonia water storage tank 24. Connection, the unloading pump 23 transports the ammonia water of the ammonia water tanker 22 to the ammonia water storage tank 24 for storage, the ammonia water storage tank 24 is connected with the ammonia water delivery pump 25, and the ammonia water delivery pump 25 is connected with the injection port (21) for injecting the ammonia water through the pipeline. Connected, the ammonia water delivery pump 25 draws out the ammonia water in the ammonia water storage tank 24 and transports it to the injection port (21) through the pipeline for injection. At the same time, the ammonia water conveying and spraying device 2 also includes an air compressor II26 and an air storage tank II27. The air compressor II26 is connected with the air storage tank II27. The air compressor II26 compresses and stores the air in the air storage tank II27, and the air storage tank II27 passes through the air storage tank II27. The pipeline is connected with the injection port (21), and is sprayed at the injection port (21), the pipeline for transporting ammonia water is connected in parallel with the pipeline for transporting gas, and the gas is sprayed while the ammonia water is sprayed, and the purpose is to spray the ammonia water. Blow out to atomize ammonia water, and use force to heat with ammonia water to vaporize.

The ash cleaning device 34 includes a rake ash cleaner 341, an air compressor I342 and an air storage tank I343. The air compressor I342 is connected to the air storage tank I343. The air compressor I342 compresses and stores the air in the air storage tank I343. The tank I343 is connected with the rake type ash cleaner 341, and the gas storage tank I343 provides the air source for the rake type ash cleaner 341. After the gas produced by the air compressor I342 passes through the ash hopper of the SCR reaction tower 3, the gas temperature is heated to about 200 °C, and then enters the gas storage tank I343 for storage and standby. The gas in the gas storage tank I343 is connected to the rake ash cleaner 341. , to provide a blowing air source for the rake cleaner 341.

Based on the above-mentioned cement kiln SCR denitration system, the present invention also relates to a technological process of the cement kiln SCR denitration system, and the technological process is as follows:

a) The waste gas containing NOx enters the preheater 1 from the kiln end. After preheating by the preheater 1, the waste gas containing NOx at 300-400°C is introduced into the SCR reaction tower 3 from the outlet of the preheater 1 through the pipeline I11; at the same time, Ammonia water delivery and injection device 2 injects ammonia water to pipeline I11 to mix with NOx-containing exhaust gas;

b) Ammonia water is gasified into ammonia gas when encountering high temperature waste gas, and the gasified ammonia water is mixed with NOx-containing waste gas and then enters SCR reaction tower 3. Ammonia is a reducing agent. When the mixed gas passes through catalyst 33 in SCR reaction tower 3, The ash cleaning device 34 is always in the blowing state to lift the dust in the exhaust gas, and the NOx is reduced to N ₂ and H ₂ O through the catalytic action of the catalyst 33 to complete the denitrification; the temperature difference between the inlet and outlet of the SCR reaction tower 3 is controlled within 10 ℃; The ash device 34 sprays intermittently according to the set program to lift the dust in the exhaust gas;

c) The generated N ₂ and H ₂ O are in a high temperature state, the exhaust gas after denitrification enters the power generation boiler 4, uses the waste heat to generate electricity, and then enters the high temperature fan 6, and the exhaust gas after denitrification by the SCR reaction tower enters the next passage from the high temperature fan 6 process.

The catalyst material is generally V ₂ O ₅ -WO ₃ (MoO ₃ )/TiO ₂ . In the denitration reaction, the sources of ammonia gas include liquid ammonia, ammonia water and urea. :

4NO+4NH ₃ +O ₂ →4N ₂ +6H ₂ O

6NO ₂ +8NH ₃ →7N ₂ +12H ₂ O

The system was applied in a 5000t/d production line of Conch, and achieved good results. The inlet NOx of the SCR reaction tower was 800mg/Nm ³ (10% O ² content), the outlet NOx was 50mg/Nm ³ (10% O ² content), and the exhaust gas The air volume is 340,000Nm ³ /h, and the amount of 20% ammonia water is about 800L/h. The theoretically calculated ammonia-nitrogen reaction ratio is close to 1, and the ammonia escape is within 5mg/Nm ³ .

The present invention has been exemplarily described above with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods, as long as various insubstantial improvements made by the technical solutions of the present invention are adopted, or the If the concept and technical solutions are directly applied to other occasions, they all fall within the protection scope of the present invention.

Claims (10)

1. The utility model provides a cement kiln SCR deNOx systems which characterized in that: including pre-heater (1), aqueous ammonia is carried and injection apparatus (2), SCR reaction tower (3), power generation boiler (4), return grey conveyor (5) and high temperature fan (6), the export of pre-heater (1) passes through the entry linkage of pipeline I (11) and SCR reaction tower (3), injection jet (21) sealing connection of aqueous ammonia transport and injection apparatus (2) is on pipeline I (11), aqueous ammonia and waste gas mix and get into SCR reaction tower (3), an export and the ash conveyor (5) of returning of SCR reaction tower (3) are connected, another export and power generation boiler (4) of SCR reaction tower (3) are connected, the ash outlet (41) of power generation boiler (4) are connected with ash conveyor (5) of returning, the gas outlet (42) and the high temperature fan (6) of power generation boiler (4) are connected.

2. The cement kiln SCR denitration system of claim 1, wherein: the export of preheater (1) is connected with power boiler (4) through pipeline II (12), is equipped with valve II (14) on pipeline II (12), is equipped with valve I (13) on pipeline I (11), also is equipped with injection mouth (21) that are used for spraying the aqueous ammonia on the pipeline of preheater (1), and the aqueous ammonia passes through injection mouth (21) and sprays in preheater (1).

3. The cement kiln SCR denitration system of claim 1 or 2, wherein: be equipped with water conservancy diversion equipartition board (32) in SCR reaction tower (3), catalyst (33) and ash removal device (34), water conservancy diversion equipartition board (32) set up in the entry (31) department of reaction tower, water conservancy diversion equipartition board (32) are connected on the tower body of SCR reaction tower (3), catalyst (33) are connected and are located the below of water conservancy diversion equipartition board (32) on the tower body of SCR reaction tower (3), the top of catalyst (33) is equipped with ash removal device (34), ash removal device (34) are connected and are located the below of water conservancy diversion equipartition board (32) on the tower body of SCR reaction tower (3).

4. The cement kiln SCR denitration system of claim 3, wherein: the uniform flow guide distribution plate (32) is made of inverted angle steel, a gap is formed between every two adjacent angle steel, and air passes through the gap between every two adjacent angle steel.

5. The cement kiln SCR denitration system of claim 4, wherein: the SCR reaction tower (3) is internally provided with a plurality of layers of diversion uniform distribution plates (32), and the distance between two adjacent layers of diversion uniform distribution plates (2) is increased in sequence.

6. The cement kiln SCR denitration system of claim 5, wherein: the SCR reaction tower (3) is internally provided with a plurality of layers of catalysts (33), a dust cleaning device (34) is arranged above each layer of catalyst (33), gas enters the catalysts (33) through the dust cleaning device (34) to react, and the catalysts (33) are honeycomb catalysts or plate catalysts.

7. The cement kiln SCR denitration system of claim 6, wherein: the catalyst (33) is obliquely arranged or the longitudinal section of the catalyst (33) is of a triangular structure, the catalysts (33) among the layers are parallel to each other when the catalyst (33) is obliquely arranged, and when the longitudinal section of the catalyst (33) is of the triangular structure, two adjacent layers of triangular catalysts are oppositely arranged, namely the thickest part of the upper layer catalyst (33) corresponds to the thinnest part of the lower layer catalyst (33).

8. The cement kiln SCR denitration system of claim 7, wherein: the bottom of SCR reaction tower (3) is equipped with export I (35) that are used for going out the ash and export II (36) of giving vent to anger, and export II (36) constitute U type structure through pipeline and SCR reaction tower (3), and export I (35) is connected with ash conveyor (5) back, and export II (36) are connected with power generation boiler (4).

9. The cement kiln SCR denitration system of claim 8, wherein: the ash removal device (34) comprises a rake type ash removal device, a motor, a push rod and a hanging rail, wherein the hanging rail is fixedly connected to the side wall of the tower body of the SCR reaction tower (3), the rake type ash removal device is connected to the hanging rail through a pulley in a sliding mode, one end of the push rod is connected with the rake type ash removal device, the other end of the push rod is connected with the motor, and the motor rotates to drive the push rod to push the rake type ash removal device to slide on the hanging rail.

10. The process flow of the cement kiln SCR denitration system as set forth in any one of claims 1 to 9, wherein: the process flow comprises the following steps:

a) the waste gas containing NOx enters a preheater (1) from the kiln tail, after being preheated by the preheater (1), the waste gas containing NOx at the temperature of 300-400 ℃ is introduced into an SCR reaction tower (3) from the outlet of the preheater (1) through a pipeline I (11);

meanwhile, the ammonia water is sprayed to the pipeline I (11) by the ammonia water conveying and spraying device (2) and is mixed with the waste gas containing NOx;

b) the ammonia water is gasified into ammonia gas when meeting high-temperature waste gas, the gasified ammonia water and the waste gas containing NOx are mixed and then enter the SCR reaction tower (3), the ammonia gas is a reducing agent, when the mixed gas passes through a catalyst (33) in the SCR reaction tower (3), the ash cleaning device (34) is always in a blowing state to lift up dust in the waste gas, and the NOx is reduced into N through the catalytic action of the catalyst (33)₂And H₂O, completing denitration;

c) generated N₂And H₂O is in a high-temperature state, the denitrated waste gas enters a power generation boiler (4), power is generated by using waste heat, then the waste gas enters a high-temperature fan (6), and the waste gas denitrated by the SCR reaction tower is blown by high-temperature airThe machine (6) enters the next working procedure.

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