Circulating fluidized bed boiler

Abstract

The invention relates to the technical field of boilers, in particular to a circulating fluidized bed boiler, which is provided with an SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) combined device, the SNCR and SCR combined device comprises an SNCR device and an SCR device, the SNCR device comprises an ammonia water spray pipe arranged in an area with the temperature of 800 DEG C, ammonia water is sprayed into tail gas through the ammonia water spray pipe, the ammonia water is gasified and subjected to contact reaction with NOx, and the concentration of NOx at an outlet of a cyclone separator is controlled to be less than 40mg / Nm < 3 >. The SCR device comprises an SCR reactor arranged in an area of 320-420 DEG C, NOx and ammonia gas are subjected to catalytic reaction in the SCR reactor, the concentration of NOx is reduced to be smaller than 25 mg / Nm < 3 > under the action of a catalyst, the concentration of NOx after reaction is reduced to be 20 mg / Nm < 3 >, the content of NH3 in flue gas is 45 mg / Nm < 3 >, the NOx enters an ammonia-process desulfurization tower along with the flue gas and serves as supplement of a desulfurization agent for ammonia-process desulfurization, ammonia escape can be controlled to be smaller than 1 mg / Nm < 3 > after ammonia-process desulfurization, and the ammonia escape can be controlled to be smaller than 1 mg / Nm < 3 > after ammonia-process desulfurization. The environment-friendly emission standard is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler, in particular to a circulating fluidized bed boiler. BACKGROUND

[0002] The circulating fluidized bed boiler is mainly used in the scene with complex fuel source and strict environmental protection requirements, and heat transfer, mass transfer and chemical reaction are realized through the circulating flow of solid particles under the action of gas flow, so as to improve the combustion efficiency and reduce the generation of nitrogen oxides (NOx).

[0003] According to the local environmental protection standard, the emission concentration of nitrogen oxides in the boiler flue gas is required to be NOx≤25mg / Nm 3 (O2 content 6%). However, the original generation concentration of nitrogen oxides of the circulating fluidized bed boiler cannot meet the demand, and needs to be transformed to control the emission concentration of nitrogen oxides. At present, the main method of transformation is to carry out SCR denitration transformation. Since the boiler is designed and built earlier, the SCR catalyst bed height is not reserved during design, the existing flue distance is not enough, the flue gas needs to be led out of the flue, and the SCR reactor bed is external. The external SCR bed increases the resistance of the flue by about 800Pa, which greatly affects the load of the primary and secondary air fans, and about 10% of the boiler load is affected, the heat loss increases by 5%, and the boiler efficiency is greatly reduced. At the same time, due to the compact original layout of the boiler, there are characteristics of great construction difficulty, long construction period and high engineering cost. The transformation price of a single 130t / h boiler is 8 million yuan. According to the case after transformation, it is difficult to improve the load of the boiler after transformation, and the wear is aggravated. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a circulating fluidized bed boiler.

[0005] The present application is realized by the following technical scheme: a circulating fluidized bed boiler, comprising a hearth, the hearth is connected with a fuel supply device, a combustion air device, a fluidization separation device and a tail gas treatment device, The hearth is vertically arranged, and the lower end of the hearth is provided with a bed surface; The fuel supply device comprises a coal bunker, and the coal bunker is connected to the bottom of the hearth through a coal feeder; The combustion air device comprises a primary air device, the primary air device comprises a primary air fan, and the air outlet of the primary air fan enters the lower end of the hearth; The fluidization separation device comprises a cyclone separator, and the lower end of the cyclone separator is connected to the bottom of the hearth through a backflow pipe; The tail gas treatment device comprises a flue, a dust remover and a chimney arranged in sequence, the flue is communicated with the air outlet of the cyclone separator, a superheater, a coal economizer and an air preheater are arranged in the flue from top to bottom in sequence, the air outlet of the primary air fan enters the lower end of the furnace after passing through the air preheater, Further, the SNCR and SCR combined device comprises an SNCR device and an SCR device, the SNCR device comprises an ammonia water nozzle arranged in a region with a temperature of 800 DEG C, ammonia water is sprayed into the tail gas through the ammonia water nozzle, the ammonia water is gasified and reacts with NOx, the SCR device comprises an SCR reactor arranged in a region with a temperature of 320-420 DEG C, NOx and ammonia gas are catalytically reacted in the SCR reactor.

[0006] Further, the upper end of the cyclone separator is communicated with the upper end of the furnace through an air outlet pipe one, the ammonia water nozzle is arranged on a main pipe of the air outlet pipe one, the main pipe is connected with an ammonia water inlet pipe and a compressed air inlet pipe, ammonia water is sprayed out through the compressed air, a cooling air inlet pipe is further connected on the main pipe, the main pipe penetrates through the side wall of the air outlet pipe one and is connected with a plurality of branch pipes, the branch pipes are distributed around the inner wall of the air outlet pipe one, and a nozzle is processed on the branch pipe, so as to spray ammonia water into the air outlet pipe one.

[0007] Further, the coal economizer has two groups, which are a first group of coal economizers and a second group of coal economizers from top to bottom in sequence, and the SCR reactor is arranged between the first group of coal economizers and the second group of coal economizers.

[0008] Further, the air preheater comprises an upper layer air preheater and a lower layer air preheater distributed in the flue from top to bottom, the air outlet of the primary air fan enters the lower end of the furnace after passing through the lower layer air preheater, and the air outlet of the secondary air fan enters the lower end of the furnace after passing through the upper layer air preheater, and the air inlet of the secondary air is higher than the air inlet of the primary air on the furnace.

[0009] Further, the lower end of the furnace is provided with an upper secondary air inlet and a lower secondary air inlet, the lower secondary air inlet is arranged in a region with a height of 4m above the bed surface, and the front and rear walls are opposite to each other, and is located at the joint of the dense phase region and the dilute phase region, the upper secondary air inlet is arranged in a region with a height of 4.5m above the bed surface, and the front and rear walls are opposite to each other, and is used for supplying the main air volume in the burnout stage, and the upper secondary air inlet and the lower secondary air inlet are arranged in the form of horizontal multiple holes along the width of the furnace wall.

[0010] Further, the lower end of the cyclone separator is further connected with a fluidization air fan.

[0011] Further, the lower end of the cyclone separator is provided with a circulating ash collecting device, which comprises a collecting bin arranged at the lower end of the cyclone separator, and a reflux outlet is arranged at the upper end of the collecting bin and communicated with the feeding end of a reflux pipe, so that the filling particles are ejected upwardly from the collecting bin by the airflow of the fluidizing fan, and the filling particles with large weight are intercepted.

[0012] Further, the air outlet of the primary air fan is connected to the outlet of the coal feeder.

[0013] The present application has the advantages that: the SNCR and SCR combined device is arranged, which comprises an SNCR device and an SCR device, the SNCR device comprises an ammonia water spray pipe arranged in a region with a temperature of 800℃, ammonia water is sprayed into the tail gas through the ammonia water spray pipe, the ammonia water is gasified and reacts with NOx, the NOx concentration at the outlet of the cyclone separator is controlled to be less than 40mg / Nm 3 , the SCR device comprises an SCR reactor arranged in a region with a temperature of 320-420℃, the NOx and ammonia gas are catalytically reacted in the SCR reactor, the NOx concentration is reduced to be less than 25mg / Nm 3 , the NOx concentration after the reaction is reduced to be less than 20mg / Nm 3 , the NH3 content in the flue gas is 45mg / Nm 3 , the flue gas enters the ammonia desulfurization tower, the ammonia escapes is controlled to be less than 1mg / Nm 3 after the ammonia desulfurization, and the environmental protection emission standard is met. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a schematic diagram of the connection relationship of each device in Example 1; Figure 2 It is a sectional view schematic diagram of the connection between the ammonia water spray pipe and the air outlet pipe; Figure 3 It is a top view schematic diagram of the connection between the ammonia water spray pipe and the air outlet pipe; Figure 4 It is a schematic diagram of the connection relationship between the SCR reactor and the flue; Figure 5 It is a schematic diagram of the distribution of the secondary air outlet; Figure 6 It is a left view schematic diagram of the distribution of the secondary air outlet; Figure 7 It is a top view schematic diagram of the SCR reactor.

[0015] 1, furnace; 2, ash valve three; 3, bed surface; 4, coal bunker; 5, coal feeder; 6, cyclone separator; 7, ammonia water spray pipe; 701, main pipe; 702, ammonia water inlet pipe; 703, compressed air inlet pipe; 704, cooling air inlet pipe; 705, manifold 8. Collection bin; 9. Return pipe; 10. Ash discharge valve II; 11. Flue; 12. Superheater; 13. First economizer group; 14. SCR reactor; 15. Second economizer group; 16. Fluidizing blower; 17. Upper air preheater; 18. Lower air preheater; 19. Ash discharge valve I; 20. Primary air fan; 21. Secondary air fan; 22. Dust collector; 23. Ash discharge valve IV; 24. Exhaust fan; 25. Chimney; 26. Air outlet duct I; 27. Lower secondary air outlet; 28. Upper secondary air outlet. Detailed Implementation

[0016] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 like Figures 1-7 As shown, a circulating fluidized bed boiler includes a furnace 1, which is connected to a fuel supply device. The fuel supply device includes a coal bunker 4, which is connected to the bottom of the furnace 1 via a coal feeder 5. An ash discharge valve 2 is connected to the bottom of the furnace for easy cleaning.

[0019] The upper end of the furnace 1 is connected with a fluidized separation device, which comprises a cyclone 6, the upper end of the cyclone 6 is communicated with the upper end of the furnace 1 through an air outlet pipe 1, the lower end of the cyclone 6 is connected to the bottom of the furnace 1 through a backflow pipe 9, so as to make the filled particles backflow, the lower end of the cyclone 6 is also connected with a fluidizing fan 16, so as to accelerate the flow of the filled particles, the lower end of the cyclone 6 is also provided with a circulating ash collecting device, which comprises a collecting bin 8 installed at the lower end of the cyclone 6, the upper end of the collecting bin 8 is processed with a backflow outlet, the backflow outlet is communicated with the feeding end of the backflow pipe 9, the filled particles are sprayed out of the collecting bin 8 upward by the airflow of the fluidizing fan 16, the filled particles with larger weight are intercepted, so as to ensure that the filled particles have smaller weight and can circulate with the airflow, the bottom of the collecting bin 8 is also provided with an ash valve 1, which can discharge the intercepted filled particles regularly.

[0020] The upper end of the cyclone 6 is connected with a flue 11, the combustion tail gas flows from top to bottom in the flue 11, a convection superheater 12, an economizer and an air preheater are sequentially installed in the flue 11 from top to bottom, the convection superheater 12 has three groups, the economizer has two groups, the air preheater is divided into an upper air preheater 17 and a lower air preheater 18, the bottom of the flue 11 is provided with an ash valve 2 10.

[0021] The lower air preheater 18 is connected with a primary air device, which comprises a primary air fan 20. The air outlet of the primary air fan 20 enters the lower end of the furnace 1 after passing through the lower air preheater 18 and is blown upward from the lower side of the bed surface 3. The upper air preheater 17 is connected with a secondary air device, which comprises a secondary air fan 21. The air outlet of the secondary air fan 21 enters the lower end of the furnace 1 after passing through the upper air preheater 17. In the furnace 1, the air inlet of the secondary air is higher than that of the primary air. In the present embodiment, in order to improve the effect of the secondary air, an upper secondary air inlet 28 and a lower secondary air inlet 27 are processed at the lower end of the furnace 1. The lower secondary air inlet 27 is arranged at the area with a height of 34 m of the bed surface 34 and is opposite to the front and rear walls, which is the combination point of the dense phase zone and the dilute phase zone. The upper secondary air inlet 28 is arranged at the area with a height of 34.5 m of the bed surface 34.5 and is opposite to the front and rear walls, which is the main air supply amount in the burnout stage. The upper secondary air inlet and the lower secondary air inlet 27 are both arranged in the form of horizontal multiple holes along the width of the furnace wall, with a small nozzle with a diameter of Φ150 mm. The secondary air is raised to a very high speed, so that the secondary air has a strong penetration ability and is fully mixed with the high-temperature flue gas, balances the regional temperature field, controls the combustion zone temperature, effectively inhibits the generation of NOx, and through the staged combustion of the upper and lower secondary air, three combustion zones with strong reduction, weak reduction and oxidation are formed in the height direction of the furnace 1. At the same time, the combustion intensity of the dense phase zone of the furnace 1 is significantly slowed down, the combustion temperature of the dense phase zone of the furnace 1 is controlled, the uniformity of the overall temperature distribution of the furnace 1 is improved, the generation of temperature-type nitrogen oxides is inhibited, the generation of fuel-type nitrogen oxides is greatly reduced, the flow of the primary air and the secondary air is adjusted to realize staged combustion, the content of nitrogen oxides is reduced from the source, the NOx concentration at the outlet of the furnace 1 is reduced from the original 300 mg / Nm³ to about 150 mg / Nm³. 3 -400 mg / Nm³, to about 150 mg / Nm³.

[0022] The air outlet of the primary air fan 20 is also connected to the outlet of the coal feeder 5, so as to stabilize the feeding of the coal feeder 5.

[0023] The bottom of the flue 11 is connected to the dust collector 22 through the air outlet pipe two. The bottom of the dust collector 22 is connected to the ash valve four 23 to discharge the collected dust. The air outlet end of the dust collector 22 is connected to the chimney 25 through the air outlet pipe three with the induced draft fan 24. An ammonia desulfurization tower is installed between the air outlet pipe three and the chimney 25 to desulfurize after denitrification and reduce pollution emissions.

[0024] In the embodiment, the SNCR and SCR combined device comprises an SNCR device, the SNCR device comprises an ammonia water spray pipe 7 installed on the air outlet pipe one 26, the ammonia water spray pipe 7 comprises a main pipe 701, the main pipe 701 is connected with an ammonia water inlet pipe 702 and a compressed air inlet pipe 703, ammonia water is sprayed by compressed air, a cooling air inlet pipe 704 is further connected on the main pipe 701, a cooling cavity is sleeved outside the main pipe 701, the cooling air inlet pipe 704 is communicated to the cooling cavity, and then the main pipe 701 is cooled, the service life of the main pipe 701 is improved, the main pipe 701 penetrates through the side wall of the air outlet pipe one 26 inwardly and is connected with a plurality of manifolds 705, the manifolds 705 are distributed around the inner wall of the air outlet pipe one 26, a spray port is processed on the manifold 705, and then ammonia water is sprayed into the air outlet pipe one 26, the temperature at the air outlet pipe one 26 is controlled to be 800 DEG C by controlling the air volume of the primary air and the secondary air, ammonia water is uniformly mixed with flue gas at high temperature and reacts with NOx, and the NOx concentration at the outlet of the cyclone separator 6 is controlled to be reduced to <40 mg / Nm 3 .

[0025] The SNCR and SCR combined device further comprises an SCR device, the economizer has two groups, and the economizers are sequentially arranged from top to bottom as a first group of economizers 13 and a second group of economizers 15. The height of the first group of economizers 13 is 710 mm, and the height of the second group of economizers 15 is 1600 mm. The height of the second group of economizers 15 is equivalent to the height of two first group of economizers 13. Compared with two separate economizers, the total height is increased, the heat exchange effect is not weakened, but the resistance value of the gas flow is reduced by 120 Pa. The SCR device comprises an SCR reactor 14 installed between the first group of economizers 13 and the second group of economizers 15. The height of the SCR reactor 14 is 1700 mm. The distance between the SCR reactor 14 and the first group of economizers 13 is 827 mm. The distance between the SCR reactor 14 and the second group of economizers 15 is 827 mm. The inlet temperature of the first group of economizers 13 is controlled to be 540 ℃, the outlet temperature of the first group of economizers 13 is controlled to be 420 ℃, the outlet temperature of the second group of economizers 15 is controlled to be 230 ℃, and the tail flue 11 of the boiler is utilized, with a cross section of 4.4×7m (boiler flue 11 size), the SCR reactor 14 is supported on the boiler steel frame, the SCR reactor 14, the design of the SCR catalyst adopts a honeycomb structure, and the resistance of the SCR reactor 14 is less than 350 Pa, so that the boiler system can still operate stably without increasing the power of the boiler system fan, when the system is running, the flue gas flows through the reactor after being uniformly mixed with ammonia, and in the reactor, the reducing agent (ammonia) reacts with NOx in the flue gas under the action of the catalyst to generate harmless nitrogen and water, thereby removing NOx in the flue gas, the SCR reactor 14 is arranged according to one layer of catalyst, the catalyst adopts a honeycomb type, the flue gas of the SCR reactor 14 flows from top to bottom, and a flow guide plate is installed before the catalyst bed to ensure that the flue gas passes through the catalyst vertically at a uniform speed, the design of the SCR reactor 14 fully considers the coordination and aesthetics of the surrounding equipment arrangement, the SCR reactor 14 is designed to have flue gas flowing vertically downward, thereby reducing wear, the design pressure and instantaneous non-deformation bearing pressure of the SCR reactor 14 are the same as the design parameters of the furnace 1, the shell and the inner catalyst support structure should be made of Q355 steel according to the operating temperature requirement, the number of catalyst modules per layer 12 (arranged in 3×4) is determined by designing the reactor and the inlet flue 11, the sealing strip between the SCR reactor and the flue 11 is sealed to prevent short circuiting of the flue gas, so that the inlet flue gas of the catalyst in the SCR reactor reaches: the standard deviation of the flue gas flow rate is ≤±15% of the average value; the standard deviation of the flue gas temperature is ≤±10% of the average value; the maximum deviation of the ammonia nitrogen molar ratio is ≤±5% of the average value; the flue gas incidence angle (angle with the vertical direction) is ≤±15°, the conversion efficiency of ammonia and nitrogen oxide without catalyst at 800℃ is only about 40%, at this time, the flue gas contains excess ammonia, at this time, the excess ammonia is gaseous at high temperature (420-800℃), and the excess ammonia does not corrode the flue 11 much, after passing through the first group of economizers 13, the flue gas is mixed more uniformly with the unreacted ammonia, the temperature is controlled to 420℃ to enter the SCR reactor 14, and under the action of the catalyst, the NOx concentration is reduced to <25 mg / Nm. 3 , the NOx concentration after reaction is reduced to 20 mg / Nm 3 , the NH3 content in the flue gas is 45 mg / Nm 3 , the flue gas enters the ammonia desulfurization tower, serves as a supplement to the desulfurizer of the ammonia desulfurization method, and after the ammonia desulfurization, the ammonia escape can be controlled to be less than 1 mg / Nm 3 , meeting the environmental protection emission standard; at the same time, the resistance of the boiler flue 11 is increased by <200 Pa, and the load of the boiler primary fan 20, the secondary air fan, and the induced draft fan 24 is not affected (the increase in load is small within the fan margin), which has no effect on the boiler load; the length of the flue 11 is not increased, and the thermal efficiency of the boiler is not lost.

[0026] Taking the flue gas flow of 350000 Nm 3 / h as an example, the test results are shown in Table 1.

[0027]

[0028] The circulating fluidized bed boiler provided by the embodiment has the following operation steps, 1. Check the SCR reactor and the catalyst layer comprehensively to ensure that the catalyst is not damaged or blocked and that the reactor is free of sundries; 2. Check the ammonia water storage tank, the delivery system and the SNCR injection system of the SNCR to confirm that the pipeline connection is firm, there is no leakage, the valve opening and closing state is correct, the ammonia water delivery pump is in normal operation, and the plant air pressure is qualified (≈0.45 MPa); 3. Check the CEMS (continuous emission monitoring system) and the ammonia escape monitoring equipment to ensure that they are in normal working condition and the data monitoring is accurate; 4. Start the reducing agent storage and delivery system, Check the liquid level of the ammonia water storage tank <1 meter, start the denitration ammonia water delivery pump, adjust the delivery flow according to the process requirements, and ensure that the reducing agent can be stably supplied to the SCR denitration ammonia injection system; 5. Start the SCR denitration ammonia injection system, Put into the SNCR injection system, slowly open the ammonia injection valve, gradually adjust the ammonia injection amount, and at the same time detect the change of NOx and ammonia escape data to ensure that the ammonia injection amount is in a reasonable range and avoid excessive or insufficient ammonia; 6. Real-time parameter monitoring, During the system operation, the CEMS and the ammonia escape monitoring equipment are used to monitor the key parameters such as flue gas NOx, SO2, ammonia escape amount and SCR reactor flue gas resistance in real time, and the data is recorded once an hour; 7. Parameter adjustment strategy, Denitration efficiency adjustment: if the denitration efficiency is less than 60% (NOx>25 mg / Nm³), the ammonia injection amount can be appropriately increased under the condition that the ammonia escape is not over-standard; if the denitration efficiency is still not up to standard after increasing the ammonia injection amount, the catalyst activity needs to be checked, and if necessary, professional personnel are contacted for detection and treatment; Ammonia escape control: when the ammonia escape rate approaches 1 mg / Nm³, the desulfurization ammonia water addition amount and the denitration ammonia injection amount are immediately reduced, the reasons are analyzed, and corresponding measures are taken to solve the problem; Flue gas resistance management: if the catalyst flue gas resistance of the SCR reactor exceeds 350 Pa, first confirm that the soot blower system is in normal operation, then reduce the soot blower layer blowing interval time and increase the blowing time, and if necessary, the boiler operation load can be reduced; if the resistance is still too high after taking measures, it is necessary to evaluate whether the catalyst needs to be replaced during the opportunity maintenance.

[0029] System shutdown operation 1. After receiving the shutdown instruction, gradually reduce the amount of ammonia injection, while closely monitoring the denitration efficiency and ammonia escape rate changes, until the ammonia injection valve is completely closed.

[0030] 2. Close the SNCR denitration ammonia injection system ammonia water valve, atomizing valve, and stop the ammonia water drainage pump in sequence.

[0031] 3. After shutdown, conduct a comprehensive inspection of the SCR catalyst layer, ammonia injection system and other equipment, clean up dust and debris, and repair or replace worn or damaged parts in a timely manner to prepare for the next start-up.

[0032] It is worth noting that the circulating fluidized bed boiler provided in the embodiment is transformed on the original equipment, saving costs and achieving the following effects: 1. The construction difficulty of significantly reducing the compact arrangement of the boiler device can be solved, reducing the civil engineering cost, construction cost and equipment investment, and the cost of about 5 million yuan per unit is reduced compared with the external SCR reactor transformation of 8 million yuan per unit.

[0033] 2. The construction period of the transformation method can be reduced by 40 days compared with the construction period of the external SCR reactor.

[0034] 3. After the external SCR reactor transformation, the boiler resistance increases by 800 Pa, affecting the boiler load. If you want to ensure the boiler load, you need to replace the booster fan, primary air fan and secondary air fan, and increase the boiler power consumption by about 10%. After the transformation method of the embodiment is implemented, the boiler resistance increase value is less than 200 Pa, which has a lower impact on the boiler primary air fan, secondary air fan and induced draft fan, and the boiler load can be guaranteed after transformation.

[0035] 4. After the external SCR reactor transformation, the boiler heat loss increases by about 5%. After the transformation method of the embodiment is implemented, the boiler body has not changed significantly, and the boiler heat loss has not increased.

[0036] 5. After the external SCR reactor transformation, the boiler internal flow field changes, the local wear of the boiler intensifies, and the probability of unexpected shutdown of the boiler increases. After the transformation method of the embodiment is implemented, the boiler flow field has not changed significantly, and the boiler wear has no effect.

[0037] 6. The circulating fluidized bed boiler provided in the embodiment is obtained by quickly transforming the existing boiler, has great popularization value, and has good social value and economic value.

[0038] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A circulating fluidized bed boiler, comprising a furnace, a fuel supply device, a combustion air supply device, a fluidization separation device and a tail gas treatment device, the furnace is vertically arranged, and a bed surface is arranged at a lower end of the furnace; the fuel supply device comprises a coal bunker connected to a bottom of the furnace through a coal feeder; the combustion air supply device comprises a primary air supply device, which comprises a primary air blower, and the air outlet of the primary air blower enters the lower end of the furnace; the fluidization separation device comprises a cyclone separator, and a lower end of the cyclone separator is connected to the bottom of the furnace through a backflow pipe; the tail gas treatment device comprises a flue, a dust collector and a chimney arranged in sequence, the flue is communicated with an air outlet of the cyclone separator, and a superheater, an economizer and an air preheater are arranged in the flue from top to bottom in sequence, and the air outlet of the primary air blower enters the lower end of the furnace after passing through the air preheater, characterized in that and further comprising a SNCR and SCR combined device, the SNCR and SCR combined device comprises a SNCR device and a SCR device, the SNCR device comprises an ammonia water nozzle arranged in a region with a temperature of 800℃, ammonia water is sprayed into tail gas through the ammonia water nozzle, the ammonia water is gasified and reacts with NOx, and the SCR device comprises a SCR reactor arranged in a region with a temperature of 320-420℃, and NOx and ammonia gas catalytically react in the SCR reactor.

2. A circulating fluidized bed boiler according to claim 1, characterized in that an upper end of the cyclone separator is communicated with an upper end of the furnace through an air outlet pipe one, the ammonia water nozzle is arranged on a main pipe of the air outlet pipe one, the main pipe is connected with an ammonia water inlet pipe and a compressed air inlet pipe, ammonia water is sprayed out through compressed air, a cooling air inlet pipe is further connected on the main pipe, the main pipe penetrates through a side wall of the air outlet pipe one inwardly and is connected with a plurality of branch pipes, the branch pipes are distributed around an inner wall of the air outlet pipe one, and a nozzle is arranged on the branch pipe, so that ammonia water is sprayed into the air outlet pipe one.

3. A circulating fluidized bed boiler according to claim 1, characterized in that the economizer has two groups, which are a first group of economizers and a second group of economizers arranged in sequence from top to bottom, and the SCR reactor is arranged between the first group of economizers and the second group of economizers.

4. A circulating fluidized bed boiler according to claim 1, characterized in that the air preheater comprises an upper air preheater and a lower air preheater arranged in the flue from top to bottom in sequence, the air outlet of the primary air blower enters the lower end of the furnace after passing through the lower air preheater, and further comprising a secondary air supply device, the air outlet of a secondary air blower enters the lower end of the furnace after passing through the upper air preheater, and on the furnace, an air inlet of the secondary air is higher than an air inlet of the primary air.

5. A circulating fluidized bed boiler according to claim 4, characterized in that the lower end of the furnace is provided with an upper secondary air inlet and a lower secondary air inlet, the lower secondary air inlet is arranged at a region 4m high from the bed surface, and is arranged in a front-to-back wall collision mode at a joint of a dense phase region and a dilute phase region, the upper secondary air inlet is arranged at a region 4.5m high from the bed surface, and is arranged in a front-to-back wall collision mode, and is used for mainly supplying air volume in a burnout stage, and the upper secondary air inlet and the lower secondary air inlet are arranged in a horizontal multi-hole arrangement mode along a width of a furnace wall.

6. A circulating fluidized bed boiler according to claim 1, characterized in that a fluidization air blower is further connected to the lower end of the cyclone separator.

7. A circulating fluidized bed boiler according to claim 1, characterized in that The lower end of the cyclone separator also has a circulating ash collecting device, which comprises a collecting bin arranged at the lower end of the cyclone separator, and a reflux outlet is formed at the upper end of the collecting bin and communicates with the feeding end of a reflux pipe.

8. A circulating fluidized bed boiler according to claim 1, characterized in that The air outlet of the primary air fan is also connected to the outlet of the coal feeder.

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