Efficient SCR denitration device and denitration method of gas turbine unit

Abstract

The invention discloses an efficient SCR (Selective Catalytic Reduction) denitration device of a gas turbine unit and a denitration method. The device comprises a flow velocity measuring device, an ammonia water spraying device, a flue gas rectifying device and a catalyst layer, the flow velocity measuring device and the ammonia water spraying device are sequentially arranged at the upstream of the flue gas pipeline, probes of the flow velocity measuring device and nozzles of the ammonia water spraying device are uniformly distributed on different cross sections in the flue gas pipeline, and the probes and the nozzles are matched in number and position; the flue gas rectifying device is arranged in the middle and downstream of the flue gas pipeline and in front of the multi-stage heat exchanger, and the spiral flow of flue gas is converted into linear uniform flow along the flue gas channel; the catalyst layer is arranged in the flue gas pipeline and located between the multiple stages of heat exchangers. According to the characteristic that flue gas discharged by the gas turbine spirally flows, the ammonia water injection amount is adjusted through multi-point flow velocity measurement, spiral flowing is converted into linear flowing through the flue gas rectifying device, the uniformity degree of mixed gas is improved, full catalysis is achieved, and then efficient denitration is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of exhaust gas pollution control, and in particular relates to a high-efficiency SCR denitration device and a denitration method for a gas turbine unit. Background Art

[0002] As the global requirements for pollutant emissions increase, the requirements for tail gas emissions from gas turbine units are also increasing. At the same time, unlike the widely used SCR (selective catalytic reduction) denitrification technology for coal-fired boilers in power plants, the renovation of gas turbine units covers a limited area, and the SCR denitrification reactor is arranged in a small space. It is generally arranged in the middle of the heat exchanger, which not only needs to ensure the uniformity of the mixing of ammonia and flue gas, but also needs to take into account the waste heat utilization efficiency of the boiler.

[0003] At present, most of the SCR denitrification technologies for gas turbine units use the SCR denitrification technology of producing ammonia by pyrolysis of urea. Ammonia is produced outside the flue, evenly sprayed into the flue through an ammonia spray grid, and then directly enters the boiler heat exchange and SCR denitrification section. In this method, the urea pyrolysis system occupies a large area, has high maintenance costs, the ammonia flue gas mixing is not uniform enough, and the denitrification efficiency is low, which can no longer meet actual needs.

[0004] Chinese invention patent CN110508132A discloses a denitrification system and a denitrification method for SCR high-efficiency denitrification of a gas turbine unit. The method uses urea to directly pyrolyze in the flue and then spray it into the flue. The flue gas is then rectified by a special derotator to save space in the pyrolysis device and utilize waste heat to ensure the uniformity of the mixing of the flue gas and ammonia required for denitrification.

[0005] By comparing the above patents and other prior arts, it can be found that the prior arts generally assume that the flue gas flow is uniform before ammonia injection, so a uniform ammonia injection structure is adopted to meet the flue gas uniformity requirements. However, in fact, the exhaust gas discharged by the gas turbine flows in a spiral shape in the flue gas duct, and will show the characteristics of large flow velocity around and low flow velocity in the middle. Therefore, the assumption of flue gas uniformity is not in line with engineering reality, and whether the measure of uniform ammonia injection can meet the needs of flue gas pyrolysis remains to be further discussed. Different derotators (rectifiers) structures are proposed in Chinese invention patents CN110508132A and CN117463150A, but the derotators (rectifiers) are basically arranged uniformly and can only play a role in local rectification, which can realize the conversion of the spiral motion of the flue gas into linear motion along the flue gas channel, but cannot change the objective situation that the flow velocity around the existing exhaust gas is high and the flow velocity in the middle is low. At the same time, other derotators used in the prior art are complex in structure, and the manufacturing difficulty, economy and maintenance costs are relatively large, which is not conducive to large-scale promotion and application. Summary of the invention

[0006] In view of the above shortcomings, the present invention proposes a high-efficiency SCR denitrification device and denitrification method for a gas turbine unit, which adopts an ammonia water injection method to eliminate the complicated ammonia production equipment, and cooperates with flow velocity measurement to improve the uniformity of ammonia concentration; a flue gas rectification device is used to convert the spiral exhaust gas with high flow velocity around and low flow velocity in the middle into a straight and uniform flow along the flue gas channel, thereby improving the uniformity of the mixing of flue gas and ammonia, thereby improving the denitrification efficiency.

[0007] To achieve the above object, the present invention adopts the following technical solution: The present invention provides a high-efficiency SCR denitration device for a gas turbine unit, comprising a flue gas duct, a multi-stage heat exchanger, and a catalyst layer; the upstream end of the flue gas duct is connected to the flue gas outlet pipe of the gas turbine unit, and the downstream end is connected to the chimney; the multi-stage heat exchanger and the catalyst layer are arranged inside the downstream of the flue gas duct; It also includes a flow rate measuring device and an ammonia water injection device; The flow rate measuring device and the ammonia water injection device are sequentially arranged upstream of the flue gas duct, and the probe of the flow rate measuring device and the nozzle of the ammonia water injection device are evenly distributed on two different cross sections in the flue gas duct.

[0008] Furthermore, the number and position of the flow rate measuring device probe and the ammonia water injection device nozzle match.

[0009] Furthermore, the flow velocity measuring device includes a first flow velocity measuring instrument and multiple second flow velocity measuring instruments, the probe of the first flow velocity measuring instrument is located on the axis of the flue gas duct; the probes of the multiple second flow velocity measuring instruments are evenly distributed in the flue gas duct along the circumferential direction, the circle where the probes of the multiple second flow velocity measuring instruments are located is concentric with the flue gas channel, and the insertion depth of the probes in the flue gas duct is adjustable; the number of the second flow velocity measuring instruments is not less than 6, preferably 8-15.

[0010] Furthermore, the ammonia injection device includes a first spray gun and multiple second spray guns, the nozzle of the first spray gun is located on the axis of the flue gas duct; the nozzles of the multiple second spray guns are evenly distributed in the flue gas duct along the circumferential direction, and the radius of the circle where the nozzles are located is the same as the radius of the circle where the second flow rate measuring instrument probe is located; the first spray gun and the second spray gun both use dual-fluid spray guns, and both use reverse injection (that is, the injection direction is opposite to the flue gas flow direction), which is conducive to the evaporation of ammonia water and the mixing of ammonia water and flue gas; the distance between the flow rate measuring device and the ammonia injection device is greater than or equal to 400 mm, preferably 400 mm.

[0011] Furthermore, it also includes an ammonia injection controller, the input end of the ammonia injection controller is respectively connected to the first flow rate measuring meter and each second flow rate measuring meter, and the output end is respectively connected to the first spray gun and each second spray gun, and the ammonia injection controller adjusts the injection amount of the corresponding spray gun according to the measurement results of the flow rate measuring meter.

[0012] Furthermore, it also includes a flue gas straightening device, which is arranged inside the middle and downstream of the flue gas duct and before the multi-stage heat exchanger to convert the spiral flow of the flue gas into a straight and uniform flow along the flue gas channel.

[0013] Furthermore, the flue gas rectifying device includes a rectifying orifice plate and a rectifying grid plate, wherein the rectifying grid plate is fixed on the back of the rectifying orifice plate; the rectifying orifice plate relatively reduces the smoke resistance while ensuring the uniformity of the outlet smoke flow field; the rectifying grid plate further adjusts the direction of the smoke after passing through the rectifying orifice plate and strengthens the structure of the rectifying orifice plate.

[0014] Furthermore, the rectifying orifice plate is provided with a plurality of through holes along the thickness direction, with a small opening rate on the four sides and a large opening rate in the middle, a large opening rate on the upper part and a small opening rate on the lower part, and a total opening rate of 30%-90%; the through hole diameter is preferably 50-100mm.

[0015] Furthermore, the flue gas straightening device is arranged inside the downstream of the flue gas duct and is perpendicular to the axis of the flue gas duct.

[0016] Furthermore, the catalyst layer is located between the multi-stage heat exchangers, and the temperature of the catalyst layer is 360°C-420°C, which meets the temperature requirements of the catalyst reactor and provides mixing time for ammonia and flue gas; the catalyst layer can adopt a honeycomb structure or a corrugated plate structure.

[0017] The present invention provides a high-efficiency SCR denitration method for a gas turbine unit, comprising the following steps: The flow velocity measuring device measures the flow velocity of the flue gas flowing forward spirally at different positions in a cross section upstream of the flue gas duct; The spray gun in the ammonia water spraying device sprays different amounts of ammonia water to corresponding positions in another cross section upstream of the flue gas duct according to the flow velocity at different positions. The ammonia water is heated and gasified into ammonia gas during the mixing process with the flue gas, thereby obtaining a mixed gas of flue gas and ammonia gas. The ammonia concentration of the mixed gas at different positions in the same cross section is close. After the ammonia water is completely gasified, the mixed gas of flue gas and ammonia flows through the flue gas rectifying device for rectification, so that the spiral forward flow is rectified into a straight flow, and the flue gas and ammonia are further mixed, so that the ammonia concentration of the mixed gas at different positions in the same cross section is further close; The mixed gas of flue gas and ammonia flows through several stages of heat exchangers before the catalyst layer in the multi-stage heat exchanger, and the mixed gas is further rectified and mixed so that the velocity, velocity deflection angle and ammonia concentration of the mixed gas at different positions in the same cross-section meet the design requirements, and then flows into the catalyst layer for catalytic denitrification; finally, it flows through the latter stages of the multi-stage heat exchanger until it is discharged.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1) Accurately adjust the amount of ammonia sprayed: The use of a front flow velocity measurement device is conducive to understanding the distribution characteristics of the flue gas discharged from the gas turbine unit in the upstream of the flue gas duct, providing a prerequisite for accurate injection of ammonia water; then, according to the requirements of the ammonia-nitrogen molar ratio, more ammonia water is sprayed in areas with larger flue gas volumes, and less or even no ammonia is sprayed in areas with smaller flue gas volumes. The position, quantity and flow rate of the spray gun are accurately adjusted to maintain the ammonia-nitrogen molar ratio within a controllable range, which is conducive to uniform mixing of flue gas and ammonia.

[0019] 2) Low system resistance: The direct injection of ammonia water combined with the rectification of the orifice plate and the grid plate reduces the resistance caused by the urea pyrolysis device, the ammonia injection grid pipeline and the complex deracination device, and the increase in the resistance of the entire system is relatively small.

[0020] 3) Simple structure and low cost: This patent adopts the method of direct injection of ammonia water, eliminating the existing complex urea pyrolysis system, ammonia injection grid and subsequent complex de-racination rectification device, and only adopts multi-point ammonia water injection + rectification orifice plate, rectification grid plate combination, which has a simple structure, saves external space, is more economical, and is conducive to promotion and application.

[0021] 4) Improve heat exchange and denitrification efficiency: This patent measures the distribution of the incoming flue gas flow velocity, accurately controls the amount of ammonia water injection, obtains a relatively uniform mixture of ammonia and flue gas, and then adjusts the overall deviation phenomenon through the flue gas rectification device, so that the local velocity unevenness is reduced to a minimum, and no obvious deviation occurs, so that the flow velocity of the flue gas at different positions in the same section of the flue gas duct is close, thereby improving the heat exchange efficiency of the multi-stage heat exchanger. Subsequently, the mixed gas passes through each stage of the heat exchanger by its own diffusion effect to achieve the purpose of uniform mixing of ammonia and flue gas, so that the catalytic effect of the catalyst at different positions in the catalyst layer on the mixed gas is effectively exerted, thereby improving the denitrification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a front view of the high-efficiency SCR denitrification device for the gas turbine unit.

[0023] Figure 2 This is the axonometric view of the high-efficiency SCR denitrification device for the gas turbine unit.

[0024] Figure 3 This is the layout diagram of the flow meter probe.

[0025] Figure 4 This is the layout diagram of the spray gun.

[0026] Figure 5 Schematic diagram of a flue gas rectifying device; Figure (a) is a schematic diagram of a rectifying orifice plate, and Figure (b) is a schematic diagram of a rectifying grid plate.

[0027] Figure 6 This is the process flow chart of high-efficiency SCR denitrification.

[0028] In the figure: a flue gas outlet pipe 10; a rotating blade 11; a flue gas outlet end 12; a flow rate measuring device 20; a first flow rate measuring instrument probe 21; a second flow rate measuring instrument probe 22; an ammonia water injection device 30; a first spray gun 31; a second spray gun 32; a flue gas rectifying device 40; a rectifying orifice plate 41; a rectifying grid plate 42; a catalyst layer 50; a multi-stage heat exchanger 60; a flue gas duct 70; and a chimney 80. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1; See also Figure 1-4 A high-efficiency SCR denitration device for a gas turbine unit includes a flue gas duct 70, a multi-stage heat exchanger 60, and a catalyst layer 50; the upstream end of the flue gas duct 70 is connected to the flue gas outlet pipe 10 of the gas turbine unit, and the downstream end is connected to the chimney 80; the multi-stage heat exchanger 60 and the catalyst layer 50 are arranged in the downstream of the flue gas duct 70; It also includes a flow rate measuring device 20 and an ammonia water injection device 30; the flow rate measuring device 20 and the ammonia water injection device 30 are arranged in sequence upstream of the flue gas duct 70, and the probe of the flow rate measuring device 20 and the nozzle of the ammonia water injection device 30 are evenly distributed on two different cross-sections in the flue gas duct 70, and the number and position of the probes and nozzles match.

[0031] In this embodiment, according to the cross-sectional characteristics of the flue gas duct 70, the flue gas duct 70 is mainly divided into an upstream circular tube section, a midstream expanded section and a downstream square tube section, and the upstream circular tube section matches the flue gas outlet pipe 10. Compared with the upstream circular tube section, the uniformity of flue gas distribution in the midstream expanded section and the downstream square tube section is worse. The cyclone (rectifier) ​​and the catalyst layer are all referenced to the prior art.

[0032] The flow velocity measuring device 20 includes a first flow velocity measuring instrument and eight second flow velocity measuring instruments, wherein the first flow velocity measuring instrument probe 21 is located on the axis of the flue gas duct 70; a plurality of second flow velocity measuring instrument probes 22 are evenly distributed in the upstream circular pipe section of the flue gas duct 70 along the circumferential direction, and the circle where the plurality of second flow velocity measuring instrument probes 22 are located is concentric with the circle where the flue gas channel 70 is located, and the insertion depth of the probes in the flue gas duct 70 is adjustable; specifically, a mounting seat for the flow velocity measuring instrument and the spray gun is provided on the inner wall of the flue gas duct 70, and the mounting seat is sealed with the inner wall of the flue gas duct 70, the probe of the flow velocity measuring instrument and the spray gun nozzle can pass through the mounting seat and the insertion depth in the flue gas duct 70 is adjustable, and the probe, the spray gun and the mounting seat are also sealed and connected; since the Reynolds number at the measuring position is large, the flue gas flow is stable, and the relative position size of the flow velocity distribution is basically unchanged (within the range of gas turbine load variation), the probe and the spray gun are adjusted less frequently, and there is no need to adjust repeatedly, and the sealing can be guaranteed.

[0033] The ammonia injection device 30 includes a first spray gun 31 and eight second spray guns 32. The nozzle of the first spray gun 31 is located on the axis of the flue gas duct 70. The nozzles of the multiple second spray guns 32 are evenly distributed in the flue gas duct 70 along the circumferential direction, and the radius of the circle where the nozzles are located is the same as the radius of the circle where the second flow rate measuring instrument probe 22 is located. The first spray gun 31 and the second spray gun 32 both adopt dual-fluid spray guns and adopt reverse injection (that is, the injection direction is opposite to the flue gas flow direction), which is conducive to the evaporation of ammonia water and the mixing of ammonia water and flue gas. The distance between the flow rate measuring device 20 and the ammonia injection device 30 is 400mm.

[0034] The input end of the ammonia injection controller is respectively connected to the first flow velocity measuring instrument 21 and the second flow velocity measuring instrument 22, and the output end is respectively connected to the first spray gun 31 and the second spray gun 32. The ammonia injection amount of the first spray gun 31 is adjusted according to the measurement result of the first flow velocity measuring instrument 21, and the ammonia injection amount of the second spray gun 32 is adjusted according to the measurement result of the second flow velocity measuring instrument 22; of course, the ammonia injection controller is preferably able to adjust the ammonia injection amount of the corresponding second spray gun 32 according to the measurement result of each second flow velocity measuring instrument 22, so as to realize one-to-one ammonia injection. The ammonia injection controller adopts the injection controller in the prior art, which will not be described in detail here.

[0035] The catalyst layer 50 is arranged inside the flue gas duct 70, between the multi-stage heat exchangers 60, and the temperature of the catalyst layer 50 is about 360-420°C. Specifically, the multi-stage heat exchanger 60 is provided with 5 stages, and the catalyst layer 50 is arranged between the second stage heat exchanger and the third stage heat exchanger of the multi-stage heat exchanger. The catalyst layer is a honeycomb structure or a corrugated plate structure. At the optimal temperature, the catalyst layer 50 can maximize its catalytic effect and improve the flue gas denitrification efficiency.

[0036] Compared with the prior art method of producing ammonia by pyrolysis of urea outside the flue and the comparative patent CN110508132A method of producing ammonia by pyrolysis of urea inside the flue, this embodiment adopts the method of directly spraying ammonia water, which eliminates the complex structure, saves external space, is more economical, and is conducive to popularization and application. Moreover, this embodiment adopts a flow rate measuring device, which can measure the distribution characteristics of the flue gas discharged from the gas turbine unit inside the upstream of the flue gas pipeline, providing a prerequisite for accurate spraying of ammonia water; then, according to the requirements of the ammonia-nitrogen molar ratio, more ammonia water is sprayed to the area with a large amount of flue gas, and less or even no ammonia is sprayed to the area with a small amount of flue gas, and the position, quantity and flow rate of the spray gun are accurately adjusted to maintain the ammonia-nitrogen molar ratio within a controllable range, which is conducive to the uniform mixing of flue gas and ammonia.

[0037] Embodiment 2; See also Figure 1-5 The difference between this embodiment and embodiment 1 is that a different flue gas straightening device 40 is used. The flue gas straightening device 40 is arranged inside the middle and downstream of the flue gas duct 70 and before the multi-stage heat exchanger 60 to convert the spiral flow of the flue gas into a straight and uniform flow along the flue gas channel 70.

[0038] Specifically, the flue gas rectifying device 40 includes a rectifying orifice plate 41 and a rectifying grid plate 42, and the rectifying grid plate 42 is welded to the back of the rectifying orifice plate 41; the rectifying orifice plate 41 is provided with a number of through holes along the thickness direction, with a small opening rate around, a large opening rate in the middle, a large opening rate in the upper part, and a small opening rate in the lower part, and the total opening rate is 61%; the diameter of the through hole is 100mm; the grid hole size of the rectifying grid plate 42 is 200mm*150mm. The reason why the opening rate is large at the top and small at the bottom is that the midstream of the flue gas pipeline tends to expand upward, and the amount of flue gas in the lower part will be more than that in the lower part.

[0039] Specifically, the flue gas straightening device 40 (rectifying orifice plate 41 and rectifying grid plate 42) can also be arranged in the midstream expansion section of the flue gas duct 70 (preferably near the midstream end), and the arrangement angle of the rectifying grid plate 42 of the flue gas straightening device 40 is adapted to the expansion section, but because the flue gas flow direction is not perpendicular to the multi-stage heat exchanger 60, it is necessary to add a rectifying grid plate 42 perpendicular to the axis of the downstream square pipe section of the flue gas duct 70 in the pipe section before the multi-stage heat exchanger 60 to adjust the flue gas flow direction. Compared with the above method, the flue gas straightening device 40 can also be arranged downstream of the flue gas duct 70 (before the multi-stage heat exchanger 60), and the flue gas straightening device 40 is perpendicular to the axis of the flue gas duct 70, which is more convenient and economical.

[0040] This embodiment adopts a flue gas rectification device 40 for rectification. Compared with the existing cyclone (rectifier), it has a simple structure and low cost, reduces the resistance caused by complex decyclones, and the increase in system resistance is relatively small; a combination of multi-point ammonia injection + rectification orifice plate and rectification grid plate is adopted to accurately control the ammonia injection amount to obtain a relatively uniform ammonia and flue gas mixture, and then the overall deviation phenomenon is adjusted through the flue gas rectification device, so that the local velocity non-uniformity is reduced to a minimum, and no obvious deviation occurs, so that the flow velocity of the flue gas at different positions in the same section of the flue gas duct is close, so that the catalytic effect of the catalyst at different positions in the catalyst layer on the mixed gas can be effectively exerted, thereby improving the denitrification efficiency.

[0041] Embodiment 3; See also Figure 1-6 This embodiment also provides a high-efficiency SCR denitration method for a gas turbine unit, comprising the following steps: The flow rate measuring device 20 measures the flow rate of the smoke flowing forward spirally at different positions in a cross section upstream of the smoke duct 70; The spray gun in the ammonia water spraying device 30 sprays different amounts of ammonia water to corresponding positions in another cross section upstream of the flue gas duct 70 according to the flow velocity at different positions. The ammonia water is heated and gasified into ammonia gas during the mixing process with the flue gas, thereby obtaining a mixed gas of flue gas and ammonia gas. The ammonia concentration of the mixed gas at different positions in the same cross section is close. After the ammonia water is completely gasified, the mixed gas of the flue gas and ammonia flows through the flue gas rectifying device 40 for rectification, so that the spiral forward flow is rectified into a straight flow, and the flue gas and ammonia are further mixed, so that the velocity, velocity deflection angle and ammonia concentration of the mixed gas at different positions in the same cross section are further close; The mixed gas of flue gas and ammonia flows through several stages of heat exchangers before the catalyst layer in the multi-stage heat exchanger 60, and the mixed gas is further rectified and mixed so that the velocity, velocity deflection angle and ammonia concentration of the mixed gas at different positions in the same cross-section meet the design requirements, and then flows through the catalyst layer 50 to catalyze denitrification; finally, it flows through the latter stages of heat exchangers in the multi-stage heat exchanger 60 until it is discharged.

[0042] Before the mixed gas of flue gas and ammonia enters the catalyst layer, the velocity, velocity deflection angle and ammonia concentration distribution of the mixed gas at different positions of the same cross section of the flue gas duct meet the design requirements, and the catalytic reaction is sufficient.

[0043] The working principle of the present invention is as follows: a rotating blade is arranged in the flue gas outlet pipe 10 of the gas turbine unit, and the high-temperature flue gas discharged by the gas turbine unit drives the rotating blade 11 to rotate, and the high-temperature flue gas also rotates with the rotating blade 11, and then enters the upstream of the flue gas duct 70 through the flue gas outlet end 12. Due to the high-speed rotation of the flue gas, the flow velocity distribution of the flue gas in the flue gas outlet end 12 is very uneven, so the present invention sets a flow velocity measuring device 20 inside the upstream of the flue gas duct 70, and the insertion depth of the measuring probe in the flue gas duct 70 is adjustable. By measuring a certain upstream The flue gas velocity at different positions on a cross section is measured to obtain the flow rate in a small local area where the measuring probe is located, and then the accurate data of the actual flue gas flow distribution in the flue gas duct 70 is obtained. Based on this, the ammonia flow rate sprayed by each spray gun is adjusted to make the mixing ratio of the ammonia injection amount and the flue gas flow rate in each local area similar, and finally ensure that the ammonia nitrogen molar ratio is maintained within a controllable range. The ammonia gas is heated and gasified to generate ammonia gas during the mixing process with the flue gas; then, the mixed gas of the flue gas and ammonia gas enters the midstream expansion section of the flue gas duct 70, and the ammonia and flue gas in this area are further The mixed gas flows through the flue gas rectifying device 40 at the midstream end (or downstream beginning) of the flue gas duct 70. The flue gas rectifying device 40 includes a rectifying orifice plate 41 in front and a rectifying grid plate 42 in the rear. The rectifying orifice plate 41 has rectifying distribution holes unevenly distributed. According to the characteristics of the incoming flow, the general principle is to adopt the characteristics of the opening rate of the surrounding area being relatively smaller than the middle, and the opening rate of the lower part being smaller than the opening rate of the upper part for partitioning. The mixed gas coming out of the rectifying orifice plate 41 flows through the rectifying grid plate 42 for rectification, so that the flue gas flow at different positions on the cross section of the flue gas duct 70 is uniform. The speed is further approached; a multi-stage heat exchanger 60 is arranged inside the downstream of the flue gas duct 70, and the flue gas rectification device 40 can also make the mixed gas flow vertically to the multi-stage heat exchanger 60, reducing the scouring of the multi-stage heat exchanger 6 and avoiding the subsequent flue gas from deviating again; the mixed gas passes through the first few stages of heat exchangers, and after the mixed gas is further rectified, the uniformity of the velocity distribution, the velocity deflection angle and the uniformity of the ammonia concentration in the mixed gas meet the design requirements, and then the mixed gas enters the catalyst layer 5, completes the denitration, enters the latter stages of the multi-stage heat exchanger 60, and enters the chimney 7 for discharge.

[0044] The greatest advantages of the present invention are: 1) based on the characteristics of spiral flow and uneven distribution of flue gas at the tail of the gas turbine unit, the ammonia injection amount is adjusted by multi-point flow velocity measurement, and the mixing uniformity of the flue gas and ammonia is controlled in advance, reducing the pressure of uniform mixing during rectification, and at the same time, the control of the ammonia injection amount is more accurate, more economical and reasonable; 2) The complexity of the rectification structure (derotator) is reduced, and the flue gas is rectified with a simple structure; 3) By setting a rectification structure and combining it with other structures with rectification function, flue gas rectification is jointly realized, so that the velocity distribution uniformity (deviation is less than 15%), velocity deflection angle (within ±10°) and ammonia concentration (less than 5%) of the flue gas at different positions of the same cross-section inside the downstream of the flue gas duct 70 meet the design requirements, so that the catalytic effect of the catalyst at different positions in the catalyst layer on the mixed gas can be effectively exerted, so that the denitrification efficiency is maximized.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-efficiency SCR denitration device for a gas turbine unit, comprising a flue gas duct, a multi-stage heat exchanger, and a catalyst layer; the upstream end of the flue gas duct is connected to the flue gas outlet pipe of the gas turbine unit, and the downstream end is connected to the chimney; the multi-stage heat exchanger and the catalyst layer are arranged inside the downstream of the flue gas duct; characterized in that: It also includes a flow rate measuring device and an ammonia water injection device; the flow rate measuring device and the ammonia water injection device are arranged in sequence upstream of the flue gas duct, and the probe of the flow rate measuring device and the nozzle of the ammonia water injection device are evenly distributed on two different cross sections in the flue gas duct.

2. The device according to claim 1, characterized in that: The number and position of the flow rate measuring device probe and the ammonia water injection device nozzle are matched.

3. The device according to claim 2, characterized in that: The flow velocity measuring device includes a first flow velocity measuring instrument and multiple second flow velocity measuring instruments. The probe of the first flow velocity measuring instrument is located on the axis of the flue gas duct; the probes of the multiple second flow velocity measuring instruments are evenly distributed in the flue gas duct along the circumferential direction, the circle where the probes of the multiple second flow velocity measuring instruments are located is concentric with the flue gas channel, and the insertion depth of the probes in the flue gas duct is adjustable; the number of the second flow velocity measuring instruments is not less than 6.

4. The device according to claim 3, characterized in that: The ammonia water injection device includes a first spray gun and multiple second spray guns. The nozzle of the first spray gun is located on the axis of the flue gas duct; the nozzles of the multiple second spray guns are evenly distributed in the flue gas duct along the circumferential direction, and the radius of the circle where the nozzles are located is the same as the radius of the circle where the second flow rate measuring instrument probe is located; the first spray gun and the second spray gun both use reverse injection.

5. The device according to any one of claims 1 to 4, characterized in that: It also includes a flue gas straightening device, which is arranged inside the middle and downstream of the flue gas pipeline and before the multi-stage heat exchanger to convert the spiral flow of the flue gas into a straight and uniform flow along the flue gas channel.

6. The device according to claim 5, characterized in that: The flue gas rectifying device comprises a rectifying orifice plate and a rectifying grid plate, wherein the rectifying grid plate is fixed on the back of the rectifying orifice plate.

7. The device according to claim 6, characterized in that: The rectifying orifice plate is provided with a plurality of through holes along the thickness direction, with a small opening rate on the periphery and a large opening rate in the middle, a large opening rate on the upper part and a small opening rate on the lower part, and a total opening rate of 30%-90%.

8. The device according to claim 7, characterized in that: The smoke rectifying device is arranged inside the downstream of the smoke duct and is perpendicular to the axis of the smoke duct.

9. The device according to claim 1, characterized in that: The catalyst layer is located between the multi-stage heat exchangers, and the temperature of the catalyst layer is 360°C-420°C.

10. A high-efficiency SCR denitrification method for a gas turbine unit, characterized in that: The steps include: The flow velocity measuring device measures the flow velocity of the flue gas flowing forward spirally at different positions in a cross section upstream of the flue gas duct; The spray gun in the ammonia water spraying device sprays different amounts of ammonia water to corresponding positions in another cross section upstream of the flue gas duct according to the flow velocity at different positions. The ammonia water is heated and gasified into ammonia gas during the mixing process with the flue gas, thereby obtaining a mixed gas of flue gas and ammonia gas. The ammonia concentration of the mixed gas at different positions in the same cross section is close. After the ammonia water is completely gasified, the mixed gas of flue gas and ammonia flows through the flue gas rectifying device for rectification, so that the spiral forward flow is rectified into a straight flow, and the flue gas and ammonia are further mixed, so that the velocity, velocity deflection angle and ammonia concentration of the mixed gas at different positions in the same cross section are closer; The mixed gas of flue gas and ammonia flows through several stages of heat exchangers before the catalyst layer in the multi-stage heat exchanger, and the mixed gas is further rectified and mixed so that the velocity, velocity deflection angle and ammonia concentration of the mixed gas at different positions in the same cross-section meet the design requirements, and then flows into the catalyst layer for catalytic denitrification; finally, it flows through the latter stages of the multi-stage heat exchanger until it is discharged.

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