A controllable bypass flue gas mixing reheating device for a power station boiler

Abstract

The present invention discloses a controllable bypass flue gas mixing and reheating device for a power station boiler, comprising a superheater outlet flue and a bypass flue, and a low-temperature reheater and an economizer arranged in sequence in the superheater outlet flue; the upper end of the bypass flue is connected to the upstream of the low-temperature reheater in the superheater outlet flue, and the lower end is connected to the main flue of the economizer outlet section; a jet nozzle is arranged at the end of the bypass flue inserted into the main flue; the jet nozzle comprises a nozzle body, and a plurality of nozzle bundles located on the side of the nozzle body; each nozzle bundle can reciprocate in a direction perpendicular to the axis of the nozzle body to achieve umbrella-like opening and closing, thereby adjusting the position and flow direction of the ejected flue gas. The present invention can effectively utilize the flue gas in the main flue and the waste heat of the outlet flue, and improve the thermal utilization rate of the system; compared with the prior art, the flue gas disturbance is greatly enhanced, so that the temperature components of the mixed flue gas are more uniform, and the SCR inlet flue gas temperature can be effectively increased.

Description

Technical Field

[0001] The invention relates to the field of boiler flue gas reheating SCR denitration, and in particular to a controllable bypass flue gas mixing reheating device for a power station boiler. Background Art

[0002] With the trend of vigorously developing clean energy, thermal power generation, as the pillar of the industry, still plays an important role in flexible peak load regulation in power production. The peak load regulation capacity of thermal power units shows a trend of multiple demands and high requirements. The number and time of the unit running under low load (generally below 50% of the rated load) conditions increase, and the flue gas temperature decreases, which affects the existing widely used flue gas selective catalytic reduction denitrification technology (SCR technology).

[0003] The principle of SCR (Selective Catalytic Reduction) denitrification technology is that under the action of catalyst, the reducing agent (such as liquid ammonia, urea and ammonia water, etc.) "selectively" reduces NOx in the flue gas to N2 in the range of about 260-420℃, and almost no oxidation reaction of NH3 and O2 occurs, generating non-polluting NOx of N2 and H2O. The low-load operation of the unit reduces the flue gas temperature at the SCR inlet. When it is below 260℃, the NH3 produced by the reducing agent reacts with SO3 in the flue gas to generate ammonium sulfate or ammonium bisulfate. The generated ammonium salt will block the micropores of the catalyst active material, causing wear and reducing the activity of the catalyst, thereby leading to problems such as reduced catalytic efficiency and increased ammonia slip.

[0004] Therefore, in order to improve the above situation and increase the flue gas temperature at the low-load SCR inlet, some power plants mostly adopt the economizer bypass flue modification plan to introduce the high-temperature flue gas from the bypass flue into the low-temperature flue gas. Most of the mixing methods use lateral jets to directly pass into the low-temperature flue gas. At the same time, compared with the size of the main flue, the size of the bypass flue is smaller, and the lateral jet directly enters the flue gas. There are large deviations in the flue gas flow rate, components, temperature, etc., resulting in poor actual mixing effect in the flue and uneven distribution of flue gas components. The local resistance in the flue increases, which is easy to cause wear on the pipe wall. The temperature distribution inside the flue is obviously different, with high temperature in the upper part and low temperature in the lower part, which in turn causes the catalyst activity in the low-temperature area under low load to decrease, affecting the normal operation of the SCR denitrification system and seriously reducing the denitrification efficiency. At the same time, the flue built-in gas mixing device itself has high engineering costs and complex technical steps. Summary of the invention

[0005] In order to solve the problems of uneven mixing of high and low temperature flue gas in the bypass flue and the main flue after low load operation in the prior art, the deterioration of the inlet flue gas temperature field of the SCR denitration technology of the power station boiler, affecting the activity of the catalyst, resulting in reduced denitration efficiency and increased ammonia escape rate, etc., the present invention proposes a controllable bypass flue gas mixing and reheating device for power station boilers, and the specific technical scheme is as follows:

[0006] A controllable bypass flue gas mixing reheating device for a power station boiler comprises a superheater outlet flue and a bypass flue, and a low-temperature reheater and an economizer arranged in sequence in the superheater outlet flue;

[0007] The upper end of the bypass flue is connected to the upstream of the low-temperature reheater in the flue at the outlet of the reheater, and the lower end is connected to the main flue at the outlet section of the economizer; a jet nozzle is arranged at the end of the bypass flue inserted into the main flue;

[0008] The jet nozzle includes a nozzle body and a plurality of nozzle bundles located on the side of the nozzle body; each nozzle bundle can reciprocate in a direction perpendicular to the axis of the nozzle body to achieve umbrella-like opening and closing, thereby adjusting the position and flow direction of the ejected smoke.

[0009] Furthermore, the jet nozzle includes a nozzle body, a nozzle connecting section, a small nozzle, a first electric push rod, a connecting support ring, an adjusting rod, a support rod, and an annular universal joint;

[0010] A plurality of branch pipes extending outward are axially provided on the side surface of the nozzle body, each branch pipe is sleeved with a nozzle connecting section, the nozzle connecting section has a plurality of umbrella-shaped connecting parts extending in parallel, and each connecting part is connected to a small nozzle; the support rod is located in the middle position of the nozzle connecting section, one end of which is fixedly connected to the nozzle connecting section, the connecting support ring is sleeved on the support rod, the first electric push rod is fixedly connected to the support rod, and the output end of the first electric push rod is connected to the connecting support ring; the connecting support ring is rotatably connected to a plurality of adjusting rods through an annular universal joint, and the adjusting rods correspond to the small nozzles one by one; the first electric push rod pushes the connecting support ring to move horizontally along the axial direction perpendicular to the nozzle body, and then drives the plurality of small nozzles to perform umbrella-shaped reciprocating opening and closing motion through the adjusting rod, thereby changing the expansion angles of the plurality of small nozzles, thereby adjusting the position and flow direction of the ejected smoke.

[0011] Furthermore, the jet nozzle also includes a second electric push rod and a support adjustment rod. Each nozzle connecting section is rotatably connected to one end of a plurality of support adjustment rods through an annular universal joint. The second electric push rod is fixed to the nozzle body. One end of the support adjustment rod is rotatably connected to the second electric push rod, and the other end is rotatably connected to the support adjustment rod. The support adjustment rod is driven to rotate by the push of the second electric push rod, thereby driving the nozzle connecting section to move horizontally along the axial direction perpendicular to the nozzle body.

[0012] Furthermore, each nozzle connecting section corresponds to a combination of two sets of second electric push rods and support adjustment rods.

[0013] Furthermore, the bottom of the nozzle body is conically tapered, with swirl blades, a rotating motor, and a fixed ring installed inside. The fixed ring is located in the center, and multiple swirl blades are arranged around the fixed ring. Each swirl blade is driven to rotate by a rotating motor to adjust the angle of the swirl blade.

[0014] Furthermore, a flow regulating valve is provided at the connection between the bypass flue and the jet nozzle.

[0015] Furthermore, an electrically controlled regulating valve, a temperature monitoring device 1, and a flow monitoring device 1 are sequentially provided at the entrance of the bypass flue, and the flow of the bypass flue is controlled by adjusting the opening of the electrically controlled regulating valve; the temperature monitoring device 1 and the flow monitoring device 1 are respectively used to detect the temperature and flow in the bypass flue.

[0016] Furthermore, a second temperature monitoring device and a second flow monitoring device are provided in the main flue downstream of the jet nozzle, which are used to monitor the temperature and flow of the flue gas mixed with the bypass flue, respectively.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The present invention can effectively solve the problem of uneven mixing caused by the injection of a single-hole transverse jet into the main flue gas, and improve the poor vertical distribution of the temperature and components of the flue gas after mixing;

[0019] (2) The tube bundles are arranged in a front-to-back staggered manner, which can better distribute the airflow in the main flue compared to the single jet and parallel arrangement of tube bundles in the prior art.

[0020] (3) The tail of the jet pipe adopts the form of a narrowed small hole. Compared with the bottom sealed structure in the prior art, it can solve the problem of ash particles in the flue gas depositing and clogging the small hole in the nozzle. At the same time, it can relatively alleviate the huge pressure difference between the inside of the jet pipe and the main flue, and improve the hazards of blockage and corrosion of the pipe wall structure caused by the large pressure difference.

[0021] (4) The tube bundle contains swirl blades with adjustable angles, which can form a strong swirl at the outlet, effectively blowing away the ash particles deposited in the small holes and at the bottom, ensuring the normal operation of the system.

[0022] (5) The present invention effectively utilizes the flue gas from the main flue and the waste heat from the outlet flue to improve the thermal utilization rate of the system; the flue gas mixing and reheating device used has low technical cost and difficulty, does not require complex engineering design, and is conducive to practical application in engineering. Compared with the existing technology, the flue gas disturbance is greatly enhanced, making the temperature components of the mixed flue gas more uniform, which can effectively increase the flue gas temperature at the SCR inlet, and improve the problems of decreased SCR denitrification efficiency, increased pollutant emissions, and ammonia slip. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a controllable bypass flue gas mixing and reheating device;

[0024] Figure 2 A schematic diagram of a bypass flue Figure 1 ;

[0025] Figure 3 A schematic diagram of a bypass flue Figure 2 ;

[0026] Figure 4 It is the left view of the nozzle head;

[0027] Figure 5 This is the front view of the nozzle head;

[0028] Figure 6 It is a partial cross-sectional view of the bypass flue;

[0029] Figure 7 is a schematic diagram of a smoke flow regulating unit at the bottom of the jet nozzle;

[0030] Figure 8 This is the velocity distribution diagram of the rear longitudinal section of the existing bypass single jet mixing reheat device;

[0031] Fig. 9 It is a velocity distribution diagram of the rear longitudinal section of the flue gas mixing and reheating device using the present invention.

[0032] In the figure, 1, superheater outlet flue; 2, low-temperature reheater; 3, economizer; 4, electric control valve; 5, temperature monitoring device 1; 6, flow monitoring device 1; 7, bypass flue; 8, expansion joint; 9, flow control valve; 10, main flue; 11, jet nozzle; 111, nozzle body; 112, flange; 113, nozzle connecting section; 114, nozzle head; 115, first electric push rod; 116, connecting support ring; 117, adjusting rod; 118, supporting rod; 119, second electric push rod; 120, supporting adjusting rod; 121, annular universal joint; 122, swirl blade; 123, rotating motor; 124, fixing ring; 12, temperature monitoring device 2; 13, flow monitoring device 2; 14, SCR denitrification reactor; 15, SCR denitrification outlet flue. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] like Figure 1As shown, the controllable bypass flue gas mixing reheating device of the power plant boiler of the present invention comprises a superheater outlet flue 1 and a bypass flue 7; the superheater outlet flue 1 is sequentially arranged with a low-temperature reheater 2 and an economizer 3, the upper end of the bypass flue 7 is connected to the upstream of the low-temperature reheater 2 in the superheater outlet flue 1, and the lower end is connected to the main flue 10 of the outlet section of the economizer 3. A jet nozzle 11 is arranged at the end of the bypass flue 7 inserted into the main flue 10, and a flow regulating valve 9 is arranged at the connection between the bypass flue 7 and the jet nozzle 11.

[0035] like Figures 2 to 6 As shown, the jet nozzle 11 includes a flange 112, a nozzle body 111, a nozzle connecting section 113, a small nozzle 114, a first electric push rod 115, a connecting support ring 116, an adjustment rod 117, a support rod 118, a second electric push rod 119, a support adjustment rod 120, an annular universal joint 121, a swirl blade 122, a rotating motor 123, and a fixing ring 124;

[0036] The flange 112 is located at the top of the nozzle body 111 and is used to connect with the bypass flue 7; a plurality of branch pipes extending outward are axially provided on the side of the nozzle body 111, each branch pipe is sleeved with a nozzle connecting section 113, the nozzle connecting section 113 has a plurality of umbrella-shaped connecting parts extending in parallel, each connecting part is connected to a small nozzle 114; the support rod 118 is located in the middle position of the nozzle connecting section 113, one end of which is fixedly connected to the nozzle connecting section 113, the connecting support ring 116 is sleeved on the support rod 118, the first electric push rod 115 is fixedly connected to the support rod 118, and the output end of the first electric push rod 115 is connected to the connecting support ring 116. The connecting support ring 116 is rotatably connected to multiple adjustment rods 117 through an annular universal joint 121. The adjustment rods 117 correspond to the small nozzles 114 one by one. The first electric push rod 115 pushes the connecting support ring 116 to move horizontally along the axial direction perpendicular to the nozzle body 111, and then drives the multiple small nozzles 114 to perform umbrella-shaped reciprocating opening and closing motion through the adjustment rods 117, thereby changing the expansion angles of the multiple small nozzles 114, thereby adjusting the position and flow direction of the ejected smoke.

[0037] There are also multiple nozzle connecting sections 113, which are evenly arranged along the axis direction of the nozzle body 111. Each nozzle connecting section 113 is rotatably connected to one end of several support adjustment rods 120 through an annular universal joint 121. The second electric push rod 119 is fixed to the nozzle body 111. One end of the support adjustment rod 120 is rotatably connected to the second electric push rod 119, and the other end is rotatably connected to the support adjustment rod 120. The second electric push rod 119 drives the support adjustment rod 120 to rotate, thereby driving the nozzle connecting section 113 to move horizontally along the axis direction perpendicular to the nozzle body 111, changing the direction and speed of the high-temperature flue gas jet, and achieving the effect of uniformly matching the flue gas. In order to achieve thrust balance for each nozzle connecting section 113, each nozzle connecting section 113 corresponds to a combination of two groups of second electric push rods 119 and support adjustment rods 120. As another embodiment, the nozzle connecting section 113 can also be arranged in a front-to-back staggered manner, so as to better distribute the airflow in the main flue.

[0038] In addition, if Figure 6 As shown, the bottom of the nozzle body 111 is conical, and a smoke flow regulating unit is installed inside. Figure 7 As shown, this flue gas flow regulating unit includes a swirl blade 122, a rotating motor 123, and a fixed ring 124. The fixed ring 124 is located in the center, and multiple swirl blades 122 are arranged around the fixed ring 124. Each swirl blade 122 is driven to rotate by a rotating motor 123, so as to adjust the angle of the swirl blade 122. When all the swirl blades 122 are closed, the middle fixed ring 124 serves as the outlet at the bottom, which can effectively prevent the accumulation of dust in the jet pipe from blocking the jet outlet. At the same time, the different opening and closing degrees of the swirl blades 122 will change the outlet resistance and flow rate of the lower part of the nozzle body 111, thereby affecting the resistance distribution along the inside of the nozzle, thereby changing the flow rate ejected from the nozzle part of the nozzle side wall.

[0039] The entrance of the bypass flue 7 is also provided with an electric control valve 4, a temperature monitoring device 5, and a flow monitoring device 6 in sequence. By adjusting the opening of the electric control valve 4, the flow of the bypass flue 7 can be controlled; the temperature monitoring device 5 and the flow monitoring device 6 are respectively used to detect the temperature and flow in the bypass flue 7. The multiple pipes of the bypass flue 7 are connected by an expansion joint 8, so as to compensate for the axial deformation of each section of the pipe. The main flue 10 is located downstream of the jet nozzle 11 and is provided with a temperature monitoring device 12 and a flow monitoring device 13, which are respectively used to monitor the temperature and flow of the flue gas mixed between the main flue 10 and the bypass flue 7. The mixed flue gas enters the SCR denitrification reactor 14 and is discharged from the SCR outlet flue 15.

[0040] Example 1

[0041] Using the existing boiler and SCR denitration device of a power station, and then combining the existing single-stream bypass flue mixing method without a jet nozzle and the single-stream bypass flue mixing method with a jet nozzle of the present invention, a low-load operation numerical simulation test was carried out to observe the velocity distribution diagram of the main flue 10 after the flue gas passes through the jet nozzle 11. The results are as follows: Figures 8-9 As shown. It can be observed that after a single jet mixes and reheats the flue gas, there is an obvious large-area separation of low-speed and high-speed areas in the depth direction, the cross-sectional velocity distribution is uneven, and the cross-sectional flue gas flow and component distribution show the same trend as the velocity distribution. In the numerical simulation test results of the flue gas mixing and reheating device of the present invention, it can be observed that the flue gas has no obvious velocity deviation, the velocity distribution is relatively regular, and the distribution is uniform in the longitudinal direction. This shows that the effect of flue gas mixing and reheating is significantly improved after the present invention.

[0042] The velocity deviation coefficient (CV value) was calculated by the following formula to evaluate the cross-sectional non-uniformity:

[0043]

[0044] Among them, V STD is the velocity standard deviation of the cross section, V Aver. is the surface average velocity of the cross section.

[0045] The cross-sectional velocity deviation coefficient (CV value) after the single-stream bypass flue mixing method is calculated to be 37.1%, and the cross-sectional velocity deviation coefficient (CV value) after the present invention is adopted is 13.69%. In comparison, the flue gas non-uniformity after mixing by the device of the present invention is significantly reduced, and the mixing effect of the flue gas is significantly improved.

[0046] Furthermore, under low load conditions, the temperature of the flue gas extracted from the main flue 10 by the bypass flue 7 is about 400-500°C, and the temperature of the flue gas at the outlet of the economizer 5 is about 200-240°C. The temperature monitoring device 2 12 monitors that the inlet flue gas temperature of the SCR reactor 14 has not reached the normal working temperature range of 270-360°C. The opening of the electronically controlled regulating valve 4 is adjusted, and the high-temperature flue gas is fully mixed with the flue gas of the main flue 10 through the jet nozzle 11. The temperature of the mixed flue gas is increased to between 280-310°C, and the jet nozzle 11 enhances the disturbance and evenly distributes the airflow, so that the velocity, flow rate, temperature and component distribution of the mixed flue gas are uniform in the longitudinal section. After the denitration reaction is completed, the flue gas temperature at the SCR denitration outlet flue 15 is about 270-300°C, achieving the effect of flue gas thermal mixing and achieving the purpose of increasing the inlet temperature of the SCR denitration.

[0047] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A controllable bypass flue gas mixing reheating device for a power station boiler, characterized in that: It comprises a superheater outlet flue (1) and a bypass flue (7), and a low-temperature reheater (2) and an economizer (3) which are sequentially arranged in the superheater outlet flue (1); The upper end of the bypass flue (7) is connected to the upstream of the low-temperature reheater (2) in the reheater outlet flue (1), and the lower end is connected to the main flue (10) of the economizer (3) outlet section; a jet nozzle (11) is provided at the end of the bypass flue (7) inserted into the main flue (10); The jet nozzle (11) comprises a nozzle body (111) and a plurality of nozzle bundles located on the side of the nozzle body (111); each nozzle bundle can reciprocate in a direction perpendicular to the axis of the nozzle body (111) to achieve an umbrella-like opening and closing, thereby adjusting the position and flow direction of the ejected smoke; The bottom of the nozzle body (111) is in a conical shape, and a swirl blade (122), a rotating motor (123), and a fixing ring (124) are installed inside. The fixing ring (124) is located at the center, and a plurality of swirl blades (122) are arranged around the fixing ring (124). Each swirl blade (122) is driven to rotate by a rotating motor (123), thereby adjusting the angle of the swirl blade (122).

2. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 1, characterized in that: The jet nozzle (11) comprises a nozzle body (111), a nozzle connecting section (113), a small nozzle (114), a first electric push rod (115), a connecting support ring (116), an adjustment rod (117), a support rod (118), and an annular universal joint (121); A plurality of branch pipes extending outward are axially provided on the side surface of the nozzle body (111), each branch pipe being sleeved with a nozzle connecting section (113), the nozzle connecting section (113) having a plurality of umbrella-shaped connecting parts extending in parallel, each connecting part being connected with a small nozzle (114); the support rod (118) is located in the middle of the nozzle connecting section (113), one end of which is fixedly connected to the nozzle connecting section (113), the connecting support ring (116) is sleeved on the support rod (118), the first electric push rod (115) is fixedly connected to the support rod (118), and the first electric push rod (118) is connected to the support rod (118). The output end of the connecting support ring (15) is connected to the connecting support ring (116); the connecting support ring (116) is rotatably connected to a plurality of adjusting rods (117) via an annular universal joint (121), and the adjusting rods (117) correspond to the small nozzles (114) one by one; the first electric push rod (115) pushes the connecting support ring (116) to move horizontally along an axial direction perpendicular to the nozzle body (111), thereby driving the plurality of small nozzles (114) to perform umbrella-shaped reciprocating opening and closing motions through the adjusting rods (117), thereby changing the expansion angles of the plurality of small nozzles (114), thereby adjusting the position and flow direction of the ejected smoke.

3. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 2, characterized in that: The jet nozzle (11) further comprises a second electric push rod (119) and a support adjustment rod (120); each nozzle connecting section (113) is rotatably connected to one end of a plurality of support adjustment rods (120) via an annular universal joint (121); the second electric push rod (119) is fixedly connected to the nozzle body (111); one end of the support adjustment rod (120) is rotatably connected to the second electric push rod (119), and the other end is rotatably connected to the support adjustment rod (120); the second electric push rod (119) pushes the support adjustment rod (120) to rotate, thereby driving the nozzle connecting section (113) to move horizontally along an axial direction perpendicular to the nozzle body (111).

4. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 3, characterized in that: Each nozzle connecting section (113) corresponds to a combination of two sets of second electric push rods (119) and support adjustment rods (120).

5. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 1, characterized in that: A flow regulating valve (9) is provided at the connection between the bypass flue (7) and the jet nozzle (11).

6. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 1, characterized in that: An electric control regulating valve (4), a temperature monitoring device (5), and a flow monitoring device (6) are arranged in sequence at the entrance of the bypass flue (7). The flow of the bypass flue (7) is controlled by adjusting the opening of the electric control regulating valve (4). The temperature monitoring device (5) and the flow monitoring device (6) are used to detect the temperature and flow in the bypass flue (7), respectively.

7. The controllable bypass flue gas mixing and reheating device for a power station boiler according to claim 1, characterized in that: A second temperature monitoring device (12) and a second flow monitoring device (13) are provided at a position of the main flue (10) downstream of the jet nozzle (11), and are used to monitor the temperature and flow of the flue gas mixed in the main flue (10) and the bypass flue (7), respectively.

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