Flue from outlet of electrostatic dust collector to inlet of induced draft fan of 600MW-grade coal-fired power plant

Abstract

The utility model discloses a flue from an outlet of an electrostatic dust collector to an inlet of an induced draft fan in a 600MW-grade coal-fired power plant. The flue mainly comprises a straight flue I, a straight flue II, a straight flue III and a straight flue IV, an elbow I is arranged behind the straight flue I, and an outlet of the elbow I is vertically downward; an outlet of the second elbow horizontally faces the outer side of the boiler and is connected with a third straight flue, the rear of the third straight flue is connected with a first reducer pipe, the bottom of the first reducer pipe is horizontal, the cross sections of an inlet and an outlet are interchangeable in height and width, the rear of the first reducer pipe is connected with a third elbow, and an outlet of the third elbow is vertically downward; after outlets of the elbow I and the elbow III are flush and combined, a section of straight flue IV is arranged; the first elbow, the second elbow and the third elbow are 90-degree elbows. In a word, compared with the prior art, the distance between the boiler and the chimney is shortened, the occupied area of a project is reduced, and the project investment is reduced; the width direction of the induced draft fan frame can be controlled within the width range of the dust remover, a flue is shortened, flue elbows are reduced, and the investment of the flue and the induced draft fan frame is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of flue gas systems for power generation, and particularly relates to a flue from the outlet of an electrostatic precipitator to the inlet of an induced draft fan in a 600MW-class coal-fired power plant. Background Art

[0002] The boiler flue gas system is one of the important systems in a coal-fired power plant, which is used to send the flue gas after boiler combustion to the chimney for discharge. After the flue gas is discharged from the boiler air preheater, it successively enters the dust collector, induced draft fan, desulfurization absorption tower, and chimney, and finally is discharged into the atmosphere. The flue is a pipeline connecting the above-mentioned auxiliary equipment, which is used to send the flue gas from one equipment to the next along the above process. The equipment and flue of the flue gas system are arranged behind the boiler, and whether its design is reasonable affects the distance between the boiler and the chimney, and further affects the land occupation and investment of the whole project. In a 600MW-class coal-fired power plant, the most commonly used type of dust collector is the electrostatic precipitator. Each 600MW-class coal-fired generating unit is equipped with 2 double-chamber dust collectors, and generally 2 induced draft fans are provided. Each induced draft fan corresponds to 1 dust collector and is symmetrically arranged about the boiler center line. Each double-chamber dust collector has 2 flue outlets. The most conventional method is to arrange the center line of each induced draft fan on the center line of the corresponding dust collector, with the outlet of the induced draft fan facing the back of the furnace (i.e., the chimney direction), and the center line of the induced draft fan coincides with the center line of the dust collector. Each dust collector outlet is first connected to a straight flue parallel to the center line of the dust collector, and then a 90° elbow is connected to turn it to the direction perpendicular to the center line of the dust collector. The flue arrangements of the 2 outlets of the same dust collector are symmetric about the center line of the dust collector, and the 2 elbows are connected by a straight pipe to form a Π-shaped flue. An opening is made below the middle of the straight pipe (i.e., the intersection with the center line of the dust collector), and the flue is connected to the inlet of the induced draft fan. The biggest advantage of this scheme is that the flues from the 2 outlets of the same dust collector to the induced draft fan are completely symmetric and the resistance is exactly the same, which is conducive to the average distribution of the flue gas in the dust collector. Due to the long length of the induced draft fan, components such as a reducer pipe and a damper need to be installed on the outlet flue of the induced draft fan before the elbow can be installed for turning. Therefore, this scheme will cause the distance between the boiler and the chimney to be too large, increasing the land occupation and investment of the project. If the induced draft fan is rotated 90° with the inlet center as the center and the outlet is arranged facing the boiler center line, that is, the outlets of the 2 induced draft fans of each boiler face each other, and the center lines are vertically arranged on the same straight line perpendicular to the boiler center line, the distance between the boiler and the chimney can be reduced. However, since the distance between the center lines of the 2 dust collectors of a conventional 600MW unit cannot meet the requirements of the outlet flue arrangements of the 2 induced draft fans, the distance between the 2 dust collectors needs to be increased, resulting in an increase in the site width. The Chinese patent "Improved distribution structure of the dust collector outlet flue and induced draft fan of a large coal-fired unit" (Patent No. 2017203028281, Publication Date: 2018-01-26) proposed a solution, which realizes an increase in the distance between the center lines of the 2 induced draft fan inlets without increasing the distance between the 2 dust collectors by changing the outlet of the first elbow on the outer dust collector outlet flue to face the outside of the boiler.In this solution, two 90° elbows are provided on the flue of each dust collector outlet. For the combined elbow formed by the two 90° elbows on the flue outside the boiler, according to the optimization suggestions for the aerial elbow shown in Table D.5 of the "Technical Specification for Design and Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010), the distance between the center line of the dust collector outlet and the center line of the induced draft fan inlet is 2D. 0 , that is, twice the width of the dust collector outlet flue; even considering the limit, that is, according to L = 0 in Table C.33 of the "Technical Specification for Design and Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010), the distance between the center line of the dust collector outlet and the center line of the induced draft fan inlet is also equal to the width of the dust collector outlet flue. The width of a single dust collector of a 600MW unit is generally 32 ± 1m. Taking 32m as an example, the distance from the center line of the outer side of the dust collector outlet to the outer side of the dust collector is about 8m. The width of the dust collector outlet is generally between 4.2 and 4.5m, and the distance from the tail of the induced draft fan motor to the inlet of the induced draft fan is generally more than 6.5m. Considering the maintenance of the induced draft fan motor, the distance from the center line of the frame column of the induced draft fan to the tail of the induced draft fan is more than 1m. Calculated according to the above data, the distance from the center line of the outermost column of the induced draft fan frame to the outermost side of the dust collector is about 4 - 8m. It can be seen that although this solution does not increase the width of the land occupation in the dust collector area, the width of the induced draft fan frame exceeds the width range of the dust collector by a large margin, which has an adverse impact on the layout and passage behind the dust collector. In addition, this solution increases the number of flue elbows, lengthens the flue length, and increases the investment in the flue and the induced draft fan frame. Summary of the Invention

[0003] The technical problem to be solved by the utility model is to provide a flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan in a 600MW-class coal-fired power plant with reasonable layout, less land occupation, good effect and investment saving.

[0004] To solve the above technical problems, the utility model adopts the following technical solutions:

[0005] The flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan in a 600MW-class coal-fired power plant mainly includes straight flue one, straight flue two, straight flue three and straight flue four; elbow one is installed behind straight flue one, and the outlet of elbow one is vertically downward; elbow two is installed behind straight flue two, the outlet of elbow two is horizontally towards the outside of the boiler, the outlet of elbow two is connected to straight flue three, a reducer one is connected behind straight flue three, the bottom of the reducer one is horizontal, and the height and width of the inlet and outlet cross-sections are interchanged. A reducer one is connected to elbow three behind, and the outlet of elbow three is vertically downward; the outlets of elbow one and elbow three are flush and merged to set a section of straight flue four; elbows one to three are all 90° elbows.

[0006] The cross-sections of the first to the third straight flues are all 4000mm×3800mm, and the cross-section of the fourth straight flue is 7600mm×4000mm. The lengths of the first to the fourth straight flues are 2665mm, 5865mm, 7400mm, and 5565mm respectively.

[0007] Elbow 1 and elbow 3 are sharp-turn elbows, and elbow 2 is a gentle-turn elbow.

[0008] The local resistance coefficients of elbow 1 to elbow 3 and reducer 1 are 0.726, 0.27, 0.31, and 0.005 respectively.

[0009] The inner and outer bending radii of elbow 1 are up to 518mm, the length of the straight section at the inlet end is 982mm, and the length of the outlet end is 1082mm.

[0010] The diffusion angle of reducer 1 in the height direction should be 7 - 15°, and its length is 1200mm.

[0011] The first straight flue is connected to the outlet of the dust collector on the outside of the boiler; the second straight flue is connected to the outlet of the dust collector on the center line of the boiler; after the fourth straight flue, an inlet damper of the induced draft fan is connected. A reducer 2 is installed below the damper, and the lower end of the reducer 2 is connected to the inlet of the induced draft fan.

[0012] The specifications of the damper are the same as the cross-section of the fourth straight flue.

[0013] In view of the problems existing in the current flue design, the inventor designed a flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan in a 600MW-class coal-fired power plant, which mainly includes the first straight flue, the second straight flue, the third straight flue, and the fourth straight flue; elbow 1 is installed behind the first straight flue, and the outlet of elbow 1 is vertically downward; elbow 2 is installed behind the second straight flue, the outlet of elbow 2 is horizontally towards the outside of the boiler, the outlet of elbow 2 is connected to the third straight flue, the third straight flue is connected to reducer 1 behind, the bottom of reducer 1 is horizontal, and the height and width of the inlet and outlet cross-sections are interchanged. Elbow 3 is installed behind reducer 1, and the outlet of elbow 3 is vertically downward; the outlets of elbow 1 and elbow 3 are flush and merged, and then a section of the fourth straight flue is provided; elbow 1 to elbow 3 are all 90° elbows. Applying the flue of this utility model, the center line of the inlet of the induced draft fan coincides with the center line of the outlet of the dust collector on the outside of the boiler; by reducing the inner turning radius of the elbow on the outlet flue of the dust collector on the outside of the boiler, the local resistance of the elbow is increased to make the resistances of the two outlet flues of the dust collector balanced; for the outlet flue of the dust collector on the center line side of the boiler, the height and width of the flue are interchanged by setting a reducer to make the cross-section of the elbow after turning vertically symmetric about the center line of the induced draft fan with the cross-section of the elbow after turning vertically of the outlet flue of the dust collector on the outside of the boiler; it is also possible to carry out numerical simulation of the flue gas flow field and set a deflector or a flow blocker at an appropriate position to make the flue gas flow rates on both sides uniform. Therefore, compared with the prior art, the utility model has the following beneficial effects:

[0014] (1) Compared with the conventional scheme, the distance between the boiler and the chimney is shortened, the project land occupation is reduced, and the project investment is lowered.

[0015] (2) Compared with the published patented technologies, the width direction of the induced draft fan frame can be controlled within the width range of the dust collector, the flue is shortened, the number of flue elbows is reduced, and the investment in the flue and the induced draft fan frame is lowered. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic three-dimensional layout structure diagram of the flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan in a 600 MW-class coal-fired power plant of the present utility model.

[0017] Figure 2 is Figure 1 a schematic plan layout structure and design usage diagram of the flue.

[0018] Figure 3 is Figure 2 a schematic elevation (in the A-A direction) layout structure and design usage diagram of the flue.

[0019] Figure 4 is Figure 2 a schematic elevation (in the B-B direction) layout structure and design usage diagram of the flue.

[0020] Figure 5 is a schematic diagram of elbow 1 before adjusting the bending radius.

[0021] Figure 6 is a schematic diagram of elbow 1 after adjusting the bending radius.

[0022] In the figure: 1 - dust collector, 2 - induced draft fan, 101 - straight flue 1, 102 - elbow 1, 201 - straight flue 2, 202 - elbow 2, 203 - straight flue 3, 204 - reducer 1, 205 - elbow 3, 3 - straight flue 4, 4 - inlet damper of the induced draft fan, 5 - reducer 2. SPECIFIC EMBODIMENTS

[0023] I. Design Principle

[0024] The 2 electrostatic precipitators of each boiler are arranged conventionally, and the distance between the 2 dust collectors is not increased temporarily. The outlets of the 2 induced draft fans are arranged towards the boiler center line, that is, the outlets of the 2 induced draft fans of each boiler face each other, and the center line of the induced draft fans is perpendicularly arranged on the same straight line with the boiler center line. The center line of the inlet of the induced draft fan coincides with the center line of the outlet of the dust collector on the outer side of the boiler. When cooperating with the dust collector manufacturer in design, it can be required that the manufacturer design the outlet section of the dust collector according to the required flue section to avoid setting a reducer at the outlet, and the aspect ratio of the flue section should be as close to 1 as possible. If not cooperating well with the manufacturer, a reducer is first set at the dust collector interface.

[0025] The outlet of the dust collector on the outer side of the boiler is first connected to a horizontal straight flue. The length of the aforementioned straight flue is determined according to the length required to meet the layout of the measuring points at the dust collector outlet. After the straight flue, an elbow one is installed. The outlet of the elbow one is vertically downward. There is no problem of ash accumulation in this elbow, and a sharp-turn elbow can be selected. The position of the center line of the induced draft fan is determined on the outer side of the wall surface of the outlet of the elbow one in the direction of the chimney. When determining the positioning of the center line of the induced draft fan, the size of the elbow one is designed according to the provisions of D2.1.1 in the "Technical Specification for Design Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010). The outlet of the dust collector on the center line of the boiler is first connected to a horizontal straight flue and then an elbow two is installed. The outlet of the elbow two is horizontally oriented towards the outer side of the boiler. Since there is ash accumulation in this elbow, in order to reduce the cross-sectional area of the flue to reduce ash accumulation, a slow-turn elbow is selected for this elbow. After the outlet of the elbow two is connected to a horizontal straight flue, an eccentric reducer is connected to exchange the length and width of the flue. The reducer is as short as possible on the premise of meeting D.3.1 in the "Technical Specification for Design Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010). If the cross-section of the flue is square, this reducer is not required. The exchange of the length and width of the flue can make the cross-sectional area of the outlet of the elbow after the reducer and the cross-sectional area of the outlet of the elbow on the flue of the other dust collector outlet exactly the same. After the reducer, an elbow three is installed. The outlet of the elbow three is vertically downward. There is no problem of ash accumulation in this elbow, and a sharp-turn elbow or a slow-turn elbow can be selected according to the layout needs. According to the data in Table D.1 in the "Technical Specification for Design Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010), the resistance coefficients of the sharp-turn elbow and the slow-turn elbow that meet the provisions of D2.1.1 in this specification do not differ much. The outer side of the wall surface of the outlet of the elbow in the direction of the boiler coincides with the previously determined center line of the induced draft fan, and the center line of the other direction of the outlet of the elbow coincides with the center line of the inlet of the induced draft fan, so as to determine the lengths of the above two straight flues.

[0026] According to the above design, the cross-sectional dimensions of the outlets of elbow one and elbow three are symmetrical about the center line of the induced draft fan. For the convenience of processing and manufacturing, elbow one and elbow three can also be combined into one part, and the flue wall surfaces at the overlapping part are combined into the same steel plate. After the outlets of the two elbows are combined, a straight flue is provided. The cross-section of the flue is the sum of the cross-sections of elbow one and elbow three. The length of the straight flue is designed according to the need to meet the connection of the connecting flue. An inlet damper of the induced draft fan is provided below the straight flue, and a reducer is provided below the damper and connected to the inlet of the induced draft fan. According to this scheme, the outermost columns of the induced draft fan frame can fall within the width range of the dust collector.

[0027] Due to the different arrangements of the two outlet flues of the dust collector, the length of the outlet flue of the dust collector on one side of the boiler center is longer and there are more special-shaped parts. To make the total resistance of the flues equal, the local resistance of elbow one on the outlet flue of the dust collector on the outer side of the boiler can be increased by reducing the turning radius of elbow one, so as to balance the resistance of the two outlet flues. First, elbow two and elbow three on the outlet flue of the dust collector on one side of the boiler center are designed according to the requirements of D2.1.1 in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010), and the reducer is designed according to the requirements of D.3.1 in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010) to minimize the resistance on this section of the flue. The local resistance coefficients are respectively set as ζ1, ζ2, and ζ3, and the specific values are determined according to the provisions of 11.5 in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010). After determining the external dimensions of these three special-shaped parts, the total developed length L1 of the flue can be determined. According to 11.6.1 in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010), the friction resistance coefficient λ of the flue is determined, and the total resistance of this section of the flue is (ζ1 + ζ2 + ζ3 + λL1 / De)×ω 2 / 2×ρ, where De is the equivalent diameter of the flue, ω is the flue gas flow velocity, and ρ is the flue gas density. Then, calculate the developed length L2 of the outlet flue of the dust collector on the outer side of the boiler. Since λ, De, ω, and ρ of the flues on both sides are equal, therefore, for the resistances of the flues on both sides to be the same, the local resistance coefficient ζ4 of elbow one = ζ1 + ζ2 + ζ3 + λL1 / De - λL2 / De. Then, using the calculated ζ4 and referring to the data in Table D.1, No. B in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010), interpolation method is used for calculation, and finally the inner turning radius of elbow one can be calculated. In implementation, to simplify the design process, elbow one can also be designed according to the requirements of D2.1.1 in the "Technical Code for Design Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240-2010), and the flue arrangement is provided to the dust collector manufacturer for numerical simulation of the flue gas flow field, and flow guiding plates or flow blocking plates are set at appropriate positions to make the flue gas flow rates on both sides uniform.

[0028] The lengths of induced draft fans with different parameters or from different manufacturers are slightly different. For the vast majority of induced draft fans, the distance between the two dust collectors according to the conventional distance recommended by the dust collector manufacturer can meet the arrangement of the outlet flue of the induced draft fan, and there is no need to adjust the arrangement of the dust collectors. When the distance between the two induced draft fans cannot meet the requirements of the outlet flue arrangement of the induced draft fan, the distance between the two dust collectors can be appropriately increased.

[0029] II. Basic Structure

[0030] As Figure 1As shown in the figure, the flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan in a 600 MW-class coal-fired power plant mainly includes straight flue 1, straight flue 2, straight flue 3, and straight flue 4. After straight flue 1, elbow 1 is installed, and the outlet of elbow 1 is vertically downward. After straight flue 2, elbow 2 is installed, the outlet of elbow 2 is horizontally towards the outside of the boiler, and the outlet of elbow 2 is connected to straight flue 3. After straight flue 3, reducer 1 is connected. The bottom of reducer 1 is horizontal, and the height and width of the inlet and outlet cross-sections are interchanged. After reducer 1, elbow 3 is connected, and the outlet of elbow 3 is vertically downward. The outlets of elbow 1 and elbow 3 are flush and merged, and then a section of straight flue 4 is provided. Elbows 1 to 3 are all 90° elbows.

[0031] III. Specific Examples

[0032] As Figures 2 to 4 shown in the figure, the attached drawing only shows the flue layout on the right side of the boiler center line, and the left side flue is symmetrical to the attached drawing about the boiler center line.

[0033] As Figure 2 shown in the figure, according to the equipment data provided by the dust collector manufacturer, the center line of dust collector 1 is 17375 mm away from the boiler center line. The distance between the two outlets of the dust collector is 16200, and the interface size of the dust collector is 4000×3800 (width×height) mm. The outlet of induced draft fan 2 is arranged towards the boiler center line, and the center line of the induced draft fan is perpendicular to the boiler center line. The center line of the inlet of the induced draft fan coincides with the center line of the outlet of the dust collector on the outside of the boiler.

[0034] A section of horizontal straight flue 101 is connected to the outlet of the dust collector on the outside of the boiler. The cross-section of straight flue 1 is 4000×3800 (width×height) mm. After cooperation with the dust collector manufacturer, the minimum straight flue required for installing the flue gas sampling point on the outlet flue of the dust collector is 2665 mm. After straight flue 1, elbow 102 is installed, and the outlet of elbow 1 is vertically downward. A sharp-turn elbow is selected. The height b of the flue is 3800 mm. According to D2.1.1 of the "Technical Specification for Design and Calculation of Combustion System in Coal-Fired Power Plants" (DL / T 5240-2010), the inner bending radius r n = 0.4b = 1520 mm, rounded up to 1500 mm. Then, the distance from the outside wall of the inlet of elbow 1 to the outlet towards the chimney direction can be calculated as 1500 + 3800 = 5300. From this, it can be determined that the distance from the center line of the induced draft fan to the outlet of the dust collector is 2665 + 5300 = 7965 mm.

[0035] At the outlet of the dust collector near the boiler centerline, a section of horizontal straight flue 201 is connected. The cross-section of the second straight flue is 4000×3800 (width×height) mm. After the second straight flue, an elbow 202 is installed. The outlet of the elbow is horizontally oriented towards the outside of the boiler. The outlet of the elbow is connected to the third straight flue 203. The cross-section of the third straight flue is 4000×3800 (width×height) mm. After the third straight flue, a reducer pipe 204 is connected. The bottom of the reducer pipe is horizontal, and the cross-section of the inlet and outlet is interchanged in height and width. The outlet cross-section is 3800×4000 (width×height) mm. After the reducer pipe, an elbow 205 is connected. The outlet of the elbow is vertically downward. The outer wall surface of the elbow outlet towards the boiler direction coincides with the previously determined centerline of the induced draft fan. It can be calculated that the centerline of the elbow is 7965 + 3800 / 2 = 9865 mm away from the outlet of the dust collector; the centerline of the elbow outlet in the other direction coincides with the centerline of the inlet of the induced draft fan, that is, the distance from the centerline of the dust collector outlet is 16200 mm. The elbow 205 is a sharp-turn elbow, the height of the flue b is 4000 mm, and the inner bending radius r n = 0.4b = 1600 mm. Then it can be calculated that the centerline of the inlet of the induced draft fan is 1600 + 4000 / 2 = 3600 mm away from the inlet of the elbow 205, and the distance from the outlet of the elbow to the centerline of the inlet of the elbow is also taken as 3600 mm. In order to make the outlets of the first elbow and the third elbow flush, the distance from the outlet of the first elbow to the centerline of the inlet is also determined to be 3600 mm. According to D.3.1 of "Technical Regulations for Design and Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240 - 2010), the diffusion angle of the reducer pipe 204 in the height direction should be 7 - 15°. It can be calculated that the length of the reducer pipe is 746 - 1628 mm. To avoid inconvenient processing due to too short length, 1200 mm is taken. The elbow 202 is a slow-turn elbow, b = 4000 mm. According to D2.1.1 of "Technical Regulations for Design and Calculation of Combustion System in Coal-Fired Power Plants" (DL / T5240 - 2010), r = b = 4000 mm is taken. According to the positioning of the elbow 205 and the dimensions of various special-shaped parts determined above, the lengths of the straight flue 201 and the third straight flue can be calculated. Among them, the length of the second straight flue is 9865 - 4000 = 5865 mm, and the length of the third straight flue is 16200 - 3600 - 1200 - 4000 = 7400 mm.

[0036] To balance the resistance of the flue ducts on both sides, the inner bending radius of elbow one is adjusted. According to the determined dimensions of the special-shaped parts and Article 11.5 of the "Technical Specification for Design Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010), the local resistance coefficients can be calculated. Let the local resistance coefficient of elbow two be ζ1 = 0.27, the local resistance coefficient of reducer one be ζ2 = 0.005, and the local resistance coefficient of elbow three be ζ3 = 0.31. The developed length of the flue duct on one side of the boiler centerline is L1 = 27.2 m, the developed length of the outer flue duct of the boiler is L2 = 8.9 m, the equivalent diameter of the flue duct is De = 3.9 m, and the friction resistance coefficient is λ = 0.03. Then the local resistance coefficient of elbow one is ζ4 = ζ1 + ζ2 + ζ3 + λL1 / De - λL2 / De = 0.27 + 0.005 + 0.31 + 0.03×27.2 / 3.9 - 0.03×8.9 / 3.9 = 0.726. According to Table D.1, No. B of the "Technical Specification for Design Calculation of Combustion System in Coal-fired Power Plants" (DL / T 5240-2010), by using the interpolation method, r n / b = 0.13647, then r n = 0.13647×3800 = 518 mm. Adjust the inner and outer bending radii of elbow one to 518 mm, and the overall dimensions of the elbow remain the original design, that is, straight sections are provided on both sides of the elbow arc. The length of the straight section at the inlet end is 1500 - 518 = 982 mm, and the length at the outlet end is 1600 - 518 = 1082 mm. The schematic diagram of elbow one before adjusting the bending radius is shown in Figure 5 , and the schematic diagram after adjusting the bending radius is shown in Figure 6 . Since the proportion of the friction resistance coefficient is relatively small, after modifying the bending radius of this elbow, the developed length of the flue duct is not calculated separately.

[0037] After the outlets of elbow one and elbow three are merged, a straight flue duct four is provided. The cross-section of straight flue duct four is the sum of the cross-sections of the outlets of elbow one and elbow three, that is, it is determined to be 7600×4000 mm. The length of straight flue duct four is designed to meet the connection requirements of the connecting flue. In this example, it is determined to be 5565 mm. A draft fan inlet damper 4 is connected behind straight flue duct four. The specification of the damper is the same as the cross-section of straight flue duct four, which is 7600×4000 mm. A reducer two 5 is provided below the damper. The upper cross-section of reducer two is the same as the damper specification, which is 7600×4000 mm; the lower end is connected to the draft fan inlet, and the cross-section is the same as the draft fan inlet cross-section; the length of the reducer is obtained by subtracting the outlet length of elbow 101, the length of straight flue duct four, and the thickness of the damper from the distance between the dust collector outlet elevation and the draft fan inlet elevation. The calculation result in this example is 4507 mm. For easy installation, straight flue ducts can be provided at the upper and lower parts of reducer two.

[0038] After determining the flue duct layout according to the above implementation process, when installing a compensator at an appropriate position, disconnect the straight flue duct at the place where the space required for installing the compensator is located, and then install the compensator. This description will not elaborate further.

[0039] When implementing the present utility model, without increasing the width dimension of the dust collector area, the distance between the boiler and the chimney can be shortened, the project land occupation can be reduced, and the flue gas resistance between the two outlets of the dust collector and the induced draft fan can be made nearly equal, ensuring uniform distribution of flue gas in the dust collector. It can also control the width direction of the induced draft fan frame within the width range of the dust collector, shorten the flue, reduce the number of flue elbows, and reduce the investment in the flue and the induced draft fan frame.

Claims

1. A flue from the outlet of the electrostatic precipitator to the inlet of the induced draft fan of a 600MW coal-fired power plant, characterized in that It mainly includes straight flue 1, straight flue 2, straight flue 3 and straight flue 4; elbow 1 is installed behind straight flue 1, and the outlet of elbow 1 is vertically downward; elbow 2 is installed behind straight flue 2, and the outlet of elbow 2 is horizontally toward the outside of the boiler, the outlet of elbow 2 is connected to straight flue 3, straight flue 3 is connected to reducer 1, the bottom of reducer 1 is horizontal, and the height and width of inlet and outlet sections are interchangeable, reducer 1 is connected to elbow 3, and the outlet of elbow 3 is vertically downward; a section of straight flue 4 is set after the outlets of elbow 1 and elbow 3 are flush and merged; elbows 1 to 3 are all 90° elbows.

2. The flue according to claim 1, characterized in that: The cross-sections of the straight flues one to three are 4000mm×3800mm, the cross-section of the straight flue four is 7600mm×4000mm, and the lengths of the straight flues one to four are 2665mm, 5865mm, 7400mm, and 5565mm, respectively.

3. The flue according to claim 1, characterized in that: The first elbow and the third elbow are sharp bends, and the second elbow is a gentle bend.

4. The flue according to claim 1, characterized in that: The local resistance coefficients of elbows 1 to 3 and reducer 1 are 0.726, 0.27, 0.31, and 0.005, respectively.

5. The flue according to claim 4, characterized in that: The inner and outer bending radii of the elbow 1 are 518 mm, the straight section length at the inlet end is 982 mm, and the length at the outlet end is 1082 mm.

6. The flue according to claim 5, characterized in that: The diffusion angle of the reducer in the height direction is preferably 7-15°, and its length is 1200 mm.

7. The flue according to claim 1, characterized in that: The straight flue 1 is connected to the dust collector outlet on the outside of the boiler; the straight flue 2 is connected to the dust collector outlet on the center line of the boiler; the straight flue 4 is connected to the induced draft fan inlet damper, and a reducer pipe 2 is arranged below the damper, and the lower end of the reducer pipe 2 is connected to the induced draft fan inlet.

8. The flue according to claim 7, characterized in that: The specifications of the damper are the same as the cross section of the straight flue 4.

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