JP2019052818A - Combustion ash bridge property evaluation device and combustion ash bridge property evaluation method - Google Patents

Abstract

To evaluate a bridge property of combustion ash in a heat transfer pipe of a boiler, in a combustion ash bridge property evaluation device.SOLUTION: A combustion ash bridge property evaluation device 30 in a transfer pipe of a boiler includes: a heating furnace 32; a fuel supply part 34 for supplying mixture of a fuel and air from one end side of the heating furnace 32; and a probe pipe arrangement part 36 which is arranged on the other end side of the heating furnace 32, and in which a plurality of probe pipes 54 provided by extending in the direction orthogonal to a flow direction of a combustion gas for evaluation in which the mixture combusted are arranged. The Reynolds number of the combustion gas for evaluation, and an outer diameter and a pitch of the probe pipe 54 are set so that the Strouhal number of the flow of the combustion gas for evaluation with respect to the probe pipes 54 becomes the same Strouhal number of the flow of the combustion gas with respect to the heat transfer pipe of the boiler.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a combustion ash bridge property evaluation apparatus and a combustion ash bridge property evaluation method, and more particularly to a combustion ash bridge property evaluation device and a combustion ash bridge property evaluation method in a heat transfer tube of a boiler.

  In recent years, fuels have been diversified in the field of boilers such as pulverized coal boilers, and the use of low-grade fuels such as subbituminous coal, lignite, and biomass has been expanded. Low-grade fuel contains a lot of low melting point compounds, which may increase the amount of ash adhering to the heat transfer tubes, such as the rear heat transfer section of the boiler, and may cause combustion ash bridges between the heat transfer tubes. (For example, refer to Patent Document 1).

JP 2004-116799 A

  By the way, if combustion ash adheres and accumulates on the wall surface of the heat transfer tube of the boiler, the heat transfer performance of the heat transfer tube may be lowered. Further, when a bridge of combustion ash is generated between the heat transfer tubes, the flow velocity of the combustion gas around the heat transfer tubes is lowered, which may lead to a decrease in heat transfer performance and consequently boiler efficiency. However, the evaluation method for the bridging property of the combustion ash in the heat transfer tube of the boiler has not been established yet.

  Then, the objective of this invention is providing the combustion ash bridge property evaluation apparatus and combustion ash bridge property evaluation method which can evaluate the bridge property of the combustion ash in the heat exchanger tube of a boiler.

  A combustion ash bridge property evaluation apparatus according to the present invention is a combustion ash bridge property evaluation device in a heat transfer tube of a boiler, which supplies a mixture of fuel and air from a heating furnace and one end side of the heating furnace. A probe tube arrangement in which a supply unit and a plurality of probe tubes arranged on the other end side of the heating furnace and extending in a direction intersecting with the flow direction of the combustion gas for evaluation in which the air-fuel mixture burns are arranged And an observation unit for observing the probe tube, wherein the Strouhal number of the flow of the combustion gas for evaluation with respect to the probe tube is the same as the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler As described above, the Reynolds number of the combustion gas for evaluation and the outer diameter and pitch of the probe tube are set.

  In the combustion ash bridging evaluation apparatus according to the present invention, the probe tube disposition unit is characterized in that the plurality of probe tubes are disposed along a flow direction of the evaluation combustion gas.

  In the combustion ash bridge property evaluation apparatus according to the present invention, the boiler is a pulverized coal boiler, and the fuel is subbituminous coal, lignite, or biomass.

  A combustion ash bridge property evaluation method according to the present invention is a combustion ash bridge property evaluation method in a heat transfer tube of a boiler, the step of obtaining a Strouhal number of the flow of combustion gas with respect to the heat transfer tube of the boiler, and the heat transfer tube of the boiler The Reynolds number of the evaluation combustion gas, and the outer diameter and pitch of the probe tube so that the Strouhal number of the flow of combustion gas with respect to the probe and the Strouhal number of the flow of evaluation combustion gas with respect to the probe tube are the same Crossing with respect to the longitudinal direction of the probe tube, and a setting step of setting a plurality of probe tubes having an outer diameter set in the setting step at a pitch set in the setting step An observation step of observing the probe tube by flowing the combustion gas for evaluation at a Reynolds number set in the setting step. That.

  In the combustion ash bridge property evaluation method according to the present invention, the arranging step arranges the plurality of probe tubes along a flow direction of the evaluation combustion gas.

  In the combustion ash bridge property evaluation method according to the present invention, the boiler is a pulverized coal boiler, and the fuel for the evaluation combustion gas is subbituminous coal, lignite or biomass.

  According to the above configuration, the flow of the combustion gas around the heat transfer tube of the boiler can be simulated, so that the bridging property of the combustion ash in the heat transfer tube of the boiler can be evaluated.

In embodiment of this invention, it is a schematic diagram which shows the structure of a boiler. In embodiment of this invention, it is a figure which shows the structure of a combustion ash bridge property evaluation apparatus. In embodiment of this invention, it is a figure which shows the structure of a probe tube. In embodiment of this invention, it is a figure which shows the arrangement configuration of a probe tube. In embodiment of this invention, it is a flowchart which shows the structure of the combustion ash bridge property evaluation method. In embodiment of this invention, it is a graph for demonstrating the estimation method of the straw hull number of the flow of the combustion gas with respect to the heat exchanger tube of a pulverized coal boiler. In embodiment of this invention, it is a graph for demonstrating the setting method of the Reynolds number of the combustion gas for evaluation, the outer diameter of a probe tube, and a pitch. In embodiment of this invention, it is a photograph which shows the observation result of the probe tube after 150-hour exposure.

  Embodiments of the present invention will be described below in detail with reference to the drawings. First, the boiler will be described. FIG. 1 is a schematic diagram showing the configuration of the boiler 10. The boiler 10 includes a boiler body 12 and a rear heat transfer section 14 provided in communication with the boiler body 12. The boiler body 12 is provided with a plurality of burners 16 at the bottom of the boiler body 12. Each burner 16 is connected to a pipe 18 through which a mixture of fuel and air is conveyed. When the boiler 10 is a pulverized coal boiler, for example, the fuel is composed of pulverized coal made of subbituminous coal, lignite, biomass, or the like.

  A heat transfer tube group 20 is provided in the boiler body 12 and the rear heat transfer section 14. The heat transfer tube group 20 is configured by arranging heat transfer tubes formed in an S shape or U shape in parallel. The heat transfer tube is made of a metal material such as stainless steel, for example. The heat transfer tube group 20 has a function as a heat exchanger such as a superheater or a reheater.

  When the air-fuel mixture is burned by the burner 16, a flame 22 is formed in the boiler body 12, and combustion gas is generated. An arrow G in FIG. 1 indicates the flow of combustion gas. The combustion gas flows from the lower part of the boiler body 12 toward the upper part, and moves from the boiler body 12 to the rear heat transfer unit 14. The combustion gas flows from the upper part to the lower part of the rear heat transfer unit 14 and is exhausted from the exhaust port 24 of the rear heat transfer unit 14. The combustion gas exchanges heat by passing through the heat transfer tube group 20. The direction in which the combustion gas flows is a direction that intersects the longitudinal direction of the heat transfer tube (for example, an orthogonal direction). The temperature of the combustion gas is about 800 ° C. at the upper part of the rear heat transfer unit 14 and is about 400 ° C. at the lower part of the rear heat transfer unit 14. The surface temperature of the heat transfer tube is about 650 ° C. at the upper part of the rear heat transfer unit 14 and is about 300 ° C. at the lower part of the rear heat transfer unit 14.

  When the combustion gas passes through the heat transfer tube group 20, combustion ash contained in the combustion gas adheres and accumulates on the wall surface of the heat transfer tube. More specifically, when the combustion gas flows in a direction crossing the longitudinal direction of the heat transfer tube (for example, an orthogonal direction), a Karman vortex or the like is formed around the heat transfer tube (for example, the downstream portion of the heat transfer tube). Therefore, it becomes easy for combustion ash to adhere to the wall surface of the heat transfer tube. The Reynolds number when the combustion gas passes through the heat transfer tube group 20 is, for example, about 36000. Thus, when combustion ash accumulates on the wall surface of the heat transfer tube, a bridge is formed between the heat transfer tube and the heat transfer tube. When a low-grade fuel such as subbituminous coal, lignite, or biomass is used as the fuel, a bridge is easily formed by adhering and depositing combustion ash composed of a low-melting-point compound portion or the like contained in the fuel. If such a bridge is formed, the heat transfer performance of the heat transfer tube may be reduced, the flow rate of the combustion gas around the heat transfer tube may be reduced, and the power generation efficiency of the boiler 10 may be reduced.

  The combustion ash bridge property evaluation apparatus and the combustion ash bridge property evaluation method in the heat transfer tube of the boiler 10 described below are for evaluating the bridge property of the combustion ash that is easily formed in such a heat transfer tube of the boiler 10. . In addition, about the boiler 10, it can evaluate also about another boiler, without being limited to coal fired boilers, such as a pulverized coal boiler.

  Next, the combustion ash bridge property evaluation apparatus in the heat transfer tube of the boiler 10 will be described. FIG. 2 is a diagram illustrating a configuration of the combustion ash bridge property evaluation apparatus 30. The combustion ash bridge property evaluation apparatus 30 includes a heating furnace 32, a fuel supply unit 34, a probe tube placement unit 36, and an observation unit 38.

  The heating furnace 32 includes a cylindrical ceramic tube 40 and a heater 42 provided around the ceramic tube 40. On one end side of the ceramic tube 40 in the longitudinal direction, an introduction portion 44 is provided for sealing outside air and introducing a mixture of fuel and air from the fuel supply portion 34 into the ceramic tube 40. The length of the ceramic tube 40 is preferably about 2000 mm, for example. The heater 42 may have a function of heating the ceramic tube 40 from 1350 ° C. to 1400 ° C. Thereby, even if it does not use a burner, by heating an air-fuel mixture from 1350 degreeC to 1400 degreeC, the flame 46 can be formed and an air-fuel mixture can be burned and the combustion gas for evaluation can be generated. Of course, a burner may be provided in the introduction portion 44 as an auxiliary. An arrow H in FIG. 2 indicates the flow of the evaluation combustion gas. The heating furnace 32 may be not only a vertical combustion furnace as shown in FIG. 2 but also a horizontal combustion furnace.

  The fuel supply unit 34 has a function of supplying a mixture of fuel and air to the heating furnace 32. The fuel supply unit 34 includes a feeder 48 and a pipe 50 that connects the feeder 48 and the heating furnace 32. The feeder 48 can be composed of, for example, a microfeeder. The micro-feeder is a feeder capable of rotating a disk carrying powdered fuel F with a motor and transporting the fuel F with air at a predetermined flow rate. The feeder 48 and the introduction portion 44 of the ceramic tube 40 that is one end side of the heating furnace 32 are connected by a pipe 50. As the fuel F, the same fuel as that used in the boiler 10 for evaluating the combustion ash bridge property may be used. For example, when evaluating the bridging property of combustion ash in a heat transfer tube of a pulverized coal boiler, pulverized coal composed of subbituminous coal, lignite, and biomass may be used as the fuel.

  The probe tube placement section 36 has a probe tube placement section main body 52 disposed on the other end side of the heating furnace 32 and a plurality of probe tubes 54 disposed on the probe tube placement section main body 52. The probe tube placement portion main body 52 may be formed of a glass material such as quartz glass so that the probe tube 54 can be observed from the outside. The probe tube placement portion main body 52 is provided with an introduction port 56 through which the evaluation combustion gas is introduced and an exhaust port 58 through which the evaluation combustion gas is exhausted. A space between the probe tube placement portion main body 52 and the ceramic tube 40 of the heating furnace 32 may be sealed with a seal member 60 in order to prevent leakage of the combustion gas for evaluation.

  The probe tube placement portion main body 52 is provided with a plurality of probe tubes 54. The probe tube 54 may be formed by simulating the heat transfer tube of the boiler 10. The probe tube 54 is formed in an elongated and hollow shape. The probe tube 54 is provided such that one end side of the probe tube 54 is inserted into the probe tube arrangement portion main body 52 and the other end side of the probe tube 54 is projected from the probe tube arrangement portion main body 52. The probe tube 54 is provided such that the longitudinal direction of the probe tube 54 is a direction (for example, an orthogonal direction) intersecting the direction of the flow of the evaluation combustion gas. A seal member 62 such as a gasket is provided between the probe tube placement portion main body 52 and the probe tube 54 in order to prevent leakage of the combustion gas for evaluation. The probe tube placement portion main body 52 may be provided with heating means (not shown) such as a heater. By providing a heating means (not shown) in the probe tube placement portion main body 52, the temperature of the combustion gas for evaluation introduced into the probe tube placement portion 36 can be adjusted. For example, in order to simulate the upper portion of the rear heat transfer section 14 of the boiler 10, when the temperature of the evaluation combustion gas is about 800 ° C., the evaluation combustion gas is heated by a heating means (not shown). What is necessary is just to be about 800 degreeC.

  FIG. 3 is a diagram showing the configuration of the probe tube 54. The probe tube 54 includes a probe tube main body 64 that is formed in an elongated and hollow shape. The probe tube main body 64 can be formed of a metal material such as stainless steel. The length of the probe tube main body 64 may be about 400 mm, for example. The probe tube main body 64 is inserted into the probe tube main body 64 and is provided with a cooling tube 66 for cooling by flowing a cooling medium such as water or air. The cooling pipe 66 is provided with a jet outlet for jetting the cooling medium in order to cool the probe pipe 54 by flowing the cooling medium through the gap between the probe pipe main body 64 and the cooling pipe 66. In addition, the arrow of FIG. 3 has shown the flow of the cooling medium. The cooling medium that has flowed into the gap between the probe tube main body 64 and the cooling tube 66 is discharged from a discharge port 68 provided in the probe tube main body 64. Thus, by cooling the probe tube 54 with the cooling medium, the surface temperature of the heat transfer tube of the boiler 10 can be simulated. For example, when the temperature difference between the combustion gas temperature and the surface temperature of the heat transfer tube is large as in the upper part of the rear heat transfer section 14 of the boiler 10, water may be used as the cooling medium. Further, when the temperature difference between the combustion gas temperature and the surface temperature of the heat transfer tube is small as in the lower part of the rear heat transfer unit 14 of the boiler 10, air may be used as the cooling medium. The probe tube main body 64 is provided with a temperature sensor 70 such as a thermocouple in order to measure the surface temperature of the probe tube 54.

  FIG. 4 is a diagram showing an arrangement configuration of the probe tube 54. D indicates the outer diameter of the probe tube 54. L indicates the pitch of the probe tube 54 (the distance between the centers of the probe tubes 54). For example, four probe tubes 54 are provided in the probe tube placement portion main body 52. The probe tubes 54 may be arranged in parallel along the direction of the evaluation combustion gas flow. By setting it as such a structure, the bridging property of the combustion ash which is easy to produce in the downstream part of a heat exchanger tube by the Karman vortex which arises when combustion gas passes the heat exchanger tube of the boiler 10 can be evaluated accurately. The probe tube 54 may be arranged in parallel in a direction (for example, an orthogonal direction) that intersects the direction of the evaluation combustion gas flow. By setting it as such a structure, the bridge property of the combustion ash of the direction (for example, orthogonal direction) which cross | intersects the direction of the flow of the combustion gas in the heat exchanger tube of the boiler 10 can be evaluated. The number of probe tubes 54 may be at least two, and is not limited to four as shown in FIG. 4, and may be three, six, or the like.

  The observation unit 38 is provided around the probe tube placement unit 36 and configured to be able to observe the probe tube 54. The observation part 38 can be comprised with a video camera etc., for example. By observing the probe tube 54 with a video camera or the like, it is possible to directly observe the adherence of the combustion ash to the probe tube 54, the formation process of the bridge, and the like, so that the bridging property of the combustion ash can be evaluated. The observation unit 38 is not limited to a video camera, and any unit that can observe the probe tube 54 may be used.

  The combustion ash bridge property evaluating apparatus 30 is configured to evaluate the combustion gas so that the number of straw hulls in the flow of evaluation combustion gas with respect to the probe tube 54 is the same as the number of straw hulls in the flow of combustion gas with respect to the heat transfer tube of the boiler 10 The Reynolds number and the outer diameter and pitch of the probe tube 54 are set. By making the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube 54 and the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10 the same, the form of the flow of the evaluation combustion gas with respect to the probe tube 54 Can be made the same as the form of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10. More specifically, the form of the wake of the probe pipe 54 (form of Karman vortex or the like) when the combustion gas for evaluation passes through the probe pipe 54 and the heat transfer pipe when the combustion gas passes through the heat transfer pipe of the boiler 10. The form of the wake (form of Karman vortex etc.) can be made the same. Thereby, since the form of the flow of the combustion gas with respect to the heat exchanger tube of the boiler 10 can be simulated at the laboratory level, the bridging property of the combustion ash can be accurately evaluated.

  The Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10 may be obtained by experiments or may be obtained from literature. When the Strouhal number St of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10 is obtained by experiment, the Karman vortex frequency F and the flow velocity U of the combustion gas are measured, and the outer diameter D of the heat transfer tube is used. What is necessary is just to calculate from the formula of St = F · D / U.

  When obtaining the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10 from the literature, for example, it can be obtained as follows. The Strouhal number is related to the Reynolds number of the fluid and the ratio of the outer diameter and pitch of the tube. Therefore, using the literature, the Strouhal number is estimated from the Reynolds number of the combustion gas of the boiler 10 and the ratio (l / d) of the outer diameter d and the pitch l of the heat transfer tube. Note that the Reynolds number of the combustion gas in the boiler 10 may be obtained in advance by experiments or analysis, for example. Such documents include G.I. Xu and Y. Zhou “Strohual Numbers in the Wake of Two Inline Cylinders”, Experiments in Fluids 37 (2004) pp. 199 248-256 (hereinafter referred to as Document 1) or the like can be used.

  Next, a method for setting the Reynolds number of the combustion gas for evaluation and the outer diameter D and pitch L of the probe tube 54 will be described. The Reynolds number of the evaluation combustion gas and the outer diameter D and pitch L of the probe tube 54 are such that the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube 54 is the straw of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10. It is set to be the same as the hull number. As described above, the Strouhal number is related to the Reynolds number of the fluid and the ratio of the outer diameter and pitch of the tube. Therefore, using the literature, from the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube 54, the Reynolds number of the evaluation combustion gas and the ratio (L / D) of the outer diameter D and the pitch L of the probe tube 54 Set. Such references include Tinghui Zheng, S .; K. Tang and Baolimg Fei, “ON THE FORCES AND STRONGHAL NUMBERS IN THE LOW REYNOLDS NUMBER WAKES OF. 33, no. 3, (2009) pp. 349-360 (hereinafter referred to as Document 2) or the like can be used. Then, the outer diameter D and the pitch L of the probe tube 54 may be set so that the ratio (L / D) of the set outer diameter D and pitch L of the probe tube 54 is obtained.

  Next, a combustion ash bridge property evaluation method using the combustion ash bridge property evaluation device 30 in the heat transfer tube of the boiler 10 will be described. FIG. 5 is a flowchart showing the configuration of the combustion ash bridge property evaluation method. The combustion ash bridge property evaluation method includes a step (S10) for obtaining a Strouhal number, a setting step (S12), an arrangement step (S14), and an observation step (S16).

  The step of obtaining the Strouhal number (S10) is a step of obtaining the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10. As described above, the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler 10 can be obtained from experiments, literature 1, and the like.

  In the setting step (S12), the evaluation combustion gas flow is adjusted so that the Strouhal number of the combustion gas flow with respect to the heat transfer tube of the boiler 10 is the same as the Strouhal number of the evaluation combustion gas flow with respect to the probe tube 54. In this step, the Reynolds number and the outer diameter and pitch of the probe tube 54 are set. As described above, the Reynolds number of the combustion gas for evaluation and the outer diameter D and pitch L of the probe tube 54 can be obtained from Document 2 and the like. Further, the Reynolds number of the combustion gas for evaluation is preferably 100 or more and 1000 or less. This is because when the Reynolds number of the combustion gas for evaluation is smaller than 100, it becomes difficult to supply the fuel contained in the air-fuel mixture. This is because when the Reynolds number of the combustion gas for evaluation is larger than 1000, a special feeder or the like may be required. The Reynolds number of the evaluation combustion gas can be changed, for example, by changing the inner diameter of the ceramic tube 40 of the heating furnace 32 or the flow rate of the evaluation combustion gas in the ceramic tube 40. In order to change the flow rate of the combustion gas for evaluation in the ceramic tube 40, for example, the flow rate of the air-fuel mixture when the air-fuel mixture is supplied from the fuel supply unit 34 into the ceramic tube 40 may be changed.

  The arrangement step (S14) is a step of arranging the plurality of probe tubes 54 having the outer diameter set in the setting step (S12) at the pitch set in the setting step (S12). The plurality of probe tubes 54 having the outer diameter D set in the setting step (S12) are arranged on the probe tube arrangement portion 36 at the pitch L set in the setting step (S12).

  The observation step (S16) is a step of observing the probe tube 54 by flowing the evaluation combustion gas from the direction intersecting the longitudinal direction of the probe tube 54 at the Reynolds number set in the setting step (S12). . An air-fuel mixture of fuel and air is supplied from the fuel supply unit 34 to the ceramic tube 40 of the heating furnace 32. The air excess ratio may be 1.5, for example. The amount of air is preferably 5 L / min, for example. When the air-fuel mixture is heated from 1350 ° C. to 1400 ° C. in the heating furnace 32, a flame 46 is formed, and a combustion gas for evaluation is generated. The evaluation combustion gas flows from the one end side to the other end side of the ceramic tube 40 at the Reynolds number set in the setting step (S12), and is introduced into the probe tube arranging portion 36. The evaluation combustion gas flows from the direction intersecting the longitudinal direction of the probe tube 54 (for example, the direction orthogonal thereto) at the Reynolds number set in the setting step (S12) and exhausted. The combustion gas for evaluation discharged from the exhaust port 58 of the probe tube placement unit 36 is conveyed to, for example, an exhaust gas facility or the like and subjected to exhaust gas treatment.

  By observing the probe tube 54 with an observation unit 38 such as a video camera, the combustion ash adheres to the surface of the probe tube 54 and forms a bridge directly when the combustion gas for evaluation passes through the probe tube 54. Can be observed. The time for evaluating the bridging property of the combustion ash by flowing the evaluation combustion gas may be, for example, 100 hours to 300 hours. Thus, since the bridging property of the combustion ash in the heat transfer tube of the boiler 10 can be evaluated at the laboratory level, it becomes possible to optimize the pitch of the heat transfer tube, and to take measures against the bridging of the combustion ash by installing a soot blower or the like. .

  As described above, according to the combustion ash bridge property evaluation apparatus in the heat transfer tube of the boiler having the above-described configuration, the heating furnace, the fuel supply unit that supplies the mixture of fuel and air from one end side of the heating furnace, and the heating furnace A probe tube arrangement portion arranged on the end side and arranged with a plurality of probe tubes provided extending in a direction intersecting with the flow direction of the evaluation combustion gas in which the air-fuel mixture burns, and an observation portion for observing the probe tube And the Reynolds number of the evaluation combustion gas and the probe so that the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube is the same as the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler. Since the outer diameter and pitch of the tube are set, the flow of combustion gas around the boiler heat transfer tube can be simulated at the laboratory level. Sex and can be accurately evaluated.

  According to the combustion ash bridge property evaluation method in the heat transfer tube of the boiler having the above-described configuration, the step of obtaining the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler, the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler, and In the setting step, the Reynolds number of the evaluation combustion gas, the outer diameter and the pitch of the probe tube are set so that the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube is the same. An arrangement process in which a plurality of probe tubes having a set outer diameter are arranged at a pitch set in the setting process, and a Reynolds in which the combustion gas for evaluation is set in the setting process from the direction intersecting the longitudinal direction of the probe pipe It is possible to simulate the flow of combustion gas around the heat transfer tube of the boiler at the laboratory level. The bridge of ash in the heat transfer tubes of the boiler can be accurately evaluated.

  A combustion ash bridge property evaluation test simulating superheater conditions of a pulverized coal boiler was conducted. For the combustion ash bridge property evaluation test, the same one as the combustion ash bridge property evaluation apparatus 30 shown in FIG. 2 was used. As the fuel, pulverized coal made of subbituminous coal was used.

  First, the Strouhal number of the flow of combustion gas to the heat transfer tube of the pulverized coal boiler was estimated. The above literature 1 was used for estimation of the Strouhal number. First, the Reynolds number of the combustion gas of the pulverized coal boiler and the ratio (l / d) of the outer diameter d and the pitch l of the heat transfer tube were determined. The Reynolds number of the combustion gas of the pulverized coal boiler was about 36000, and the ratio (l / d) between the outer diameter d and the pitch l of the heat transfer tube was about 5.0.

  FIG. 6 is a graph for explaining a method for estimating the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the pulverized coal boiler. The graph of FIG. 6 is the same as that of FIG. 6 (c) is cited. In FIG. 6, the Reynolds number (Re) is taken on the horizontal axis, the Strouhal number (St) is taken on the vertical axis, and the ratio (L / D) between the outer diameter D and the pitch L of the pipe is 3.5 to 5. 3 shows the relationship between the Reynolds number (Re) and the Strouhal number (St). From the graph of FIG. 6, when the Reynolds number of the combustion gas is about 36000 and the ratio (l / d) of the outer diameter (d) and the pitch (l) of the heat transfer tube is about 5.0, the Strouhal number is It is about 0.18. From this, the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the pulverized coal boiler was estimated to be about 0.18.

  Next, the Reynolds number of the combustion gas for evaluation, so that the Strouhal number of the flow of combustion gas for the heat transfer tube of the pulverized coal boiler is the same as the Strouhal number of the flow of evaluation gas for the probe tube, The outer diameter and pitch of the probe tube were set. For the setting of the Reynolds number of the combustion gas for evaluation and the outer diameter and pitch of the probe tube, the above-mentioned document 2 was used. FIG. 7 is a graph for explaining a method of setting the Reynolds number of the combustion gas for evaluation and the outer diameter and pitch of the probe tube. 7 is the same as FIG. 5 is quoted. In FIG. 7, the horizontal axis represents the ratio (L / D) of the outer diameter (D) and pitch (L) of the tube, the vertical axis represents the Strouhal number (St), and the Reynolds number (RE) ranges from 100 to 1000. The relationship between the ratio (L / D) of the outer diameter (D) and pitch (L) of the pipe and the Strouhal number (St) is shown.

  From the graph of FIG. 7, in order to set the Strouhal number to 0.18, the Reynolds number of the combustion gas for evaluation is set to about 500, and the ratio (L / D) of the outer diameter D and pitch L of the probe tube is about Set to 1.5. And in order to set the ratio (L / D) of the outer diameter D and pitch L of the probe tube to about 1.5, the outer diameter D of the probe tube is set to 17.3 mm, and the pitch L of the probe tube is set to 27.3 mm. It was. Four probe tubes were used, and the arrangement of the probe tubes was the same as that shown in FIG.

  Next, a combustion test was performed to observe the bridging property of the combustion ash in the probe tube. First, an air-fuel mixture of fuel and air was supplied from a fuel supply unit to a ceramic tube of a heating furnace. As the fuel, pulverized coal made of subbituminous coal was used. The excess air ratio (air ratio) was 1.5. The amount of air was 5 L / min. A combustion gas for evaluation was generated by heating the mixture to 1400 ° C. in a heating furnace. Then, the combustion gas for evaluation was flowed from one end side to the other end side of the ceramic tube, and was introduced into the probe tube placement portion. The Reynolds number of the combustion gas for evaluation was about 500. The evaluation combustion gas was flowed from a direction orthogonal to the longitudinal direction of the probe tube. The temperature of the combustion gas for evaluation was 700 ° C. The surface temperature of the probe tube was 500 ° C. The probe tube was exposed for 150 hours while flowing the evaluation combustion gas. The probe tube was observed with a video camera.

  FIG. 8 is a photograph showing the observation results of the probe tube after exposure for 150 hours. As shown in the photograph of FIG. 8, a bridge of combustion ash was confirmed between the probe tubes in the vertical direction along the flow direction of the combustion gas for evaluation. As a result, it was found that the bridging property of the combustion ash in the heat transfer tube of the boiler can be evaluated.

DESCRIPTION OF SYMBOLS 10 Boiler 12 Boiler main body 14 Rear heat transfer part 16 Burner 18, 50 Piping 20 Heat transfer tube group 22, 46 Flame 24, 58 Exhaust port 30 Combustion ash bridge property evaluation apparatus 32 Heating furnace 34 Fuel supply part 36 Probe pipe arrangement part 38 Observation Portion 40 Ceramic tube 42 Heater 44 Introduction portion 48 Feeder 52 Probe tube placement portion main body 54 Probe tube 56 Introduction port 60, 62 Seal member 64 Probe tube body 66 Cooling tube 68 Discharge port 70 Temperature sensor

Claims (6)

A combustion ash bridge property evaluation apparatus for a heat transfer tube of a boiler,
A heating furnace;
A fuel supply unit for supplying a mixture of fuel and air from one end of the heating furnace;
A probe tube disposition portion disposed on the other end side of the heating furnace and disposed with a plurality of probe tubes provided extending in a direction intersecting with a flow direction of the evaluation combustion gas in which the air-fuel mixture burns;
An observation unit for observing the probe tube;
With
The Reynolds number of the evaluation combustion gas and the probe so that the Strouhal number of the flow of the evaluation combustion gas with respect to the probe tube is the same as the Strouhal number of the flow of the combustion gas with respect to the heat transfer tube of the boiler. A combustion ash bridge property evaluation apparatus characterized in that an outer diameter and a pitch of a pipe are set. The combustion ash bridge property evaluation apparatus according to claim 1,
The said probe pipe arrangement | positioning part is a combustion ash bridge property evaluation apparatus characterized by the said some probe pipe being arrange | positioned along the direction of the flow of the said combustion gas for evaluation. The combustion ash bridge property evaluation apparatus according to claim 1 or 2,
The boiler is a pulverized coal boiler,
The combustion ash bridging property evaluation apparatus, wherein the fuel is subbituminous coal, lignite, or biomass. A combustion ash bridge property evaluation method for a heat transfer tube of a boiler,
A process for determining the Strouhal number of the flow of combustion gas to the heat transfer tube of the boiler;
The Reynolds number of the evaluation combustion gas and the probe tube so that the Strouhal number of the combustion gas flow with respect to the heat transfer tube of the boiler and the Strouhal number of the evaluation combustion gas flow with respect to the probe tube are the same. A setting step for setting the outer diameter and pitch of
An arrangement step of arranging a plurality of probe tubes having an outer diameter set in the setting step at a pitch set in the setting step;
An observation step of observing the probe tube by flowing the evaluation combustion gas at a Reynolds number set in the setting step from a direction intersecting the longitudinal direction of the probe tube;
A combustion ash bridge property evaluation method comprising: It is a combustion ash bridge property evaluation method according to claim 4,
In the arranging step, the plurality of probe tubes are arranged along a flow direction of the evaluation combustion gas. A combustion ash bridge property evaluation method according to claim 4 or 5,
The boiler is a pulverized coal boiler,
A combustion ash bridge property evaluation method, wherein the fuel for the evaluation combustion gas is subbituminous coal, lignite, or biomass.