JP3655482B2 - Fluid mixer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluid mixer that reduces an enthalpy deviation at a water wall outlet of a commercial and industrial boiler furnace, for example.
[0002]
[Prior art]
As shown in FIG. 8, a commercial or industrial coal-fired boiler has a furnace 6 that burns fuel and absorbs heat mainly by radiant heat transfer, and a convection heat transfer that distributes combustion gas to a heat transfer tube group. The horizontal heat transfer section 7 that absorbs the amount of heat.
[0003]
The furnace 6 is composed of a water wall made up of a large number of tubes, and receives a substantially uniform heat load in the majority of the basin. However, since the heat load locally increases in the vicinity of the burner 8 that is the combustion apparatus, a deviation occurs in the epitaxial of the fluid in the pipe at the outlet of the furnace water wall. If it is a conventional boiler, the dryness of the fluid at the furnace water wall outlet (= steam content) is as low as 0.5 to 0.7, the saturated state is maintained, and even if there is an empirical deviation, a temperature deviation will occur. There was no.
[0004]
On the other hand, by raising the dryness of the fluid at the outlet of the furnace water wall to near 1 and completing evaporation at the furnace water wall, the heat transfer tube group can be simplified and the furnace can be made compact. In such a furnace, when an enthalpy deviation occurs, the fluid having the higher enthalpy becomes superheated steam, so that the temperature becomes equal to or higher than the saturation temperature, resulting in a temperature difference from the fluid having the lower enthalpy. If the temperature difference exceeds a certain value, the thermal stress generated in the metal becomes excessive and exceeds the design strength of the furnace water wall, so cracks occur, and in the worst case, it is necessary to stop the operation.
[0005]
With conventional boilers, this problem does not occur at a constant load, so there is no need to take special measures. However, a temporary temperature difference occurs when the load increases or decreases, so the intermediate height of the furnace water wall There is also an example in which a furnace water wall intermediate header 10 as shown in FIG. 9 is provided at the site, and after mixing in the header 10, a flow is made to flow through the upper furnace water wall tube.
[0006]
Further, as shown in FIG. 10, the furnace water wall is divided into upper and lower parts, and a lower water wall pipe outlet pipe connected to the outlet of the heat transfer pipe constituting the lower furnace water wall 1 is provided and mixed by the mixer 11. After that, a structure is also adopted in which the water flows into the upper water wall pipe inlet pipe connected to the heat transfer pipe inlet constituting the upper furnace water wall 2.
[0007]
[Problems to be solved by the invention]
If it is a conventional type | mold boiler, in order to reduce a temperature difference, it designs so that the dryness of the fluid of a furnace water wall exit may be set to 0.5-0.7. If it does so, even if the imbalance of the heat absorption amount of a furnace water wall will arise, the dryness of the fluid of a furnace water wall exit will not exceed one. Accordingly, since the fluid in the pipe is always kept at the saturation temperature, there is no temperature difference.
[0008]
On the other hand, in a furnace designed so that the fluid dryness at the furnace water wall outlet is close to 1, when an unbalance of heat absorption occurs, the pipe with high heat absorption exceeds 1 and Above saturation temperature. On the other hand, tubes with low heat absorption always have a saturation temperature. Therefore, a temperature difference is generated between a pipe having a high heat absorption amount and a pipe having a low heat absorption amount.
[0009]
To solve this problem, the conventional method used in the furnace is, for example, to install a furnace water wall intermediate pipe at the intermediate height of the furnace water wall, mix and then flow to the upper water wall pipe The structure and the furnace water wall are divided into upper and lower parts, and a lower water wall pipe outlet is connected to the outlet of the heat transfer pipe that forms the lower furnace water wall. After mixing in the mixer, the upper furnace water wall It is difficult to keep the temperature difference below the design tolerance in the structure that flows to the upper water wall pipe inlet pipe connected to the heat transfer pipe inlet that constitutes.
[0010]
This is because the flow state of the fluid in the pipe changes depending on the dryness. If the flow rate is constant, the flow state in the pipe changes as shown in FIG. 11 due to the increase in dryness. In areas where the dryness is low, the liquid phase occupies a large proportion, resulting in a slag flow or bubble flow in which a liquid film is formed on the tube wall, whereas in areas where the dryness is high, the liquid phase becomes mist in the pipe. Resulting in a floating annular spray flow.
[0011]
Therefore, since the flow patterns are greatly different, it is impossible to apply the conventional method as it is. Actually, as a result of collecting data by applying the conventional design method, the metal temperature difference exceeds the design allowable value at the time of partial load as shown in FIG.
[0012]
The object of the present invention is to prevent the enthalpy deviation even in a furnace designed so that the degree of dryness of the fluid at the outlet of the furnace water wall is about 1, and to prevent the temperature difference between the tubes constituting the furnace water wall. It is to reduce and prevent failure of the furnace pressure resistance.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the present invention adopts the following configuration.
[0014]
A plurality of inflow side connecting pipes connected to the outlet pipe of the lower water wall pipe connected to the heat transfer pipe outlet of the lower furnace water wall, and an upper water wall pipe inlet pipe connected to the heat transfer pipe inlet of the upper furnace water wall A fluid mixer comprising an outflow side connecting pipe connected to the wall,
The fluid mixer has a main body formed in a cylindrical shape, and the inflow side communication pipe and the outflow side communication pipe are arranged radially around the main body,
The fluid mixer which makes the stage space | interval of the inflow side connecting pipe installed in the single stage or multiple stages in the said fluid mixer main body and the outflow side connecting pipe installed in multiple stages more than 4 times the internal diameter of a fluid mixer.
[0015]
In the fluid mixer, the interval between the stages of the outflow side connecting pipes installed in a plurality of stages is made smaller than the inner diameter of the fluid mixer.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The fluid mixer which concerns on embodiment of this invention is demonstrated below using FIGS. FIG. 1 shows a configuration example in which the fluid mixer according to the present embodiment is applied to a supercritical pressure transformer once-through boiler. FIG. 2 is an enlarged view of the fluid mixer shown in FIG. FIG. 3 is a cross-sectional view of FIG. 2 and shows a simplified structure of the fluid mixer. FIG. 3 illustrates the inner diameter D of the fluid mixer, the interval L1 between the inflow side communication tube and the outflow side communication tube, and the interval L2 between the outflow side communication tubes. Here, 1 is a lower furnace water wall, 2 is an upper furnace water wall, 3 is a fluid mixer, 4 is an inflow side communication pipe, and 5 is an outflow side communication pipe.
[0017]
First, as shown in FIG. 1, the boiler of the present embodiment is configured with a water wall at the periphery, and the water wall is vertically divided at a position higher than the middle portion of the height. Here, the lower furnace water wall 1 is composed of a spiral wall with inclined heat transfer tubes, and the upper furnace water wall 2 is composed of an upper water wall whose heat transfer tubes are vertical. The spiral wall and the upper water wall are composed of a large number of heat transfer tubes, but have a structure in which about several tens of tubes are joined together by a header.
[0018]
An inflow side connecting pipe 4 is connected to the outlet header of the lower furnace water wall 1 connected to the spiral wall side, and the connecting pipe 4 is connected to the fluid mixer 3. As shown in FIG. 2, the fluid mixer 3 has a cylindrical shape, and a plurality of inflow side communication tubes 4 and outflow side communication tubes 5 are arranged radially around the periphery. The fluid that has passed through the inflow side connecting pipe 4 extending from the lower furnace water wall 1 is mixed in the fluid mixer 3 and distributed to the outflow side connecting pipe 5 connected to the inlet header of the upper furnace water wall 2 to flow out. To do. In the boiler of this embodiment, the inner diameter D of the mixer is set to 200 mm, and the interval L1 between the inflow side connecting pipe and the outflow side connecting pipe is set to 4 times the fluid mixer inner diameter.
[0019]
Next, functions and operations of the present invention that accompany the adoption of the embodiment of the present invention will be described below. According to the embodiment of the present invention, since the inflow side communication pipe 4 and the outflow side communication pipe 5 are arranged radially around the cylindrical fluid mixer 3, it is possible to reduce the enthalpy deviation in the circumferential direction, Since no swirling occurs, erosion inside the fluid mixer 3 can be prevented. Here, the mist flowing in from the inflow side connecting pipe 4 is entrained in the gas phase and has an inertial force, so that it cannot be uniformly dispersed inside the fluid mixer 3, and the center of the fluid mixer 3 as shown in FIG. Dense to the department.
[0020]
However, the dense mist is gradually diffused due to the frictional resistance from the gas phase and flows out from the outflow side connecting pipe as shown in FIG. Therefore, as a result of performing experiments by variously changing the distance L1 between the inflow side communication pipe and the outflow side communication pipe, the distance L1 between the inflow side communication pipe and the outflow side communication pipe is set to be four times or more the fluid mixer inner diameter D. Thus, it was found that the dispersion ratio of the mist on the upper and lower stages on the outflow side was almost constant, and the enthalpy deviation was significantly below the allowable value under this condition. The obtained measurement results are shown in FIG.
[0021]
In FIG. 6, the horizontal axis represents L1 / D, and the vertical axis represents the enthalpy deviation. When L1 / D is 4 or more at both 50% load and 30% load, the enthalpy deviation is less than the allowable value.
[0022]
By suppressing the enthalpy deviation below the allowable value, even if the internal fluid of the lower furnace water wall 1 has an enthalpy deviation and partially becomes superheated steam, the enthalpy is mixed in the fluid mixer 3 and the upper furnace water wall 2 Enthalpy deviation can be reduced at the entrance. Therefore, since the temperature difference between the heat transfer tubes at the outlet of the upper furnace water wall 2 can be greatly reduced, it is possible to suppress the thermal stress generated in the metal to be lower than the design strength of the furnace water wall. As a result, the life of the furnace is extended, and damage to the furnace water wall can be prevented.
[0023]
FIG. 7 shows the experimental results when another embodiment of the present invention is used. In this embodiment, the distance L1 between the inflow side communication pipe and the outflow side communication pipe is secured at least four times the fluid mixer inner diameter D, and the distance L2 between the outflow side communication pipes is made smaller than the fluid mixer inner diameter D. It is. According to FIG. 7, by setting L2 / D to 1 or less, the enthalpy deviation is less than the allowable value at both 50% load and 30% load. With such a configuration, the upper and lower stages of the outflow side connecting pipe can be installed in a region where the pressure is substantially equal. Therefore, mist is distributed to the upper and lower stage pipes of the outflow side connecting pipe, and the enthalpy deviation can be further reduced.
[0024]
As described above, the embodiment of the present invention includes the following configurations and operations and effects.
[0025]
By arranging the inflow side communication pipe and the outflow side communication pipe radially around the cylindrical fluid mixer, it is possible to reduce the enthalpy deviation in the circumferential direction and at the same time, no swirling occurs. Erosion can be prevented. Furthermore, by setting the interval between the inflow side communication pipe and the outflow side communication pipe to be at least four times the inner diameter of the fluid mixer, it is possible to appropriately distribute the flow rate of mist to the upper and lower stages of the outflow side. Therefore, there is an enthalpy deviation in the internal fluid of the lower furnace water wall heat transfer tube, and even if it partially becomes superheated steam, enthalpy mixing is performed in the fluid mixer, and the enthalpy deviation is reduced at the upper furnace water wall heat transfer tube inlet it can.
[0026]
Therefore, since the temperature difference between the heat transfer tubes at the upper furnace water wall heat transfer tube outlet can be reduced, it is possible to suppress the thermal stress generated in the metal below the design strength of the furnace water wall. As a result, the life of the furnace is extended, and damage to the furnace water wall can be prevented.
[0027]
Further, by making the intervals between the plurality of stages of the outflow side communication pipes smaller than the inner diameter of the fluid mixer, it is possible to further optimize the flow distribution of mist to the upper and lower stages of the outflow side communication pipes.
[0028]
【The invention's effect】
By applying the present invention to a boiler furnace, even if there is an enthalpy deviation in the internal fluid of the lower furnace water wall heat transfer tube and it becomes partially superheated steam, enthalpy mixing is performed in the fluid mixer, and the upper furnace water wall The enthalpy deviation can be reduced at the heat transfer tube inlet, and the temperature difference between the heat transfer tubes at the upper furnace water wall heat transfer tube outlet can be reduced, so that the thermal stress generated in the metal can be kept below the design strength of the furnace water wall. It becomes. As a result, the life of the furnace is extended, and damage to the furnace water wall can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example in which a fluid mixer according to an embodiment of the present invention is applied to a supercritical pressure transformer once-through boiler.
FIG. 2 is an enlarged view of the fluid mixer shown in FIG.
3 is a cross-sectional view of FIG. 2 showing a simplified structure of the fluid mixer. FIG.
FIG. 4 is a diagram showing a mist concentration distribution in the fluid mixer.
FIG. 5 is a diagram schematically showing the flow state of mist inside the fluid mixer.
FIG. 6 is a diagram showing an example of measured values of enthalpy deviation obtained by applying the present invention to a boiler furnace.
FIG. 7 is a diagram showing experimental results obtained when another embodiment of the present invention is applied.
FIG. 8 is a diagram illustrating an outline of a business boiler.
FIG. 9 is a diagram showing an example in which an intermediate header is employed in the prior art.
FIG. 10 is a diagram showing an example in which a mixer according to the prior art is employed.
FIG. 11 is a diagram schematically showing the flow state of the fluid in the pipe.
FIG. 12 is a diagram showing a metal temperature difference when the prior art is applied to a furnace designed so that the fluid quality at the reactor water wall outlet is close to 1.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lower furnace water wall 2 Upper furnace water wall 3 Fluid mixer 4 Inflow side communication pipe 5 Outflow side communication pipe 6 Furnace 7 Horizontal installation heat-transfer pipe part 8 Burner 9 Furnace water wall 10 Intermediate header 11 Mixer

Claims (2)

A plurality of inflow side connecting pipes connected to the outlet pipe of the lower water wall pipe connected to the heat transfer pipe outlet of the lower furnace water wall, and an upper water wall pipe inlet pipe connected to the heat transfer pipe inlet of the upper furnace water wall An outflow side connecting pipe connected to the main body, wherein the fluid mixer has a main body formed in a cylindrical shape, and the inflow side connecting pipe and the outflow side connecting pipe are provided around the main body. Arranged radially,
A step interval between the inflow side connecting pipes installed in a single stage or a plurality of stages in the fluid mixer main body and the outflow side connecting pipes installed in a plurality of stages is made four times or more the inner diameter of the fluid mixer. Fluid mixer. The fluid mixer according to claim 1.
The fluid mixer characterized by making the space | interval between the stages of the said outflow side connecting pipe installed in multiple stages smaller than the said fluid mixer internal diameter.

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