JPH0616243Y2 - Natural circulation boiler steam drum - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention relates to a steam drum for a natural circulation type boiler.

(Prior Art) Conventionally, the steam drum for a natural circulation type boiler shown in FIG. 3 has been used. In the heat transfer tube 1, a part of the saturated water that receives the heat of the high-temperature exhaust gas G and flows from the water drum 4 into the heat transfer tube 1 becomes steam and flows in a gas-liquid two-phase flow state. Further, in the downcomer pipe 3, almost saturated water flows. For this reason, a density difference occurs between the fluids of the heat transfer tube 1 and the downfall tube 3, and this density difference serves as a circulating force to move up the heat transfer tube 1 as a gas-liquid two-phase fluid, and thus the steam drum 2, the downfall tube 3, It circulates in the order of the drum 4 and returns to the heat transfer tube 1 again. The flow in the steam drum 2 will now be described in a little more detail. The gas-liquid two-phase fluid flowing from the heat transfer tube 1 into the outer drum body 5 is a flow path formed between the outer drum body 5 and the inner drum body 6. 7 and flows from here to the cyclone separators 8a and 8b, respectively. The gas-liquid two-phase fluid is separated into steam and saturated water by the cyclone separators 8a and 8b by centrifugal force. Steam is more scrubber 9
, Fine water droplets are removed and sent to a steam turbine (not shown) or a superheater (not shown) through the steam outlet pipe 10. On the other hand, the saturated water separated in the cyclone separators 8a and 8b gathers above the drum inner barrel 6 and is sent to the downcomer pipe 3.

(Problems to be solved by the invention) By the way, the high-temperature exhaust gas G is generated by the heat transfer tubes 1 arranged in rows.
The heat exchange with the gas-liquid two-phase fluid is made during the passage of the gas, so that the temperature of the hot exhaust gas G gradually decreases. An example of the test results for this is shown in FIG. The horizontal axis is each position of the heat transfer tubes arranged in a row along the flow of the high-temperature exhaust gas G, and in this case, the heat transfer tube has the first row at the position where the gas flows in, and the tenth row before the outflow. count. The hot exhaust gas temperature is about 420 ° C near the first row heat transfer tubes, but about 180 ° C in the tenth row heat transfer tubes. Therefore, the heat transfer amount in the heat transfer tubes in the first row is the largest.

Next, the circulation action of the gas-liquid two-phase fluid passing through the water drum 4 and the steam drum 2 will be described with reference to FIG. The horizontal axis shows the flow rate and the vertical axis shows the pressure difference. The number of rows of heat transfer tubes is five. As shown in Fig. 3, a heat transfer tube that is heated and a downcomer that is not heated (usually not heated,
When placed in the combustion gas passage or the like, it is heated. However, the amount of heat exchange is small and almost no steam is generated in the downcomer. ) And a circulation circuit are formed.
It should be noted that the circulation circuit also includes cyclone separators 8a and 8b installed on the drum inner case 6. The amount of pressure loss in the cyclone separators 8a and 8b is the largest factor that impedes circulation in the circulation circuit. And cyclone separator
The pressure loss of 8a and 8b increases in proportion to almost the square of the flow rate flowing through the cyclone separator.

The so-called flow rate characteristic, which shows the relationship between the circulating flow rate of the heat transfer tubes in each row and the pressure difference between the heat transfer tubes in each row (difference between the water drum pressure and the cyclone separator inlet pressure), is the flow rate characteristic in FIG. It is shown by curves G1, G2, G3, G4, G5. Here, G1 is a flow rate characteristic curve flowing through the heat transfer tube installed on the high temperature exhaust gas upstream side, and G5 is a flow rate characteristic curve flowing through the heat transfer tube installed on the high temperature exhaust gas downstream side. Then, the sum of the flow rate characteristic curves G1 to G5 of each row represents the flow rate of all the heat transfer tubes. The flow characteristic curve for this all heat transfer tube is shown by ΣGi. Further, considering the pressure loss generated in the cyclone separator that is in communication with the flow path, the flow rate characteristic of flowing through all the heat transfer tubes eventually becomes a curve ΣG.

On the other hand, the flow rate characteristic flowing through the downcomer pipe is shown by a curve Gd represented by a broken line in the figure in consideration of the pressure difference from the water drum internal pressure to the steam drum internal pressure in addition to the flow rate flowing through the downcomer pipe. The reason why the curve Gd becomes a downward-sloping curve is that the flow resistance of the downcomer pipe increases due to the increase in flow rate.

By the way, since the pressure difference and the flow rate between the water drum and the steam drum are naturally equal on the heat transfer tube side and the downfall tube side, the pressure difference and the flow rate obtained at the intersection a of the heat transfer tube side flow rate characteristic ΣG and the downfall tube side flow rate characteristic Gd. Will be shown.

The flow rate of the heat transfer tubes in each row at this time can be obtained as follows. First, point b is obtained by subtracting the pressure loss of the cyclone separator from point a. This pressure difference at point b is the pressure difference between the water drum internal pressure and the cyclone separator inlet pressure, and this pressure difference is ΔP3. The flow rate of the heat transfer tubes in each row is determined by the intersections c, d, e, f, g of the pressure difference ΔP3 and the flow rate characteristic curves G1 to G5 of the heat transfer tubes in each row. Of these flow rate characteristic curves G1 to G5, the flow rate characteristic G5 that flows through the heat transfer tubes in the final row has a small intersection point g, as can be understood from the figure, and due to slight fluctuations in the heating amount and other factors. , The heat transfer tube flow may be trapped. Therefore, the flow of the heat transfer tubes in the last row becomes unstable,
There is a risk of damage to the heat transfer tube due to thermal fatigue.

Therefore, an object of the present invention is to prevent an unstable flow of the gas-liquid two-phase fluid passing through the heat transfer tubes installed on the downstream side of the high-temperature exhaust gas among the gas-liquid two-phase fluids flowing through the heat transfer tubes in each row. To provide a steam drum for a natural circulation boiler.

[Constitution of device]

(Means for Solving the Problem) A steam drum for a natural circulation type boiler according to the present invention is a horizontally long cylinder steam drum, and this steam drum is provided with a drum inner cylinder and a drum inner cylinder arranged concentrically. A cyclone separator is provided on the drum inner body, and is connected to the cyclone separator, and is connected to the flow passage formed between the drum outer body and the drum inner body, and this flow passage, and the gas-liquid two-phase fluid from the water drum is supplied. The heat transfer tube is provided with a heat transfer tube that guides the heat transfer tube, and the heat transfer tube is arranged in a row along and across the flow of the high-temperature exhaust gas.
A partition plate for partitioning into the second flow path and the second flow path is provided, and the ascending force of the steam generated by the heat transfer tube installed on the upstream side of the high-temperature exhaust gas in the first flow path of the divided flow paths. Is used to guide the gas-liquid two-phase fluid from the water drum, while using the suction force of the steam generated by the heat transfer tube installed relatively upstream of the high-temperature exhaust gas into the divided second flow path. It is characterized in that the gas-liquid two-phase fluid that remains in the heat transfer tube installed downstream of the high-temperature exhaust gas is introduced.

(Operation) In the above-described configuration, the partition plate is provided in the flow path to provide the first flow path and the second flow path
Of the high temperature exhaust gas is connected to the first flow path, and the heat transfer tubes of the high temperature exhaust gas are installed upstream and downstream of the high temperature exhaust gas are connected to the second flow path. Therefore, the flow of the gas-liquid two-phase fluid in each row of heat transfer tubes becomes good. That is, the heat transfer tube communicating with the first flow path receives the heat of the high-temperature exhaust gas to generate steam, and the ascending force of this steam allows the gas-liquid two-phase fluid to flow favorably to the first flow path.

Further, among the heat transfer tubes communicating with the second flow path, the heat transfer tubes installed relatively upstream of the high-temperature exhaust gas also utilize the ascending force of the vapor as described above to improve the flow of the gas-liquid two-phase fluid. There is.
However, since the heat transfer pipe installed on the downstream side of the high-temperature exhaust gas receives a low amount of heat from the high-temperature exhaust gas, the amount of generated steam is small, and the power of rising steam cannot be expected. However, in the second flow path, steam has already flowed from the heat transfer tube installed relatively upstream of the high-temperature exhaust gas, and this steam serves as a suction force and remains in the heat transfer tube installed downstream of the high-temperature exhaust gas. Withdrawing the gas-liquid two-phase fluid, the flow of the gas-liquid two-phase fluid is improved.

As described above, in the steam drum for the natural circulation type boiler according to the present invention, no matter whether the heat transfer tubes are installed on the upstream or downstream side of the hot exhaust gas, the gas and liquid from all the heat transfer tubes to the first flow path and the second flow path are Since the flow of the two-phase fluid becomes good, it is possible to secure stability in terms of material strength and weakness in combination with the generation of a large amount of vapor.

(Embodiment) An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 2 indicates a steam drum, which is a horizontally long cylinder. The steam drum 2 is provided with an inner drum body 6 coaxially arranged with an outer drum body 5. A pair of cyclone separators 8 is provided on the drum inner body 6.
a and 8b are provided, and a pair of these cyclone separators 8
A flow path S is provided between the outer drum body 5 and the inner drum body 6 by communicating with a and 8b.
Are formed.

A partition plate 11 is provided in the flow path S, and the partition plate 11 divides the first flow path 12 and the second flow path 13 from each other.
The first flow path 12 includes a heat transfer tube 1A connected to the water drum 4. The heat transfer tube 1A is located upstream of the high-temperature exhaust gas G, and a plurality of tubes are installed in a row across the flow. There is. The second flow path 13 includes heat transfer tubes 1B and 1C connected to the water drum 4,
These heat transfer tubes 1B and 1C are installed in a row from the relatively upstream side of the high-temperature exhaust gas G toward the downstream side. A downfall pipe 3 that connects the steam drum 2 and the water drum 4 is provided on the most downstream side of the high-temperature exhaust gas G. Note that reference numeral 9 indicates a scrubber, and reference numeral 10 indicates a steam outlet pipe. The steam from which fine water droplets have been removed from the scrubber 9 is sent to a steam turbine (not shown) via the steam outlet pipe 10. There is.

The circulation action of the gas-liquid mixed vapor in the natural circulation boiler having the above configuration will be described with reference to FIG. Similar to FIG. 5, the flow rate characteristics of the heat transfer tubes in each row are shown by curves G1 to G5. Characteristic curve ΣGa based on total flow rate of two rows of heat transfer tubes installed upstream of high temperature exhaust gas
And the characteristic curve ΣGb based on the total flow rate of the three rows of heat transfer tubes installed on the downstream side of the high-temperature exhaust gas, the cyclone separator 8 installed at the outlets of the first flow path 12 and the second flow path 13 is obtained.
Characteristic curves h and i are obtained by adding the pressure loss components a and 8b. In this case, the pressure loss of the cyclone separators 8a and 8b is slightly larger in the characteristic curve h than in the case of FIG. 5, and smaller in the characteristic curve i than in the case of FIG. The characteristic curve j on the heat transfer tube side is represented by the sum of the characteristic curves h and i.

On the other hand, the characteristic curve on the downcomer side is indicated by the curve Gd indicated by the same broken line as in FIG. In the steady state, the pressure difference between the water drum internal pressure and the steam drum internal pressure and the flow rate are naturally equal on both the heat transfer tube side and the downfall tube side, so the intersection point between the heat transfer tube side flow rate characteristic j and the downfall tube side flow rate characteristic Gd. K is the pressure difference and the flow rate required. The flow rate of the heat transfer tubes in each row at this time can be obtained as follows. That is, first, the pressure difference at the point k is set to ΔP4, and the intersections 1 and m of this pressure difference ΔP4 and the characteristic curves h and i are obtained. The flow rates indicated by the intersections 1 and m are the first flow path 12 and the second flow path 13
It shows the flow rate through the. Next, points n and o are obtained by subtracting the pressure loss at the cyclone separators 8a and 8b from the intersections l and m. The pressure difference at the points n and o is the height between the water drum 4 and the first flow passage 12 and the second flow passage 13, which are designated as ΔP5 and ΔP6, respectively. The flow rate of the heat transfer tube 1A installed on the upstream side of the high-temperature exhaust gas is determined by the intersection points p and q of the pressure difference ΔP5 and the flow rate characteristic curves G1 and G2. Also,
The flow rate of the high temperature exhaust gas in the heat transfer tube 1B installed relatively upstream and the heat transfer tube 1C installed downstream thereof is a pressure difference Δ6 and a flow rate characteristic curve.
It is determined by the intersection points r, s, and t with G3, G4, and G5. Here, comparing the flow rate G5 of the heat transfer tubes 1C in the final row with FIG. 5 and FIG. 2 according to the present invention, it is apparent that the pressure difference and the flow rate are both increased. The factors that cause such events are
The suction force of the steam flowing from the heat transfer tube 1B installed relatively upstream of the high temperature exhaust gas to the second flow path 13 acts to raise the gas-liquid two-phase fluid remaining in the heat transfer tube 1C installed downstream of the high temperature exhaust gas. Is believed to be giving. Therefore, the flow of the heat transfer tube can always be an upward flow.

In this way, by configuring the gas-liquid two-phase fluid generated in each heat transfer tube 1A, 1B, 1C to flow through paths independent from each other, all of the gas-liquid two-phase fluid flowing in each row heat transfer tube It can be an upflow, and an unstable flow state can be avoided.

[Effect of device]

As described above, according to the present invention, the flow passage formed between the outer drum body and the inner drum body has the first flow passage communicating with the heat transfer pipe installed on the upstream side of the high temperature exhaust gas and the relatively high temperature exhaust gas. Since the partition plate that separates the second flow path communicating with the heat transfer tubes installed on the upstream side and the downstream side from each other is provided, the flow of the gas-liquid two-phase fluid passing through the heat transfer tubes in each row is entirely changed to the first flow path. Further, it is possible to satisfactorily lead to the second flow path, so that the heat transfer tubes in each row have an excellent effect of preventing damage due to thermal fatigue or the like.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a steam drum for a natural circulation type boiler according to the present invention, FIG. 2 is a view for explaining a water circulation action of the natural circulation type boiler of the present invention, and FIG. FIG. 4 is a sectional view showing a steam drum, FIG. 4 is a characteristic diagram showing a relationship between a heat transfer tube position and a gas temperature, and FIG. 5 is a view for explaining a water circulation action of a conventional natural circulation boiler. 1A, 1B, 1C ...... Heat transfer tube 2 ...... Steam drum 3 ...... Precipitation tube 4 ...... Water drum 5 …… Drum outer body 6 …… Drum inner body 8a, 8b …… Cyclone separator 11 …… Partition plate 12… … First flow path 13 …… Second flow path S …… Flow path

Claims (1)

[Scope of utility model registration request] 1. A horizontally elongated steam drum, wherein the steam pipe drum is provided with a drum inner cylinder having a concentric arrangement on an outer drum body, a cyclone separator is provided on the drum inner cylinder, and the cyclone separator is electrically connected to the cyclone separator. , The drum outer body,
A flow path formed between the drum inner shell and a heat transfer tube communicating with the flow path and guiding the gas-liquid two-phase fluid from the water drum are provided, while the heat transfer tube is along the flow of the high-temperature exhaust gas, and In a steam drum for a natural circulation type boiler installed in a row across, a partition plate that divides the above flow passage into a first flow passage and a second flow passage is provided, and among the divided flow passages, In the first flow path, the vapor-liquid two-phase fluid from the water drum is guided by using the ascending force of the steam generated by the heat transfer tube installed on the upstream side of the high-temperature exhaust gas, while the second flow section is divided. The gas-liquid two-phase fluid remaining in the heat transfer pipe installed on the downstream side of the high-temperature exhaust gas is guided to the passage by using the suction force of the steam generated by the heat transfer pipe installed on the relatively upstream side of the high-temperature exhaust gas. A steam drum for natural circulation type boilers.