JP7594982B2 - Steam dryer - Google Patents

Description

The present invention relates to a steam dryer.

The steam-water separation system of a boiling water reactor typically comprises a gas-liquid separator that separates steam and liquid from the mixed flow of steam and liquid generated in the reactor core, and a steam dryer that removes liquid droplets from the wet steam separated by the gas-liquid separator. The steam that has passed through the steam dryer and from which liquid droplets have been removed is sent from inside the reactor through a pipe to a steam turbine, where it rotates the turbine blades.

In a steam dryer, the wet steam containing liquid droplets released from the gas-liquid separator is guided by a hood plate and the flow rate is distributed by a perforated plate, after which the liquid droplets contained in the wet steam are separated in a steam flow path formed between two adjacent corrugated plates.

In the steam flow path, the liquid droplets contained in the wet steam stick to the auxiliary plate attached to the corrugated sheet and become a liquid film, then flow into the slits formed in the auxiliary plate due to gravity and shear forces generated by the steam flow. The liquid droplets that flow into the slits become liquid and descend in the drain flow path (liquid film discharge flow path) formed by the auxiliary plate and the corrugated sheet, and are separated from the wet steam (for example, Patent Document 1).

The cross-sectional shape of this steam dryer does not change significantly from top to bottom, so shortening it has little effect on the basic structure. For this reason, it is thought that shortening the steam dryer will make the pressure vessel smaller and reduce the manufacturing costs of the reactor.

JP 2004-205302 A

However, shortening the length of the steam dryer also shortens the steam and drain passages, raising concerns that the performance of separating liquid droplets may decrease. In other words, if the mass flow rate of steam released from the steam-water separator remains the same as before the shortening, the mass flow rate of steam passing through the steam passage of the steam dryer per unit height increases relatively compared to before the shortening. As a result, the amount of liquid droplets flowing into the slits per unit height increases relatively, and the amount of liquid descending the drain passage per unit height increases relatively.

On the other hand, shortening the drain passage can cause liquid that is once contained in the drain passage and drops down to overflow from the slit at the bottom of the drain passage into the steam passage, where it turns into droplets due to the steam flow and is re-scattered into the steam passage, potentially increasing the moisture content of the steam sent from the steam dryer to the steam turbine.

When the moisture content of the steam flowing into a steam turbine from a steam dryer is higher than the upper limit (required value), erosion (abrasive corrosion) occurs on the turbine blades, making it difficult to maintain the integrity of the steam turbine.

The object of the present invention is to provide a steam dryer that can prevent droplets that flow from the steam flow path through the slits into the drain flow path and turn into liquid and drop down from being re-scattered from the slits into the steam flow path in a shortened steam dryer.

In order to achieve the above-mentioned object, the present invention comprises a drain flow path formed between at least two plates standing with a gap between them, a slit provided in one of the at least two plates connecting the drain flow path with a steam flow path, a horizontal plate spanning between the at least two plates and dividing an area of the drain flow path close to the slit into upper and lower parts, and a vertical plate spanning between the at least two plates , extending downward from an end of the horizontal plate located opposite the slit with the end serving as an upper end , and dividing the drain flow path.

According to the present invention, by dividing the drain passage with horizontal and vertical plates, it is possible to prevent liquid droplets that fall inside the drain passage from being re-scattered into the steam passage, and even if the length of the steam dryer is shortened, an increase in the moisture content of the steam released from the steam dryer can be suppressed. Problems, configurations, and effects other than those described above will be made clear by the explanation of the embodiments below.

1 is a vertical cross-sectional view showing an internal structure of a boiling water reactor incorporating a steam dryer according to a first embodiment of the present invention. FIG. 2 is a perspective view, partly in section, showing in detail the arrangement and structure of the steam dryer according to the first embodiment of the present invention; FIG. 2 is a perspective view, partly in section, showing in detail the structure of one row of a plurality of steam dryer units included in the steam dryer according to the first embodiment of the present invention; FIG. 2 is an enlarged perspective view showing a portion of a steam flow path provided in the steam dryer unit of the steam dryer according to the first embodiment of the present invention. 5 is a view taken along the line AA in FIG. 4. 5 is a view taken along the line BB in FIG. 4. 6 is a view taken along the line CC in FIG. 5 . FIG. 2 is an enlarged perspective view illustrating a state in which liquid droplets are separated from wet steam in the steam dryer unit of the steam dryer according to the first embodiment of the present invention. 1 is a graph showing the flow rate and humidity of steam at an inlet required for a steam dryer such that the humidity of the steam at an outlet satisfies the requirements of a steam turbine. FIG. 11 is an enlarged perspective view showing a portion of a steam flow path provided in a steam dryer unit of a steam dryer according to a second embodiment of the present invention. 11 is a view taken along the line A1-A1 of FIG. 10. 11 is a view taken along the line A2-A2 of FIG. 10. 11 is a view taken along the line A3-A3 of FIG. 10. 11 is a view taken along the line BB in FIG. 10 . 12 is a view taken along the line CC in FIG. 11 . 1A is a schematic diagram of a vertical cross section of a steam dryer unit of a steam dryer according to a second embodiment of the present invention, and FIG. 1B is a graph showing the relationship between the height of an inlet of a steam flow passage and the flow velocity of wet steam.

The configuration and operation of the steam dryer according to the first and second embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals in each drawing indicate the same parts.

First Embodiment
FIG. 1 is a vertical cross-sectional view showing the internal structure of a boiling water reactor in which a steam dryer according to this embodiment is incorporated.

The boiling water reactor 100 having the steam dryer 10 according to this embodiment circulates the cooling water (reactor water) in the reactor pressure vessel 110 between the reactor core 120 and the downcomer 130 by an internal pump 140.

During this circulation, the reactor water is heated in the reactor core 120 and becomes a mixed fluid of water and steam. This mixed fluid flows into the steam separator 150 located directly above the reactor core 120, where it is centrifuged to separate water and wet steam.

The wet steam separated by the steam-water separator 150 is discharged to the steam dryer 10 arranged above the steam-water separator 150. The water separated by the steam-water separator 150 is discharged from the steam-water separator 150 and descends to the downcomer 130, where it becomes reactor water that circulates again through the reactor core 120. The wet steam from which the water has been separated by the steam-water separator 150 has liquid droplets separated by the steam dryer 10.

Figure 2 is a perspective view with a portion cut away to show in detail the structure of the steam dryer 10 according to this embodiment.

The steam dryer 10 has a cylindrical skirt 11 that covers the side of the steam-water separator 150, a disk-shaped isolation wall 12 that is placed on the skirt 11 and covers the upper part of the steam-water separator 150, and multiple (six rows in this embodiment) steam dryer units 13 that are placed on the isolation wall 12 and whose lower ends communicate with the inside of the skirt 11 through the openings in the isolation wall 12.

The skirt 11 and the isolation wall 12 allow the wet steam discharged from the steam separator 150 to be efficiently guided to the steam dryer unit 13.

Figure 3 is a perspective view, partially cut away, showing in detail the structure of one row of multiple steam dryer units 13 in the steam dryer 10 according to this embodiment.

The steam dryer unit 13 has a food plate 1 that introduces wet steam WS containing droplets released from the steam separator 150, a perforated plate 2 that distributes the flow rate of the wet steam introduced into the food plate 1, and a plurality of corrugated plates 3 arranged perpendicular to the perforated plate 2, and the gap between two adjacent corrugated plates 3 of the plurality of corrugated plates 3 forms a steam flow path 4.

In addition, at the bottom of the steam dryer unit 13, there is a drain trough 14 that collects the liquid descending from the steam dryer unit 13, and a drain duct 15 that guides the liquid collected in the drain trough 14 to the downcomer 130.

Figure 4 is an enlarged perspective view showing a portion of the steam flow path 4 provided in the steam dryer unit 13 of the steam dryer 10 according to this embodiment, Figure 5 is a view taken along the line A-A in Figure 4, Figure 6 is a view taken along the line B-B in Figure 4, and Figure 7 is a view taken along the line C-C in Figure 5. Note that the slit 7 in Figure 7 is shown by a two-dot chain line, as it is provided in the auxiliary plate 5 on the opposite side to the view taken along the arrow.

Each of the two corrugated sheets 3 (first corrugated sheet 3a and second corrugated sheet 3b) sandwiching the steam flow path 4 has a plurality of bent portions 31 and flat portions 32 extending vertically. The bent portions 31 have convex portions 31a that protrude toward the steam flow path 4 and concave portions 31b that are recessed toward the steam flow path 4, and the convex portions 31a and concave portions 31b are arranged alternately on either side of the flat portion 32.

In addition, two auxiliary plates 5 (first auxiliary plate 5a and second auxiliary plate 5b) are provided between the two corrugated plates 3 that sandwich the steam flow path 4, with convex portions 51 and concave portions 52 arranged alternately in cross section. Therefore, in detail, the steam flow path 4 is formed between the first auxiliary plate 5a and the second auxiliary plate 5b, which is arranged at a predetermined distance from the first auxiliary plate 5a.

The recess 52 in the first auxiliary plate 5a is joined to the recess 31b in the first corrugated plate 3a, and the protrusion 51 in the first auxiliary plate 5a is disposed at a distance from the protrusion 31a in the first corrugated plate 3a. The drain passage 6 is formed between the protrusion 51 in the first auxiliary plate 5a and the protrusion 31a in the first corrugated plate 3a.

In addition, slits 7 connecting the steam flow path 4 and the drain flow path 6 are formed, for example, from the upper end to the lower end of the first auxiliary plate 5a on the upstream side of the protrusion 51 in the steam flow direction (the direction of the arrow of wet steam WS) of the steam flow path 4. Therefore, the first auxiliary plate 5a is divided into multiple plates by each of the multiple slits 7.

As shown in FIG. 4, the slit 7 is also formed between the upstream end 53 of the steam flow passage 4 of the first auxiliary plate 5a in the steam flow direction (the direction of the arrow of the wet steam WS) and the convex portion 31a of the first corrugated plate 3a.

The recess 52 in the second auxiliary plate 5b is joined to the recess 31b in the second corrugated plate 3b, and the protrusion 51 in the second auxiliary plate 5b is disposed at a distance from the protrusion 31a in the second corrugated plate 3b. The drain passage 6 is formed between the protrusion 51 in the second auxiliary plate 5b and the protrusion 31a in the second corrugated plate 3b.

In addition, slits 7 that connect the steam flow path 4 and the drain flow path 6 are formed from the upper end to the lower end of the second auxiliary plate 5b on the upstream side of the convex portion 51 in the steam flow direction of the steam flow path 4 of the second auxiliary plate 5b. Therefore, the second auxiliary plate 5b is divided into multiple plates by each of the multiple slits 7.

As shown in Figures 5 and 6, the drain passage 6 has an upstream region 6a located upstream of the wet steam WS and a downstream region 6b located downstream, with the upstream region 6a being the region close to the slit 7. As shown in Figures 5 and 7, the upstream region 6a is provided with a horizontal plate (stop plate) 8 that spans between at least two plates (corrugated plate 3 and auxiliary plate 5) and divides the region close to the slit 7 in the drain passage 6 (upper region 6aa) into upper and lower regions (upper region 6aa and lower region 6ab).

In addition, as shown in Figures 5 and 7, in the drain passage 6 below the horizontal plate 8, a vertical plate (partition plate) 9 is provided that extends downward from the end 81 of the horizontal plate 8 located on the opposite side of the slit 7 (the boundary between the upstream region 6a and the downstream region 6b) and is bridged between at least two plates (the corrugated plate 3 and the auxiliary plate 5) (see Figure 6), dividing the drain passage 6.

As shown in FIG. 7, the vertical plate 9 divides the lower region 6ab of the upstream region 6a from the lower region 6bb of the downstream region 6b. As a result, the lower region 6bb of the downstream region 6b is surrounded on all sides by the corrugated plate 3, the auxiliary plate 5, and the vertical plate 9.

Figure 8 is an enlarged perspective view that shows a schematic diagram of droplets D being separated from wet steam WS in the steam dryer unit 13 of the steam dryer 10 according to this embodiment. The droplets D contained in the wet steam WS passing through the steam flow path 4 are separated from the steam WS by centrifugal force and stick to the downstream side of the steam flow path 4 in the steam flow direction (the direction of the arrow of the wet steam WS) in the recess 52 of the auxiliary plate 5, forming a liquid film LF.

The liquid film LF flows down the surface of the auxiliary plate 5 due to the shear force caused by the pressure of the steam WS and gravity, and turns into droplets D through the slits 7 and flows into the drain passage 6.

The upstream region 6a of the drain passage 6 is divided into upper and lower regions (upper region 6aa and lower region 6ab) by a horizontal plate 8, and the lower region 6ab of the upstream region 6a is divided from the lower region 6bb of the downstream region 6b by a vertical plate 9.

Liquid droplets Da that flow from the slits 7 into the upper region 6aa of the upstream region 6a cannot descend into the lower region 6ab of the upstream region 6a due to the horizontal plate 8, and instead flow into the upper region 6ba of the downstream region 6b, from which they become liquid La and descend into the lower region 6bb. The liquid La then descends into the drain trough 14. Liquid droplets Db that flow from the slits 7 into the lower region 6ab of the upstream region 6a cannot descend into the lower region 6bb of the downstream region 6b due to the vertical plate 9, and instead become liquid Lb and descend into the drain trough 14.

[effect]
In the steam dryer 10 of the present embodiment, the lower region 6bb of the downstream region 6b is surrounded by the corrugated plate 3, the auxiliary plate 5, and the vertical plate 9 as described above. Therefore, the liquid L1 descending in the lower region 6bb of the downstream region 6b does not come into contact with the wet steam WS flowing from the slit 7 into the lower region 6ab of the upstream region 6a. Therefore, the liquid L1 descending in the lower region 6bb of the downstream region 6b is not blown away from the lower region 6bb of the downstream region 6b by the pressure of the wet steam WS. This prevents the liquid L1 from becoming droplets and scattering again from the slit 7 into the steam flow path 4, and can suppress an increase in the moisture content of the steam delivered from the steam dryer 10.

In addition, by shortening the length of the steam dryer 10, the flow rate of the liquid L descending through the drain passage 6 increases, and there is a possibility that the liquid L may overflow at the bottom of the drain passage 6 and overflow from the slits 7, and become droplets due to the steam flow and be re-scattered into the steam passage 4. However, in the steam dryer 10 of this embodiment, the lower area 6bb of the downstream area 6b is surrounded on the front, rear, left and right by the corrugated plate 3, auxiliary plate 5 and vertical plate 9, so that the liquid L is prevented from overflowing from the slits 7 and prevented from being re-scattered as droplets into the steam passage 4.

In addition, since the steam flow path 4 is formed between the first auxiliary plate 5a and the second auxiliary plate 5b, which have the convex portion 51 and the concave portion 52, centrifugal force acts when the wet steam WS flows from the concave portion 52 of the steam flow path 4 toward the convex portion 51, and the liquid droplets D, which have a large mass, are separated from the wet steam WS. Therefore, the liquid droplets D can be easily separated from the wet steam WS.

The drain passage 6 is formed between the convex portion 51 on the first auxiliary plate 5a and the convex portion 31a on the corrugated plate 3, and the slit 7 is formed on the upstream side of the convex portion 51 on the first auxiliary plate 5a in the steam flow direction of the steam passage 4. Therefore, the liquid droplets D separated from the wet steam WS by centrifugal force can be efficiently guided to the drain passage 6 by the slit 7 formed on the upstream side.

In addition, the slits 7 are provided from the upper end to the lower end of the auxiliary plate 5, so that the liquid droplets D can be separated from the wet steam WS over a wide range in the vertical direction and guided to the drain passage 6.

Figure 9 is a graph showing the steam flow rate and humidity at the inlet required for the steam moisture at the outlet of the steam dryer 10 to meet the steam turbine requirements.

As described above, the steam dryer 10 according to this embodiment can suppress an increase in the moisture content of the steam at the outlet. Therefore, it is possible to suppress a decrease in the operable region shown in FIG. 9.

Second Embodiment
Fig. 10 is an enlarged perspective view showing a part of the steam flow path 4 provided in the steam dryer unit 13 of the steam dryer 10 according to the second embodiment of the present invention. Fig. 11 is a view taken along the A1-A1 arrows in Fig. 10, Fig. 12 is a view taken along the A2-A2 arrows in Fig. 10, Fig. 13 is a view taken along the A3-A3 arrows in Fig. 10, Fig. 14 is a view taken along the B-B arrows in Fig. 10, and Fig. 15 is a view taken along the C-C arrows in Fig. 11. Note that the slits 7 in Fig. 15 are shown by two-dot chain lines because they are provided in the auxiliary plate 5 on the opposite side to the side viewed from the arrows.

The steam dryer 10 according to this embodiment differs from the steam dryer according to the first embodiment in that, as shown in FIG. 10, one drain passage 6 is provided with multiple horizontal plates 8 (in this embodiment, a first horizontal plate 8a, a second horizontal plate 8b, and a third horizontal plate 8c) and multiple vertical plates 9 (in this embodiment, a first vertical plate 9a, a second vertical plate 9b, and a third vertical plate 9c).

As shown in Figs. 10 and 15, the first horizontal plate 8a is the horizontal plate 8 located at the top and longest in the steam flow direction of the steam flow path 4 among the multiple horizontal plates 8, and the distance from the lower end of the drain flow path 6 (steam flow path 4) to the upper surface of the first horizontal plate 8a is hb. As shown in Fig. 11, the first horizontal plate 8a is bridged between at least two plates (corrugated plate 3 and auxiliary plate 5), and divides the area (first area 6a1) on the slit 7 side of the drain flow path 6 into upper and lower parts as shown in Fig. 15. In addition, the slit 7 is divided by the first horizontal plate 8a as shown in Fig. 15, and a first opening 7a is formed above the first horizontal plate 8a.

A first vertical plate 9a is provided extending downward from the end 8a1 of the first horizontal plate 8a located on the opposite side of the slit 7 to the lower end of the drain passage 6 (see FIG. 15). As shown in FIGS. 12 to 14, the first vertical plate 9a is bridged between at least two plates (the corrugated plate 3 and the auxiliary plate 5) and divides the first passage 6b1 from the drain passage 6. The first passage 6b1 is surrounded on all sides by the corrugated plate 3, the auxiliary plate 5, and the first vertical plate 9a.

As shown in Figures 10 and 15, the second horizontal plate 8b is located between the first horizontal plate 8a and the third horizontal plate 8c among the multiple horizontal plates 8, and is shorter than the first horizontal plate 8a and longer than the third horizontal plate 8c in the steam flow direction of the steam flow passage 4, and the distance from the lower end of the drain passage 6 to the upper surface of the second horizontal plate 8b is hc.

As shown in FIG. 12, the second horizontal plate 8b is bridged between at least two plates (the corrugated plate 3 and the auxiliary plate 5) and divides the area (the second area 6a2 shown in FIG. 12) on the slit 7 side of the drain passage 6 divided by the first vertical plate 9a into upper and lower parts. In addition, as shown in FIG. 15, the slit 7 is divided by the second horizontal plate 8b, and a second opening 7b is formed between the first horizontal plate 8a and the second horizontal plate 8b.

A second vertical plate 9b is provided that extends downward from the end 8b1 of the second horizontal plate 8b located on the opposite side of the slit 7 to the lower end of the drain passage 6 (see FIG. 15). As shown in FIGS. 13 and 14, the second vertical plate 9b is bridged between at least two plates (the corrugated plate 3 and the auxiliary plate 5) and divides the second passage 6b2 from the drain passage 6 into which the first passage 6b1 is divided by the first vertical plate 9a. The second passage 6b2 is surrounded on all sides by the corrugated plate 3, the auxiliary plate 5, the first vertical plate 9a, and the second vertical plate 9b.

As shown in Figures 10 and 15, the third horizontal plate 8c is the horizontal plate 8 located at the lowest position among the multiple horizontal plates 8 and is the shortest horizontal plate 8 in the steam flow direction of the steam flow passage 4, and the distance from the lower end of the drain passage 6 to the upper surface of the third horizontal plate 8c is hd.

As shown in Figure 13, the third horizontal plate 8c is bridged between at least two plates (corrugated plate 3 and auxiliary plate 5) and divides the area (third area 6a3 shown in Figure 13) on the slit 7 side of the drain passage 6, in which the first passage 6b1 and the second passage 6b2 are divided by the first vertical plate 9a and the second vertical plate 9b, into upper and lower parts. In addition, the slit 7 is divided by the third horizontal plate 8c as shown in Figure 15, and a third opening 7c is formed between the second horizontal plate 8b and the third horizontal plate 8c, and a fourth opening 7d is formed below the third horizontal plate 8c.

A third vertical plate 9c is provided, which extends downward from the end 8c1 of the third horizontal plate 8c located on the opposite side of the slit 7 to the lower end of the drain passage 6 (steam passage 4) (see Figure 15).

As shown in FIG. 14, the third vertical plate 9c is bridged between at least two plates (the corrugated plate 3 and the auxiliary plate 5) and divides the drain passage 6, which is divided by the first vertical plate 9a and the second vertical plate 9b into the first passage 6b1 and the second passage 6b2, into the third passage 6b3 and the fourth passage 6b4. The third passage 6b3 is surrounded on the front, rear, left and right by the corrugated plate 3, the auxiliary plate 5, the second vertical plate 9b and the third vertical plate 9c, and the fourth passage 6b4 communicates with the steam passage 4 through the fourth opening 7d.

Therefore, in the steam dryer 10 according to this embodiment, the length from the slit 7 to the end 81 (ends 8a1 to 8c1) of the multiple horizontal plates 8 (first horizontal plate 8a to third horizontal plate 8c) is longer the higher the horizontal plate 8 is located.

The slit 7 is divided into a plurality of openings 7i (first opening 7a to fourth opening 7d) in the vertical direction, and the plurality of drain passages 6 (first passage 6b1 to fourth passage 6b4, hereafter referred to as the plurality of divided passages 6i) divided into each of the plurality of openings 7i are connected to each other.

That is, as shown in FIG. 15, droplets D1 contained in the wet steam WS flowing above the first horizontal plate 8a flow into the first opening 7a and descend as liquid L1 through the first flow path 6b1. Droplets D2 contained in the wet steam WS flowing between the first horizontal plate 8a and the second horizontal plate 8b flow into the second opening 7b and descend as liquid L2 through the second flow path 6b2. Droplets D3 contained in the wet steam WS flowing between the second horizontal plate 8b and the third horizontal plate 8c flow into the third opening 7c and descend as liquid L3 through the third flow path 6b3. Droplets D4 contained in the wet steam WS flowing below the third horizontal plate 8c flow into the fourth opening 7d and descend as liquid L4 through the fourth flow path 6b4.

The drain passage 6 in this embodiment is designed with cross-sectional areas Aa to Ad so that the flow rate QL of the liquid L descending through each of the first passage 6b1 to fourth passage 6b4 is approximately uniform. Note that the cross-sectional areas Aa to Ad can be changed depending on the size and width of the first horizontal plate 8a to third horizontal plate 8c and the first vertical plate 9a to third vertical plate 9c.

Specifically, if the flow velocity of the liquid L descending through each of the first flow paths 6b1 to 4th flow paths 6b4 is VLi (i = a, b, c, d) and the cross-sectional area of each of the first flow paths 6b1 to 4th flow paths 6b4 is Ai (i = a, b, c, d), the flow rate QLi (i = a, b, c, d) of the liquid L descending through each of the first flow paths 6b1 to 4th flow paths 6b4 can be expressed by the following formula (1).

In order to make the flow rate QLi of the liquid L descending through each of the first flow path 6b1 to the fourth flow path 6b4 uniform, the cross-sectional area Ai can be determined so as to satisfy the following formula (2).

On the other hand, the flow velocity VLi of the liquid L descending through each of the first flow paths 6b1 to 6b4 is considered to be proportional to the flow velocity Vsi of the wet steam WS flowing through the first opening 7a to the fourth opening 7d that communicate with each of the first flow paths 6b1 to 6b4, and the flow velocity VLi of the liquid L can be expressed by the following equation (3).

Figure 16 shows (A) a schematic diagram of a vertical cross section of the steam dryer unit 13 of the steam dryer 10 according to this embodiment, and (B) a graph showing the relationship between the height H of the inlet of the steam flow path 4 and the flow velocity Vs of the wet steam WS.

As shown in FIG. 16(A), the direction of travel of the wet steam WS containing liquid droplets released from the steam separator 150 is changed from upward to sideways by the hood plate 1, which has a curved cross section. As a result, centrifugal force acts on the wet steam WS, and even after passing through the perforated plate 2, at the entrance of the steam flow path 4, as shown in FIG. 16(B), the flow velocity Vs of the wet steam WS is thought to be faster as the height H of the entrance of the steam flow path 4 is higher. Therefore, the flow velocity Vsi of the wet steam WS flowing through the first opening 7a to the fourth opening 7d is thought to be different at the upper and lower ends of each of the first opening 7a to the fourth opening 7d.

Therefore, the flow rate QLi of the liquid L descending through each of the first flow path 6b1 to the fourth flow path 6b4, calculated based on the flow rate Vsi of the wet steam WS, has an error ΔQLi. For example, in the first opening 7a, the flow rate at the height ha of the upper end is Vsa, while the flow rate at the height hb of the lower end is Vsb. Therefore, the error ΔQLa of the flow rate QLa of the liquid L1 descending through the first flow path 6b1 can be expressed by the following equation (4).

The standard deviation s of the flow rate QLi of the liquid L descending through each of the first opening 7a to the fourth opening 7d can be expressed by the following formula (5).

Here, n is the number of divided flow paths 6i (n=4 in this embodiment), Qi is the flow rate of liquid L descending through each of the first flow path 6b1 to the fourth flow path 6b4, and Qm is the average value of the flow rates Qi of liquid L descending through each of the first flow path 6b1 to the fourth flow path 6b4.

By designing the cross-sectional area Ai of each of the first flow path 6b1 to the fourth flow path 6b4 so that this standard deviation s is smaller than the error ΔQLi, the flow rate QL of the liquid L descending each of the first flow path 6b1 to the fourth flow path 6b4 becomes approximately uniform.

In addition, if the flow velocity Vsi of the wet steam is proportional to the height of the steam flow path 4 as shown in Figure 16 (B) and the vertical width of each of the first opening 7a to the fourth opening 7d is the same, the error ΔQLi in the second opening 7b to the fourth opening 7d is considered to be approximately the same value as the error ΔQLa in the flow rate QLa of the liquid L descending the first flow path 6b1 shown in equation (4). Therefore, the standard deviation s can be expressed by the following equation.

[effect]
In the steam dryer 10 according to this embodiment, the horizontal plates 8 (first horizontal plate 8a to third horizontal plate 8c) are longer in the steam flow direction of the steam flow passage 4, and the distance from the slit 7 to the end 81 (ends 8a1 to 8c1) is longer as the horizontal plate 8 is positioned higher. Therefore, the divided flow passage 6i communicating with the upper opening 7i is provided at a position away from the slit 7, and even if the flow velocity of the wet steam WS is high above the steam flow passage 4, the liquid droplets D flow into the divided flow passage 6i away from the slit 7, and are prevented from being re-entrained from the slit by the pressure of the wet steam WS.

In the steam dryer 10 of this embodiment, the cross-sectional area Ai of each of the multiple divided flow paths 6i (first flow path 6b1 to fourth flow path 6b4) divided by the vertical plate 9 is designed so that the flow rate QL of the liquid L descending from each of the multiple divided flow paths 6i is approximately uniform.

Therefore, the cross section of the divided flow passage 6i is wide relative to the flow rate of the descending liquid L, and the waste of flow passage space can be suppressed. In addition, the divided flow passage 6i is narrow relative to the flow rate of the descending liquid L, and the liquid L is prevented from overflowing from the divided flow passage 6i, overflowing into the steam flow passage 4 from the opening 7i of the slit 7, and being re-scattered by the wet steam flow.

In addition, in the steam dryer 10 of this embodiment, the horizontal plates 8 are multiple horizontal plates 8 (first horizontal plate 8a, second horizontal plate 8b, and third horizontal plate 8c), the vertical plates 9 are multiple vertical plates 9 (first vertical plate 9a, second vertical plate 9b, and third vertical plate 9c), the region 6a close to the slit 7 is divided into multiple parts vertically by the multiple horizontal plates 8, and the drain passage 6 is separated into multiple divided passages 6i (first passage 6b1 to fourth passage 6b4) by the multiple vertical plates 9. Therefore, the divided passages 6i other than the divided passage 6i closest to the slit are separated from the slit 7 by each of the multiple vertical plates 9.

In addition, the flow rate QL of the liquid L descending through each of the multiple divided flow paths 6i is approximately uniform. Therefore, the flow rate of the liquid L descending through the divided flow paths 6i on the slit side can be reduced, preventing the liquid L from overflowing from the slit 7 and re-scattering into the steam flow path 4, and suppressing an increase in the moisture content of the steam released from the steam dryer 10.

In addition, in the steam dryer 10 of this embodiment, the cross-sectional areas of the multiple divided flow paths 6i are designed so that the standard deviation of the flow rate QLi of the liquid L in any one of the multiple divided flow paths 6i relative to the average value of the flow rate QL of the liquid L descending each of the multiple divided flow paths 6i is smaller than the error ΔQs of the flow rate Qs of the steam flowing into the opening 7i of the slit 7 communicating with any one of the multiple divided flow paths 6i.

As a result, even if the flow speed of the wet steam WS flowing through the steam flow path 4 differs in the vertical direction, the cross-sectional area of the multiple divided flow paths 6i can be designed so that the flow rate QL of the liquid L discharged from each of the multiple divided flow paths 6i is approximately uniform.

Therefore, the cross section of the divided flow passage 6i is wide relative to the flow rate of the descending liquid L, and the waste of flow passage space can be suppressed. In addition, the divided flow passage 6i is narrow relative to the flow rate of the descending liquid L, and the liquid L is prevented from overflowing from the divided flow passage 6i, overflowing into the steam flow passage from the opening of the slit 7, and being re-scattered as droplets by the wet steam flow.

In addition, in the steam dryer 10 of this embodiment, the error ΔQs in the flow rate Qs of steam flowing into the opening 7i (first opening 7a to fourth opening 7d) of the slit 7 that communicates with any one of the multiple divided flow paths 6i is calculated from the flow velocity of the wet steam flowing through the upper and lower ends of the opening 7i of the slit 7. This makes it possible to easily and accurately calculate the cross-sectional area Ai at which the flow rate QL of the liquid L descending from each of the multiple divided flow paths 6i is approximately uniform when the flow velocity Vsi of the wet steam is proportional to the height of the steam flow path 4 as shown in FIG. 15(B).

The present invention is not limited to the above-described embodiments, but includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

The present invention may be embodied in the following manner. Although the embodiment in which the slit 7 is formed in the first auxiliary plate 5a has been shown, the slit 7 may be formed between the first auxiliary plate 5a and the corrugated plate 3.

3, 3a, 3b... corrugated plate, 31a... convex portion, 31b... concave portion, 4... steam flow path, 5, 5a, 5b... auxiliary plate, 51... convex portion, 52... concave portion, 6... drain flow path, 6a... upstream region, 6b1... first flow path, 6b2... second flow path, 6b3... third flow path, 6a4... fourth flow path, 6i... divided flow path, 7... slit, 7a... first opening, 7b... second opening, 7c... third opening, 7d... fourth opening, 7i... opening, 8... horizontal plate, 8a... first horizontal plate, 8b... second horizontal plate, 8c... third horizontal plate, 81, 8a1, 8b1, 8c1... end portion, 9... vertical plate, 9a... first vertical plate, 9b... second vertical plate, 9c... third vertical plate, 10... steam dryer

Claims (10)

A drain passage formed between at least two plates standing apart from each other;
a slit provided in any one of the at least two plates and connecting the drain passage to a steam passage;
A horizontal plate that is disposed between the at least two plates and divides an area of the drain passage close to the slit into upper and lower portions;
a vertical plate extending downward from an end of the horizontal plate opposite the slit with the end as an upper end and spanning between the at least two plates, thereby dividing the drain flow path. The steam dryer according to claim 1,
The horizontal plates are a plurality of horizontal plates provided at intervals in the vertical direction,
The steam dryer according to claim 1, wherein the vertical plates are a plurality of vertical plates extending downward from respective ends of the horizontal plates opposite the slits, the ends serving as upper ends . The steam dryer according to claim 2,
A steam dryer, wherein the horizontal plates each have a longer length from the slit to the end thereof the higher they are located. The steam dryer according to claim 1,
The at least two plates include a first auxiliary plate having convex portions and concave portions arranged alternately in a cross section;
A steam dryer comprising: a first auxiliary plate and a second auxiliary plate arranged at a predetermined interval from the first auxiliary plate, the first auxiliary plate being spaced apart from the second auxiliary plate; The steam dryer according to claim 4,
The at least two plates further include a corrugated plate having a recess to which the recess in the first auxiliary plate is joined and a protrusion to which the protrusion in the first auxiliary plate is disposed at an interval,
The drain passage is formed between the convex portion of the first auxiliary plate and the convex portion of the corrugated plate,
the slit is formed on the upstream side of the protrusion of the first auxiliary plate in a steam flow direction of the steam flow passage. The steam dryer according to claim 5,
A steam dryer, characterized in that the slit is provided from an upper end to a lower end of the first auxiliary plate. The steam dryer according to claim 1,
a cross-sectional area of each of the plurality of drain passages divided by the vertical plates is designed so that a flow rate of liquid descending from each of the plurality of drain passages divided by the vertical plates is approximately uniform. The steam dryer according to claim 7,
The cross plate is a plurality of cross plates,
The vertical plate is a plurality of vertical plates,
The slit and the area close to the slit are vertically divided into a plurality of openings and areas by the horizontal plates,
The steam dryer, wherein the drain passage is separated into a plurality of drain passages by the vertical plates. 9. The steam dryer according to claim 8,
a cross-sectional area of each of the drain passages is designed so that a standard deviation of a flow rate of liquid descending through any one of the drain passages relative to an average value of a flow rate of liquid descending through each of the drain passages is smaller than an error in a flow rate of steam flowing into an opening of a slit communicating with any one of the drain passages. The steam dryer according to claim 9,
a flow rate error of the steam flowing into an opening of a slit communicating with any one of the plurality of drain passages is calculated from the flow velocity of wet steam flowing through the upper and lower ends of the opening of the slit communicating with any one of the plurality of drain passages.

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