Water and steam separator for a boiler drum

Abstract

A separator (1) for a boiler drum for separating steam and water, the separator (1) having a separation chamber (5) with a fluid inlet (2) at the bottom of the separation chamber (5) and a steam outlet (3) at the top of the separation chamber (5), and helical vanes (9) attached to the chamber wall (6) of the separation chamber (5) between the fluid inlet (2) and the steam outlet (3) to achieve a circular motion of the incoming fluid, and wherein a circular water outlet (4) surrounds the steam outlet (3). The top end (8) of the chamber wall (6) of the separation chamber (5) within the water outlet (4) has a rounded top profile to ensure a smooth flow and to maintain a full collector (13) at the top area of the water outlet (4), and the top end (8) of the chamber wall (6) is preferably inwardly inclined. The inclination at the top end (8) of the chamber wall (6) is preferably concave.

Description

Technical Field

[0001] The present invention relates to a steam and water separator having a separation chamber having a fluid inlet at the bottom of the separation chamber and a steam outlet at the top of the separation chamber. Background Technology

[0002] The boiler drum forms part of the boiler's circulation system. The drum has two main functions: first, and most importantly, it separates steam from the mixture of water and steam; second, it houses equipment for purifying both the steam and water.

[0003] Two different types of cyclone separators are used to perform basic separation of water and steam. The basic type has a tangential inlet that causes the fluid to rotate, and the lighter steam separates from the water and exits from the top of the cyclone separator.

[0004] The vertical cyclone separator has a bottom inlet, and the helical blades convert the incoming fluid flow into a circulating motion. Therefore, the aqueous phase separates and flows laterally to the side of the separator's separation chamber, and flows upward along the inner wall of the separation chamber to the space between the separation chamber and the outer wall of the separator. Steam exits from the top of the separator. Vertical separators are disclosed in the following publications: US3216182, EP2250437, JPH11141802, US3086343, GB664447, US3329130, and US5320652. Summary of the Invention

[0005] As boiler operating efficiency requirements increase, the inflow to the boiler drum also increases, necessitating optimization of steam separation efficiency. Existing solutions generate excessively high pressure differentials, and / or too much water leaves with the steam, which also remains mixed with the discharged water. Water in the steam must not be allowed to enter the superheater and further into the steam turbine, as this would have harmful consequences. Steam bubbles in the discharged water will create small water droplets within the drum when they burst. The auxiliary demister captures most of these droplets. This increases the water load on the auxiliary demister, thus affecting its overflow, and water may enter the superheater. Excessive water entering the superheater can damage it, and in the worst case, impurities with water droplets may continue into the steam turbine. Steam bubbles below the water surface will also worsen water level control and, in the worst case, will be absorbed by downcomers, weakening the drive head of the natural cooling water circulation.

[0006] Widely used and other disclosed vertical separators can effectively separate water and steam within a separation chamber. The main problem is not the separation step itself, but rather the steam entering the water outlet. The water flow should be smooth and consistent within the water outlet to maintain the separation of the gas and liquid phases. For example, known separators have a top design of the separation chamber with a sharp water path at the edge of the water outlet. The disclosure in US3216182 recognizes the problem of steam entering the water outlet and returning from there. This backflow will contain water droplets because the abrupt change in the flow path produces these droplets. This problem is solved by directing the mixture to a separate water / steam outlet concentric with the water outlet. Steam entering the water outlet causes a backflow of the water and steam mixture. This mixture should be separated again in a demister.

[0007] US3329130 discloses a rounded top at the top of the chamber wall of a separation chamber. This slightly rounded end of the chamber wall cannot prevent high turbulence at the top of the water outlet because the radius is too sharp to achieve a significant flow path guiding effect.

[0008] Inconsistent flow or turbulence within the water outlet will open a steam inlet leading deeper into the water outlet. Any steam entering the outlet may also cause a backward ejection of the water-steam mixture, resulting in water entering the steam outlet. The object of this invention is to prevent steam from entering the water outlet and mixing with the water outflow. Flow integrity is ensured by avoiding any abrupt changes in the flow path. Inconsistent gravity suction effects are also avoided because the downward path of the water will be completely filled, and therefore variations in the water flow are prevented. This invention enables more complete separation of the aqueous and steam phases without causing excessive pressure drops in the separator. These and other objects, which will become apparent from the following overview and description, are achieved by the separator according to the invention.

[0009] A separator for a boiler drum, the separator for separating steam and water, the separator having a separation chamber having a fluid inlet at the bottom of the separation chamber and a steam outlet at the center of the top of the separation chamber. Helical blades are attached to the chamber wall between the fluid inlet and the steam outlet to achieve annular motion of the incoming fluid to separate the water phase and the steam phase. A circular water outlet surrounds the steam outlet.

[0010] The rapid, circular motion of the fluid directs the flat, upward flow of the aqueous phase to the side of the separation chamber, where lighter steam bubbles move to the surface of the water flow and burst. The steam then flows upward through the separation chamber to the steam outlet at the top. If the separation chamber has a top shape with an upwardly increasing diameter, the upward flow of water will have a circular component and will rise optimally. The upward-flowing water forms a thinner layer, which improves steam separation. The steam outlet can also have a larger initial diameter to reduce the pressure drop. If the steam outlet has a bottom shape with a smoothly decreasing diameter, the pressure drop will be further reduced.

[0011] The objective is to create a water collector with a uniform barrier surface that prevents further steam from entering the water outlet. To achieve this, water must flow smoothly within the outlet to suppress turbulence, isolated droplets, or other flow inconsistencies. Otherwise, steam will enter the outlet between droplets or separated flows. The water collector is arranged in an inverted configuration, but it functions like a conventional water collector, forming a stable barrier for the gas. It is filled with the continuously rising flow of separated water. Therefore, carefully designed water channels are necessary to prevent water from falling back into the collector. Different operating conditions will result in water layers of varying thicknesses; therefore, the dimensions must be designed to accommodate various operating conditions, i.e., flow velocities and flow rates. During operation, no active adjustments to any blades or other components are possible.

[0012] To achieve this goal, the main new and most critical feature is the form of the apex of the separation chamber wall. The apex of the separation chamber wall within the water outlet has a rounded profile with a sufficiently large minimum radius. This cannot be achieved simply by grinding the cut-out apex of the chamber wall to a small radius. If the outflowing water has a sufficient radius relative to the surrounding flow velocity, the outflowing water will remain on the side of the apex without breaking into droplets or causing other discontinuities in the flow. This is known as the "teapot effect." Therefore, the apex is not merely the end of a cylinder or cone, but a unique, integral part of the separator. If the apex of the separation chamber wall is formed by the separation chamber wall itself, the rounded form should continue at least at the apex, preferably at least 45 degrees.

[0013] The inwardly sloping top of the separation chamber ensures that the water collector within the water outlet is optimally kept full and free from steam. This design creates a stable and uniform water surface behind the opening of the water outlet, preventing the entry of the steam phase. The sloping top of the chamber wall of the separation chamber smoothly guides the inflow onto the opposite wall of the water outlet. The inward slope is preferably concave, so that the slope optimally guides the inflow smoothly onto the opposite wall of the water outlet. The opposite side of the outlet should have a low contact angle relative to the surface of the inflow to avoid droplet formation where the inflow contacts the opposite side.

[0014] The top of the chamber wall surrounding the water outlet, opposite the water outlet, should be smoothly curved to allow for a smooth and continuous flow of water through the area of ​​the collector. Any sharp edges will cause discontinuities in the flow and thus lead to possible steam paths.

[0015] If multiple guide vanes are provided within the water outlet, behind the collector, between the chamber wall of the separation chamber and the outer wall of the separator, and these guide vanes are arranged downwards at a pitch angle opposite to that of the helical blades, it further ensures that the collector remains filled. The vanes redirect the flow in a more horizontal direction, thereby generating a slight back pressure. Since the water outlet beside the separation chamber will thus be filled only with water, it can generate an effective gravity suction effect. This partially compensates for the pressure drop caused by the guide vanes. The cumulative circumferential coverage of the guide vanes is preferably at least 360 degrees. The pitch angle of the guide vanes is preferably between 45 and 75 degrees. The number of guide vanes is preferably 6 to 16, depending on the pitch angle and the target circumferential coverage.

[0016] The water outlet should have a smooth, curved profile on the opposite side of the collector area, conforming to the rounded apex of the chamber wall of the separation chamber. The width of the water outlet should be substantially constant, or preferably, it should gradually narrow in the flow direction to ensure smooth and uniform flow. The narrowing path ensures that the collector remains completely filled, and any trapped steam can return from the wider opening of the outlet.

[0017] Without increasing pressure drop, the separation efficiency percentage for both the aqueous and steam phases has shown significant superiority over existing vertical separators. The amount of residual water that needs to be separated from the steam in the demister is also significantly reduced, thus increasing demister efficiency and minimizing pressure loss. The carefully optimized design of this separator ensures higher steam power generation compared to boilers with conventional separators. Attached Figure Description

[0018] Examples of embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 The existing steam drum arrangement of the boiler is shown.

[0019] Figure 2 A cross-section of a preferred embodiment of the present invention is shown; Figure 3 It shows Figure 2 A view of the guide blades in an embodiment. Detailed Implementation

[0020] Figure 1A prior art steam drum arrangement is shown for separating steam and water fluids entering from the cooling pipes of the boiler chamber. A vertical separator 1 first separates the incoming fluids. Several separators 1 are installed inside the steam drum, depending on the boiler capacity. The fluid is primarily steam bubbles in water. At higher steam levels, the water may also be in the form of droplets.

[0021] The main demister at the top of separator 1 prevents most residual droplets from entering the steam space of the steam drum. An auxiliary demister at the top of the steam drum removes droplets, preventing them from flowing out into the superheater tubes. If the separation efficiency is too low, the demister can be filled with water, resulting in higher pressure losses and incomplete separation.

[0022] The spiral blades 9 inside the separation chamber 5 guide the incoming fluid in a circular motion, and the separated water phase rises to the water outlet 4 along the side of the chamber wall 6 of the separation chamber 5. The separated water exits the separator 1 from the bottom of the water outlet 4. The steam exits through the central steam outlet 3 at the top of the separation chamber 5.

[0023] The design shown has several flaws that lead to pressure drop and incomplete separation within separator 1. The form of water outlet 4 interferes with the outflowing water because incompletely separated steam can enter water outlet 4 and may cause resonant backflow. The sharp edge at the top of the chamber wall 6 of separation chamber 5 breaks the separated water flow into droplets, which will mix with any ejection of captured steam flowing back from water outlet 4. The droplets will then exit separator 1 through steam outlet 3.

[0024] Figure 2 A cross-section of a preferred embodiment of the invention is shown. The separator 1 has a separation chamber 5 with a fluid inlet 2 at its bottom. A helical blade 9 is attached to the chamber wall 6 of the separation chamber 5 between the fluid inlet 2 and a steam outlet 3. An annular water outlet 4 surrounds the steam outlet 3. At the top of the section of the separation chamber 5 above the helical blade 9, the chamber wall 6 of the separation chamber 5 has a top section 7 with an upwardly increasing diameter. The steam outlet 3 has a bottom shape with an upwardly decreasing diameter. The top curved shape of the steam outlet 3 has an upwardly increasing diameter.

[0025] Water outlet 4 initially guides upwards, and then, at the top of water outlet 4, within the inverted water collector 13, water outlet 4 turns downwards. The top 8 of the chamber wall 6 of the separation chamber 5 within water outlet 4 has a rounded profile. The minimum radius R should be greater than 8 mm, preferably greater than 12 mm, and this minimum radius does not need to be constant. The opposite wall of water outlet 4 has a profile conforming to the top 8 of the chamber wall of separation chamber 5. The width of water outlet 4 is substantially constant, or narrows in the outflow direction. The top 8 of the chamber wall of separation chamber 5 within water outlet 4 slopes inwards, i.e., it has an upwardly decreasing diameter. The angle β of the slope from the beginning to the point where the chamber wall bends outwards from the slope line should be at least 15 degrees, and the length of the slope L should be at least 25 mm. Preferably, the slope is not straight, but concave, as... Figure 2 As shown. The inward tilt also evenly directs the incoming water onto the outer wall 14 of the water outlet, thereby isolating the opening region of the water outlet 4 from the free steam flow. This inward tilt also locally reduces the velocity, thus increasing the static pressure of the water. This enhances the effect of removing steam from the water.

[0026] Several guide vanes 12 are positioned within the water outlet 4, between the top region of the chamber wall 6 of the separation chamber 5 and the outer wall 11 of the separator 1. The number of guide vanes 12 is preferably 6 to 16, more preferably 10 to 14. The cumulative circumferential coverage of the equidistant guide vanes 12 is preferably at least 300 degrees, and most preferably more than 360 degrees, such that they cover at least a large portion of the entire circle.

[0027] The dashed line on surface 10 shows the surface of the water flow within the separation chamber 5 and into the water outlet 4. A gap should be provided between the wall of the steam outlet 3 and the surface 10 of the water flow to prevent water from entering the steam outlet 3. A smooth and consistent flow will keep the water collector 13, located at the highest region of the water outlet 4, full, preventing steam from entering beyond the opening of the water outlet 4. In practice, no steam backflow will occur, but any path of returning steam is indicated by a curved arrow. The guide vanes 12 will constrain the inflow of water into the water outlet 4, thereby ensuring that the water collector 13 remains full. If the width of the water outlet 4 is sufficiently reduced at or after the end of the water collector 13, it can also ensure, or alternatively, that the water collector 13 remains full.

[0028] Figure 3 It shows Figure 2A more detailed view of the guide vane 12 in the embodiment. The pitch angle α of the guide vane 12 is aligned in the opposite direction to the pitch angle of the helical blade 9. The pitch angle α of the guide vane 12 is preferably between 45 and 75 degrees. The arrows indicate the approximate direction of the water flow. Increasing the angle of attack of the guide vane 12 relative to the flow direction will enhance the separation of steam and water, but will also increase pressure loss. If the guide vane 12 is aligned in the same direction with respect to the pitch angle of the helical blade 9, they will draw in and strengthen the water inflow. Therefore, the water collector 13 may be open to steam and draw in steam.

Claims

1. A separator (1) for separating steam and water in a boiler drum, the separator (1) having a separation chamber (5) having a fluid inlet (2) at the bottom of the separation chamber (5) and a steam outlet (3) at the top of the separation chamber (5), and a helical blade (9) attached to the chamber wall (6) of the separation chamber (5) between the fluid inlet (2) and the steam outlet (3) to achieve annular motion of the incoming fluid, wherein, A circular water outlet (4) surrounds the steam outlet (3), the water outlet (4) being first directed upward and then turned downward, characterized in that the top end (8) of the chamber wall (6) of the separation chamber (5) within the water outlet (4) has a rounded top profile with a minimum radius (R) of 8 mm.

2. The separator (1) according to claim 1, wherein The top end (8) of the wall (6) of the separation chamber (5) is inclined inward, such that the angle (β) from the start of the inclined line to the point where the top end (8) of the wall (6) bends outward from the inclined line and the top end (8) of the wall (6) is at least 15 degrees, and the length (L) of the inclination is at least 25 mm.

3. The separator (1) according to claim 1 or 2, wherein The minimum radius (R) of the rounded top profile is at least 12 mm.

4. The separator (1) according to any one of claims 1-2, wherein, The inclination at the top (8) of the chamber wall (6) is concave.

5. The separator (1) according to any one of claims 1-2, wherein, The opposite wall of the water outlet (4) at the top (8) of the chamber wall (6) surrounding the separation chamber (5) has a curved form without any edges.

6. The separator (1) according to any one of claims 1-2, wherein, The separation chamber (5) has a top section (7) with an upwardly increasing diameter.

7. The separator (1) according to any one of claims 1-2, wherein, Inside the water outlet (4), a plurality of guide vanes (12) are provided between the chamber wall (6) of the separation chamber (5) and the outer wall (11) of the separator (1), and the plurality of guide vanes (12) are arranged in the opposite direction of the pitch angle (α) of the spiral blade (9).

8. The separator (1) according to claim 7, wherein The number of the guide blades (12) is 6 to 16 or 10 to 14.

9. The separator (1) according to claim 7, wherein The cumulative circumferential coverage of the guide vane (12) is at least 300 degrees or at least 360 degrees.

10. The separator (1) according to claim 7, wherein, The pitch angle (α) of the guide vane (12) is between 45 degrees and 75 degrees.

11. The separator (1) according to any one of claims 1-2, wherein, The opposite wall of the top end (8) of the water outlet (4) facing the chamber wall of the separation chamber (5) is curved, such that the width of the water outlet (4) is substantially constant, or the width of the water outlet (4) narrows in the outflow direction.

12. The separator (1) according to any one of claims 1-2, wherein, The steam outlet (3) has a bottom shape with a decreasing diameter upwards and / or a top shape with a increasing diameter upwards.

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