Condensation system

Abstract

A condensation system for condensing turbine exhaust steam, which is led via one or more turbine exhaust steam connections (21) to a condenser device (25) and a cooling device for the condenser coolant, wherein the condenser device (25) has a surface condenser (30) and a mixing condenser (35), and the cooling device has two separate coolant lines. The coolants of the surface condenser (30) and the mixing condenser (35) are supplied separately via coolant lines, and the surface condenser (30) and the mixing condenser (35) are arranged in a common condenser housing, or the surface condenser (30) and the mixing condenser (35) are arranged in separate condenser housings.In the condenser housing of the mixing condenser (35), flow guide plates (14) are arranged, which are designed to direct the new exhausted steam flowing directly from the turbine over a condensate collecting vessel (31), and the exhausted steam flow is partly counter-current and partly cross-current to the condensate flow of the mixing condenser (35). ŕ.

Description

Technical area The invention relates to a system for condensing exhaust steam with a condensing device and a cooling device, wherein two different condensation principles are combined in the condensing device and the cooling device has two types of cooling, a circulating cooling and / or a circulating-through cooling system, connected to the condensing device. State of the art Several types of condensing devices are known, such as water-cooled surface condensers and mixing or injection condensers. Water-cooled surface condensers have a series of cooling tubes filled with cooling water, in which the water is passed through large water chambers, and in which the exhaust steam from the turbine is condensed. However, the cooling tubes and water chambers of this type are expensive to manufacture. Surface condensers are now built with once-through cooling or circulating cooling, such as wet or dry cooling towers. In once-through cooling, natural water is used as the cooling water for the condensers in an open circuit. This type of cooling is used in places where such fresh water is available in sufficient quantities at a reasonable cost. However, environmental impacts, such as heating the running water, must also be taken into account. Once-through cooling is only applicable to condensers such as surface condensers where the coolant does not come into direct contact with the turbine steam. If there is not enough fresh water or for environmental reasons there is no suitable cooling device, then various circulation circuits are used with recooling of the coolant. In the circulation circuit, the coolant flows through the condenser system, where it is heated by the condensation of the turbine steam, then flows into a cooling tower for recooling and finally flows back into the condenser. A distinction can be made between wet cooling towers and dry cooling towers; in the first, the coolant is cooled in an open and air-tight system, in the second, in a closed system, sealed off from the air. Wet cooling towers are efficient due to the favorable heat transfer between water and air, and the heat transferred results in the evaporation of approx. 1-2% of the water flow. However, they have the well-known disadvantage that they cause fog clouds, hail and shadows due to evaporation, which are becoming less and less acceptable in residential and agricultural areas.In addition, the evaporated water must be replaced with fresh water. Dry coolers have the advantage of not causing such fog clouds, but they are less efficient than wet coolers and require additional and expensive cooling surface area in the cooling tower. The cooling towers used in everyday practice are known as wet-dry cooling towers, or hybrid cooling towers, such as those described in patent specification DE 24 52 123 and in the article “Cutting the fog” in The Chemical Engineer of October 29, 1992. They primarily meet the environmental requirements and the requirements for reducing water loss in order to avoid fog clouds, hail and shadows caused by fog clouds. To do this, the cooling water of the surface condenser is cooled in two circuits, in a dry cooling tower section and a wet cooling tower section. In dry cooling, the cooling water is led through finned cooling water tubes, where the air in the dry cooling tower section is heated by convective heat transfer. In wet cooling, the air is heated by direct contact between air and water. The evaporation of water increases the humidity of the air and creates water-saturated air.This saturated air mixes with the warm dry air from the dry cooling tower section, so that a moist air stream is generated, but no more fog clouds are formed. In order to reduce the humidity of the moist air to a practical value, approximately 20% of the heat must be removed in dry cooling. In hybrid cooling towers, the advantages of both cooling processes can be combined, namely the high heat output of the wet process and the fog-free nature of the dry process. The degree of hybridization can also be varied depending on the weather by means of a passage between the dry and wet parts of the cooling water in order to optimize the final humidity of the air mixture. The condensing system, also known as the Heller system, is described in the article "Operational experience and further development results of power plant air conditioning with the Heller system" by L. Heller and L. Forgo, published in the December 13, 1963 issue of Energietechnik or in the third volume of "Grosse Kraftwerke" published by Springer Verlag in 1968. According to this, the turbine steam is condensed with its own condensate in a mixing condenser, where part of the condensate is fed to the water-steam circuit and the rest is fed to the dry cooling tower via a cooling water circuit. One advantage of mixing condensers over surface condensers is that the condensation can be large, even complete, which reduces the condensate pressure and increases the turbine output. Furthermore, this type of condenser can be manufactured more advantageously, since expensive pipelines in the condenser and water chambers are not required. Finally, there are no water losses in the dry cooling tower.However, this system has the disadvantage of requiring an expensive heating surface in the dry cooling tower. This surface is larger compared to a system with the same capacity, with a surface condenser and a wet cooling tower, because the heat transfer to the air is worse here. Description of the invention The object of the invention is to create a condensation system that is cheaper to produce while maintaining the advantages of the aforementioned systems, and at the same time increases the turbine performance by reducing the condensate pressure. This task is solved by a condensation system for condensing turbine exhaust steam, which is led to a condenser device via one or more turbine exhaust steam connections, and a cooling device for a condenser coolant, where the condenser device has a surface condenser and a mixer2 HU 222 391 Bl condenser, and the cooling device has two separate refrigerant lines, and the refrigerants of the surface condenser and the mixing condenser are separately circulated through refrigerant lines, and the surface condenser and the mixing condenser are arranged in a common condenser housing, or the surface condenser and the mixing condenser are arranged in separate condenser housings. Flow guide plates are arranged in the condenser housing of the mixing condenser, which are designed to direct the new spent steam flowing directly from the turbine over a condensate collection vessel, and the steam flow is flowed in the opposite direction and crosswise to the condensate flow of the mixing condenser. In the first embodiment of the invention, both condensers of the device are arranged in a single common housing, in which both types of condensation are found, namely on the surface of the cooling tubes and with its own, sprayed condensate. In the second embodiment of the invention, the two condensers are arranged in separate housings. The steam is fed into the housings of the surface condenser and the mixing condenser through a common turbine evaporator branch. The condenser unit is connected to a wet-dry or hybrid cooling tower via two separate circulation lines, where the cooling water from the surface condenser is recooled by evaporation in the wet section and the condensate from the mixing condenser is recooled convectively in the dry section of the hybrid cooling tower. The main advantage of this condensation system is that a mixing condenser is used as part of the condenser system together with a surface condenser, rather than just a surface condenser on its own. In this system, the possibility is exploited to install a mixing condenser in the dry part of the hybrid cooling tower, where air cooling medium cannot be used. This results in savings in material and manufacturing costs. The total costs of a surface condenser are largely determined by the piping, tubes and support plates for the water chambers. In the system according to the invention, by using a mixing condenser, the running surface, support plates and water chambers can be reduced by, for example, 50%, which results in a saving of approximately 35% of the total costs of the condenser system. The total costs of the system can be further reduced if the volume of the mixing condenser is reduced with the same performance.This is possible if the condensate in the mixing condenser is not sprayed as drops, but is distributed as a very thin and turbulent water film. The heat transfer through such a film is several times greater than the heat transfer through droplets, so that the same performance can be achieved in a smaller space. Finally, the use of a mixing condenser has the advantage that the temperature difference in the mixing condenser section is zero. At the same time, the reduction of the temperature difference also causes a reduction in the condensate pressure, which can increase the turbine performance. The environmental benefits of hybrid cooling towers, such as the elimination of fog clouds, are also achieved in the condensation system according to the invention. It is also achieved that less fresh additional cooling water is required compared to pure wet cooling towers, since in the wet process only a part of the cooling water of the entire condenser system is cooled. In this system, it is not possible to pass between the wet and dry cooling circuits at the cooling tower outlet to control the air humidity. However, this control is not necessary, since the heat flow of the dry cooling can be max. 50% and the humidity of the exiting air mixture is far from the saturated range at all operating loads and in all seasons. Brief description of the figures Figure 1: A condensing system with a condenser unit with two combined condenser types arranged in a single housing and connected to a hybrid chiller, Figure 2: Side and top view of a condensation system with a surface condenser and a mixing condenser arranged in a separate housing, Figure 3: View and side view of a combined condenser system with a vented condenser and internal vents for cooling condensate and make-up water. Implementation of the invention 1 shows a system for condensing the exhaust steam of a low-pressure turbine 20. This has a condenser device 25 in which two condensers, i.e. a surface condenser 30 combined with a mixing condenser 35, are arranged in a common housing with a common condensate collection vessel 31. The steam from the low-pressure turbine 20 flows through an exhaust steam connection 21 into the housing of the condenser device 25. There, in the surface condenser 30, it condenses on the cooling tubes which are assembled in tube bundles 1 and in the condensate dispersed in the mixing condenser 35. Part of the steam flows in the flow paths in the directions of the arrows into the tube bundles 1, and another part flows around a flow guide plate 14 into the mixing condenser 35. The flow guide plate 14 results in the steam flowing from bottom to top in the region of the spray nozzles 2 of the mixing condenser 35, so that a flow is partly countercurrent and partly crosscurrent to the condensate spray. By diverting the steam flow, on the one hand, a countercurrent flow of the condensate is ideally created, but on the other hand, a pressure loss is caused that must be minimized. In order to optimize the flow conditions in the mixing condenser while minimizing the pressure loss, the flow is guided, for example, by one or more diagonal or curved plates. These flow guide plates 14 have the particular function of optimizing the deaeration of the condensates in the mixing condenser 35. As a result of this counterflow, the oxygen and other gas content of the falling condensate is continuously reduced during the fall. In the meantime, it must be avoided that the mixing condenser 35 HU 222 391 B1 condenser with a higher oxygen content would come into contact with the condensate collecting vessel 31, since this would cause the oxygen to enter the condensate collecting vessel 31 and increase the oxygen content of the condensate. Therefore, the flow guide plates 14 are arranged in such a way that the new spent steam flowing from the turbine towards the flow guide plates 14, which has a lower oxygen content, is led directly towards the condensate collecting vessel 31, and a cushion of the new spent steam is formed on the condensate surface in the condensate collecting vessel 31. The steam with a lower oxygen content then flows upwards above the condensate collecting vessel. In order to minimize contact between the condensate collection vessel 31 and the higher oxygen content steam in the mixing condenser, the condensate collection vessel 31 is formed only at the bottom of the surface condenser 30, and not at the bottom of the mixing condenser 35.The flow guide plates 14 also have the task of ensuring that the fresh steam flow flows countercurrently to the condensate flow for the greatest possible distance. The use of flow guide plates 14 to form a vapor plume above the condensate collection vessel 31 and to create a counterflow to the condensate flow in the mixing condenser 35 is also possible in condensers that have a horizontal exhaust steam flow from the turbine 20. The position of the condensate collection vessel 31 below the surface condenser 30 and / or the mixing condenser 35 is optimized in this case. By replacing part of the surface condenser 30 with a mixing condenser, it becomes unnecessary to support the housing with the support plates of the tube bundles 1. The housing of the combined condenser plant 25 can be supported, for example, by pipes, anchors or plates between the support plates and the condenser wall. The combined condenser 25 is connected by means of bypass lines 32, 33 to a hybrid cooling tower 40, in which the coolant of the condenser 25 is cooled. The cooling water of the surface condenser 30 enters the tubes of the tube bundle 1 through water chambers (not shown). After flowing through the cooling tubes, it is conveyed via a line by means of a circulation pump 5 to the wet part 42 of the hybrid cooling tower 40, where it is sprayed by spray nozzles 44, inserts or inserts 3. The cold air flows in the direction of the arrow through an air filter 43 and inserts 3, while the water cools down, flows into a collecting vessel and is pumped back into the surface condenser 30 via the pump 5. The mixing condensers 35 have several spray nozzles 2 or spray valves, which spray the cooled condensate of almost drinking water quality into the steam space. The steam from the turbine 20 condenses here in direct contact with the cold condensate, while in this process almost complete condensation is achieved. The sprayed condensate meets the newly formed condensate in the condensate collecting vessel 31. Two lines lead from here, one to a feed water pump 10, which carries part of the condensate further in the water-steam process, the other to a circulation pump 6, which carries the remaining condensate into a closed, airless circuit. It flows through the circulation pump 6 through the conduit 33 through the finned heat exchanger tubes 4, where it convectively transfers heat to the air, which flows upward through the air filters 43 in the direction of the arrow and by the action of the fans 45 or by the natural draft next to the tubes, and mixes with the moist air of the wet cooling.After flowing through the 4 heat exchanger tubes, the condensate is returned to the mixing condenser 35 through the line 33. In the cooling circuit in the wet part of the cooling tower 42, water is lost due to evaporation. Approximately 1-2% of the flow to be cooled is lost. The replacement of this water volume increases the salinity of the water. By replacing a larger amount of fresh make-up water and draining the salt water, the evaporated water is replaced on the one hand and the salinity in the circulation is stabilized on the other hand. Two water pipes 12, 13 are arranged in the hybrid cooling tower 40, one of which is used to introduce fresh water and the other to drain the salt water. An amount of fresh make-up water is added to the cooling water circuit of the surface condenser 30, which is approximately 5% of the cooling water volume of the open flow. In comparison, the required make-up water volume of a condenser system with only a surface condenser and wet-bed recooling requires a maximum of 5% total volume.In the system according to the invention, this additional water quantity is reduced by half in accordance with the division of the condensation of the surface and mixing condenser, since part of the condensation power is taken over by the mixing condenser and its cooling condensate flows in a closed, almost loss-free circuit. In a further embodiment of the invention, the According to Figure 2, the design of the condensation system is identical to that of Figure 1, with the difference that the surface condenser part and the mixing condenser part are separated from each other, each arranged in its own housing. Figure 2 shows this embodiment by way of example a cylindrical surface condenser 30 and a mixing condenser 35, which are connected to the turbine 20 via an evaporation stub. Instead of one mixing condenser, several mixing condensers can also be arranged, as shown in the top view. The figures show only two possible embodiments of the combination of surface and mixed capacitor. Other possible arrangements: a) In the so-called table arrangement, the condenser equipment is arranged below the turbine and the steam flow flows vertically from the turbine, as in Figure 1, and - the mixing condenser is divided into two parts, which are arranged on either side of the surface condenser, or - the mixing condenser is not arranged next to the surface condenser, but behind it; HU 222 391 Bl b) in the so-called floor mounted arrangement, the turbine and the condenser equipment are arranged on the same level and the steam flow is horizontal and next to the turbine or in the direction of the turbine axis, and - the mixing condenser next to the surface condenser, or - is arranged behind the surface condenser. In one embodiment, the mixing condenser part of the combined condenser device according to the invention is connected to a dry cooling tower and its surface condenser part is connected to a natural water cooling water circulation cooler. In a further embodiment, the surface condenser section is connected to a separate wet cooling tower and the mixing condenser section is connected to a separate dry cooling tower. The used air from the two cooling towers is brought together through ducts and mixed, thereby reducing the humidity and preventing the formation of fog clouds. In order to achieve the lowest possible pressure in the condenser system and to increase the turbine output, the condensate must be freed from non-condensable gases (air) as much as possible. In surface condensers, such as As shown in Figure 1, this can be achieved by collecting the steam-air mixture in air coolers 7 in the low pressure zone of each tube bundle 1 and extracting it through extraction pipes (not shown). In the mixing condenser section, as shown in Figure 3, non-condensable gases are removed from the condenser housing via vent pipes 36, 37, 17 through a vent condenser 15. In the embodiment shown in Figure 3, the mixing condenser 35 is also equipped with an internal vent 23. This is arranged in the mixing condenser 35 in a kind of cabin, which is formed by straight partitions 24 and the mixing condenser housing wall 35, the rear partition being indicated by a dashed line. The partitions 24, which can also be cylindrical, extend downwards from the top of the mixing condenser, but do not reach the bottom of the space, so that steam can flow into the space from below. The air vent 23 has spray nozzles 26 from which a partial flow of cooling condensate is sprayed through a pad or devices 34.A further deaerator 28 for the make-up water, which is fed into the water-steam cycle to compensate for losses due to steam, is designed like deaerator 23, with partitions in the form of a kind of cabin and has spray nozzles which spray the cooling condensate through a pad or devices 34. In both deaerators 23, 28, the steam flows from below, countercurrently to the condensate flow. In another variant, the steam flows through an opening in the upper region of the partitions 24, partly downwards and partly upwards, in the same direction and countercurrently to the condensate flow. In this case, the ventilation is arranged between the two columns with the same and countercurrent flow, as is known from EP 0 461 515. The additive water can also be introduced into the air vent 23, so that only one air vent is installed in the mixing condenser space. In the condenser device 25 according to FIG. 2, the mixing condenser 35 also has an internal air vent 23. The air vent 23 and the spray device 34 arranged therein are cylindrical. The air venting is carried out in a similar manner to that shown in FIG. 3. A steam line 47 leads from the surface condenser 30 to the air vent 23, in which the steam flows against the condensate flow. The condensed condensate is led from the air vent 23 to the condensate collection vessel 31 of the surface condenser via a connecting line 46. For example, an additive water air vent can be installed in the second mixing condenser space. In Figure 3, the steam-air mixture of the mixing condenser 35 and its internal vents is led to the vent condenser 15. This is connected to the mixing condenser 35, but can also be formed inside the housing. The steam-air mixture flows into the vent condenser 15 via several different lines 36,37,17, namely from the additive water vent 28 via line 17, from the mixing condenser via line 36 and from the vent 23 of the mixing condenser via line 37. The majority of the steam is condensed there by the spray nozzles 18. The spray nozzles 18 are meanwhile fed by the return condensate from the dry cooling circuit 33 via line 9. The non-condensable gases are extracted from the vent condenser 15 via an extraction pipe 8. The condensate water level in the vent condenser 15 is maintained by a siphon which leads from the vent condenser 15 to the mixing condenser 35. The condensate formed in the two condensers flows down into a condensate collecting vessel, from where it is partly returned to the cooling circuit via the circulation pump 6 and partly to the water-steam circuit (not shown) via the feed water pump 10. The condensate collecting vessel 31 has a barrier 39 for separating the high-quality condensate from the surface condenser 30 and the deaerator 23 of the water-steam circuit and the low-quality condensate from the mixing condenser 35 and the make-up water deaerator 28. The condensate level in the water-steam circuit is controlled by a conventional control valve (not shown) downstream of the pump 10 and by the flow-through facility between the condensate from the mixing condenser 35 and the make-up water deaerator 28. There is a flow path between the condensate of the mixing condenser 35 and the surface condenser 30 via the vent 23 and the openings in the upper region of the barrier 39, which allow the condensate to pass through. As is known, there is more free space in a mixing condenser compared to a surface condenser. According to a particular embodiment of the invention, the mixing condensers 35 have an internal flashbox 50 with a flat or curved baffle plate as shown in Figure 2. The steam flows along this plate, is distributed in the mixing condenser 35 and condenses in the dispersed condensate, while the condensate flows down into the condensate collection vessel 31.

Claims

PATENT CLAIMS 1. Condensation system for condensing turbine exhaust steam, which is led to a condenser device (25) via one or more turbine exhaust steam connections (21), and a cooling device for a condenser coolant, wherein the condenser device (25) has a surface condenser (30) and a mixing condenser (35), and the cooling device has two separate coolant lines, and the coolants of the surface condenser (30) and the mixing condenser (35) are separately circulated through coolant lines, and the surface condenser (30) and the mixing condenser (35) are arranged in a common condenser housing, or the surface condenser (30) and the mixing condenser (35) are arranged in separate condenser housings, characterized in that flow guide plates (14) are arranged in the condenser housing of the mixing condenser (35) which are are designed to direct steam over a condensate collection vessel (31),and the exhaust steam flow is partly counter-flowed and partly cross-flowed with the condensate flow of the mixing condenser (35)., Condensation system according to claim 1, characterized in that the mixing condensers (35) have a venting condenser (15) which is attached to the mixing condenser (35) or integrated into the mixing condenser space.

3. Condensation system according to claim 1, characterized in that the mixing condensers (35) have an internal deaerator (23) equipped with a spray insert or devices (34) for deaeration of the condensate and improvement of the water quality of the water-steam cycle, and the steam flow is conducted in countercurrent or cocurrent with the condensate.

4. Condensation system according to claim 1, characterized in that the mixing condensers (35) have an internal additive water deaerator (28) equipped with a cartridge or devices (34) for deaeration of the additive water of the water-steam cycle, and the steam flow is conducted in countercurrent or cocurrent with the condensate.

5. Condensation system according to claim 1, characterized in that the mixing condensers (35) have an internal expansion vessel (50) provided with a baffle plate.

6. Condensation system according to claim 1, characterized in that the condenser device (25) consists of a surface condenser (30) through which natural water flows and a mixing condenser (35) connected to a dry cooling tower.