CN102852742B - Tower type solar thermal power generation system for heat absorber of vacuum heat absorption pipes - Google Patents

Abstract

The invention discloses a tower type solar thermal power generation system for a heat absorber of vacuum heat absorption pipes, which is characterized in that water/steam is taken a heat transfer fluid, and fusion salt is taken as a heat storage medium. The tower type solar thermal power generation system comprises a heliostat (1), a support tower (2), a heat absorber (3), a steam turbine (4), a generator (5), a deaerator (6), a condenser (7), a water feed pump (8), a high-temperature fusion salt storage tank (9), a low-temperature fusion salt storage tank (10), a water/steam-fusion salt heat exchanger (11), a fusion salt steam generator (12) and a control valve (13). The heat absorber (3) is formed by connecting the vacuum heat absorption pipes (18) in series and in parallel. According to the invention, the heliostat is arranged in a fan-shaped manner, a rectangular manner or a circumferential manner, the high-temperature and high-pressure overheating steam is obtained, and the solar thermal power generation system is suitable for a large installed capacity tower type solar thermal power generation station.

Description

Tower solar thermal power generation system with vacuum heat absorbing tube heat absorber

technical field

The invention relates to a tower type solar thermal power generation system, in particular to a tower type solar thermal power generation system using a vacuum heat absorbing tube as a heat absorber.

Background technique

Solar energy is an inexhaustible renewable energy source. Today, as fossil fuels are decreasing year by year and the international energy situation is becoming increasingly severe, the development and utilization of solar energy is one of the important ways to realize the diversification of energy supply and ensure energy security. The basic principle of the tower-type solar thermal power generation device is to use many heliostats to reflect solar radiation to the solar receiver placed on the tower, and generate superheated steam or high-temperature air with the help of heating medium to drive the generator set to generate electricity. The high temperature solar heat absorber is the core component of the tower thermal power generation system. Many studies have been carried out on this technology abroad, mainly in the United States, Spain, Germany, Israel, Australia, South Korea and so on. Among them, the power generation working fluid of the solar thermal power generation system using the Rankine cycle is water vapor, and the high-energy-flux-density solar energy collected by the heliostat field is converted into high-quality water vapor that meets the operation of the steam turbine. The usual technical methods include direct methods and There are two indirect ways. The direct method refers to concentrating solar energy into water/steam heat absorbers to obtain high-quality steam, and the indirect method refers to concentrating solar energy into non-hydraulic heat absorbers, such as molten salt heat absorbers, air heat absorbers, Sodium heat absorber, oil heat absorber, etc., and then through heat exchange equipment to obtain high-quality steam.

The solar thermal power station using water/steam as the working medium does not require secondary heat conversion, and has the advantages of simple system and high efficiency. It is one of the technical methods that all countries in the world attach importance to development. European patent EP2428999A1 discloses a solar thermal power generation system that utilizes natural circulation to obtain saturated steam. U.S. Patent US2008078378-A1 discloses a water/steam heat absorber in which the steam generator and the steam superheater are heated separately. The area with low density, and the steam generator is arranged in the area with high energy flow density of concentrated radiation input. Patent WO20110303331A2 discloses a tower-type solar thermal power generation system, which is characterized by the use of water/steam heat absorbers and molten salt heat absorbers, the steam generator and steam superheater of the water/steam heat absorber are arranged separately, and the steam generator It is arranged outside the heat absorber to enclose a cavity, and a steam superheater is arranged in the cavity to reduce the heat loss in the steam superheating process, and the molten salt heat absorber is arranged on the ground. The heliostat field is arranged in a circle, and part of the solar radiation concentrated by the heliostats is reflected and converged again by the lower trans-type secondary reflector to the molten salt heat absorber arranged on the ground, and part of the heliostats converge the solar radiation energy Into the steam superheater, some heliostats focus the solar radiation energy on the steam generator.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the existing water/steam heat absorbers, such as low thermal efficiency, high requirements on the precision of the concentrating system, and poor safety, and propose a tower-type solar thermal power generation system using vacuum heat absorbing tubes as heat absorbers.

The tower type solar thermal power generation system of the present invention uses water, saturated steam and superheated steam as the heat transfer fluid, and includes main equipment and auxiliary equipment such as heliostats, support towers, heat absorbers, heat storage systems, steam turbines and generators , such as pumps, etc. The invention uses water, saturated steam and superheated steam as the heat transfer fluid, and the obtained high-temperature and high-pressure steam can be directly used for steam turbine power generation, avoiding the use of intermediate heat transfer fluid, and improving the heat conversion efficiency of the system.

The heliostat is a concentrating device of a tower-type solar thermal power station. The heliostats are arranged on the ground with the supporting tower as a reference, and the heliostats can be arranged in a fan-shaped arrangement, a rectangular arrangement or a circular arrangement, so as to efficiently gather solar energy to the surface of the heat sink.

The support tower is used to support the heat absorber and its pipeline system, and is usually made of steel structure or reinforced concrete. For a fan-shaped heliostat field, the support tower is arranged at the center of one side of the fan-shaped heliostat field, and for a circular heliostat field the support tower is arranged at the center of the heliostat field. The principle of the arrangement is to realize the heliostat The mirror field has the highest light-gathering efficiency throughout the year.

The heat absorber is composed of multiple vacuum heat absorbing tubes. Holes are left between the plurality of vacuum heat-absorbing tubes, and at least two rows of vacuum heat-absorbing tubes are arranged in the direction of energy flow for absorbing concentrated solar radiation to ensure sufficient absorption of solar energy. Multiple vacuum heat absorbing tubes are connected by welding, and can be connected in series or in parallel according to the flow direction of the heat transfer fluid.

The vacuum heat absorbing tube is the core heat absorbing element of the solar thermal power station. The vacuum heat absorbing tube is composed of a metal inner tube, a glass outer tube, a glass metal sealing ring, etc. The metal inner tube is located in the inner layer of the vacuum heat absorbing tube, and the glass outer tube is located in the outer layer of the vacuum heat absorbing tube. The axis of the outer tube coincides, the glass-metal sealing ring is located at both ends of the vacuum heat-absorbing tube, one end of the glass-metal sealing ring is welded to the metal inner tube, the other end is welded to the glass outer tube, the outer wall of the metal inner tube is connected to the inner wall of the glass outer tube and the outer wall surface of the glass-metal sealing ring together form a cavity, and a vacuum is drawn from the cavity to form a vacuum interlayer. The outer surface of the metal inner tube is coated with a selective absorbing coating, which has a high absorption ratio in the solar spectral range and a low emission ratio in the infrared band. Multiple vacuum heat absorbing tubes can be connected in series by welding metal inner tubes, and the parallel connection of vacuum heat absorbing tubes can be realized by welding the metal inner tubes of multiple vacuum heat absorbing tubes with headers or main pipelines. The heat absorber is equipped with upper and lower headers to realize the parallel connection between the vacuum heat absorbing tubes.

Due to the high light-to-heat conversion efficiency of the vacuum heat-absorbing tube, a higher temperature can be obtained under the condition of a lower concentrated radiation energy flux density, and the heat absorber can be arranged with a larger heat-absorbing area, which can significantly reduce the solar radiation. The overflow loss on the surface of the heat absorber during the concentrating process of the mirror field greatly reduces the requirements for the tracking accuracy of the heliostat, thereby helping to reduce the initial investment and operating costs of the heliostat field. Depending on the requirements of the steam parameters at the outlet of the heat absorber, a steam-water separator can be arranged. The steam-water separator is placed in the support tower, and the steam-water separator does not receive heating from solar radiation.

The heat storage system uses molten salt as the heat storage medium, including a high-temperature salt storage tank for storing molten salt at a relatively high temperature, a low-temperature salt storage tank for storing molten salt at a relatively low temperature, and a water/steam-molten salt storage tank. Heat exchangers and auxiliary equipment such as a molten salt steam generator, molten salt pumps and valves. The steam side of the water/steam-molten salt heat exchanger is connected to the heat absorber and the steam turbine respectively through steam pipelines, and the water side of the water/steam-molten salt heat exchanger is connected to the deaerator through pipelines. The high-temperature salt storage tank is arranged adjacent to the support tower to reduce the heat loss of superheated steam transmission. The water/steam-molten salt heat exchanger, the low-temperature salt storage tank and the molten salt steam generator are arranged near the high-temperature salt storage tank, the low-temperature salt storage tank and the high-temperature salt storage tank are arranged adjacently, the low-temperature salt storage tank and the high-temperature salt storage tank One side of the tank is adjacent to the water/steam-molten salt heat exchanger to reduce the heat loss of pipeline transmission during the heating process, and the other side of the low-temperature salt storage tank and the high-temperature salt storage tank are adjacent to the molten salt steam generator to reduce Pipeline transfer heat loss for an exothermic process. The heat storage system can stabilize the fluctuation of solar energy and be used for power generation when solar energy is insufficient or at night, increasing the operating hours.

The working process of the present invention is as follows:

The solar radiation energy collected by the heliostat is projected onto the heat absorber on the support tower. The heat absorber is composed of multiple vacuum heat absorption tubes. Water, steam-water mixture and steam flow in the metal inner tube of the vacuum heat absorbing tube due to the different heat transfer characteristics of the heat transfer fluid in the tube. Most of the concentrated radiant energy flow is projected through the glass outer tube of the vacuum heat absorbing tube, and penetrates to the outer surface of the metal inner tube coated with a selective absorbing coating to achieve efficient absorption of input solar radiation energy and low heat radiation loss . Through the convective heat exchange with the water/steam flowing in the metal inner tube, the conversion of solar energy to water/steam heat energy is realized. The steam at the outlet of the heat absorber can be directly sent to the steam turbine to drive the generator to generate electricity, or it can be sent to the water/steam-molten salt heater to heat the molten salt for heat storage. When the solar energy is insufficient, the high-temperature molten salt in the heat storage system is heated by the molten salt steam generator to obtain superheated steam, which is sent to the steam turbine to drive the generator to generate electricity. The solar thermal power generation system of the present invention is suitable for fan-shaped arrangement of heliostat fields and circular arrangement of heliostat fields, and has significant advantages in tower-type solar thermal power stations with installed capacity.

Description of drawings

Fig. 1 tower type solar thermal power generation system of the present invention;

Fig. 2 directly produces steam type vacuum heat absorbing pipe water/steam heat absorber schematic diagram of the present invention;

Fig. 3 schematic diagram of the used vacuum heat absorbing tube of heat absorber of the present invention;

Fig. 4 A-A direction sectional view of Fig. 2 of the present invention;

Fig. 5 has the schematic diagram of the vacuum heat absorbing pipe water/steam heat absorber of the present invention with steam-water separator;

In the figure: 1 heliostat, 2 support tower, 3 heat absorber, 4 steam turbine, 5 generator, 6 deaerator, 7 condenser, 8 feed water pump, 9 high temperature molten salt storage tank, 10 low temperature molten salt storage Tank, 11 water/steam-molten salt heat exchanger, 12 molten salt steam generator, 13 control valve, 14 concentrated radiant energy flow, 15 feed water, 16 superheated steam, 17 molten salt, 18 vacuum heat absorbing pipe, 19 feed water Header, 20 steam header, 21 steam-water separator, 22 circulating water pump, 23 saturated steam, 31 metal inner tube, 32 glass outer tube, 33 glass-metal sealing ring, 34 vacuum interlayer, 35 selective absorption coating.

Detailed ways

Fig. 1 shows the tower type solar thermal power generation system of the present invention. The power generation system includes main equipment such as heliostat 1, support tower 2, heat absorber 3, heat storage system, steam turbine 4 and generator 5, and auxiliary equipment such as pumps. The support tower 2 is the benchmark of the power generation system. The heliostat 1 is arranged around the support tower 2. The heat absorber 3 is located on the top of the support tower 1. According to the flow direction of the heat transfer fluid, the feed water pump 8 and the deaerator 6 and The heat absorber 3 is connected sequentially through pipelines, the feed water pump 8 can be placed on the support tower 2 or on the ground, the heat absorber 3 and the steam turbine 4 are connected through pipelines, the generator 5 and the steam turbine 4 are fixedly connected by a coupling, and the steam turbine 5 and the The condensers 7 are connected by pipelines. The high temperature molten salt storage tank 9, the low temperature molten salt storage tank 10, the water/steam-molten salt heat exchanger 11 and the molten salt steam generator 12 together form a thermal storage system, and the molten salt in the water/steam-molten salt heat exchanger 11 The side is connected to the high-temperature molten salt storage tank 9 and the low-temperature molten salt storage tank 10 respectively through pipelines, and the steam side of the water/steam-molten salt heat exchanger 11 is connected to the heat absorber 3 and the steam turbine 5 respectively through steam pipelines, and the water/steam - The water side of the molten salt heat exchanger 11 is connected to the deaerator 6 . The molten salt steam generator 12 is connected to the high temperature molten salt storage tank 9 and the low temperature molten salt storage tank 10 respectively through pipelines. The control valve 13 is arranged on the pipeline of the system for adjustment during operation of different operation modes. The concentrating radiant energy flow 14 is formed by converging the solar light by the heliostat 1 for projecting onto the surface of the heat absorber 3 . The feed water 15 is the heat transfer fluid in the system, which is pumped by the feed water pump 8 from the deaerator 6 to the heat absorber 3 for heat absorption or pumped by the feed water pump 8 from the deaerator 6 to the molten salt steam generator 12 heat exchange in. The superheated steam 16 is the heat transfer fluid in the system and the working medium that drives the steam turbine 4 to do work to drive the generator 5 to generate electricity. The superheated steam 16 is generated by the heat absorber 3 or the molten salt steam generator 12 .

The concentrated radiant energy flow 14 converged by the heliostat 1 is projected onto the surface of the heat absorber 3, heating the feed water 15 pumped from the deaerator 6 by the feed water pump 8, and the feed water 15 is heated in the heat absorber 3 to The superheated steam 16 is transported to the steam turbine 4 to do work to drive the generator 5 to generate electricity. The steam exhausted from the steam turbine is condensed by the condenser 7 and then flows back to the deaerator 6 under the action of the feedwater pump 8 to complete solar heating of the feedwater 15 to directly generate superheated steam 16 for power generation. process. The superheated steam 16 produced by the heat absorber 3 can also flow into the water/steam-molten salt heat exchanger 11 of the heat storage system to exchange heat with the heat storage working medium molten salt 17 flowing out from the low-temperature molten salt storage tank 10. After the exchange, the molten salt 17 is heated to high-temperature molten salt and stored in the high-temperature molten salt storage tank 9, and the superheated steam 16 is cooled to feed water 15, flows back to the deaerator 6, and continues to be pumped back to the heat absorber 3 as a heat transfer medium for absorption. hot. When the solar energy is insufficient, the heat storage system is put into operation, and the molten salt 17 flowing out from the high-temperature molten salt storage tank 9 is heated by the molten salt steam generator 9 to the feed water 15 pumped from the deaerator 6 through the feed water pump 8 to the superheated steam 16 , the superheated steam 16 is sent to the steam turbine 4 to do work to drive the generator 5 to generate electricity, and the exhaust steam of the steam turbine is condensed by the condenser 7 and then flows back to the deaerator 6 under the action of the feed water pump 8 to complete the independent power generation process of the thermal storage system.

FIG. 2 shows the direct steam generation type vacuum heat absorbing tube water/steam heat absorber of the present invention, which is composed of multiple vacuum heat absorbing tubes 18 , water feed header 19 and steam header 20 . The steam header 20 is located at the top of the heat absorber, and the feed water header 19 is located at the bottom of the heat absorber. A plurality of vacuum heat absorbing pipes 18 are connected in series by welding to form a vacuum heat absorbing pipe string. The box 19 is welded and connected, and the top of the vacuum heat-absorbing pipe string is welded and connected with the steam header 20. The series and parallel connections of the vacuum heat absorbing pipe strings form a cavity type, flat plate type or cylinder type water/steam heat absorber.

The structure of the vacuum heat absorbing tube 18 is shown in Figure 3. The vacuum heat absorbing tube 18 is composed of a metal inner tube 31, a glass outer tube 32 and a glass-to-metal sealing ring 33, and one end of the metal inner tube 31 is welded to the glass-to-metal sealing ring 33 , the glass outer tube 32 is welded to the other end of the glass metal sealing ring 33 . There is a vacuum interlayer 34 between the glass outer tube 32 and the metal inner tube 31, and the outer surface of the metal inner tube 31 is coated with a selective absorption coating 35, which has a high absorption ratio in the solar spectrum range and has a high absorption ratio in the infrared band. The lower emission ratio realizes the efficient absorption of solar energy and the lower radiation heat loss between the outer wall of the metal inner tube 31 and the glass outer tube 32, which ensures that the heat absorber of the present invention can have higher thermal efficiency. A plurality of vacuum heat-absorbing tubes 18 are connected in series to form a sufficient length, and the vacuum heat-absorbing tube strings are arranged in at least two parallel rows to reduce the transmission loss. The arrangement of the two rows of vacuum heat-absorbing tube strings is shown in Figure 4. The front-row vacuum heat-absorbing tube strings and the rear-row vacuum heat-absorbing tube strings are alternately arranged to ensure that the concentrated radiation energy flow 14 put into it can be completely absorbed by the metal inner tube 31 of the vacuum heat-absorbing tube 18 . During work, the concentrated radiant energy flow 14 is projected onto the surface of the glass outer tube 32 of the vacuum heat absorbing tube 18, a small part of the energy is reflected to the external environment and absorbed by the glass outer tube 32, and most of the radiant energy passes through the glass outer tube 32 to On the outer surface of the metal inner tube 31, most of the energy is absorbed to heat the metal inner tube 31, and a small part of the energy is reflected. The feed water 15 flows into the feed water header 19 and then flows into the vacuum heat absorption pipe 18 to conduct convective heat exchange with the metal inner pipe 31 and then flows into the steam header 20, and the steam header 20 flows out of the superheated steam 16 to complete the conversion of solar energy to water/steam heat energy .

Fig. 5 shows that the present invention has the vacuum heat absorbing pipe water/steam heat absorber with steam-water separator, and this heat absorber is made of many vacuum heat-absorbing pipes 18, feedwater header 19, steam header 20, steam-water separator 21 and circulating water pump 22 form. The steam header 20 is located at the top of the heat absorber, the feedwater header 19 is located at the bottom of the heat absorber, the vacuum heat absorbing pipes 18 are connected in series by welding to form a sufficient length of vacuum heat absorbing pipe strings, and the lower part of the vacuum heat absorbing pipe strings is connected with the The feedwater header 19 is welded and connected, and the top of the vacuum heat-absorbing pipe string is connected with the steam-water separator 21. Vacuum heat absorbing tube strings are arranged in parallel in at least 2 rows to reduce permeation loss. When working, the concentrated radiation energy flow 14 is projected onto the surface of the vacuum heat-absorbing tube 18, a small part of the energy is reflected to the external environment and absorbed by the glass outer tube 32, and most of the radiant energy passes through the glass outer tube 32 to the outside of the metal inner tube 31 On the surface, most of the energy is absorbed to heat the metal inner tube 31, and a small part of the energy is reflected. After the feed water 15 flows into the feed water header 19, it flows into the vacuum heat-absorbing pipe 18 and conducts convective heat exchange with the metal inner pipe 31, and then flows into the steam-water separator 21. The separators 21 absorb heat in multiple cycles. The saturated steam 23 generated in the steam-water separator 21 flows into the vacuum heat absorption pipe 18 connected to the steam header 20 to be heated as superheated steam 16 flows into the steam header 20 and then flows out to complete the conversion of solar energy to water/steam heat energy.

Claims (5)

1. a tower type solar thermal power generation system of vacuum heat absorbing tube heat absorber, it is characterized in that described solar thermal power generation system comprises heliostat (1), support tower (2), heat absorber (3), heat storage system, steam turbine (4) and generator (5); the heliostat (1) is arranged around the support tower (2), and the heat absorber (3) is located on the top of the support tower (1); The water pump (8), deaerator (6) and heat absorber (3) are connected sequentially through pipelines: the feed water pump (8) is placed on the supporting tower (2) or on the ground; the heat absorber (3) and the steam turbine (4) The generator (5) and the steam turbine (4) are fixedly connected by a coupling, and the steam turbine (5) and the condenser (7) are connected by a pipeline; the heat storage system is composed of high-temperature molten salt storage tank (9), low temperature molten salt storage tank (10), water/steam-molten salt heat exchanger (11) and molten salt steam generator (12); water/steam-molten salt heat exchanger (11) The steam side is connected to the heat absorber (3) and the steam turbine (5) respectively through steam pipes, and the water side of the water/steam-molten salt heat exchanger (11) is connected to the deaerator (6) through pipes; the water/steam- The molten salt side of the molten salt heat exchanger (11) is connected to the high temperature molten salt storage tank (9) and the low temperature molten salt storage tank (10) through pipelines, and the molten salt steam generator (12) is connected to the high temperature molten salt storage tank through pipelines (9) is connected with low-temperature molten salt storage tank (10); described heat absorber (3) is made up of multiple vacuum heat absorbing pipes (18), feedwater header (19), steam header (20); The header (20) is located on the top of the heat absorber (3), and the feedwater header (19) is located at the bottom of the heat absorber (3); multiple vacuum heat absorbing pipes (18) are connected in series by welding to form a vacuum absorber of sufficient length. The heat pipe string, the bottom of the vacuum heat absorbing pipe string (18) is welded with the water supply header (19), and the top of the vacuum heat absorbing pipe string (18) is connected with the steam-water separator (21). 2. according to the tower type solar thermal power generation system of vacuum heat absorbing tube heat absorber according to claim 1, it is characterized in that at least 2 rows of described vacuum heat absorbing tube strings are arranged side by side; Saturated steam (23) flows into the vacuum heat absorbing pipe (18) connected with the steam header (20) and is heated to become superheated steam (16). After flowing into the steam header (20), it flows out. 3. A tower type solar thermal power generation system of a vacuum heat absorbing tube heat absorber, characterized in that said solar thermal power generation system comprises a heliostat (1), a support tower (2), a heat absorber (3), heat storage system, steam turbine (4) and generator (5); the heliostat (1) is arranged around the support tower (2), and the heat absorber (3) is located on the top of the support tower (1); The water pump (8), deaerator (6) and heat absorber (3) are connected sequentially through pipelines: the feed water pump (8) is placed on the supporting tower (2) or on the ground; the heat absorber (3) and the steam turbine (4) The generator (5) and the steam turbine (4) are fixedly connected by a coupling, and the steam turbine (5) and the condenser (7) are connected by a pipeline; the heat storage system is composed of high-temperature molten salt storage tank (9), low temperature molten salt storage tank (10), water/steam-molten salt heat exchanger (11) and molten salt steam generator (12); water/steam-molten salt heat exchanger (11) The steam side is connected to the heat absorber (3) and the steam turbine (5) respectively through steam pipes, and the water side of the water/steam-molten salt heat exchanger (11) is connected to the deaerator (6) through pipes; the water/steam- The molten salt side of the molten salt heat exchanger (11) is connected to the high temperature molten salt storage tank (9) and the low temperature molten salt storage tank (10) through pipelines, and the molten salt steam generator (12) is connected to the high temperature molten salt storage tank through pipelines (9) is connected with low-temperature molten salt storage tank (10); Described heat absorber is made of many root vacuum heat-absorbing pipes (18), water feed header (19), steam header (20), steam-water separator (21 ) and a circulating water pump (22); the steam header (20) is located at the top of the heat absorber (3), and the feed water header (19) is located at the bottom of the heat absorber (3); a plurality of vacuum heat absorbing pipes (18) The vacuum heat-absorbing pipe string of sufficient length is formed in series by welding, the lower part of the vacuum heat-absorbing pipe string is welded to the water supply header (19), and the top of the vacuum heat-absorbing pipe string (18) is connected to the steam-water separator (21); At least 2 rows of vacuum heat-absorbing pipe strings are arranged side by side; the saturated steam (23) produced in the steam-water separator (21) flows into the vacuum heat-absorbing pipe (18) connected with the steam header (20) and is heated to superheated steam (16 ) flows into the steam header (20) and then flows out. 4. According to the tower type solar thermal power generation system of the vacuum heat absorbing tube heat absorber described in claim 1 or 2 or 3, it is characterized in that in the described heat absorber (3), the vacuum heat absorbing tube (18) is connected in series The rear arrangement forms cavity type, flat type or cylinder type vacuum heat absorbing pipe strings. 5. The tower type solar thermal power generation system of vacuum heat absorbing tube heat absorber according to claim 1, characterized in that said heliostats (1) are arranged in a fan-shaped arrangement or a circular arrangement.