CN102135270B - Heat accumulation and evaporation integrated device for solar thermal power generation - Google Patents

Abstract

Integrated heat storage and evaporation device for solar thermal power generation. The nozzle (2), the evaporator (3), and the molten salt pump (4) are integrated and installed in the molten salt heat storage tank (1). The evaporator (3) is welded on the bottom of the molten salt heat storage tank (1) and immersed in the molten salt. The nozzles (2) are evenly arranged on the liquid surface of the molten salt. Water passes through the evaporator (3) from bottom to top, and in the process of generating steam, the natural convection of molten salt is strengthened and the thermocline is stratified. The present invention uses passive natural convection enhanced stratification technology, and the evaporator does not need an additional pumping system and long-time preheating.

Description

Integrated heat storage and evaporation device for solar thermal power generation

technical field

The invention relates to a heat storage and evaporation integrated device for solar thermal power generation.

Background technique

A significant advantage of solar thermal power generation technology that is different from other renewable energy power generation technologies is that it can use large-scale heat storage technology to overcome the impact of solar energy's intermittency and instability on power generation characteristics, so that solar thermal power generation can output stable load to the grid to ensure the stability of the grid. At the same time, the existence of the heat storage device increases the power generation capacity and the power generation hours of the solar thermal power station, and reduces the cost of solar thermal power generation. At present, the best solar thermal power storage technology for commercial use is mainly double-tank molten salt heat storage. The low-temperature salt tank stores low-temperature molten salt at about 290°C, which is sent to the heat absorber by the pumping system to generate high-temperature molten salt at a high temperature of about 560°C, and then the high-temperature molten salt is stored in the high-temperature salt tank. At night or when clouds are covered, the high-temperature molten salt is sent out by the pumping system to the evaporator to release heat, and then the low-temperature molten salt flows back to the low-temperature salt tank. The main disadvantages of this technology are the high cost and the large amount of molten salt used. In order to solve the above problems, a single molten salt tank can be used to store heat in a single-tank thermocline using the principle of fluid stratification caused by the different densities of molten salt at different temperatures. The key to the single-tank thermocline heat storage technology lies in the stratification and maintenance of the thermocline. Patents WO201000089, US2010031062, and US4523629 describe the installation of floating plates in molten salt tanks, using the floating plates as thermocline stratification tools, with hot fluid on the upper part of the floating plate and cold fluid on the lower part of the floating plate. During the charging and discharging process, the floating plate can move up and down to prevent the mixing of cold and hot fluids and maintain the stratified state of the thermocline. Under normal circumstances, the capacity of solar thermal power stations is very large. According to the length of heat storage time, tens of thousands of tons of molten salt are required. Therefore, the scale of the heat storage device is very large, so it is difficult to use floating plates in the manufacturing and operation process great. The papers "Thermal Analysis of Solar Thermal Energy Storage in a Molten-Salt Thermocline" and "Molten Salt Thermal Energy Storage in Thermoclines under Different Environment Boundary Conditions" describe an inert solid material such as quartz sand and gravel in molten salt tanks, A technology that utilizes the low thermal conductivity of solid materials to enhance stratification. Patents 200710028077.X and ZL200720051634.5 describe a technology of layering with ceramic foam. No matter what kind of solid material is used as the filler to achieve layering, there are compatibility issues between the material and the molten salt itself, as well as the contamination of the molten salt. Moreover, all the above-mentioned technologies require a set of high-temperature molten salt pumping system to send the high-temperature molten salt to the evaporator to release heat and generate water vapor. Therefore, the system is complex and costly. Although ZL200810198461.9 describes a casing-type molten salt water evaporator, which can be used for heat release and heat transfer of high-temperature molten salt, it cannot realize heat storage.

In short, the existing single-tank thermocline heat storage has the disadvantages of difficulty in thermocline stratification, the need for an additional high-temperature pumping system to send high-temperature molten salt to the evaporator, and the long warm-up time of the external evaporator startup process.

Contents of the invention

The technical problem to be solved by this invention is:

1. Thermocline stratification of single tank thermocline heat storage;

2. The heat storage and the evaporator are independent, requiring an additional pumping system;

3. The warm-up time of the evaporator start-up process is long, which affects the running hours of the power station.

The scheme adopted by the present invention to solve the problems of the technologies described above is:

The present invention adopts a heat storage and evaporation integrated device to solve the above technical problems. The present invention adopts a conventional cylindrical vertical molten salt tank as a molten salt heat storage tank, and its diameter and height are determined according to the heat storage capacity. Multiple evaporators are welded to the bottom of the molten salt heat storage tank. Multiple evaporators can be arranged in regular triangles, squares, circles, etc. in the molten salt tank, and the spacing is determined by the size of the evaporation capacity and maintenance requirements. The evaporator is immersed in the molten salt of the molten salt heat storage tank, and the thermocline stratification of the molten salt heat storage tank is strengthened in the process of steam generation, and the active stratification technology, such as: floating plate, inert packing, is Passive natural tropostratification technology. The bottom of the evaporator is provided with a water header, and the bottom of the water header is provided with a cold water inlet. The upper part of the evaporator is provided with a steam header, and the upper part of the steam header is provided with a steam outlet. The water header and steam header are connected by heat exchange tubes. The outer partition of the evaporator is welded together with the web. The radial plate and the water header are welded together, and the problem of thermocline stratification is solved through the outer shield. A plurality of spray heads are installed between the top of the molten salt heat storage tank and the liquid surface of the molten salt. The arrangement of nozzles can be arranged in regular triangles, squares and circles. The nozzle is installed on the high temperature molten salt pipeline according to the conventional method. The high-temperature molten salt pipeline enters the molten salt tank from the top of the molten salt heat storage tank and branches in a direction parallel to the liquid surface of the molten salt. The branching mode of the molten salt pipeline is designed according to the arrangement of the nozzles. The high-temperature molten salt from the heat absorber enters the molten salt heat storage tank from the top of the molten salt heat storage tank through the distribution and atomization of the nozzle. The molten salt pump is vertically installed on the upper part of the molten salt heat storage tank, and the molten salt pump pumps out the low-temperature molten salt at the bottom of the molten salt and sends it to the heat absorber for heating. The evaporator integrated in the molten salt heat storage tank is immersed in the high-temperature molten salt, and no additional high-temperature molten salt pumping system is needed to send the high-temperature molten salt to the evaporator, which overcomes the conventional evaporator being set outside the heat storage tank, Disadvantages of requiring an additional pumping system to deliver the high temperature molten salt into the evaporator. Since the evaporator is always immersed in high-temperature molten salt, the temperature of the equipment is always high, which does not require long-term preheating when the conventional evaporator starts, which solves the problem of evaporator start-up preheating. Its working process is: the water working medium enters from the bottom of the evaporator, because the evaporator is submerged in the molten salt heat storage. The high-temperature molten salt transfers heat to the water through natural convection, and the water evaporates in the evaporator to produce high-temperature and high-pressure steam that meets the requirements of the steam turbine parameters and enters the steam turbine to generate power. The temperature in the upper part of the evaporator is low, the hot fluid floats on the upper part due to its low density, and the cold fluid sinks naturally to realize the stratification of molten salt. The outer shroud of the evaporator confines natural convection between the evaporator surface and the outer shroud, strengthening and protecting the thermocline.

The present invention utilizes the feature that the cold fluid of the evaporator requires molten salt to conduct heat and evaporate, and in the process of water evaporation, the molten salt outside the evaporator is naturally convected to realize natural stratification without any floating plate or filler and pumping system. The structure is simple, the start-up time of the steamer is short, and the heat storage and evaporation are integrated.

Description of drawings

Fig. 1 Structural diagram of heat storage and evaporation integrated device;

Figure 2 The front view of the evaporator;

Figure 3 top view of the evaporator;

In the figure: 1 molten salt heat storage tank, 2 nozzle, 3 evaporator, 4 molten salt pump, 5 steam header, 6 heat exchange tube, 7 water header, 8 supporting legs, 9 outer shield, 10 spoke plate.

Detailed ways

Fig. 1 is a structural diagram of the heat storage and evaporation integrated device of the present invention. A spray head 2 , an evaporator 3 and a molten salt pump 4 are arranged in the molten salt heat storage tank 1 . A plurality of nozzles 2 are installed between the top of the molten salt heat storage tank 1 and the liquid surface of the molten salt, above the liquid surface of the molten salt, and are evenly distributed in a regular triangle, square or circle. The nozzle is installed on the high temperature molten salt pipeline according to the conventional method. The high-temperature molten salt pipeline enters the molten salt tank from the top of the molten salt heat storage tank and branches in a direction parallel to the liquid surface of the molten salt. The branching mode of the molten salt pipeline is designed according to the arrangement of the nozzles. After the high-temperature molten salt from the heat absorber is diverted through the evenly distributed nozzles 2, it falls evenly at a low speed on the molten salt liquid surface of the molten salt heat storage tank 1, and the high-temperature molten salt has a low density and naturally stays in the molten salt heat storage 1 upper part. The flow rate and velocity of the molten salt in the diversion are relatively low, which can prevent the disturbance of the molten salt in the molten salt heat storage tank 1 when the fluid enters, and is beneficial to maintain the temperature stratification of the molten salt. A plurality of evaporators 3 are evenly distributed and immersed in the molten salt in the molten salt heat storage tank 1 , arranged in a regular triangle, square or circle, etc. and welded to the bottom of the molten salt heat storage tank 1 . The low-temperature water enters from the bottom of the evaporator 3, the cold water flows in the evaporator from bottom to top, and the surrounding high-temperature molten salt heats the cold water to generate steam with required parameters. During the steam generation process of the evaporator, the surrounding high-temperature molten salt will naturally produce natural convection, the low-temperature molten salt with high density will sink to the bottom of the molten salt heat storage tank 1, and the high-temperature molten salt with low density will float up to the molten salt for heat storage The upper part of the tank 1, so that a thermocline is naturally formed in the molten salt heat storage tank 1. The molten salt pump 4 vertically installed on the top of the molten salt heat storage tank 1 goes deep into the molten salt until it is close to the bottom of the molten salt heat storage tank 1, and the low-temperature molten salt is drawn out from the bottom of the molten salt heat storage tank 1 and pumped to The heat absorbed in the heat absorber generates high-temperature molten salt, and the high-temperature molten salt flows back into the molten salt heat storage tank 1 from the top of the molten salt heat storage tank 1 through the nozzle 2 .

Figure 2 and Figure 3 are the front view and top view of the evaporator respectively. The heating surface of the evaporator 3 is formed by a bundle of heat exchange tubes 6 . A plurality of heat exchange tubes 6 are arranged in a circular or triangular manner, the lower ends of the heat exchange tubes 6 are inserted into the cylindrical closed water header 7, and the upper ends of the heat exchange tubes 6 are inserted into the cylindrical closed steam header 5 . There is enough space between each heat exchange tube 6 in the heat exchange tube bundle, and they cannot be closely arranged. The water header 7 and the steam header 5 are respectively connected by water pipes and steam pipes for water supply and steam outlet. The web 10 is welded together with the water header 7 and the outer partition 9 for fixing. In order to eliminate the stress that may be caused by the difference in expansion between the tube bundle composed of the outer shield 9 and the heat exchange tubes 6, the web plate 10 and the steam header 5 are in contact but not fixed, and can slide relative to each other, so that the heat exchange tubes 6 The formed tube bundle, water header 7 and steam header 5 can move up and down relative to the outer shroud 9 . The supporting legs 8 are welded together with the outer shield 9 and the water header 7, and are welded to the bottom of the molten salt heat storage tank 1 to prevent the evaporator 3 from drifting in the molten salt heat storage tank 1. The evaporator 3 is immersed in the molten salt heat storage tank 1 together with the outer shield 9 . The cold water enters from the water header 7, and the molten salt heat transfer feed water at the lower part becomes low-temperature molten salt. As the water rises in the heat exchange tube 6, it is gradually heated by the surrounding high-temperature molten salt. Therefore, the molten salt is in the height direction. The higher the position, the higher the temperature. There is a severe convection area between the outer partition 9 and the heat exchange tube 6. The heat-exchanged low-temperature molten salt will naturally flow out from the bottom of the outer partition 9, and the high-temperature molten salt will flow out from the outer partition. 9 The upper part flows in, which not only realizes the heating of the water, but also strengthens the stratification of the thermocline.

Claims (4)

1. An integrated heat storage and evaporation device for solar thermal power generation, characterized in that: the integrated heat storage and evaporation device includes a molten salt heat storage tank (1), a nozzle (2), and an evaporator (3) and the molten salt pump (4); the nozzle (2), the evaporator (3) and the molten salt pump (4) are integrated and installed in the molten salt heat storage tank (1); the molten salt heat storage tank (1) is evenly arranged with A plurality of nozzles (2), the nozzles (2) are installed between the top of the molten salt heat storage tank (1) and the liquid surface of the molten salt, and are located above the liquid surface of the molten salt; multiple evaporators (3) are immersed in the molten salt and welded on the bottom of the molten salt heat storage tank (1), and evenly arranged; The evaporator (3) includes a heat exchange tube bundle composed of a plurality of heat exchange tubes (6), a steam header (5), a water header (7), support legs (8), and an outer shield (9) and the spoke plate (10); the water header (7) is located at the bottom of the evaporator (3); the steam header (5) is located at the upper part of the evaporator (3); the The lower end of the heat exchange tube (6) is inserted into the water header (7), and the upper end of the heat exchange tube (6) is inserted into the steam header (5); the water header (7) and the outer shield ( 9) Weld together through the web (10); the web (10) is welded to the outer cover (9), and the web (10) is in contact with the steam header (5) and slides relatively; the supporting legs (8) Located on the water header (7) and the outer shield (9), and welded to the bottom of the molten salt heat storage tank (1). the 2. The heat storage and evaporation integrated device for solar thermal power generation according to claim 1, characterized in that: in the heat exchange tube bundle, a plurality of heat exchange tubes (6) are arranged in a circular or triangular manner, There is a space between each heat exchange tube (6). the 3. The heat storage and evaporation integrated device for solar thermal power generation according to claim 1, characterized in that: the molten salt pump (4) is vertically installed on the top of the molten salt heat storage tank (1), and Insert into the molten salt until close to the bottom of the molten salt storage tank (1). the 4. The heat storage and evaporation integrated device for solar thermal power generation according to claim 1, characterized in that: the nozzle (2) is installed on the high-temperature molten salt pipeline in the molten salt heat storage tank (1) , the high-temperature molten salt pipeline enters the molten salt tank (1) from the top of the molten salt heat storage tank (1), and branches in a direction parallel to the liquid surface of the molten salt. the

Images