CN108561282B - Trough type direct steam and molten salt combined thermal power generation system - Google Patents

Abstract

The invention relates to a trough type direct steam and molten salt combined thermal power generation system. The system comprises a direct steam system, a turbine power generation system, a feedwater regenerative system and a condensing system; the direct steam system comprises a direct steam solar heat collection field, a steam heat exchanger, a medium-temperature heat storage device, a water mixer, a gas-liquid separator and the like; the solar heat collection system also comprises a molten salt heat collection system with the function of a superheated steam section, wherein the molten salt heat collection system comprises a trough type molten salt solar heat collection field, a high-temperature molten salt tank, a high Wen Lengrong molten salt tank, a superheater and the like. When the system works, the preheating and evaporating processes of water in the system are completed in a direct steam solar heat collection field in a direct steam system, and the superheating and reheating processes are completed in a molten salt superheater and a reheater in a molten salt system; the high-temperature working medium at the outlet of the molten salt system only exchanges heat with the superheater and the reheater, so that the heat transfer temperature difference inside the heat exchanger is reduced, the exergy loss of the heat exchanger is reduced, and the efficiency of the thermal power generation system can be improved by 15-20%.

Description

A trough type direct steam and molten salt combined thermal power generation system

Technical field

The invention belongs to the technical field of solar power generation, and specifically relates to a trough solar thermal power generation system.

Background technique

Solar energy is the most widely distributed and abundant renewable energy source. In order to improve the quality and utilization efficiency of solar energy, high-temperature solar thermal utilization has attracted widespread attention. Trough solar thermal power generation is currently the most mature and lowest-cost solar thermal power generation technology. Traditional conventional solar trough thermal power generation systems include solar thermal collection systems, heat storage systems, heat transmission and heat exchange systems, and power generation systems. The solar thermal collection system includes high-temperature vacuum collector tubes, concentrators, tracking mechanisms, and related connecting pipes and valves.

For power stations with heat transfer oil and molten salt working fluids, the concentrator focuses the solar radiation on the trough vacuum collector tube on the focal line of the parabolic trough, and the heat transfer fluid is heated by convection heat exchange with the wall of the collector tube. The heated heat transfer fluid then passes through a series of heat exchangers to generate steam, and the energy of the steam generates electricity through the steam power cycle. After heating the steam, the heat transfer fluid returns to the solar collector field. The trough solar thermal power generation system has a long collector field heating circuit, so the heat loss of the trough thermal power generation system mainly comes from the loss of the collector field pipes and collector tubes. The temperature of the currently commercially operated trough thermal power generation system can reach 400°C. In order to improve the system power generation efficiency, the operating temperature of the trough thermal power generation system has a tendency to be further increased. Currently, the maximum temperature of experimental power stations using molten salt as the heat transfer medium can reach 550°C. As the temperature of the collector field increases, the heat loss of the collector tube increases exponentially and the heat loss of the connecting pipes increases significantly. Therefore, reducing the heat loss of the trough collector field is of great significance to improving the efficiency of the thermal power generation system. At the same time, in the steam generator, the steam boiling temperature is much lower than the outlet temperature of the collector field, and there is a large exergy loss during the heat exchange process of the heat exchanger.

Trough direct steam power generation technology has higher efficiency, less environmental pollution and lower investment. It is the most promising technology among solar thermal power generation technologies. However, due to the intermittency and periodicity of solar radiation, the control problems of the system are very complicated. In addition, the instability of the two-phase flow in the collector tube and the deterioration of heat transfer in the superheated section also limit the development of direct steam power generation technology.

Contents of the invention:

In order to improve the efficiency of the trough thermal power generation system and reduce the cost of power generation, the present invention proposes a trough type direct steam and molten salt combined thermal power generation system.

A trough-type direct steam and molten salt combined thermal power generation system includes a direct steam system 2, a steam turbine power generation system 5, a feed water heat recovery system 3 and a condensation system 4;

The steam turbine power generation system 5 includes a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder, a steam turbine low-pressure cylinder and a generator set;

The feed water recuperation system 3 includes a high-pressure heat exchanger, a low-pressure heat exchanger, a deaerated water tank, a pre-pump and a condensate water pump; the low-pressure heat exchanger is connected to a low-pressure cylinder; the high-pressure heat exchanger is connected to a turbine high-pressure cylinder Connection; the deaeration water tank is connected to the steam turbine medium-pressure cylinder, low-pressure heat exchanger, pre-pump and high-pressure heat exchanger respectively;

The condensation system 4 includes a cooling tower and a condenser; the condenser is connected to the steam turbine low-pressure cylinder and the inlet of the condensation water pump of the feed water reheat system 3 respectively;

The direct steam system 2 includes a direct steam solar heat collecting field 20, a water pump 21, a liquid storage tank 22, a steam heat exchanger 23, a medium temperature heat storage device 24, a water mixer 25 and a gas-liquid separator 26; the direct steam solar energy The inlet of the heat collecting field 20 is connected in series with the water pump 21, the liquid storage tank 22 and the water mixer 25; the outlet of the direct steam solar heat collecting field 20 is connected with the inlet of the gas-liquid separation 26; the gas phase outlet of the gas-liquid separator 26 is connected with The steam inlet of the superheater 15 and the liquid phase outlet of the gas-liquid separator 26 are connected to the inlet of the water mixer 25; the steam heat exchanger 23 is connected in parallel with the direct steam solar heat collecting field 20; the medium temperature heat storage device 24 enters The outlets are respectively connected to the heat storage medium inlet and outlet of the steam heat exchanger 23;

It also includes a molten salt heat collection system 1, which includes a trough-type molten salt solar heat collection field 10, a high-temperature hot molten salt tank 18, a high-temperature cold molten salt tank 11, a molten salt pump 12, and an expansion tank 13 , molten salt mixer 14, superheater 15, reheater 16 and molten salt diverter 17; the entrance of the molten salt solar collector field 10 is connected in series with a molten salt pump 12, an expansion tank 13 and a molten salt mixer 14. , the high-temperature cold molten salt tank 11 is connected in parallel through the second valve 110 in series on the pipeline between the inlet of the molten salt solar collector field 10 and the outlet of the molten salt pump 12; the outlets of the molten salt solar collector field 10 are connected in series The molten salt diverter 17, the overheating mechanism and the molten salt mixer 14 are connected. The overheating mechanism is composed of a parallel superheater 15 and a reheater 16; between the outlet of the molten salt solar collector field 10 and the inlet of the molten salt diverter 17 The high-temperature molten salt tank 18 is connected in parallel through the first valve 19 in series on the pipeline between them. The outlet of the high-temperature molten salt tank 18 is connected in series with the pump 111; the steam outlet of the superheater 15 is connected to the steam inlet of the high-pressure cylinder of the steam turbine; so The steam outlet of the reheater 16 is connected to the steam inlet of the steam turbine intermediate pressure cylinder;

The molten salt heat collection system 1 has the function of a superheated steam section;

During operation, the preheating and evaporation process of water in the system is completed in the direct steam solar collector field 20 in the direct steam system 2, and the superheating and reheating processes are completed in the molten salt superheater 16 and reheater 15 in the molten salt system 1. Finish.

The further limited technical solutions are as follows:

The medium-temperature heat storage system 24 is a phase change energy storage device, a double-tank molten salt energy storage device, a single-tank inclined temperature layer energy storage device, or a latent heat concrete heat storage device.

The direct steam solar collector field 20 includes a trough direct steam trough collector tube, a trough concentrator, a tracking mechanism, a steam connection pipeline, a pump and a valve, which are connected according to the connection relationship of a conventional solar collector field.

The molten salt solar collector field 10 includes a trough molten salt collector tube, a trough concentrator, a tracking mechanism, molten salt connecting pipelines and related pumps and valves, which are connected according to the connection relationship of a conventional solar collector field.

The condensation system 4 is a water-cooled condenser or an air-cooled condenser.

The steam turbine low-pressure cylinder is composed of two or more low-pressure cylinders connected in series.

The beneficial technical effects of the present invention are reflected in the following aspects:

1. By using a trough-type direct steam and molten salt combined thermal power generation system, the two systems are effectively combined to complement each other. What is different from traditional heat collection systems that use a single working fluid is that the preheating and evaporation process of water is completed in the direct steam solar heat collection field in the direct steam system, and the superheating and reheating processes are completed in the molten salt superheating in the molten salt system. The heater and reheater are completed.

2. The high-temperature working fluid at the outlet of the molten salt system only exchanges heat with the superheater and reheater, reducing the heat transfer temperature difference inside the heat exchanger and reducing the exergy loss of the heat exchanger. At the same time, the length of the high-temperature molten salt circuit in the collector field is reduced by 60 to 70% compared to the traditional molten salt collector system, which can reduce the heat loss of the collector field by 30 to 40% on sunny days during the day and reduce the energy consumption of heat preservation and tracing by 50% at night. ~60%, so the present invention can increase the efficiency of the thermal power generation system by 15-20%.

3. Compared with the traditional steam system, the direct steam system eliminates the superheated steam section. The gas-liquid separator installed at the outlet of the direct steam solar collector field can ensure steam output with stable parameters, allowing the direct steam solar collector field to use a larger water flow rate, improve the heat transfer stability of the two-phase flow, and eliminate the traditional The deterioration of heat transfer in the superheated steam section of the direct steam system will damage the collector tube. Using a high-temperature molten salt circuit to reheat and superheat steam can improve the stability of output steam parameters and improve system operation stability.

4. The present invention can significantly reduce the usage of molten salt, significantly reduce the initial investment cost of the power station, and reduce the unit power cost.

Description of the drawings

Figure 1 shows a schematic diagram of a trough-type direct steam and molten salt combined thermal power generation system of the present invention.

Figure 2 shows a schematic diagram of the molten salt system of the present invention.

Figure 3 shows a schematic diagram of the direct steam system of the present invention.

The serial numbers in the above picture are: molten salt collector system 1, direct steam collector system 2, water supply heat recovery system 3, condensation system 4, steam turbine power generation system 5, trough molten salt solar collector field 10, high temperature cold molten salt tank 11 , molten salt pump 12, expansion tank 13, molten salt mixer 14, superheater 15, reheater 16, molten salt diverter 17, high temperature hot molten salt tank 18, first valve 19, direct steam solar collector field 20 , water pump 21, liquid storage tank 22, steam heat exchanger 23, medium temperature heat storage device 24, water mixer 25, gas-liquid separator 26, steam valve 27, second valve 110, pump 111.

Detailed ways:

In order to further illustrate the characteristics and functions of the present invention, the present invention will be further described in detail through embodiments in conjunction with the drawings.

Referring to Figure 1, a trough type direct steam and molten salt combined thermal power generation system includes a direct steam system 2, a steam turbine power generation system 5, a feed water heat recovery system 3, a condensation system 4 and a molten salt heat collection system 1.

The steam turbine power generation system 5 includes a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder, a steam turbine low-pressure cylinder and a generator set. The steam turbine low-pressure cylinder is composed of three low-pressure cylinders of level two or higher in series.

The feed water recuperation system 3 includes a high-pressure heat exchanger, a low-pressure heat exchanger, a deaerated water tank, a pre-pump and a condensate pump; the low-pressure heat exchanger is connected to a low-pressure cylinder; the high-pressure heat exchanger is connected to a high-pressure cylinder of a steam turbine; The deaerated water tank is connected to the steam turbine medium-pressure cylinder, low-pressure heat exchanger, pre-pump and high-pressure heat exchanger respectively.

The condensation system 4 is a water-cooled condenser, including a cooling tower and a condenser; the condenser is connected to the steam turbine low-pressure cylinder and the inlet of the condensation water pump of the feed water recuperation system 3 respectively.

Referring to Figure 2, the direct steam system 2 includes a direct steam solar heat collecting field 20, a water pump 21, a liquid storage tank 22, a steam heat exchanger 23, a medium temperature heat storage device 24, a water mixer 25 and a gas-liquid separator 26. The direct steam solar collector field 20 includes a trough direct steam trough collector tube, a trough concentrator, a tracking mechanism, a steam connection pipeline, a pump and a valve, which are connected according to the connection relationship of a conventional solar collector field; the direct steam solar collector The inlet of the thermal field 20 is connected in series with a water pump 21, a liquid storage tank 22 and a water mixer 25. The outlet of the direct steam solar collector field 20 is connected to the inlet of the gas-liquid separator 26; the gas phase outlet of the gas-liquid separator 26 is connected to the steam inlet of the superheater 15; the liquid phase outlet of the gas-liquid separator 26 is connected to the water mixer 25 entrance. The steam heat exchanger 23 is connected in parallel with the direct steam solar collector field 20 . The medium temperature heat storage system 24 is a phase change energy storage device, and the inlet and outlet of the medium temperature heat storage device 24 are respectively connected to the heat storage medium inlet and outlet of the steam heat exchanger 23.

Referring to Figure 3, the molten salt heat collection system 1 has the function of a superheated steam section; the molten salt heat collection system 1 includes a trough molten salt solar heat collection field 10, a high-temperature hot molten salt tank 18, a high-temperature cold molten salt tank 11, molten salt Pump 12, expansion tank 13, molten salt mixer 14, superheater 15, reheater 16 and molten salt diverter 17; molten salt solar collector field 10 includes trough molten salt collector tube, trough concentrator, tracking The mechanism, molten salt connecting pipelines and related pumps and valves are connected according to the connection relationship of conventional solar collector fields. The entrance of the molten salt solar collector field 10 is connected in series with the molten salt pump 12, the expansion tank 13 and the molten salt mixer 14. The pipeline between the entrance of the molten salt solar collector field 10 and the outlet of the molten salt pump 12 is connected in series. The second valve 110 is connected in parallel with the high-temperature cold molten salt tank 11; the outlet of the molten salt solar collector field 10 is connected in series with the molten salt diverter 17, the overheating mechanism and the molten salt mixer 14. The overheating mechanism is composed of a parallel superheater. The high-temperature thermal molten salt tank 18 is connected in parallel through the first valve 19 in series on the pipeline between the outlet of the molten salt solar collector field 10 and the inlet of the molten salt diverter 17. The high-temperature thermal molten salt tank 18 is The outlet of the tank 18 is connected in series with the pump 111; the steam outlet of the superheater 15 is connected to the steam inlet of the high-pressure cylinder of the steam turbine; the steam outlet of the reheater 16 is connected to the steam inlet of the intermediate-pressure cylinder of the steam turbine.

The main steam temperature of the steam turbine used in the steam turbine power generation system 5 is 540°C, the pressure is 13Mpa, the reheat steam temperature is 540°C, the pressure is 1.8Mpa, and the feed water temperature is 222°C.

During operation, the preheating and evaporation process of water in the system is completed in the direct steam solar collector field 20 in the direct steam system 2, and the superheating and reheating processes are completed in the molten salt superheater 16 and reheater 15 in the molten salt system 1. Finish.

The specific working principle is explained as follows:

The water in the liquid storage tank 22 of the direct steam system 2 is transported to the direct steam solar collector field 20 through the water pump 21. The water is preheated and boiled in the direct steam solar collector field 20, and is converted from direct steam into a water vapor mixture state of 330°C. The solar heat collecting field 20 outputs, part of the water vapor mixture enters the steam heat exchanger 23 to exchange heat with the medium temperature energy storage device 24, condenses into water and returns to the direct steam solar heat collecting field 20 entrance; the other part passes through the gas-liquid separator 26, and the gas and liquid are separated. The saturated water at the liquid phase outlet of the reactor 26 and the feed water at the outlet of the feed water recuperation system 3 are mixed in the water mixer 25 and returned to the direct steam solar heat collecting field 20. The dry steam at the gas phase outlet of the gas-liquid separator 26 enters the superheater 15. At night or during rainy periods when there is no solar radiation, the steam valve 27 connected to the direct steam solar collector field 20 is closed, as shown in Figure 3. The loop water is preheated by the steam heat exchanger 23, boils, and passes through the gas-liquid separator in turn. 26. The steam passes through the heater 15 to generate high-temperature and high-pressure steam. The liquid phase of the gas-liquid separator 26 returns to the water mixer 25 and is mixed with the feed water to complete a heating cycle again.

The 340°C molten salt in the expansion tank 13 of the molten salt heat collection system 1 is transported to the molten salt solar heat collection field 10 through the molten salt pump 12. It is heated to 550°C in the molten salt solar heat collection field 10, and part of it enters the high-temperature hot molten salt. In the tank 18, part of the molten salt diverter 17 enters the superheater 15 and the reheater 16 respectively for heating steam. The temperature of the molten salt drops to 340°C, and is mixed with part of the molten salt in the high-temperature cold molten salt tank 11 to return to the molten salt solar collector. Field 10. At night or during rainy periods when there is no solar radiation, the first valve 19 and the second valve 110 connected to the molten salt solar collector field 10 are closed, as shown in Figure 2, and the molten salt in the high-temperature hot molten salt tank 18 is pumped through the pump 111 (See Figure 2) It is transported to the superheater 15 and the reheater 16, and the molten salt temperature drops to 340°C and enters the high-temperature cold molten salt tank 11.

In the steam turbine power generation system 5, the superheated steam generated by the heater 15 enters the high-pressure cylinder of the steam turbine power generation system. The high-pressure cylinder completes expansion and work, and enters the medium-pressure cylinder through the gas-liquid separator 26, high-pressure heat exchanger, and reheater 16. Continue to expand and do work; part of the exhaust gas from the medium-pressure cylinder enters the first-stage low-pressure cylinder to continue expanding and doing work, and part enters the deaeration water tank; part of the exhaust gas from the first-stage low-pressure cylinder enters the first-stage low-pressure heat exchanger, and the other part enters the second-stage low-pressure heat exchanger. cylinder; part of the exhaust gas from the second-stage low-pressure cylinder enters the second-stage low-pressure heat exchanger, and the other part enters the third-stage low-pressure cylinder; the exhaust gas from the third-stage low-pressure cylinder enters the condenser, and is condensed into water through the first and second-stage low-pressure heat exchangers. Heat exchanger, deaerated water tank, high pressure heat exchanger, enter direct steam solar collector field 20.

The present invention has been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments. Under the inspiration of the present invention, those of ordinary skill in the art can make improvements and fine-tuning without departing from the spirit of the present invention. All fall within the protection of the present invention.

Claims (6)

1. A trough type direct steam and molten salt combined thermal power generation system, including a direct steam system (2), a steam turbine power generation system (5), a feed water heat recovery system (3) and a condensation system (4); The steam turbine power generation system (5) includes a steam turbine high pressure cylinder, a steam turbine intermediate pressure cylinder, a steam turbine low pressure cylinder and a generator set; The feed water recuperation system (3) includes a high-pressure heat exchanger, a low-pressure heat exchanger, a deaerated water tank, a pre-pump and a condensate pump; the low-pressure heat exchanger is connected to a low-pressure cylinder; the high-pressure heat exchanger is connected to a steam turbine The high-pressure cylinder is connected; the deaeration water tank is connected to the steam turbine medium-pressure cylinder, low-pressure heat exchanger, pre-pump and high-pressure heat exchanger respectively; The condensation system (4) includes a cooling tower and a condenser; the condenser is connected to the steam turbine low-pressure cylinder and the inlet of the condensation water pump of the feed water recuperation system (3) respectively; it is characterized by: The direct steam system (2) includes a direct steam solar collector field (20), a water pump (21), a liquid storage tank (22), a steam heat exchanger (23), a medium temperature heat storage device (24), and a water mixer (25) and gas-liquid separator (26); the entrance of the direct steam solar collector field (20) is connected in series with a water pump (21), a liquid storage tank (22) and a water mixer (25); the direct steam solar collector The outlet of the thermal field (20) is connected to the inlet of the gas-liquid separator (26); the gas phase outlet of the gas-liquid separator (26) is connected to the steam inlet of the superheater (15), and the liquid phase of the gas-liquid separator (26) The outlet is connected to the inlet of the water mixer (25); the steam heat exchanger (23) is connected in parallel to the direct steam solar heat collecting field (20); the inlet and outlet of the medium temperature heat storage device (24) are connected to steam heat exchangers respectively. The heat storage medium inlet and outlet of the device (23); It also includes a molten salt heat collection system (1). The molten salt heat collection system (1) includes a trough molten salt solar heat collection field (10), a high-temperature hot molten salt tank (18), and a high-temperature cold molten salt tank (11). ), molten salt pump (12), expansion tank (13), molten salt mixer (14), superheater (15), reheater (16) and molten salt diverter (17); the molten salt solar collector The inlet of the thermal field (10) is connected in series with the molten salt pump (12), the expansion tank (13) and the molten salt mixer (14), and the inlet of the molten salt solar thermal field (10) and the outlet of the molten salt pump (12) The high-temperature cold molten salt tank (11) is connected in parallel with the high-temperature cold molten salt tank (11) through the second valve (110) connected in series; the outlet of the molten salt solar collector field (10) is connected in series with the molten salt diverter (17), the superheater mechanism and molten salt mixer (14), the overheating mechanism is composed of a parallel superheater (15) and a reheater (16); the outlet of the molten salt solar collector field (10) and the molten salt diverter (17) The high-temperature hot-melt salt tank (18) is connected in parallel through the first valve (19) in series on the pipeline between the inlets, and the outlet of the high-temperature hot-melt salt tank (18) is connected in series with a pump (111); the superheater (15) The steam outlet is connected to the steam inlet of the high-pressure cylinder of the steam turbine; the steam outlet of the reheater (16) is connected to the steam inlet of the intermediate-pressure cylinder of the steam turbine; The molten salt heat collection system (1) has the function of a superheated steam section; When working, the preheating and evaporation process of water in the system is completed in the direct steam solar collector field (20) in the direct steam system (2), and the superheating and reheating processes are completed in the molten salt in the molten salt collector system (1). The superheater (15) and reheater (16) are completed. 2. A trough-type direct steam and molten salt combined thermal power generation system according to claim 1, characterized in that the medium temperature heat storage device (24) is a phase change energy storage device or a double-tank molten salt energy storage device. Or a single-tank thermocline energy storage device or a sensible heat concrete heat storage device. 3. A trough-type direct steam and molten salt combined thermal power generation system according to claim 1, characterized in that the direct steam solar collector field (20) includes a trough-type direct steam trough collector tube, a trough-type Concentrator, tracking mechanism, steam connections and pumps and valves. 4. A trough-type direct steam and molten salt combined thermal power generation system according to claim 1, characterized in that the molten salt solar collector field (10) includes a trough-type molten salt collector tube, a trough-type light concentrator device, tracking mechanism, molten salt connecting pipelines and related pumps and valves. 5. A trough-type direct steam and molten salt combined thermal power generation system according to claim 1, characterized in that the condensation system (4) is a water-cooled condenser or an air-cooled condenser. 6. A trough-type direct steam and molten salt combined thermal power generation system according to claim 1, characterized in that the steam turbine low-pressure cylinder is composed of two or more low-pressure cylinders connected in series.