CN106918030A - A kind of coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system - Google Patents

Abstract

The invention discloses a coal-saving high-temperature tower-type solar thermal complementary coal-fired power station integrated system, which is characterized in that the system includes: a plurality of series-connected high-pressure heaters, a plurality of series-connected low-pressure heaters, with an economizer As well as boilers with water walls, steam-water separators, heating devices for coal-fired power stations, solar heaters, high-pressure cylinders for steam turbines, medium-pressure cylinders for steam turbines, low-pressure cylinders for steam turbines and generators. The present invention proposes a new integration scheme that uses molten salt as the intermediate heat exchange working medium of the tower solar heat collection system and simultaneously heats superheated steam and reheated steam, not only using the tower solar heat collector to increase the heat collection temperature of solar heat, but also adopting The two-stage integration method of superheating and reheating can avoid the fluctuation caused by the introduction of solar heat into the coal-fired unit from affecting the normal operation of the steam turbine. The invention is more reasonable than the traditional integration method in terms of high temperature utilization of solar heat, and also has significant thermodynamic and economical advantages.

Description

A coal-saving high-temperature tower-type solar thermal complementary coal-fired power plant integrated system

technical field

The invention belongs to the technical field of power generation in solar thermal complementary coal-fired power plants, and in particular relates to a coal-saving high-temperature tower-type solar thermal complementary coal-fired power plant integrated system.

Background technique

Since the first industrial revolution, fossil energy has played an important role in the progress of human civilization. However, from the photochemical pollution in Europe in the 1950s to the large-scale smog in China today, the environmental pollution caused by fossil energy consumption has seriously affected people's health. Nowadays, energy conservation and emission reduction has become an international consensus, and the development of a diversified energy structure is the goal of all countries. Solar energy is gradually being valued due to its unique advantages. Generally speaking, the development of solar energy has the following advantages: no greenhouse gas (mainly CO ₂ , NO _X ) or toxic gas (SO ₂ , particles) emissions; increase regional/national energy independence; Solar energy is a renewable energy source that is plentiful and cheap. 70% of my country's electricity comes from thermal power plants. Constrained by resources and the environment, the work of energy conservation and emission reduction is becoming more and more important. Many small and medium thermal power plants with high coal consumption are facing the fate of shutting down. Therefore, the complementary utilization of energy has gradually become an important development trend of the energy system. my country's solar energy resources are very rich, and the solar-assisted coal-fired power generation system has gradually attracted everyone's attention. In the traditional solar thermal complementary coal-fired power station system, the solar energy introduced into the system according to the difference of integration position and integration temperature has a great influence on the operating conditions of the steam-water system and the steam turbine. In the traditional solar thermal complementary coal-fired power plant integrated system, the integration method of using trough solar collectors to generate medium and low temperature heat cannot efficiently and rationally utilize solar energy resources. The invention proposes an integration scheme of tower solar energy and conventional coal-fired power plants, which can not only efficiently utilize high-temperature solar heat, but also use the process of solar energy to heat reheat steam as the main means for regulating the temperature of reheat steam. The operating conditions of the steam turbine part have not changed due to the introduction of solar heat, and the safe operation of the solar thermal complementary coal-fired power plant system has also been ensured under the premise of reducing the amount of coal fed.

Contents of the invention

The invention takes the solar thermal complementary coal-fired power station system as a reference system, and proposes a new coal-saving integrated system using a high-temperature tower solar thermal complementary coal-fired power station system by changing the integration position and integration mode of solar energy in the system. The system uses molten salt as the intermediate heat exchange working medium of the tower solar heat collection system, and a new integrated scheme of heating superheated steam and reheated steam at the same time, not only using the tower solar collector to increase the heat collection temperature of solar heat, Moreover, the two-stage integration method of superheating and reheating can avoid the fluctuation caused by the introduction of solar heat into the coal-fired unit from affecting the normal operation of the steam turbine. While the system receives more solar energy, it saves more coal supply and improves the photoelectric conversion efficiency of solar energy. The invention is more reasonable than the traditional integration method in terms of high temperature utilization of solar heat, and also has significant thermodynamic and economical advantages.

The technical scheme adopted in the present invention is:

A coal-saving high-temperature tower-type solar thermal complementary coal-fired power plant integrated system, including multiple high-pressure heaters in series, multiple low-pressure heaters in series, boilers with economizers and water-cooled walls, steam-water separators, fuel-fired Heating devices of coal power stations, solar heaters, high-pressure cylinders of steam turbines, medium-pressure cylinders of steam turbines, low-pressure cylinders of steam turbines and generators.

Among them, the connection relationship and process flow of each component in the system are as follows: the feed water from the first-stage high-pressure heater is introduced into the boiler and heated to the state of saturated steam through the economizer and the heating surface of the water wall, and the saturated steam is separated into steam in the steam-water separator. two parts. Part of the saturated steam flows through the low temperature superheater (low superheater), split screen superheater (split screen), rear screen superheater (back screen) and high temperature superheater (high superheater) in sequence according to the original layout of the heating surface of the coal-fired power station. Due to the coal-saving mode, the steam temperature above the outlet will be reduced. Another part of saturated steam is introduced into the solar heater to exchange heat with high-temperature molten salt, and then this part of superheated steam is mixed with high-pass outlet steam to maintain the temperature of the main steam (high-pressure cylinder inlet steam) at a constant temperature (566 ° C), and then pass into high-pressure Expansion in the cylinder (HP) does work for the generator. The exhaust steam from the high-pressure cylinder of the steam turbine needs to be introduced into the boiler for reheating, and the exhaust steam will pass through the low-temperature reheater (low reheater) and the high-temperature reheater (high reheater) inside the boiler in sequence. The high re-exit steam temperature will be reduced due to the coal-saving mode. The reheated steam is introduced into another solar heater to exchange heat with molten salt, and the temperature of the reheated steam (steam entering the medium-pressure cylinder) remains constant (566°C), and then it is passed into the medium-pressure cylinder (IP) to expand to work for the generator , this part of the reheated steam entering the medium-pressure cylinder continues to work for the generator according to the steam-water system flow of the coal-fired power station, and flows through the low-pressure cylinder (LP), the series-connected low-pressure heaters 5, 6, 7, 8, and the deaerator 4 And the high pressure heaters 1,2,3 connected in series to complete the whole cycle.

Further, the heating device of the coal-fired power station includes low-pass, partition screen, rear screen and high-pass equipment, low-regeneration and high-regeneration equipment, and a deaerator.

Further, the solar heater includes a heliostat, a tower receiver and a plurality of high-temperature molten salt tank heat exchangers.

Further, the number of the high-temperature molten salt tank heat exchangers is two, one is used to heat the saturated steam to a superheated steam state, and mix it with the superheated steam higher than the outlet to maintain the high-pressure cylinder inlet steam temperature constant. The other is used to heat the reheat steam below the rated temperature at the high re-exit to the rated temperature.

Furthermore, the high-temperature molten salt tank heat exchanger used for heating and reheating steam is also equipped with a flue baffle device as an auxiliary means to avoid the failure of the baffle method. The traditional flue baffle method uses the divided flue baffle method to regulate the reheat steam temperature. The advantages are simple structure and convenient operation. It has been adopted by many large power plant boilers. But the disadvantage is that the time lag of the steam temperature adjustment is too large, the opening of the baffle and the change of the steam temperature are in a nonlinear relationship, and the effective range of the opening is narrow. The flue gas baffle has good regulating performance when the opening degree is 40%-60%, and the flue gas ratio is 30%-70% and has good steam temperature regulating performance. However, if the flue gas share is lower than 25% or higher than 75%, the baffle will not be able to regulate, and the means for adjusting the steam temperature of the reheater will be invalid, and the rated steam temperature of the reheater can no longer be guaranteed.

The beneficial effects of the present invention are: compared with the previous scheme of using solar energy to heat feed water/condensate water, the present invention uses solar energy to heat high-temperature steam, and since there is no change in the amount of regenerative steam extraction, it will not affect the steam flow in the entire steam turbine flow, Pressure, temperature and amount of work done. In order to ensure the safe operation of the unit, there is no need to calculate and check the regenerative steam extraction at all levels. In addition, the present invention uses a supercritical once-through boiler, without a steam drum, and has a small heat storage capacity. Therefore, under the same degree of interference, the change of steam temperature will be more obvious than that of a steam drum boiler, and the present invention can well control the main steam and reheat steam temperature.

Description of drawings

Fig. 1 is a schematic flow chart of the solar thermal part of the coal-saving high-temperature tower solar thermal complementary coal-fired power plant integrated system of the present invention.

Fig. 2 is a schematic flow diagram of part of the coal-fired power station of the coal-saving high-temperature tower-type solar thermal complementary coal-fired power station integration system of the present invention.

In the figure: 1-level one high pressure heater; 2-two level high pressure heater; 3-three level high pressure heater; 4-deaerator; 5-level one low pressure heater; 6-two level low pressure heater; 7 -Three-stage low-pressure heater; 8-four-stage low-pressure heater; HP is the high-pressure cylinder of the steam turbine; IP is the medium-pressure cylinder of the steam turbine; LP is the low-pressure cylinder of the steam turbine; G is the generator.

detailed description

Based on the traditional solar thermal complementary coal-fired power station system, the present invention proposes a system integration solution with better performance by changing the system flow. The present invention will be further described with the accompanying drawings and specific implementation methods below. The coal-fired unit selects a 660MW supercritical thermal power unit as a reference system.

The system flow chart is shown in Figure 1 and Figure 2: the feed water at the outlet of the primary high-pressure heater (1) is introduced into the boiler and heated to a saturated steam state by the heating surfaces such as the economizer and the water wall, and then divided into two parts. Part of the saturated steam flows through the lower pass, the partition screen, the rear screen and the higher pass in sequence according to the original layout of the heating surface of the coal-fired power station. Another part of saturated steam is introduced into #1 solar heater to exchange heat with high-temperature molten salt, and then this part of superheated steam is mixed with high-pass outlet steam to maintain the main steam temperature (566°C) and then pass into the high-pressure cylinder (HP) Expansion works. The exhaust steam from the high-pressure cylinder of the steam turbine is introduced into the boiler for reheating, and the exhaust steam from the high-pressure cylinder will pass through the low pass and high reheat inside the boiler in turn. The reheated steam higher than the outlet is introduced into #2 solar heater to exchange heat with high-temperature molten salt, and the temperature of the reheated steam is heated to 566°C, and then it is passed into the intermediate pressure cylinder (IP) to expand to work for the generator, and then enters the medium pressure cylinder This part of the reheated steam continues to work for the generator according to the steam-water system flow of the coal-fired power station, and flows through the low-pressure cylinder (LP), the series-connected low-pressure heaters 5, 6, 7, 8, the deaerator 4 and the series-connected high-pressure heating Devices 1, 2, 3, thus completing the entire cycle. The thermal parameters (temperature, pressure, flow, etc.) of the reheated steam heated by solar energy are exactly the same as those of the original coal-fired power plant system, so the reheated steam heated by solar energy does not affect the subsequent thermodynamic cycle. It can be seen from the above that the introduction of solar energy reduces the coal feed of coal-fired power plants, and the heat transferred from boilers to steam (water) is reduced, so that superheated steam and reheated steam cannot reach the rated temperature, which affects the safe operation of coal-fired units. The invention utilizes solar energy to heat superheated steam and reheated steam to the rated temperature, which makes up for the influence of insufficient steam heat absorption caused by reducing the amount of coal fed.

In the tower solar heat collection system, the low temperature molten salt is introduced into the tower solar receiver through the molten salt pump to receive solar heat, and the high temperature molten salt heated by solar energy is divided into two parts and flows into #1 solar heater and #2 solar heater respectively The device heats superheated steam and reheated steam. After heat exchange, the two parts of low-temperature molten salt are collected and flow into the molten salt pump again to form a cycle. In the tower solar collector system, the process of heating the reheated steam with the #2 solar heater is used as the main means to control the temperature of the reheated steam, and the flue baffle method is used as an auxiliary adjustment method, avoiding the traditional division of the flue baffle method When adjusting the reheat steam temperature, when the flue gas share is lower than 25% or higher than 75%, the baffle method regulation fails.

Below in conjunction with calculation example, the present invention is further described.

System initial conditions: The present invention takes a 660MW supercritical thermal power unit as a reference system, and the main parameters of the unit are shown in Table 1. In order to accurately measure the impact of the introduction of solar energy on the coal saving and performance of the unit under different working conditions, two parameters are defined:

In the formula, η _se is the photoelectric conversion efficiency; P _S is the solar energy output power (W); is the total solar radiation energy (kJ/h); P _Z is the complementary system output power (W); is the total heat load of the boiler (kJ/h); η _ref is the efficiency of the original coal-fired power plant of the reference system; b is the coal consumption for power supply (g/kWh); m _sc is the coal consumption converted to standard coal (kg); E is the electrical energy output by the power plant (kWh).

Table 2 shows the main parameter changes of the system after extracting 11% steam flow; Table 3 shows the parameters of each design point in the new system; Table 4 shows the annual thermodynamic characteristics of the new system. In the design of solar mirror field scale, an optimal solar mirror field area should be considered. Because when the solar mirror field area increases, the new system can use more solar energy and thus save more coal. However, with the increase of solar energy input, the photoelectric conversion efficiency of solar energy does not increase all the time, but begins to decrease after reaching a certain value. The optimal design point parameters of the new system are shown in Table 5.

Table 1 The main parameters of the benchmark coal-fired power station

Table 2 Changes of main parameters of the system after extracting 11% steam flow

Table 3 Parameters of each design point in the new system

Table 4 Annual thermal characteristics of the new system

Table 5 Optimum design point parameters of the new system

As shown in Table 3 and Table 4, compared with the original system, the complementary system can reduce coal consumption by 7.7g/kWh, increase the efficiency of the whole plant by 1.07%, the maximum instantaneous photoelectric conversion efficiency can reach 23.16%, and the annual photoelectric conversion efficiency is 15.36%. And under the optimal design point, as shown in Table 5, the annual photoelectric conversion efficiency increases to 16.97%. For the existing single solar thermal power generation technology, the coal-saving high-temperature tower-type solar thermal complementary coal-fired power plant integrated system of the present invention is more cost-effective, so it has certain economic advantages.

The present invention has been described in detail above, obviously, as long as it does not substantially deviate from the invention point and effect of the present invention and is obvious to those skilled in the art, it is also included in the protection scope of the present invention.

Claims (5)

1. a kind of coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system, it is characterised in that the system includes：It is many The high-pressure heater of individual series connection, the low-pressure heater of multiple series connection, the boiler with economizer and water-cooling wall, steam-water separation Device, coal fired power plant heating device, solar heater, and steam turbine high-pressure cylinder, Steam Turbine Through IP Admission, turbine low pressure cylinder and Generator；

Wherein, the annexation of all parts and technological process are as follows in system：The feedwater out of one-level high-pressure heater is drawn Enter and be heated to saturated-vapor state through economizer and water wall surface in boiler, by saturated vapor point in steam-water separator It is two parts；A part of saturated vapor flows through low temperature superheater, segmentation successively according to original coal fired power plant heating surface arrangement Screen superheater, Late reworking and high temperature superheater；Another part saturated vapor is introduced into solar heater and high temperature melting Salt exchanges heat, and then mixes this part superheated steam with outlet vapor is exceeded, and maintains high pressure cylinder throttle (steam) temperature constant, is subsequently passed Generator acting is expanded in high pressure cylinder；Steam turbine high-pressure cylinder steam discharge is introduced to carry out reheating in boiler, and steam discharge will be passed sequentially through Boiler internal low-temperature reheater and high temperature reheater；Reheated steam is introduced into another solar heater and fused salt heat exchanging, is maintained Intermediate pressure cylinder throttle (steam) temperature is constant, is subsequently passed in intermediate pressure cylinder and is expanded to generator acting acting；Into the reheated steam of intermediate pressure cylinder Generator acting acting is continued as according to coal fired power plant boiler circuit flow, low pressure (LP) cylinder is flowed through successively, the low-pressure heater of series connection, Oxygen-eliminating device and the high-pressure heater of series connection are so as to complete whole circulation.

2. coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system according to claim 1, its feature exists Include low mistake, panel superheater in, the coal fired power plant heating device, shield afterwards and exceed equipment, and it is low again with equipment, deoxygenation again high Device.

3. coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system according to claim 1, its feature exists In the solar heater includes heliostat, tower receiver and multiple high-temperature molten salt slot type heat exchangers.

4. coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system according to claim 3, its feature exists In, the number of the high-temperature molten salt slot type heat exchanger is 2, and one is used to for saturated vapor to be heated to superheated steam state, and Mix with the superheated steam for exceeding outlet to maintain high pressure cylinder throttle (steam) temperature constant, another is used to export height less than specified again The reheated steam of temperature is heated to rated temperature.

5. coal-saving high temperature tower-type solar thermal complementation coal fired power plant integrated system according to claim 4, its feature exists In：High-temperature molten salt slot type heat exchanger for heating reheated steam also carries retaining board device of flue as supplementary means.