JP7351793B2 - Coal-fired power generation system - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Japan Society of Energy and Resources, 36th Energy Systems, Economics, and Environment Conference Lecture Proceedings, January 20, 2020 [Publications] 36th Energy Systems, Economics, and Environment Conference Economic and Environmental Conference, January 28, 2020

The present invention relates to a coal-fired power generation system that can operate at minimum load without using fossil fuels.

Coal exists in a wide area of the world, has large recoverable reserves, and has stable prices, so it has a highly stable supply and a low price per calorific value. Against this background, coal-fired power generation facilities that use coal as fuel have become widely popular as power generation facilities that can stably meet the demand for electricity (for example, Patent Document 1).

On the other hand, recently, as one of the measures against global warming, reducing carbon dioxide generated from power plants and the like is being considered. Against this background, renewable energy power generation equipment that uses renewable energy without using coal or natural gas that emit carbon dioxide is being introduced (for example, Patent Document 2).

In order to operate the power system stably, in addition to adjusting the demand and supply of power to keep the frequency constant, it is necessary to maintain inertia to suppress sudden fluctuations in frequency, and to adjust the voltage of the power transmission and distribution grid. It is necessary to supply reactive power required for adjustment. At present, the role of stable operation of these power systems is played by thermal power generation.In addition to continuing to generate electricity and adjusting power supply and demand by increasing or decreasing output, thermal power generation also has It is required to maintain the inertial force that the power system has within the power system, and to supply reactive power to the power system using a generator.

On the other hand, during times when the output of renewable energy is high, thermal power generation is stopped in order of fuel cost, in order to maintain a balance between electricity demand and supply. Because coal-fired power plants have low fuel costs, they continue to generate electricity for a longer period of time than other thermal power plants, even during times when renewable energy output is high. Therefore, as the last bastion of electricity supply and demand adjustment, coal-fired power generation is required to generate electricity at a lower output and contribute to stabilizing the power system.

Coal-fired power generation equipment uses pulverized coal, which is obtained by crushing coal in a mill, as fuel to obtain high-temperature, high-pressure steam, which operates a steam turbine and drives a generator. During periods when the output of renewable energy is high, coal-fired power generation equipment can quickly follow fluctuations in electricity demand with low power generation output, so the mill uses minimal power to obtain pulverized coal, and the boiler uses minimal power to obtain pulverized coal. generates steam. In other words, in order to stabilize the power system, coal-fired power generation equipment continues to operate at a minimum load to maintain output, increasing or decreasing output, maintaining the inertial force necessary for the power system, and Currently, they are supplying electricity, etc.

Since the output of renewable energy power generation equipment varies greatly depending on the natural environment, it is inevitable that surplus power will be generated depending on the time of day. The current situation is that large-capacity, inexpensive power storage is required to effectively utilize surplus power.

Japanese Patent Application Publication No. 2013-174182 JP2016-226238A

The present invention was made in view of the above situation, and enables minimum load operation to stabilize the power system while suppressing the use of coal (while maintaining environmental conditions without emitting carbon dioxide). The purpose is to provide a coal-fired power generation system that can be maintained.

In particular, by applying existing coal-fired power generation facilities, the use of coal can be suppressed (while environmental conditions are protected without emitting carbon dioxide), and at the same time, the minimum load can be achieved to stabilize the power system. An object of the present invention is to provide a coal-fired power generation system that can maintain minimum load operation while further reducing the power consumption.

A coal-fired power generation system of the present invention according to claim 1 for achieving the above object includes: a coal-fired power generation system that is connected to an electric power system and obtains electric power by driving a steam turbine; Renewable energy power generation equipment that obtains electricity from energy, and a minimum load that is operated using surplus electricity from the electricity obtained by the renewable energy power generation equipment and that maintains the minimum load operation of the coal-fired power generation equipment. It is characterized by comprising an operation maintenance means.

In the present invention according to claim 1, the minimum load operation maintaining means maintains the minimum load operation of the coal-fired power generation equipment using surplus electricity obtained from the renewable energy power generation equipment, so that coal is not used and the current state is maintained. It is possible to perform minimum load operation (maintaining inertia force to stabilize the system, supplying reactive power, etc.) in coal-fired power generation equipment.

Because it does not use means of pulverizing coal as fuel (because it is powered by surplus electricity), there is no need to use a mill to pulverize coal, for example, to maintain minimum load operation, and The resulting medium- and low-pressure steam enables output values at extremely low loads (the output value at the lowest load can be lowered).

This makes it possible to maintain minimum load operation to stabilize the power grid without emitting carbon dioxide and maintaining environmental conditions.

In particular, by applying existing coal-fired power generation equipment, it is possible to reduce carbon dioxide emissions, protect environmental conditions, and further reduce the minimum load to stabilize the power system (coal-fired power generation equipment). (Since it is not used, the minimum load can be lowered), making it possible to maintain the minimum load operation.

The coal-fired power generation system of the present invention according to claim 2 is the coal-fired power generation system according to claim 1, wherein the coal-fired power generation equipment is a boiler that generates steam by being charged with coal and ignited. The minimum load operation maintaining means is an electric burner that ignites the coal.

In the present invention according to claim 2, by igniting coal prepared as fuel with an electric burner, steam is generated in the boiler, and the generated steam can maintain minimum load operation, so that normal operation can be resumed. to enable the transition of Also, there is no need for a burner that uses carbon-based fuel to ignite the coal.

Further, in the coal-fired power generation system of the present invention according to claim 3, in the coal-fired power generation system according to claim 2, the boiler has a device through which fluid flows, and the minimum load operation maintenance means is the It is characterized by being an electric heater that heats the fluid flowing through the device.

In the present invention according to claim 3, a minimum amount of steam is generated by heating the fluid flowing through the device using an electric heater, and the minimum load operation can be maintained by the generated steam.

Further, the coal-fired power generation system of the present invention according to claim 4 is the coal-fired power generation system according to claim 2 or 3, wherein the coal-fired power generation equipment has a mill for crushing coal, and the The load operation maintaining means is characterized in that it is an air heater that heats the primary air that conveys the pulverized coal pulverized by the mill to the boiler.

In the present invention according to claim 4, the primary air conveying the pulverized coal pulverized in the mill can be heated by an air heater, and the pulverized coal can be preheated to help ignite the pulverized coal conveyed to the boiler. can.

Further, the coal-fired power generation system of the present invention according to claim 5 is the coal-fired power generation system according to any one of claims 2 to 4, in which the coal-fired power generation equipment includes exhaust steam of the steam turbine. has a condensing means for obtaining condensed water by being cooled, and a water supply route for supplying the condensed water obtained by the condensation means to the boiler, and the minimum load operation maintaining means circulates through the water supply route. It is characterized by being a water supply heater that heats supply water.

In the present invention according to claim 5, the feed water for generating steam can be heated by the feed water heater, thereby helping to generate steam.

Further, the coal-fired power generation system of the present invention according to claim 6 is the coal-fired power generation system according to any one of claims 2 to 4, wherein the coal-fired power generation equipment is configured to generate exhaust gas from the boiler. It has an exhaust system for discharging the exhaust gas, and a flue gas treatment means for purifying exhaust gas flowing through the exhaust system, and the minimum load operation maintaining means heats the flue gas treatment means to maintain an active state. It is characterized by being an active heater.

In the present invention according to claim 6, since the active heater can maintain the activated state of the exhaust gas treatment means, there is no need to use exhaust gas to warm up the exhaust gas treatment means, and the equipment can be operated by the circulation of exhaust gas. Damage can be suppressed.

The coal-fired power generation system of the present invention can maintain minimum load operation to stabilize the power system without emitting carbon dioxide and while environmental conditions are protected.

In particular, by applying existing coal-fired power generation equipment, it is possible to reduce the minimum load without emitting carbon dioxide, while protecting the environmental conditions, and further reducing the minimum load to stabilize the power system. It becomes possible to maintain driving.

1 is a schematic diagram of a coal-fired power generation system according to an embodiment of the present invention. It is a schematic system diagram explaining an example of a once-through boiler. It is a schematic system diagram explaining an example of a drum type boiler. It is a schematic system diagram of a water supply route.

FIG. 1 shows a schematic system for explaining the overall configuration of a coal-fired power generation system according to an embodiment of the present invention.

Connected to the power system 1 is a coal-fired power generation facility 4 in which a generator 3 is operated by the drive of a steam turbine 2 to obtain electric power. The coal-fired power generation facility 4 includes a boiler 6 in which coal (pulverized coal) is introduced into a combustion chamber 5 to generate steam.

The coal-fired power generation facility 4 includes a mill facility 7 that crushes coal to obtain pulverized coal that is used as fuel for the boiler 6 . In the mill equipment 7, coal is pulverized by a plurality of (required number of) mills to obtain the required amount of pulverized coal. Primary air for conveying pulverized coal is supplied to the mill equipment 7 from a primary air passage 8, and pulverized coal is supplied to the burner 9 of the combustion chamber 5 by the primary air.

Note that the reference numeral 10 in the figure is a damper that adjusts the amount of primary air sent from the primary air path 8 to the mill equipment 7.

High-temperature, high-pressure steam generated in the boiler 6 is sent to the steam turbine 2 through the steam introduction path 11 and expanded (the steam turbine 2 is driven), and the generator 3 is operated. In addition, the reference numeral 12 in the figure is an adjustment valve for adjusting the amount of steam sent from the steam introduction path 11 to the steam turbine 2.

Exhaust steam that has completed its work in the steam turbine 2 is condensed and condensed in a condenser 13, and is supplied to the boiler 6 equipment (low-temperature side heat exchanger) through a water supply path 15 by driving a water supply pump 14. .

Exhaust gas from the boiler 6 is released from an exhaust system 16. The exhaust system 16 is equipped with a denitrification device 17 and a desulfurization device 18 as exhaust gas processing means for purifying exhaust gas. Further, the exhaust system 16 is equipped with an electrostatic precipitator 19. In addition, the reference numeral 20 in the figure is a heat exchange means for exchanging heat (warming the primary air) with the primary air, which will be described later.

More specifically, as will be described later, the coal-fired power generation equipment 4 has a minimum load that maintains the minimum load operation of the coal-fired power generation equipment 4 (maintenance of inertia for system stability, operation of supplying reactive power, etc.). A means of operation and maintenance is provided. On the other hand, the power system 1 is connected to a renewable energy power generation facility 21 that obtains electric power from renewable energy (wind power, sunlight, etc.). The minimum load operation maintenance means is operated by surplus power obtained from the renewable energy power generation equipment 21 and supplied to the power system 1 .

Mill equipment that grinds coal into fine powder because it is not necessary to burn coal to obtain the minimum amount of steam (heat) when performing minimum load operation to stabilize the system of coal-fired power generation equipment 4. There is no need to use 7.

In order to obtain the minimum amount of steam (heat) by obtaining pulverized coal using mill equipment 7, it is necessary to operate a minimum number of mills, and an output value of a certain load is required, and there is a limit to reducing the minimum load. . By operating the minimum load operation maintenance means using surplus electricity without using coal, it is possible to suppress the operation of the mill in mill equipment 7, and the medium-pressure/low-pressure steam (heat) obtained from electricity allows extremely low It can be the output value of the load (the output value of the lowest load can be lowered).

For this reason, the minimum load operation of the coal-fired power generation facility 4 is carried out to stabilize the power system while the use of coal is suppressed (eliminated) (while environmental conditions are protected without emitting carbon dioxide). It becomes possible to maintain.

The minimum load operation maintaining means operated by surplus power out of the power supplied to the power system 1 will be specifically explained.

The combustion chamber 5 of the boiler 6 is equipped with an electric burner 23 for igniting pulverized coal obtained in advance. By igniting pulverized coal prepared as fuel by the electric burner 23, steam is generated in the boiler 6, and the generated steam enables transition from the lowest load operation state to normal operation. Further, a burner using carbon-based fuel such as natural gas is not required to ignite the pulverized coal.

Further, as will be specifically described later, the boiler 6 is equipped with a heat exchanger through which feed water flows, and is equipped with an electric heater 24 that heats the feed water flowing through the heat exchanger as a means for maintaining minimum load operation. There is. The electric heater 24 heats the feed water flowing through the heat exchanger to generate a minimum amount of steam, which allows minimum load operation to be maintained.

Furthermore, an air heater 25 is provided on the upstream side of the damper 10 in the primary air path 8 . The primary air carrying the pulverized coal can be heated by an air heater 25. Thereby, the pulverized coal is preheated, and the ignition of the pulverized coal can be assisted when the pulverized coal is ignited by the electric burner 23 or when the pulverized coal is ignited by the burner 9 after shifting to normal operation.

Further, although specifically described later, water supply heaters 26 for heating the water supply are provided on the upstream and downstream sides of the water supply route 15 with the water supply pump 14 in between. Feed water for generating steam in the boiler 6 can be heated by the feed water heater 26, which can help generate steam.

Further, the denitrification device 17 and the desulfurization device 18 provided in the exhaust system 16 are equipped with an active heater 27. Since the active heater 27 can maintain the catalysts of the denitrification device 17 and desulfurization device 18 at the activation temperature, it is necessary to perform warm-up operation (activation operation) of the denitrification device 17 and desulfurization device 18 using exhaust gas containing impurities. Therefore, damage to equipment due to the flow of impurities in the exhaust gas can be suppressed.

A specific example of the boiler 6 equipped with the electric heater 24 will be described based on FIGS. 2 and 3. FIG. 2 shows a schematic system for explaining an example of a once-through boiler, and FIG. 3 shows a schematic system for explaining an example of a drum-type boiler.

As shown in FIG. 2, the once-through boiler 6 includes a furnace wall tube economizer (low-temperature side heat exchanger) 31 to which feed water is sent by a feed water pump 14, and a furnace wall tube economizer 31 that supplies water heated by the furnace wall tube economizer 31. The system is equipped with a superheater 32 to which water is sent to superheat the feed water. Steam superheated by the superheater 32 is sent to the steam turbine 2.

A reflux path 33 branched from the downstream side of the furnace wall tube economizer 31 is equipped with a brackish water separator 34, and the liquid separated by the brackish water separator 34 is sent to the furnace wall tube economizer 31 by a circulation pump 35. . By controlling the fluid flowing into the brackish water separator 34, the evaporation point in the superheated region can be made variable.

The brackish water separator 34 is equipped with the electric heater 24 described above, and the liquid separated from the brackish water is heated by the electric heater 24.

As shown in FIG. 3, the drum-type boiler 6 includes a furnace wall tube economizer (low-temperature side heat exchanger) 41 to which feed water is sent by a feed water pump 14, and a furnace wall tube economizer 41 that supplies water heated by the furnace wall tube economizer 41. It is equipped with an evaporator 42 for heating. A steam drum 43 is provided to which the fluid evaporated by the evaporator 42 is sent, and a superheater 44 is provided to which the vapor separated by the steam drum 43 is sent and superheated.

Steam superheated by the superheater 44 is sent to the steam turbine 2. The fluid in the steam drum 43 is sent to the evaporator 42 by a circulation pump 45. In the drum-type boiler 6, the superheating area is fixed.

The steam drum 43 is equipped with the electric heater 24 described above, and the fluid sent to the evaporator 42 is heated by the electric heater 24.

A specific example of the water supply path 15 provided with the water supply heater 26 will be described based on FIG. 4 . FIG. 4 shows a schematic diagram of the water supply route.

As shown in FIG. 4, condensate from the condenser 13 is sent to a low-pressure feed water heater 52 by an upstream feed water pump 51, heated, and then degassed by a deaerator 53. The deaerated feed water is sent to the high pressure feed water heater 54 by the feed water pump 14, heated, and then sent to the boiler 6.

The low-pressure feed water heater 52 and the high-pressure feed water heater 54 are equipped with the above-described feed water heater 26, and the feed water heater 26 heats the feed water sent to the boiler 6.

In the above-mentioned coal-fired power generation equipment 4, the minimum load operation maintenance means that maintains the minimum load operation of the coal-fired power generation equipment 4 is operated by the surplus electricity obtained from the renewable energy power generation equipment 21. be done. That is, the electric burner 23, the electric heater 24, the air heater 25, and the water heater 26 are operated by the surplus power of the renewable energy power generation equipment 21.

Therefore, it is possible to obtain the minimum amount of steam (heat) using surplus electricity (surplus electricity from the renewable energy power generation equipment 21) out of the electricity supplied to the power system 1 without using coal. The low-pressure steam (heat) obtained by electric power without using coal makes it possible to maintain the minimum load operation of the coal-fired power generation facility 4 with a low load output value.

Therefore, by applying existing coal-fired power generation equipment, we can suppress (eliminate) the use of coal, do not emit carbon dioxide, protect environmental conditions, and at the minimum to stabilize the power system. It becomes possible to maintain the minimum load operation of the coal-fired power generation facility 4 while the load is further reduced.

INDUSTRIAL APPLICABILITY The present invention can be used in the industrial field of coal-fired power generation systems that can operate at minimum load without using fossil fuels.

1 Power system 2 Steam turbine 3 Generator 4 Coal-fired power generation equipment 5 Combustion chamber 6 Boiler 7 Mill equipment 8 Primary air passage 9 Burner 10 Damper 11 Steam introduction passage 12 Regulating valve 13 Condenser 14 Water supply pump 15 Water supply route 16 Exhaust system 17 Denitrification device 18 Desulfurization device 19 Electrostatic precipitator 20 Heat exchange means 21 Renewable energy power generation equipment 23 Electric burner 24 Electric heater 25 Air heater 26 Feed water heater 31, 41 Furnace wall tube economizer 32, 44 Superheater 33 Reflux path 34 Brackish water Separator 35, 45 Circulation pump 42 Evaporator 43 Steam drum 51 Upstream feed water pump 52 Low pressure feed water heater 53 Deaerator 54 High pressure feed water heater

Claims (6)

Coal-fired power generation equipment that is connected to the power grid and obtains electricity by driving a steam turbine;
Renewable energy power generation equipment that is connected to the power system and obtains power from renewable energy;
It is characterized by comprising a minimum load operation maintenance means that is operated by surplus electricity out of the electricity obtained by the renewable energy power generation equipment and maintains a minimum load operation of the coal-fired power generation equipment. Coal-fired power generation system. The coal-fired power generation system according to claim 1,
The coal-fired power generation equipment is
It has a boiler that generates steam by charging coal and igniting it,
The minimum load operation maintenance means is
A coal-fired power generation system characterized by being an electric burner that ignites the coal. The coal-fired power generation system according to claim 2,
The boiler has equipment through which fluid flows,
The minimum load operation maintenance means is
A coal-fired power generation system characterized by being an electric heater that heats fluid flowing through the equipment. In the coal-fired power generation system according to claim 2 or 3,
The coal-fired power generation equipment is
It has a mill that grinds coal;
The minimum load operation maintenance means is
A coal-fired power generation system characterized by being an air heater that heats primary air that conveys pulverized coal pulverized by the mill to the boiler. The coal-fired power generation system according to any one of claims 2 to 4,
The coal-fired power generation equipment is
condensing means for obtaining condensed water by cooling the exhaust steam of the steam turbine;
and a water supply path for supplying condensed water obtained by the condensing means to the boiler,
The minimum load operation maintenance means is
A coal-fired power generation system characterized by being a water supply heater that heats the water supply flowing through the water supply route. The coal-fired power generation system according to any one of claims 2 to 4,
The coal-fired power generation equipment is
an exhaust system that discharges exhaust gas from the boiler;
and an exhaust gas treatment means for purifying exhaust gas flowing through the exhaust system,
The minimum load operation maintenance means is
A coal-fired power generation system, characterized in that the system is an active heater that heats the flue gas treatment means and maintains the activated state.

Images