Boiler system

Abstract

To provide a boiler system capable of suppressing power consumption while adopting an electric boiler.SOLUTION: The boiler system 1 includes an electric boiler facility 2A composed of at least one electric boiler for generating vapor by using supplied electricity as a heating source, and a preheater 6 for pre-heating boiler feed water supplied to the electric boiler facility 6a by using a heat pump 2A.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a boiler system having an electric boiler. [Background technology]

[0002] Boiler systems that supply steam generated in a boiler to load equipment have been widely used in the past. In addition, in order to realize a carbon-free society in the future, it is expected that some of the fossil fuel boilers that have been the mainstream until now will be replaced by electric boilers that can use clean energy such as solar power generation.

[0003] A known electric boiler is one disclosed in Patent Document 1, for example. An electric boiler generates steam using supplied electricity as a heat source, and generally generates steam by heating boiler water with an electric heater. Because electric boilers use electricity as a heat source, they have the advantage of being able to reduce exhaust emissions and noise levels more easily than boilers that use fossil fuels as a heat source. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-292085 Summary of the Invention [Problem to be solved by the invention]

[0005] While electric boilers have the excellent features described above, they tend to consume relatively large amounts of power because they use electricity as a heat source. Therefore, when configuring a boiler system that uses an electric boiler, it is important to minimize power consumption. In view of the above-mentioned problems, the present invention aims to provide a boiler system that can minimize power consumption while using an electric boiler. [Means for solving the problem]

[0006] The boiler system according to the present invention includes an electric boiler facility consisting of at least one electric boiler that generates steam using supplied electricity as a heat source, and a preheating device that preheats boiler feedwater supplied to the electric boiler facility using a heat pump. This configuration makes it possible to reduce power consumption while employing an electric boiler.

[0007] More specifically, the above configuration may include a mixing boiler facility including the electric boiler facility and a fossil fuel boiler facility consisting of at least one fossil fuel boiler that generates steam using supplied fossil fuel as a heat source, and a control unit that controls steam generation in the mixing boiler facility, and the steam generated by the mixing boiler facility may be supplied to a load facility.

[0008] More specifically, the control unit may be configured to perform demand increase response control by prioritizing steam generation by the electric boiler equipment over that by the fossil fuel boiler equipment in order to meet requests for increased power demand in the boiler system, and demand decrease response control by prioritizing steam generation by the fossil fuel boiler equipment over that by the electric boiler equipment in order to meet requests for decreased power demand.

[0009] More specifically, the control unit may be configured to increase the intensity of the preheating when performing the demand increase response control and decrease the intensity of the preheating when performing the demand decrease response control. Also, more specifically, the configuration may be configured to include a water supply tank for storing preheated boiler feedwater, and to supply water from the water supply tank to the electric boiler facility.

[0010] More specifically, the electric boiler facility may be configured to include a plurality of electric boilers, and the control unit may control the amount of steam generated by the electric boiler facility by changing the number of operating electric boilers. Also, more specifically, the electric boiler facility may be configured to supply steam generated by the mixing boiler facility to the load facility via a steam header, and the control unit may perform the demand increase control and the demand decrease control within a range in which a detected pressure value in the steam header satisfies a predetermined condition.

[0011] Furthermore, in a boiler system having the above-described configuration, which includes a mixing boiler facility including the electric boiler facility and a fossil fuel boiler facility consisting of at least one fossil fuel boiler that generates steam using supplied fossil fuel as a heat source, and a control unit that controls steam generation in the mixing boiler facility, and in which the steam generated by the mixing boiler facility is supplied to a load facility, the control unit may be configured to stop operation of the preheating device and all of the electric boiler facilities in response to a request for a reduction in power demand in the boiler system. [Effects of the Invention]

[0012] According to the boiler system of the present invention, it is possible to reduce the amount of power consumption even while employing an electric boiler. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a boiler system and its surroundings according to an embodiment of the present invention. [Figure 2] 1 is an explanatory diagram illustrating a configuration example of a heat pump according to an embodiment of the present invention. [Figure 3] 4 is a flowchart illustrating request response control according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0015] Fig. 1 is a schematic configuration diagram of a boiler system 1 according to this embodiment and its surroundings. As shown in the figure, the boiler system 1 includes an electric boiler facility 2A consisting of one or more electric boilers (three electric boilers A1 to A3, as an example in this embodiment), and a fossil fuel boiler facility 2B consisting of one or more fossil fuel boilers (three fossil fuel boilers B1 to B3, as an example in this embodiment). In the following description, the boiler facility including the electric boiler facility 2A and the fossil fuel boiler facility 2B may be referred to as a mixed boiler facility 2.

[0016] Furthermore, the boiler system 1 includes a steam pipe 3, a steam header 4, a steam pressure sensor 5, a preheating device 6, a feedwater tank 7, and a control device 8. The steam header 4 is connected to each boiler in the mixing boiler facility 2 via the steam pipe 3. The steam pressure sensor 5 detects the pressure value inside the steam header 4 (hereinafter also referred to as the "header pressure value"). The control device 8 controls the steam generation in the mixing boiler facility 2 and the preheating of the boiler feedwater in the preheating device 6.

[0017] Each of the electric boilers A1 to A3 is equipped with an electric heater or the like and generates steam using Joule heat generated by electricity from a commercial power source or the like. In this way, each of the electric boilers A1 to A3 generates steam using the supplied electricity as a heat source. Each of the electric boilers A1 to A3 is switched by the control device 8 between an operating state in which it operates to generate a predetermined amount of steam (for example, 500 kg / h), and a stopped state (standby state) in which it stops operating to generate steam.

[0018] This allows the control device 8 to control the amount of steam generated by the electric boiler facility 2A by changing the number of electric boilers A1 to A3 in operation. That is, when the amount of steam generated by the electric boiler facility 2A is to be reduced, the control device 8 reduces the number of electric boilers A1 to A3 in operation, and when the amount of steam generated by the electric boiler facility 2A is to be increased, the control device 8 increases the number of electric boilers A1 to A3 in operation.

[0019] Each of the fossil fuel boilers B1-B3 is equipped with a burner or the like and burns a fossil fuel (e.g., fuel derived from heavy oil, kerosene, or natural gas) to generate steam. In this way, each of the fossil fuel boilers B1-B3 generates steam using the supplied fossil fuel as a heat source. Furthermore, each of the fossil fuel boilers B1-B3 can be switched by the control device 8 between an operating state in which it operates to generate steam and a stopped state (standby state) in which it stops operating to generate steam. In the operating state, the amount of steam generated can be adjusted by controlling the amount of fossil fuel combustion. This allows the control device 8 to control the amount of steam generated by the fossil fuel boiler facility 2B by changing the number of operating fossil fuel boilers B1-B3 or the amount of fossil fuel combustion in any of the operating fossil fuel boilers B1-B3.

[0020] The steam generated by the mixing boiler equipment 2 is sent to a steam header 4 via a steam pipe 3. The steam header 4 collects the steam generated by the mixing boiler equipment 2 and supplies the steam to a load equipment 11 that uses the steam via a supply pipe 10. The steam pressure sensor 5 sends information on the detected header pressure value to a control device 8.

[0021] The preheating device 6 uses a heat pump 6a to preheat the boiler feedwater to be supplied to the electric boiler facility 2A. The feedwater tank 7 can store the preheated boiler feedwater. In this embodiment, the boiler feedwater preheated by the preheating device 6 is sent to the feedwater tank 7, and is supplied from the feedwater tank 7 to the electric boiler facility 2A. Note that the boiler feedwater for the fossil fuel boilers B1 to B3 may be supplied from the feedwater tank 7, or may be supplied from a different water source.

[0022] Fig. 2 shows a schematic configuration example of a heat pump 6a (air-source heat pump). As shown in this figure, the heat pump 6a shown in Fig. 2 includes a compressor 61, a condenser 62, an expansion valve 63, and an evaporator 64, which are connected by a refrigerant circulation line Lc. A refrigerant R can be circulated through the refrigerant circulation line Lc.

[0023] The compressor 61 has a motor as a drive source, and compresses the refrigerant R received from the upstream side to produce high-temperature, high-pressure refrigerant R, which it sends downstream. The rotation speed of the compressor 61 can be controlled by the control device 8. By increasing the rotation speed of the compressor 61, it is possible to increase the strength of preheating in the preheating device 6 (i.e., the heat storage temperature of the water tank 7), and by decreasing the rotation speed of the compressor 61, it is possible to decrease the strength of preheating in the preheating device 6. Note that increasing the rotation speed of the compressor 61 increases the power consumption of the heat pump 6a accordingly, and decreasing the rotation speed of the compressor 61 decreases the power consumption of the heat pump 6a accordingly.

[0024] Condenser 62 exchanges heat between refrigerant R sent from compressor 61 and boiler feedwater, condensing the refrigerant R. The boiler feedwater (preheated boiler feedwater) that has undergone heat exchange in condenser 62 is sent to feedwater tank 7. The heat exchange between refrigerant R and boiler feedwater in condenser 62 may be a once-through (once-through) system or a circulation system. In the case of a circulation system, condenser 62 and feedwater tank 7 are connected by a required circulation line, and boiler feedwater before preheating is supplied to feedwater tank 7.

[0025] The expansion valve 63 passes the refrigerant R sent from the condenser 62, thereby reducing the pressure and temperature of the refrigerant R. The evaporator 64 exchanges heat between heat source air Ar (outside air) and the refrigerant R sent from the expansion valve 13, and evaporates the refrigerant R by absorbing heat from the heat source air Ar. The evaporator 64 shown in FIG. 2 is configured as, for example, a fin-tube heat exchanger, and is capable of actively sending the heat source air Ar to a number of fins provided on the surface of a heat transfer tube (part of the refrigerant circulation line Lc) through which the refrigerant R passes, using a blower fan 64a.

[0026] When the heat pump 6a is driven, the refrigerant R circulates in the direction indicated by the solid arrow in Fig. 2. At this time, the refrigerant R absorbs heat from the heat source air Ar in the evaporator 64 and is vaporized, while the refrigerant R releases heat to the boiler feedwater and is condensed in the condenser 62. In this way, the boiler feedwater is preheated using the heat pump 6a.

[0027] A preheating device 6 having such a heat pump 6a makes it possible to preheat by effectively utilizing unused heat (heat from the air in the case of an air-source heat pump), thereby realizing energy savings and a reduction in carbon dioxide emissions. Note that the heat pump 6a is not limited to an air-source heat pump, and for example, a heat recovery heat pump that can recover heat from cooling water before heat dissipation in a cooling tower or from waste hot water discharged from production equipment may also be used.

[0028] The power demand adjustment device 12 receives an up / down DR activation command from an aggregator or the like, and provides support for controlling the mixing boiler equipment 2 and the preheating device 6 in order to adjust the power demand within a facility such as a factory in which the boiler system 1 is installed. The power demand adjustment device 12 may be included in the boiler system 1, but is not limited to this, and may be located within the same facility without being included in the boiler system 1, or may be located outside the facility.

[0029] Aggregators, etc., are businesses that integrate and control consumer-side energy resources and distributed energy resources and provide energy services through virtual power plants (VPPs) and demand response (DR), and include resource aggregators and aggregation coordinators. Resource aggregators are businesses that directly conclude VPP service contracts with consumers and control resources. Aggregation coordinators are businesses that aggregate the amount of electricity controlled by resource aggregators and trade electricity directly with general electricity transmission and distribution companies and retail electricity companies.

[0030] For example, at times such as peak power demand, i.e., when power supply falls below power demand, an aggregator or the like initiates a downward demand response (hereinafter also referred to as downward DR) to consumers, requesting a reduction in power demand. The downward DR initiation command is sent, for example, in the form of an email, and includes information specifying the start time and duration of the downward DR. Upon receiving the downward DR initiation command, the power demand adjustment device 12 transmits to the control device 8 a control signal (hereinafter also referred to as downward DR request signal) for performing downward DR in the boiler system 1. The downward DR request signal is a signal including information specifying the start time and end time of the downward DR based on the instructions of the downward DR initiation command.

[0031] Furthermore, for example, when excessive output from renewable energy sources occurs, i.e., when power supply exceeds power demand, an aggregator or the like initiates an upward demand response (hereinafter also referred to as "upward DR") to consumers, requesting an increase in power demand. The upward DR initiation command is sent, for example, in the form of an email, and includes information specifying the start time and duration of the upward DR. Upon receiving the upward DR initiation command, the power demand adjustment device 12 transmits to the control device 8 a control signal (hereinafter also referred to as "upward DR request signal") for performing upward DR in the boiler system 1. The upward DR request signal is a signal including information specifying the start time and end time of the upward DR based on the instructions of the upward DR initiation command.

[0032] The power demand adjustment device 12 may be configured to support peak shaving of power demand within the facility in addition to adjusting the power demand within the facility in response to a DR activation command. In a first example, the power demand adjustment device 12 monitors the amount of power usage within the facility during a demand time period (e.g., 30 to 60 minutes), and transmits a downward DR request signal to the control device 8 when the amount of power usage is predicted to exceed the contracted power amount with the electricity retailer. The request for downward DR is canceled when the amount of power usage within the demand time period falls below a reference power amount that is lower than the contracted power amount. In a second example, the power demand adjustment device 12 transmits a downward DR request signal to the control device 8 at the start time of a power saving implementation day that is set according to a power saving request period (e.g., a specified date and time in summer) from the electricity retailer. The request for downward DR is canceled at the end time of the power saving implementation day. In a third example, the power demand adjustment device 12 transmits a downward DR request signal to the control device 8 at the start time of a preset peak operating time period. The request for a downward DR will be lifted at the end of the peak operating period, which is set based on the factory's production plan, etc.

[0033] The control device 8 controls the mixing boiler facility 2 to generate steam during normal operation (when neither demand decrease response control nor demand increase response control, which will be described later, is being performed) so that the header pressure value detected by the steam pressure sensor 5 satisfies a predetermined condition α that has been set in advance. Note that the ratio of the amount of steam generated by the electric boiler facility 2A to the amount of steam generated by the fossil fuel boiler facility 2B during normal operation (the priority of steam generation between the two) can be set appropriately depending on the operating environment of the boiler system 1, etc. In this embodiment, as an example, the ratio is assumed to be approximately equal.

[0034] The above-mentioned predetermined condition α is a condition for supplying an appropriate amount of steam to the load equipment 11, and in the example of this embodiment, this condition is satisfied when the header pressure value is a pressure value corresponding to a preset target steam volume (or within a pressure range corresponding to the preset target steam volume). This makes it possible to supply an appropriate amount of steam from the mixing boiler equipment 2 to the load equipment 11 via the steam header 4. Note that the specific control method for the steam output by the control device 8 is not particularly limited, and for example, a method of PID control of the steam generation amount of the fossil fuel boiler equipment 2B may be adopted, while operating an appropriate number of electric boiler equipment 2A, so that the header pressure value converges to a pressure value corresponding to the target steam volume.

[0035] Furthermore, under normal circumstances, the control device 8 drives the heat pump 6a to preheat the boiler feedwater. This reduces the heating load of the boiler feedwater in the electric boiler equipment 2A, making it possible to reduce the amount of power consumed by the electric boiler equipment 2A. Note that, since the feedwater tank 7 is installed in this embodiment, even when the demand for boiler feedwater in the electric boiler equipment 2A is low, the preheated boiler feedwater can be stored in the feedwater tank 7 to prepare for an increase in demand.

[0036] On the other hand, when a request for a downward DR or an upward DR is made, the control device 8 executes a control operation (request response control) that can respond to the request. This request response control will be described in more detail with reference to the flowchart of FIG.

[0037] The control device 8 waits for reception of a downward DR request signal from the power demand adjusting device 12 (step S1) and for reception of an upward DR request signal (step S2).

[0038] When the control device 8 receives a downward DR request signal (Yes in step S1), it monitors the arrival of the start time of the downward DR, which is recognized based on this signal (step S3). When the start time of the downward DR arrives (Yes in step S3), the control device 8 executes demand reduction response control that prioritizes steam generation in the fossil fuel boiler facility 2B over the electric boiler facility 2A so as to respond to the request for the downward DR within a range in which the header pressure value satisfies a predetermined condition α (step S4).

[0039] More specifically, the control device 8 reduces the amount of steam generated by the electric boiler equipment 2A, thereby reducing the power consumption of the electric boiler equipment 2A and achieving the lower DR. At the same time, the control device 8 increases the amount of steam generated by the fossil fuel boiler equipment 2B by the amount of the decrease in the amount of steam generated by the electric boiler equipment 2A, thereby maintaining a state in which the header pressure value satisfies the above-mentioned condition α. ​​In this way, the boiler system 1 prioritizes steam generation by the fossil fuel boiler equipment 2B over the electric boiler equipment 2A (in other words, increases the proportion of steam generation by the fossil fuel boiler equipment 2B in the amount of steam generated by the mixing boiler 2), making it possible to achieve both the lower DR and an appropriate supply of steam to the load equipment 11.

[0040] Furthermore, when performing the demand reduction response control described above, the control device 8 may also reduce the strength of preheating of boiler feedwater by the heat pump 6a. This reduces the power consumption of the heat pump 6a, making it easier to achieve the lower DR. In particular, in a situation where it is difficult to reduce the number of operating electric boilers A1 to A3 from the current level, reducing the strength of preheating is a very effective measure for achieving the lower DR.

[0041] Furthermore, the control device 8 monitors the arrival of the end time of the current downward DR (step S5), and when the end time of the downward DR arrives (Yes in step S5), it ends the current demand reduction response control and resumes normal control operation (step S9), and repeats the operation of step S1.

[0042] On the other hand, when an upward DR request signal is received (Yes in step S2), the control device 8 monitors the arrival of the start time of the upward DR, which is recognized based on this signal (step S6). When the start time of the upward DR arrives (Yes in step S6), the control device 8 executes demand increase response control that prioritizes steam generation by the electric boiler facility 2A over the fossil fuel boiler facility 2B so as to respond to the request for the upward DR within a range in which the header pressure value satisfies the predetermined condition α (step S7).

[0043] More specifically, the control device 8 increases the amount of steam generated by the electric boiler equipment 2A, thereby increasing the power consumption of the electric boiler equipment 2A, and thereby achieving the upward DR. At the same time, the control device 8 reduces the amount of steam generated by the fossil fuel boiler equipment 2B by the amount of increase in the amount of steam generated by the electric boiler equipment 2A, thereby maintaining a state in which the header pressure value satisfies the above-mentioned condition α. ​​In this way, the boiler system 1 prioritizes steam generation by the electric boiler equipment 2A over that of the fossil fuel boiler equipment 2B (in other words, increases the proportion of steam generation by the electric boiler equipment 2A in the amount of steam generated by the mixing boiler 2), thereby enabling the achievement of the upward DR and an appropriate supply of steam to the load equipment 11 at the same time.

[0044] Furthermore, when performing the above-described demand increase response control, the control device 8 may increase the strength of preheating of the boiler feedwater by the heat pump 6a (the heat storage temperature of the feedwater tank 7). In this way, the power consumption of the heat pump 6a can be increased, making it easier to achieve the upward DR. In particular, under low-load conditions where it is difficult to increase the number of operating electric boilers A1 to A3 from the current level, increasing the strength of the preheating is a very effective measure to achieve the upward DR.

[0045] Furthermore, the control device 8 monitors the arrival of the end time of the current upward DR (step S8), and when the end time of the upward DR arrives (Yes in step S8), it ends the current demand increase response control and resumes normal control operation (step S9), and repeats the operation of step S1.

[0046] The operation of the request response control (steps S1 to S9) described above is intended to allow the boiler system 1 to function in a supply and demand balancing market, and is capable of appropriately responding to the activation of a demand response in the supply and demand balancing market. On the other hand, when the boiler system 1 is to function in a capacity market, the control operation of the control device 8 may be executed so as to allow the boiler system 1 to appropriately respond to the activation of a demand response in the capacity market.

[0047] More specifically, when the power demand adjustment device 12 receives a command to invoke a downward DR in the capacity market, it transmits a downward DR request signal to the control device 8. Upon receiving the downward DR request signal, the control device 8 stops all operations of the preheating device 6 and the electric boiler equipment 2A (in this embodiment, all operations of the electric boilers A1 to A3 are stopped) in response to the request for a downward DR (a request to reduce the power demand in the boiler system 1). At the same time, the control device 8 increases the amount of steam generated by the fossil fuel boiler equipment 2B to compensate for the decrease in the amount of steam generated due to the shutdown of all operations of the electric boiler equipment 2A. This enables the boiler system 1 to respond to the invocation of a downward DR in the capacity market as much as possible and continue to supply an appropriate amount of steam to the load equipment 11.

[0048] As described above, the boiler system 1 of this embodiment includes an electric boiler facility 2A consisting of at least one electric boiler that generates steam using supplied electricity as a heat source, and a preheating device 6 that uses a heat pump 6a to preheat boiler feedwater that is supplied to the electric boiler facility 2A. Therefore, according to the boiler system 1, by preheating the boiler feedwater using the heat pump 6a, it is possible to reduce the amount of power consumption required to generate steam in the electric boiler, making it possible to suppress power consumption even while employing an electric boiler.

[0049] Although the heat pump 6a also consumes electricity when it is operating, it can preheat the boiler feedwater with a relatively small amount of electricity because it uses unused heat as described above. Therefore, generating steam in the electric boiler equipment 2A using boiler feedwater preheated by the heat pump 6a can reduce power consumption compared to generating steam in the electric boiler equipment 2A using boiler feedwater that has not been preheated.

[0050] The boiler system 1 also includes a mixing boiler facility 2 including an electric boiler facility 2A and a fossil fuel boiler facility 2B, and a control device 8 that controls steam generation in the mixing boiler facility 2, and supplies the steam generated by the mixing boiler facility 2 to a load facility 11. The control device 8 also performs demand increase response control that prioritizes steam generation in the electric boiler facility 2A over the fossil fuel boiler facility 2B in order to respond to requests for increased power demand in the boiler system 1, and demand decrease response control that prioritizes steam generation in the fossil fuel boiler facility 2B over the electric boiler facility 2A in order to respond to requests for decreased power demand. Therefore, the boiler system 1 is able to appropriately respond to requests for increases and decreases in power demand.

[0051] <Contribution to the United Nations-led Sustainable Development Goals (SDGs)> The boiler system disclosed herein uses a heat pump and an electric boiler that heats water using electricity without using fossil fuels, which can contribute to achieving Goal 13 of the Sustainable Development Goals (SDGs), "Take urgent action to combat climate change," by promoting the reduction of carbon dioxide emissions. [Industrial Applicability]

[0052] The present invention can be used in a boiler system having an electric boiler. [Explanation of symbols]

[0053] 1. Boiler system 2. Mixing boiler equipment 2A electric boiler equipment 2B Fossil fuel boiler equipment 3 Steam piping 4 Steam header 5 Vapor pressure sensor 6 Preheating device 6a Heat pump 61 Compressor 62 Condenser 63 Expansion valve 64 Evaporator 64a Fan 7. Water tank 8 Control Device 10 Supply pipe 11 Load equipment 12 Power demand adjustment device A1~A3 Electric boiler B1~B3 Fossil fuel boilers Lc refrigerant circulation line R refrigerant

Claims

1. an electric boiler facility including at least one electric boiler that generates steam using supplied electricity as a heat source; a preheating device that preheats boiler feedwater supplied to the electric boiler facility using a heat pump.

2. a mixing boiler facility including the electric boiler facility and a fossil fuel boiler facility consisting of at least one fossil fuel boiler that generates steam using a supplied fossil fuel as a heat source; a control unit for controlling steam generation in the mixing boiler facility, 2. The boiler system according to claim 1, wherein the steam generated by the mixing boiler facility is supplied to a load facility, The control unit a demand increase response control that prioritizes steam generation by the electric boiler facility over steam generated by the fossil fuel boiler facility in order to respond to an increase in the demand for electric power in the boiler system; and a demand reduction response control that prioritizes steam generation by the fossil fuel boiler facility over steam generation by the electric boiler facility in order to respond to the request for a reduction in the power demand.

3. The control unit increasing the intensity of the preheating when performing the demand increase response control; The boiler system according to claim 2 , wherein the intensity of the preheating is reduced when the demand reduction response control is performed.

4. 4. The boiler system according to claim 3, further comprising a water supply tank for storing preheated boiler feed water, and water is supplied to the electric boiler facility from the water supply tank.

5. the electric boiler facility comprises a plurality of the electric boilers, The control unit 3. The boiler system according to claim 2, wherein the amount of steam generated by the electric boiler facility is controlled by changing the number of electric boilers in operation.

6. The steam generated by the mixing boiler facility is supplied to the load facility via a steam header, The control unit 6. The boiler system according to claim 2, wherein the demand increase response control and the demand decrease response control are performed within a range in which a detected value of the pressure in the steam header satisfies a predetermined condition.

7. a mixing boiler facility including the electric boiler facility and a fossil fuel boiler facility consisting of at least one fossil fuel boiler that generates steam using a supplied fossil fuel as a heat source; a control unit for controlling steam generation in the mixing boiler facility, 2. The boiler system according to claim 1, wherein the steam generated by the mixing boiler facility is supplied to a load facility, The control unit A boiler system that stops operation of the preheating device and all of the electric boiler equipment in response to a request for a decrease in power demand in the boiler system.

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