Boiler system

Abstract

This prevents the risk of biomass fuel igniting and also prevents the biomass fuel from becoming too moist, which can accelerate fermentation. [Solution] A boiler system 100 is provided, comprising: a mill 12 for crushing biomass fuel; a fuel storage tank 20 for storing biomass fuel; a transport unit 30 for transporting biomass fuel; a boiler 40 that generates steam by burning the biomass fuel crushed by the mill 12 in a combustion device 41; and an exhaust gas extraction unit 90 that branches off a portion of the exhaust gas G flowing through an exhaust gas passage L1 that guides the exhaust gas G discharged from the boiler 40 to a chimney 71 and guides it to at least one of the fuel storage tank 20 and the transport unit 35. The exhaust gas extraction unit 90 includes a cooler 92 that cools the exhaust gas G by heat exchange with a heat transfer medium that is not mixed with the exhaust gas G, and a dehumidifier 93 that removes some of the moisture from the exhaust gas G cooled by the cooler 92.

Description

Technical Field

[0001] The present disclosure relates to a boiler system.

Background Art

[0002] Conventionally, there has been known a boiler system that promotes the drying of fuel stored in a bunker by supplying a part of the exhaust gas discharged from a boiler to the bunker (see, for example, Patent Document 1). The boiler system disclosed in Patent Document 1 prevents the risk of ignition of the fuel by mixing air with a part of the exhaust gas to adjust the temperature of the exhaust gas, so that high-temperature exhaust gas is supplied to the bunker.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the boiler system of Patent Document 1, the risk of ignition of the fuel stored in the bunker due to high temperature is prevented by mixing air to adjust the temperature of the exhaust gas. However, by mixing air with the exhaust gas, the oxygen concentration of the exhaust gas increases. Therefore, the risk of ignition of the fuel due to the increase in the oxygen concentration increases.

[0005] In recent years, in thermal power plants, as a measure to suppress carbon dioxide emissions, the use of plant-derived woody biomass fuel as an alternative fuel to coal has been expanding. When the moisture content of biomass fuel is high moisture (for example, the moisture content exceeds 10%), fermentation is promoted, resulting in the release of carbon monoxide and heat generation.

[0006] In the boiler system described in Patent Document 1, when biomass fuel is used as fuel, the moisture contained in the biomass fuel remains as water vapor in the exhaust gas, and this moisture-containing exhaust gas is supplied to the bunker. As a result, the biomass fuel stored in the bunker may absorb moisture, leading to a high moisture content and potentially accelerating fermentation.

[0007] This disclosure is made in view of these circumstances and aims to provide a boiler system that can prevent the risk of biomass fuel ignition and prevent the biomass fuel from becoming too moist and fermentation from being accelerated. [Means for solving the problem]

[0008] To solve the above problems, the boiler system of this disclosure employs the following means. A boiler system according to one aspect of the present disclosure comprises: a grinding device for grinding biomass fuel; a fuel storage unit for storing the biomass fuel; a transport unit for transporting the biomass fuel; a boiler for generating steam by burning the biomass fuel ground by the grinding device in a combustion unit; and an exhaust gas extraction unit that branches off a portion of the exhaust gas flowing through an exhaust gas passage that guides the exhaust gas discharged from the boiler to the outside of the system and guides it to at least one of the fuel storage unit and the transport unit, wherein the exhaust gas extraction unit includes a cooling unit that cools the exhaust gas by heat exchange with a heat transfer medium that is not mixed with the exhaust gas, and a dehumidifying unit that removes a portion of the moisture from the exhaust gas cooled by the cooling unit. [Effects of the Invention]

[0009] According to this disclosure, the risk of biomass fuel ignition is prevented, as is the promotion of fermentation due to high moisture content in the biomass fuel. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing a boiler system according to one embodiment of the present disclosure. [Figure 2]This flowchart shows the operation of the exhaust gas extraction section of a boiler system according to one embodiment of the present disclosure. [Figure 3] This graph shows the relationship between the temperature of the exhaust gas that has passed through the cooling section and the position of the exhaust gas extraction passage. [Figure 4] This graph shows the relationship between the relative humidity of the exhaust gas that has passed through the dehumidification section and the position of the exhaust gas extraction passage. [Modes for carrying out the invention]

[0011] Hereinafter, the boiler system 100 of this embodiment will be described with reference to the drawings. Figure 1 is a schematic configuration diagram showing a boiler system 100 according to one embodiment of the present disclosure. As shown in Figure 1, the boiler system 100 of this embodiment includes a fuel supply equipment 10, a fuel storage tank (fuel storage section) 20, a transport section 30, a transport section 35, a boiler 40, a denitrification equipment 50, a dust collection equipment 60, a desulfurization equipment 70, a chimney 71, a steam turbine 80, a generator 81, a condenser 82, and an exhaust gas extraction section 90.

[0012] The fuel supply equipment 10 is equipment that crushes biomass fuel and supplies it to the boiler 40. The fuel supply equipment 10 has a bunker (fuel storage section) 11 and a mill (crushing device) 12. The bunker 11 is a device that temporarily stores the biomass fuel transported by the transport section 30 and also supplies the biomass fuel to the mill 12. The mill 12 is a device that crushes the biomass fuel and supplies the biomass fuel to the boiler 40 together with transport air.

[0013] Here, biomass fuel refers to, for example, biomass pellets (hereinafter also simply called pellets) made by compressing crushed biomass particles. The biomass raw materials used for biomass pellets are renewable, biologically derived organic resources, such as thinned wood, waste wood, driftwood, grass, agricultural and livestock waste, and sewage sludge. Because biomass pellets are molded into a specific shape during the manufacturing process, their size is more uniform than that of coal. For example, while coal before crushing is in the form of lumps ranging from 2 to 50 mm, pellets are cylindrical in shape with a diameter of about 6 to 8 mm and a length of about 40 mm, and are homogeneous.

[0014] The fuel storage tank 20 is a facility for storing biomass fuel that is transported by the transport unit 35.

[0015] The transport unit 30 is a device that transports biomass fuel from the fuel storage tank 20 to the bunker 11. The transport unit 30 is formed, for example, by covering a conveyor belt with a duct. The transport unit 35 is a device that transports biomass fuel loaded onto the fuel receiving equipment 1 to the fuel storage tank 20. The transport unit 35 is formed, for example, by covering a conveyor belt with a duct.

[0016] The boiler 40 is a device that generates steam by burning the biomass fuel crushed by the fuel supply equipment 10 in the combustion device 41. The boiler 40 generates superheated steam by exchanging heat with feedwater or steam using the heat generated by the combustion of the biomass fuel. The superheated steam generated in the boiler 40 is supplied to the steam turbine 80. The exhaust gas G generated by the combustion of the biomass fuel is guided out of the system through the chimney 71 via the exhaust gas flow path L1. The exhaust gas flow path L1 is a flow path that guides the exhaust gas G discharged from the boiler 40 to the chimney 71.

[0017] The denitrification equipment 50 supplies a reducing agent, such as ammonia or urea solution, which has the effect of reducing nitrogen oxides, to the exhaust gas G, thereby removing nitrogen oxides (NOx) contained in the exhaust gas G. The denitrification equipment 50 promotes the reaction between the nitrogen oxides contained in the exhaust gas to which the reducing agent is supplied and the reducing agent through the catalytic action of a denitrification catalyst installed inside the denitrification equipment 50.

[0018] The dust collection equipment 60 is a device for removing dust such as ash contained in the exhaust gas G. As the dust collection equipment 60, for example, a bag filter or an electrostatic precipitator can be used.

[0019] The desulfurization equipment 70 is a device for removing sulfur oxides contained in the exhaust gas G. As the desulfurization equipment 70, for example, a wet desulfurization equipment using limestone as an absorbent can be used. A part of the exhaust gas G that has passed through the desulfurization equipment 70 is discharged from the chimney 71 into the atmosphere outside the system through the exhaust gas flow path L1.

[0020] The steam turbine 80 is a device that obtains power from the superheated steam supplied from the boiler 40, rotates, and drives the connected generator 81. The generator 81 is driven by the steam turbine 80 to generate electric power. The steam that has driven the steam turbine 80 is guided to the condenser 82 and liquefied, and then supplied to the boiler 40 as feed water.

[0021] The exhaust gas extraction unit 90 is a device that branches a part of the exhaust gas G flowing through the exhaust gas flow path L1 into the exhaust gas extraction flow path L2 and guides it to at least one of the fuel supply equipment 10, the fuel storage tank 20, and the conveying units 30 and 35. The exhaust gas extraction unit 90 includes a blower (pressure boosting unit) 91, a cooler (cooling unit) 92, a dehumidifier (dehumidifying unit) 93, a flow rate adjustment unit 94, a storage equipment 95, a control device 96, an oxygen measurement unit 97a, an oxygen measurement unit 97b, an oxygen measurement unit 97c, a temperature measurement unit 98, and a humidity measurement unit 99.

[0022] The blower 91 is a device that extracts a part of the exhaust gas G flowing through the exhaust gas flow path L1, boosts the pressure of the exhaust gas G guided to the exhaust gas extraction flow path L2, and discharges it to the cooler 92. The rotation speed of the blower 91 is controlled by the control device 96.

[0023] The cooler 92 is a device that cools the exhaust gas G discharged from the blower 91 by heat exchange with a heat transfer medium (for example, air such as the atmosphere or cooling water such as seawater) that is not mixed with the exhaust gas G. As the exhaust gas G supplied to the cooler 92 passes through the cooler 92, its temperature decreases, and the water that condenses as the temperature decreases is removed.

[0024] The upstream and downstream sides of the cooler 92 in the exhaust gas extraction passage L2 are connected by a cooling bypass passage 92a. A flow control valve 92b is located in the cooling bypass passage 92a. The control device 96 can adjust the ratio of the flow rate of exhaust gas G passing through the cooler 92 to the flow rate of exhaust gas G passing through the cooling bypass passage 92a by adjusting the opening degree of the flow control valve 92b. The exhaust gas G that has passed through the cooler 92 is mixed with the exhaust gas G that has passed through the cooling bypass passage 92a and led to the dehumidifier 93.

[0025] The dehumidifier 93 is a device that removes some of the moisture from the exhaust gas G cooled by the cooler 92. The dehumidifier 93 can be an adsorption type, for example, which removes moisture by passing the exhaust gas G through an adsorbent that adsorbs moisture, but other methods may also be used.

[0026] The upstream and downstream sides of the dehumidifier 93 in the exhaust gas extraction passage L2 are connected by a dehumidification bypass passage 93a. A flow rate control valve 93b is located in the dehumidification bypass passage 93a. The control device 96 can adjust the ratio of the flow rate of exhaust gas G passing through the dehumidifier 93 to the flow rate of exhaust gas G passing through the dehumidification bypass passage 93a by adjusting the opening degree of the flow rate control valve 93b. The exhaust gas G that has passed through the dehumidifier 93 is mixed with the exhaust gas G that has passed through the dehumidification bypass passage 93a and led to the flow rate adjustment unit 94.

[0027] The flow rate adjustment unit 94 is a device that adjusts the amount of exhaust gas G, from which some moisture has been removed by the dehumidifier 93, supplied to at least one of the fuel supply equipment 10, the fuel storage tank 20, and the transport unit 30. The flow rate adjustment unit 94 has a damper 94a that adjusts the amount of exhaust gas G supplied from the exhaust gas extraction passage L2 to the fuel supply equipment 10, a damper 94b that adjusts the amount of exhaust gas G supplied from the exhaust gas extraction passage L2 to the fuel storage tank 20, and a damper 94c that adjusts the amount of exhaust gas G supplied from the exhaust gas extraction passage L2 to the transport unit 30. The opening degrees of dampers 94a, 94b, and 94c are adjusted by the control device 96.

[0028] The storage facility 95 is a facility for storing exhaust gas G from which some of the moisture has been removed by the dehumidifier 93. The control device 96 controls the on-off valve 95a to the open state when the opening of dampers 94a, 94b, and 94c is set to 0 and exhaust gas G is not circulated, thereby supplying exhaust gas G from the exhaust gas extraction passage L2 to the storage facility 95. The control device 96 controls the on-off valve 95a to the open state when the boiler 40 is stopped and exhaust gas G is not supplied to the exhaust gas extraction section 90, thereby supplying exhaust gas G from the storage facility 95 to the exhaust gas extraction passage L2.

[0029] The control device 96 is a device that controls each part of the exhaust gas extraction unit 90. The control device 96 receives the oxygen concentration measured by the oxygen measurement unit 97a, oxygen measurement unit 97b, and oxygen measurement unit 97c. The control device 96 receives the temperature (°C) of the exhaust gas G measured by the temperature measurement unit 98. The control device 96 receives the relative humidity (%RH) of the exhaust gas G measured by the humidity measurement unit 99.

[0030] The control device 96 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example. The CPU reads this program into the RAM and performs information processing and calculations to realize the various functions.

[0031] The oxygen measurement unit 97a is a device that measures the oxygen concentration in the fuel storage space 11a of the bunker 11. The oxygen measurement unit 97a transmits the measured oxygen concentration to the control device 96.

[0032] The oxygen measurement unit 97b is a device that measures the oxygen concentration in the fuel storage space 20a of the fuel storage tank 20. The oxygen measurement unit 97b transmits the measured oxygen concentration to the control device 96.

[0033] The oxygen measurement unit 97c is a device that measures the oxygen concentration in the space through which the transport unit 30 transports biomass fuel. The oxygen measurement unit 97c transmits the measured oxygen concentration to the control device 96.

[0034] The temperature measuring unit 98 is a device that measures the temperature (°C) of exhaust gas G supplied to at least one of the fuel supply equipment 10, fuel storage tank 20, and transport unit 30 via the flow rate adjustment unit 94. The temperature measuring unit 98 transmits the measured temperature to the control device 96.

[0035] The humidity measuring unit 99 is a device that measures the relative humidity (%RH) of exhaust gas G supplied to at least one of the fuel supply equipment 10, fuel storage tank 20, and transport unit 30 via the flow rate adjustment unit 94. The humidity measuring unit 99 transmits the measured humidity to the control device 96.

[0036] Next, the operation of the exhaust gas extraction unit 90 will be described with reference to Figure 2. Figure 2 is a flowchart showing the operation of the exhaust gas extraction unit 90 of a boiler system 100 according to one embodiment of the present disclosure. Each step shown in Figure 2 is executed by the control program of the control device 96.

[0037] First, in the process from step S101 to step S107, the control device 96 controls each part of the exhaust gas extraction unit 90 so that the oxygen concentration in the space where the biomass fuel is present is below a predetermined concentration.

[0038] In step S101, the control device 96 determines whether the oxygen concentration measured by the oxygen measuring unit 97a is below a predetermined concentration. If it is YES, the process proceeds to step S102; otherwise, the process proceeds to step S105. The predetermined concentration is set lower than the lower explosion limit oxygen concentration of the biomass fuel stored in the fuel storage space 11a of the bunker 11, and is preferably set to, for example, 11%.

[0039] In step S102, the control device 96 reduces the opening of the damper 94a by a predetermined opening to reduce the amount of exhaust gas G supplied to the bunker 11. This is because the oxygen concentration measured by the oxygen measuring unit 97a is below a predetermined concentration, and there is no need to further reduce the oxygen concentration in the fuel storage space 11a of the bunker 11.

[0040] In step S103, the control device 96 determines whether the opening of the damper 94a is at the minimum opening (for example, the opening at which the flow rate of exhaust gas G becomes 0). If YES, the process proceeds to step S104; otherwise, the process proceeds to step S108.

[0041] In step S104, the control device 96 reduces the rotational speed of the blower 91 to reduce the discharge amount of exhaust gas G from the blower 91. This is because the damper 94a is at its minimum opening and the amount of exhaust gas G supplied to the bunker 11 cannot be further reduced. The blower's discharge amount is reduced to reduce the blower's power consumption so that the blower 91 does no unnecessary work when the damper 94a is at zero opening. In addition, as will be described later, similar control is performed on dampers other than damper 94a, but even when the opening of all dampers controlled from S101 to S102 is 0, the control flow from S108 onwards is necessary in order to supply the extracted exhaust gas G to the storage facility 95.

[0042] In step S105, the control device 96 increases the opening of the damper 94a by a predetermined opening to increase the amount of exhaust gas G supplied to the bunker 11. This is because the oxygen concentration measured by the oxygen measuring unit 97a is higher than a predetermined concentration, and it is necessary to reduce the oxygen concentration in the fuel storage space 11a of the bunker 11.

[0043] In step S106, the control device 96 determines whether the opening of the damper 94a is at its maximum opening. If it is YES, it proceeds to step S107; otherwise, it proceeds to step S108.

[0044] In step S107, the control device 96 increases the rotational speed of the blower 91 to increase the discharge amount of exhaust gas G from the blower 91. This is because the damper 94a is at its maximum opening and the amount of exhaust gas G supplied to the bunker 11 cannot be further increased.

[0045] In the processes described above from steps S101 to S107, the control device 96 controlled the opening degree of the damper 94a and the rotation speed of the blower 91 based on the oxygen concentration in the fuel storage space 11a of the bunker 11 measured by the oxygen measuring unit 97a. In other words, although the processes described above from steps S101 to S107 were performed with the damper 94a and blower 91 as the controlled objects of the control device 96, the same process is performed for other controlled objects as well.

[0046] In this embodiment, if multiple oxygen concentration meters are installed, the exhaust gas requirements may be reversed. However, when control is performed according to this flowchart, in both the "increase" and "decrease" processes of the exhaust gas supply, dampers 94a to 94c, which individually control the supply amount, are controlled first, and when the individual control reaches its limit, the blower 91, which controls the overall system, is controlled. If there are multiple control targets where the dampers are fully closed and fully open at the same time, the control limit of the individual control has been exceeded, so it is preferable to maintain the current discharge rate of the blower 91 or to increase the discharge rate by prioritizing the fully open damper side. On the control target side where the damper is fully closed, the oxygen concentration gradually increases due to the outflow of exhaust gas, so the damper will no longer be fully closed over time. On the other hand, the signal from the control target side where the damper is fully open to increase (or maintain) the discharge rate of the blower 91 remains unchanged, so the control to increase (or maintain) the discharge rate continues.

[0047] Other controlled components are the damper 94b and the blower 91. In this case, during the process from step S101 to step S107, the control device 96 controls the opening degree of the damper 94b and the rotation speed of the blower 91 based on the oxygen concentration in the fuel storage space 20a of the fuel storage tank 20 measured by the oxygen measuring unit 97b.

[0048] Other controlled objects are the damper 94c and the blower 91. In this case, during the process from step S101 to step S107, the control device 96 controls the opening degree of the damper 94c and the rotation speed of the blower 91 based on the oxygen concentration in the space through which the transport unit 30 transports biomass fuel, as measured by the oxygen measuring unit 97c.

[0049] Next, in the process from step S108 to step S110, the control device 96 controls each part of the exhaust gas extraction unit 90 so that the temperature of the exhaust gas G supplied to the space where the biomass fuel is present is below a predetermined temperature.

[0050] In step S108, the control device 96 determines whether the temperature of the exhaust gas G measured by the temperature measuring unit 98 is below a predetermined temperature. If it is YES, the process proceeds to step S109; otherwise, the process proceeds to step S110. The predetermined temperature is preferably set to, for example, 60°C to avoid temperature rise due to oxidation of the biomass fuel (spontaneous oxidation temperature rise).

[0051] In step S109, the control device 96 increases the opening of the flow control valve 92b by a predetermined opening to reduce the flow rate of exhaust gas G passing through the cooler 92. This is because increasing the flow rate of exhaust gas G passing through the cooling bypass passage 92a reduces the flow rate of exhaust gas G passing through the cooler 92. As the flow rate of exhaust gas G passing through the cooler 92 decreases, the temperature of the exhaust gas G measured by the temperature measuring unit 98 rises.

[0052] In step S110, the control device 96 reduces the opening of the flow control valve 92b by a predetermined opening to increase the flow rate of exhaust gas G passing through the cooler 92. This is because reducing the flow rate of exhaust gas G passing through the cooling bypass passage 92a increases the flow rate of exhaust gas G passing through the cooler 92. As the flow rate of exhaust gas G passing through the cooler 92 increases, the temperature of the exhaust gas G measured by the temperature measuring unit 98 decreases.

[0053] Next, in the process from step S111 to step S113, the control device 96 controls each part of the exhaust gas extraction unit 90 so that the relative humidity of the exhaust gas G supplied to the space where the biomass fuel is present is below a predetermined humidity.

[0054] In step S111, the control device 96 determines whether the relative humidity of the exhaust gas G measured by the humidity measuring unit 99 is below a predetermined humidity. If it is YES, the process proceeds to step S112; otherwise, the process proceeds to step S113. The predetermined humidity is preferably set to, for example, 70% RH to avoid heat generation and carbon monoxide release due to accelerated fermentation of the biomass fuel. By setting the relative humidity of the space containing the biomass fuel to 70% RH or less, the moisture content of the biomass fuel can be kept below 10%, thereby preventing accelerated fermentation of the biomass fuel.

[0055] In step S112, the control device 96 increases the opening of the flow control valve 93b by a predetermined opening to reduce the flow rate of exhaust gas G passing through the dehumidifier 93. This is because increasing the flow rate of exhaust gas G passing through the dehumidification bypass channel 93a reduces the flow rate of exhaust gas G passing through the dehumidifier 93. As the flow rate of exhaust gas G passing through the dehumidifier 93 decreases, the relative humidity of the exhaust gas G measured by the humidity measuring unit 99 increases.

[0056] In step S113, the control device 96 reduces the opening of the flow control valve 93b by a predetermined opening to increase the flow rate of exhaust gas G passing through the dehumidifier 93. This is because reducing the flow rate of exhaust gas G passing through the dehumidification bypass channel 93a increases the flow rate of exhaust gas G passing through the dehumidifier 93. As the flow rate of exhaust gas G passing through the dehumidifier 93 increases, the relative humidity of the exhaust gas G measured by the humidity measuring unit 99 decreases.

[0057] The control device 96 terminates the processing of this flowchart depending on whether it has executed step S112 or step S113. When the control device 96 extracts exhaust gas G from the exhaust gas flow path L1 to the exhaust gas extraction flow path L2 and operates the exhaust gas extraction unit 90, it repeats the operation of executing each process from step S101 to step S113 according to this flowchart.

[0058] Next, referring to Figure 3, we will explain the relationship between the temperature of the exhaust gas G that has passed through the cooler 92 and the position of the exhaust gas extraction passage L2. The positions P1 to P7 of the exhaust gas extraction passage L2 shown in Figure 3 correspond to the positions P1 to P7 shown in Figure 1.

[0059] As shown in Figure 3, the temperature of the exhaust gas G rises between the inlet position P1 of the blower 91 and the outlet position P2 of the blower 91. This is because the exhaust gas G is pressurized in the blower 91. From the outlet position P2 of the blower 91 to the inlet position P3 of the cooler 92, the temperature of the exhaust gas G remains constant.

[0060] The temperature of the exhaust gas G decreases between the inlet position P3 of the cooler 92 and the outlet position P4 of the cooler 92. This is because a portion of the exhaust gas G is cooled in the cooler 92. At position P4, the temperature of the exhaust gas G cooled in the cooler 92 increases due to mixing with the exhaust gas G passing through the cooling bypass passage 92a. The temperature of the exhaust gas G becomes constant at each position from position P4 to position P7, and at each position downstream of position P7.

[0061] Next, referring to Figure 4, we will explain the relationship between the temperature of the exhaust gas G that has passed through the dehumidifier 93 and the position of the exhaust gas extraction passage L2. The positions P1 to P7 of the exhaust gas extraction passage L2 shown in Figure 4 correspond to the positions P1 to P7 shown in Figure 1.

[0062] As shown in Figure 4, the relative humidity of the exhaust gas G decreases between the inlet position P1 of the blower 91 and the outlet position P2 of the blower 91. This is because the exhaust gas G is pressurized in the blower 91, causing its temperature to rise. From the outlet position P2 of the blower 91 to the inlet position P3 of the cooler 92, the relative humidity of the exhaust gas G remains constant.

[0063] The relative humidity of the exhaust gas G increases between the inlet position P3 of the cooler 92 and the outlet position P4 of the cooler 92. This is because a portion of the exhaust gas G is cooled in the cooler 92. At each position from position P4 to position P5, the relative humidity of the exhaust gas G remains constant.

[0064] Between the inlet position P5 of the dehumidifier 93 and the outlet position P6 of the dehumidifier 93, the relative humidity of the exhaust gas G decreases. This is because some of the moisture in the exhaust gas G is removed by the dehumidifier 93. At position P6, the relative humidity of the exhaust gas G dehumidified by the dehumidifier 93 increases due to mixing with the exhaust gas G passing through the dehumidification bypass channel 93a. At each position downstream of position P6, the relative humidity of the exhaust gas G remains constant.

[0065] The boiler system 100 of this embodiment described above provides the following functions and effects.

[0066] According to the boiler system 100 of this embodiment, a portion of the exhaust gas G discharged from the boiler 40 and led to the chimney 71 is branched off and guided by the exhaust gas extraction unit 90 to at least one of the bunker 11, fuel storage tank 20, and transport unit 30. In the exhaust gas extraction unit 90, the exhaust gas G is cooled by heat exchange with a heat transfer medium (air or cooling water) that is not mixed with the exhaust gas G, and then guided to at least one of the bunker 11, fuel storage tank 20, and transport unit 30. Since the exhaust gas G, whose oxygen has been reduced by combustion in the boiler 40, is not mixed with air or the like that increases oxygen, at least one of the bunker 11, fuel storage tank 20, and transport unit 30 will have a low oxygen concentration and a low temperature, thereby preventing the risk of biomass fuel ignition.

[0067] According to the boiler system 100 of this embodiment, in the exhaust gas extraction section 90, some of the moisture in the exhaust gas G is removed by the dehumidifier 93 and then guided to at least one of the bunker 11, fuel storage tank 20, and transport section 30. Therefore, it is possible to prevent the biomass fuel from becoming too moist and fermentation from being accelerated in at least one of the bunker 11, fuel storage tank 20, and transport section 30 to which the exhaust gas G is guided.

[0068] According to the boiler system 100 of this embodiment, the damper 94c adjusts the amount of exhaust gas G supplied to the transport unit 35 so that the oxygen concentration measured by the oxygen measuring unit 97c is below a predetermined concentration, thereby appropriately preventing the risk of the biomass fuel being transported in the transport unit 30 igniting.

[0069] According to the boiler system 100 of this embodiment, the damper 94a adjusts the amount of exhaust gas G supplied to the bunker 11 so that the oxygen concentration measured by the oxygen measuring unit 97a is below a predetermined concentration, thereby appropriately preventing the risk of biomass fuel stored in the bunker 11 igniting.

[0070] According to the boiler system 100 of this embodiment, the damper 94b adjusts the amount of exhaust gas G supplied to the fuel storage tank 20 so that the oxygen concentration measured by the oxygen measuring unit 97b is below a predetermined concentration, thereby appropriately preventing the risk of biomass fuel stored in the fuel storage tank 20 igniting.

[0071] According to the boiler system 100 of this embodiment, the cooler 92 cools the exhaust gas G so that the temperature measured by the temperature measuring unit 98 is below a predetermined temperature, thereby appropriately preventing the risk of biomass fuel ignition.

[0072] According to the boiler system 100 of this embodiment, the dehumidifier 93 removes some of the moisture from the exhaust gas G so that the humidity measured by the humidity measuring unit 99 is below a predetermined humidity, thereby appropriately preventing the biomass fuel from becoming too moist and fermentation from being accelerated.

[0073] [Other embodiments] In the above description, one oxygen measurement unit is installed in each of the bunker 11, fuel storage tank 20, and transport unit 30, but other configurations are also possible. For example, multiple oxygen measurement units may be installed in each of the bunker 11, fuel storage tank 20, and transport unit 30. In this case, the control device 96 may acquire the average value of multiple oxygen concentrations transmitted from the multiple oxygen measurement units, or it may acquire the highest concentration among the multiple oxygen concentrations.

[0074] Furthermore, in this embodiment, the control device 96 may prioritize the control of the opening degrees of dampers 94a, 94b, and 94c. For example, when increasing the opening degrees of all dampers 94a, 94b, and 94c, the control device 96 may prioritize increasing the opening degree of damper 94c, which is connected to the transport section 30 where there is a high risk of ignition due to friction from transporting biomass fuel, and may not prioritize increasing the opening degrees of the other dampers.

[0075] Furthermore, in this embodiment, in order to enhance resistance to oxidative corrosion caused by acidic substances such as NOx and SOx contained in the exhaust gas G, it is preferable to form the exhaust gas extraction passage L2 from a highly corrosion-resistant material such as stainless steel.

[0076] Furthermore, the boiler system 100 of this embodiment preferably includes wastewater treatment equipment for processing the water that condenses due to cooling in the cooler 92 and the water that is removed by the dehumidifier 93. In addition, the boiler system 100 of this embodiment preferably has shut-off valves placed between each position from position P0 to position P1 in order to facilitate maintenance of the blower 91, cooler 92 and dehumidifier 93, and is configured so that the shut-off valves at the necessary locations can be closed when performing maintenance.

[0077] The boiler system described in the embodiments above can be understood, for example, as follows. A boiler system according to a first aspect of the present disclosure comprises a crushing device (12) for crushing biomass fuel, a fuel storage unit (20) for storing the biomass fuel, a transport unit (30, 35) for transporting the biomass fuel, a boiler (40) for burning the biomass fuel crushed by the crushing device in a combustion unit to generate steam, and an exhaust gas extraction unit (90) for branching off a portion of the exhaust gas flowing through an exhaust gas passage (L1) that guides the exhaust gas discharged from the boiler to the outside of the system and guiding it to at least one of the fuel storage unit and the transport unit, wherein the exhaust gas extraction unit includes a cooling unit (92) for cooling the exhaust gas by heat exchange with a heat transfer medium that is not mixed with the exhaust gas, and a dehumidifying unit (93) for removing a portion of the moisture from the exhaust gas cooled by the cooling unit.

[0078] According to the boiler system of the first aspect of this disclosure, a portion of the exhaust gas discharged from the boiler and led out of the system is branched off and led to at least one of the fuel storage section and the transport section by an exhaust gas extraction section. In the exhaust gas extraction section, the exhaust gas is cooled by heat exchange with a heat transfer medium that is not mixed with the exhaust gas and is led to at least one of the fuel storage section and the transport section. Since the exhaust gas, whose oxygen has been reduced by combustion in the boiler, is not mixed with air or the like that increases oxygen, at least one of the fuel storage section and the transport section will have a low oxygen concentration and a low temperature, thereby preventing the risk of biomass fuel ignition.

[0079] According to the boiler system of the first aspect of this disclosure, in the exhaust gas extraction section, a portion of the moisture is removed from the exhaust gas by the dehumidification section and it is then guided to at least one of the fuel storage section and the transport section. Therefore, it is possible to prevent the biomass fuel from becoming high in moisture and fermentation from being promoted in at least one of the fuel storage section and the transport section to which the exhaust gas is guided.

[0080] In the boiler system according to a second aspect of the present disclosure, the following configuration is preferable in the first aspect: The exhaust gas extraction section has a flow rate adjustment section (94) that adjusts the amount of the exhaust gas, from which some of the moisture has been removed by the dehumidification section, supplied to at least one of the fuel storage section and the transport section.

[0081] According to the boiler system of the second aspect of this disclosure, by adjusting the amount supplied to at least one of the fuel storage unit and the transport unit using the flow rate adjustment unit, the risk of biomass fuel ignition can be appropriately prevented, and the risk of biomass fuel becoming high in moisture and fermentation being promoted can be appropriately prevented.

[0082] In the boiler system according to the third aspect of this disclosure, the following configuration is preferable in the second aspect: the system is further provided with oxygen measuring units (97a, 97b, 97c) that measure the oxygen concentration in the space for transporting the biomass fuel in the transporting unit and / or in the fuel storage space of the fuel storage unit, and the flow rate adjustment unit adjusts the amount of exhaust gas supplied to the transporting unit and / or the fuel storage unit so that the oxygen concentration measured by the oxygen measuring unit is below a predetermined concentration.

[0083] According to the boiler system of the third aspect of this disclosure, the flow rate adjustment unit adjusts the amount of exhaust gas supplied to the transport unit and / or fuel storage unit so that the oxygen concentration measured by the oxygen measurement unit is below a predetermined concentration, thereby appropriately preventing the risk of ignition of the biomass fuel transported by the transport unit and / or the biomass fuel stored in the fuel storage unit, and appropriately preventing the biomass fuel from becoming too moist and fermentation from being accelerated.

[0084] In the boiler system according to the fourth aspect of this disclosure, the following configuration is preferable in the third aspect: that is, the predetermined concentration is any oxygen concentration of 11% or less.

[0085] According to the boiler system of the fourth aspect of this disclosure, the risk of biomass fuel stored in the fuel storage unit igniting can be appropriately prevented by adjusting the amount of exhaust gas supplied to the fuel storage unit so that the oxygen concentration measured by the oxygen measurement unit becomes any oxygen concentration of 11% or less.

[0086] In a boiler system according to a fifth aspect of this disclosure, it is preferable that any of the first to fourth aspects further have the following configuration: namely, a temperature measuring unit (98) for measuring the temperature of the exhaust gas supplied to at least one of the fuel storage unit and the transport unit, and the cooling unit cools the exhaust gas so that the temperature measured by the temperature measuring unit is below a predetermined temperature.

[0087] According to the boiler system of the fifth aspect of this disclosure, the cooling unit cools the exhaust gas so that the temperature measured by the temperature measuring unit is below a predetermined temperature, thereby appropriately preventing the risk of biomass fuel ignition.

[0088] In the boiler system according to the sixth aspect of this disclosure, the following configuration is preferable in the fifth aspect: that the predetermined temperature is any temperature of 60°C or lower.

[0089] According to the boiler system of the sixth aspect of this disclosure, the cooling unit cools the exhaust gas to any temperature of 60°C or less as measured by the temperature measuring unit, thereby appropriately preventing the risk of biomass fuel ignition.

[0090] In the boiler system according to the seventh aspect of this disclosure, it is preferable that any of the first to fourth aspects further have the following configuration: that is, a humidity measuring unit (99) for measuring the relative humidity of the exhaust gas supplied to at least one of the fuel storage unit and the transport unit, and the dehumidifying unit removes a portion of the moisture from the exhaust gas so that the humidity measured by the humidity measuring unit is below a predetermined humidity.

[0091] According to the boiler system of the seventh aspect of this disclosure, the dehumidification unit removes a portion of the moisture from the exhaust gas so that the humidity measured by the humidity measurement unit is below a predetermined humidity, thereby appropriately preventing the biomass fuel from becoming too moist and fermentation from being accelerated.

[0092] In the boiler system according to the eighth aspect of this disclosure, the following configuration is preferable in the seventh aspect: the predetermined humidity is any relative humidity of 70% RH or less.

[0093] According to the boiler system of the eighth aspect of this disclosure, the dehumidification unit removes a portion of the moisture from the exhaust gas so that the humidity measured by the humidity measuring unit is 70 RH or less, thereby appropriately preventing the biomass fuel from becoming too moist and fermentation from being accelerated.

[0094] In the boiler system according to the ninth aspect of this disclosure, it is preferable that any of the first to fourth aspects further have the following configuration: namely, the biomass fuel is a pellet formed by compressing crushed biomass particles.

[0095] According to the boiler system of the ninth aspect of this disclosure, it is possible to appropriately prevent biomass fuel, which is a pellet formed by compressing biomass particles, from becoming high in moisture and thus accelerating fermentation. [Explanation of Symbols]

[0096] 1. Fuel receiving facility 10 Fuel supply equipment 11. Bunka (fuel storage section) 11a Fuel storage space 12 Mill (Grinding device) 20 Fuel storage tank (fuel storage section) 20a Fuel storage space 30,35 Conveyor section 40 Boilers 41 Combustion device 50 Denitration equipment 60 Dust collection equipment 70 Desulfurization equipment 71 Chimney 80 Steam Turbine 81 Generator 82 Condenser 90 Exhaust gas extraction section 91 Blower 92 Cooler (cooling section) 92a Cooling bypass channel 92b Flow control valve 93 Dehumidifier (dehumidification section) 93a Dehumidification bypass channel 93b Flow control valve 94 Flow rate adjustment section 94a, 94b, 94c damper 95 Storage facilities 95a Shut-off valve 96 Control device 97a, 97b, 97c Oxygen Measurement Unit 98 Temperature Measurement Unit 99 Humidity Measurement Unit 100 Boiler Systems G exhaust gas L1 Exhaust gas flow path L2 Exhaust Gas Extraction Channel

Claims

1. A crushing device for crushing biomass fuel, A fuel storage unit for storing the aforementioned biomass fuel, A transport unit for transporting the biomass fuel, The aforementioned crushing device burns the crushed biomass fuel in a combustion device to generate steam in a boiler, The system includes an exhaust gas extraction unit that branches off a portion of the exhaust gas flowing through an exhaust gas passage that guides the exhaust gas discharged from the boiler to the outside of the system and guides it to at least one of the fuel storage unit and the transport unit, The exhaust gas extraction section is, A cooling unit that cools the exhaust gas by heat exchange with a heat transfer medium that is not mixed with the exhaust gas, A boiler system comprising a dehumidifying unit that removes a portion of the moisture from the exhaust gas cooled by the cooling unit.

2. The exhaust gas extraction section is, The boiler system according to claim 1, further comprising a flow rate adjustment unit for adjusting the amount of exhaust gas from which a portion of the moisture has been removed by the dehumidification unit, supplied to at least one of the fuel storage unit and the transport unit.

3. The transport unit is equipped with an oxygen measuring unit for measuring the oxygen concentration in the space for transporting the biomass fuel and / or in the fuel storage space of the fuel storage unit. The boiler system according to claim 2, wherein the flow rate adjustment unit adjusts the amount of exhaust gas supplied to the transport unit and / or the fuel storage unit so that the oxygen concentration measured by the oxygen measurement unit is below a predetermined concentration.

4. The boiler system according to claim 3, wherein the predetermined concentration is any concentration of 11% or less.

5. The system includes a temperature measuring unit for measuring the temperature of the exhaust gas supplied to at least one of the fuel storage unit and the transport unit, The boiler system according to any one of claims 1 to 4, wherein the cooling unit cools the exhaust gas so that the temperature measured by the temperature measuring unit becomes below a predetermined temperature.

6. The boiler system according to claim 5, wherein the predetermined temperature is any temperature of 60°C or less.

7. The system includes a humidity measuring unit that measures the relative humidity of the exhaust gas supplied to at least one of the fuel storage unit and the transport unit, The boiler system according to any one of claims 1 to 4, wherein the dehumidifying unit removes a portion of the moisture from the exhaust gas so that the relative humidity measured by the humidity measuring unit becomes less than or equal to a predetermined humidity.

8. The boiler system according to claim 7, wherein the predetermined humidity is any relative humidity of 70% RH or less.

9. The boiler system according to any one of claims 1 to 4, wherein the biomass fuel is pellets obtained by compressing and molding crushed biomass particles.

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