Boiler system, and operation method for a boiler system
Patent Information
- Authority / Receiving Office
- MY · MY
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-04-11
- Publication Date
- 2026-07-08
AI Technical Summary
Biomass combustion ash in boilers often has a low melting point, causing it to stick to the inner walls and reduce heat exchange efficiency, which is not effectively addressed by existing techniques.
A boiler system that stores and supplies different types of solid fuels, including biomass and coal, with controlled sulfur and additive concentrations to increase the melting point of combustion ash, using a fuel supply unit and dust removal device to manage ash composition and reuse ash as additives.
The system effectively increases the melting point of combustion ash, preventing adhesion to the boiler walls and maintaining heat exchange efficiency, while reducing CO2 emissions and the cost of additives by reusing collected ash.
Abstract
Description
Boiler system and method for operating the boiler system
[0001] This disclosure relates to a boiler system and a method for operating the boiler system. This application claims the benefit of priority from Japanese Patent Application No. 2021-91171 filed on May 31, 2021, the contents of which are incorporated herein by reference.
[0002] In recent years, in order to prevent global warming, ２ There is a demand for a reduction in carbon dioxide emissions. To this end, technologies for burning biomass in addition to coal or for burning biomass instead of coal in boilers (for example, Patent Document 1) have been studied.
[0003] Japanese Patent Application Laid-Open No. 2021-1701
[0004] However, depending on the type of biomass, the combustion ash produced by burning the biomass may have a low melting point, which can cause the ash to melt and adhere to the inner wall of the boiler, resulting in a decrease in the boiler's heat exchange efficiency.
[0005] In view of these problems, the present disclosure aims to provide a boiler system capable of increasing the melting point of combustion ash, and a method for operating the boiler system.
[0006] In order to solve the above problems, a boiler system according to one embodiment of the present disclosure includes a plurality of fuel storage sections each storing a different type of solid fuel selected from a plurality of types of biomass, or a different type of solid fuel selected from one or more types of biomass and one or more types of coal, and a fuel supply section that supplies the solid fuel from each of the plurality of fuel storage sections to a furnace so that the calcium concentration contained in the combustion ash after combustion is 30 mass% or less.
[0007] The fuel supply unit may also control the amount of solid fuel supplied to the furnace from each of the multiple fuel storage units so that the concentration of sulfur contained in the entire solid fuel supplied to the furnace is 20 mmol / kg or more.
[0008] The fuel supply unit may also control the amount of solid fuel supplied from each of the plurality of fuel reservoirs to the furnace so that the concentrations of silica and alumina contained in the combustion ash are 40 mass % or more.
[0009] The furnace may further include an additive storage section for storing an additive containing at least silica and alumina, and the fuel supply section may supply the additive to the furnace in addition to the solid fuel.
[0010] The additive may also be ash from the combustion of either or both of coal and biomass.
[0011] The present invention may also include a dust collector that collects combustion ash from the combustion exhaust gas discharged from the furnace, and the additive may be the combustion ash collected by the dust collector.
[0012] The system may also include a heat exchanger that exchanges heat between the combustion exhaust gas discharged from the furnace and water, and a cleaning section that cleans the combustion ash with the water that has been heat exchanged by the heat exchanger, and the additive may be the combustion ash after being cleaned by the cleaning section.
[0013] In order to solve the above problem, another boiler system according to one embodiment of the present disclosure includes a dust removal device that recovers combustion ash from the combustion exhaust gas discharged from the furnace, a heat exchanger that exchanges heat between the combustion exhaust gas discharged from the furnace and water, a cleaning section that cleans the combustion ash with the water that has been heat exchanged by the heat exchanger, and a fuel supply section that supplies the combustion ash that has been cleaned by the cleaning section and biomass to the furnace.
[0014] In order to solve the above problems, one embodiment of the present disclosure provides a method for operating a boiler system including a plurality of fuel storage sections each storing a different type of solid fuel selected from a plurality of types of biomass, or a method for storing a different type of solid fuel selected from one or more types of biomass and one or more types of coal, and supplies the solid fuel from each of the plurality of fuel storage sections to a furnace so that the calcium concentration in the combustion ash after combustion is 30 mass% or less.
[0015] According to the present disclosure, it is possible to increase the melting point of combustion ash.
[0016] Fig. 1 is a diagram illustrating a boiler system according to this embodiment. Fig. 2 is a diagram illustrating a fuel supply unit according to this embodiment. Fig. 3 is a flowchart illustrating the process flow of an operating method for a boiler system according to this embodiment. Fig. 4 is a diagram illustrating the relationship between aluminosilicate and chloride ions contained in combustion ash. Fig. 5 is a diagram illustrating the relationship between sulfur and chloride ions contained in the entire solid fuel. Fig. 6 is a diagram illustrating the relationship between calcium and chloride ions contained in combustion ash.
[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Dimensions, materials, specific numerical values, etc. shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.
[0018] [Boiler system 100] Fig. 1 is a diagram illustrating a boiler system 100 according to this embodiment. In Fig. 1, solid arrows indicate the flows of solid fuel, combustion ash, and water. In Fig. 1, dashed arrows indicate the flow of air.
[0019] As shown in FIG. 1 , the boiler system 100 includes a fuel supply unit 110, a furnace 112, a forced draft fan 114, a denitration device 120, an air preheater 122, a dust removal device 124, an induced draft fan 126, a reheater 128, a desulfurization device 130, a boost-up fan 132, a pump 140, a heat exchanger 142, a cleaning section 144, and a drying section 146.
[0020] The fuel supply unit 110 supplies the solid fuel and additives to the furnace 112. The fuel supply unit 110 will be described in more detail below.
[0021] An air intake passage 10 is connected to the furnace 112. A forced draft fan 114 is provided in the air intake passage 10. Air supplied by the forced draft fan 114 is preheated by an air preheater 122 (described later) and is introduced to the furnace 112 through the air intake passage 10. The furnace 112 burns solid fuel supplied by the fuel supply unit 110 with the air. The furnace 112 is, for example, a pulverized coal boiler (PC boiler) or a circulating fluidized bed boiler (CFB boiler). Combustion exhaust gas generated in the furnace 112 passes through a flue 20 and is released into the atmosphere from a chimney 30.
[0022] The combustion exhaust gas generated by burning the solid fuel in the furnace 112 contains nitrogen oxides (NOx), sulfur oxides (SOx), combustion ash, mercury, and halogens. For this reason, a denitration device 120, an air preheater 122, a dust removal device 124, an induced draft fan 126, a reheater 128, a desulfurization device 130, and a boost-up fan 132 are provided in the flue 20 connecting the furnace 112 and the chimney 30.
[0023] The induced draft fan 126 and the boost-up fan 132 guide the combustion exhaust gases produced in the furnace 112 to the chimney 30 .
[0024] The denitration device 120 includes a denitration catalyst and reduces nitrogen oxides contained in the combustion exhaust gas.
[0025] The air preheater 122 is provided downstream of the denitration device 120 in the flue 20. The air preheater 122 exchanges heat between the combustion exhaust gas from which nitrogen oxides have been removed by the denitration device 120 and the air passing through the air intake passage 10. That is, the air preheater 122 heats the air supplied by the forced draft fan 114 with the heat contained in the combustion exhaust gas.
[0026] The dust remover 124 is provided downstream of the air preheater 122 in the flue 20. The dust remover 124 is, for example, an electrostatic precipitator or a bag filter. The dust remover 124 recovers combustion ash from the combustion exhaust gas.
[0027] The induced draft fan 126 is provided downstream of the dust removal device 124 in the flue 20. The reheater 128 is provided downstream of the induced draft fan 126 in the flue 20. The reheater 128 exchanges heat between the flue gas flowing between the induced draft fan 126 and the desulfurization device 130 and the flue gas flowing between the boost-up fan 132 and the chimney 30.
[0028] The desulfurization device 130 is provided downstream of the induced draft fan 126 in the flue 20. The desulfurization device 130 dissolves sulfur oxides and hydrogen chloride (HCl) contained in the combustion exhaust gas in an aqueous solution and removes them. The boost-up fan 132 is provided downstream of the desulfurization device 130 in the flue 20.
[0029] The pump 140 supplies water to the heat exchanger 142. The heat exchanger 142 is provided in the flue 20 between the air preheater 122 and the dust remover 124. The heat exchanger 142 is an indirect heat exchanger. The heat exchanger 142 exchanges heat between the water supplied by the pump 140 and the combustion exhaust gas flowing through the flue 20. That is, the heat exchanger 142 heats the water with the heat contained in the combustion exhaust gas. The heat exchanger 142 heats the water to, for example, a temperature of 70°C or higher and lower than 100°C (approximately 80°C).
[0030] The combustion ash collected by the dust removal device 124 and the water heated by the heat exchanger 142 are introduced into the cleaning section 144. The cleaning section 144 cleans the combustion ash with the water heated by the heat exchanger 142. The cleaned combustion ash is introduced into the drying section 146.
[0031] The water after washing also contains potassium and phosphorus, so the water after washing may be used as fertilizer after undergoing a predetermined treatment.
[0032] The drying section 146 exchanges heat between the combustion ash cleaned by the cleaning section 144 and the air flowing through the air intake passage 10. The drying section 146 is an indirect heat exchanger. The combustion ash is dried by the heat exchange between the combustion ash and the air in the drying section 146. The combustion ash after the heat exchange is led to the fuel supply unit 110. The air after the heat exchange is led to the air intake passage 10.
[0033] [Fuel Supply Unit 110] Next, the fuel supply unit 110 will be described. Fig. 2 is a diagram illustrating the fuel supply unit 110 according to this embodiment. As shown in Fig. 2, the fuel supply unit 110 includes a first fuel storage section 210, a second fuel storage section 212, an additive storage section 214, and a fuel supply section 220.
[0034] The first fuel storage unit 210 (fuel storage unit) stores biomass (solid fuel). The biomass is one or more of woody biomass, herbaceous biomass, and waste-based biomass. Examples of woody biomass include wood, sawdust, and bark. Examples of herbaceous (plant) biomass include sugarcane, sorghum, bamboo, wheat straw, and rice straw. Examples of waste-based biomass include empty fruit bunches (EFBs) and palm kernel shells (PKSs) generated as a result of producing palm oil from palm trees. The first fuel storage unit 210 may also store biomass pellets. Pellets are solid fuel (biomass) processed into a cylindrical shape of several millimeters to several centimeters.
[0035] The second fuel reservoir 212 (fuel reservoir) stores coal (solid fuel). The coal is one or more of anthracite, semi-anthracite, bituminous coal, sub-bituminous coal, and lignite.
[0036] The additive reservoir 214 stores an additive. The additive is silica (SiO ２ ) and alumina (Al ２ O ３ For example, the additive contains at least aluminosilicate (SiO ２ ・Al ２ O ３ In this embodiment, the additive storage section 214 stores the combustion ash, which has been cleaned by the cleaning section 144 and dried by the drying section 146, as an additive.
[0037] The fuel supply unit 220 supplies additives to the furnace 112 in addition to biomass and coal. In this embodiment, the fuel supply unit 220 includes a first supply pipe 230, a second supply pipe 232, a third supply pipe 234, a first valve 240, a second valve 242, a third valve 244, a bunker 250, a mill 252, and a fuel control unit 260.
[0038] The first supply pipe 230 is a pipe that connects the first fuel storage section 210 and the bunker 250. The second supply pipe 232 is a pipe that connects the second fuel storage section 212 and the bunker 250. The third supply pipe 234 is a pipe that connects the additive storage section 214 and the bunker 250.
[0039] The first valve 240 is provided in the first supply pipe 230. The first valve 240 changes the opening degree of a flow path formed in the first supply pipe 230. In this embodiment, the first fuel storage unit 210 is located above the bunker 250. Therefore, when the first valve 240 is opened, the biomass stored in the first fuel storage unit 210 is supplied to the bunker 250 by its own weight.
[0040] The second valve 242 is provided in the second supply pipe 232. The second valve 242 changes the opening degree of a flow path formed in the second supply pipe 232. Similar to the first fuel storage section 210, in this embodiment, the second fuel storage section 212 is located above the bunker 250. Therefore, when the second valve 242 is opened, the coal stored in the second fuel storage section 212 is supplied to the bunker 250 by its own weight.
[0041] The third valve 244 is provided in the third supply pipe 234. The third valve 244 changes the opening degree of a flow path formed in the third supply pipe 234. Similar to the first fuel storage section 210 and the second fuel storage section 212, in this embodiment, the additive storage section 214 is located above the bunker 250. Therefore, when the third valve 244 is opened, the coal stored in the additive storage section 214 is supplied to the bunker 250 by its own weight.
[0042] The first valve 240, the second valve 242, and the third valve 244 are, for example, rotary valves.
[0043] The bunker 250 mixes the biomass, coal, and additives. The mill 252 pulverizes the biomass, coal, and additives mixed by the bunker 250. The biomass, coal, and additives pulverized by the mill 252 are supplied to the combustion port of the furnace 112.
[0044] The fuel control unit 260 is configured by a semiconductor integrated circuit including a CPU (central processing unit). The fuel control unit 260 reads programs, parameters, and the like for operating the CPU from a ROM. The fuel control unit 260 manages and controls the entire fuel supply unit 220 in cooperation with a RAM serving as a work area and other electronic circuits. In this embodiment, the fuel control unit 260 adjusts the opening degree of the first valve 240, the opening degree of the second valve 242, and the opening degree of the third valve 244.
[0045] Specifically, the fuel control unit 260 adjusts the opening degree of the first valve 240, the opening degree of the second valve 242, and the opening degree of the third valve 244 so that the mixture of solid fuel and additives supplied from the mill 252 to the furnace 112 satisfies the following conditions (A), (B), and (C): Condition (A) The concentration of silica and alumina contained in the combustion ash (combustion ash) generated by combustion in the furnace 112 is 40 mass % (wt %) or more; Condition (B) The concentration of sulfur (S) contained in the entire solid fuel (biomass and coal) supplied to the furnace 112 is 20 mmol / kg or more; and Condition (C) The concentration of calcium (Ca) contained in the combustion ash after combustion is 30 mass % or less.
[0046] Coal contains less calcium than biomass. Coal also contains more silica and alumina than biomass. Coal also contains more sulfur than biomass. As described above, the additive contains silica and alumina.
[0047] The amounts per unit volume of silica, alumina, sulfur, and calcium contained in the solid fuel (biomass) stored in the first fuel storage section 210, the solid fuel (coal) stored in the second fuel storage section 212, and the additive stored in the additive storage section 214 are measured in advance using a predetermined device. The predetermined device is an inductively coupled plasma (ICP) mass spectrometry (ICP-MASS) device, an ICP atomic emission spectrometry (ICP-AES) device, or an atomic absorption spectrometry (AAS) device.
[0048] [Operation Method of Boiler System] Next, a description will be given of a method of operating the boiler system 100. Fig. 3 is a flowchart illustrating the process flow of the operation method of the boiler system 100 according to this embodiment. As shown in Fig. 3, the operation method of the boiler system 100 includes a fuel adjustment step S110 and a supply step S120.
[0049] [Fuel adjustment process S110] The fuel control unit 260 adjusts the opening degree of the first valve 240, the opening degree of the second valve 242, and the opening degree of the third valve 244 so that the mixture of solid fuel and additives supplied from the mill 252 to the furnace 112 satisfies the above conditions (A), (B), and (C).
[0050] Then, the biomass, coal, and additives are supplied to the bunker 250. The bunker 250 mixes the biomass, coal, and additives. The biomass, coal, and additives mixed by the bunker 250 satisfy all of the above conditions (A), (B), and (C).
[0051] The mixture produced by the bunker 250 is then directed to a mill 252 .
[0052] [Feeding Step S120] The mill 252 feeds the mixture produced by the bunker 250 to the furnace 112.
[0053] As described above, the boiler system 100 and the operating method of the boiler system 100 according to this embodiment supply a mixture of solid fuel and additives to the furnace 112 so as to satisfy the above conditions (A) and (C). As a result, the boiler system 100 can increase the melting point of combustion ash produced in the furnace 112. Therefore, the boiler system 100 can suppress adhesion of combustion ash to the inner wall of the furnace 112. In other words, the boiler system 100 can promote the detachment of combustion ash adhering to the inner wall of the furnace 112. Therefore, the boiler system 100 can suppress a decrease in heat exchange efficiency.
[0054] Furthermore, in the boiler system 100 and the operating method of the boiler system 100 according to this embodiment, a mixture of solid fuel and additives is supplied to the furnace 112 so as to satisfy the above conditions (A), (B), and (C). This allows the following reaction formulas (1) and (2) to proceed in the gas phase of the furnace 112. ２ O ３ 2SiO ２ + 2KCl + H ２ O → K ２ O.Al ２ O ３ 2SiO ２ + 2HCl...Reaction formula (1) 2KCl + SO ２ + (1 / 2O ２ ) + H ２ O → K ２ O ４ +2HCl ... Reaction formula (2) Therefore, the boiler system 100 can convert alkali chloride (KCl), which causes corrosion of the inner wall and piping of the furnace 112, into hydrogen chloride (HCl). This allows the boiler system 100 to suppress corrosion of the inner wall and piping of the furnace 112. As described above, the hydrogen chloride produced by the progress of reaction formulas (1) and (2) is removed by the desulfurization device 130.
[0055] Furthermore, as described above, the boiler system 100 mixes the solid fuel and the additive in the bunker 250 so as to satisfy the above conditions (A), (B), and (C). This allows the boiler system 100 to suppress adhesion of combustion ash to the inner wall of the furnace 112 and corrosion caused by the combustion ash more effectively than the comparative example in which the solid fuel and the additive are supplied to the furnace 112 through separate ports. Specifically, in the comparative example, depending on the flow conditions inside the furnace 112, the locations where silica, alumina, and sulfur flow may be limited, resulting in uneven locations where adhesion of combustion ash and corrosion caused by the combustion ash can be reduced. In contrast, the boiler system 100 can supply the solid fuel and the additive to the furnace 112 in a substantially uniformly mixed state. This allows the boiler system 100 to flow silica, alumina, and sulfur evenly within the furnace 112, thereby suppressing adhesion of combustion ash to the inner wall of the furnace 112 and corrosion caused by the combustion ash.
[0056] Furthermore, the boiler system 100 supplies the mixture of solid fuel and additive to the furnace 112 so as to satisfy the above conditions (A) and (C). This makes it possible for the boiler system 100 to suppress adhesion of combustion ash to the inner wall of the furnace 112 and corrosion caused by the combustion ash, regardless of the type of biomass, the place of origin, and other properties of the biomass.
[0057] Furthermore, the boiler system 100 supplies the mixture of solid fuel and additives to the furnace 112 so as to satisfy the above condition (A). That is, the boiler system 100 adjusts the concentrations of silica and alumina contained in the combustion ash. The amount of combustion ash per unit volume varies depending on the type of solid fuel. Therefore, compared to the comparative example in which the concentrations of silica and alumina contained in the solid fuel are adjusted, the boiler system 100 can avoid a situation in which excessive silica and alumina are contained in the combustion ash.
[0058] As described above, the boiler system 100 supplies biomass as a solid fuel to the furnace 112. Therefore, the boiler system 100 reduces CO emissions by 20% compared to when only coal or biomass is supplied to the furnace 112. ２Emissions can be reduced.
[0059] Furthermore, as described above, the boiler system 100 uses, as an additive, the combustion ash collected by the dust removal device 124. This allows the boiler system 100 to reduce the cost required for the additive.
[0060] Conventionally, the combustion ash collected by the dust collector 124 has been disposed of in landfills. In contrast, the boiler system 100 uses at least a portion of the combustion ash collected by the dust collector 124 as an additive. Therefore, the boiler system 100 can reduce the cost required for disposing of the combustion ash in landfills.
[0061] Furthermore, the boiler system 100 uses at least a portion of the combustion ash collected by the dust collector 124 as an additive, thereby stabilizing the properties of the combustion ash. Therefore, the boiler system 100 can use the combustion ash collected by the dust collector 124 that has not been used as an additive as a concrete raw material or fertilizer.
[0062] The boiler system 100 also includes a cleaning unit 144. This makes it possible to remove alkali metals and alkaline earth metals from the combustion ash collected by the dust collector 124. Therefore, by using the cleaned combustion ash as an additive, the boiler system 100 can avoid a situation in which the melting point of the combustion ash increases.
[0063] [Example] Solid fuel was burned in a combustion furnace equipped with a simulated water tube inside, the metal temperature of which was controlled at 650°C. Then, chloride ions (Cl － ) concentration was measured.
[0064] Fig. 4 is a diagram illustrating the relationship between aluminosilicate and chloride ions contained in combustion ash. In Fig. 4, the horizontal axis represents the concentration [wt%] of aluminosilicate contained in combustion ash. In Fig. 4, the vertical axis represents the concentration [mmol / kg] of chloride ions contained in combustion ash.
[0065] As shown in Figure 4, the concentration of chloride ions in the combustion ash decreases as the amount of aluminosilicate in the combustion ash increases. Furthermore, when the amount of aluminosilicate is in the range of more than 0 wt% and less than 40 wt%, the concentration of chloride ions decreases more rapidly as the amount of aluminosilicate increases. On the other hand, when the amount of aluminosilicate is in the range of 40 wt% to 75 wt%, the decrease in the concentration of chloride ions with increasing amount of aluminosilicate is gradual.
[0066] From the above results, it was confirmed that by achieving condition (A), i.e., by setting the concentration of silica and alumina contained in the combustion ash after combustion to 40 wt% or more and 100 wt% or less, the boiler system 100 can efficiently reduce the concentration of chloride ions.
[0067] Fig. 5 is a diagram illustrating the relationship between sulfur and chloride ions contained in the entire solid fuel. In Fig. 5, the horizontal axis represents the sulfur concentration [mmol / kg] contained in the entire solid fuel. In Fig. 5, the vertical axis represents the chloride ion concentration [mmol / kg] contained in the combustion ash.
[0068] As shown in Figure 5, the concentration of chloride ions in the combustion ash decreases as the amount of sulfur contained in the entire solid fuel increases. Furthermore, when the amount of sulfur is in the range of more than 0 mmol / kg and less than 20 mmol / kg, the concentration of chloride ions decreases rapidly as the amount of sulfur increases. On the other hand, when the amount of sulfur is in the range of 20 mmol / kg or more and 60 mmol / kg or less, the decrease in the concentration of chloride ions with increasing amount of sulfur is gradual.
[0069] From the above results, it was confirmed that by satisfying condition (B), i.e., by setting the sulfur concentration contained in the entire solid fuel to 20 mmol / kg or more and 781 mmol / kg (2.5 wt%), the boiler system 100 can efficiently reduce the concentration of chloride ions.
[0070] Fig. 6 is a diagram illustrating the relationship between calcium and chloride ions contained in combustion ash. In Fig. 6, the horizontal axis represents the concentration [wt%] of calcium (CaO, which is the equivalent value of calcium oxide) contained in combustion ash. In Fig. 6, the vertical axis represents the concentration [mmol / kg] of chloride ions contained in combustion ash.
[0071] As shown in Figure 6, when the amount of calcium contained in the combustion ash is in the range of more than 0 wt% and not more than 50 wt%, the concentration of chloride ions contained in the combustion ash increases as the amount of calcium increases. Furthermore, when the amount of calcium is in the range of more than 0 wt% and not more than 20 wt%, the concentration of chloride ions increases slightly as the amount of calcium increases. When the amount of calcium is in the range of more than 20 wt% and not more than 30 wt%, the concentration of chloride ions increases rapidly as the amount of calcium increases. Furthermore, when the amount of calcium is in the range of more than 30 wt% and not more than 35 wt%, the concentration of chloride ions increases rapidly as the amount of calcium increases. When the amount of calcium is in the range of more than 35 wt% and not more than 40 wt%, the concentration of chloride ions increases slightly as the amount of calcium increases. When the amount of calcium is in the range of more than 40 wt% and not more than 50 wt%, the increase in the concentration of chloride ions with an increase in the amount of calcium is gradual.
[0072] On the other hand, when the amount of calcium is in the range of more than 50 wt % to 65 wt % or less, the concentration of chloride ions decreases slightly as the amount of calcium increases.
[0073] From the above results, it was confirmed that by achieving condition (C), i.e., by setting the concentration of calcium contained in the combustion ash after combustion to more than 0 wt % and not more than 30 wt %, the boiler system 100 can efficiently reduce the concentration of chloride ions.
[0074] Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.
[0075] For example, in the above embodiment, the boiler system 100 is illustrated as having two fuel storage sections (the first fuel storage section 210 and the second fuel storage section 212). However, the boiler system 100 may have three or more fuel storage sections. Also, the boiler system 100 is illustrated as having the first fuel storage section 210 for storing biomass and the second fuel storage section 212 for storing coal. However, the boiler system 100 may have multiple fuel storage sections that respectively store different types of solid fuels selected from multiple types of biomass. Alternatively, the boiler system 100 may have multiple fuel storage sections that respectively store different types of solid fuels selected from one or more types of biomass and one or more types of coal. Note that the fuel storage sections may store solid fuels that have been cut to a predetermined size or coarsely pulverized in advance.
[0076] For example, the fuel storage unit may include a fuel storage unit for storing either woody biomass (including bark and rice husks) or herbaceous biomass washed with water, and a fuel storage unit for storing waste biomass. Woody biomass (including bark and rice husks) and herbaceous biomass washed with water contain larger amounts of silica, alumina, and sulfur than waste biomass.
[0077] In the above embodiment, the boiler system 100 includes the additive storage unit 214. However, the boiler system 100 does not necessarily have to include the additive storage unit 214.
[0078] In the above embodiment, the boiler system 100 is exemplified as having a configuration including the cleaning unit 144. However, the boiler system 100 does not have to have the cleaning unit 144. In this case, the combustion ash collected by the dust collector 124 is used as an additive as is. In this case, the boiler system 100 can reduce the cost required for the additive. Furthermore, the boiler system 100 can reduce the cost required for landfilling the combustion ash. Furthermore, the boiler system 100 can stabilize the properties of the combustion ash.
[0079] In the above embodiment, the boiler system 100 uses the combustion ash collected by the dust collector 124 as the additive. However, the additive may contain at least silica and alumina. For example, the additive may be kaolinite, or may be combustion ash from either or both of coal and biomass.
[0080] When coal combustion ash (coal ash) is used as the additive, coal ash deposited at the bottom of the furnace from other coal-fired boiler systems may be used. By using coal ash deposited at the bottom of the furnace, it is possible to prevent heavy metals and trace elements from being mixed into the combustion ash generated in the boiler system 100. Examples of heavy metals include mercury (Hg), selenium (Se), arsenic (As), cadmium (Cd), and lead (Pb). Examples of trace elements include fluorine (F), boron (B), and iodine (I).
[0081] Furthermore, when biomass combustion ash (biomass ash) is used as the additive, the biomass ash may be washed with water before use, which can prevent a decrease in the melting point of the combustion ash generated in the boiler system 100.
[0082] In the above embodiment, an example has been given in which multiple types of solid fuels and additives are mixed in the bunker 250. However, multiple types of solid fuels and additives may each be supplied independently to the furnace 112. For example, multiple types of solid fuels may be supplied to the bunker 250, and the additives may be supplied between the mill 252 and the furnace 112. Alternatively, multiple types of solid fuels may be supplied to the bunker 250, and the additives may be supplied from a secondary air supply port of the furnace 112.
[0083] In the above embodiment, the fuel supply unit 220 supplies the mixture of solid fuel and additives to the furnace 112 so as to satisfy all of the above conditions (A), (B), and (C). However, the fuel supply unit 220 may supply the mixture of solid fuel and additives to the furnace 112 so as to satisfy at least condition (C). This allows the fuel supply unit 220 to increase the melting point of the combustion ash.
[0084] In the above embodiment, the fuel control unit 260 simultaneously controls the apertures of the first valve 240, the second valve 242, and the third valve 244. However, the fuel control unit 260 may exclusively control the apertures of the first valve 240, the second valve 242, and the third valve 244. For example, the first valve 240, the second valve 242, and the third valve 244 may be configured as on-off valves, and the fuel control unit 260 may exclusively control the on-off of the first valve 240, the second valve 242, and the third valve 244 so that the solid fuel and additive in the bunker 250 satisfy the above conditions (A), (B), and (C).
[0085] In the above embodiment, the boiler system 100 includes the fuel supply unit 220 that supplies a mixture of solid fuel and additives to the furnace 112 so as to satisfy all of the above conditions (A), (B), and (C). However, the boiler system may include a fuel supply unit that supplies the combustion ash cleaned by the cleaning unit 144 and biomass to the furnace 112, instead of the fuel supply unit 220. That is, the boiler system may include a dust remover 124 that recovers combustion ash from the combustion exhaust gas exhausted from the furnace 112, a heat exchanger 142 that exchanges heat between the combustion exhaust gas exhausted from the furnace 112 and water, a cleaning unit 144 that cleans the combustion ash with the water heat exchanged by the heat exchanger 142, and a fuel supply unit that supplies the combustion ash cleaned by the cleaning unit 144 and biomass to the furnace 112. This allows the boiler system to reduce the cost of additives. Furthermore, the boiler system can reduce the cost required for landfilling combustion ash, and can stabilize the properties of combustion ash.
[0086] The present disclosure can contribute, for example, to Sustainable Development Goal (SDG) Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy" and Goal 13 "Take urgent action to combat climate change and its impacts."
[0087] 100: Boiler system 112: Furnace 124: Dust removal device 142: Heat exchanger 144: Cleaning section 210: First fuel storage section (fuel storage section) 212: Second fuel storage section (fuel storage section) 214: Additive storage section 220: Fuel supply section
Claims
1. A boiler system comprising: a plurality of fuel storage units each storing a different type of solid fuel selected from a plurality of types of biomass, or a different type of solid fuel selected from one or more types of biomass and one or more types of coal; and a fuel supply unit that supplies the solid fuel from each of the plurality of fuel storage units to a furnace so that the calcium concentration in combustion ash after combustion is 30 mass% or less.
2. A boiler system as described in claim 1, wherein the fuel supply unit controls the amount of solid fuel supplied to the furnace from each of the multiple fuel storage units so that the sulfur concentration contained in the entire solid fuel supplied to the furnace is 20 mmol / kg or more.
3. A boiler system as described in claim 1 or 2, wherein the fuel supply unit controls the amount of solid fuel supplied from each of the multiple fuel storage units to the furnace so that the concentration of silica and alumina contained in the combustion ash is 40 mass% or more.
4. A boiler system as described in claim 3, further comprising an additive storage section for storing an additive containing at least silica and alumina, and the fuel supply section supplies the additive to the furnace in addition to the solid fuel.
5. The boiler system according to claim 4, wherein the additive is combustion ash of either or both of coal and biomass.
6. A boiler system according to claim 4 or 5, further comprising a dust removal device that recovers combustion ash from the combustion exhaust gas discharged from the furnace, and the additive is the combustion ash recovered by the dust removal device.
7. A boiler system as described in claim 6, comprising: a heat exchanger that exchanges heat between the combustion exhaust gas discharged from the furnace and water; and a cleaning section that cleans the combustion ash with the water that has been heat exchanged by the heat exchanger, wherein the additive is the combustion ash after being cleaned by the cleaning section.
8. A boiler system comprising: a dust removal device that recovers combustion ash from combustion exhaust gas discharged from a furnace; a heat exchanger that exchanges heat between the combustion exhaust gas discharged from the furnace and water; a cleaning unit that cleans the combustion ash with the water that has been heat exchanged by the heat exchanger; and a fuel supply unit that supplies the combustion ash after being cleaned by the cleaning unit and biomass to the furnace.
9. A method for operating a boiler system having multiple fuel storage sections, each storing a different type of solid fuel selected from multiple types of biomass, or each storing a different type of solid fuel selected from one or more types of biomass and one or more types of coal, wherein the solid fuel is supplied from each of the multiple fuel storage sections to a furnace so that the calcium concentration in the combustion ash after combustion is 30 mass% or less.