Additive supply amount control system, combustion equipment, and additive supply amount control method

Abstract

To provide an additive supply amount control system capable of suppressing corrosion caused by phosphate with a small amount of an additive.SOLUTION: An additive supply amount control system for a combustion furnace for burning fuel containing phosphorus includes: a detection unit for detecting at least one of a content amount of aluminum and a content amount of calcium in ash, and a content amount of phosphorus in the ash by analyzing the fuel or the ash generated by combustion of the fuel; and an additive amount control unit for controlling an addition amount of an additive containing at least one of alkali metal and alkali earth metal to be added to the fuel. The additive amount control unit controls the addition amount of the additive on the basis of a value obtained by subtracting at least one of a value in correspondence with the content amount of the aluminum in the ash and the content amount of the calcium in the ash from a value in correspondence with the content amount of the phosphorus in the ash.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to an additive supply amount control system, a combustion facility, and an additive supply amount control method. [Background technology]

[0002] Patent Document 1 describes a method for incinerating sewage sludge containing phosphorus using an incinerator. In this method, to solve the problem of combustion ash adhering to and accumulating in the exhaust gas passage on the outlet side of the combustion furnace, causing clogging, damage, or breakage of the exhaust gas passage, the composition of the dewatered sludge incinerated in the incinerator is adjusted by additives so that the value of Y, which is calculated by the following formula (h) from the content of Na, K, Ca, Mg, Al, Fe and P in the dewatered sludge supplied to the incinerator, is 1 or more. This suppresses the formation of phosphorus compounds that easily melt in the temperature range of 840 to 900°C, making it difficult for sintered ash to melt and thus reducing the problem of its adhesion and accumulation. Y={Na(mol)+K(mol)+Ca(mol×2)+Mg(mol×2)+Al(mol×3)+Fe(mol×3) / P(mol×3) ···(h) [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-120104 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, when burning phosphorus-containing fuel in an incinerator, corrosion caused by phosphates is likely to occur on the furnace walls of the incinerator and structures downstream of the incinerator (for example, the flow path walls of the exhaust gas passage and heat exchangers within the exhaust gas passage). In this regard, Patent Document 1 does not disclose any knowledge on how to suppress corrosion caused by phosphates with a small amount of additive.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an additive supply amount control system capable of suppressing corrosion caused by phosphate with a small amount of additives, a combustion facility including the same, and an additive supply amount control method.

Means for Solving the Problems

[0006] To achieve the above object, an additive supply amount control system according to at least one embodiment of the present disclosure is an additive supply amount control system for a combustion furnace for burning a fuel containing phosphorus, a detection unit configured to detect at least one of the content of aluminum and the content of calcium in the ash and the content of phosphorus in the ash by analyzing the ash generated by the combustion of the fuel or the fuel; an addition amount control unit configured to control the addition amount of an additive containing at least one of an alkali metal and an alkaline earth metal added to the fuel; and includes The addition amount control unit is configured to control the addition amount of the additive based on a value obtained by subtracting at least one of a value corresponding to the content of aluminum in the ash and a value corresponding to the content of calcium in the ash from a value corresponding to the content of phosphorus in the ash.

[0007] To achieve the above object, a combustion facility according to at least one embodiment of the present disclosure is the additive supply amount control system; the combustion furnace; and includes

[0008] To achieve the above object, an additive supply amount control method according to at least one embodiment of the present disclosure is an additive supply amount control method for a combustion furnace for burning a fuel containing phosphorus, A detection step of detecting at least one of the content of aluminum and the content of calcium in the ash and the content of phosphorus in the ash by analyzing the ash generated by the combustion of the fuel or the fuel; An additive amount control step of controlling the additive amount of adding an additive containing at least one of an alkali metal and an alkaline earth metal to the fuel; comprising; In the additive amount control step, the additive amount is controlled based on a value obtained by subtracting at least one of a value corresponding to the content of aluminum in the ash and a value corresponding to the content of calcium in the ash from a value corresponding to the content of phosphorus in the ash.

Advantages of the Invention

[0009] According to at least one embodiment of the present disclosure, there are provided an additive supply amount control system capable of suppressing corrosion caused by phosphate with a small amount of additive, a combustion facility provided with the same, and an additive supply amount control method.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram of a combustion facility 1 including an additive supply amount control system 50 according to an embodiment. [Figure 2] It is a diagram showing an example of the hardware configuration of an additive amount control unit 40 in FIG. 1. [Figure 3] It is a diagram showing the corrosion amount of each of NaPO3-NaCl, NaPO3-Na2SO4, NaPO3-KPO3, and NaCl-KCl-Na2SO4-K2SO4 under the conditions described in the figure. [Figure 4] It is a diagram showing a curve C showing the relationship between the composition of the molten salt and the corrosion amount and the corrosion amounts of (a) NaPO3-NaCl, (b) NaPO3-Na2SO4, and (d) NaCl-KCl-Na2SO4-K2SO4. [Figure 5] It is a diagram showing the relationship between the solubility of Cr2O3 in the molten salt NaCl-KCl-Na2SO4-K2SO4 and the basicity. [Figure 6] This figure shows the relationship between the Na2O / P2O5 (molar ratio) and the Na2O activity in the molten salt. [Figure 7] This is a diagram illustrating the state of the NaPO3-KPO3-Na3PO4-K3PO4 system. [Figure 8] This figure shows the results of verifying the adhesion properties of the ash when the above value X is changed by varying the content of each of Al2O3, CaO, P2O5, Na2O, and K2O in the ash. [Figure 9] This is a schematic diagram of a combustion facility 1 including an additive supply amount control system 50 according to another embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of the invention, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.

[0012] Figure 1 is a schematic diagram of a combustion facility 1 including an additive supply amount control system 50 according to one embodiment. Figure 2 is a diagram showing an example of the hardware configuration of the additive amount control unit 40 in Figure 1.

[0013] As shown in Figure 1, the combustion equipment 1 comprises a combustion furnace 12 for burning fuel internally, a flue 4 through which combustion gases from the combustion furnace 12 are guided, heat transfer tubes 14 provided in the flue 4, a capture unit 18 provided downstream of the heat transfer tubes 14 in the flue 4, and an additive supply amount control system 50 for controlling the amount of additives supplied to the fuel. The combustion furnace 12, flue 4, and heat transfer tubes 14 constitute the boiler 2, and each of the combustion furnace 12, flue 4, and heat transfer tubes 14 is made of heat-resistant steel containing chromium, nickel, etc.

[0014] The combustion furnace 12 is supplied with fuel from the fuel supply unit 8 and air from the air supply unit 10, and is configured to burn the fuel inside the combustion furnace 12. The fuel supplied from the fuel supply unit 8 is a phosphorus-containing fuel, such as biomass fuel represented by PKS (Palm Kernel Shell), rubber trees, chicken manure, or sludge. If a biomass fuel that is difficult to burn on its own (dedicated combustion) is used, the fuel supplied to the combustion furnace 12 may include auxiliary fuels such as natural gas in addition to the biomass fuel.

[0015] In the combustion furnace 12, combustion gases and ash are generated by the combustion of fuel. Some of the ash accumulates at the bottom of the combustion furnace 12 and is discharged to the outside of the combustion furnace 12 through an ash discharge section (not shown). In addition, some of the ash is carried along with the combustion gases as fly ash and guided to the flue 4. The combustion temperature of the combustion furnace 12 may be less than 900°C (for example, 800°C or more and less than 900°C).

[0016] The heat transfer tube 14 is configured to heat the fluid (such as water) flowing inside it by exchanging heat with the high-temperature combustion gas flowing through the flue. The water heated in the heat transfer tube 14 may be used, for example, as steam to drive a power generation turbine.

[0017] As shown in Figure 1, a de-cooling section 16 may be provided downstream of the heat transfer tube 14 in the flue 4 to lower the temperature of the combustion gas flowing through the flue 4. The de-cooling section 16 may be configured to lower the temperature of the combustion gas by, for example, spraying water. The de-cooling section 16 may be configured to lower the temperature of the combustion gas after it has passed through the heat transfer tube 14 to a temperature range in which the synthesis of a predetermined substance (e.g., dioxins) does not proceed.

[0018] The capture unit 18 is configured to capture ash (fly ash) carried along with the combustion gas from the flue 4. In other words, the capture unit 18 separates the ash from the combustion gas that carries it. For example, a dust collection device such as a bag filter or an electrostatic dust collector can be used as the capture unit 18.

[0019] The combustion gas from which ash has been removed in the capture unit 18 is discharged to the outside of the combustion equipment 1 via the exhaust passage 5 and chimney 6 connected to the capture unit 18. A fan 22 may be provided in the exhaust passage 5 to draw in the combustion gas. Furthermore, the ash separated from the combustion gas in the capture unit 18 is discharged from the capture unit 18 via the discharge pipe 20 and discharge valve 21.

[0020] The additive supply control system 50 will be described in more detail below. As shown in Figure 1, an additive supply amount control system 50 according to one embodiment includes an additive supply unit 28 for supplying an additive containing at least one of alkali metals and alkaline earth metals to fuel before or during combustion, a detection unit 26 for measuring components in ash, and an additive amount control unit 40 for controlling the amount of additive added to the fuel.

[0021] As shown in Figure 2, the additive amount control unit 40 is configured using a computer that includes, for example, a processor 72, RAM (Random Access Memory) 74, ROM (Read Only Memory) 76, HDD (Hard Disk Drive) 78, input I / F 80, and output I / F 82, all of which are connected to each other via a bus 84. The hardware configuration of the additive amount control unit 40 is not limited to the above and may be configured as a combination of a control circuit and a storage device. The additive amount control unit 40 is also configured by a computer executing programs that realize each function of the additive amount control unit. The functions of each part of the additive amount control unit 40 described below are realized, for example, by loading a program held in ROM 76 into RAM 74 and executing it with the processor 72, as well as by reading and writing data to RAM 74 and ROM 76. The hardware constituting the additive amount control unit 40 may be centralized in one location or distributed across multiple locations.

[0022] In the exemplary embodiment shown in Figure 1, the additive supply unit 28 includes an additive supply line 29 for supplying additives to the fuel, a tank 30 connected to the additive supply line 29 for storing the additives, a supply pump 32 for pressurizing and supplying the additives from the tank 30, and a supply valve 34 for adjusting the amount of additive supplied.

[0023] In some embodiments, the additive supply unit 28 is configured to supply additives to the fuel before combustion. For example, the additive supply unit 28 may be configured to supply additives to a fuel supply unit 8 (hopper, etc.) where the fuel is stored before being supplied to the combustion furnace 12. Alternatively, in some embodiments, the additive supply unit 28 may be configured to supply additives from above the fuel inside the combustion furnace 12.

[0024] The additive may contain one or more of the following: sodium carbonate, potassium carbonate, calcium carbonate, and magnesium carbonate. The following explanation will use the case where the additive contains sodium carbonate and potassium carbonate as an example. If the additive contains two or more compounds from among sodium carbonate, potassium carbonate, calcium carbonate, and magnesium carbonate, each compound may be supplied to the fuel separately, or the two or more compounds may be mixed before being supplied to the fuel.

[0025] The detection unit 26 is configured to analyze the properties of the ash generated by the combustion of the fuel, for example using an XRF (X-ray fluorescence analyzer), and to detect the respective content of sodium, potassium, phosphorus, calcium, and aluminum in the ash. In the exemplary embodiment shown in Figure 1, the detection unit 26 is configured to detect the respective content of sodium, potassium, phosphorus, calcium, and aluminum in the ash captured by the capture unit 18. The detection unit 26 may, for example, collect the ash to be analyzed via a discharge pipe 20 through which the ash is discharged from the capture unit 18.

[0026] The additive amount control unit 40 is configured to control the amount of additive added to the fuel by the additive supply unit 28 based on the detection results from the detection unit 26. Specifically, the additive amount control unit 40 controls the amount of additive added to the fuel by the additive supply unit 28 based on the respective content of sodium, potassium, phosphorus, calcium, and aluminum in the ash detected by the detection unit 26. In the exemplary embodiment shown in Figure 1, the additive amount control unit 40 controls the amount of additive added to the fuel by controlling the opening degree of the supply valve 34.

[0027] Here, the number of moles of sodium, potassium, phosphorus, calcium, and aluminum contained per unit weight of ash, calculated from the detection results of the detection unit 26, is given by m Na、 m K、 m P、 m Ca、 m AlThen, the addition amount control unit 40 controls the addition amount of the additive to the fuel so that the value X defined by the following formula (1) is greater than 1. X=(m Na +m K ) / (m P -0.6×m Ca -m Al ) ···(1)

[0028] That is, the addition amount control unit 40 calculates, from the detection result of the detection unit 26, the number of moles m Na、 m K、 m P、 m Ca、 m Al of each of sodium, potassium, phosphorus, calcium, and aluminum contained per unit weight of ash, and based on these, calculates the numerator (m Na +m K ) and the denominator (m P -0.6×m Ca -m Al ) of the above formula (1) respectively, and calculates the above value X by dividing the numerator (m Na +m K ) by the denominator (m P -0.6×m Ca -m Al ), and controls the addition amount of the additive to the fuel so that X is greater than 1. That is, the addition amount control unit 40 divides the sum of m Na and m K by the value obtained by subtracting the value obtained by multiplying m Ca by 0.6 and m Al from m P ) to calculate the value X, and controls the addition amount of the additive to the fuel so that X is greater than 1. For example, when X is 1 or less, the addition amount control unit 40 may increase the addition amount of the additive per unit weight of the fuel, and for example, when X is 3 or more, the addition amount control unit 40 may decrease the addition amount of the additive per unit weight of the fuel.

[0029] Hereinafter, the technical significance of making the value X defined by the above formula (1) greater than 1 will be described. As a result of diligent research by the inventors of the present invention, analysis of ash discharged from a stably operated combustion furnace 12 in the combustion equipment 1 illustrated in Figure 1 was performed using XRD (X-ray diffraction). The phosphate compounds discharged from the combustion furnace 12 contained AlPO4 and Ca5(PO4)3(OH), while sodium and potassium phosphate compounds were not detected. The inventors of the present invention investigated using chemical thermodynamic calculations and calculated that the phosphorus contained in the fuel that was not used to produce AlPO4 and Ca5(PO4)3(OH) (hereinafter referred to as "remaining phosphorus") exists as a sodium / potassium solid solution (a solid of Na / K / P / O of any composition that is not detected by XRD and is not identified as a compound).

[0030] In other words, when the combustion furnace 12 is operating stably, AlPO4 and Ca5(PO4)3(OH) are preferentially produced over alkali metal salts of phosphoric acid, and the amount of the remaining phosphorus is the denominator of the right side of equation (1) above, i.e., (m P -0.6 × m Ca -m Al It is represented by ). Furthermore, the remaining phosphorus is thought to exist as a solid solution of sodium phosphate / potassium phosphate.

[0031] Furthermore, as a result of diligent research by the inventors of this application, it has become clear that, with respect to the remaining phosphorus, the above-mentioned corrosion caused by phosphates can be effectively suppressed by making the sum of the molar ratio of Na2O to P2O5 in the molten salt (=Na2O / P2O5) and the molar ratio of K2O to P2O5 in the molten salt (=K2O / P2O5) greater than 1, that is, by making the above value X greater than 1.

[0032] Figure 3 shows the amount of corrosion of the material (25Cr steel) by each of the molten salts (a) NaPO3-NaCl, (b) NaPO3-Na2SO4, (c) NaPO3-KPO3, and (d) NaCl-KCl-Na2SO4-K2SO4 under the specified conditions described in the upper right of Figure 3. The specified conditions here are a temperature of 600°C, a gas composition of nitrogen-based with an oxygen concentration of 3%, a test time of 50 hours, and the material to be corroded is 25Cr steel. Figure 4 shows the amount of corrosion of the material (25Cr steel) by each of the molten salts (a), (b), and (d) described above, along with curve C which shows the relationship between the composition of the molten salt and the amount of corrosion of the material (25Cr steel).

[0033] As shown in Figure 3, the corrosion amounts for (b) NaPO3-Na2SO4, (c) NaPO3-KPO3, and (d) NaCl-KCl-Na2SO4-K2SO4 are significantly suppressed compared to the corrosion amount for (a) NaPO3-NaCl. When the sum of the molar ratio of Na2O to P2O5 in the molten salt (=Na2O / P2O5) and the molar ratio of K2O to P2O5 in the molten salt (=K2O / P2O5) is 1 (i.e., in the case of (c) above), the corrosion amount is significantly suppressed. Furthermore, in Figure 4, curve C shows that the corrosion amount changes depending on the ratio (weight %) of SO4 content to the total SO4 content and Cl content in the molten salt. The corrosion amounts for (a) NaPO3-NaCl, (b) NaPO3-Na2SO4, and (d) NaCl-KCl-Na2SO4-K2SO4 all closely coincide with curve C.

[0034] Therefore, the amount of corrosion in each of (a) to (d) above corresponds to the ratio of the SO4 content to the total SO4 and Cl content in the molten salt, and the influence of phosphorus content on each amount of corrosion is negligibly small.

[0035] Furthermore, as illustrated in Figure 5, the basicity of the molten salt is Na2O > 10 -10It is known that in the range satisfying [condition], active dissolution occurs, resulting in severe corrosion by molten salts. However, in the case of phosphates, when the molar ratio of Na₂O to P₂O₅ in the molten salt (=Na₂O / P₂O₅) is 1 or more and less than 3, the activity of Na₂O in the molten salt (corresponding to about -23 to -14 in Fig. 6) results in limited corrosion by the molten salt. For example, even when the metal temperature is 700°C, Na₂O < 10 -10 is satisfied.

[0036] Therefore, the additive amount control unit 40 controls the additive amount of the additive to the fuel so that the value X defined by the above formula (1) is greater than 1, thereby suppressing the corrosiveness and corrosion acceleration of phosphoric acid itself, and effectively suppressing the corrosion caused by phosphates. Also, the additive amount control unit 40 can effectively suppress the corrosion caused by phosphates with a small amount of additive by controlling the additive amount of the additive to the fuel so that 1 < X < 3 is satisfied.

[0037] Fig. 7 is a phase diagram of the NaPO₃-KPO₃-Na₃PO₄-K₃PO₄ system. In Fig. 7, the calculated results of the melting points of phosphoric acid compounds are shown when the equivalent fraction of K content divided by the sum of Na content and K content, that is, K / (Na + K), is taken as the horizontal axis, and the equivalent fraction of P₂O₅ / (Na₂O + K₂O) is taken as the vertical axis.

[0038] As shown in Figure 7, by satisfying X ≥ 2.6 for the value X defined by the above formula (1), the melting point of the phosphoric acid compound can be made to 900°C or higher. As a result, the ash becomes less likely to melt in the temperature range below 900°C. This makes it less likely for combustion ash to adhere to and accumulate in the exhaust gas flow path on the outlet side of the combustion furnace, thereby suppressing clogging, damage, or breakage of the exhaust gas flow path. Furthermore, by satisfying 2.6 ≤ X < 3, it is possible to make it less likely for combustion ash to adhere to the exhaust gas flow path on the outlet side of the combustion furnace with a smaller amount of additive than in the incineration treatment method described in Patent Document 1, thereby suppressing clogging, damage, or breakage of the exhaust gas flow path. For example, when X = 2.6 is satisfied, the amount (mol) of alkali metals (sodium and potassium in the above example) can be reduced to 2.6 / 3 times the molar amount of phosphorus compared to Patent Document 1.

[0039] Therefore, the additive amount control unit 40 controls the amount of additive added to the fuel so that 2.6 ≤ X < 3 for the value X defined by the above formula (1), thereby making it difficult for combustion ash to adhere to the exhaust gas flow path on the outlet side of the combustion furnace with a small amount of additive, and suppressing clogging, damage, or breakage of the exhaust gas flow path.

[0040] Figure 8 shows the results of verifying the adhesion properties of the ash when the above value X is changed by varying the content of each of Al2O3, CaO, P2O5, Na2O, and K2O in the ash. As shown in Figure 8, in Case 3 where X=1.1, ash adhesion is high, while in Case 1 where X=-1.7, Case 2 where X=-7.5, and Case 4 where X=8.3, ash adhesion is low.

[0041] Here, in case 3 where X=1.1, X is less than 2.6, so the melting point of the phosphate compound is lower than 900°C and the ash adheres well. In contrast, in case 4 where X=8.3, X is greater than or equal to 2.6, so the melting point of the phosphate compound is higher than 900°C and the ash adheres poorly.

[0042] Also, in Case 1 where X = -1.7 and Case 2 where X = -7.5, since the denominator of the above formula (1) is a negative value, it means that the remaining phosphorus does not exist, and in this case, the ash adhesion is also small.

[0043] Thus, in the case where 2.6 ≤ X is satisfied, it is possible to make it difficult for combustion ash to adhere to the exhaust gas flow path on the outlet side of the combustion furnace, and it is possible to suppress clogging, damage, or breakage of the exhaust gas flow path. In Case 3 where 1 < X < 3, although the ash adhesion is large, as described above, corrosion caused by phosphate can be suppressed with a small amount of additive.

[0044] In some embodiments, the addition amount control unit 40 may control the addition amount of the additive per unit weight of the fuel so that the melting point of the phosphate compound contained in the ash is higher than the combustion temperature of the combustion furnace by adjusting the value of X according to the combustion temperature of the combustion furnace. In this case, the addition amount control unit 40 may increase the value of X as the combustion temperature of the combustion furnace increases, and may increase the addition amount of the additive per unit weight of the fuel as the combustion temperature of the combustion furnace increases. Thereby, it is possible to make it difficult for combustion ash to adhere to the exhaust gas flow path on the outlet side of the combustion furnace, and it is possible to suppress clogging, damage, or breakage of the exhaust gas flow path.

[0045] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0046] For example, in the above-described embodiment, the detection unit 26 analyzes the properties of the ash generated by the combustion of the fuel by, for example, XRF (X-ray fluorescence analyzer). However, in other embodiments, as shown in FIG. 9, for example, the detection unit 26 may be configured to detect the content of each of sodium, potassium, phosphorus, calcium, and aluminum in the ash by analyzing the fuel before being supplied to the combustion furnace 12 by XRF or the like.

[0047] Further, when the fuel supplied to the combustion furnace 12 includes biomass fuel and auxiliary fuel such as natural gas, the addition amount control unit 40 controls the addition amount of the additive to the fuel so as to satisfy 1 < X < 3 (more preferably, 2.6 ≤ X < 3), and may be configured to control the biomass co - firing rate, which is the ratio of the biomass fuel in the fuel supplied to the combustion furnace 12.

[0048] Also, in the above - described embodiment, the detection unit 26 detects both the content of aluminum and the content of calcium in the ash. However, in other embodiments, the detection unit 26 may detect at least one of the content of aluminum and the content of calcium in the ash, and it is not necessary to detect either one of the content of aluminum and the content of calcium in the ash. In this case, the addition amount control unit subtracts at least one of a value corresponding to the content of aluminum in the ash (for example, the number of moles of aluminum contained per unit weight of the ash) and a value corresponding to the content of calcium in the ash (a value obtained by multiplying the number of moles of calcium contained per unit weight of the ash by 0.6) from a value corresponding to the content of phosphorus in the ash (for example, the number of moles of phosphorus contained per unit weight of the ash), and controls the addition amount of the additive to the fuel based on the obtained value.

[0049] The content described in each of the above embodiments can be understood as follows, for example.

[0050] [1] The additive supply amount control system according to at least one embodiment of the present disclosure (for example, the additive supply amount control system 50 described above) is an additive supply amount control system for a combustion furnace (for example, the combustion furnace 12 described above) for burning fuel containing phosphorus, a detection unit (for example, the detection unit 26 described above) configured to detect at least one of the content of aluminum and the content of calcium in the ash and the content of phosphorus in the ash by analyzing the ash generated by the combustion of the fuel or the fuel, An additive amount control unit (for example, the additive amount control unit 40 described above) is configured to control the amount of an additive containing at least one of alkali metals and alkaline earth metals added to the fuel, Equipped with, The additive amount control unit is configured to control the amount of the additive based on a value obtained by subtracting at least one of the following from a value corresponding to the phosphorus content in the ash (for example, the number of moles of aluminum per unit weight of ash) and a value corresponding to the calcium content in the ash (for example, the number of moles of calcium per unit weight of ash multiplied by 0.6) from a value corresponding to the phosphorus content in the ash (for example, the number of moles of phosphorus per unit weight of ash).

[0051] As a result of diligent research by the inventors of the present invention, analysis of ash discharged from a stably operated combustion furnace using XRD revealed that the phosphate compounds discharged from the combustion furnace included AlPO4 and Ca5(PO4)3(OH), while sodium and potassium phosphate compounds were not detected. Chemical thermodynamic calculations by the inventors of the present invention calculated that the phosphorus in the fuel that was not used to produce AlPO4 and Ca5(PO4)3(OH) (hereinafter referred to as "remaining phosphorus") exists as a sodium / potassium solid solution (a solid of Na / K / P / O of arbitrary composition that is not detected by XRD and therefore not identified as a compound).

[0052] In other words, when the combustion furnace is operating stably, AlPO4 and Ca5(PO4)3(OH) are preferentially produced over alkali metal salts of phosphoric acid, and the remaining phosphorus is thought to exist as sodium phosphate / potassium phosphate salts. Furthermore, it was revealed that if an appropriate amount of alkali metal is supplied to the combustion furnace for the remaining phosphorus, the corrosiveness and corrosion acceleration of phosphoric acid in the molten salt can be suppressed.

[0053] The additive supply control system described in [1] above is based on these findings and controls the amount of additive containing at least one of an alkali metal and an alkaline earth metal based on a value obtained by subtracting at least one of the values ​​corresponding to the aluminum content in the ash and the calcium content in the ash from a value corresponding to the phosphorus content in the ash, thereby suppressing corrosion caused by phosphates with a small amount of additive.

[0054] [2] In some embodiments, in the additive supply amount control system described in [1] above, The additive amount control unit is configured to control the amount of the additive based on a value obtained by subtracting both the value corresponding to the content of aluminum in the ash and the value corresponding to the content of calcium in the ash from the value corresponding to the content of phosphorus in the ash.

[0055] The additive supply control system described in [2] above is based on the findings described in [1] above, and controls the amount of additive containing at least one of alkali metals and alkaline earth metals based on a value obtained by subtracting both the value corresponding to the aluminum content in the ash and the value corresponding to the calcium content in the ash from the value corresponding to the phosphorus content in the ash, thereby suppressing corrosion caused by phosphates with a small amount of additive.

[0056] [3] In some embodiments, in the additive supply amount control system described in [2] above, The detection unit is configured to further detect the sodium and potassium content in the ash by analyzing the ash or the fuel generated by the combustion of the fuel. The number of moles of sodium, potassium, phosphorus, calcium, and aluminum contained per unit weight of the ash is, respectively, m Na、 m K、 m P、 m Ca、 m Al So, The additive amount control unit is configured to control the amount of additive added based on the detection result of the detection unit, such that the value X defined by the following formula (1) becomes greater than 1. X=(m Na +m K ) / (m P -0.6 × m Ca -m Al ) ···(1)

[0057] According to the additive supply control system described in [3] above, by controlling the amount of additive added so that the above value X is greater than 1, corrosion caused by phosphates can be effectively suppressed with a small amount of additive.

[0058] [4] In some embodiments, in the additive supply amount control system described in [3] above, The additive amount control unit is configured to control the amount of additive added based on the detection result of the detection unit, so that the value X becomes 2.6 or greater.

[0059] According to the additive supply control system described in [4] above, by controlling the amount of additive added so that the above value X is 2.6 or higher, the melting point of the phosphate compound contained in the ash can be raised to 900°C or higher. As a result, the ash becomes less likely to melt in the temperature range below 900°C. This makes it less likely for combustion ash to adhere to and accumulate in the exhaust gas flow path on the outlet side of the combustion furnace, and effectively suppresses clogging, damage, or breakage of the exhaust gas flow path.

[0060] [5] In some embodiments, in the additive supply amount control system described in [3] or [4] above, The additive amount control unit is configured to control the amount of additive added based on the detection result of the detection unit, so that the value X becomes less than 3.

[0061] According to the additive supply control system described in [5] above, corrosion caused by phosphates can be effectively suppressed with a small amount of additive, and / or combustion ash can be less likely to adhere to and accumulate in the exhaust gas flow path on the outlet side of the combustion furnace with a small amount of additive. Therefore, corrosion caused by phosphates can be effectively suppressed with a small amount of additive, and / or clogging, damage, or breakage of the exhaust gas flow path can be effectively suppressed with a small amount of additive.

[0062] [6] A combustion apparatus according to at least one embodiment of the present disclosure (e.g., the combustion apparatus 1 described above) An additive supply amount control system as described in any of [1] to [5] above, The aforementioned combustion furnace, It is equipped with.

[0063] According to the combustion equipment described in [6] above, since it is equipped with an additive supply amount control system as described in any of [1] to [5] above, corrosion caused by phosphates can be suppressed with a small amount of additive.

[0064] [7] The additive supply amount control method according to at least one embodiment of the present disclosure is A method for controlling the amount of additive supplied to a combustion furnace (for example, the combustion furnace 12 described above) for burning a fuel containing phosphorus, A detection step involves analyzing the ash produced by the combustion of the fuel or the fuel itself to detect at least one of the aluminum content and calcium content in the ash, and the phosphorus content in the ash. Addition amount control step: Controlling the amount of an additive containing at least one of alkali metals and alkaline earth metals added to the fuel. Equipped with, In the additive amount control step, the amount of the additive is controlled based on a value obtained by subtracting at least one of the following from a value corresponding to the phosphorus content in the ash (for example, the number of moles of aluminum per unit weight of ash) and a value corresponding to the calcium content in the ash (for example, the number of moles of calcium per unit weight of ash multiplied by 0.6): from a value corresponding to the phosphorus content in the ash (for example, the number of moles of phosphorus per unit weight of ash).

[0065] As a result of diligent research by the inventors of the present invention, analysis of ash discharged from a stably operated combustion furnace using XRD revealed that the phosphate compounds discharged from the combustion furnace included AlPO4 and Ca5(PO4)3(OH), while sodium and potassium phosphate compounds were not detected. Chemical thermodynamic calculations by the inventors of the present invention calculated that the phosphorus in the fuel that was not used to produce AlPO4 and Ca5(PO4)3(OH) (hereinafter referred to as "remaining phosphorus") exists as a sodium / potassium solid solution (a solid of Na / K / P / O of arbitrary composition that is not detected by XRD and therefore not identified as a compound).

[0066] In other words, when the combustion furnace is operating stably, AlPO4 and Ca5(PO4)3(OH) are preferentially produced over alkali metal salts of phosphoric acid, and the remaining phosphorus is thought to exist as sodium phosphate / potassium phosphate salts. Furthermore, it was revealed that if an appropriate amount of alkali metal is supplied to the combustion furnace for the remaining phosphorus, the corrosiveness and corrosion acceleration of phosphoric acid in the molten salt can be suppressed.

[0067] The additive supply control method described in [7] above is based on such findings, and by controlling the amount of additive containing at least one of alkali metals and alkaline earth metals based on a value obtained by subtracting at least one of the values ​​corresponding to the aluminum content in the ash and the calcium content in the ash from a value corresponding to the phosphorus content in the ash, corrosion caused by phosphates can be suppressed with a small amount of additive. [Explanation of Symbols]

[0068] 1. Combustion equipment 2 Boilers 4 Flue 5. Exhaust passage 6 Chimney 8 Fuel supply section 10 Air supply unit 12 Combustion furnaces 14 Heat transfer tubes 16. Cooling section 18. Supplementary section 20 Discharge pipe 21. Exhaust valve 22 Fans 26 Detection unit 28 Additive supply unit 29 Additive supply line 30 tanks 32 Supply pump 34 Supply valve 40 Addition amount control unit 50 Additive supply control system 72 processors 74 RAM 76 ROM 78 HDD 80 Input Interfaces 82 Output Interfaces 84 Bus

Claims

1. A system for controlling the amount of additives supplied to a combustion furnace for burning phosphorus-containing fuel, A detection unit configured to detect at least one of the aluminum content and calcium content in the ash, and the phosphorus content in the ash, by analyzing the ash produced by the combustion of the fuel or the fuel itself. An additive amount control unit configured to control the amount of an additive containing at least one of alkali metals and alkaline earth metals added to the fuel, Equipped with, The additive amount control unit is configured to control the amount of the additive based on a value obtained by subtracting both the value corresponding to the content of aluminum in the ash and the value corresponding to the content of calcium in the ash from the value corresponding to the content of phosphorus in the ash. The detection unit is configured to further detect the sodium and potassium content in the ash by analyzing the ash or the fuel generated by the combustion of the fuel. If the number of moles of sodium, potassium, phosphorus, calcium, and aluminum contained per unit weight of the ash is m Na, m K, m P, m Ca, and m Al, respectively, then The additive amount control unit is configured to control the amount of additive added based on the detection result of the detection unit, such that the value X defined by the following formula (1) is greater than 1, thus providing an additive supply amount control system. X=(mNa+mK) / (mP-0.6×mCa-mAl)...(1)

2. The additive supply amount control system according to claim 1, wherein the additive amount control unit is configured to control the amount of additive to be added so that the value X is 2.6 or more, based on the detection result of the detection unit.

3. The additive supply amount control system according to claim 1 or 2, wherein the additive amount control unit is configured to control the amount of additive to be added so that the value X is less than 3, based on the detection result of the detection unit.

4. The additive supply amount control system according to claim 1, The aforementioned combustion furnace, A combustion facility equipped with the following features.

5. A method for controlling the amount of additive supplied to a combustion furnace for burning phosphorus-containing fuel, A detection step involves analyzing the ash produced by the combustion of the fuel or the fuel itself to detect at least one of the aluminum content and calcium content in the ash, and the phosphorus content in the ash. Addition amount control step: Controlling the amount of an additive containing at least one of alkali metals and alkaline earth metals added to the fuel. Equipped with, In the additive amount control step, the amount of the additive is controlled based on a value obtained by subtracting both the value corresponding to the content of aluminum in the ash and the value corresponding to the content of calcium in the ash from the value corresponding to the content of phosphorus in the ash. The detection step is configured to further detect the sodium and potassium content in the ash by analyzing the ash or the fuel produced by the combustion of the fuel. If the number of moles of sodium, potassium, phosphorus, calcium, and aluminum contained per unit weight of the ash is m Na, m K, m P, m Ca, and m Al, respectively, then An additive supply amount control method, wherein the additive amount control step is configured to control the amount of additive added so that the value X defined by the following formula (1) is greater than 1, based on the detection result of the detection step. X=(mNa+mK) / (mP-0.6×mCa-mAl)...(1)

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