JP2018146137A - Corrosion prevention method and corrosion prevention control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion prevention method and a corrosion prevention control apparatus capable of extended use of cheap fuel and suppressing increase in cost for the corrosion protection.SOLUTION: There is provided a corrosion prevention method comprising: a step (S1) of acquiring composition information of Na, K, Cl and S in a fuel; a step (S2) of specifying based on the acquired information a salt composition including at least one of Na and K that can exist in the combustion ash; a step (S3) of setting a temperature range of a metal of a heat exchanger below the melting point of the salt composition based on melting point information of the salt composition; and a step (S4) of adjusting the metal temperature to stay within the set temperature; wherein the step of specifying the salt composition includes a step of determining possible existence of carbonate in the combustion ash when a total amount of Cl and S in the fuel is smaller than that of Na and K in a stoichiometric ratio, and possible non-existence of carbonate in the combustion ash when a total amount of Cl and S is greater than that of Na and K.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an anticorrosion method and an anticorrosion control device for a heat exchanger in an apparatus that generates energy by burning fuel.

  As an apparatus for generating energy by combustion, there are an industrial boiler, a business boiler, various turbines, and the like. In such devices, fossil fuels such as coal and heavy oil are often used as fuel. For example, Patent Document 1 discloses a thermal boiler using pulverized coal as fuel.

Fossil fuel is a finite resource and is said to be depleted in the future. In recent years, CO ₂ emissions have been reduced from the viewpoint of global warming. Therefore, fossil fuels that emit a large amount of CO ₂ and promote global warming are used from the viewpoint of global environmental conservation. Being regulated.

  Therefore, the use of renewable energy such as waste or biomass is promoted as an alternative to fossil fuels. Biomass is a general term for biological resources created from animals and plants. Biomass that is often used in devices that generate energy through combustion is woody materials such as building waste and thinned wood. Building waste is easier to obtain as a cheaper fuel than thinned wood (unused wood).

JP 2014-228258 A

  In an apparatus that generates energy by combustion, components in the apparatus may corrode due to components contained in the fuel.

  For example, Patent Document 1 discloses that the furnace wall of a boiler is subjected to sulfidation corrosion due to sulfur contained in coal. In Patent Document 1, the degree of sulfide corrosion is predicted with high accuracy by reaction fluid calculation, and the life of the furnace wall tube is evaluated.

  For example, in a boiler that generates energy by burning waste, biomass, or the like, there is a concern that the material of the heat transfer tube in the upper part of the boiler is corroded by molten salt. A part of the ash produced when the fuel is burned adheres to the heat transfer tube and deposits while flowing along with the combustion gas. Molten salt components (K, Na, S, Cl, etc.) are concentrated in the adhering ash. It is known that the chlorine compound contained in the molten salt in the adhered ash particularly induces severe corrosion of the heat transfer tube.

  In order to prevent corrosion due to the molten salt component, usually, a countermeasure such as using a highly corrosion-resistant Ni alloy as the material of the heat transfer tube or setting a regulated value for the chlorine content in the fuel is taken.

  However, Ni alloy is an expensive material, and its use increases the cost. While the cost is reduced with an inexpensive fuel, using an expensive Ni alloy does not lead to the expansion of the use of an inexpensive fuel. In addition, building waste materials tend to contain more molten salt components than unused wood. Therefore, limiting the chlorine content in the fuel does not lead to the expansion of the use of inexpensive fuel.

  The present invention has been made in view of such circumstances, and provides an anticorrosion method and an anticorrosion control device capable of expanding the application of inexpensive fuel and suppressing an increase in cost for anticorrosion. With the goal.

  In order to solve the above problems, the anticorrosion method and anticorrosion control device of the present invention employ the following means.

  The present invention is a method for preventing corrosion of a heat exchanger in an apparatus for generating energy by burning fuel, the step of acquiring composition information of Na, K, Cl and S in the fuel, and the acquired composition information And a step of identifying a salt composition containing at least one of Na and K that may be present in the combustion ash obtained by burning the fuel, and based on melting point information of the salt composition, the metal of the heat exchanger Determining the set temperature range of the salt composition below the melting point of the salt composition, and adjusting the temperature of the metal so as to be within the set temperature range, the step of specifying the salt composition, When the total amount of Cl and S in the fuel is less than the stoichiometric ratio with respect to the total amount of Na and K, carbonate is present in the combustion ash, and the total amount of Cl and S But before If the total amount of Na and the K greater than the stoichiometric ratio, to provide a corrosion protection method comprising the step of determining said carbonate during the combustion ashes can not exist.

  The combustion ash deposited on the metal surface of the heat exchanger contains molten salt components (Na, K, Cl and S). However, in the said invention, since the temperature of the metal of a heat exchanger is adjusted so that it may become less than melting | fusing point of the salt composition which can be contained in combustion ash, formation of molten salt on the metal surface can be prevented. This makes it possible to avoid corrosion of the heat exchanger without limiting the use of expensive corrosion resistant materials and the chlorine content in the fuel.

  A plurality of salts may exist in the combustion ash obtained by burning fuel. The melting point of the salt composition in which a plurality of salts are mixed varies depending on the combination and composition of the mixed salts. Therefore, in order to adjust the metal temperature so that molten salt is not formed, it is important to specify a salt composition that can exist in the combustion ash.

  In the said invention, the salt containing at least one of Na or K of the kind which may exist in combustion ash is specified. Na and K are molten salt cation components contained in the fuel. Na and K react with the molten salt anion component of Cl or S to form a compound. Therefore, the salt that can be contained in the combustion ash can be specified based on the composition information of Na, K, Cl, and S in the fuel.

On the other hand, when the molten salt cation component is present in a greater amount than the stoichiometric ratio with respect to the total amount of Cl and S, the excess molten salt cation component can react with carbonic acid (CO ₂ ) to become carbonate. The melting point information to be used varies depending on the presence or absence of carbonate. Since biomass tends to contain a lot of molten salt cation components, more accurate melting point information can be obtained by determining the presence or absence of carbonate when biomass is used as fuel.

  In one aspect of the invention, the step of adjusting the temperature of the metal is a first adjustment that adjusts a heat transfer area of a heat exchanger at a design stage, and the temperature of the metal is measured during operation of the device. And a second adjustment that adjusts the fuel input amount based on the obtained measured value.

  By adjusting the metal temperature of the heat exchanger in two stages, formation of molten salt can be reliably prevented.

  The present invention is an anticorrosion method for a heat exchanger in an apparatus for generating energy by burning biomass, wherein the composition of Na, K, Cl and S in the biomass is obtained, and the biomass is Na, K, Cl When the total amount of Cl and S is greater than the stoichiometric ratio with respect to the total amount of Na and K, the surface temperature of the metal of the heat exchanger is less than 518 ° C. The heat exchange when the biomass includes Na, K, Cl and S and the total amount of Cl and S is less than the stoichiometric ratio to the total amount of Na and K An anticorrosion method is provided in which the surface temperature of the metal of the vessel is set to less than 544 ° C.

When the biomass contains Na, K, Cl and S, NaCl, KCl, Na ₂ SO ₄ , K ₂ SO ₄ may be present in the combustion ash. The minimum liquid phase formation temperature of the salt composition in which these salts are present is 518 ° C. Therefore, by adjusting the metal temperature to less than 518 ° C., preferably 515 ° C. or less, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

On the other hand, when the molten salt anion component is present in a larger amount than the stoichiometric ratio with respect to the molten salt cation component, carbonates (Na ₂ CO ₃ , K ₂ CO ₃ ) may be further mixed in the combustion ash. The minimum liquid phase formation temperature of such a salt composition is 544 ° C. Therefore, by adjusting the metal temperature to less than 544 ° C., preferably 544 ° C. or less, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

  When the carbonate is included, the minimum liquid phase formation temperature of the salt composition can be increased by about 30 ° C. as compared with the case where the carbonate is not included. The metal temperature of the heat exchanger is preferably higher. According to the above invention, by confirming the presence or absence of carbonate, the energy generation efficiency can be improved by raising the metal temperature as much as possible while suppressing corrosion.

  The present invention is also a method for preventing corrosion of a heat exchanger in an apparatus for generating energy by burning biomass, wherein the composition of Na, K, Cl and S in the biomass is obtained, and the biomass is Na, K When the total amount of Cl and S is greater than the stoichiometric ratio with respect to the total amount of Na and K, the surface temperature of the metal of the heat exchanger Is set to less than 658 ° C., the biomass contains Na, K, and Cl, does not contain S, and the total amount of Cl and S is less than the stoichiometric ratio with respect to the total amount of Na and K In the case where the amount is less, a corrosion prevention method is provided in which the metal surface temperature of the heat exchanger is set to less than 558 ° C.

  If the biomass does not contain S and contains Na, K and Cl, NaCl and KCl may be present in the combustion ash. The minimum liquid phase formation temperature of the salt composition in which these salts are present is 658 ° C. Therefore, by adjusting the metal temperature to less than 658 ° C., preferably 650 ° C. or less, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

On the other hand, when the molten salt anion component is present in a larger amount than the stoichiometric ratio with respect to the molten salt cation component, carbonates (Na ₂ CO ₃ , K ₂ CO ₃ ) may be further mixed in the combustion ash. The minimum liquid phase formation temperature of such a salt composition is 558 ° C. Therefore, by adjusting the metal temperature to less than 558 ° C., preferably 555 ° C. or less, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

  The present invention is also a method for preventing corrosion of a heat exchanger in an apparatus for generating energy by burning biomass, wherein the composition of Na, K, Cl and S in the biomass is obtained, and the biomass is Na, K And S, without Cl, and when the total amount of Cl and S is greater than the stoichiometric ratio to the total amount of Na and K, the metal surface temperature of the heat exchanger Is set to 800 ° C. or less, the biomass contains Na, K and S, does not contain Cl, and the total amount of Cl and S is greater than the stoichiometric ratio with respect to the total amount of Na and K In the case where the amount is too small, the anticorrosion method for setting the metal surface temperature of the heat exchanger to less than 700 ° C. is provided.

Even if Cl is not contained in the fuel, there is a risk that the metal of the heat exchanger is corroded by sulfurization or carburization. Therefore, it is necessary to adjust the metal temperature in order to suppress corrosion. When biomass does not contain Cl and contains Na, K, and S, Na ₂ SO ₄ and K ₂ SO ₄ may be present in the combustion ash. The minimum liquid phase formation temperature of the salt composition in which these salts are present is lower than 850 ° C. and higher than 800 ° C. Therefore, by adjusting the metal temperature to 800 ° C. or lower, preferably 700 ° C. or lower, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

On the other hand, when the molten salt anion component is present in a larger amount than the stoichiometric ratio with respect to the molten salt cation component, carbonates (Na ₂ CO ₃ , K ₂ CO ₃ ) may be further mixed in the combustion ash. The minimum liquid phase formation temperature of such a salt composition is 700 ° C. Therefore, by adjusting the metal temperature to less than 700 ° C., preferably 650 ° C. or less, formation of molten salt can be prevented and corrosion of the heat exchanger can be suppressed.

  Further, the present invention is an anti-corrosion control device that is connected to a device that generates energy by burning fuel and controls the anti-corrosion of a heat exchanger of the device, and includes Na, K, Cl, and S in the fuel. An acquisition unit that acquires composition information, a specifying unit that specifies a salt composition containing at least one of Na or K that may be present in combustion ash obtained by burning the fuel, based on the acquired composition information, and acquisition On the basis of the composition information, when the total amount of Cl and S is greater than the stoichiometric ratio with respect to the total amount of Na and K, carbonate is present in the combustion ash, and the Cl and S A determination unit that determines that no carbonate is present in the combustion ash when the total amount of S is less than the stoichiometric ratio with respect to the total amount of Na and K; and at least one of Na and K Salt group including one Multi-component melting point information of the product, fuel information correlating the metal temperature of the heat exchanger and the amount of fuel input, information of the salt composition specified by the specifying unit and the determination A determination unit that determines a set temperature range of the metal to be lower than the melting point of the salt composition from multi-component melting point information related to the salt composition that may be present in the combustion ash based on the determination result of the part; An anticorrosion control device is provided that includes an adjustment unit that adjusts the amount of fuel to be fed so that the temperature of the fuel falls within the set temperature range.

  In the aspect of the invention described above, the adjustment unit may include a reception unit that receives the measured temperature of the metal, and may adjust the amount of fuel input so that the received measured temperature is within the set temperature range. .

  The present invention can prevent the formation of molten salt on the metal surface by adjusting the temperature of the metal of the heat exchanger so as to be lower than the melting point of the salt composition that can be contained in the combustion ash. As a result, it is possible to expand the application of inexpensive fuel and suppress the increase in cost for anticorrosion.

It is a schematic structure figure of a biomass combustion boiler concerning one embodiment. It is a figure which shows the procedure of the anticorrosion method which concerns on one Embodiment. It is a figure which shows an example of a multicomponent melting point diagram. It is a figure which shows an example of a multicomponent melting point diagram. It is a figure which shows an example of a multicomponent melting point diagram. It is a figure which shows an example of a multicomponent melting point diagram. It is a figure which shows an example of a multicomponent melting point diagram. It is a schematic block diagram of the anticorrosion control apparatus which concerns on one Embodiment. It is the schematic of an adhesion ash layer. It is a figure which shows the result of having analyzed the actual ash condition of the real machine of a biomass combustion boiler. It is a figure which shows the result of having analyzed the actual ash condition of the real machine of a biomass combustion boiler. It is a figure which illustrates the composition information of biomass. Is a diagram illustrating the relationship cationic components in the fuel and _{(K 2 O + Na 2 O} ) and anionic components (2Cl + SO _4).

Below, one embodiment of the anticorrosion method and anticorrosion control device concerning the present invention is described with reference to drawings. The present invention can be applied to an apparatus for generating energy by burning a fuel, which has a heat exchanger in which there is a concern of corrosion due to molten salt. Such devices include biomass fired boilers, waste fired boilers, incinerators and recovery boilers. Heat exchangers that are concerned about corrosion by molten salt are heat transfer tubes such as heaters, reheaters, and economizers. Molten salt components that are of concern for corroding heat exchangers are sodium (Na), potassium (K), chlorine (Cl), sulfur (S) and carbonic acid (CO ₃ ).

  In this embodiment, the anticorrosion method and anticorrosion apparatus applied to a biomass combustion boiler are illustrated.

  In FIG. 1, the schematic block diagram of the biomass combustion boiler 1 is shown. The biomass combustion boiler 1 includes a fuel supply unit 2 that supplies fuel (biomass) F, a furnace 4 that generates heat by burning the supplied fuel in a burner 3, and an upper position of the furnace 4 and the vicinity of the gas outlet 5 6 groups of heat transfer tubes (evaporator, superheater, reheater, economizer) disposed in

  The combustion gas G generated by burning biomass in the furnace 4 flows above the furnace 4, exchanges heat with the heat transfer tube group 6, and is then discharged from the gas discharge port 5 to a downstream exhaust gas treatment facility or the like. High-temperature steam generated by heat exchange in the heat transfer tube group 6 is supplied to a steam turbine (not shown) to drive the steam turbine.

  Combustion ash is contained in the combustion gas. The combustion ash adheres to each heat transfer tube of the heat transfer tube group while the combustion gas flows. The heat transfer tube is made of a metal material such as low alloy steel (2Cr), SUS304, or SUS310. SUS means stainless steel, and SUS304 and SUS310 are both types of stainless steel.

  In FIG. 2, the procedure of the anticorrosion method which concerns on this embodiment is shown. The anticorrosion method according to the present embodiment determines the set temperature range of the heat transfer tube metal, the step of acquiring the composition information of the fuel (S1), the step of specifying the salt composition that may be present in the combustion ash (S2). The process (S3) and the process (S4) which adjusts the metal temperature of a heat exchanger tube are included.

S1: Step of obtaining fuel composition information Woody fuel (pellet, chip), rice straw fuel, PKS (Perm Kellell Shell), etc. are used as fuel biomass. In this step, composition information on at least Na, K, Cl and S in the fuel is acquired.

  The composition information can be obtained, for example, by analysis using a high temperature combustion method, a high frequency inductively coupled plasma (ICP) method, an ion chromatography (IC) method, an atomic absorption method, an XRF (X-ray diffraction method) or the like. As the composition information, composition information provided by a fuel vendor may be used. When obtained by analysis, the composition information is preferably obtained after fuel purchase or before fuel use.

  In the high-temperature combustion method, a sample (fuel) is heated to about 1350 ° C. in an oxygen stream, and all sulfur is oxidized and vaporized. This is a method (see Japanese Industrial Standard JIS M 8813). The high temperature combustion method can quantify S (combustibility S, non-combustibility S) contained in the fuel.

  The ICP method is a method for identifying and quantifying elements by inductively coupled plasma generated by argon gas to heat a sample (fuel) and atomize and thermally excite it. The ICP method can quantify Na and K contained in the fuel.

  The IC method is a method using liquid chromatography (ion exchange chromatography) using an ion exchange resin as a stationary phase and an aqueous electrolyte solution as a mobile phase (eluent). With respect to the peak of the obtained chromatogram, Cl can be identified and quantified by matching the retention time with the standard solution. The fuel is pretreated with a combustion apparatus or the like and then subjected to chromatography.

S2: A step of specifying a salt composition that can exist in the combustion ash Based on the composition information acquired in S1, a salt composition that can exist in the combustion ash is specified. The salt composition that may be present in the combustion ash includes at least one of Na or K. The salt composition that may be present in the combustion ash is a composition composed of one kind of salt or a composition in which a plurality of salts are mixed.

In this step, for example, when Na, K and Cl are contained in the fuel, it is specified that a salt composition containing NaCl and KCl may be present in the combustion ash. For example, when Na, K and S are contained in the fuel, it is specified that a salt composition containing Na ₂ SO ₄ and K ₂ SO ₄ may be present in the combustion ash. For example, when Na, K, Cl and S are contained in the fuel, it is specified that a salt composition containing NaCl, KCl, Na ₂ SO ₄ and K ₂ SO ₄ may be present in the combustion ash.

The step (S2) of identifying a salt composition that may be present in the combustion ash determines whether or not carbonate (Na ₂ CO ₃ , K ₂ CO ₃ ) containing Na or K may be present in the combustion ash. The process of carrying out is included. In the determining step, when the total amount of Cl and S in the fuel is smaller than the stoichiometric ratio with respect to the total amount of Na and K based on the composition information acquired in S1, carbonates are contained in the combustion ash. It is determined that it can exist. In the same process, when the total amount of Cl and S is larger than the stoichiometric ratio with respect to the total amount of Na and K based on the composition information acquired in S1, carbonate cannot be present in the combustion ash. judge.

S3: Step of determining the set temperature range of the metal of the heat transfer tube Based on the melting point information of the salt composition specified in S2, the set temperature range of the metal is the temperature at which the salt composition specified in S2 does not become a molten salt (melting point Less). The lower limit of the set temperature range is not particularly limited, but is usually set to a temperature equal to or higher than the saturation temperature at the water / steam pressure, and is approximately 300 ° C. or higher.

  When the salt composition specified in S2 contains only one kind of salt, the set temperature range is determined within a temperature range (below the melting point) at which the specified salt does not become a molten salt. When a plurality of salts are contained in the salt composition specified in S2, melting point information of the multi-component salt composition can be obtained using a multi-component melting point diagram related to the specified salt. And based on this melting | fusing point information, a preset temperature range is set to the range of the temperature from which a multi-component salt composition does not turn into molten salt. The temperature range in which the multi-component salt composition does not become a molten salt can be obtained by reading the lowest liquid phase formation temperature from the multi-component melting point diagram.

  FIG. 3 to FIG. 7 illustrate multi-component melting points. The numbers described in the figure are melting points (° C.).

FIG. 3 is a quaternary melting point diagram of a KCl—NaCl—K ₂ SO ₄ —Na ₂ SO ₄ salt composition (E. K. Akopov and A. G. Bergman, Zhur. Neorg. Khim., 4 [7]. ] 1655 (1959)).

According to FIG. 3, for example, a quaternary salt composition in which KCl, NaCl, K ₂ SO ₄ and Na ₂ SO ₄ are mixed does not become a molten salt at a temperature of less than 518 ° C. Can be maintained).

  According to FIG. 3, for example, it is possible to obtain melting point information that a binary salt composition in which KCl and NaCl are mixed does not become a molten salt at a temperature lower than 658 ° C.

FIG. 4 shows a ternary melting point diagram of a KCl—Na ₂ CO ₃ —Na ₂ SO ₄ salt composition (AG Bergman and AK Sementsova, Zhur. Neorg. Khim., 3 [2] 395. (See 1958)).

According to FIG. 4, for example, melting point information that a ternary salt composition in which KCl, Na ₂ CO ₃ and Na ₂ SO ₄ are mixed does not become a molten salt at a temperature lower than 544 ° C. is obtained.

FIG. 5 shows a ternary melting point diagram of a KCl—K ₂ SO ₄ —Na ₂ CO ₃ salt composition (AK Sementsova and A. G. Bergman, Zhur. Obshchel. Khim., 26, 995 (1958 ))).

According to FIG. 5, for example, melting point information that a ternary salt composition in which KCl, K ₂ SO ₄ and Na ₂ CO ₃ are mixed does not become a molten salt at a temperature below 546 ° C. is obtained.

Combining the melting point information obtained from FIG. 4 and FIG. 5, a multi-component salt composition in which the fuel contains Na, K, Cl and S and carbonates does not become a molten salt at temperatures below 544 ° C. The melting point information is obtained. 4 and 5 are different from FIG. 3 and do not cover all the compounds to be considered. From FIG. 3, NaCl and KCl, Na ₂ SO ₄ and K ₂ SO ₄ show similar behaviors, It can be adopted as an approximate temperature.

6 shows a quaternary melting point diagram of a KCl—NaCl—K ₂ CO ₃ —Na ₂ CO ₃ salt composition (RN Nyankovskaya, Doklady Akad. Nauk S.S.S.R., 83, 420). (See (1952)).

According to FIG. 6, for example, melting point information that a quaternary salt composition containing KCl, NaCl, K ₂ CO ₃ and Na ₂ CO ₃ does not become a molten salt at a temperature lower than 558 ° C. is obtained.

FIG. 7 shows a quaternary melting point diagram of the K ₂ SO ₄ —Na ₂ SO ₄ —K ₂ CO ₃ —Na ₂ CO ₃ salt composition (AK Sementsova, KA Bvdoklmova, and A.G. Bergman, Zhur. Neorg. Khim., 4, 146 (1968)).

According to FIG. 7, for example, a quaternary salt composition in which K ₂ SO ₄ , Na ₂ SO ₄ , K ₂ CO ₃ and Na ₂ CO ₃ coexist does not become a molten salt at a temperature below 700 ° C. Information is obtained.

According to FIG. 7, for example, melting point information that a binary salt composition in which K ₂ SO ₄ and Na ₂ SO ₄ are mixed does not become a molten salt at a temperature of 800 ° C. or lower is obtained.

S4: Adjusting the metal temperature of the heat transfer tube Adjust the metal temperature so that it falls within the set temperature range determined in S3. The metal temperature is designed from the exhaust gas temperature and the steam temperature at the time of design. When the water / steam cycle temperature is determined, the metal is placed at a position where the exhaust gas temperature is low in order to lower the metal temperature. The exhaust gas temperature and steam temperature are controlled by adjusting the load during operation such as when changing fuel after design.

  In S4, you may implement both the 1st adjustment which adjusts the heat-transfer area of a heat exchanger tube in a design stage, and the 2nd adjustment which adjusts the injection amount of a fuel during operation of a biomass combustion boiler. During the second adjustment, the metal temperature of the heat transfer tube is measured, and the amount of fuel input may be controlled based on the obtained measurement value so that the metal temperature falls within the set temperature range determined in S3. By doing so, the corrosion by molten salt can be prevented more reliably.

  Next, an anticorrosion control device for carrying out the anticorrosion method according to the present embodiment will be described. In FIG. 8, the schematic block diagram of the anticorrosion control apparatus 10 is shown. The anticorrosion control device 10 includes an acquisition unit 11, an identification unit 12, a determination unit 13, a library 14, a determination unit 15, and an adjustment unit 16.

  The acquisition part 11 acquires the composition information of the fuel supplied to a biomass combustion boiler. The composition information includes at least information on Na, K, Cl and S.

  The specifying unit 12 receives the composition information acquired by the acquiring unit 11, and specifies a salt composition containing at least one of Na or K that may be present in the combustion ash based on the composition information.

  The determination part 13 receives the composition information acquired by the acquisition part 11, and determines whether carbonate can exist in combustion ash based on this composition information. When the total amount of Cl and S is larger than the stoichiometric ratio with respect to the total amount of Na and K, the determination unit 13 has carbonate in the combustion ash, and the total amount of Cl and S is Na and K. It is programmed to determine that no carbonate can be present in the combustion ash when less than the stoichiometric ratio to the total amount.

  The library 14 stores multi-component melting point information of a salt containing at least one of Na and K, and fuel information that correlates the metal temperature of the heat transfer tube and the amount of fuel input. The multi-component melting point information is, for example, a multi-component melting point diagram.

  The determining unit 15 receives information on the salt composition specified from the specifying unit 12. The determination unit 15 receives the determination result from the determination unit 13. Based on the acquired composition information and the determination result of the determination unit, the set temperature range of the metal is determined from multi-component melting point information related to the salt composition that may be present in the combustion ash. The set temperature range does not include the temperature at which the salt composition that may be present in the combustion ash becomes a molten salt.

  The adjustment unit 16 receives information on the set temperature range from the determination unit 15 and adjusts the amount of fuel input to the fuel supply unit 2 of the biomass combustion boiler 1 based on the information so that the metal temperature falls within the set temperature range. Send a command to do.

  The adjustment unit 16 may include a reception unit that receives the measured temperature of the metal. The adjustment unit 16 sends a command for adjusting the amount of fuel input so that the received measured temperature is within the set temperature range, to the fuel supply unit.

  The adjusting unit 16 preferably has a receiving unit (not shown) that receives the measured temperature of the metal. For example, the metal is provided with temperature measuring means such as a thermocouple, and the temperature information obtained by the temperature measuring means is received by the receiving unit. Then, the amount of fuel input is adjusted so that the received measured temperature falls within the set temperature range.

  The anticorrosion control device 10 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is preinstalled in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

  Next, the grounds for setting the procedure of the anticorrosion method according to the present embodiment as described above will be described.

  Combustion ash is contained in the combustion gas. When biomass is burned, molten salt components (Na, K, S, and Cl) that may corrode metals are contained in the combustion ash.

  During the flow of the combustion gas G, the combustion ash particles adhere to the surface (metal) of the heat transfer tube 6a and are accumulated to form the attached ash layer 20. FIG. 9 shows a schematic diagram of the attached ash layer 20. The adhesion ash layer 20 is composed of combustion ash particles (fly ash) FA and voids V. The void V is composed of a molten salt component and a gas.

  As shown in FIG. 9, even after the adhesion ash layer 20 is formed, the molten salt component MS penetrates into the adhesion ash layer 20 from the combustion gas G flowing on the surface side of the adhesion ash layer 20. Therefore, the molten salt component MS is concentrated inside the adhered ash layer. Usually, when the molten salt component (particularly Cl) contacts the metal in the molten salt state, severe corrosion is induced.

  On the other hand, even if the molten salt component is concentrated in the adhered ash layer 20 as a result of intensive research, the inventor of the present application will corrode the metal if the molten salt component is present as a solid salt in the portion in contact with the metal. The knowledge that it can suppress greatly was acquired.

  FIG. 10 and FIG. 11 show the results of analyzing the actual ash status of the biomass fired boiler. The analysis is a surface analysis using EPMA. FIG. 10 is a diagram showing a Cl distribution in an attached ash layer formed by accumulating real ash. FIG. 11 is a diagram reproducing the phenomenon of FIG. 10 by calculation. The calculation was performed by thermodynamic calculation incorporating Sile solidification calculation. The software used was ChemSheetver 1.89. FIG. 11A is a diagram showing the relationship between the molten amount distribution (relative value) of the molten salt component and the temperature (° C.) in the attached ash layer. FIG. 11 (B) is a diagram showing the relationship between the combustion ash composition (relative value) and the temperature within the attached ash layer (° C.).

  The temperature inside the attached ash layer 20 was lowest in the innermost layer 21 on the surface side of the heat transfer tube 6 a and increased toward the outer layer 23. The temperature in the innermost layer 21 was about 410 ° C.-525 ° C., the temperature in the inner layer 22 was about 535 ° C.-650 ° C., and the temperature in the outer layer 23 was 660 ° C.-700 ° C.

  According to FIGS. 10 and 11, the Cl content in the adhered ash layer 20 was extremely small in the innermost layer 21 and the outer layer 23, and was large in the inner layer 22. Thereby, it was confirmed that the adhesion ash layer 20 can be divided into three layers of the innermost layer 21, the inner layer 22, and the outer layer 23 in order from the heat transfer tube 6a side. Although not shown in the figure, S and K of the attached ash layer 20 were also measured in the same manner as Cl. As a result, the distribution of S and K is not as biased as that of Cl, and a certain amount exists in the innermost layer 21 and the outer layer 23.

  According to FIG. 11, there is no melting in the innermost layer 21 and the outer layer 23, and a molten salt exists only in the inner layer 22.

  According to the above results, the distribution of Cl, which causes particularly severe corrosion, is uneven, and almost no Cl is present in the innermost layer 21. Since Cl contained in the solid salt is accompanied by a very slow movement between the solid phases at the contact point, the corrosion rate is low, and the corrosion rate of the metal due to Cl contained in the molten salt having a high transfer rate within the phase is high. This fact suggests that if the state of the deposited ash layer 20 in FIG. 10, that is, the state in which the molten salt containing Cl does not penetrate into the metal side (innermost layer 21) can be maintained, the corrosion of the metal can be greatly suppressed. ing.

  In order to prevent the molten salt containing Cl from penetrating into the metal side, in the above embodiment, the metal temperature is set to a range where the molten salt is not formed (below the melting point of the salt composition). Since the innermost layer 21 is covered with the inner layer 22 and the outer layer 23, the innermost layer 21 is less affected by the high-temperature combustion gas G than the outer layer 23 and the inner layer 22. By adjusting the metal to a temperature at which no molten salt is formed, the molten salt component in the innermost layer 21 maintains a solid salt state, and the solid salt can block the penetration of the molten salt from the inner layer 22. As a result, metal corrosion is suppressed.

  FIG. 12 illustrates biomass composition information. Bituminous coal (coal) contained more anionic components (Cl and S) than cationic components (Na and K). Waste (paper mill waste fuel) had a lower proportion of anionic component to cationic component than coal. Wood chips (biomass) contained more cationic components than anionic components.

FIG. 13 shows the relationship between the cation component (K ₂ O + Na ₂ O) and the anion component (2Cl + SO ₄ ) in the fuel. In the figure, the ◆ plot is waste fuel and the ● plot is wood fuel. According to FIG. 13, in the waste fuel, the total amount of the anion component was larger than the stoichiometric ratio with respect to the total amount of the cation component. In the woody fuel, the total amount of the anion component was less than the stoichiometric ratio with respect to the total amount of the cation component.

  When there are more anionic components than cation components such as coal and waste, the cation components (Na and K alkali metals) react with Cl and S to preferentially form chlorine compounds and sulfates. (Verified). Thus, almost no carbonate is formed.

On the other hand, if the cationic component as biomass is higher than the anionic component, the surplus of the cation component is reacted with carbon dioxide (CO _2), are estimated to form the carbonate.

  As can be seen from FIG. 12, the fuel usually contains a plurality of molten salt components. Therefore, a plurality of combinations of salts that may exist in the combustion ash are also conceivable. A multi-component composition containing a plurality of salts has different melting points depending on the combination of salts and the content ratio. Therefore, in order to determine the set temperature range of the metal temperature, it is necessary to specify a salt composition that can exist in the combustion ash.

  Furthermore, as described above, compared with the case where coal and waste are used as fuel, the combustion ash of biomass fuel is more likely to contain carbonate, so it is also necessary to determine the presence or absence of carbonate. .

  By specifying the salt composition that can be present in the combustion ash and further determining the presence or absence of carbonate, it becomes possible to select appropriate melting point information (multi-component melting point diagram). As a result, the metal temperature can be adjusted more reliably so that molten salt is not generated in the innermost layer 21, and the anticorrosion effect can be enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, corrosion of the metal of a heat exchanger tube can be prevented by preventing formation of molten salt on the metal surface. According to the present invention, corrosion due to chlorine can be avoided regardless of the use of an expensive metal as a heat transfer tube material or fuel limitation. Thereby, while expanding application of a cheap fuel, the cost increase for anticorrosion can be suppressed.

  If the molten ash solidifies and adheres to the surface of the adhering ash layer 20 and the heat transfer tube 6a, even if the fuel does not contain Cl, there is a risk of corrosion risk due to sulfurization or carburization. Therefore, it is preferable to apply the anticorrosion method according to the present invention even if the fuel does not contain Cl.

1 Biomass combustion boiler (device that generates energy by burning fuel)
2 Fuel supply section 3 Burner 4 Furnace 5 Gas outlet 6 Heat transfer tube (heat exchanger)
DESCRIPTION OF SYMBOLS 10 Corrosion prevention control apparatus 11 Acquisition part 12 Identification part 13 Determination part 14 Library 15 Determination part 16 Adjustment part

Claims (7)

An anticorrosion method for a heat exchanger in an apparatus for generating energy by burning fuel, comprising:
Obtaining composition information of Na, K, Cl and S in the fuel;
Identifying a salt composition containing at least one of Na or K that may be present in combustion ash obtained by burning the fuel based on the obtained composition information;
Determining a set temperature range of the heat exchanger metal below the melting point of the salt composition based on the melting point information of the salt composition;
Adjusting the temperature of the metal so as to be within the set temperature range;
Including
The step of identifying the salt composition comprises:
When the total amount of Cl and S in the fuel is less than the stoichiometric ratio to the total amount of Na and K, carbonate is present in the combustion ash, and the Cl and S The anticorrosion method including the step of determining that carbonate cannot be present in the combustion ash when the total amount is greater than the stoichiometric ratio with respect to the total amount of Na and K. Adjusting the temperature of the metal,
A first adjustment for adjusting a heat transfer area of the heat exchanger at a design stage;
A second adjustment for measuring the temperature of the metal during the operation of the device and adjusting the amount of fuel input based on the obtained measurement value;
The anticorrosion method of Claim 1 containing this. An anticorrosion method for a heat exchanger in an apparatus that generates energy by burning biomass,
Obtaining the composition of Na, K, Cl and S in the biomass;
When the biomass includes Na, K, Cl and S, and the total amount of Cl and S is greater than the stoichiometric ratio to the total amount of Na and K, the metal of the heat exchanger Set the surface temperature to less than 518 ° C,
When the biomass contains Na, K, Cl and S, and the total amount of Cl and S is less than the stoichiometric ratio to the total amount of Na and K, the metal of the heat exchanger The anticorrosion method which sets the surface temperature of less than 544 degreeC. An anticorrosion method for a heat exchanger in an apparatus that generates energy by burning biomass,
Obtaining the composition of Na, K, Cl and S in the biomass;
The heat exchange when the biomass contains Na, K and Cl, does not contain S, and the total amount of Cl and S is greater than the stoichiometric ratio to the total amount of Na and K Set the metal surface temperature below 658 ° C,
The heat exchange when the biomass contains Na, K and Cl, does not contain S, and the total amount of Cl and S is less than the stoichiometric ratio to the total amount of Na and K Anticorrosion method for setting the surface temperature of the metal of the vessel to less than 558 ° C An anticorrosion method for a heat exchanger in an apparatus that generates energy by burning biomass,
Obtaining the composition of Na, K, Cl and S in the biomass;
The heat exchange when the biomass contains Na, K and S, does not contain Cl, and the total amount of Cl and S is greater than the stoichiometric ratio to the total amount of Na and K Set the surface temperature of the metal of the vessel to 800 ° C or lower,
The heat exchange when the biomass contains Na, K and S, does not contain Cl, and the total amount of Cl and S is less than the stoichiometric ratio with respect to the total amount of Na and K Anticorrosion method for setting the surface temperature of the metal of the vessel to less than 700 ° C. An anti-corrosion control device connected to a device for generating energy by burning fuel and controlling the anti-corrosion of the heat exchanger of the device,
An acquisition unit for acquiring composition information of Na, K, Cl and S in the fuel;
Based on the obtained composition information, a specific unit that identifies a salt composition containing at least one of Na or K that may be present in combustion ash obtained by burning the fuel;
Based on the obtained composition information, when the total amount of Cl and S is greater than the stoichiometric ratio with respect to the total amount of Na and K, carbonate is present in the combustion ash, and the Cl And a determination unit that determines that no carbonate is present in the combustion ash when the total amount of S is less than the stoichiometric ratio with respect to the total amount of Na and K.
A library storing multi-component melting point information of a salt composition containing at least one of Na and K, and fuel information correlating a temperature of a metal of the heat exchanger and a fuel input amount;
Based on the information on the salt composition specified by the specifying unit and the determination result of the determining unit, the set temperature range of the metal is determined from multi-component melting point information related to the salt composition that may be present in the combustion ash. A determinator that determines less than the melting point of the salt composition;
An adjustment unit that adjusts the amount of fuel input so that the temperature of the metal falls within the set temperature range;
An anticorrosion control device. The adjusting unit has a receiving unit that receives the measured temperature of the metal,
The anticorrosion control device according to claim 6, wherein the amount of fuel input is adjusted so that the received measured temperature falls within the set temperature range.

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