How to select a scale dissolving agent

Abstract

The present invention pertains to a method for selecting a solubilizer suitable for scale components.　Provided are: a method for selecting a scale solubilizer, the method comprising a step for obtaining the coordinates of an intrinsic physical property value of scale to be removed based on the Hansen parameter, and a step for selecting a solubilizer on the basis of a distance between the coordinates of the intrinsic physical property value of the scale to be removed and the coordinates of an intrinsic physical property value of a solubilizer; and a method for removing scale using the same.

Description

[Technical field]

[0001] The present invention relates to a method for selecting a scale dissolving agent and a method for removing scale. [Background technology]

[0002] 2. Description of the Related Art Conventionally, scale deposition has been a problem in systems that include a fluid distribution system, such as power plant systems, ship systems, boiler systems, and steel plant systems.

[0003] It is known to use cleaning agents to remove scale. For example, in geothermal power plants, a method of cleaning sulfur scale using hydrazine capable of dissolving elemental sulfur, or a mixed aqueous solution of sodium sulfite or sodium sulfide and a wetting agent is known for the purpose of preventing operational troubles caused by the formation and adhesion of sulfur scale (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-141299 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 concludes that a dissolving agent that easily dissolves elemental sulfur is effective as a dissolving agent for sulfur scale. However, in geothermal power plants, the main component of sulfur scale that covers the substrate surface of the hydrogen sulfide flow section is iron sulfide. In addition, the surface of the iron sulfide has a multi-layer structure covered with silica scale. Therefore, the dissolving agent disclosed in Patent Document 1 does not dissolve the scale, which causes a problem of increased maintenance costs.

[0006] For example, geothermal power plants are scattered throughout Japan and overseas, and the components of the scale generated at each geothermal power plant vary even within Japan. Furthermore, even within the same plant, the components of the circulating fluid vary depending on the location. For this reason, it was sometimes difficult to remove scale using only a solvent that can dissolve and remove specific components.

[0007] In addition, in various plants other than geothermal power plants where fluids flow, various types of scale are formed due to components contained in the fluid, and dissolving agents that can only dissolve and remove specific components are insufficient. [Means for solving the problem]

[0008] In order to select a dissolving agent according to the components of the scale, the inventors have considered selecting a dissolving agent for the scale to be removed based on the Hansen solubility parameter (HSP). Methods for selecting a solvent for removing adhesives and a resin coating remover based on the value of the interaction distance of the Hansen solubility parameter are known (for example, JP 2020-107754 A and JP 2015-113367 A).

[0009] However, there is no information on the selection of a dissolving agent for a substance such as scale that adheres without artificial manipulation and exists in a non-uniform and unknown form or in a multi-layer structure. As a result of further intensive research, the inventors of the present invention came up with the idea of ​​selecting a dissolving agent that corresponds to the composition and structure of the scale to be removed, and have completed the present invention.

[0010] That is, according to one embodiment, the present invention provides a method for selecting a scale dissolving agent, comprising the steps of: A step of obtaining coordinates of intrinsic physical properties based on the Hansen solubility for the scale to be removed; selecting a dissolving agent based on a distance between the coordinates of the characteristic physical property value of the scale to be removed and the coordinates of the characteristic physical property value of the dissolving agent; Includes.

[0011] In the method for selecting a scale dissolving agent, the intrinsic physical property value is preferably one or more selected from a dispersion force δd, a dipole-dipole force δp, and a hydrogen bonding force δh.

[0012] In the method for selecting a scale dissolving agent, the step of selecting the dissolving agent is a step of selecting a mixed dissolving agent obtained by mixing two or more different substances, It is preferable that the composition of the mixed dissolution agent is determined so that the coordinates of the characteristic physical property values ​​based on the Hansen solubility of the mixed dissolution agent are close to the coordinates of the characteristic physical property values ​​of the scale to be removed.

[0013] In the method for selecting a scale dissolving agent, the mixed dissolving agent is a mixed dissolving agent obtained by mixing a substance A at x (mol%) and a substance B at y (mol%), and the step of selecting the mixed dissolving agent comprises: The dispersion force of the scale to be removed is δdS, the dipole-dipole force is δpS, the hydrogen bond force is δhS, The dispersion force of substance A is δdA, the dipole-dipole force is δpA, and the hydrogen bond force is δhA. If the dispersion force of substance B is δdB, the dipole-dipole force is δpB, and the hydrogen bond force is δhB, then Distance Ra2 between the coordinates of the characteristic property value of the mixed dissolving agent and the coordinates of the characteristic property value of the scale to be removed: Ra2=[4×{δdS-(δdA×x / 100+δdB×y / 100)} 2 +{δpS-(δpA×x / 100+δpB×y / 100)} 2 +{δhS-(δhA×x / 100+δhB×y / 100)} 2 ] 1 / 2 It is preferable to include a step of determining material A, material B, x, and y so that

[0014] In the method for selecting a scale dissolving agent, the step of selecting the dissolving agent is a step of selecting a single dissolving agent consisting of a single substance C, and the selection step includes: The dispersion force of the scale to be removed is δdS, the dipole-dipole force is δpS, the hydrogen bond force is δhS, If the dispersion force of substance C is δdC, the dipole-dipole force is δpC, and the hydrogen bond force is δhC, then Distance Ra1 between the coordinates of the characteristic property value of material C and the coordinates of the characteristic property value of the scale to be removed: Ra1 = {4 × (δdS-δdC) 2 +(δpS-δpC) 2 +(δhS-δhC) 2} 1 / 2 It is preferable that the step of selecting a substance C having a smaller value is performed.

[0015] In the method for selecting a scale dissolving agent, the step of obtaining coordinates of intrinsic physical property values ​​based on Hansen solubility for the scale to be removed preferably includes the step of sampling the scale and obtaining the coordinates of the intrinsic physical property values.

[0016] In the method for selecting a scale dissolving agent, it is preferable that the step of obtaining coordinates of characteristic physical property values ​​based on the Hansen solubility for the scale to be removed includes a step of obtaining coordinates of characteristic physical property values ​​based on elemental analysis of a fluid containing a substance that causes scale formation.

[0017] In the method for selecting a scale dissolving agent, the elemental analysis method is preferably a method using inductively coupled plasma.

[0018] In the method for selecting a scale dissolving agent, it is preferable that the scale to be removed contains iron sulfide and the substance C is acetic acid, and / or the scale to be removed contains silica and the substance C is hydrofluoric acid.

[0019] According to another embodiment, the present invention provides a method for removing scale, comprising the steps of selecting a scale dissolving agent based on any one of the methods for selecting a scale dissolving agent described above; and applying the scale dissolving agent obtained by the selecting step to the scale to be removed.

[0020] In the scale removal method, in addition to the step of applying the scale dissolving agent to the scale to be removed, it is preferable that the method further comprises the step of removing the scale by a physical method.

[0021] In the scale removal method, the physical method comprises: A step of subjecting the scale to a temperature change to generate a shear force; and / or A step of applying a mechanical force to the scale to be removed. It is preferred that the compound contains

[0022] In the scale removal method, the scale to be removed includes two or more layers composed of different components, the step of selecting a scale dissolving agent includes the step of selecting a scale dissolving agent for each of the two or more layers individually; It is preferable that the step of applying the scale dissolving agent to the scale to be removed includes a step of sequentially applying individually selected scale dissolving agents to the two or more layers, or a step of mixing and preparing individually selected scale dissolving agents and applying them to the two or more layers.

[0023] According to another embodiment, the present invention relates to a method for producing a mixed dissolving agent, the method including the steps of selecting a mixed dissolving agent based on the above-mentioned method for selecting a mixed dissolving agent, and preparing the mixed dissolving agent. Effect of the Invention

[0024] According to the method for selecting a scale dissolving agent of the present invention, a dissolving agent corresponding to the components of the scale to be removed can be selected, and even for scale generated in various types of plants or scale adhering to different locations within the same plant, a dissolving agent suited to the properties of the scale can be selected. In addition, it becomes possible to select and manufacture a dissolving agent containing multiple components. Furthermore, it is possible to provide an effective scale removal method using these dissolving agents. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram for explaining an example of a method for selecting a single solubilizing agent according to a first aspect of a first embodiment of the present invention, and is a diagram showing coordinates of intrinsic physical property values ​​based on the Hansen solubility index. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of a laminated form of the scale. [Diagram 3] FIG. 3 is a diagram for explaining an example of a method for selecting a mixed solubilizer according to the second aspect of the first embodiment of the present invention, and is a diagram showing the coordinates of intrinsic physical property values ​​based on the Hansen solubility. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment described below.

[0027] [First embodiment: Selection of dissolving agent] According to a first embodiment, the present invention relates to a method for selecting a dissolving agent. The selection method includes the following steps. (1) A process for obtaining the coordinates of the intrinsic physical properties based on the Hansen solubility for the scale to be removed (2) selecting a dissolving agent based on the distance between the coordinates of the characteristic physical property values ​​of the scale to be removed and the coordinates of the characteristic physical property values ​​of the dissolving agent;

[0028] In the present invention, a dissolving agent is a substance capable of reducing the amount of scale adhesion by dissolving the scale to be removed, and may be a single substance or a mixture of two or more substances. In this specification, a dissolving agent consisting of a single substance is also referred to as a single dissolving agent. Also, a dissolving agent consisting of a mixture of two or more substances is also referred to as a mixed dissolving agent.

[0029] The scale to be removed may be any scale that may contain inorganic compounds and organic compounds. More specifically, the scale may be generated and attached due to a substance dissolved in a fluid substance such as flowing water in a power plant system such as geothermal, thermal, atomic, hydroelectric, or biomass, ship systems such as ship exhaust gas cleaning systems (EGCS), seawater desalination systems, factory heating heat sources, boiler systems for building heating and hot water supply, cooling water systems, cleaning water systems, and other steel plant systems, and the type of the scale is not particularly limited. For example, in a geothermal power plant, the scale may be multi-component scale that is generated in layers on substrates such as pipes, heat exchangers, turbines, and drains that constitute the plant.

[0030] The intrinsic property value based on the Hansen solubility may be one or more selected from the dispersion force δd, the dipole-dipole force δp, and the hydrogen bond force δh. Therefore, the selection method may be based on one-dimensional coordinates consisting of one intrinsic property value, may be based on two-dimensional coordinates consisting of two intrinsic property values, or may be based on three-dimensional coordinates consisting of three intrinsic property values.

[0031] The method for selecting a dissolving agent according to the present embodiment will be described below in terms of the selection of a single dissolving agent and the selection of a mixed dissolving agent.

[0032] [First aspect: Selection of a single dissolving agent] According to a first aspect, the selection method of the present embodiment relates to a method for selecting a single dissolving agent. The method for selecting a single dissolving agent includes the following steps. (A) A process for obtaining coordinates of intrinsic physical properties based on the Hansen solubility for the scale to be removed (B) selecting a dissolving agent based on a distance from the coordinates of the characteristic property value of the scale to be removed, The dissolving agent is a single dissolving agent consisting of a single substance C, The dispersion force of the scale to be removed is δdS, the dipole-dipole force is δpS, the hydrogen bond force is δhS, When the dispersion force of substance C is δdC, the dipole-dipole force is δpC, and the hydrogen bond force is δhC, Distance Ra1 between the coordinates of the characteristic property value of the scale to be removed and the coordinates of the characteristic property value of material C: Ra1 = {4 × (δdS-δdC) 2 +(δpS-δpC) 2 +(δhS-δhC) 2} 1 / 2 (1) A step of selecting a substance C having a smaller

[0033] In step (A), the coordinates of the intrinsic physical property values ​​based on the Hansen solubility are obtained for the scale to be removed. Figure 1 is a conceptual diagram of a three-dimensional coordinate space used in the method for selecting a single dissolving agent. Three axes, dispersion force δd, dipole-dipole force δp, and hydrogen bond force δh, are set in the coordinate space, and the coordinate S of the scale to be plotted in this space is obtained in step (A).

[0034] The coordinates δdS, δpS, and δhS of the characteristic physical property values ​​of the scale to be removed can generally be obtained by experimentation, for example, including a step of collecting the scale to be removed at a desired location in the target plant, analyzing the layer structure and components of the scale, and a step of experimentally obtaining the coordinates of the characteristic physical property values ​​from the components.

[0035] FIG. 2 is a diagram showing a schematic structure of scale adhering to pipes and equipment in a geothermal power plant. Water containing dissolved silica and sulfur flows through a geothermal power plant, and layered scale may adhere to the plant. Referring to FIG. 2, a first layer 2 made of sulfur scale mainly composed of iron sulfide is formed on a substrate 1 made of steel or the like, and a second layer 3 made of silica scale mainly composed of silica is formed on the first layer 2. Note that FIG. 2 is a schematic diagram, and the thickness of the layer of the actual scale may be uneven or there may be a portion where the layer is interrupted. In addition, if the material of the substrate is different, the components of the scale generated will also be different. Furthermore, even in the same plant, the ease of scale generation and the growth rate differ depending on the location. Therefore, it is preferable to analyze such layer structure according to the location where the scale to be removed adheres, and to analyze the components of each layer. As shown in FIG. 2, when the scale is composed of multiple layers with different main components, a dissolving agent suitable for each layer can be extracted.

[0036] The coordinates δdS, δpS, and δhS of the characteristic physical properties of the scale to be removed can also be estimated from the composition ratio of the components of the fluid flowing through the plant. This is useful when it is difficult to stop the operation of the plant system, or when it is impossible to sample the scale because it is severely stuck and cannot be peeled off, or when it is necessary to obtain the composition of the scale in a simple manner. Since the composition of the fluid flowing through the plant varies depending on the location of the plant, the fluid can be sampled at the desired location. For example, in a geothermal power plant, the liquid flowing through the production well, the reinjection well, the heat exchanger, etc. can be sampled.

[0037] The collected fluid can be analyzed by any analytical method. The analytical method can be based on a trace element analysis method. For example, element analysis can be performed by a method using inductively coupled plasma, more specifically, ICP-MS analysis can be used, but is not limited to a specific method.

[0038] The process of experimentally obtaining the coordinates of the intrinsic physical properties from actually collected scale components or from the results of elemental analysis of the fluid can be carried out, for example, by a penetration rate method in which a solvent is penetrated into the scale particles and the affinity is evaluated.

[0039] Next, in step (B), a dissolving agent is selected based on the distance from the coordinates of the characteristic physical property value of the scale to be removed. More specifically, a substance C having the coordinates of the characteristic physical property value close to the distance Ra1 from the coordinates of the characteristic physical property value of the scale to be removed is selected.

[0040] The Hansen solubility parameters of a substance can be obtained from a database. Also, if the structure of a substance is known, the Hansen solubility parameters of the substance can be obtained using the Hansen Solubility Parameter software HSPiP (Hansen Solubility Parameter in Practice).

[0041] In the coordinate space shown in Figure 1, the coordinates of six candidate substances a, b, C, d, e, and f are plotted. Of these, substance C, which has the closest distance Ra1, can be selected as the dissolving agent for scale S. Among these substances, substances with coordinates of intrinsic physical properties close to the coordinates (δdS, δpS, δhS) of the intrinsic physical properties of the scale S to be removed can be said to be good dissolving agents for scale S, and substances with coordinates of intrinsic physical properties farther away can be said to be poor dissolving agents for scale S. Substance C, which has the smaller distance Ra1, is the most preferable dissolving agent.

[0042] In FIG. 1, if we imagine a sphere of radius r centered on the coordinates (δdS, δpS, δhS) of the inherent physical property values ​​of the scale S to be removed in the coordinate space, it can be said that if a material has coordinates (δdC, δpC, δhC) within the sphere within a certain radius r, the scale S to be removed can generally be dissolved with high efficiency. The radius r is preferably 10 (MPa 1 / 2 ) or less, the smaller the better, and the closer to 0 is the most preferable. In other words, when the distance Ra1 between the coordinates of the inherent physical property value of the scale S to be removed is 10 (MPa 1 / 2) or less, a substance with a characteristic property value coordinate can be said to be a good solubility agent. However, 1 / 2 ) or less, if there is no substance with the coordinates of the intrinsic physical properties, the distance Ra1 is 10(MPa 1 / 2 ), the substance with the smallest distance Ra1 may be selected as the dissolving agent.

[0043] Alternatively, instead of using the distance Ra1 as the only index, multiple indexes such as the price and ease of handling of the candidates may be set to comprehensively select the substance and the dissolving agent.

[0044] In FIG. 1, a three-dimensional coordinate space is illustrated, but in two-dimensional coordinates, two of δd, δp, and δh are selected for each of the scale and the dissolving agent, and the distance between the coordinates Ra1 is calculated in the same manner, and a substance can be selected. In the above formula (1), the two-dimensional coordinates can be considered as a case where any one of δdS-δdC, δpS-δpC, and δhS-δhC is 0 or close to 0, that is, any one of the characteristic physical properties is the same for the scale and the dissolving agent. In the case of one-dimensional coordinates, one of δd, δp, and δh are selected for each of the scale and the dissolving agent, and the distance between the coordinates Ra1 is calculated in the same manner, and a substance can be selected. In the above formula (1), the one-dimensional coordinates can be considered as a case where any two of δdS-δdC, δpS-δpC, and δhS-δhC are 0 or close to 0, that is, any two of the characteristic physical properties are the same for the scale and the dissolving agent.

[0045] As an example, when the scale S to be removed is silica scale, whose main component is silica (SiO2), there may be multiple candidate substances, but among them, hydrofluoric acid can be extracted as a substance with a small coordinate distance Ra1, and hydrofluoric acid can be used as a single dissolving agent. If the coordinates of the characteristic physical properties of silica scale are plotted as in Figure 1, the coordinates of the characteristic physical properties of hydrofluoric acid are 1 / 2 ) (not shown).

[0046] As another example, when the scale to be removed S is sulfur scale whose main component is iron sulfide (FeS), there may be multiple candidate substances, but among them, acetic acid can be extracted as the substance with the smallest coordinate distance Ra1, and acetic acid can be used as the sole dissolving agent. If the coordinates of the characteristic physical properties of sulfur scale are plotted as in Figure 1, the coordinates of the characteristic physical properties of acetic acid are 1 / 2 ) (not shown).

[0047] [Second aspect: Selection of mixed dissolving agent] According to a second aspect, the selection method of the present embodiment relates to a method for selecting a mixed dissolving agent. The selection method of a mixed dissolving agent includes the following steps. (a) A step of obtaining coordinates of intrinsic physical properties based on the Hansen solubility for the scale to be removed (b) selecting a mixed dissolving agent containing two or more different substances based on a distance from the coordinates of the characteristic physical property value of the scale to be removed, A step of determining the composition of the mixed dissolving agent so that the coordinates of the characteristic physical property values ​​based on the Hansen solubility of the mixed dissolving agent are close to the coordinates of the characteristic physical property values ​​of the scale to be removed.

[0048] In the second embodiment, step (a) can be carried out in the same manner as step (A) in the first embodiment, and therefore a description thereof will be omitted here.

[0049] For step (b), the multiple substances constituting the mixed dissolving agent and their mixing ratio are determined so that the distance Ra2 between the coordinates of the intrinsic physical property value of the scale to be removed and the coordinates of the intrinsic physical property value based on the Hansen solubility of the mixed dissolving agent is close.

[0050] Here, the case where the mixed dissolving agent is composed of two kinds of substances A and B will be described by way of example, and the distance Ra2 in the three-dimensional coordinate system will be defined. When substance A is mixed with substance B at x (mol%) and y (mol%) (where x+y=100), The dispersion force of the scale to be removed is δdS, the dipole-dipole force is δpS, the hydrogen bond force is δhS, The dispersion force of substance A is δdA, the dipole-dipole force is δpA, and the hydrogen bond force is δhA. If the dispersion force of substance B is δdB, the dipole-dipole force is δpB, and the hydrogen bond force is δhB, then The distance Ra2 between the coordinates of the inherent physical property values ​​of the mixed dissolving agent and the coordinates of the inherent physical property values ​​of the scale to be removed can be expressed as follows. Ra2=[4×{δdS-(δdA×x / 100+δdB×y / 100)} 2 +{δpS-(δpA×x / 100+δpB×y / 100)} 2 +{δhS-(δhA×x / 100+δhB×y / 100)} 2 ] 1 / 2 (2)

[0051] Material A and material B are selected so that the line segment connecting the coordinates of their respective inherent physical properties intersects or touches a sphere of radius r centered on the coordinates of the inherent physical properties of the scale to be removed. The value of radius r is 10(MPa 1 / 2 ), but it can be as low as 10 (MPa 1 / 2 ) can be set to a value exceeding the value of the inherent physical property of the substance A and the substance B. The coordinates of the inherent physical property of the substance A and the substance B can be obtained in the same manner as the selection of the candidate substance in the step (B) of the first embodiment. Next, the components and the composition of the mixed dissolving agent can be selected by determining the values ​​of x and y so that Ra2 approaches 0.

[0052] FIG. 3 is a conceptual diagram of a three-dimensional coordinate space used in the method for selecting a mixed dissolving agent. The coordinates S of the characteristic physical property value of the scale to be plotted in this space are determined in step (a). Six types of substances A, B, C, d, e, and f are plotted in the coordinate space shown in FIG. 3. Of these, substance C is a single dissolving agent selected in the first embodiment for the same scale to be removed. Substances A and B are arranged such that the line segment connecting the coordinates of their characteristic physical property values ​​has a radius of r = 10 (MPa 1 / 2) sphere. Therefore, candidate substances A and B can be components of a mixed dissolving agent with scale S. Then, by applying the coordinates of the intrinsic physical property values ​​of candidate substances A and B to equation (2) and calculating them, it is possible to calculate the values ​​of x and y where Ra2 approaches 0, and obtain the coordinate M of the intrinsic physical property value of the mixed dissolving agent. In other words, it is possible to select a mixed dissolving agent that contains substances A and B in a molar ratio of x:y.

[0053] In the second embodiment, the distance Ra2 between the coordinate S of the characteristic property value of the scale to be removed and the coordinate M of the characteristic property value of the mixed dissolving agent is 10 (MPa 1 / 2 ) or less, the mixed dissolving agent can be said to be a good dissolving agent. However, if the distance Ra2 is 10 (MPa 1 / 2 ) or less, if there are no substances A, B, and proportions x and y that realize the composition of the mixed solvent with the coordinates of the characteristic physical properties of the following, the distance Ra2 is 10 (MPa 1 / 2 ), the substance with the smallest distance Ra2 may be selected as the dissolving agent.

[0054] Here, a mixed dissolving agent containing substance A and substance B in a molar ratio of x:y may be more advantageous than a single dissolving agent consisting of substance C in the following cases. If the price of the mixed solubilizer is less than the price of a single solubilizer, or When Ra2 of mixed dissolving agent is less than Ra1 of single dissolving agent Therefore, the method for selecting a dissolution agent of the present invention also includes a method comprising a step of combining and comparing the selection method according to the first embodiment and the selection method according to the second embodiment.

[0055] In this way, the selection method according to the second aspect of the present embodiment can select a good dissolving agent by using multiple substances that do not become good dissolving agents by themselves. Therefore, it is possible to significantly increase the options of dissolving agents, and it is possible to shorten the maintenance time and reduce the maintenance costs of plants where scale adhesion is a problem. In addition, by using the selection method according to the first aspect and the selection method according to the second aspect in combination, it is possible to select a dissolving agent that is more suitable for use.

[0056] [Second embodiment: Method for producing mixed dissolving agent] According to a second embodiment, the present invention relates to a method for producing a mixed dissolving agent. The method for producing a mixed dissolving agent includes the following steps: (i) selecting a mixed dissolving agent by the selection method described in the second aspect of the first embodiment; (ii) mixing two or more different substances selected by the above steps to prepare a mixed dissolving agent;

[0057] Step (i) of this embodiment can be carried out in the same manner as the second aspect of the first embodiment, and therefore a description thereof will be omitted here. Step (ii) can be carried out by mixing two or more substances selected in step (i) in the ratio determined in step (i).

[0058] According to the present embodiment, a mixed dissolving agent according to the components of scale can be produced, which shortens the plant maintenance time and reduces the maintenance costs. In particular, even if an appropriate single dissolving agent does not exist, a mixed dissolving agent can be obtained by the production method of the present embodiment and can be used to remove scale.

[0059] [Third embodiment: scale removal method] According to a third embodiment, the present invention relates to a method for removing scale. The method for removing scale includes the following steps. (I) A step of selecting a scale dissolving agent based on the selection method described in the first embodiment. (II) A step of applying the scale dissolving agent obtained by the selecting step to the scale to be removed. In addition, the following steps may be further included as optional steps. (III) applying the scale dissolving agent to the scale to be removed and removing the scale by a physical method

[0060] Step (I) in this embodiment can be carried out by the method described in the first embodiment, and therefore a description thereof will be omitted here.

[0061] In step (II), the dissolving agent selected in step (I) is prepared and applied to the scale to be removed. Methods of application include, but are not limited to, spraying the dissolving agent onto the scale to be removed, pouring the dissolving agent onto the equipment to which the scale to be removed is attached, contacting the scale to be removed with the dissolving agent for a predetermined period of time, spraying the dissolving agent onto the scale to be removed, injecting the dissolving agent onto the scale to be removed, applying the dissolving agent to the scale to be removed by any of the methods described above and then immersing the scale in the dissolving agent with ultrasound.

[0062] Step (III) is a step of carrying out a method in which a physical force is applied to the scale, and can be used in combination with the use of a dissolving agent. In terms of chronological order, the dissolving agent and the physical method can be carried out simultaneously, or either one can be carried out first. Preferably, the physical method can be carried out after the application of the dissolving agent to the scale to be removed.

[0063] An example of a specific physical method is a step of applying a temperature change to the scale to be removed to generate a shear force. In this step, a temperature change is applied to the scale and the member where the scale is generated, and a shear force caused by the difference in linear expansion coefficient accompanying the temperature change causes cracks or fissures in the scale, making it easier to peel off. For example, a step of heating the scale and its surrounding members and a step of cooling the scale can be performed. Heating and cooling can be performed repeatedly. These operations are advantageous in that a temperature difference is applied to the scale and its surrounding members, and preferably the temperature difference is increased, thereby maximizing the thermal stress that is generated. For the heating step, one or more means selected from a heater, induction heating (IH), microwaves, burners, boiler steam, and hot air can be used. For the cooling step, one or more means selected from a chiller, river water, dry mist, and cold air can be used.

[0064] Another example of a specific physical method is a step of applying a mechanical force to the scale to be removed. In this step, a tool or the like can be used to perform mechanical operations such as polishing, cutting, peeling, drilling, striking, vibrating (with a vibrator or ultrasonic waves), cutting, peeling, and / or crushing on the scale to be removed. A plurality of different physical methods can also be used in combination, and the physical method is not limited to the exemplified methods.

[0065] When the scale to be removed is a multi-layered scale including two or more layers made of different components, the scale can be removed based on information on the layer structure and components in the thickness direction of the scale to be removed obtained in step (A) or step (a) of the method for selecting a dissolving agent. Specifically, a scale dissolving agent can be selected individually for each of the two or more layers, and the individually selected scale dissolving agents can be applied sequentially to the two or more layers, or the individually selected scale dissolving agents can be mixed and prepared and applied to the two or more layers. When mixed and prepared, the mixing ratio can be determined based on the ratio of the thickness, mass, volume, etc. of the two or more layers.

[0066] According to the scale removal method of the present embodiment, a dissolving agent selected according to the scale to be removed is used, making it possible to remove the scale effectively and economically. EXAMPLES

[0067] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0068] A single dissolving agent was selected using three-dimensional coordinates according to the procedure described in the first aspect of the first embodiment of the present invention. The scale to be removed was assumed to be sulfur scale (FeS). The coordinates of the characteristic physical properties of the scale to be removed were experimentally obtained using the penetration rate method. As a result of calculation using formula (1), a value of Ra1 of 1.6 was obtained for sulfur scale, and acetic acid was selected as the dissolving agent. The coordinates of the characteristic physical properties of the selected acetic acid were δd 14.5, δp 8.0, and δh 13.5. [Industrial Applicability]

[0069] The method for selecting a scale dissolving agent, the method for removing scale, and the method for producing a scale dissolving agent according to the present invention can be applied to the removal of scale in various plant systems.

Claims

1. A step of obtaining coordinates of intrinsic physical properties based on the Hansen solubility for the scale to be removed; selecting a dissolving agent based on a distance between the coordinates of the characteristic physical property value of the scale to be removed and the coordinates of the characteristic physical property value of the dissolving agent; A method for selecting a scale dissolving agent, comprising: The intrinsic physical property values ​​are represented by a dispersion force δd, a dipole-dipole force δp, and a hydrogen bond force δh, The step of selecting a dissolving agent is a step of selecting a mixed dissolving agent obtained by mixing two different substances, The mixed dissolving agent is a mixed dissolving agent in which a substance A is mixed with a substance B at x (mol %) and y (mol %), and the step of selecting the mixed dissolving agent comprises: The dispersion force of the scale to be removed is δdS, the dipole-dipole force is δpS, the hydrogen bond force is δhS, The dispersion force of substance A is δdA, the dipole-dipole force is δpA, and the hydrogen bond force is δhA. If the dispersion force of substance B is δdB, the dipole-dipole force is δpB, and the hydrogen bond force is δhB, then The distance Ra between the coordinates of the characteristic property value of the mixed dissolving agent and the coordinates of the characteristic property value of the scale to be removed ２ : Ra ２ =[4×{δdS-(δdA×x / 100+δdB×y / 100)} ２ +{δpS-(δpA×x / 100+δpB×y / 100)} ２ +{δhS-(δhA×x / 100+δhB×y / 100)} ２ ] １／２ The selection method includes a step of determining material A, material B, x, and y such that

2. The selection method according to claim 1 , wherein the step of obtaining coordinates of intrinsic physical property values ​​based on the Hansen solubility for the scale to be removed includes the step of sampling the scale and obtaining coordinates of the intrinsic physical property values.

3. The selection method according to claim 1, wherein the step of obtaining coordinates of characteristic physical property values ​​based on the Hansen solubility for the scale to be removed includes a step of obtaining coordinates of characteristic physical property values ​​based on elemental analysis of a fluid containing a substance causing scale formation.

4. The selection method according to claim 3 , wherein the elemental analysis method is a method using inductively coupled plasma.

5. A step of selecting a scale dissolving agent based on the method for selecting a scale dissolving agent according to any one of claims 1 to 4; and applying the scale dissolving agent obtained by the selection step to the scale to be removed.

6. In addition to the step of applying the scale dissolving agent to the scale to be removed, the method further includes a step of removing the scale by a physical method, The physical method comprises: A step of applying a temperature change to the scale to be removed to generate a shear force; and / or A step of applying mechanical force to the scale to be removed, including grinding, cutting, peeling, drilling, striking, vibrating, cutting, peeling off, and / or crushing. The method for removing scale according to claim 5, comprising:

7. The scale to be removed includes two or more layers made of different components, the step of selecting a scale dissolving agent includes the step of selecting a scale dissolving agent for each of the two or more layers individually; A scale removal method as described in claim 5 or 6, wherein the step of applying the scale dissolving agent to the scale to be removed includes a step of sequentially applying individually selected scale dissolving agents to the two or more layers, or a step of mixing and preparing individually selected scale dissolving agents and applying them to the two or more layers.

8. A step of selecting a mixed dissolving agent based on the method for selecting a scale dissolving agent according to any one of claims 1 to 4; preparing a mixed dissolution agent; A method for producing a mixed dissolving agent comprising the steps of:

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