Method for producing regenerated inorganic fibers and method for producing catalyst carrier holding mat

Abstract

To provide a method for regenerating inorganic fibers from the discarded material of a catalyst carrier holding mat.SOLUTION: A method for producing regenerated inorganic fibers includes: a cutting step for cutting the discarded material of a catalyst carrier holding mat composed of inorganic fibers; a classifying step for classifying the discarded material; a firing step for firing the discarded material; and a sorting step for sorting the discarded material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing recycled inorganic fibers and a method for producing a catalyst carrier-holding mat. [Background technology]

[0002] Although the recycling rate of on-board parts is increasing year by year, catalyst carrier support mats are typically not recycled when the vehicle they are installed in is scrapped, but are instead disposed of in landfills as industrial waste.

[0003] Similarly, even if a product uses inorganic fibers as a raw material, for example, insulation materials for building materials, there are circumstances such as the fact that they are mainly used covered with a resin cover and that there is a low possibility of contamination during use. For this reason, it has become possible to manufacture new insulation materials by defibrating used insulation materials and mixing them with new inorganic fibers (for example, Patent Document 1).

[0004] It is presumed that the reasons why catalyst carrier support mats are not actively recycled are as follows.

[0005] First, because the catalyst carrier holding mat is used under conditions where vibration and heat are applied, the inorganic fibers are broken and fined over time, the three-dimensional structure of the inorganic fibers is destroyed, and the properties of the inorganic fibers are deteriorated. Therefore, the catalyst carrier holding mat taken out of the used catalytic converter cannot be reused as it is, and in order to reuse it, it is necessary to remove the fine inorganic fibers.

[0006] Furthermore, various impurities may adhere to the used catalyst carrier supporting mat due to external factors. For example, impurities in exhaust gas and precious metal components that have fallen off from the catalyst carrier may be attached. In addition, when recycling a catalyst carrier containing precious metals, the metal case is often cut to extract the catalyst carrier, and metal pieces (cuttings) from cutting the metal case and catalyst carrier pieces may be mixed in. Furthermore, a blanket of glass fiber is often placed around the catalyst carrier holding mat mounted on the vehicle for insulation, and it is not possible to prevent fragments of this blanket of glass fiber and cuttings of the metal case that covers the blanket of glass fiber from being mixed in during the process of recovering the catalyst carrier holding mat.

[0007] For the above reasons, the reality is that no study has yet been conducted on a method for recycling the catalyst support holding mat. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-210289 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above problems, and has an object to provide a method for regenerating inorganic fibers from waste catalyst carrier holding mats. [Means for solving the problem]

[0010] The method for producing recycled inorganic fibers of the present invention is characterized in that it includes a cutting process for cutting waste catalyst carrier holding mats made of inorganic fibers, a classification process for classifying the waste material, a firing process for firing the waste material, and a sorting process for sorting the waste material.

[0011] The waste catalyst support mat refers to discarded catalyst support mat recovered from used catalytic converters or the like. The recovery of the catalyst carrier holding mat is carried out, for example, after disassembling the device in which the catalyst carrier holding mat was used and removing the catalyst carrier. Therefore, when peripheral devices such as a casing are removed or cut in order to remove the catalyst carrier, foreign matter such as cutting chips, catalyst pieces, fragments of blanket-like glass fibers, and rust is likely to be mixed in.

[0012] In this specification, discarded catalyst support holding mats collected from disposal sites, recycling facilities, etc., and mixtures of these without any particular distinction or classification are referred to as "catalyst support holding mat waste (scrap material)." The catalyst support holding mat waste includes, for example, papermaking mat waste and needle mat waste. In addition, the catalyst support holding mat waste may contain foreign matter such as the above-mentioned cutting chips, catalyst pieces, blanket-like glass fiber fragments, and rust.

[0013] In the method for producing recycled inorganic fibers of the present invention, waste materials of catalyst support holding mats made of inorganic fibers (hereinafter simply referred to as waste materials) are subjected to four steps, namely, a cutting step, a classification step, a firing step, and a selection step. The order of the cutting step, the classification step, the firing step, and the selection step is not particularly limited. By carrying out the cutting step, the classification step, the firing step and the sorting step, foreign matter contained in the waste catalyst carrier holding mat can be removed, and recycled inorganic fibers can be obtained.

[0014] The resulting regenerated inorganic fibers can be used for various purposes. Examples of applications of the recycled inorganic fibers include fillers, unshaped refractories, heat insulating materials, and raw materials for catalyst carrier supporting mats.

[0015] Furthermore, the method for producing recycled inorganic fibers of the present invention emits less CO2 compared to producing inorganic fibers from new raw materials because less calcination is performed under high temperature conditions.

[0016] In the method for producing recycled inorganic fibers of the present invention, the cutting step is preferably a rough cutting step in which the waste material is roughly cut into pieces having a size of 30 mm square to 100 mm square. The waste material roughly cut into the above shape is easy to handle.

[0017] In the method for producing recycled inorganic fibers of the present invention, the waste material preferably includes a waste material of a needle mat. Needle mat waste contains a large amount of long-fiber inorganic fibers, so the recovery efficiency of recycled inorganic fibers is high.

[0018] In the method for producing recycled inorganic fibers of the present invention, the classification step preferably includes a first classification step for classifying the waste material, and a second classification step for further classifying the waste material that has been subjected to the first classification step. When the classification process includes a first classification process and a second classification process, the foreign matter can be efficiently removed by adjusting the classification conditions in the first classification process and the second classification process.

[0019] In the method for producing recycled inorganic fibers of the present invention, the first classification step is preferably a step of removing foreign matter having a size of 10 mm or less using a sieve having openings of more than 10 mm. Foreign matter with a size of 10 mm or less includes, for example, metal pieces, catalyst carrier pieces, and inorganic fibers constituting a catalyst carrier holding mat produced by a papermaking method, the organic content of which has already been burned off. The above-mentioned first classification step makes it possible to remove these foreign matters.

[0020] In the method for producing recycled inorganic fibers of the present invention, it is preferable that the firing process is a process carried out after the first classification process and before the second classification process, and is a process for burning off the organic matter contained in the waste material that has been subjected to the first classification process. Foreign matter that exceeds 10 mm in size due to the presence of organic matter cannot be removed by the first classification process described above, but if the firing process is the above process, the organic matter contained in the foreign matter can be burned off, reducing the size of the foreign matter to 10 mm or less, making it possible to remove it.

[0021] In the method for producing recycled inorganic fibers of the present invention, the second classification step is preferably a step for removing inorganic fibers that have been made fine as a result of the organic matter being burned off in the firing step. The catalyst carrier retaining mat may maintain its shape because the inorganic fibers are bound by an organic binder, and if the organic components are not burned off, the shape may exceed 10 mm in size and may not be able to be removed in the first classification process. However, when the second classification process is the above process, the inorganic fibers constituting the catalyst support holding mat can be finely divided by burning off the organic components, thereby making it possible to remove some of the foreign matter that could not be removed in the first classification process.

[0022] In the method for producing recycled inorganic fibers of the present invention, it is preferable that the waste material includes waste papermaking mats, and the second classification process is a process for removing inorganic fibers derived from the papermaking mats that have been finely divided due to the organic matter being burned off in the firing process. In papermaking mats, the shape is maintained by the inorganic fibers being bound by an organic binder. Therefore, if the organic content has not been burned off, papermaking mat waste may contain a large amount of foreign matter that is larger than 10 mm in size and cannot be removed in the first classification process. Even in such a case, the inorganic fibers derived from the paper mat can be removed by using the second classification step.

[0023] In the method for producing recycled inorganic fibers of the present invention, the calcination step is preferably a step of burning off organic matter contained in the waste material. By burning off the organic matter contained in the waste material in the firing step, the organic matter can be removed from the waste material.

[0024] In the method for producing recycled inorganic fibers of the present invention, the calcination step is preferably a step of heating the waste material to a temperature of 800 to 900°C. By setting the heating temperature in the firing step within the above range, the organic matter contained in the waste material can be removed without deteriorating the inorganic fibers. If the heating temperature is less than 800°C, the organic matter contained in the waste material may not be sufficiently removed. If the heating temperature exceeds 900°C, the inorganic fibers that make up the waste material may be deteriorated.

[0025] In the method for producing recycled inorganic fibers of the present invention, the sorting step is preferably a specific gravity separation step in which inorganic fibers and other foreign matter contained in the waste material are separated based on specific gravity. When the sorting step is the specific gravity separation step, foreign matter having a specific gravity significantly different from that of inorganic fibers can be easily removed.

[0026] In the method for producing recycled inorganic fibers of the present invention, the specific gravity separation process is preferably a dry specific gravity separation process in which the waste material is placed on the upper surface of an inclined porous plate, and air is blown from the bottom surface to the top surface of the porous plate while applying vibration, thereby moving materials with relatively high specific gravity to the top of the porous plate and materials with relatively low specific gravity to the bottom of the porous plate. When the specific gravity separation step is the dry specific gravity separation step, substances having a different specific gravity from the inorganic fibers can be easily removed.

[0027] In the manufacturing method of recycled inorganic fibers of the present invention, the waste material contains blanket-like glass fibers in addition to the inorganic fibers constituting the catalyst carrier holding mat, the sorting process is performed after the firing process, and the firing process is a process in which the waste material is heated to a temperature of 800 to 900°C to burn off the organic matter contained in the waste material and to thermally shrink the blanket-like glass fibers to increase their specific gravity, and it is preferable that the sorting process separates the blanket-like glass fibers whose specific gravity has been increased by the firing process. By going through the above steps, blanket-like glass fibers contained as impurities in the waste material can be efficiently removed.

[0028] The method for producing recycled inorganic fibers of the present invention preferably further comprises an acid treatment step of treating the waste material with an acidic solution. By including the acid treatment process, it is easier to remove foreign matter such as metals that could not be separated in the sorting process.

[0029] The method for producing recycled inorganic fibers of the present invention preferably further comprises a wet separation step of wet separating the waste material. The wet separation step can improve the efficiency and accuracy of classification compared to the dry separation step, so that by further providing the wet separation step, short fibers having a short fiber length can be removed with high accuracy, and the quality of the recycled inorganic fibers can be stabilized.

[0030] In the method for producing recycled inorganic fibers of the present invention, the wet separation step is preferably a step of preparing a mixture of the waste material and a solvent, and subjecting the mixture to a centrifugation operation. When the wet separation step is the above-mentioned centrifugal separation operation, inorganic fibers having short fiber lengths can be removed with high accuracy.

[0031] In the method for producing recycled inorganic fibers of the present invention, the wet separation step is preferably a step of preparing a mixture of the waste material and a solvent, and then controlling the pH of the mixture to carry out a flocculation and separation operation. When the wet separation step is the above-mentioned coagulation and separation operation, inorganic fibers having short fiber lengths can be removed with high accuracy. Furthermore, when the waste material contains multiple types of inorganic fibers, different types of inorganic fibers can be separated by utilizing the fact that the pH at which the inorganic fibers aggregate differs depending on the type of inorganic fiber.

[0032] In the manufacturing method of recycled inorganic fibers of the present invention, it is preferable that the cutting process is a process of cutting waste material of a catalyst carrier holding mat made of inorganic fibers, the classification process is a process of classifying the cut waste material, the firing process is a process of firing the classified waste material, and the sorting process is a process of sorting the fired waste material. In the method for producing recycled inorganic fibers of the present invention, it is preferable to first carry out a step of cutting waste material of a catalyst carrier holding mat made of inorganic fibers (cutting step), then a step of classifying the cut waste material (classification step), then a step of calcining the classified waste material (calcining step), and then a step of sorting the calcined waste material (sorting step). By carrying out the cutting step, classification step, firing step and sorting step in this order, foreign matter can be efficiently removed from the waste material.

[0033] The manufacturing method of the catalyst carrier-holding mat of the present invention is characterized by including a step of preparing a slurry containing recycled inorganic fibers obtained by the manufacturing method of recycled inorganic fibers of the present invention, a solvent, and an organic binder, a papermaking step of molding the slurry by a papermaking method to obtain an inorganic fiber aggregate containing the recycled inorganic fibers, and a drying step of drying the inorganic fiber aggregate.

[0034] The recycled inorganic fibers produced by the method for producing recycled inorganic fibers of the present invention emit less CO2 than inorganic fibers produced by conventional methods. Therefore, by using the method for producing a catalyst carrier-holding mat of the present invention, it is possible to reduce CO2 emissions. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a flow chart that illustrates an example of a method for producing recycled inorganic fibers according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view that illustrates an example of a dry gravity separation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention.

[0037] [Manufacturing method of recycled inorganic fibers] The method for producing recycled inorganic fibers of the present invention is characterized in that it includes a cutting process for cutting waste catalyst carrier holding mats made of inorganic fibers, a classification process for classifying the waste material, a firing process for firing the waste material, and a sorting process for sorting the waste material.

[0038] The waste catalyst support mat refers to discarded catalyst support mat recovered from used catalytic converters or the like. The recovery of the catalyst carrier holding mat is carried out, for example, after disassembling the device in which the catalyst carrier holding mat was used and removing the catalyst carrier. Therefore, when peripheral devices such as a casing are removed or cut in order to remove the catalyst carrier, foreign matter such as metal pieces, catalyst pieces, fragments of blanket-like glass fibers, and rust is likely to be mixed in.

[0039] In this specification, discarded catalyst support holding mats collected from disposal sites, recycling facilities, etc., and mixtures of these without any particular distinction or classification are referred to as "catalyst support holding mat waste (scrap material)." The catalyst support holding mat waste includes, for example, papermaking mat waste and needle mat waste. In addition, the catalyst support holding mat waste may contain foreign matter such as the above-mentioned cutting chips, catalyst pieces, blanket-like glass fiber fragments, and rust.

[0040] In the method for producing recycled inorganic fibers of the present invention, waste materials of catalyst support holding mats made of inorganic fibers (hereinafter simply referred to as waste materials) are subjected to four steps, namely, a cutting step, a classification step, a firing step, and a selection step. The order of the cutting step, the classification step, the firing step, and the selection step is not particularly limited. By carrying out the cutting step, the classification step, the firing step and the sorting step, foreign matter contained in the waste catalyst carrier holding mat can be removed, and recycled inorganic fibers can be obtained.

[0041] The cutting step, the classification step, the firing step and the selection step may all be carried out in a batch manner or in a continuous manner.

[0042] The resulting regenerated inorganic fibers can be used for various purposes. Examples of applications of the recycled inorganic fibers include fillers, unshaped refractories, heat insulating materials, and raw materials for catalyst carrier supporting mats.

[0043] Furthermore, the method for producing recycled inorganic fibers of the present invention emits less CO2 compared to producing inorganic fibers from new raw materials, due to reasons such as less calcination under high temperature conditions.

[0044] FIG. 1 is a flow chart that illustrates an example of a method for producing recycled inorganic fibers according to the present invention. In the method for producing recycled inorganic fibers shown in FIG. 1, a cutting step S1, a classification step S2, a firing step S3, and a selection step S4 are carried out on waste catalyst support holding mats in this order.

[0045] That is, the cutting process is a process of cutting waste material of catalyst carrier supporting mat made of inorganic fibers, the classification process is a process of classifying the cut waste material, the firing process is a process of firing the classified waste material, and the sorting process is a process of sorting the fired waste material. By carrying out the cutting step, classification step, firing step and sorting step in this order, foreign matter can be efficiently removed from the waste material.

[0046] However, in the method for producing recycled inorganic fibers of the present invention, the order of the cutting step, the classification step, the firing step, and the selection step is not limited to the order shown in FIG.

[0047] The cutting step, the classification step, the firing step and the selection step will be described in detail below.

[0048] (Cutting process) In the cutting process, the waste material is cut. Shredding waste materials improves their ease of handling.

[0049] The "scrap material" used in the cutting process may be scrap material that has not been subjected to the classification process, firing process, and sorting process, but it may also be scrap material that has been subjected to one or more of the above three processes.

[0050] However, taking into consideration the ease of handling of waste materials in the classification process, firing process, and sorting process, it is preferable that the cutting process be carried out before the classification process and the sorting process, and it is even more preferable that the cutting process be carried out first among the four processes of the cutting process, classification process, firing process, and sorting process. In other words, the cutting step is preferably a step of cutting waste catalyst support holding mats made of inorganic fibers.

[0051] The size of the waste material cut in the cutting step is not particularly limited, but a size of 30 mm to 100 mm is preferable, and a size of 30 mm to 50 mm is more preferable.

[0052] The cutting process in which waste materials are roughly cut into sizes of 30mm to 100mm is also called the rough cutting process. That is, the cutting step is preferably a rough cutting step in which the waste material is roughly cut into pieces having a size of 30 mm to 100 mm square.

[0053] The method for cutting the waste material is not particularly limited, but examples thereof include cutting with a cutting machine, feather mill, crusher, etc.

[0054] (Classification process) In the classification process, foreign matter is removed by taking advantage of size differences.

[0055] The waste material used in the classification step may be waste material that has not been subjected to the cutting step, the firing step, and the sorting step, but may also be waste material that has been subjected to one or more of the above three steps.

[0056] However, in consideration of the ease of handling the waste material in the classification step, the classification step is preferably carried out after the cutting step. In other words, the classification step is preferably a step of classifying the shredded waste material.

[0057] The classification step is preferably a sieving step in which the waste material is sieved using a sieve having a predetermined mesh size.

[0058] The classification step preferably includes a first classification step for classifying the waste material, and a second classification step for further classifying the waste material that has been subjected to the first classification step.

[0059] The first classification step is preferably a step of removing foreign matter having a size of 10 mm or less using a sieve having openings of more than 10 mm square, for example.

[0060] The second classification step is preferably a step of removing foreign matter having a size of 10 mm or less using a sieve having openings of more than 10 mm square, for example.

[0061] (Firing process) In the firing step, the waste material is fired. By calcining the waste material, the organic matter contained in the waste material can be burned off.

[0062] Examples of the organic components include organic binders originally contained in the catalyst carrier holding mat, soot which is a component in exhaust gas, and organic tape (adhesive tape) used to fix the catalyst carrier holding mat and peripheral equipment.

[0063] The waste material used in the firing step may be waste material that has not been subjected to the cutting step, classification step, and sorting step, but may also be waste material that has been subjected to one or more of the above three steps.

[0064] However, in consideration of the ease of handling of waste materials in the firing step, the firing step is preferably carried out after the cutting step.

[0065] Furthermore, from the viewpoint of reducing the energy required for the firing step, it is preferable that the waste material used in the firing step is the waste material from which foreign matter has been removed in the classification step. Therefore, it is preferable that the firing step is performed after the classification step. In other words, the firing step is preferably a step of firing classified waste material.

[0066] However, as a result of the organic matter contained in the waste material being burned away in the firing process, foreign matter that had been maintaining its shape due to the organic matter may become finer. In order to remove such fine foreign matter, a classification step is preferably carried out after the firing step.

[0067] That is, when the classification step includes the above-mentioned first classification step and second classification step, the firing step is preferably carried out after the first classification step and before the second classification step.

[0068] In addition, when the waste material contains inorganic fibers (aggregates) whose shape is maintained by organic matter, the above-mentioned firing process can burn off the organic matter and refine the inorganic fibers (aggregates) in the waste material. Here, if the second classification step is carried out after the firing step, the above-mentioned fine inorganic fibers can be removed.

[0069] That is, the second classification step is preferably a step of removing inorganic fibers that have been made fine as a result of the organic components being burned off in the firing step.

[0070] The paper mat is composed of an aggregate of inorganic fibers in which short inorganic fibers are bound together by organic components. Therefore, when the waste material contains waste papermaking mats, the organic matter can be burned off in the firing step, and the inorganic fibers (aggregates) originating from the papermaking mats in the waste material can be made finer.

[0071] Therefore, the second classification step is preferably a step for removing inorganic fibers derived from the papermaking mat that have been finely divided due to burning off of the organic components in the firing step.

[0072] The firing step is preferably a step of burning off organic matter contained in the waste material, and more preferably a step of heating the waste material to a temperature of 800 to 900°C.

[0073] The atmosphere in the firing step is not particularly limited, but it is preferable to perform firing in air, for example.

[0074] When the waste material contains a blanket of glass fibers, the waste material can be heated to a temperature of 800 to 900°C in a firing process, which burns off the organic matter contained in the waste material and thermally shrinks the blanket of glass fibers, thereby increasing their specific gravity.

[0075] (Sorting process) In the sorting process, foreign matter contained in the waste material is sorted and removed. Here, the selection step does not include the above-mentioned classification step. In addition, the wet separation step described below is not included in the sorting step.

[0076] The waste material used in the sorting step may be waste material that has not been subjected to the cutting step, the classification step, and the firing step, but may also be waste material that has been subjected to one or more of the above three steps.

[0077] However, in consideration of the possibility that the foreign matter may undergo thermal shrinkage during the firing step, resulting in an increase in specific gravity, it is preferable that the sorting step be carried out after the firing step. In other words, the sorting step is preferably a step of sorting out foreign matter contained in the fired waste material.

[0078] The sorting step is preferably a gravity separation step in which inorganic fibers and other foreign matter contained in the waste material are separated based on specific gravity. The gravity separation step is not included in the classification step described above.

[0079] The specific gravity separation process is preferably a dry specific gravity separation process in which waste material is placed on the upper surface of an inclined porous plate, and air is blown from the bottom to the top of the porous plate while applying vibration, thereby moving materials with relatively high specific gravity to the top of the porous plate and materials with relatively low specific gravity to the bottom of the porous plate.

[0080] An example of a dry gravity separation process will be described with reference to FIG. FIG. 2 is a cross-sectional view that illustrates an example of a dry gravity separation process.

[0081] Waste material 1 is placed on a porous plate 10 shown in FIG. The waste material 1 contains low specific gravity material 3 having a relatively low specific gravity and high specific gravity material 5 having a relatively high specific gravity. The shapes of the low specific gravity substance 3 and the high specific gravity substance 5 are not limited to the circular (spherical) shapes shown in FIG.

[0082] The porous plate 10 is inclined at a predetermined angle (θ) from the horizontal direction (the direction in which the dashed line indicated by H in FIG. 2 extends). There is sufficient friction between the surface of the porous plate 10 and the waste material 1. Therefore, the waste material 1 does not naturally move downward along the inclination θ of the porous plate 10.

[0083] The porous plate 10 has numerous holes through which air can pass, and when wind blows from below the porous plate 10, some of the wind reaches the upper surface side of the porous plate 10. Therefore, when air is blown from below the porous plate 10 while the porous plate 10 is vibrated in a direction parallel to the inclination direction (the direction indicated by the double arrow v in Figure 2), the low specific gravity material 3, which has a relatively small specific gravity, is lifted up by the air and moves below the porous plate 10 as it falls. On the other hand, the high-specific-gravity material 5, which has a relatively large specific gravity, is not stirred up by the air blowing, so its position on the porous plate 10 remains unchanged and it does not move downward.

[0084] By the above operation, the low specific gravity material 3 having a relatively small specific gravity is concentrated below the porous plate 10, and the high specific gravity material 5 having a relatively large specific gravity is concentrated above the porous plate 10. This makes it possible to separate the inorganic fibers and other foreign matter contained in the waste material based on the difference in specific gravity. For example, when the waste material contains a blanket of glass fibers in addition to the inorganic fibers constituting the catalyst carrier holding mat, the specific gravity of the thermally shrunk blanket of glass fibers is greater than the specific gravity of the inorganic fibers contained in the waste material. Therefore, by the dry specific gravity separation process, the thermally shrunk blanket of glass fibers is concentrated above the porous plate, and the inorganic fibers contained in the waste material are concentrated below the porous plate.

[0085] The conditions for the dry gravity separation step are not particularly limited, and may be appropriately set so as to separate the inorganic fibers and other foreign matter contained in the waste material.

[0086] The inclination angle of the porous plate can be set appropriately, but is preferably, for example, 5° to 30°.

[0087] The porous plate may be, for example, a mesh or a punched metal.

[0088] The size of the openings in the porous plate may be such that a sufficient amount of air can be supplied from the bottom surface to the top surface of the porous plate and inorganic fibers contained in the waste material do not fall through the openings.

[0089] When the waste material contains a blanket of glass fibers in addition to the inorganic fibers constituting the catalyst carrier holding mat, and the waste material is heated at a temperature of 800 to 900°C in the firing process, the blanket of glass fibers undergoes thermal contraction and has a large specific gravity. Therefore, the specific gravity of the blanket of glass fibers becomes larger than that of the inorganic fibers contained in the waste material, and the inorganic fibers contained in the waste material and the blanket of glass fibers (thermally shrunk) can be separated by the dry specific gravity separation process described above.

[0090] In other words, when the waste material contains blanket-like glass fibers in addition to the inorganic fibers that make up the catalyst carrier holding mat, the sorting process is performed after the firing process, in which the waste material is heated to a temperature of 800 to 900°C to burn off the organic components contained in the waste material and to thermally shrink the blanket-like glass fibers to increase their specific gravity, and in the sorting process, it is preferable to separate the blanket-like glass fibers whose specific gravity has been increased by the firing process.

[0091] In the dry gravity separation step, after removing foreign matter, the fibers constituting the recycled inorganic fibers may be further separated according to their specific gravities. For example, by dividing the recycled inorganic fibers into high specific gravity, medium specific gravity, and low specific gravity recycled inorganic fibers, the specific gravity and therefore the composition of the recycled inorganic fibers can be adjusted.

[0092] The method for producing recycled inorganic fibers of the present invention may include steps other than the cutting step, classification step, firing step, and selection step described above.

[0093] Examples of other steps include an acid treatment step and a wet separation step.

[0094] The method for producing recycled inorganic fibers of the present invention preferably further comprises an acid treatment step of treating the waste material with an acidic solution. By including the acid treatment process, it is easier to remove foreign matter such as metals that could not be separated in the classification and sorting processes.

[0095] The order in which the acid treatment step is carried out is not particularly limited, but it is preferable to carry out the acid treatment step after the cutting step, the classification step and the selection step.

[0096] The acid solution used in the acid treatment step is not particularly limited as long as it reacts with the object to be removed. Examples of the acid solution include hydrochloric acid, nitric acid, and phosphoric acid.

[0097] In general, inorganic fibers have extremely low reactivity with acidic solutions, so it can be said that ordinary acidic solutions do not react with inorganic fibers. On the other hand, cutting chips of metal cases and the like are easily dissolved in acidic solutions, so they can be removed by the acid treatment process.

[0098] After the reaction is completed, the acidic solution is neutralized as necessary, and then filtered and washed with water to separate the acidic solution and foreign matter.

[0099] The method for producing recycled inorganic fibers of the present invention preferably further comprises a wet separation step of wet separating the waste material. The wet separation step is not included in the above-mentioned classification step and selection step. The wet separation process can improve the efficiency and accuracy of classification compared to the dry separation process. Therefore, by further providing the wet separation step, the fiber length distribution of the recycled inorganic fibers can be narrowed, and the quality of the recycled inorganic fibers can be stabilized.

[0100] Examples of the wet separation step include a step of performing a centrifugation operation and a step of performing a flocculation separation operation.

[0101] The wet separation step is preferably a step of preparing a mixed liquid by mixing the waste material with a solvent, and subjecting the mixed liquid to a centrifugation operation. When the wet separation step is the above-mentioned centrifugal separation operation, inorganic fibers having short fiber lengths can be removed with high accuracy.

[0102] The solvent used in preparing the mixture to be centrifuged is not particularly limited, but examples thereof include water and ethanol.

[0103] The centrifugal acceleration in the centrifugation step is not particularly limited, but may be, for example, 1000G to 10000G.

[0104] The wet separation step is preferably a step in which the waste material is mixed with a solvent to prepare a mixed liquid, and then the pH of the mixed liquid is controlled to carry out a flocculation and separation operation. When the wet separation step is the above-mentioned coagulation and separation operation, inorganic fibers having short fiber lengths can be removed with high accuracy.

[0105] By such an operation, for example, inorganic fibers in the waste material can be agglomerated, and the agglomerated inorganic fibers can be separated from components other than the inorganic fibers.

[0106] The pH of the mixture may be appropriately adjusted depending on the type of inorganic fibers to be aggregated. For example, when alumina fibers are to be aggregated, the pH is preferably about 8.5, and when mullite fibers are to be aggregated, the pH is preferably about 7. Under the above conditions, the surface charge (zeta potential) of the inorganic fibers approaches zero, and the electrostatic repulsion between the inorganic fibers weakens, making the inorganic fibers more likely to aggregate.

[0107] As mentioned above, the pH at which precipitation occurs varies depending on the type of inorganic fiber. Therefore, even if the waste material contains multiple types of inorganic fibers, these can be separated by carrying out the coagulation and separation process.

[0108] The solvent used in preparing the mixture for the flocculation and separation operation is not particularly limited, but examples thereof include water and ethanol.

[0109] The pH of the mixture can be controlled, for example, by adding a pH adjuster. Examples of pH adjusters to be added to the mixed solution include acids such as sulfuric acid, hydrochloric acid, and nitric acid, and bases such as sodium hydroxide and potassium hydroxide.

[0110] In addition to the pH adjuster, a flocculant may be added. Adding a flocculant may make flocculation more likely to occur in the mixed liquid. The flocculant may be an inorganic flocculant or a polymer flocculant.

[0111] [Recycled inorganic fibers] Next, the regenerated inorganic fibers obtained by the method for producing regenerated inorganic fibers of the present invention will be described.

[0112] The recycled inorganic fibers obtained by the method for producing recycled inorganic fibers of the present invention are inorganic fibers separated from waste catalyst support holding mats, and are preferably composed of inorganic fibers having a fiber length of 0.1 mm to 20 mm.

[0113] The average fiber length of the recycled inorganic fibers is preferably 0.1 mm to 20 mm. The average fiber diameter of the recycled inorganic fibers is preferably 3 μm to 10 μm.

[0114] The type of inorganic fiber constituting the recycled inorganic fiber may be only one type, or two or more types of inorganic fibers may be included.

[0115] [Method of manufacturing the catalyst carrier holding mat] The manufacturing method of the catalyst carrier-holding mat of the present invention is characterized by including a step of preparing a slurry containing recycled inorganic fibers obtained by the manufacturing method of recycled inorganic fibers of the present invention, a solvent, and an organic binder, a papermaking step of molding the slurry by a papermaking method to obtain an inorganic fiber aggregate containing the recycled inorganic fibers, and a drying step of drying the inorganic fiber aggregate.

[0116] [Slurry preparation process] The slurry includes recycled inorganic fibers, a solvent, and an organic binder. As the solvent, for example, water can be used. As the organic binder, for example, an acrylic resin or the like can be used. If necessary, a dispersant, a flocculant, etc. may be added to the slurry.

[0117] The present invention relates to a regenerated inorganic fiber and a regenerated inorganic fiber obtained by the method for producing a regenerated inorganic fiber of the present invention. The length of the recycled inorganic fibers may be adjusted by cutting or the like, if necessary.

[0118] [Paper making process] Next, the slurry is molded by a papermaking method to obtain an inorganic fiber aggregate. For example, the slurry is poured into a molding machine having a filtering mesh formed on the bottom thereof, and the solvent in the slurry is then removed through the mesh to produce an inorganic fiber aggregate.

[0119] [Drying process] Subsequently, the obtained inorganic fiber aggregate is dried. The drying temperature is preferably 100 to 250°C. The inorganic fiber aggregate may be dried while being compressed. The inorganic fiber aggregate can be compressed using a press or the like. Drying may be performed simultaneously with pressing by using the press plate of the press machine as a hot plate and setting the temperature of the hot plate to a high temperature (for example, 100° C. to 250° C.).

[0120] By the above steps, a catalyst carrier-holding mat can be produced using the recycled inorganic fibers of the present invention as a raw material. The recycled inorganic fibers produced by the method for producing recycled inorganic fibers of the present invention emit less CO2 than inorganic fibers produced by conventional methods. Therefore, by using the method for producing a catalyst carrier-holding mat of the present invention, it is possible to reduce CO2 emissions.

[0121] The present specification describes the following inventions:

[0122] The present disclosure (1) relates to a waste material of a catalyst carrier holding mat made of inorganic fibers, The method for producing recycled inorganic fibers includes a cutting step of cutting the waste material, a classification step of classifying the waste material, a firing step of firing the waste material, and a sorting step of sorting the waste material.

[0123] The present disclosure (2) is the method for producing recycled inorganic fibers according to the present disclosure (1), wherein the cutting step is a rough cutting step of roughly cutting the waste material into pieces having a size of 30 mm to 100 mm square.

[0124] The present disclosure (3) is a method for producing recycled inorganic fibers according to the present disclosure (1) or (2), in which the waste material includes a waste material of a needle mat.

[0125] The present disclosure (4) is a method for producing recycled inorganic fibers in any combination with any of the present disclosures (1) to (3), wherein the classification process includes a first classification process for classifying the waste material and a second classification process for further classifying the waste material that has been subjected to the first classification process.

[0126] The present disclosure (5) is a method for producing recycled inorganic fibers described in the present disclosure (4), in which the first classification process is a process for removing foreign matter having a size of 10 mm or less using a sieve with a mesh size of more than 10 mm.

[0127] The present disclosure (6) is a method for producing recycled inorganic fibers according to the present disclosure (4) or (5), in which the firing process is carried out after the first classification process and before the second classification process, and is a process for burning off organic matter contained in the waste material that has been subjected to the first classification process.

[0128] The present disclosure (7) is a method for producing recycled inorganic fibers in any combination with any of the present disclosures (4) to (6), in which the second classification process is a process for removing inorganic fibers that have been finely divided due to the burning off of organic components in the firing process.

[0129] The present disclosure (8) relates to a method for manufacturing a papermaking mat, wherein the waste material includes a papermaking mat waste material, The second classification process is a process for removing inorganic fibers derived from the papermaking mat that have been refined as a result of the organic components being burned off in the firing process. This is a method for producing recycled inorganic fibers, which can be arbitrarily combined with any of the present disclosures (4) to (7).

[0130] The present disclosure (9) is a method for producing recycled inorganic fibers in any combination with any of the present disclosures (1) to (8), wherein the firing step is a step of burning off organic matter contained in the waste material.

[0131] The present disclosure (10) is the method for producing recycled inorganic fibers according to the present disclosure (9), wherein the firing step is a step of heating the waste material to a temperature of 800 to 900°C.

[0132] The present disclosure (11) is a method for producing recycled inorganic fibers, which is any combination with any of the present disclosures (1) to (10), wherein the sorting process is a specific gravity separation process for separating inorganic fibers and other foreign matter contained in the waste material based on specific gravity.

[0133] The present disclosure (12) is a method for producing recycled inorganic fibers according to the present disclosure (11), wherein the specific gravity separation process is a dry specific gravity separation process in which the waste material is placed on the upper surface of an inclined porous plate, and air is blown from the bottom surface to the top surface of the porous plate while applying vibration, thereby moving substances having a relatively high specific gravity to the top of the porous plate and moving substances having a relatively low specific gravity to the bottom of the porous plate.

[0134] The present disclosure (13) relates to a method for manufacturing a catalyst carrier support mat, and further relates to a method for manufacturing the catalyst carrier support mat. The sorting step is carried out after the firing step, The firing step is a step of heating the waste material to a temperature of 800 to 900° C. to burn off organic matter contained in the waste material and to thermally shrink the blanket-like glass fiber to increase its specific gravity; In the method for producing recycled inorganic fibers according to the present disclosure (12), in the sorting step, the blanket-like glass fibers whose specific gravity has increased due to the firing step are separated.

[0135] The present disclosure (14) is a method for producing recycled inorganic fibers in any combination with any of the present disclosures (1) to (13), further comprising an acid treatment step of treating the waste material with an acidic solution.

[0136] The present disclosure (15) is a method for producing recycled inorganic fibers in any combination with any of the present disclosures (1) to (14), further comprising a wet separation step of wet-separating the waste material.

[0137] The present disclosure (16) is the method for producing recycled inorganic fibers according to the present disclosure (15), wherein the wet separation step is a step of preparing a mixture of the waste material and a solvent and subjecting the mixture to a centrifugation operation.

[0138] The present disclosure (17) is a method for producing recycled inorganic fibers according to the present disclosure (15), wherein the wet separation process is a process for preparing a mixture of the waste material and a solvent, and then controlling the pH of the mixture to perform a coagulation and separation operation.

[0139] The present disclosure (18) is a process for cutting a waste material of a catalyst carrier holding mat made of inorganic fibers, The classification step is a step of classifying the cut waste material, The firing step is a step of firing the classified waste material, The method for producing recycled inorganic fibers in any combination with any of the present disclosures (1) to (17), wherein the sorting step is a step of sorting the burned waste material.

[0140] The present disclosure (19) provides a method for producing a recycled inorganic fiber, comprising the steps of: preparing a slurry containing recycled inorganic fibers obtained by a method for producing a recycled inorganic fiber in any combination with any of the present disclosures (1) to (18); a solvent; and an organic binder; a papermaking process for forming the slurry by a papermaking method to obtain an inorganic fiber aggregate containing the recycled inorganic fibers; and a drying step of drying the inorganic fiber aggregate.

[0141] An example of the method for producing the recycled inorganic fibers of the present invention will be described below.

[0142] (Process 1: Cutting process) First, a cutting process is performed on a waste catalyst carrier holding mat made of inorganic fibers. The cutting process is a rough cutting process in which waste materials are roughly cut into pieces measuring 30mm to 100mm square. By going through the rough cutting process, the waste material is reduced in size to 30mm to 100mm, making it easier to handle. The waste materials used here include waste needle mats and waste papermaking mats, and contain foreign matter such as cutting chips, catalyst pieces, blanket-like glass fibers, and rust.

[0143] (Process 2: 1st classification process) Next, the waste material that has gone through the cutting process is subjected to the first classification process, which is a classification process. In the first classification process, a sieve with mesh size of more than 10 mm is used to remove foreign matter smaller than 10 mm. Through the first classification process, foreign objects with a size of 10 mm or less are removed from the waste material. Here, foreign objects such as cutting chips and metal pieces are removed.

[0144] (Step 3: Firing step) Next, the waste material that has gone through the first classification process is subjected to a firing process. In the firing process, the waste material that has gone through the first classification process is heated in the atmosphere at a temperature of 800 to 900°C for one hour. The burning process burns off the organic matter contained in the waste material, and the fabric-like glass fiber shrinks due to heat, increasing its specific gravity. The burning off of the organic matter contained in the waste material causes the inorganic fibers derived from the paper mat to become finer.

[0145] (Process 4: 2nd classification process) Next, the waste material that has undergone the firing process undergoes a second classification process. In the second classification process, a sieve with mesh size greater than 10 mm is used to remove foreign matter smaller than 10 mm. The classification conditions in the second classification process are the same as those in the first classification process, but the inorganic fibers derived from the paper mat have become finer due to the firing process, and these are removed in the second classification process.

[0146] (Step 5: Sorting step) Finally, the waste material that has gone through the second classification process undergoes a sorting process. In the sorting process, a dry gravity separation process as shown in FIG. 2 is carried out. By carrying out the dry gravity separation process, it is possible to separate the blanket-like glass fibers whose specific gravity has increased due to thermal shrinkage in the firing process. Specifically, for example, after the dry specific gravity separation process is completed, the waste material that has fallen from the downstream side of the porous plate and the waste material that is located in the downstream 1 / 3 of the porous plate can be collected to obtain recycled inorganic fibers.

[0147] Through the above steps, recycled inorganic fibers can be obtained from waste needle mats, waste papermaking mats, and waste catalyst carrier supporting mats containing blanket-like glass fibers. [Explanation of symbols]

[0148] 1. Waste catalyst carrier support mat 3 Low specific gravity substances 5 High density substances 10 Porous Plate S1 Cutting process S2 Classification process S3 Firing process S4 Sorting process

Claims

1. For waste catalyst carrier support mats made of inorganic fibers, A method for producing recycled inorganic fibers, comprising the steps of: cutting the waste material in a cutting step; classifying the waste material in a classifying step; calcining the waste material in a calcining step; and sorting the waste material in a sorting step.

2. The method for producing recycled inorganic fibers according to claim 1 , wherein the cutting step is a rough cutting step for roughly cutting the waste material into pieces having a size of 30 mm to 100 mm.

3. The method for producing recycled inorganic fibers according to claim 1 , wherein the waste material includes a waste needle mat.

4. The method for producing recycled inorganic fibers according to claim 1 , wherein the classification step includes a first classification step of classifying the waste material, and a second classification step of further classifying the waste material that has been subjected to the first classification step.

5. The method for producing recycled inorganic fibers according to claim 4, wherein the first classification step is a step of removing foreign matter having a size of 10 mm or less using a sieve having a mesh size of more than 10 mm.

6. The method for producing recycled inorganic fibers according to claim 5, wherein the firing process is carried out after the first classification process and before the second classification process, and is a process for burning off organic matter contained in the waste material that has been subjected to the first classification process.

7. The method for producing recycled inorganic fibers according to claim 6 , wherein the second classification step is a step of removing inorganic fibers that have been made fine by burning off an organic component in the firing step.

8. The waste material includes waste paper mats, The method for producing recycled inorganic fibers according to claim 7 , wherein the second classification step is a step for removing inorganic fibers derived from the papermaking mat that have been finely divided due to burning off of organic matter in the firing step.

9. The method for producing recycled inorganic fibers according to claim 1 , wherein the firing step is a step of burning off organic matter contained in the waste material.

10. The method for producing recycled inorganic fibers according to claim 9, wherein the firing step is a step of heating the waste material to a temperature of 800 to 900°C.

11. The method for producing recycled inorganic fibers according to claim 1 , wherein the sorting step is a specific gravity separation step in which inorganic fibers and other foreign matter contained in the waste material are separated based on specific gravity.

12. The method for producing recycled inorganic fibers according to claim 11, wherein the specific gravity separation process is a dry specific gravity separation process in which the waste material is placed on the upper surface of an inclined porous plate, and air is blown from the bottom surface to the top surface of the porous plate while applying vibration, thereby moving substances with relatively high specific gravity to the top of the porous plate and materials with relatively low specific gravity to the bottom of the porous plate.

13. The waste material includes a blanket of glass fibers in addition to the inorganic fibers constituting the catalyst carrier holding mat, The sorting step is carried out after the firing step, The firing step is a step of heating the waste material to a temperature of 800 to 900° C. to burn off organic matter contained in the waste material and to thermally shrink the blanket-like glass fiber to increase its specific gravity; The method for producing recycled inorganic fibers according to claim 12 , wherein the sorting step separates the blanket-like glass fibers having a high specific gravity due to the firing step.

14. The method for producing recycled inorganic fibers according to claim 1 , further comprising an acid treatment step of treating the waste material with an acidic solution.

15. The method for producing recycled inorganic fibers according to claim 1 , further comprising a wet separation step of wet separating the waste material.

16. The method for producing recycled inorganic fibers according to claim 15, wherein the wet separation step is a step of preparing a mixed liquid of the waste material and a solvent, and subjecting the mixed liquid to a centrifugal separation operation.

17. The method for producing recycled inorganic fibers according to claim 15, wherein the wet separation step is a step of preparing a mixed liquid of the waste material and a solvent, and then controlling the pH of the mixed liquid to carry out a coagulation and separation operation.

18. The cutting step is a step of cutting a waste material of a catalyst carrier holding mat made of inorganic fibers, The classification step is a step of classifying the cut waste material, The firing step is a step of firing the classified waste material, The method for producing recycled inorganic fibers according to claim 1 , wherein the sorting step is a step of sorting the burned waste material.

19. A step of preparing a slurry containing recycled inorganic fibers obtained by the method for producing recycled inorganic fibers according to any one of claims 1 to 18, a solvent, and an organic binder; a papermaking process for forming the slurry by a papermaking method to obtain an inorganic fiber aggregate containing the recycled inorganic fibers; and drying the inorganic fiber aggregate.

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