Adsorption element, adsorption rotor, and adsorption processing device

Abstract

Provided is an adsorption element which has a honeycomb structure formed by an adsorption sheet containing an adsorbent, wherein a differential thermogravimetric curve has, in the range of 350-500°C, a minimum value (% / °C) of not more than -0.005% / °C, and the honeycomb structure has 80-135 cells / cm2

Description

Adsorption element, adsorption rotor, and adsorption treatment device

[0001] The present invention relates to an adsorption element, an adsorption rotor, and an adsorption treatment device used in an adsorption treatment device for adsorbing and removing harmful components such as organic solvents contained in a gas to be treated.

[0002] Conventionally, an adsorption element has been known in which an adsorption sheet containing an adsorbent, organic fibers, an organic binder, and an inorganic binder is molded into a honeycomb shape. For example, Patent Document 1 discloses an adsorption element in which zeolite is used as an adsorbent and processed into a honeycomb shape.

[0003] Patent Document 2 discloses an adsorption treatment device having adsorption elements. In this adsorption treatment device, the adsorption elements are arranged circumferentially to form a cylindrical adsorption rotor, and the arranged adsorption elements are divided into an adsorption zone and a desorption zone. In the adsorption zone, the treated gas containing organic solvents is adsorbed by the adsorbent, and the purified gas is discharged outside the system. Meanwhile, in the desorption zone, the organic solvent adsorbed by the adsorption elements is transferred to a heated gas to restore the adsorption capacity of the adsorption elements, and the gas containing the organic solvent is discharged as a high-concentration gas. The adsorption rotor on which the adsorption elements are arranged is equipped with a rotation mechanism, and the adsorption and desorption processes are performed continuously by rotating circumferentially. In this device, the adsorption elements are packed and mounted in a block case. Patent Document 3 discloses an adsorption treatment device that can be stably transported and rotated to increase adsorption capacity.

[0004] JP 2004-268020 A JP 2019-209269 A International Publication No. 2017 / 170207

[0005] There is a need to further improve the treatment performance of organic solvents in conventional adsorption treatment devices. One possible way to meet this need is to increase the amount of adsorbent packed per block case. Increasing the amount of adsorbent per block case increases the organic solvent adsorption capacity and also improves the contact efficiency between the adsorbent and the organic solvent, thereby improving the treatment performance of the organic solvent.

[0006] However, this method has the problem that when the block case is packed with adsorption elements, the honeycomb structure collapses due to insufficient mechanical strength of the adsorption elements, resulting in a significant increase in pressure loss. While one method of increasing the mechanical strength of the adsorption elements is to solidify them with resin or the like, this can lead to problems such as the pores of the adsorbent being blocked by the resin, causing a decrease in the performance of the adsorption elements, and the honeycomb structure itself being blocked.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide an adsorption element or the like that maintains adsorption performance and has sufficient mechanical strength.

[0008] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention has the following configuration: 1. An adsorption element having a honeycomb structure formed from an adsorption sheet containing an adsorbent, in which the minimum value (% / °C) of the differential thermogravimetric curve in the range of 350°C to 500°C is -0.005% / °C or less, and the number of cells in the honeycomb structure is 80 cells / cm ２ More than 135 pieces / cm ２ An adsorption element as set forth below. 2. The adsorption element as set forth in 1 above, wherein the adsorbent is at least one of zeolite, activated carbon, and metal-organic framework (MOF). 3. The adsorption element as set forth in 1 or 2 above, wherein the content of the adsorbent is 60% by weight to 85% by weight, when the entire adsorption element is taken as 100% by weight. 4. The adsorption element as set forth in any one of 1 to 3 above, wherein the adsorption element has a planar compressive strength of 23 kPa or more. 5. The adsorption element as set forth in any one of 1 to 4 above, wherein the adsorption element has a vertical compressive strength of 55 kPa or more. 6. An adsorption rotor as set forth in any one of 1 to 5 above, which is rotatable in a circumferential direction. 7. An adsorption treatment device as set forth in 6 above, which is equipped with the adsorption rotor as set forth in 6 above, and which performs adsorption treatment by flowing a gas to be treated into the adsorption element.

[0009] The present invention makes it possible to provide an adsorption element having sufficient mechanical strength and excellent adsorption performance.

[0010] Fig. 1 is a diagram showing an adsorption element according to an embodiment of the present invention. Fig. 2 is another diagram showing an adsorption element according to an embodiment of the present invention. Fig. 3 is a diagram showing measurement results of Example 1 and Comparative Example 1. Fig. 4 is a diagram showing graphs of thermal derivative curves of Example 1 and Comparative Example 1.

[0011] An adsorption element according to an embodiment of the present invention will be described below with reference to the drawings. In the embodiments described below, when reference is made to the number, amount, etc., the scope of the present invention is not necessarily limited to that number, amount, etc., unless otherwise specified. The same reference numerals are used for identical or corresponding parts, and redundant descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments will be used in appropriate combinations. In this specification, the notations "A to Z" and "A to Z" refer to the upper and lower limits of a range (i.e., from A to Z). When no unit is specified for A and only a unit is specified for Z, the unit of A and the unit of Z are the same.

[0012] [Adsorption Element Structure] As shown in FIGS. 1 and 2 , the adsorption element 1 in this embodiment has a honeycomb structure composed of a corrugated sheet 1a and a liner sheet 1b, allowing gas to pass through the adsorption element. A honeycomb structure generally refers to a three-dimensional structure composed of multiple small spaces (cells) surrounded by side walls. The adsorption element 1 preferably has a honeycomb structure from the viewpoints of maintaining mechanical strength and reducing manufacturing costs. The adsorption element 1 includes a corrugated sheet 1a and a liner sheet 1b stacked in a block case (frame) as shown in FIG. 3 . As shown in FIG. 3 , the adsorption element 1 receives a pre-passage gas F1 and discharges a post-passage gas F2. The corrugated sheet 1a and the liner sheet 1b are composed of an adsorption sheet containing an adsorbent. Examples of the adsorbent include activated alumina, silica gel, activated carbon, zeolite, and a metal-organic framework (MOF). The adsorbent is preferably at least one of zeolite, activated carbon, and a metal-organic framework (MOF).

[0013] In the adsorption element 1, the number of cells in the honeycomb structure is 80 / cm ２~135 pieces / cm ２ The number of cells is preferably 80 / cm. ２ If the number of cells is less than 135 / cm, the adsorption element will not be able to achieve sufficient adsorption performance. ２ If the thickness exceeds this value, it will be necessary to reduce the thickness of the adsorption sheet that constitutes the partition walls of the honeycomb structure, and the mechanical strength of the adsorption sheet will be weakened, making it difficult to manufacture the adsorption sheet. The cell shape of the honeycomb structure is not particularly specified, but taking the honeycomb structure of Figure 2 as an example, it is preferable that the wave height be 0.7 mm to 1.1 mm and the wavelength be 1.8 mm to 2.6 mm.

[0014] The partition wall thickness of the honeycomb structure constituting the honeycomb structure constituting the adsorption element 1 is preferably 0.16 mm to 0.25 mm. If the partition wall thickness is less than 0.16 mm, the thickness of the adsorption sheet constituting the partition wall needs to be made thinner, but the mechanical strength of the adsorption sheet is weakened, making it impossible to manufacture the adsorption sheet. If the partition wall thickness exceeds 0.25 mm, the partition wall becomes too thick and the density of the partition walls is reduced to 80 / cm. ２ You cannot get more than this number of cells.

[0015] The basis weight of the adsorption sheet constituting the adsorption element 1 is 65 g / m ２ ~90g / m ２ The basis weight of the adsorption sheet is preferably 65 g / m ２ If the basis weight of the adsorption sheet is less than 90 g / m, the mechanical strength of the adsorption sheet will be weakened, and the mechanical strength of the adsorption element having a honeycomb structure after the heat treatment will not be maintained. ２ When the thickness exceeds 80 cells / cm, the partition walls of the honeycomb structure become thick. ２ You cannot get more than this number of cells.

[0016] [Method for Manufacturing Adsorption Element] The following method can be used to manufacture the adsorption element 1 in this embodiment. A honeycomb-shaped material (precursor element) is manufactured by molding a sheet-like material containing an adsorbent, a heat-resistant organic component, and a thermally decomposable organic component into a honeycomb shape using a honeycomb-forming adhesive. The precursor element is then heat-treated (fired) at a temperature below the melting point or decomposition temperature of the heat-resistant organic component and above the decomposition temperature of the thermally decomposable organic component, causing thermal oxidative decomposition of the thermally decomposable organic component contained in the precursor element, converting most of the precursor element into oxides, thereby manufacturing an adsorption element 1 with excellent mechanical strength.

[0017] The method for manufacturing the adsorption element 1 will now be described in more detail.

[0018] [Sheet-like material] The sheet-like material can be obtained by mixing and papermaking an adsorbent and a skeletal material. Examples of a method for mixing and papermaking a sheet-like material include a wet papermaking method. This sheet-like material becomes the adsorbent sheet in the adsorption element 1 by heat treatment.

[0019] [Adsorbent] Examples of the adsorbent include activated alumina, silica gel, activated carbon, zeolite, and metal-organic framework (MOF). Among these, the adsorbent is preferably at least one of zeolite, activated carbon, and metal-organic framework (MOF) from the viewpoint of improving the adsorption performance of the adsorption element. When wet papermaking is performed as the mixed papermaking process to obtain a sheet-like material, the adsorbent is preferably in powder or granular form, more preferably in powder form. When activated carbon is used as the adsorbent, the adsorbent is preferably a powder having an average particle size of 10 μm to 50 μm, or a fiber having an average fiber diameter of 10 μm to 30 μm. The raw material for the activated carbon is not particularly specified, but examples include coconut stalk, coal, pitch, phenolic resin, polyacrylonitrile, cellulose, etc.

[0020] Zeolite is preferred as the adsorbent. Zeolite has a high heat resistance temperature and is less reactive with organic solvents during adsorption than activated carbon, so there is less risk of heat generation. Zeolite also has a sharper pore structure than activated carbon, so it has excellent adsorption performance for organic solvents and the like. When using zeolite as the adsorbent, the adsorbent is preferably a powder with an average particle size of 1 μm or more and 20 μm or less. Suitable zeolites include naturally occurring zeolites and artificially synthesized zeolites, such as beta type, ZSM-5 type, ferrierite type, mordenite type, L type, Y type, and A type.

[0021] The adsorbent is preferably a high-silica zeolite with a high silica / alumina ratio. This is because high-silica zeolite is less susceptible to the moisture and humidity in the gas to be treated when adsorbing organic solvents and the like from the gas to be treated. The silica / alumina ratio is preferably 15 or more, and more preferably 50 or more.

[0022] The adsorption element 1 includes at least one adsorbent. When multiple adsorbents are selected, the ratio of the adsorbents is not particularly limited. The adsorbents may be selected appropriately depending on the treatment conditions of the gas to be treated.

[0023] [Organic Component] (Heat-Resistant Organic Component) In this embodiment, organic fibers, which are heat-resistant organic components, are used as a framework material that supports the adsorbent during the production of the sheet-like material and after molding. The heat-resistant organic component is preferably a pulp-like or short-fiber organic fiber with a fiber length of approximately 10 mm or less. The heat-resistant organic component is preferably a fiber with excellent heat resistance, having a melting point or thermal decomposition temperature of 300°C or higher. If the melting point or thermal decomposition temperature of the heat-resistant organic component is less than 300°C, a significant decrease in strength of the adsorption element will be unavoidable under the high temperatures encountered during adsorption / desorption operations. Specific examples of organic fibers include fibers made from aramid, meta-aramid, polybenzimidazole (PBI), polybenzoxazole (PBO), polyimide, polyamide-imide, polyether ketone, etc.

[0024] (Thermal Decomposable Organic Component) The sheet-shaped material preferably contains, as an organic component, an organic binder, which is a thermally decomposable organic component having a thermal decomposition temperature of less than 300°C, in addition to organic fibers, which are heat-resistant organic components. The organic binder acts to support a high proportion of the adsorbent on the sheet during production of the sheet-shaped material. Examples of organic binders include PVA (polyvinyl alcohol), starch, and polyacrylonitrile, with PVA being preferred.

[0025] The organic binder may cover the adsorbent to a large extent, which may cause a decrease in adsorption performance. Therefore, it is preferable that the organic binder cover the adsorbent to a small extent in the adsorption sheet. A method for reducing the organic binder's coverage of the adsorbent is to convert the organic binder into an oxide or carbide, or to decompose and eliminate the organic binder. More preferably, the organic binder is converted into an oxide. By converting the organic binder into an oxide, the mechanical strength of the adsorption element can be improved. Note that when the organic binder is converted into a carbide or decomposed and eliminated, the functional groups of the organic binder are reduced, which may reduce the adhesion to the adsorbent and cause the adsorbent to be detached.

[0026] [Adhesive Component] The sheet-like material of this embodiment may contain an adhesive component in addition to the adsorbent, heat-resistant organic component, and thermally decomposable organic component. The adhesive component can fix and maintain the adsorbent and skeletal material in the sheet-like material during heat treatment. An inorganic binder can be used as the adhesive component. Furthermore, an inorganic binder can also be used as the adhesive component that fixes and maintains the corrugated sheet 1a and liner sheet 1b that form the honeycomb structure.

[0027] The inorganic binder is soluble in water, uniformly dispersed in the sheet, and hardens by reaction and gelation during heat treatment, serving to firmly fix the adsorbent and the framework during hardening. The inorganic binder preferably has a thermal decomposition temperature of 300°C or higher, generates reaction heat with highly reactive organic solvents, has low catalytic activity that could cause the sheet to ignite or burn, and is unlikely to reduce the adsorption performance of the adsorbent due to its coating. Examples of inorganic binders include phosphate-based binders such as sodium hexametaphosphate and silicate-based binders such as sodium silicate.

[0028] The adhesive component that fixes and maintains the adsorbent and skeletal material together and the adhesive component that fixes and maintains the corrugated sheet 1a and liner sheet 1b together may be the same or different, and an appropriate binder may be selected.

[0029] [Adsorbent Content] Taking into consideration the adsorption performance, productivity, and adsorbent shedding, the adsorbent content in the adsorption element 1 is preferably 60% by weight or more, where 100% by weight is the entire adsorption element. If the adsorbent content is less than 60% by weight, the adsorption element will not exhibit sufficient adsorption performance. There is no upper limit on the weight of the adsorbent, but from the viewpoint of maintaining the shape of the adsorption element, 85% by weight or less is preferred. If the adsorbent content exceeds 85% by weight, the adsorption sheet will lack flexibility and will be difficult to process.

[0030] The content of the adhesive component in the adsorption element 1 is 5 to 30% by weight, where the entire adsorption sheet is taken as 100% by weight. If it is less than 5% by weight, the adhesion between the adsorbent and the framework material will be poor, and if it exceeds 30% by weight, the flexibility of the adsorption sheet will be insufficient, which is undesirable.

[0031] [Heat Treatment] The adsorption element 1 can be obtained by subjecting a precursor element, which is a honeycomb-shaped sheet material, to heat treatment. Heat treatment is preferably carried out in an air atmosphere using a heating oven or the like. The heat treatment temperature is preferably below the melting point or decomposition temperature (T1°C) of the heat-resistant organic component, more preferably 5°C to 20°C lower than T1°C, or preferably above the decomposition temperature (T2°C) of the thermally decomposable organic component, more preferably 5°C to 20°C higher than T2°C. The treatment time can be selected as appropriate, but it is preferable to select temperature conditions and time such that the minimum value of the differential thermogravimetric curve described below in the adsorption element is −0.005% / °C or less. This heat treatment oxidizes the organic binder, which is the thermally decomposable organic component, to form an oxide, thereby increasing the mechanical strength of the adsorption element 1.

[0032] After the heat treatment, the adsorption element 1 exhibits a small minimum value in the differential thermogravimetric curve in the range of 350° C. to 500° C. due to the presence of oxides of the thermally decomposable organic components contained in the adsorption element. In the present invention, thermogravimetric measurement is performed in a nitrogen atmosphere, and the minimum value is defined as the smallest peak in the differential thermogravimetric curve in the range of 350° C. to 500° C.

[0033] From the viewpoint of improving the mechanical strength of the adsorption element 1, the minimum value of the differential thermogravimetric curve is -0.005% / °C or less, and preferably -0.006% / °C or less. If the minimum value of the differential thermogravimetric curve is greater than -0.005% / °C, the amount of oxides of the thermally decomposable organic components is small, resulting in a decrease in mechanical strength, which may cause the honeycomb structure to collapse when the block case is filled. There is no particular lower limit for the minimum value of the differential thermogravimetric curve, but it may be, for example, -0.015% / °C or more.

[0034] The planar compressive strength of the adsorption element 1 is preferably 23 kPa or more. If the planar compressive strength is less than 23 kPa, the adsorption element is easily crushed, and many air passages are crushed and lost, resulting in a loss of performance as an adsorption element and making it impractical.

[0035] The vertical compressive strength of the adsorption element 1 is preferably 55 kPa or more. If the vertical compressive strength is less than 55 kPa, the adsorption element is easily crushed, and many air passages are crushed and lost, which makes the adsorption element impractical because it does not perform as expected.

[0036] The scope of the present application also includes an adsorption rotor using the adsorption element of this embodiment and an adsorption treatment device equipped with this adsorption rotor. This adsorption treatment device can perform adsorption treatment by flowing the gas to be treated into the adsorption element. The shape of the adsorption rotor is not limited, and it may be a vertically placed cylindrical shape, a horizontally placed cylindrical shape, or a disk shape. The adsorption rotor using the adsorption element of this embodiment can rotate in the circumferential direction.

[0037] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for evaluating physical properties and the like are as follows.

[0038] (1) Minimum Value of Derivative Thermogravimetric Curve Using a thermal analyzer (product name STA7000, manufactured by Hitachi High-Tech Corporation), 10 mg of sample was packed into a platinum pan and heated from 35°C to 1050°C at 5°C / min under a nitrogen atmosphere. Thermogravimetric measurement was performed to obtain a thermogravimetric change curve (TG curve) with temperature (°C) on the x-axis and the rate of thermogravimetric change (%) on the y-axis. Furthermore, a differential thermogravimetric curve (DTG curve, unit: % / °C) was obtained by differentiating the TG curve. The differential thermogravimetric curve shows a positive value when the thermogravimetric value of the sample increases and a negative value when the thermogravimetric value of the sample decreases. In the range from 350°C to 500°C, the smallest numerical peak of the differential thermogravimetric curve was determined as the minimum value (% / °C) of the differential thermogravimetric curve. The smaller this value, the more oxide of the organic binder is contained.

[0039] (2) Planar Compression Strength A set of suction sheets consisting of a corrugated sheet and a liner sheet cut into a 3 cm x 3 cm surface was compressed in the planar direction at 0.2 mm / min, and the stress value at the elastic limit was measured. This stress value was taken as the compressive strength in the planar direction of the suction element. The height of the set of suction sheets at this time was 0.1 cm.

[0040] (3) Vertical Compression Strength Five pairs of suction sheets, each consisting of a corrugated sheet and a liner sheet cut into 3 cm x 3 cm pieces, were stacked and compressed at 1 mm / min from the direction of ventilation to measure the stress value at the elastic limit. This stress value was taken as the vertical compression strength of the suction element. The height of the five stacked suction sheets was 0.6 cm.

[0041] [Example 1] 37.5 wt% of ZSM-5 (MFI) zeolite and 37.5 wt% of Y-type (FAU) zeolite were used as adsorbents, 17 wt% of pulp-like and short fiber-like aramid fibers were used as organic fibers that are heat-resistant organic components, and 8 wt% of PVA was used as an organic binder that is a thermally decomposable organic component. The mixture was then used in a wet papermaking machine to make a paper with a basis weight of 75 g / m. ２ A sheet-like material was prepared.

[0042] Next, the sheet-like material was immersed in a 7 wt % aqueous solution of sodium hexametaphosphate, which is an adhesive component, and dried in air at 100°C to obtain a precursor sheet in which 5 wt % sodium hexametaphosphate was fixed to the sheet-like material.

[0043] Next, the precursor sheet was molded into a honeycomb molding machine using an acrylic emulsion with a solid content of 43% as an adhesive component for forming a honeycomb, with a cell count of 95 cells / cm. ２ The honeycomb-shaped precursor sheet was formed into a precursor element having a honeycomb structure. The content of the honeycomb-forming adhesive component used was approximately 4 wt % based on the weight of the precursor sheet after impregnation. The precursor element was then heat-treated in a firing furnace at 400°C in an air atmosphere for approximately 50 seconds to obtain the adsorption element of Example 1. The minimum value of the differential thermogravimetric curve of this adsorption element was -0.01°C / %.

[0044] Next, 7.7 kg of the obtained adsorption elements of Example 1 were packed into a rectangular parallelepiped block case having a height of 700 mm, a width of 250 mm, and a depth of 225 mm. It was visually confirmed that the honeycomb structure of the adsorption elements in the packed block was not crushed. In other words, it was found that high packing was possible.

[0045] Comparative Example 1 A precursor sheet prepared in the same manner as in Example 1 was used in a honeycomb forming machine to form a honeycomb with a cell count of 95 cells / cm using an acrylic emulsion with a solid content of 43% as an adhesive component for honeycomb forming. ２ The honeycomb-shaped precursor sheet was formed into a precursor element having a honeycomb structure. The content of the honeycomb-forming adhesive component used was approximately 4 wt % based on the weight of the precursor sheet after impregnation. The precursor element was then heat-treated in a firing furnace at 400°C in an air atmosphere for approximately 60 minutes to obtain an adsorption element of Comparative Example 1. The minimum value of the differential thermogravimetric curve of this adsorption element was -0.004°C / %.

[0046] Next, 7.7 kg of the obtained adsorption elements of Comparative Example 1 were packed into a rectangular parallelepiped block case having a height of 700 mm, a width of 250 mm, and a depth of 225 mm. It was visually confirmed that the honeycomb structure of the adsorption elements in the packed block had been crushed.

[0047] Figure 4 shows the evaluation results for Example 1 and Comparative Example 1. Figure 5 shows a graph of the differential thermogravimetric curves for Example 1 and Comparative Example 1. It can be seen that, compared to Comparative Example 1, Example 1 maintains the mechanical strength of the adsorption element due to the presence of an oxide of the organic binder, allowing for high packing into the block case without crushing the honeycomb structure. This shows that the configuration shown in Example 1 makes it possible to provide an adsorption element with sufficient mechanical strength as an adsorption element.

[0048] The embodiments and examples disclosed herein are all illustrative and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include all modifications within the scope of the claims and meanings equivalent to the claims.

[0049] The present invention makes it possible to manufacture an adsorption element that is excellent in mechanical strength and adsorption performance, and therefore can make a great contribution to the industrial world.

[0050] 1 adsorption element, 1a corrugated sheet, 1b liner sheet, F1 gas before passing, F2 gas after passing

Claims

1. An adsorption element having a honeycomb structure formed from an adsorption sheet containing an adsorbent, the minimum value (% / °C) of the differential thermogravimetric curve in the range of 350°C to 500°C is -0.005% / °C or less, and the number of cells in the honeycomb structure is 80 cells / cm ２ More than 135 pieces / cm ２ The adsorption element is as follows.

2. The adsorption element according to claim 1, wherein the adsorbent is at least one of zeolite, activated carbon, and a metal-organic framework (MOF).

3. The adsorption element according to claim 1 or 2, wherein the adsorption material content of the adsorption element is 60% by weight to 85% by weight when the adsorption element is taken as 100% by weight.

4. An adsorption element according to claim 1 or 2, wherein the adsorption element has a plane compressive strength of 23 kPa or more.

5. An adsorption element according to claim 1 or 2, wherein the adsorption element has a vertical compressive strength of 55 kPa or more.

6. An adsorption rotor comprising the adsorption element according to claim 1 or 2 and capable of rotating in a circumferential direction.

7. An adsorption treatment apparatus comprising the adsorption rotor according to claim 6, in which a gas to be treated is made to flow into the adsorption element to perform adsorption treatment.

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