Silica removal apparatus and adsorbent regeneration process

Abstract

To provide a silica removal apparatus and an adsorbent regeneration process capable of being operated at a lower running cost.SOLUTION: A silica removal apparatus includes a container into which water is introduced, an adsorbent provided in the container and containing at least one of activated alumina and aluminum hydroxide removing silica contained in the water, a supply channel that supplies treated water from which the silica is removed from the water by the adsorbent to the outside of the container and a heating part for heating the adsorbent.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a silica removal apparatus and a method for regenerating an adsorbent. [Background technology]

[0002] The adhesion and accumulation of scale (limescale) is a problem in various water circulation systems, including the chilled water systems and cooling water systems of air conditioning equipment, boiler feed water systems, and plant cooling water systems. If scale adheres to and accumulates in piping, it can clog the circulation system, and if scale adheres to and accumulates on the heat transfer surfaces of heat exchangers, it can lead to a deterioration in heat exchange efficiency. One of the main causes of scale is silica (silicon dioxide) ions in water. As a technology for removing such silica from water, a technology has been proposed that uses activated alumina (γ-Al2O3) to adsorb silica (Non-Patent Documents 1-3). . [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] W. Bouguerra and 3 others, “Equilibrium and kinetic studies of adsorption of silica onto activated alumina”, [online], January 31, 2006, Science Direct, [searched on May 18, 2020], Internet<https: / / www.sciencedirect.com / science / article / abs / pii / S0011916406014081?via%3Dihub> [Non-Patent Document 2] ASBEHRMAN, et al., “Removal of Silica from Water”, [online], April 1, 1940, ACS Publications [Retrieved August 16, 2023], Internet<https: / / pubs.acs.org / doi / 10.1021 / ie50364a006> [Non-Patent Document 3] Ruben Miranda and 2 others, “Silica Removal from a Paper Mill Effluent by Adsorption on Pseudoboehmite and γ-Al2O3”, [online], June 29, 2021, MDPI, [searched on May 18, 2021], Internet<https: / / www.mdpi.com / 2073-4441 / 13 / 15 / 2031> [Non-Patent Document 4] P. Sanciolo and 4 others, “Silica scale mitigation for high recovery reverse osmosis of groundwater for a mining process”, [online], December 17, 2013, Science Direct, [Retrieved May 18, 2023], Internet<https: / / www.sciencedirect.com / science / article / abs / pii / S0011916414000897?via%3Dihub> Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have discovered that aluminum oxide hydroxide, like activated alumina, has the property of adsorbing silica. However, there is a limit to the amount of silica adsorbed by activated alumina and aluminum oxide hydroxide. Therefore, in a silica removal device that removes silica from raw water using an adsorbent containing at least one of activated alumina and aluminum oxide hydroxide, regular replacement of the adsorbent increases the running cost.

[0005] One aspect of the disclosed technique aims to provide a silica removal apparatus and an adsorbent regeneration method that can be operated at lower running costs. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by a silica removal device as follows: This silica removal device includes a container into which water is introduced, an adsorbent that is placed in the container and contains at least one of activated alumina and aluminum oxide hydroxide for removing silica contained in the water, a supply path that supplies treated water from which the silica has been removed by the adsorbent to the outside of the container, and a heating unit that heats the adsorbent.

[0007] According to the silica removal device, the adsorbent that has adsorbed silica can be regenerated by heating, and the regenerated adsorbent can adsorb silica again. Since it is possible to continue removing silica from water without replacing the adsorbent with a new one, the silica removal device can be operated at a lower running cost.

[0008] The silica removal device may have the following features. The heating section heats the adsorbent to 40° C. or higher. The adsorbent containing at least one of activated alumina and aluminum oxide hydroxide can increase the amount of silica adsorption after thermal regeneration by heating to 40° C. or higher. Therefore, a decrease in efficiency of silica removal using the adsorbent after thermal regeneration can be suppressed as much as possible.

[0009] The silica removal apparatus may have the following characteristics: It further includes a drainage channel for draining the water stored in the container after heating by the heating unit, and a treated water supply unit for supplying the treated water to the container after heating by the heating unit and discharging the supplied treated water from the drainage channel. With a silica removal apparatus having such characteristics, the silica remaining in the container after heating can be washed out of the container by the treated water, so that excessive silica removal from the adsorbent after heating can be suppressed.

[0010] The silica removal device may have the following features. The container includes a first container and a second container, and while the heating unit heats the adsorbent disposed in either one of the first container and the second container, the silica is removed from the water by the adsorbent in the other container. With a silica removal device having such features, while the adsorbent in the first container is heated, the second container removes silica from the water, and while the adsorbent in the second container is heated, the first container removes silica from the water. That is, with this silica removal device, silica removal from water can be continued even while the adsorbent is being heated.

[0011] The silica removal device may have the following features. A stirring blade is disposed in the container, and the stirring blade is driven at a predetermined interval to stir the water in the container. When the stirring blade rotates while water is stored in the container, the water in the container is stirred and the air bubbles attached to the adsorbent are removed. Air bubbles may adhere to the adsorbent as the water flows through the adsorbent, and the silica removal performance of the adsorbent may be reduced due to the air bubbles. A silica removal device having such features can remove the air bubbles attached to the adsorbent, so that the silica removal ability of the silica removal device is suppressed from decreasing. The removal of the air bubbles attached to the adsorbent may be achieved by disposing an ultrasonic generator in the container and generating ultrasonic waves at a predetermined interval by the ultrasonic generator.

[0012] The silica removal device may have the following features. The adsorbent is divided into mesh bags and placed in the container. In a silica removal device having such features, the mesh itself acts as a filter, and suspended solids in the water are removed. In addition, when the adsorbent is divided into a plurality of containers, the flow of water in the container is rectified by the gaps between the meshes to make the flow uniform, and the adsorbent on the upstream side, which is expected to reach the end of its life sooner, can be preferentially replaced.

[0013] The disclosed technology can also be understood from the aspect of a method for regenerating an adsorbent. Effect of the Invention

[0014] According to the disclosed technology, it is possible to provide a silica removal apparatus and an adsorbent regeneration method that can be operated at lower running costs. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing an example of a silica removing device according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a cross section of an adsorption tower. [Diagram 3] FIG. 3 is a diagram showing an example of the results of a test performed on the silica adsorption performance. [Figure 4] FIG. 4 is a diagram illustrating the verification results of the adsorption of silica by activated alumina. [Diagram 5] FIG. 5 is a diagram showing an example of a process flow for removing silica from raw water using the silica removal device according to the embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a silica removing device according to a first modified example. [Figure 7] FIG. 7 is a diagram showing an example of a process flow for removing silica from raw water by the silica removal device according to the first modified example. [Figure 8] FIG. 8 is a diagram showing an example of a silica removing apparatus according to the second modified example. [Figure 9] FIG. 9 is a diagram showing an example of a process flow for removing silica from raw water by the silica removal apparatus according to the second modified example. [Figure 10] FIG. 10 is a diagram showing an example of a heating system for activated alumina according to the third modified example. [Figure 11] FIG. 11 is a diagram showing an example of an adsorption tower provided with an agitating blade in the fourth modified example. [Figure 12] FIG. 12 is a diagram showing an example of an adsorption tower provided with an ultrasonic generator in the fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <Embodiment> 1 is a diagram showing an example of a silica removal apparatus 1 according to an embodiment. The silica removal apparatus 1 includes adsorption towers 2 and 3, a raw water supply pipe 4, a treated water supply pipe 5, a drain pipe 6, valves 7, 7A, 8, and 8A, heating devices 21 and 31, and connecting pipes 41, 42, 51, 52, 61, and 62.

[0017] The raw water supply pipe 4 is a pipe that is connected to the adsorption tower 2 by a connecting pipe 41 and is connected to the adsorption tower 3 by a connecting pipe 42. The raw water supply pipe 4 supplies raw water, such as tap water or well water, to the adsorption towers 2 and 3 via the connecting pipes 41 and 42. Valves 7 and 8 are provided on the connecting pipes 41 and 42, respectively. The silica removal apparatus 1 can select either the adsorption tower 2 or 3 to which raw water is to be supplied by opening or closing the valves 7 and 8.

[0018] The adsorption towers 2 and 3 adsorb silica in the raw water to an adsorbent containing at least one of activated alumina (γ-Al2O3, γ-alumina) and aluminum oxide hydroxide (AlOOH). Although α-Al2O3 is sometimes called activated alumina, in this specification, activated alumina is γ-Al2O3, not α-Al2O3. The adsorbent is formed, for example, in a granular form. FIG. 2 is a diagram showing an example of a cross section of the adsorption tower 2. FIG. 2 shows an example of a cross section of the adsorption tower 2, but the cross section of the adsorption tower 3 is similar. The inside of the adsorption tower 2 is filled with aluminum oxide hydroxide 22 formed in a granular form. In this embodiment, a configuration in which aluminum oxide hydroxide 22 is used as the adsorbent will be described, but as described above, the adsorbent may include at least one of aluminum oxide hydroxide 22 and activated alumina. When the inside of the adsorption tower 2 is filled with granular aluminum oxide hydroxide 22, gaps 23 are formed inside the adsorption tower 2. Raw water supplied from raw water supply pipe 4 passes through gap 23, whereby silica in the raw water is adsorbed by aluminum oxide hydroxide 22. The treated water from which silica has been adsorbed in adsorption towers 2 and 3 is sent to treated water supply pipe 5 via connecting pipes 51 and 52. Adsorption towers 2 and 3 are an example of a "container." Adsorption tower 2 is an example of a "first container." Adsorption tower 3 is an example of a "second container."

[0019] The treated water supply pipe 5 is connected to the adsorption tower 2 by a connecting pipe 51 and to a connecting pipe 52. Thus, it is a pipe connected to the adsorption tower 3. The treated water supply pipe 5 supplies the treated water, which has had silica adsorbed by the adsorption towers 2 and 3, to external equipment such as a cold water system or cooling water system of an air conditioning system, a boiler feed water system, a plant cooling water system, or various other water circulation systems. A valve 7B is provided on the connecting pipe 51, and a valve 8B is provided on the connecting pipe 52. By opening and closing the valves 7B and 8B, it is possible to select from which of the adsorption towers 2 and 3 the treated water is to flow into the treated water supply pipe 5. The treated water supply pipe 5 is an example of a "supply path".

[0020] The drain pipe 6 is a pipe that is connected to the adsorption tower 2 by a connecting pipe 61 and is connected to the adsorption tower 3 by a connecting pipe 62. Valves 7A and 8A are provided on the connecting pipes 61 and 62, respectively. By opening and closing the valves 7A and 8A, it is possible to select whether or not to drain water from the adsorption towers 2 and 3. The drain pipe 6 drains water accumulated in the adsorption towers 2 and 3. The drain pipe 6 is an example of a "drainage channel."

[0021] The heating devices 21, 31 are disposed so as to be in contact with the side surfaces of the adsorption towers 2, 3. The heating devices 21, 31 are heaters that heat the aluminum oxide hydroxide 22 in the adsorption towers 2, 3 by heating the adsorption towers 2, 3. There is no limitation on the heating method of the heating devices 21, 31, and various means can be adopted, for example, heating by fire, heating by a current-carrying nichrome wire, heating by electromagnetic induction, etc. In FIG. 1, the heating devices 21, 31 are illustrated as being in contact with the side surfaces of the adsorption towers 2, 3 to heat the adsorption towers 2, 3 from the outside, but the heating devices 21, 31 may be disposed inside the adsorption towers 2, 3. The heating devices 21, 31 are an example of a "heating section".

[0022] <Method of producing aluminum oxide hydroxide 22> The aluminum oxide hydroxide 22 is produced, for example, by the following steps (1) and (2). (1)Al2O3+2OH - +3H2O is dissolved in NaHO solution, filtered, and cooled to produce Al(OH)3 via the following reaction: Al2O3+2OH - +3H2O → 2Al(OH)3+H2O (2) By heating Al(OH)3 in a neutral to slightly basic aqueous solution to 150 to 300°C, AlO(OH) is produced by the following reaction. Al(OH)3 → AlO(OH) + H2O

[0023] <Method of producing activated alumina> Activated alumina is produced, for example, by the following steps (1) to (3). (1)Al2O3+2OH - +3H2O is dissolved in NaHO solution, filtered, and cooled to produce Al(OH)3 via the following reaction: Al2O3+2OH - +3H2O → 2Al(OH)3+H2O (2) By heating Al(OH)3 in a neutral to slightly basic aqueous solution to 150 to 300°C, AlO(OH) is produced by the following reaction. Al(OH)3 → AlO(OH) + H2O (3) By heating AlO(OH) to 500℃, activated alumina (γ-Al2O3) is produced by the following reaction. Note that when AlO(OH) is heated to 1000℃ or higher, α-Al2O3 is produced. 2AlO(OH) → Al2O3+H2O

[0024] Here, the silica adsorption performance of the aluminum hydroxide oxide 22 and the activated alumina will be examined. This examination is carried out in the following procedure. (1) Place 0.1 g of the sample to be verified in a 16 mg-Si / g sodium silicate solution or tap water. (2) Immerse the sample in water at 20°C for 24 hours. (3) Filter through 5C filter paper and measure the silicon concentration in the filtrate.

[0025] FIG. 3 is a diagram showing an example of the results of a verification carried out on the performance of adsorbing silica. In FIG. 3, in addition to aluminum hydroxide oxide 22 and activated alumina, the results of aluminum hydroxide (Al(OH)3) and α-alumina (α-Al2O2) are also illustrated for comparison. Referring to FIG. 3, it can be seen that both aluminum hydroxide oxide 22 and activated alumina have high silica removal capabilities compared to aluminum hydroxide and α-alumina. It can also be seen that aluminum hydroxide oxide 22 has the highest silica removal capability among the four samples prepared.

[0026] <Thermal regeneration of aluminum oxide hydroxide 22 adsorbed with silica> The thermal regeneration of the aluminum hydroxide oxide 22 with silica adsorption was verified, and will be described with reference to the drawings. Fig. 4 is a diagram illustrating the verification results of the adsorption of silica by the aluminum hydroxide oxide 22. The verification results will be described below with reference to Fig. 4.

[0027] (First Verification) In the first verification, the relationship between the amount of silica adsorbed by the aluminum oxide hydroxide 22 and the temperature at which the aluminum oxide hydroxide 22 is heated was verified. In the first verification, the following first to third steps were performed.

[0028] (First step) 1 g of aluminum oxide hydroxide 22 was immersed in 50 ml of water with a silica concentration of a mg / L for 1 hour. After immersion, the aluminum oxide hydroxide 22 and the water were separated, and the silica concentration of the separated water was measured at b mg / L. The amount of silica adsorbed by the aluminum oxide hydroxide 22 was calculated by {(ab) [mg / L] × 0.05 [L]} / 1 [g]. The amount of silica adsorbed by the aluminum oxide hydroxide 22 when it was first adsorbed was 2.4 mg-si / g.

[0029] (Second step) The aluminum hydroxide oxide 22 to which silica has been adsorbed in the first step is immersed in 50 ml of heated ultrapure water for 24 hours to heat the aluminum hydroxide oxide 22 and heat-regenerate the aluminum hydroxide oxide 22. After immersion, the aluminum hydroxide oxide 22 is separated from the ultrapure water.

[0030] (Third step) Using the aluminum oxide hydroxide 22 separated from the ultrapure water in the second step, the silica adsorption in the first step is carried out again.

[0031] Fig. 4A is a diagram illustrating the relationship between the temperature of the heated ultrapure water and the amount of silica adsorbed by aluminum oxide hydroxide 22 in the first verification. The vertical axis of Fig. 4A illustrates the amount of silica adsorbed (mg-si / g) by aluminum oxide hydroxide 22 in the third step, and the horizontal axis illustrates the temperature (°C) of the ultrapure water in the second step. With reference to Fig. 4A, it can be seen that the higher the temperature of the ultrapure water used in the second step, the greater the amount of silica adsorbed by the regenerated aluminum oxide hydroxide 22. The temperature of the ultrapure water in the second step is preferably, for example, 40°C or higher.

[0032] FIG. 4B is a diagram illustrating the relationship between the immersion time when aluminum oxide hydroxide 22 is immersed in ultrapure water heated to 80° C. and the amount of silica adsorbed by aluminum oxide hydroxide 22 in the first verification. FIG. 4C is a diagram illustrating the relationship between the immersion time when aluminum oxide hydroxide 22 is immersed in ultrapure water heated to 60° C. and the amount of silica adsorbed by aluminum oxide hydroxide 22 in the first verification. With reference to FIGS. 4B and 4C, it can be seen that the longer the immersion time, the greater the amount of silica adsorbed by the regenerated aluminum oxide hydroxide 22. It can also be seen that even with an immersion time of about 30 seconds, the amount of silica adsorbed by aluminum oxide hydroxide 22 tends to recover. With reference to FIG. 4B, It can be seen that by immersing aluminum hydroxide oxide 22 in ultrapure water at 80° C. for 24 hours, the amount of silica adsorbed by aluminum hydroxide oxide 22 can be restored to "2.2 mg-si / g", which is the same as when silica was first adsorbed.

[0033] (Second Verification) In the second verification, the first to third steps in the first verification were repeated to verify the change in the amount of silica adsorbed by aluminum oxide hydroxide 22. In the second verification, the ultrapure water was heated to 80° C. in the second step, and the time for immersing aluminum oxide hydroxide 22 in the ultrapure water was set to 24 hours. FIG. 4D is a diagram illustrating the results of the second verification. The vertical axis of FIG. 4D illustrates the amount of silica adsorbed by aluminum oxide hydroxide 22 (mg-si / g), and the horizontal axis illustrates the number of times that the first to third steps were repeated.

[0034] 4D, it can be seen that even if the regeneration of aluminum oxide hydroxide 22 by heating is repeatedly performed, the amount of silica adsorption by aluminum oxide hydroxide 22 can be maintained at about "1.5 mg-si / g". In other words, it can be seen that the regeneration of aluminum oxide hydroxide 22 by heating can be repeatedly performed. Note that although the adsorption of silica by aluminum oxide hydroxide 22 has been described with reference to FIGS. 4A to 4D, the same results are obtained for activated alumina as for aluminum oxide hydroxide 22.

[0035] <Silica removal process> Fig. 5 is a diagram showing an example of a process flow for removing silica from raw water by the silica removal apparatus 1 according to the embodiment. In Fig. 5, the adsorption tower 2 is described as the first adsorption tower, the adsorption tower 3 is described as the second adsorption tower, the valve 7 is described as the first valve, the valve 8 is described as the second valve, the valve 7A is described as the third valve, the valve 8A is described as the fourth valve, the heating device 21 is described as the first heating device, and the heating device 31 is described as the second heating device. Hereinafter, an example of a process flow for removing silica from raw water by the silica removal apparatus 1 will be described with reference to Fig. 5.

[0036] In step S1, the valves 7 and 7B are opened, and the valves 7A, 8, 8A, and 8B are closed. As a result, raw water flows into the adsorption tower 2 via the raw water supply pipe 4 and the connecting pipe 41, and the treated water from which silica has been removed in the adsorption tower 2 is supplied to external equipment via the connecting pipe 51 and the treated water supply pipe 5.

[0037] In step S2, silica contained in the raw water is removed by being adsorbed onto the aluminum oxide hydroxide 22 in the adsorption tower 2. The treated water from which silica has been removed by the adsorption tower 2 is supplied to an external facility via the connection pipe 51 and the treated water supply pipe 5.

[0038] In step S3, valves 8 and 8B are opened, and valves 7 and 7B are closed. As a result, raw water flows into the adsorption tower 3 via the raw water supply pipe 4 and the connecting pipe 42, and treated water from which silica has been removed in the adsorption tower 3 is supplied to external equipment via the connecting pipe 52 and the treated water supply pipe 5.

[0039] In step S4, silica contained in the raw water is removed by being adsorbed onto aluminum oxide hydroxide 22 in the adsorption tower 3. The treated water from which silica has been removed by the adsorption tower 3 is supplied to external equipment via the connecting pipe 52 and the treated water supply pipe 5. In addition, the heating device 21 heats the aluminum oxide hydroxide 22 in the adsorption tower 2. By heating the aluminum oxide hydroxide 22, the aluminum oxide hydroxide 22 becomes capable of adsorbing silica again. After the aluminum oxide hydroxide 22 is heated, the valve 7A is opened and the water stored in the adsorption tower 2 is drained from the drain pipe 6 via the connecting pipe 61.

[0040] In step S5, the valves 7 and 7B are opened, and the valves 7A, 8, 8A, and 8 As a result, the raw water supplied flows into the adsorption tower 2 via the raw water supply pipe 4 and the connecting pipe 41.

[0041] In step S6, silica contained in the raw water is removed by being adsorbed onto the aluminum oxide hydroxide 22 in the adsorption tower 2. The treated water from which silica has been removed by the adsorption tower 2 is supplied to external equipment via the connecting pipe 51 and the treated water supply pipe 5. In addition, the aluminum oxide hydroxide 22 in the adsorption tower 3 is heated by the heating device 31. By heating the aluminum oxide hydroxide 22, the aluminum oxide hydroxide 22 becomes capable of adsorbing silica again. After the aluminum oxide hydroxide 22 is heated, the valve 8A is opened and the water stored in the adsorption tower 3 is drained from the drain pipe 6 via the connecting pipe 62.

[0042] <Effects of the embodiment> According to this embodiment, the aluminum hydroxide oxide 22 having silica adsorbed thereon is heated and regenerated, and the silica can be adsorbed by the heated and regenerated aluminum hydroxide oxide 22. That is, according to this embodiment, it is possible to continue removing silica from water without replacing the aluminum hydroxide oxide 22 having silica adsorbed thereon with new aluminum hydroxide oxide 22. Therefore, according to this embodiment, it is possible to reduce the running cost of removing silica from raw water using the aluminum hydroxide oxide 22.

[0043] According to this embodiment, while the aluminum oxide hydroxide 22 in the adsorption tower 2 is being regenerated, silica removal from the raw water is performed by the adsorption tower 3, and while the aluminum oxide hydroxide 22 in the adsorption tower 3 is being regenerated, silica removal from the raw water is performed by the adsorption tower 2. That is, according to this embodiment, silica removal from the raw water can be continued even during the regeneration of the aluminum oxide hydroxide 22.

[0044] According to this embodiment, after the aluminum hydroxide oxide 22 is heated, the water stored in the adsorption towers 2 and 3 is drained from the drain pipe 6 via the connecting pipes 61 and 62. Therefore, adsorption of silica contained in the stored water to the aluminum hydroxide oxide 22 regenerated by heating is suppressed.

[0045] <First Modification> In the embodiment described above, after the aluminum hydroxide oxide 22 in the adsorption towers 2, 3 is heated and regenerated, the adsorption towers 2, 3 are not cleaned. In the first modification, a modification in which the aluminum hydroxide oxide 22 in the adsorption towers 2, 3 is heated and regenerated, and then the adsorption towers 2, 3 are cleaned. The same components as in the embodiment are denoted by the same reference numerals, and their description will be omitted. Hereinafter, the first modification will be described with reference to the drawings.

[0046] 6 is a diagram showing an example of a silica removal apparatus 1A according to a first modified example. The silica removal apparatus 1A differs from the silica removal apparatus 1 according to the embodiment in that a cleaning water supply pipe 9 is connected to the adsorption tower 2, and a cleaning water supply pipe 10 is connected to the adsorption tower 3. The cleaning water supply pipes 9 and 10 are provided with valves 7C and 8C, respectively.

[0047] The cleaning water supply pipe 9 is a pipe that supplies cleaning water for cleaning the inside of the adsorption tower 2 to the adsorption tower 2. The cleaning water supplied to the adsorption tower 2 is drained from the drain pipe 6 via the connecting pipe 61. The cleaning water supply pipe 10 is a pipe that supplies cleaning water for cleaning the inside of the adsorption tower 3 to the adsorption tower 3. The cleaning water supplied to the adsorption tower 3 is drained from the drain pipe 6 via the connecting pipe 62. As the cleaning water, for example, treated water from which silica has been removed by the adsorption towers 2 and 3 or ultrapure water can be used. The cleaning water supply pipes 9 and 10 are an example of a "treated water supply unit".

[0048] FIG. 7 is a flow chart showing a process for removing silica from raw water by a silica removal device 1A according to a first modified example. 7 is a diagram showing an example of the process flow for removing silica from raw water by the silica removal apparatus 1A will be described below with reference to FIG.

[0049] In step S1A, the valves 7 and 7B are opened, and the valves 7A, 7C, 8, 8A, 8B, and 8C are closed. In step S3A, the valves 8 and 8B are opened, and the valves 7 and 7B are closed.

[0050] In step S41, the valves 7A and 7C are opened, and then cleaning water is supplied to the adsorption tower 2 via the cleaning water supply pipe 9. The cleaning water supplied to the adsorption tower 2 is drained from the drain pipe 6 via the connecting pipe 61. Thereafter, the valves 7A and 7C are closed.

[0051] In step S42, the valves 8A and 8C are opened, and then cleaning water is supplied to the adsorption tower 3 via the cleaning water supply pipe 10. The cleaning water supplied to the adsorption tower 3 is drained from the drain pipe 6 via the connecting pipe 62. Thereafter, the valves 8A and 8C are closed.

[0052] In the first modification, after the aluminum oxide hydroxide 22 is regenerated by heating, the insides of the adsorption towers 2 and 3 are washed with wash water. This washing washes away silica remaining in the adsorption towers 2 and 3, and therefore a decrease in the amount of silica removed from the raw water caused by the remaining silica being adsorbed by the aluminum oxide hydroxide 22 is suppressed.

[0053] <Second Modification> In the embodiment described above, the aluminum hydroxide oxide 22 is heated by heating the adsorption towers 2 and 3 using the heating devices 21 and 31 provided in the adsorption towers 2 and 3, respectively. In the second modification, a configuration in which the aluminum hydroxide oxide 22 is heated by supplying hot water to the adsorption towers 2 and 3 will be described.

[0054] 8 is a diagram showing an example of a silica removal apparatus 1B according to a second modified example. The silica removal apparatus 1B differs from the silica removal apparatus 1 according to the embodiment in that a hot water tank 71, instead of the heating device 21, is connected to the adsorption tower 2 by a hot water supply pipe 72 and a hot water drain pipe 73, and a hot water tank 81, instead of the heating device 31, is connected to the adsorption tower 3 by a hot water supply pipe 82 and a hot water drain pipe 83. Valves 7D and 7E are provided in the hot water supply pipe 72 and the hot water drain pipe 73, respectively. Valves 8D and 8E are provided in the hot water supply pipe 82 and the hot water drain pipe 83, respectively.

[0055] The hot water tanks 71 and 81 are water tanks that store a portion of the treated water supplied from the treated water supply pipe. The hot water tanks 71 and 81 are equipped with a heater therein, and the treated water stored in the hot water tanks 71 and 81 is heated by the heater to produce hot water of, for example, 80° C. The hot water tank 71 supplies the heated hot water to the adsorption tower 2 via the hot water supply pipe 72, and the aluminum oxide hydroxide 22 is heated and regenerated by the heat of the hot water. The hot water that has had its heat removed by the aluminum oxide hydroxide 22 is returned to the hot water tank 71 via the hot water drain pipe 73. The hot water returned to the hot water tank 71 is heated by the heater in the hot water tank 71 and supplied to the adsorption tower 2 via the hot water supply pipe 72.

[0056] Fig. 9 is a diagram showing an example of a process flow of removing silica from raw water by the silica removal apparatus 1B according to the second modified example. Hereinafter, with reference to Fig. 9, an example of a process flow of removing silica from raw water by the silica removal apparatus 1B will be described.

[0057] In step S1A, valves 7 and 7B are opened, while valves 7A, 7D, 7E, 8, 8A, 8B, 8D, and 8E are closed.

[0058] In step S4A, silica contained in the raw water is converted into hydroxide acid in the adsorption tower 3. The silica is adsorbed by the aluminum oxide hydroxide 22 and removed. The treated water from which silica has been removed by the adsorption tower 3 is supplied to an external facility via the connecting pipe 52 and the treated water supply pipe 5. The valves 7D and 7E are opened, and the valves 7, 7A, and 7B are closed. As a result, hot water from the hot water tank 71 is supplied to the adsorption tower 2 via the hot water supply pipe 72, and the hot water from which heat has been removed by the aluminum oxide hydroxide 22 in the adsorption tower 2 is returned to the hot water tank 71 via the hot water drain pipe 73. The aluminum oxide hydroxide 22 is heated, so that the aluminum oxide hydroxide 22 can adsorb silica again. After the aluminum oxide hydroxide 22 is heated, the valve 7A is opened, and the hot water stored in the adsorption tower 2 is drained from the drain pipe 6 via the connecting pipe 61. The valves 7A, 7D, and 7E are then closed.

[0059] In step S6A, silica contained in the raw water is removed by being adsorbed by the aluminum oxide hydroxide 22 in the adsorption tower 2 in the adsorption tower 2. The treated water from which silica has been removed by the adsorption tower 2 is supplied to an external facility via the connecting pipe 51 and the treated water supply pipe 5. In addition, the valves 8D and 8E are opened, and the valves 8, 8A, and 8B are closed. As a result, hot water from the hot water tank 81 is supplied to the adsorption tower 3 via the hot water supply pipe 82, and the hot water from which heat has been removed by the aluminum oxide hydroxide 22 in the adsorption tower 3 is returned to the hot water tank 81 via the hot water drain pipe 83. The aluminum oxide hydroxide 22 is heated, so that the aluminum oxide hydroxide 22 can adsorb silica again. After the aluminum oxide hydroxide 22 is heated, the valve 8A is opened, and the hot water stored in the adsorption tower 3 is drained from the drain pipe 6 via the connecting pipe 62. Thereafter, the valves 8A, 8D, and 8E are closed.

[0060] In the second modification, the aluminum hydroxide oxide 22 can be thermally regenerated in the same manner as in the first modification by heating the aluminum hydroxide oxide 22 with warm water. During thermal regeneration in the second modification, water containing silica eluted from the aluminum hydroxide oxide 22 may be discharged from the adsorption towers 2, 3, and the water discharged (e.g., treated water) may be replenished to the adsorption towers 2, 3 to replace the water in the adsorption towers 2, 3. By replacing the water in this manner, thermal regeneration can be performed efficiently even with a small amount of water.

[0061] <Third Modification> In the embodiment and the second modified example described above, the aluminum hydroxide oxide 22 is heated inside the adsorption towers 2 and 3. In the third modified example, a configuration in which the aluminum hydroxide oxide 22 is heated outside the adsorption towers 2 and 3 will be described.

[0062] Fig. 10 is a diagram showing an example of a heating system 200 for aluminum hydroxide oxide 22 according to a third modified example. The heating system 200 includes a regeneration vessel 201, a heating device 202, a circulation device 203, and connecting pipes 211, 212, and 213. The regeneration vessel 201 and the heating device 202 are connected by the connecting pipe 211. The heating device 202 and the circulation device 203 are connected by the connecting pipe 212. The circulation device 203 and the regeneration vessel 201 are connected by the connecting pipe 213. Valves are not shown in Fig. 10.

[0063] The aluminum oxide hydroxide 22 used to adsorb silica in the adsorption towers 2, 3 is removed from the adsorption towers 2, 3 and stored in the regeneration vessel 201. Water is also stored in the regeneration vessel 201. The water stored in the regeneration vessel 201 is preferably treated water from which silica has been removed, but may also be tap water.

[0064] The circulation device 203 has a pump, and by driving the pump, the water stored in the regeneration container 201 is sent to the heating device 202 via the connecting pipe 211, and the water sent to the heating device 202 is sent to the regeneration container 201 via the connecting pipe 212, the circulation device 203, and the connecting pipe 213. In other words, the circulation device 203 circulates water between the regeneration container 201 and the heating device 202.

[0065] The heating device 202 has a heater for heating water, and the heater heats the water sent from the regeneration container 201. The water heated by the heating device 202 is sent to the regeneration container 201 by the circulation device 203 as described above.

[0066] In a heating system 200 according to the third modification, water heated by a heating device 202 is supplied to a regeneration container 201, thereby heating the aluminum hydroxide oxide 22 in the regeneration container 201. The water from which heat has been removed by heating the aluminum hydroxide oxide 22 is sent to the heating device 202 by a circulation device 203, where it is reheated, and is sent again to the regeneration container 201. Therefore, according to the third modification, the aluminum hydroxide oxide 22 taken out from the adsorption towers 2 and 3 can be heated and regenerated.

[0067] The aluminum hydroxide oxide 22 thermally regenerated by the heating system 200 is washed with water to remove silica remaining on the surface, and then returned to the adsorption towers 2 and 3. During thermal regeneration in the heating system 200, the water containing silica eluted from the aluminum hydroxide oxide 22 may be drained from the regeneration vessel 201 and the drained water (e.g., treated water) may be replenished to the regeneration vessel 201 to replace the water in the regeneration vessel 201. By replacing the water in this manner, efficient thermal regeneration can be performed even with a small amount of water.

[0068] <Fourth Modification> Air bubbles may adhere to the aluminum hydroxide oxide 22 stored in the adsorption towers 2 and 3 as the raw water passes through the aluminum hydroxide oxide 22. Since the raw water is less likely to flow through the areas where the air bubbles adhere, there is a risk of a decrease in the silica removal capacity of the adsorption towers 2 and 3. In the third modified example, the removal of air bubbles adhered to the aluminum hydroxide oxide 22 will be described.

[0069] To remove the air bubbles, for example, it is possible to provide an agitating blade inside the adsorption towers 2 and 3. FIG. 11 is a diagram showing an example of the adsorption tower 2 provided with an agitating blade 91 in the third modified example. For simplicity, the aluminum oxide hydroxide 22 is not shown in FIG. 11. The agitating blade 91 is provided, for example, at the bottom of the adsorption tower 2, but may be provided at the top of the adsorption tower 2. When the agitating blade 91 rotates while water is stored in the adsorption tower 2, the water in the adsorption tower 2 is agitated, and the air bubbles attached to the aluminum oxide hydroxide 22 are removed. Note that the agitating blade 91 is preferably provided inside the adsorption tower 2, because the air bubbles can be periodically removed by rotating the agitating blade 91 at predetermined intervals, for example. The same applies to the adsorption tower 3.

[0070] 12 is a diagram showing an example of an adsorption tower 2 provided with an ultrasonic generator 92 in the fourth modified example. The ultrasonic generator 92 removes air bubbles adhering to the aluminum oxide hydroxide 22 by vibrating the water and aluminum oxide hydroxide 22 in the adsorption tower 2 with ultrasonic waves. The ultrasonic generator 92 is preferable because it can periodically remove air bubbles by generating ultrasonic waves at predetermined time intervals, for example. The same applies to the adsorption tower 3.

[0071] Another method for removing the air bubbles adhering to the aluminum hydroxide oxide 22 is, for example, a method of circulating water between the adsorption towers 2 and 3. Air bubbles adhering to the aluminum hydroxide oxide 22 can also be removed by suddenly changing the water flow rate at which raw water is supplied to the adsorption towers 2 and 3 (changing the water flow rate at an acceleration equal to or higher than a predetermined threshold value). Air may also be sent into the adsorption towers 2 and 3 to generate bubbles (bubbling), and the air bubbles adhering to the aluminum hydroxide oxide 22 may be removed by the bubbles.

[0072] According to the third modification, the air bubbles adhering to the aluminum hydroxide oxide 22 are removed, so that a decrease in the silica removal capacity of the adsorption towers 2, 3 caused by the air bubbles adhering to the aluminum hydroxide oxide 22 is suppressed.

[0073] <Fourth Modification> As explained with reference to Fig. 4D, even if the thermal regeneration of the aluminum hydroxide oxide 22 is repeated many times, the silica removal performance of the aluminum hydroxide oxide 22 is maintained to a certain degree. However, repeated thermal regeneration of the aluminum hydroxide oxide 22 may cause the desired silica removal capacity of the adsorption towers 2, 3 to decrease. When the silica removal capacity falls below the desired capacity, it is considered better to replace the aluminum hydroxide oxide 22 in the adsorption towers 2, 3 with new aluminum hydroxide oxide 22. In the fourth modification, a description will be given of the determination of the replacement time of the aluminum hydroxide oxide 22.

[0074] The silica removal performance of the thermally regenerated aluminum hydroxide 22 can be determined, for example, by measuring the silica concentration in treated water from which silica has been removed by the adsorption towers 2 and 3. Methods for measuring the silica concentration include a method using molybdenum, ICP atomic emission spectrometry, and atomic absorption spectrometry, but none of these methods are considered suitable for continuous or simple analysis of treated water.

[0075] Therefore, in the fourth modified example, a frequency threshold is set for the number of times that the aluminum hydroxide oxide 22 is thermally regenerated, and when the number of times that the aluminum hydroxide oxide 22 is thermally regenerated reaches or exceeds the frequency threshold, it is determined that the life of the aluminum hydroxide oxide 22 has expired, and the aluminum hydroxide oxide 22 in the adsorption towers 2, 3 is replaced with new aluminum hydroxide oxide 22.

[0076] In the fourth modification, a processing amount threshold may be set for the processing amount of raw water from which silica is removed by the adsorption towers 2 and 3, and when the processing amount of raw water treated by the adsorption towers 2 and 3 becomes equal to or greater than the processing amount threshold, it may be determined that the life of the aluminum oxide hydroxide 22 has expired, and the aluminum oxide hydroxide 22 in the adsorption towers 2 and 3 may be replaced with new aluminum oxide hydroxide 22. The number of times threshold and processing amount threshold may be set in advance by testing, for example.

[0077] As a method for storing the aluminum hydroxide oxide 22 in the adsorption towers 2, 3 during replacement, there may be mentioned a method in which baffles are placed in the adsorption towers 2, 3 so as to suppress turbulence of the water flow in the adsorption towers 2, 3, and granular aluminum hydroxide oxide 22 is stored in the adsorption towers 2, 3.

[0078] As an alternative method for storing the aluminum hydroxide oxide 22 in the adsorption towers 2 and 3 during replacement, for example, the aluminum hydroxide oxide 22 may be filled into a water-permeable container (for example, a mesh bag) and the container may be stored in the adsorption towers 2 and 3. In this case, the aluminum hydroxide oxide 22 may be filled into one container and stored in the adsorption towers 2 and 3. Alternatively, the aluminum hydroxide oxide 22 may be divided into a plurality of containers and filled therein, and then stored in the adsorption towers 2 and 3.

[0079] By filling the mesh bag with aluminum hydroxide oxide 22, the mesh itself acts as a filter to remove suspended solids in the raw water. In addition, when the aluminum hydroxide oxide 22 is divided into multiple containers, the flow of raw water in the adsorption towers 2 and 3 is rectified by the gaps between the mesh to make the flow uniform, and the aluminum hydroxide oxide 22 on the upstream side, which is thought to reach the end of its life sooner, can be preferentially replaced.

[0080] According to the fourth modified example, aluminum hydroxide oxide 22 with reduced silica removal capacity is replaced with new aluminum hydroxide oxide 22, so that even if the adsorption towers 2, 3 are operated continuously for a long period of time, the deterioration of the silica removal capacity of the adsorption towers 2, 3 is suppressed.

[0081] <Other variations> In the embodiment, two adsorption towers 2, 3 are used, so that while regeneration of aluminum oxide hydroxide 22 is being performed in one of the adsorption towers 2, 3, silica removal from the raw water continues in the other of the adsorption towers 2, 3. However, the silica removal apparatus 1 may be configured to include a single adsorption tower 2. In this case, it is sufficient to stop the removal of silica from the raw water while regeneration of aluminum oxide hydroxide 22 is being performed in the adsorption tower 2. By using a configuration including a single adsorption tower 2, silica removal from the raw water can be achieved with a simpler configuration than that of the silica removal apparatus 1 according to the embodiment.

[0082] Furthermore, an agitator for agitating the aluminum oxide hydroxide 22 may be provided in the adsorption towers 2 and 3. By agitating the aluminum oxide hydroxide 22 during heating by the heating devices 21 and 31, the aluminum oxide hydroxide 22 is heated more efficiently.

[0083] Furthermore, a mesh-like member may be disposed downstream of the aluminum hydroxide oxide 22 in the adsorption towers 2 and 3. By disposing such a member, the granular aluminum hydroxide oxide 22 is prevented from flowing out downstream of the adsorption towers 2 and 3.

[0084] The embodiments and modifications disclosed above can be combined with each other. [Explanation of symbols]

[0085] 1. Silica removal device 1A·Silica removal device 1B Silica removal device 2.Adsorption tower 3...Adsorption tower 4. Raw water supply pipe 5. Treated water supply pipe 6...Drain pipe 7. Valve 7A··Valve 7B Valve 7C··Valve 7D··Valve 7E··Valve 8. Valve 8A··Valve 8B··Valve 8C··Valve 8D··Valve 8E··Valve 9. Cleaning water supply pipe 10. Cleaning water supply pipe 21...Heating device 22. Aluminum oxide hydroxide 23. Gap 31...Heating device 41 Connecting pipe 42 Connecting pipe 51 Connecting pipe 52 Connecting pipe 61 Connecting pipe 62 Connecting pipe 71·Hot water tank 72·Hot water supply pipe 73·Hot water drain pipe 81·Hot water tank 82·Hot water supply pipe 83·Hot water drain pipe 91··Mixing blade 92 Ultrasonic generator 200 Heating System 201·Recycled container 202...Heating device 203...Circulation device 211 Connecting pipe 212 Connecting pipe 213 Connecting pipe

Claims

1. A container into which water is introduced; an adsorbent, the adsorbent including at least one of activated alumina and aluminum oxide hydroxide, disposed in the container and adapted to remove silica contained in the water; a supply path for supplying treated water obtained by removing the silica from the water by the adsorbent to the outside of the container; A heating unit that heats the adsorbent. Silica removal equipment.

2. The heating unit heats the adsorbent to 40° C. or higher. The silica removal apparatus according to claim 1 .

3. a drainage channel for draining the water stored in the container after heating by the heating unit; The system further includes a treated water supply unit that supplies the treated water to the container after heating by the heating unit and discharges the supplied treated water from the drainage channel. The silica removal apparatus according to claim 1 .

4. The container includes a first container and a second container, While the heating unit heats the adsorbent disposed in either the first container or the second container, the silica is removed from the water by the adsorbent in the other container. The silica removal apparatus according to claim 1 .

5. A stirring blade is disposed in the container, The stirring blade is driven at predetermined intervals to stir the water in the container. The silica removal apparatus according to claim 1 .

6. An ultrasonic generator is disposed within the container, The ultrasonic generator generates ultrasonic waves at predetermined intervals. The silica removal apparatus according to claim 1 .

7. The adsorbent is placed in the container in a mesh bag. The silica removal apparatus according to any one of claims 1 to 6.

8. an adsorption stopping step of stopping the process of adsorbing silica contained in the water onto an adsorbent containing at least one of activated alumina and aluminum oxide hydroxide; A heating step of heating the adsorbent having the silica adsorbed thereon. Methods for regenerating adsorbents.

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