Particulate adsorbent recovery device

Abstract

To prevent a filtration speed from decreasing with the thickness of a cake generated during dehydration treatment by filtration of liquid or slurry containing particulate adsorbents, or the like as an appropriate range.SOLUTION: An adsorbent recovery device for recovering particulate adsorbents contained in liquid or slurry by solid liquid separation includes a cartridge filter unit and a compressor for pressurizing the inside of the cartridge filter unit, the cartridge filter unit includes a sludge recovery vessel, and a plurality of filter elements installed inside the sludge recovery vessel, an interval between the inner wall surface of the sludge recovery vessel and the filter element adjacent to the inner wall surface among the plurality of filter elements is equal to or less than a first prescribed value, and an interval between adjacent filter elements among the plurality of filter elements is equal to or less than a second prescribed value.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] The present disclosure relates to an adsorbent recovery apparatus. [Background technology]

[0002] As dehydration treatment technologies for sludge and the like, there are various techniques for treating slurries such as factory effluent and sludge discharged from facilities such as agricultural and livestock industries by filtration using a filter.

[0003] Wastewater generated during decontamination work at facilities contaminated with radioactive materials also needs to be purified by removing solid matter and radioactive materials.

[0004] Patent Document 1 discloses a decontamination waste liquid treatment device that is equipped with a filter unit that separates the waste liquid into filtration residue and filtrate, with regard to the treatment of radioactive waste liquid in which contaminated water and sludge coexist. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-186025 A Summary of the Invention [Problem to be solved by the invention]

[0006] During the fuel debris removal work at the Fukushima Daiichi Nuclear Power Plant (hereinafter referred to as "1F"), it is expected that a large amount of slurry / sludge waste containing a large amount of radioactive materials including alpha nuclides will be generated. In particular, there is concern that waste adsorbent sludge with a very high water content will be generated by the treatment of contaminated water using powdered adsorbent. In addition, storage space is limited within the 1F premises.

[0007] For this reason, there is a demand for technology that can rapidly dehydrate such waste adsorbent sludge.

[0008] It is known that in dehydration treatment by filtration, the finer the particle size, the greater the pressure difference in the equipment during filtration, making dehydration treatment more difficult. The same issue exists with dehydration treatment using cartridge filters. The waste adsorbent sludge to be dehydrated is dominated by fine particles on the order of a few μm, which can make filtration difficult. In particular, the finer the particles, the more significantly they are affected by the cake thickness, so filtration when the cake is thick is an issue.

[0009] The following describes the problems that arise when waste adsorbent sludge and the like is dehydrated using a cartridge filter system.

[0010] When the cake is thick, the water permeability is low, the filtration rate is slow, and a long treatment time is required.

[0011] When a part of the filter element is exposed to the air, an air bypass is formed, making it difficult to increase the filtration pressure.

[0012] As the filtration process progresses, the cake that is formed increases in particle packing density and adheres to the surface of the filter element, reducing water permeability and making filtration difficult.

[0013] An object of the present disclosure is to keep the thickness of the cake formed during dehydration treatment by filtration of a liquid or slurry containing a particulate adsorbent or the like within an appropriate range, and to prevent a decrease in the filtration rate. [Means for solving the problem]

[0014] The adsorbent recovery device disclosed herein is a device that recovers particulate adsorbent contained in a liquid or slurry by solid-liquid separation, and comprises a cartridge filter unit and a compressor that pressurizes the inside of the cartridge filter unit, and the cartridge filter unit has a sludge collection container and a plurality of filter elements installed inside the sludge collection container, wherein the distance between the inner wall surface of the sludge collection container and a filter element among the plurality of filter elements that is closest to the inner wall surface is equal to or less than a first predetermined value, and the distance between adjacent filter elements among the plurality of filter elements is equal to or less than a second predetermined value. Effect of the Invention

[0015] According to the present disclosure, the thickness of the cake generated during dehydration treatment by filtration of a liquid or slurry containing a particulate adsorbent or the like can be kept within an appropriate range, thereby preventing a decrease in the filtration rate. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a powder adsorbent recovery device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a flow diagram showing an example of treatment of radioactive liquid waste using a powder adsorbent. [Figure 3A] FIG. 2 is a configuration diagram showing details of the cartridge filter unit of FIG. 1. [Figure 3B] FIG. 3B is a cross-sectional view showing the cartridge filter unit of FIG. 3A. [Figure 4] 1 is a graph showing the relationship between filtration rate and cake thickness when titanium silicate is used as the adsorbent. [Diagram 5] 1 is a graph showing the relationship between filtration rate and cake thickness when activated carbon is used as the adsorbent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The adsorbent recovery device according to the present disclosure will be described below using examples. In the examples, a powder adsorbent containing radioactive substances is handled, which is generated as a result of mixing a powder adsorbent with radioactive liquid waste and adsorbing and separating radioactive substances contained in the radioactive liquid waste with the powder adsorbent. In other words, a dehydration process is performed by filtering waste adsorbent sludge containing a large amount of radioactive substances. Therefore, the powder adsorbent contains radioactive substances adsorbed and separated from the radioactive liquid waste. EXAMPLES

[0018] FIG. 1 is a schematic diagram showing the configuration of a powder adsorbent recovery apparatus (also simply referred to as an "adsorbent recovery apparatus") according to an embodiment.

[0019] In this figure, the powder adsorbent recovery apparatus 100 includes a waste liquid storage tank 102, a cross-flow concentration section 103, a sedimentation section 105, a flocculant supply section 106, a pH adjuster supply section 107, and a cartridge filter unit 108. The waste liquid storage tank 102 includes a submersible pump 109. The cross-flow concentration section 103 includes a cross-flow filter element 104.

[0020] A connection pipe 110 for supplying a powder adsorbent-containing slurry is connected to the waste liquid storage tank 102. A submersible pump 109 of the waste liquid storage tank 102 and a slurry inlet of the cross-flow concentration section 103 are connected by a connection pipe 111. A valve 118 is provided on the connection pipe 111.

[0021] The slurry outlet of the cross-flow concentrating section 103 and the waste liquid storage tank 102 are connected by a connection pipe 112. The connection pipe 112 is provided with a valve 119.

[0022] A branch pipe, that is, a connection pipe 113, is connected to the connection pipe 112. The connection pipe 113 is connected to the sedimentation section 105. The connection pipe 113 is provided with a valve 120.

[0023] A flocculant is supplied to the settling section 105 from a flocculant supply section 106 via a connection pipe 114. A pH adjuster (water quality adjuster) is also supplied to the settling section 105 from a pH adjuster supply section 107 via a connection pipe 115. The settling section 105 and the cartridge filter unit 108 are connected by a connection pipe 116. Adsorption-treated water (filtrate) flows out from the cartridge filter unit 108 via a connection pipe 123. A valve 121 is provided on the connection pipe 116.

[0024] The filtrate outflow portion of the cross-flow concentrating section 103 is connected by a connecting pipe 117. The connecting pipe 117 is provided with a valve 122. The adsorption-treated water flows out from the filtrate outflow portion of the cross-flow concentrating section 103 via the connecting pipe 117.

[0025] FIG. 2 is a flow diagram showing an example of treatment of radioactive liquid waste with a powder adsorbent.

[0026] In this diagram, first, an adsorbent is supplied to radioactive liquid waste (adsorption treatment step S11). Then, in a cross-flow concentration treatment step S12, an adsorbent-containing slurry, which is a mixture of radioactive liquid waste and an adsorbent, is separated into a cross-flow concentrated water (cross-flow concentrated slurry) and a separated liquid. Next, in a sedimentation separation treatment step S13, a flocculant and a water quality conditioner are supplied to the cross-flow concentrated water, thereby separating it into a precipitated sludge and a separated liquid. Then, in a cartridge filter treatment step S14, the precipitated sludge is separated into a cake and a separated liquid.

[0027] FIG. 3A is a configuration diagram showing details of the cartridge filter unit of FIG.

[0028] 3A, cartridge filter unit 108 incorporates a plurality of filter elements 303. Filter elements 303 are each cylindrical, and are arranged in a vertically upright state at the bottom of the sludge collection container of cartridge filter unit 108.

[0029] The powder adsorbent-containing slurry is supplied to the cartridge filter unit 108 via a connecting pipe 116. A valve 308 is provided to the connecting pipe 116. A compressor 304 is also connected to the cartridge filter unit 108 via the connecting pipe 306. A valve 309 is provided to the connecting pipe 306.

[0030] The powder adsorbent-containing slurry is supplied to the outside of the filter element 303 in the internal space of the cartridge filter unit 108. The liquid contained in the powder adsorbent-containing slurry flows into the inside of the filter element 303 and flows out as adsorption-treated water via the connection pipe 123. The connection pipe 123 is provided with a valve 310. The powder adsorbent contained in the powder adsorbent-containing slurry accumulates as a cake on the outer surface of the filter element 303. It is preferable that the connection pipes 123 are individually provided on the downstream side of each filter element 303 as shown in this figure.

[0031] Solid-liquid separation in cartridge filter unit 108 is promoted by pressurizing the inside of cartridge filter unit 108 with air sent from compressor 304 .

[0032] FIG. 3B is a cross-sectional view showing the cartridge filter unit of FIG. 3A.

[0033] 3B, inside the cartridge filter unit 108, a plurality of filter elements 303 are arranged with a fixed distance between adjacent filter elements 303. In other words, three adjacent filter elements 303 form an equilateral triangle with the center of each element as an apex. It can also be expressed that the centers of the seven filter elements 303 form the apexes and center of gravity of a regular hexagon.

[0034] The distance a (shown by a dotted line in the figure) between the inner wall surface of the sludge collection container of the cartridge filter unit 108 and the filter elements 303 (the filter elements 303 adjacent to the inner wall surface) constituting the vertices of a regular hexagon is desirably about half the distance b (shown by a dotted line in the figure) between adjacent filter elements 303. This is because, whereas cake accumulated between the inner wall surface of the sludge collection container and the filter element 303 is dewatered only from the surface in contact with the filter element 303, cake accumulated between adjacent filter elements 303 is dewatered from both surfaces in contact with the two filter elements 303.

[0035] If the above two types of intervals a and b are set to be equal to or less than predetermined values, the number of filter elements 303 may be increased.

[0036] Here, the interval a is referred to as a “first predetermined value,” and the interval b is referred to as a “second predetermined value.” The second predetermined value is preferably 1.5 times or more and 2 times or less of the first predetermined value.

[0037] With this configuration, the thickness of the cake accumulated on the outside of the filter element 303 is kept below a predetermined value, so that the filtration resistance of the cake can be suppressed to a predetermined value or less, and the filtration speed (dewatering speed) can be maintained.

[0038] The thicker the cake, the slower the filtration rate. Figures 4 and 5 show the results of an experimental study on this issue using a specific adsorbent.

[0039] In the experiment, the adsorbent slurry was filtered, and the amount of treated liquid discharged as filtrate [ml], treatment time [min], and filtration area [mm 2 ] was used to calculate the average filtration rate per unit area.

[0040] Figure 4 is a graph showing the relationship between filtration rate and cake thickness when titanium silicate (crystallized silicotitanate (CST), particle size approximately 5 μm) is used as the adsorbent. The horizontal axis shows the average filtration rate per unit area, and the vertical axis shows the cake thickness of titanium silicate. The horizontal axis is a logarithmic scale.

[0041] In this figure, the experimental data are indicated by marks ●, and the approximate straight line obtained by the least squares method is indicated by a dotted line.

[0042] The approximation line shown in this figure is expressed by the following formula (1) when the horizontal axis is x1 and the vertical axis is y1.

[0043]

number

[0044] Figure 5 is a graph showing the relationship between filtration rate and cake thickness when activated carbon (particle size approximately 50 μm) is used as the adsorbent. The horizontal axis shows the average filtration rate per unit area, and the vertical axis shows the cake thickness of the activated carbon. The horizontal axis is a logarithmic scale.

[0045] In this figure, the experimental data are indicated by marks ●, and the approximate straight line obtained by the least squares method is indicated by a dotted line.

[0046] The approximation line shown in this figure is expressed by the following formula (2) when the horizontal axis is x2 and the vertical axis is y2.

[0047]

number

[0048] The above y1 and y2 are reference values ​​when setting the first predetermined value, which is the interval a in FIG. 3B.

[0049] In summary, the first specified value and the second specified value are values ​​calculated using an equation that expresses the relationship between the average filtration rate per unit area for the particulate adsorbent and the cake thickness and that corresponds to the particle size of the particulate adsorbent.

[0050] The above formula (1) holds when the particle size is approximately 5 μm, and the above formula (2) holds when the particle size is approximately 50 μm. However, the formula expressing the relationship between the filtration rate and the cake thickness can be expanded by using the particle size as a parameter.

[0051] In this specification, taking into consideration the correlation in filtration theory, when the particle size is in the range of 1 to 100 μm and the particle size is a value r (μm) other than 5 μm or 50 μm, the first predetermined value is set to y (r) and the following formula (3) is used for approximation.

[0052] y(r)=((y2-y1) / (50-5))×(r-5) …(3) (where 1≦r≦100) In the above formula (3), "50" and "5" indicate that particle sizes of 5 μm and 50 μm are used.

[0053] Next, a specific configuration of the cartridge filter unit 108 shown in FIGS. 3A and 3B will be described.

[0054] The cartridge filter unit 108 includes seven filter elements 303 and a sludge collection container (outer container) which is a unit can containing the seven filter elements 303. The dimensions of the outer container are 210 mm in diameter and 800 mm in height. The dimensions of one filter element 303 are 30 mm in diameter and 500 mm in height. The water to be treated is assumed to be 2.2 x 10 liters of treated liquid as the treatment condition during the 1F fuel debris removal period. 5 The treatment time was set to 24 x 60 min. The powder adsorbent was CST with a particle size of about 5 μm. The SS concentration was 10,000 ppm. Here, SS is an abbreviation for Suspended Solids, which refers to insoluble substances suspended in water (also called "suspended solids" or "floating solids").

[0055] In the cartridge filter unit 108 shown in FIGS. 3A and 3B, it is preferable to carry out the dewatering process by the following steps.

[0056] A predetermined amount of liquid or slurry to be treated containing the powder adsorbent (powder adsorbent-containing slurry) is supplied to the cartridge filter unit 108. Next, some or all of the valves 310 provided in each of the multiple connection pipes 123 are opened, and the compressor 304 is operated to perform dehydration treatment by pressurization. Then, the filter element 303 is switched so as to maintain the dehydration speed. In this case, it is preferable to detect the dehydration speed (amount of filtrate) for each of the multiple connection pipes 123 and control so as to open the valve 310 of the appropriate connection pipe 123 that can maintain the dehydration speed. This allows the filtration process to be continued while maintaining a sufficiently high dehydration speed for the entire cartridge filter unit 108. Note that the data detected in the above control may be the pressure in the connection pipes 123 instead of the dehydration speed.

[0057] The above series of steps continues until the cartridge filter unit 108 is sufficiently filled with cake or until the dewatering rate falls below a predetermined value.

[0058] The cake accumulated in the cartridge filter unit 108 is removed together with the cartridge filter unit 108 and moved to a storage location.

[0059] In other words, the above control can be switched between opening and closing the valve 310 to allow or stop the flow of filtrate from each of the multiple filter elements 303 .

[0060] As a result, even if cake adheres to one filter element, making filtration difficult, the filtration process can be continued using another filter element.

[0061] In the above examples, the powder adsorbent is described as being titanium silicate CST and activated carbon, but the powder adsorbent of the present disclosure is not limited to these and may be titanate monosodium titanate (MST), impregnated activated carbon (e.g., oxine-impregnated activated carbon), iron oxide, etc. In other words, the powder adsorbent has titanium silicate, titanate, activated carbon, iron oxide, etc. as the main component or base material. The powder adsorbent is an aggregate of particulate adsorbents, and the particle diameter (particle size) is assumed to be approximately 1 mm or less, but the particle size is not limited to this and may be approximately several mm. [Explanation of symbols]

[0062] 100: powder adsorbent recovery device, 102: waste liquid storage tank, 103: cross-flow concentration section, 104: cross-flow filter element, 105: sedimentation separation section, 106: coagulant supply section, 107: pH adjuster supply section, 108: cartridge filter unit, 109: submersible pump, 110, 111, 112, 113, 114, 115, 116, 117, 123, 306: connecting piping, 118, 119, 120, 121, 122, 308, 309, 310: valve, 303: filter element, 304: compressor.

Claims

1. An apparatus for recovering a particulate adsorbent contained in a liquid or slurry by solid-liquid separation, comprising: A cartridge filter unit; a compressor for pressurizing the inside of the cartridge filter unit, The cartridge filter unit includes a sludge collection container and a plurality of filter elements disposed inside the sludge collection container. a distance between an inner wall surface of the sludge collection container and a filter element among the plurality of filter elements that is closest to the inner wall surface is equal to or less than a first predetermined value; the distance between adjacent filter elements among the plurality of filter elements is equal to or less than a second predetermined value.

2. The adsorbent recovery device of claim 1, wherein the first specified value and the second specified value are values ​​calculated using an equation expressing the relationship between the average filtration rate per unit area for the particulate adsorbent and the cake thickness, the equation corresponding to the particle size of the particulate adsorbent.

3. 2. The adsorbent recovery device according to claim 1, wherein the particulate adsorbent is composed mainly or mainly of titanium silicate, titanate, activated carbon or iron oxide.

4. 2. The adsorbent recovery apparatus according to claim 1, wherein the second predetermined value is 1.5 times or more and 2 times or less than the first predetermined value.

5. 3. The adsorbent recovery apparatus according to claim 2, wherein the first predetermined value is calculated as follows. The equation expressing the relationship between the average filtration rate and the cake thickness is When the particle size is 5 μm, it is represented by the following formula (1): [0010] (In the formula, the average filtration rate is x1 and the cake thickness is y1.) When the particle size is 50 μm, it is represented by the following formula (2): [0025] (Wherein, the average filtration rate is x2 and the cake thickness is y2.) When the particle size is a value r (μm) other than 5 μm or 50 μm, the particle size can be expressed by the following formula (3) where the first predetermined value is y (r). y(r)=((y2-y1) / (50-5))×(r-5)...(3) (where 1≦r≦100)

6. 2. The adsorbent recovery apparatus according to claim 1, wherein the filter element is cylindrical and is arranged in a vertical position on the bottom of the sludge recovery vessel.

7. A connecting pipe is provided downstream of each of the plurality of filter elements, Each of the connecting pipes is provided with a valve; 2. The adsorbent recovery device according to claim 1, further comprising a valve that opens or closes the valve to switch between starting and stopping the flow of filtrate from each of the plurality of filter elements.

8. 2. The adsorbent recovery device according to claim 1, wherein the particulate adsorbent contains radioactive substances adsorbed and separated from radioactive liquid waste.

Images