Bentonite purifying and stirring production device

Abstract

The invention discloses and provides a bentonite purifying and stirring production device. Polluted bentonite is classified into gravel, sand and bentonite; and a bentonite purification unit (2) for purifying the sand separated in the bentonite classification unit with a chelating cleaning solution. The bentonite purification unit (2) has a bentonite cleaning unit (14), a chelating agent regeneration unit (15), a bentonite flushing unit (16), and a chelating agent recovery unit (17). The bentonite cleaning unit (14) cleans the sand discharged from the bentonite classification unit (1). The chelating agent regeneration unit (15) regenerates the chelating cleaning liquid and returns the chelating cleaning liquid to the bentonite cleaning unit (14). A bentonite flushing unit (16) cleans the sand discharged from the bentonite cleaning unit (14) with flushing water. A chelating agent recovery unit (17) recovers a chelating agent from the cleaning wastewater discharged from the bentonite flushing unit (16).

Description

Technical Field

[0001] This invention relates to a bentonite purification and stirring production apparatus, which separates bentonite contaminated with harmful metals or their compounds into gravel, sand and soil in a bentonite grading section, and purifies the sand separated in the bentonite grading section with a chelating cleaning solution containing chelating agents and water. Background Technology

[0002] In recent years, bentonite contamination has become a problem. This includes bentonite contamination at or near production facilities that use hazardous metals such as chromium, lead, cadmium, selenium, and mercury, and / or their compounds (hereinafter collectively referred to as "hazardous metals, etc.") as raw materials, or bentonite contamination caused by the illegal dumping of industrial waste containing hazardous metals, etc. Furthermore, effective remediation at the existing site of bentonite contaminated with hazardous metals (hereinafter referred to as "hazardous metal-contaminated bentonite") (hereinafter referred to as the "original site") is quite difficult through methods such as insoluble treatment, sealing, or electroremediation of the hazardous metals, etc. Therefore, hazardous metal-contaminated bentonite is usually removed from the original site by excavation and then purified in external bentonite remediation facilities.

[0003] Traditionally, a widely used method for purifying bentonite contaminated with harmful metals in off-site bentonite remediation facilities involves washing the bentonite with a cleaning solution to remove the harmful metals. In light of this, the inventors of this application propose several closed-system bentonite remediation facilities that use a chelating cleaning solution containing a chelating agent and water, which is recycled. This process wet-classifies the bentonite into gravel, sand, and soil while simultaneously removing harmful metals adhering to or bound to the bentonite. Summary of the Invention

[0004] This invention was made to solve the aforementioned problems. Its purpose is to provide a means in a closed-system bentonite purification facility that uses a chelating agent to purify bentonite contaminated with harmful metals, and to separate sand from the bentonite for reuse, thereby reducing the amount or flow of chelating agent in the bentonite purification facility, preventing or reducing the chelating agent from being carried out of the bentonite purification facility by sand, and reducing the floor space occupied by the equipment used to recover the chelating agent.

[0005] To solve the above problems, the present invention adopts the following technical solution: a bentonite purification and mixing production device for purifying bentonite containing gravel, sand, and soil and contaminated with harmful metals or their compounds. The bentonite purification and mixing production device comprises: classifying the bentonite into gravel, sand, and soil; and washing and purifying the sand and gravel separated from the bentonite with a washing solution of a chelating agent and water. The bentonite purification device includes: a mixing device for mixing the bentonite fed into the bentonite classification section and washing water; a drum screen for separating gravel from the mixture of bentonite and washing water discharged from the mixing device; and a hydrocyclone for separating the sand, soil, and washing water from the mixture discharged from the drum screen. The bentonite purification unit comprises: a sand separator; a thickener for separating a mixture of mud and washing water discharged from the hydrocyclone into a supernatant and sludge containing mud by sedimentation separation; and a filter press for filtering the sludge discharged from the thickener to separate the mud, the bentonite purification unit comprising: a bentonite washing unit for washing the bentonite discharged from the hydrocyclone with a chelating washing solution to remove harmful metals or their compounds therefrom; a chelating agent regeneration unit for removing harmful metals or their compounds contained in the chelating agent in the chelating washing solution discharged from the bentonite washing unit to regenerate the chelating agent and returning it to the bentonite washing unit; washing the sand discharged from the bentonite washing unit with rinsing water to remove the chelating agent; and the chelating agent return... The receiving section recovers the chelating agent from the cleaning wastewater containing the chelating agent discharged from the bentonite washing section. The bentonite washing section includes: a flow-through mixer for mixing and agitating the sand and chelating cleaning liquid discharged from the hydrocyclone, so that harmful metals or their compounds adhering to or bound to the bentonite are captured by the chelating agent; a vibrating screen for removing the chelating cleaning liquid from the mixture of bentonite and chelating cleaning liquid discharged from the mixer; and a belt filter press having a porous, endless belt wound and circulating on multiple rollers, and an upper and lower belt mechanism opposite to each other, receiving the bentonite wetted by the chelating cleaning liquid discharged from the vibrating screen and clamping it in the upper belt mechanism. The upper belt mechanism is used for conveying between the upper and lower belt mechanisms. In the part opposite to the lower belt mechanism, a pressurized air supply device is provided on the upper belt mechanism. The pressurized air flows downward through the endless belt of the upper belt mechanism, the bentonite layer sandwiched between the upper and lower belt mechanisms, and the endless belt of the lower belt mechanism to reduce the content of bentonite in the chelating cleaning solution. The chelating agent regeneration section has a chelating cleaning solution regeneration device with a solid phase adsorption material. The complexation generation capacity of this material is higher than that of the chelating agent. When it comes into contact with the chelating cleaning solution, it adsorbs harmful metals or their compounds in the chelating cleaning solution and removes the harmful metals or their compounds from the chelating agent in the chelating cleaning solution.The bentonite rinsing section includes a chelating agent removal device, which removes the chelating agent from the bentonite by spraying or jetting rinsing water onto the sand discharged from the bentonite rinsing section. The chelating agent recovery section includes: a cleaning wastewater storage tank for receiving and storing cleaning wastewater containing chelating agents discharged from the bentonite rinsing section; a bentonite storage section, located on the ground, in the form of an open-top container; the opening is located above the bentonite storage section to prevent rainwater from falling into the bentonite storage section; and a cleaning wastewater dispersing device for spraying the cleaning wastewater stored in the cleaning wastewater storage tank. The bentonite is sprinkled into the bentonite storage section; the cleaning wastewater return mechanism is used to clean the bentonite in the bentonite storage section, and excess cleaning wastewater is returned to the cleaning wastewater storage tank. This bentonite purification and stirring production device also includes: continuously distributing cleaning wastewater from the cleaning wastewater distribution device for a predetermined period; evaporating the water from the cleaning wastewater distributed onto the bentonite for water evaporation into the air; transferring the sand for water evaporation in the bentonite storage section to the bentonite cleaning section; and supplying a portion of the bentonite discharged from the bentonite rinsing section as bentonite for water evaporation to the bentonite storage section.

[0006] In the bentonite purification method related to the present invention, fine sand is preferably used as sand for water evaporation, and the amount of cleaning wastewater distributed from the cleaning wastewater distribution device to the bentonite storage section is set such that the water content of the sand for water evaporation contained in the bentonite storage section is maintained at 30 to 35%.

[0007] In this invention, the chelating agent is added to the large volume of cleaning water in the internal circulation system of the bentonite purification and stirring production apparatus. Instead, the sand discharged from the hydrocyclone is cleaned with a chelating cleaning solution. Furthermore, since the sand cleaned with the chelating cleaning solution is washed with rinsing water in the bentonite rinsing section, sand free of chelating agents and suitable for reuse can be obtained. Further, since the chelating cleaning solution content of the sand wetted by the chelating cleaning solution is reduced by the pressurized air supply device in the belt filter press, the amount of rinsing water used in the bentonite rinsing section, i.e., the amount of cleaning wastewater that needs to be evaporated, can be reduced, thereby reducing the floor space occupied by the bentonite storage section in the chelating agent recovery section. Attached Figure Description

[0008] Figure 1 A block diagram illustrating the bentonite purification and mixing production apparatus related to this invention.

[0009] Figure 2 To display the composition Figure 1 This is a schematic diagram of the bentonite grading section, which is part of the bentonite purification and mixing production device.

[0010] Figure 3 To display the composition Figure 1The diagram shows a schematic outline of the bentonite purification section, which is part of the bentonite purification and mixing production apparatus.

[0011] Figure 4 Display components Figure 3 The diagram shows the bentonite cleaning section of the bentonite purification unit.

[0012] Figure 5 To display the composition Figure 3 The diagram shows the structure of the regeneration unit.

[0013] Figure 6 To display the composition Figure 3 The diagram shows the bentonite rinsing section of the bentonite purification unit.

[0014] Figure 7 To display Figure 1 The diagram shows the structure of a bentonite purification and mixing production unit (excluding the chelating agent regeneration section).

[0015] Figure 8 This is a cross-sectional view of the sand container, the wastewater distribution device, and the roof, taken on a plane perpendicular to the length (front-to-back) direction of the bentonite storage.

[0016] Figure 9 This is a floor plan of the bentonite storage area after the roof and frame structure have been removed.

[0017] Labeling Explanation: 1. Bentonite Grading Section, 2. Bentonite Purification Section, 3. Feed Hopper, 4. Mixer, 5. Grinding Mill, 6. Rotary Drum Screen, 7. Hydrocyclone, 8. pH Adjustment Tank, 9. Flocculation Tank, 10. Thickener, 11. Cleaning Water Storage Tank, 12. Intermediate Tank, 13. Filter Press, 14. Bentonite Cleaning Section, 14A. Mixing Agitator, 14B. Vibrating Screen, 14C. Belt Filter Press, 15. Chelating Agent Regeneration Section, 16. Bentonite Washing Section, 17. Chelating Agent Recovery Section, 20. Main Body, 21. Baffle, 22. Mixer, 23. Motor, 24. Metal Mesh, 25. Shell, 26. Piping, 27. Cleaning Liquid Storage Tank, 28. Lower Belt Mechanism, 29. Upper Belt Mechanism, 30. Lower Drive Roller, 31. Lower Driven Roller, 32. Endless Belt, 33. Upper Drive Roller, 34. Upper driven roller, 35 Endless belt, 36 Chelating cleaning solution receiving tank, 37 Drain pipe, 38 Pressurization chamber, 39 Air supply pipe, 40 Air pump (blower), 41 Packing tower, 42 Intermediate storage tank, 43 Regenerated chelating cleaning solution storage tank, 44 Acid storage tank, 45 Water storage tank, 46 Pump, 47-50 Pipelines, 51 Pump, 52 Pipeline, 53 Pump, 54, 55 Pipelines, 56 Pump, 57, 58 Pipelines, 61-68 Valves, 70 Belt conveyor, 71 Bentonite supply device, 72 Rinse water distribution device, 73 Cleaning wastewater receiving tank, 74 Drive roller, 74a shaft, 75 Driven roller, 75a shaft, 76 Conveyor belt, 77 Support roller, 78 Guide plate, 83 Cleaning wastewater passage, 84 85 Cleaning wastewater storage tank, 86 Bentonite storage section, 87 Front wall, 88 Rear wall, 89 Right wall, 90 Bottom wall, 92 Roof, 93 Cleaning wastewater distribution device, 94 Cleaning wastewater return mechanism, 100 Ground, 101 Drainage ditch, 102 Water collection and drainage ditch, 103 Protrusion, 104 Perforated plate, 105 Sand layer, 107 Left vertical frame, 108 Right vertical frame, 109 Horizontal frame, 111 Water supply pipe, 112 Water discharge nozzle, 113 Intermediate pipe, 114 Cleaning wastewater supply pipe, 115 Cleaning wastewater supply pump. Detailed Implementation

[0018] Hereinafter, with reference to the accompanying drawings, a bentonite purification and stirring production apparatus related to an embodiment of the present invention will be specifically described.

[0019] like Figure 1 As shown, the bentonite purification and mixing production apparatus includes: a bentonite classification section 1 that wet-classifies contaminated bentonite into gravel, sand and soil using washing water; and a bentonite purification section 2 that washes and purifies the sand separated in the bentonite classification section 1 with a chelating cleaning solution containing a chelating agent and water.

[0020] like Figure 2As shown, in the bentonite grading section 1, bentonite (contaminated bentonite) collected by excavating sites contaminated with harmful metals or other pollutants is received in the feed hopper 3. The bentonite in the feed hopper 3 is then first fed into a container-shaped mixer 4, where it is mixed with washing water. Here, the bentonite includes gravel (2–75 mm), sand (0.075–2 mm), and soil (silt or clay with a particle size of less than 0.075 mm) of various sizes. The bentonite in the feed hopper 3 is contaminated with harmful metals, and sometimes with other pollutants. Examples of harmful metals include chromium, lead, cadmium, selenium, mercury, metallic arsenic, and their compounds. The chelating washing solution described later is a substance capable of effectively capturing (removing) such harmful metals.

[0021] The mixture of bentonite and washing water generated in mixer 4 (hereinafter referred to as the "bentonite-water mixture") is transferred to mill 5. Mill 5 can be, for example, a rod mill. Although not shown in detail, a rod mill is a device in which multiple rods (steel rods) are arranged inside a drum. The rotation of the drum causes the rods to roll parallel to each other and make line contact, using impact force, friction, etc., to peel off and remove harmful metals and other substances adhering to or fixed on the gravel. Most of the harmful metals and other substances that detach into the washing water are attached to the surface of the sand and soil (fine-grained soil) particles.

[0022] The bentonite-water mixture discharged from the grinder 5 is introduced into the drum screen 6. Although not shown in detail, the drum screen 6 is a wet screening device comprising a tank for storing washing water and a generally cylindrical drum screen arranged at an angle relative to the horizontal plane. The drum screen can be rotated about its central axis by a motor. Furthermore, washing water can be sprayed in a mist form inside the drum screen.

[0023] When the bentonite-water mixture flows inside the rotating drum screen of the drum screen 6, bentonite particles (sand, soil) finer than the mesh size of the drum screen pass through the mesh along with the washing water, flow out of the drum screen, and enter the receiving tank. On the other hand, bentonite particles (gravel) coarser than the mesh size of the drum screen cannot pass through the mesh and are therefore discharged out of the drum screen through the open end on the lower side of the drum screen.

[0024] The screening particle size of the drum screen is set such that, for example, bentonite particles (sand, soil) with a particle size less than 2 mm can pass through the mesh of the drum screen. Therefore, in drum screen 6, bentonite particles with a particle size greater than 2 mm (i.e., gravel) are separated from the bentonite-water mixture. It should be noted that the size of the drum screen of drum screen 6 is not limited to the above-mentioned size and can be arbitrarily set according to the desired particle size of the larger bentonite particles.

[0025] A bentonite-water mixture containing bentonite particles (sand, soil) with a particle size less than 2 mm and washing water, collected in the receiving trough of the rotary screen 6, is introduced into a hydrocyclone 7. A pump forces the bentonite-water mixture into a downwardly narrowing, generally conical cylinder, creating a swirling current. Using the resulting centrifugal force, the bentonite-water mixture is separated into a mixture of smaller soil particles (e.g., less than 0.075 mm) and washing water (with washing water comprising the majority), and a mixture of larger sand particles (e.g., greater than 0.075 mm) and washing water. The mixture of soil and washing water (hereinafter referred to as "soil-containing water") is then discharged from the upper end of the hydrocyclone 7, while the mixture of sand and washing water is discharged from the lower end. The soil-containing water is then transferred to a pH adjustment tank 8. The mud in the muddy water is, for example, silt or clay with a particle size of less than 0.075 mm. The mixture of sand and washing water discharged from the lower end of the hydrocyclone 7 is transferred to the bentonite purification section 2 after the proportion of washing water is reduced, for example, by using a vibrating screen. (See...) Figure 3 ).

[0026] The muddy water discharged from hydrocyclone 7 is introduced into pH adjustment tank 8, where its pH (hydrogen ion index) is adjusted to approximately neutral or a predetermined pH (e.g., pH 7-8) using pH adjusters such as acids (e.g., sulfuric acid, hydrochloric acid, etc.) and alkalis (e.g., aqueous sodium hydroxide solution, etc.). The pH-adjusted muddy water in pH adjustment tank 8 is then introduced into flocculation tank 9. In flocculation tank 9, polyaluminum chloride solution (PAC), a polymeric flocculant, and a pH adjuster (acid or alkali) are added to the muddy water. This results in the formation of numerous flocs containing both insoluble metal hydroxides and mud within flocculation tank 9.

[0027] The muddy water containing a large amount of flocculent material in the aforementioned flocculation tank 9 is introduced into the thickener 10. In the thickener 10, where the muddy water is essentially still, gravity causes the flocculent material or mud to settle, forming a sludge layer at the bottom (e.g., with a solids content of 5-10%) and a supernatant (washing water) at the top, which contains almost no flocculent material or mud. It should be noted that when oil floats on the surface of the supernatant, it can be removed, for example, by floating an oil-absorbing pad on the surface of the water in the thickener 10 and then recovering the oil-absorbing pad in a timely manner.

[0028] The supernatant in the aforementioned thickener 10 is introduced into the cleaning water storage tank 11 and stored. The cleaning water stored in the cleaning water storage tank 11 is supplied to the mixer 4 and the drum screen 6. When the cleaning water stored in the cleaning water storage tank 11 decreases due to evaporation, etc., water (industrial water, tap water, etc.) is added as needed. The sludge accumulated at the bottom of the thickener 10 is transferred to the intermediate tank 12 for temporary storage. The sludge in the intermediate tank 12 is transferred to the filter press 13 as needed or continuously. The filter press 13 is an intermittent or semi-continuous pressure filter that pressurizes the sludge received from the intermediate tank 12 to produce a filter cake (soil) and filtrate (cleaning water). The filtration pressure of the filter press 13 is preferably set such that, for example, the moisture content of the filter cake reaches 30-40%. Here, the filtrate from the filter press 13 is returned to the thickener 10. In this way, the cleaning water is circulated within the bentonite classification section 1 and is not discharged to the outside. That is, the bentonite grading section 1 is a closed system for the washing water.

[0029] like Figure 3 As shown, the bentonite purification unit 2 includes a bentonite washing unit 14, a chelating agent regeneration unit 15, a bentonite rinsing unit 16, and a chelating agent recovery unit 17. Here, the bentonite washing unit 14 washes the sand discharged from the hydrocyclone 7 with a chelating cleaning solution containing a chelating agent and water, removing harmful metals and the like from the sand. The chelating agent regeneration unit 15 removes harmful metals and the like contained in the chelating agent from the chelating cleaning solution discharged from the bentonite washing unit 14 to regenerate the chelating cleaning solution, and returns it to the bentonite washing unit 14. The bentonite rinsing unit 16 washes the sand discharged from the bentonite washing unit 14 with rinsing water to remove the chelating agent. The chelating agent recovery unit 17 recovers the chelating agent from the cleaning wastewater containing the chelating agent discharged from the bentonite rinsing unit 16.

[0030] like Figure 4 As shown, the bentonite cleaning unit 14 includes a flow-through mixer 14A, a vibrating screen 14B, and a belt filter press 14C. The mixer 14A is used to mix and agitate the sand and chelating cleaning liquid discharged from the hydrocyclone 7, so that harmful metals or other contaminants adhering to or bound to the bentonite are captured by the chelating agent. The vibrating screen 14B is used to remove most of the chelating cleaning liquid from the mixture of bentonite and chelating cleaning liquid discharged from the mixer 14A. The belt filter press 14C, as described in detail below, is used to receive the bentonite wetted by the chelating cleaning liquid discharged from the vibrating screen 14B, reducing its chelating cleaning liquid content (or chelating cleaning liquid percentage) while conveying the sand.

[0031] Specifically, the mixing agitator 14A includes: a slender, generally cylindrical body 20 with a central shaft extending vertically; a plurality of baffles 21 (baffles) mounted on the inner circumferential surface of the body 20; a mixer 22 disposed within the body 20; and a motor 23 for driving the mixer 22 to rotate. Each baffle 21 is basically an annular shape with a hole formed in the center, but is formed into an inwardly downward inclined cone shape to promote the downward movement of bentonite.

[0032] The mixer 22 has multiple stirring blades or impellers mounted on a rotating shaft extending in the vertical direction. The shape or size of the stirring blades is set so that they can pass through the holes of each baffle 21. Here, each baffle 21 and each stirring blade of the mixer 22 are arranged alternately in the vertical direction.

[0033] The dimensions of the body 20 are preferably set to ensure that the chelating cleaning fluid and sand particles flowing through the body 20 have a predetermined residence time (e.g., 0.1 to 0.3 hours). Furthermore, the number, shape, and rotational speed of each stirring blade of the mixer 22 are preferably set to achieve a turbulence level (e.g., Reynolds number 20,000 to 100,000) within the body 20 that allows the sand particles to be dispersed approximately uniformly in the chelating cleaning fluid.

[0034] Then, bentonite and chelating cleaning fluid are supplied to the upper opening of the body section 20, and the chelating cleaning fluid and bentonite particles are mixed by the mixer 22. As a result, a mixture in which bentonite particles are substantially uniformly dispersed in the chelating cleaning fluid (hereinafter referred to as the "bentonite-cleaning fluid mixture") is generated. This bentonite-cleaning fluid mixture flows downward at a slow speed within the body section 20 while being stirred by multiple stirring blades of the mixer 22. In this way, within the mixing mixer 14A, the bentonite particles come into contact with the chelating cleaning fluid, and harmful metals and the like adhering to the surface of the sand particles in the bentonite-cleaning fluid mixture are removed. It should be noted that the baffle 21 increases the turbulence (Reynolds number) of the sand-cleaning fluid mixture within the body section 20, thereby promoting the removal or detachment of harmful metals and the like from the sand particles.

[0035] Examples of chelating agents used in chelating cleaning solutions include sodium salts of EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2'-iminodisuccinic acid), IDS (2,2'-iminodisuccinic acid), MGDA (methylglycine diacetic acid), EDDS (ethylenediaminedisuccinic acid), or GLDA (L-glutamic acid diacetic acid). These chelating agents are effective in capturing (chelating) harmful metals attached to or bound to sand particles. Depending on the type of harmful metal attached to or bound to the sand, a suitable chelating agent may be selected, or multiple chelating agents may be used.

[0036] After removing harmful metals from the bentonite, the bentonite cleaning solution mixture is introduced into the vibrating screen 14B through the lower opening of the main body 20, from which most of the chelating cleaning solution is separated. The vibrating screen 14B is an inclined type vibrating screen with a metal mesh 24 having a predetermined mesh size, arranged at an angle within the housing 25. A circular vibrating screen or similar device can also be used. Alternatively, a stationary inclined screen can be used instead of a vibrating screen. The metal mesh 24 of the vibrating screen 14B uses a mesh size (diameter) that prevents bentonite particles from passing through. The chelating cleaning solution passing through the metal mesh 24 is introduced into the cleaning solution storage tank 27 through the pipe 26 and stored. The chelating cleaning solution stored in the cleaning solution storage tank 27 is then transported to the chelating agent regeneration unit 15, described later.

[0037] On the other hand, sand that cannot pass through the metal mesh 24 of the vibrating screen 14B is introduced into the belt filter press 14C. The sand introduced into the belt filter press 14C is wetted with a chelating cleaning solution, which has a relatively high chelating cleaning solution content (e.g., 20-40%). Therefore, by processing it in this belt filter press 14C, its chelating cleaning solution content is reduced as much as possible.

[0038] The belt filter press 14C is a dual-belt filter press comprising a lower belt mechanism 28 and an upper belt mechanism 29 disposed above it in a vertically opposite direction. The lower belt mechanism 28 includes a lower drive roller 30 and a lower driven roller 31. The lower drive roller 30 is driven by a motor at a predetermined rotational speed in the direction indicated by the arrow (…). Figure 4 The rotation is driven in a clockwise direction. Furthermore, a flexible, porous, endless lower belt 32 (hereinafter referred to as "belt 32") is wound around the lower drive roller 30 and the lower driven roller 31. The belt 32 circulates along a loop between the lower drive roller 30 and the lower driven roller 31.

[0039] The aforementioned upper belt mechanism 29 includes an upper drive roller 33 and an upper driven roller 34. The upper drive roller 33 is driven by a motor (not shown) in the direction indicated by the arrow (…). Figure 4 The upper drive roller 33 (in a counter-clockwise direction) rotates at the same circumferential speed as the lower drive roller 30. Furthermore, a flexible, porous, endless upper belt 35 (hereinafter referred to as "belt 35") is wound around the upper drive roller 33 and the upper driven roller 34. The belt 35 circulates along a loop between the upper drive roller 33 and the upper driven roller 34.

[0040] The belt 32 of the lower belt mechanism 28 and the belt 35 of the upper belt mechanism 29 are respectively formed of a flexible (soft) porous material that allows chelating cleaning liquid and air to pass through but does not allow sand to pass through. The belts 32 and 35 can also be filter media mounting belts on which filter cloth or other filter materials are installed on porous belts.

[0041] In the lower belt mechanism 28, a chelating cleaning fluid receiving tank 36 is arranged between the upper and lower horizontal running paths of the belt 32. The chelating cleaning fluid receiving tank 36 is an open container that receives the chelating cleaning fluid that has detached from the sand and flows downwards through the belt 32. The chelating cleaning fluid in the receiving tank 36 flows down to the cleaning fluid storage tank 27 by gravity through the drain pipe 37. It should be noted that the belt 32 is supported by multiple (many) support rollers in the upper horizontal running path and runs approximately horizontally.

[0042] In the upper belt mechanism 29, a pressurization chamber 38 is provided between the upper and lower horizontal running paths of the belt 35. The pressurization chamber 38 is a container-shaped chamber with an open lower portion, which is closed by the belt 35 running on the lower horizontal running path. The pressurization chamber 38 is connected to an air pump 40 (blower) via an air supply pipe 39. When the belt filter press 14C is running, pressurized air is supplied from the air pump 40 to the pressurization chamber 38, and the pressurization chamber 38 is under pressurization.

[0043] When the belt filter press 14C is operating, the lower drive roller 30 rotates at a predetermined speed in the direction indicated by the arrow (clockwise), while the upper drive roller 33 rotates at the same circumferential speed in the direction indicated by the arrow (counterclockwise). Since the two drive rollers 30 and 33 have the same diameter, they rotate in opposite directions at the same speed. As a result, in Figure 4 In the positional relationship shown, belt 32 circulates clockwise, and belt 35 circulates counterclockwise. Therefore, in the portion where the two belts 32 and 35 are close to each other in the vertical direction, belts 32 and 35 maintain a predetermined interval and run in a straight line in the same direction. The belt filter press 14C receives sand wetted by chelating cleaning liquid discharged from the vibrating screen 14B. Bentonite is conveyed between the two belts 32 and 35 in the portion where the lower belt mechanism 28 and the upper belt mechanism 29 are opposite. At this time, pressurized air is supplied to the inner surface (inside) of belt 35 of the upper belt mechanism 29. This pressurized air flows downward at high speed through belt 35, the bentonite layer sandwiched between the two belts 32 and 35, and belt 32, causing most of the chelating cleaning liquid adhering to the sand to detach from the sand and flow down or fall into the chelating cleaning liquid receiving tank 36. As a result, the bentonite chelating cleaning liquid content becomes very low (e.g., 5-10%). This reduces the proportion of sand in the chelating cleaning solution that is scraped off by the scraper and transferred to the sand rinsing section 16, which will be described later.

[0044] like Figure 5As shown, in the chelating agent regeneration unit 15, a packed tower 41 is provided as a means of regenerating the chelating cleaning solution or chelating agent. The tower is filled with solid-phase adsorbent material particles or a packing material with fixed solid-phase adsorbent material. In addition, the chelating agent regeneration unit 15 is also provided with: an intermediate storage tank 42 for storing the chelating cleaning solution to be regenerated; a regenerated chelating cleaning solution storage tank 43 for storing the regenerated chelating cleaning solution; an acid storage tank 44 for storing acid; and a water storage tank 45 for storing water.

[0045] From cleaning fluid storage tank 27 (see Figure 4 The introduced chelating cleaning solution is temporarily stored in an intermediate storage tank 42. A pump 46 and a series of multiple pipelines 47-50 are provided for transferring the chelating cleaning solution stored in the intermediate storage tank 42 to the packed tower 41 during regeneration, and simultaneously transferring the regenerated chelating cleaning solution in the packed tower 41 to the regeneration chelating cleaning solution storage tank 43. Furthermore, a pump 51 and pipeline 52 are provided for returning the chelating cleaning solution stored in the regeneration chelating cleaning solution storage tank 43 to the bentonite cleaning section 14.

[0046] Furthermore, the chelating agent regeneration unit 15 is equipped with a pump 53 and multiple pipelines 54 and 55 for transferring the acid stored in the acid storage tank 44 to the packed tower 41 during the regeneration of the solid-phase adsorbent material, and simultaneously returning the acid discharged from the packed tower 41 to the acid storage tank 44. Additionally, the chelating agent regeneration unit 15 is equipped with a pump 56 and multiple pipelines 57 and 58 for transferring water stored in the water storage tank 45 to the packed tower 41 during the washing of the solid-phase adsorbent material regenerated by the acid, and simultaneously returning the water discharged from the packed tower 41 to the water storage tank 45. Valves 61, 62, 63, and 64 are respectively installed on the pipelines 47, 48, 54, and 57 that transfer chelating cleaning solution, acid, or water to the packed tower 41 for opening and closing. On the other hand, valves 65, 66, 67, and 68 are respectively installed on pipelines 49, 50, 55, and 58 used to discharge chelating cleaning solution, acid, or water from the packed tower 41 to the corresponding pipelines. By switching the opening and closing states of these valves 61-64 and 65-68, any one of the chelating cleaning solution, acid, or water can be supplied to or discharged from the packed tower 41. It should be noted that the opening and closing of these valves 61-64 and 65-68 is automatically controlled by a controller (not shown).

[0047] This is an example of the operation method of the aforementioned chelating agent regeneration section 15. It should be noted that the operation method described below is merely an example, and the operation method of the chelating agent regeneration section 15 of the present invention is certainly not limited to the following. When regenerating the chelating cleaning solution (chelating agent), valves 61, 62, 65, and 66, which are installed on pipelines 47-50, are opened, while other valves 63, 64, 67, and 68 are closed, and pump 46 is operated. As a result, the chelating cleaning solution in the intermediate storage tank 42 flows through the interior of the packed tower 41 and is transferred to the regenerated chelating cleaning solution storage tank 43. Inside the packed tower 41, the chelating cleaning solution containing the chelating agent that has captured harmful metals, etc., is brought into contact with a solid-phase adsorbent material (solid-phase adsorbent material particles) with a complexation generation capacity higher than that of the chelating agent. As a result, the harmful metals, etc., captured by the chelating agent are detached from the chelating agent and adsorbed or extracted by the solid-phase adsorbent material. Thus, harmful metals, etc., are removed and recovered from the chelating cleaning solution, and the chelating agent is restored to a state capable of capturing harmful metals, etc., thereby regenerating the chelating cleaning solution. The chelation cleaning solution stored in the regeneration chelation cleaning solution storage tank 43 is pumped back to the bentonite cleaning section 14 via the pipeline 52 through the pump 51.

[0048] The solid-phase adsorbent material of the chelating agent is a solid substance such as a gel, which typically possesses strong binding forces (non-covalent bonds). When it comes into contact with an aqueous solution containing a chelating agent that has captured a metal, the metal ions coordinated with the chelating agent can detach from the chelating agent and move to the solid-phase adsorbent material. Examples of such solid-phase adsorbent materials include materials in which cyclic molecules are densely loaded onto a support such as silica gel or resin, and chelating ligands are modified onto these cyclic molecules. When using such solid-phase adsorbent materials, various bonds and interactions, such as coordination bonds and hydrogen bonds, are formed between adjacent cyclic molecules and chelating ligands, resulting in multi-point interactions and a stronger chemical bond to metal ions than that of the chelating agent. Furthermore, due to the characteristics of the cyclic molecules, metal ions can be selectively captured. With the regeneration of this chelating cleaning solution, the adsorption capacity of harmful metals in the solid-phase adsorbent material gradually increases over time, but the adsorption capacity of the solid-phase adsorbent material has an upper limit. Therefore, when the adsorption capacity of harmful metals in the solid-phase adsorbent material reaches or is close to saturation, the solid-phase adsorbent material needs to be regenerated. That is, with the chelation cleaning solution removed, acid flows through the interior of the packed tower 41 to remove harmful metals and other substances adsorbed on the solid-phase adsorbent material, thereby regenerating the solid-phase adsorbent material. In this way, harmful metals and other substances are recovered by the acid, and the solid-phase adsorbent material is regenerated, restoring it to a state where it can again adsorb or extract harmful metals and other substances or their ions. It should be noted that after regeneration with acid, the solid-phase adsorbent material is washed with water to remove trace amounts of acid adhering to it.

[0049] When the adsorption capacity of harmful metals in the solid adsorbent material within the packed tower 41 reaches or is near saturation, and acid regeneration is required, valves 63, 62, 65, and 67 on pipelines 54, 48, 49, and 55 are opened, while other valves 61, 64, 66, and 68 are closed, and pump 53 operates. As a result, acid in the acid storage tank 44 flows through the interior of the packed tower 41 and returns to the acid storage tank 44. Before the regeneration operation of the solid adsorbent material begins, the chelating cleaning solution within the packed tower 41 is discharged. It should be noted that if multiple packed towers 41 are arranged in parallel, the chelating cleaning solution can be continuously regenerated even if some packed towers 41 stop supplying chelating cleaning solution. Whether the adsorption capacity of harmful metals in the solid adsorbent material has reached or is near saturation can be determined by detecting the content of harmful metals in the chelating cleaning solution discharged from the packed tower 41.

[0050] The time for the acid to flow through the packed tower 41 is appropriately set according to the size or shape of the packed tower 41 and the size of the solid adsorbent particles. The acid circulates between the acid storage tank 44 and the packed tower 41. During this time, the solid adsorbent in the packed tower 41 comes into contact with the acid, and harmful metals and other substances adsorbed on the solid adsorbent are detached by the acid. That is, harmful metals and other substances are recovered by the acid, and at the same time, the solid adsorbent is regenerated, restoring itself to a state where it can adsorb harmful metals and other substances again.

[0051] After the solid-phase adsorbent material is regenerated with acid, during the water washing process, valves 64, 62, 65, and 68, located on pipelines 57, 48, 49, and 58, are opened, while other valves 61, 63, 66, and 67 are closed, and pump 56 is activated. This causes water in the water storage tank 45 to flow through the packed tower 41 and back to the water storage tank 45. Before starting this water washing operation of the solid-phase adsorbent material, the acid in the packed tower 41 is removed. Water circulates between the water storage tank 45 and the packed tower 41. At this time, the solid-phase adsorbent material in the packed tower 41 comes into contact with water, and the acid adhering to the solid-phase adsorbent material is washed away. Afterward, the regeneration of the chelation cleaning solution begins again.

[0052] like Figure 6As shown, the sand rinsing unit 16 (chelating agent removal device) includes a belt conveyor 70, a sand supply device 71, a rinsing water distribution device 72, and a cleaning wastewater receiving tank 73. Here, the belt conveyor 70 includes: a generally cylindrical drive roller 74 coaxially mounted on a shaft 74a driven by an electric motor (not shown); a generally cylindrical driven roller 75 coaxially mounted on a shaft 75a not connected to a drive source; an annular or endless conveyor belt 76 wound around the drive roller 74 and the driven roller 75; a plurality of support rollers 77 supporting or guiding the conveyor belt 76; and a guide plate 78 guiding the sand discharged from the belt conveyor 70. The drive roller 74 and the driven roller 75 have the same diameter and are positioned at the same height. The conveyor belt 76 is formed of a porous, mesh, fibrous, or cloth-like material that allows rinsing water to pass through but does not allow sand particles to pass through, and is flexible into an annular shape. The flushing water distribution device 72 distributes flushing water onto the bentonite conveyed by the conveyor belt 76 within a predetermined length (e.g., 1-2 m) in the direction of movement of the conveyor belt 76. It should be noted that the amount of flushing water distributed from the flushing water distribution device 72 is preferably set to be sufficient to wash away approximately all of the chelating cleaning fluid adhering to the sand. For example, the amount of flushing water distributed is 1.5 to 2.0 times the amount of chelating cleaning fluid adhering to the bentonite. Specifically, for example, when conveying chelating cleaning fluid containing 10% sand at a rate of 5 tons per hour (dry basis), 0.75 to 1.0 tons of flushing water are distributed per hour.

[0053] The bentonite supply device 71, located near the driven roller 75, supplies sand discharged from the bentonite cleaning section 14 to the conveyor belt 76 at a predetermined flow rate. The bentonite supplied in this way is conveyed by the conveyor belt 76 and falls downwards via the guide plate 78 at the position corresponding to the drive roller 74, being stored in a bentonite storage area (not shown). Rinse water is distributed onto the bentonite conveyed by the conveyor belt 76 by the rinse water distribution device 72. This rinse water moves downwards through the gaps between the bentonite particles, flowing down the conveyor belt 76 as cleaning wastewater or falling into the cleaning wastewater receiving tank 73. At this time, the chelating cleaning liquid adhering to the bentonite is washed downwards by the rinse water, flowing into or falling into the cleaning wastewater receiving tank 73.

[0054] Thus, sand without chelating agents is stored in the bentonite storage area (not shown). On the other hand, the cleaning wastewater containing chelating agents in the cleaning wastewater receiving tank 73 of the bentonite rinsing section 16 is introduced into the cleaning wastewater evaporation device 81 of the chelating agent recovery section 17 (see...). Figure 7 Then, the chelating agent is recovered from the cleaning wastewater by means of the cleaning wastewater evaporation device 81, and the chelating agent is sent back to the bentonite cleaning section 14 along with the sand.

[0055] Furthermore, to further reduce the amount of rinsing water used in the bentonite rinsing section 16, i.e., the amount of cleaning wastewater discharged, a vacuum suction belt conveyor can also be used as the belt conveyor 70. It should be noted that the vacuum suction belt conveyor is a device that, while conveying sand using a filter media mounting belt, simultaneously uses the filter media mounting belt to vacuum-suction the bentonite to reduce its moisture content. At this time, because the air flowing at high speed into the decompression chamber through the gaps between the bentonite particles promotes the downward movement of the rinsing water or cleaning wastewater, the amount of rinsing water used can be significantly reduced.

[0056] The following describes in detail the structure and function of the cleaning wastewater evaporation device 81 in the chelating agent recovery unit 17.

[0057] like Figures 7-9 As shown, in the cleaning wastewater evaporation device 81 of the chelating agent recovery section 17, a cleaning wastewater storage tank 84 is provided, which receives the cleaning wastewater receiving tank 73 from the bentonite rinsing section 16 via the cleaning wastewater passage 83 (see...). Figure 6 The wastewater discharged contains chelating agents. The wastewater storage tank 84 is a rectangular concrete tank buried in the ground. A roof (not shown) is provided above the wastewater storage tank 84 to prevent rainwater from falling onto it. It should be noted that, for the sake of clarity in showing the positional relationship of the facilities or devices in the chelating agent recovery unit 17 or the wastewater evaporation device 81, [the following is omitted as it is not part of the main text]. Figure 7 In the middle, the wastewater storage tank 84 and the wastewater passage 83 are arranged in parallel directions ( Figure 7 In terms of the positional relationship (left and right direction), the side where the cleaning wastewater storage tank 84 is located is called "left", and the side where the cleaning wastewater passage 83 is located is called "right".

[0058] Furthermore, in the cleaning wastewater evaporation device 81, container-shaped bentonite receiving portions 85 for holding water evaporation sand are arranged at appropriate intervals in a direction perpendicular to the cleaning wastewater storage tank 84 (front-back direction). In this embodiment, fine sand (sand with a particle size of 0.075 to 0.25 mm) is used as this water evaporation sand. It should be noted that, for the sake of concisely showing the positional relationship of the facilities or devices in the chelating agent recovery unit 17 or the cleaning wastewater evaporation device 81, in terms of the direction in which the cleaning wastewater storage tank 84 and the bentonite receiving portions 85 are side by side (a direction perpendicular to the left-right direction), the side where the cleaning wastewater storage tank 84 is located is referred to as "front," and the side where the bentonite receiving portions 85 are located is referred to as "rear."

[0059] The bentonite container 85 has a front wall 86, a rear wall 87, a left wall 88, a right wall 89, and a bottom wall 90. It is a rectangular planar shape with a relatively short length in the left-right direction and a relatively long length in the front-back direction. It has a depth capable of accommodating an appropriate amount of sand for water evaporation and is a concrete box-shaped container installed on the ground or buried underground. Furthermore, the cleaning wastewater evaporation device 81 also includes: a roof 92 disposed above the bentonite container 85 to prevent rainwater from falling onto the bentonite container 85; a cleaning wastewater distribution device 93 that distributes the cleaning wastewater containing chelating agents stored in the cleaning wastewater storage tank 84 onto the sand for water evaporation contained in the bentonite container 85; and a cleaning wastewater return mechanism 94 that returns the cleaning wastewater at the bottom of the bentonite container 85 to the cleaning wastewater storage tank 84.

[0060] The bentonite-containing section 85 is made of concrete, with its upper portion exposed to the atmosphere and buried in the ground at 100. It has a rectangular shape with a relatively short lateral length (e.g., 20–50 m) and a relatively long front-to-back length (e.g., 100–200 m), and its depth is set to accommodate a suitable amount of sand for water evaporation (e.g., 0.4–0.8 m). It is a box-shaped (shallow pool-shaped) container with an integrally formed front wall 86, rear wall 87, left side wall 88, right side wall 89, and bottom wall 90. It should be noted that the lateral and front-to-back lengths of the bentonite-containing section 85 are appropriately set according to the amount of cleaning wastewater to be evaporated by the sand-containing section 85.

[0061] On the upper surface of the bottom wall 90, a plurality of drainage ditches 101 are provided, which are spaced apart from each other at predetermined intervals, extend parallel to each other in the front-back direction, and have a predetermined depth (e.g., 5-10 cm). These drainage ditches 101 are connected to a water collection drainage ditch 102 located near the front end of the bentonite receiving portion 85. The front end of the water collection drainage ditch 102 is connected to the cleaning wastewater storage tank 84. It should be noted that the drainage ditches 101 and the water collection drainage ditch 102 are constituent elements of the cleaning wastewater return mechanism 94. The cleaning wastewater (i.e., the excess cleaning wastewater that has not evaporated) that flows down the gaps in the sand for water evaporation and into each drainage ditch 101 flows back to the cleaning wastewater storage tank 84 by gravity via the water collection drainage ditch 102. Furthermore, perforated plates 104 are provided on a plurality of protrusions 103 located between these drainage ditches 101 in the left-right direction, allowing the cleaning wastewater to pass through but not the sand for water evaporation. Here, the perforated plate 104 is not a single plate-shaped component, but is composed of many perforated plates of convenient size for manufacturing and handling (e.g., perforated plates with a width of 1 to 2 m, a front-to-back width of 2 to 5 m, and a thickness of 5 to 10 mm). Then, a sand layer 105 of a predetermined thickness (e.g., 30 to 60 cm) is formed on the perforated plate 104.

[0062] On the left side wall 88 of the bentonite receiving portion 85, a plurality of left vertical frames 107 are arranged at appropriate intervals (e.g., 5-10 m) along the front-back direction. Simultaneously, on the right side wall 89, a plurality of right vertical frames 108 are arranged at appropriate intervals (e.g., 5-10 m) along the front-back direction. It should be noted that the left vertical frames 107 and right vertical frames 108 are arranged at the same position in the front-back direction. Furthermore, the upper portions of the left vertical frames 107 and right vertical frames 108, which are arranged at the same position in the front-back direction, are connected by horizontal frames 109 extending horizontally in the left-right direction. Additionally, the upper portions of adjacent left vertical frames 107 are connected to each other by longitudinal frames (not shown) extending in the front-back direction, and the upper portions of adjacent right vertical frames 108 are connected to each other by longitudinal frames (not shown) extending in the front-back direction.

[0063] Thus, a roof 92 is installed on a fence-like frame structure consisting of a left vertical frame 107, a right vertical frame 108, a horizontal frame 109, and a longitudinal frame (not shown). The roof 92 has a planar shape slightly larger than the bentonite containment portion 85 to prevent rainwater from falling into the bentonite containment portion 85 during ordinary rainfall. It should be noted that, although not shown, rainwater falling on the roof 92 is discharged outside the bentonite containment portion 85 through rainwater drainage devices such as gutters, and will not flow into the cleaning wastewater storage tank 84.

[0064] The wastewater distribution device 93 is positioned above the bentonite containment section 85 and below the roof 92, and includes multiple water supply pipes 111 extending in the front-to-back direction. Although not shown in detail, each water supply pipe 111 is supported by a horizontal frame 109 using fasteners. These water supply pipes 111 are arranged in parallel at appropriate intervals in the left-to-right direction (e.g., 1-2 m). Furthermore, on each water supply pipe 111, multiple downward-opening water nozzles 112 are installed at appropriate intervals in the front-to-back direction (e.g., 1-2 m).

[0065] The front ends of each water supply pipe 111 extending in the front-to-back direction are connected to the rear end of the cleaning wastewater supply pipe 114 via an intermediate pipe 113 extending in the left-to-right direction. It should be noted that the rear end of each water supply pipe 111 is closed. The front end of the cleaning wastewater supply pipe 114 is immersed in the cleaning wastewater in the cleaning wastewater storage tank 84. Furthermore, a cleaning wastewater supply pump 115 is installed on the cleaning wastewater supply pipe 114 near the cleaning wastewater storage tank 84. Here, the cleaning wastewater supply pump 115 draws in and pressurizes the cleaning wastewater in the cleaning wastewater storage tank 84 through the cleaning wastewater supply pipe 114 (the portion of the cleaning wastewater supply pump 115 near the cleaning wastewater storage tank) and supplies it to each water supply pipe 111 via the cleaning wastewater supply pipe 114 (the portion of the cleaning wastewater supply pump 115 near the sand receiving portion) and the intermediate pipe 113. In this way, cleaning wastewater can be released from the upper surface of the sand layer 105 (sand for water evaporation) within the bentonite containment portion 85 of each water discharge nozzle 112.

[0066] The following describes a method for treating cleaning wastewater containing chelating agents to recover the chelating agents using the chelating agent recovery unit 17 or the cleaning wastewater evaporation unit 81. From the cleaning wastewater receiving tank 73 (see...) Figure 6 The cleaning wastewater containing chelating agents discharged, except for the water that evaporates (vaporizes) into the atmosphere naturally, flows into the cleaning wastewater storage tank 84 through the cleaning wastewater passage 83 and is stored there.

[0067] The cleaning wastewater stored in the cleaning wastewater storage tank 84 is supplied by the cleaning wastewater supply pump 115 through the cleaning wastewater supply pipe 114 and the intermediate pipe 113 to each water delivery pipe 111. The wastewater is then released from each discharge nozzle 112 in a generally downward manner as droplets or mist onto the upper surface of the sand layer 105 in the bentonite containing portion 85, and is evenly distributed on the sand layer 105. In this way, the cleaning wastewater is distributed onto the sand layer 105 in the bentonite containing portion 85 through the discharge nozzles 112, and the sand particles in the sand layer 105 are always kept with cleaning wastewater, or the sand particles are maintained in a saturated moisture state covered by a film of cleaning wastewater (e.g., moisture content of 30-35%).

[0068] Then, the cleaning wastewater retained in the sand layer 105 evaporates (vaporizes) into the atmosphere. In this way, all the cleaning wastewater flowing into the cleaning wastewater storage tank 84 evaporates (vaporizes) from the sand layer 105 into the atmosphere. At this time, the chelating agent contained in the cleaning wastewater remains within the sand layer 105. Therefore, the chelating agent contained in the cleaning wastewater is not discharged to the outside but is reliably recovered. It should be noted that the area or size of the bentonite containment portion 85 required for the cleaning wastewater to evaporate from the sand layer 105 will be described later.

[0069] The amount of cleaning wastewater distributed from the cleaning wastewater distribution device 93 (discharge nozzle 112) to the sand layer 105 is preferably set to be greater than the amount of cleaning wastewater evaporating from the sand layer 105 (e.g., 1.2 to 2.0 times the expected evaporation amount). As a result, the sand constituting the sand layer 105 is maintained at a saturated moisture state (e.g., a moisture content of 30 to 35%). Here, excess cleaning wastewater flows down into the gaps between the sand particles within the sand layer 105, through the perforated plate 104, and into the drainage ditch 101. Then, excess cleaning wastewater in the drainage ditch 101 flows back to the cleaning wastewater storage tank 84 via the collection drainage ditch 102.

[0070] This process of evaporating the cleaning wastewater is repeated, and the chelating agent gradually accumulates in the sand layer 105 within the bentonite container 85. Therefore, after a predetermined period (e.g., every 2 to 6 months), the sand used for water evaporation in a predetermined area or zone (e.g., an area of ​​100 to 200 m²) within the sand container 85 is removed and introduced into the bentonite washing section 14 to recover the chelating agent. Then, in the area or zone within the bentonite container 85 where the sand used for water evaporation has been removed, fine sand screened from the sand discharged from the bentonite rinsing section 16 is introduced as sand for water evaporation. That is, the sand containing the chelating agent for water evaporation in the predetermined area or zone within the bentonite container 85 is exchanged with fine sand screened from sand without the chelating agent. Therefore, the loss of the chelating agent from the bentonite purification and mixing production unit S to the outside can be prevented or reduced. In addition, since a portion of the sand produced by the bentonite washing section 16 without chelating agent is used as sand for water evaporation contained in the bentonite containing section 85, the sand for water evaporation used in the bentonite containing section 85 can be easily obtained.

[0071] The following describes the specifications (surface area, dimensions, etc.) of the cleaning wastewater storage tank 84 and the bentonite container 85 required for the evaporation of cleaning wastewater from the sand layer 105. It is assumed that the bentonite purification and mixing production unit S purifies 100 tons of contaminated bentonite (containing water) per hour. This contaminated bentonite comprises 25 tons of gravel (dry basis), 30 tons of sand (dry basis), 25 tons of soil (dry basis), and 20 tons of water (25% water content). Furthermore, when the bentonite purification and mixing production unit S operates for 8 hours per day and 250 days per year, the specifications of the cleaning wastewater storage tank 84 and the bentonite container 85 can be set, for example, as follows. It should be noted that the specifications described here are merely examples. Even if the bentonite processing capacity, operating time, or number of operating days of the bentonite treatment system S differs, the specifications or dimensions of the cleaning wastewater storage tank 84 and the bentonite container 85 can be set using the same method.

[0072] The specifications for the cleaning wastewater storage tank 84 are set as follows:

[0073] • Rectangular storage tank (left and right dimensions: 10m, front and back dimensions: 25m, depth: 3m); • Surface area 250 m²; • Maximum water storage capacity is approximately 700 tons; The sand container has a specification of 85.

[0074] The specifications for the bentonite containment portion (85) are set as follows:

[0075] • Rectangular shape (left and right dimensions: 40m, front and back dimensions: 100m, depth: 0.8m); • Upper surface area: 4000 m²; • Sand holding capacity is approximately 2000 m³; Wastewater discharge from the bentonite rinsing section 16 Assuming that the chelated cleaning liquid content of the sand discharged from the belt filter press 14C of the bentonite cleaning section 14 is 10%, and the amount of rinsing water used in the bentonite rinsing section 16 is set to be 2.0 times the amount of chelated cleaning liquid contained in or attached to the bentonite, then the amount of cleaning wastewater containing chelating agent discharged from the bentonite rinsing section 16 is 12,000 tons per year.

[0076] 30 tons / hour × 0.1 × 8 hours × 250 days × 2.0 = 12,000 tons / year Evaporation rate of water from cleaning wastewater storage tank 84 It is generally known that the evaporation rate of water from lakes, ponds, and other bodies of water is approximately 0.5 to 1.0 tons per square meter per year. Therefore, it is estimated that at least 125 tons of water evaporate annually from the wastewater storage tank 84 (surface area 250 m²).

[0077] As mentioned earlier, the maximum storage capacity of the cleaning wastewater storage tank 84 is approximately 700 tons, which is equivalent to about 15 days of the cleaning wastewater discharge from the bentonite rinsing section 16 (12,000 tons / year, or 48 tons / day based on 250-day operation). On the other hand, since the cleaning wastewater stored in the cleaning wastewater storage tank 84 is treated daily in the bentonite containment section 85, the cleaning wastewater storage tank 84 can store sufficient cleaning wastewater without overflowing.

[0078] Water evaporation rate of sand layer 105 For example, the estimated water evaporation rate of the sand layer 105 within the 85-component bentonite containment portion is 3.15 tons / m²·year, as described below. That is, Non-Patent Document 1 discloses that, at a temperature of 14.2℃, a relative humidity of 59%, and an air velocity of 250 cm / s, the water evaporation rate of bentonite with a water content of 32.1% (saturated moisture state) is 11.3 × 10⁻⁻⁻⁻⁶. 6g / cm²·second. Furthermore, it was disclosed that the water evaporation rate of bentonite with a water content of 32.9% (saturated moisture state) was 7.9 × 10⁻⁻⁻⁻⁶ at a temperature of 14.8℃, a relative humidity of 57%, and an air velocity of 170 cm / second. 6 g / cm²·second.

[0079] In summary, according to the related bentonite purification and stirring production apparatus of the present invention, since chelating agents are not added to the large amount of cleaning water circulating in the series of flow systems within the bentonite purification and stirring production apparatus S, but instead the sand discharged from the hydrocyclone 7 is cleaned with a chelating cleaning solution, the amount of chelating agent that needs to be retained within the bentonite purification and stirring production apparatus S can be significantly reduced. Furthermore, since the sand cleaned with the chelating cleaning solution is washed with rinsing water in the bentonite rinsing section 16, bentonite free of chelating agents and suitable for reuse can be obtained. In addition, since the chelating agent in the cleaning wastewater discharged from the bentonite rinsing section 16 is recovered by the chelating agent recovery section 17 and returned to the bentonite cleaning section 14, the amount of chelating agent used can be significantly reduced.

[0080] Furthermore, since the supply of pressurized air in the belt filter press 14C reduces the chelation cleaning liquid content of the sand wetted by the chelation cleaning liquid, the amount of rinsing water used in the bentonite rinsing section 16, i.e. the amount of cleaning wastewater that needs to be evaporated, can be reduced, thereby reducing the floor space occupied by the bentonite containing section 85.

Claims

1. A bentonite purification and stirring production apparatus for purifying bentonite containing gravel, sand, and soil and contaminated with harmful metals or their compounds, characterized in that, It has a bentonite grading section and a bentonite purification section, wherein: The bentonite grading section includes a mixing device, a drum screen, a hydrocyclone, a thickener, and a filter press connected in sequence. The mixing device is used to mix bentonite with washing water. The drum screen is used to separate gravel. The hydrocyclone is used to separate sand. The thickener is used to separate the supernatant from the sludge containing mud by sedimentation. The filter press is used to filter the sludge and separate the mud. The bentonite purification unit includes a bentonite washing unit, a chelating agent regeneration unit, a bentonite rinsing unit, and a chelating agent recovery unit. The bentonite washing unit is used to wash sand to remove harmful metals or their compounds. The chelating agent regeneration unit is used to regenerate the chelating agent and circulate it to the bentonite washing unit. The bentonite rinsing unit is used to remove residual chelating agent from the sand. The chelating agent recovery unit is used to recover the chelating agent from the washing wastewater. The chelating agent recovery unit includes a cleaning wastewater storage tank, a sand storage unit, a cleaning wastewater distribution device, and a cleaning wastewater return mechanism. The sand storage unit is a container-shaped structure with an opening at the top and a shielding structure at the top. The cleaning wastewater distribution device is used to spray cleaning wastewater into the sand storage unit. The cleaning wastewater return mechanism is used to return excess cleaning wastewater to the cleaning wastewater storage tank. The device is also equipped with a circulation mechanism for transferring the sand used for water evaporation that adsorbs chelating agents in the sand storage section to the bentonite washing section, and for replenishing a portion of the sand discharged from the bentonite washing section into the sand storage section as new sand for water evaporation.

2. The bentonite purification and mixing production device according to claim 1, characterized in that, The bentonite cleaning section includes a flow-through mixer, a vibrating screen, and a belt filter press. The flow-through mixer is used to mix sand with chelating cleaning solution and capture harmful metals or their compounds. The vibrating screen is used to separate the chelating cleaning solution. The belt filter press is used to reduce the chelating cleaning solution content in the sand.

3. The bentonite purification and mixing production device according to claim 2, characterized in that, The belt filter press includes an upper belt mechanism and a lower belt mechanism arranged opposite to each other. Both belt mechanisms are equipped with a porous endless belt wound on multiple rollers. The upper belt mechanism is equipped with a pressurized air supply device, and the pressurized air can flow downward through the upper endless belt, the sand layer and the lower endless belt in sequence.

4. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The chelating agent regeneration section is equipped with a chelating cleaning solution regeneration device. The regeneration device includes a solid-phase adsorption material. The complexation generation capacity of the solid-phase adsorption material is higher than that of the chelating agent, and it can adsorb harmful metals or their compounds in the chelating cleaning solution.

5. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The bentonite washing section is equipped with a chelating agent removal device, which removes the chelating agent on the sand discharged from the bentonite washing section by spraying or jetting washing water.

6. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The wastewater return mechanism includes a drainage ditch and a water collection ditch installed on the bottom wall of the sand storage section. The drainage ditch extends along the length of the sand storage section, and the water collection ditch connects the drainage ditch to the wastewater storage tank. Excess wastewater is returned to the wastewater storage tank through the drainage ditch and the water collection ditch.

7. The bentonite purification and mixing production apparatus according to claim 6, characterized in that, The bottom wall of the sand storage section is provided with multiple protrusions, which are located between adjacent drainage ditches. A perforated plate is laid on the protrusions, and a sand layer is formed on the perforated plate.

8. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The cleaning wastewater distribution device includes multiple water supply pipes arranged along the length of the sand storage section. Multiple water discharge nozzles are installed at intervals on the water supply pipes. The water supply pipes are connected to the cleaning wastewater storage tank through an intermediate pipe and a cleaning wastewater supply pipe. A cleaning wastewater supply pump is provided on the cleaning wastewater supply pipe.

9. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The flow-through mixer includes a main body, a baffle, a mixer, and a motor. The baffle is installed on the inner circumference of the main body and is in the shape of an inwardly downward inclined cone. The mixing blades of the mixer and the baffle are arranged alternately in the vertical direction. The mixing blades can pass through the hole in the center of the baffle.

10. The bentonite purification and mixing production apparatus according to claim 1, characterized in that, The chelating agent regeneration section also includes an intermediate storage tank, a regenerated chelating cleaning solution storage tank, an acid solution storage tank, and a water storage tank. Each storage tank is connected to the packed tower via a pipeline with a valve, which can realize the switching between chelating cleaning solution regeneration, solid phase adsorbent acid solution regeneration, and water washing.

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