JP2007117845A - Reaction tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reaction tank which can effectively agitate heavy metals-containing water loaded with a reducing substance by requiring no mechanical means, such as an agitator inserted into the reaction tank, and, thereby, can easily make the structure of the inside of the reaction tank airtight to prevent the oxidation of the reducing substance by air. <P>SOLUTION: The reaction tank comprises a reaction tank main body 70 where the inside is airtightly closed, one of the upper part and lower part is connected with a heavy metals-containing water feed pipe 71, and the other part is connected with a heavy metals-containing water discharge pipe 72, and a first baffle plate 73 installed vertically on the inner wall of the reaction tank main body 70, and protruded from the inner wall to inside. The feed pipe 71 is connected with the reaction tank main body 70 so that rotating flow of the heavy metals-containing water is generated in the reaction tank main body from the above one part to the other part by introducing the heavy metals-containing water in the direction along the inner wall of the reaction tank main body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reaction vessel suitable for use in a heavy metal-containing water treatment plant for removing heavy metals from waste water containing heavy metals with a reducing substance such as a reducing iron compound.

  In general, waste water discharged from factories and the like contains heavy metals that are various pollutants such as lead, zinc, nickel, and selenium. For this reason, when processing the said waste_water | drain etc., after removing these heavy metals until it becomes below each discharge | emission standard based on the water pollution prevention method, it is necessary to flow to a sewer, a river, etc. In particular, for the selenium, which has been considered difficult to remove, the effluent standard is strictly regulated to 0.1 mg / liter.

  Therefore, for example, in the following Patent Document 1, a solid reaction separation of a effluent from a primary reaction tank provided with an introduction pipe for a heavy metal drainage containing selenium, an alkali agent introduction pipe and a stirrer, and the primary reaction tank. A secondary reaction tank comprising a tank, a separated liquid introduction pipe, a ferrous salt introduction pipe, an alkaline agent introduction pipe, and an inert gas and air blowing pipe provided with a switching valve; and the secondary reaction An apparatus for treating heavy metal wastewater containing selenium having a solid-liquid separation tank for effluent from the tank has been proposed.

  In the heavy metal wastewater treatment apparatus, it is possible to remove the hydroxide as a hydroxide by first adding an alkali neutralizer to adjust the pH to 8 to 10.5 in the primary reaction tank for heavy metal wastewater containing selenium. Heavy metals are precipitated. Next, the effluent from this primary reaction tank is solid-liquid separated in a solid-liquid separation tank, sent to the secondary reaction tank and heated to 65 ° C. or higher, and further, inert gas is blown to remove dissolved oxygen. Add ferrous sulfate and so on to dissolve ferrous ions, add sodium hydroxide and so on to neutralize the waste water to pH 8.5 to 11, and stir the inside to proceed the selenium reduction reaction By oxidizing, ferrous hydroxide is oxidized and iron oxide is deposited.

  Next, by stopping the blowing of the inert gas into the secondary reaction tank and switching to the blowing of air, the removal of heavy metal is started and ferrite particles are generated. Thereafter, the precipitate from which the effluent from the secondary reaction tank is obtained is sent to a solid-liquid separation tank, and is subjected to solid-liquid separation by filtration or a magnet all at once.

According to such a treatment apparatus, it is said that the wastewater standards can be sufficiently satisfied with respect to the residual concentration of heavy metals including selenium by passing the treated water through the first to third steps. .
JP 2002-326090 A

  By the way, in the conventional heavy metal wastewater treatment apparatus, in the secondary reaction tank, oxygen in the wastewater reacts with the ferrous ions in order to ensure the reduction reaction of selenium by ferrous ions. It is necessary to prevent this. For this reason, it is necessary to provide an inert gas blowing device or the like for removing dissolved oxygen in the waste water, and there is a problem that the device and its control are further complicated and the equipment cost is increased.

  In order to promote these reactions when injecting inert gas to precipitate iron oxide by reduction of selenium, or when stopping inactive gas blowing and switching to air blowing to generate ferrite particles Need to be stirred.

  Conventionally, this kind of stirring is generally performed by a stirrer having a rotating shaft inserted into a reaction vessel and driven to rotate by a motor or the like, and a stirring blade fixed to the rotating shaft. There is a risk that air may enter from the insertion portion of the rotating shaft in the tank. For this reason, it is necessary to supply an excessive inert gas into the reaction tank or to provide an expensive mechanical seal having airtightness in the insertion portion, and there is a problem that the cost is inferior.

  The present invention has been made in view of such circumstances, and does not require mechanical means such as a stirrer inserted into a reaction vessel, and effectively contains heavy metal-containing water to which an internal reducing substance is added. It is an object of the present invention to provide a reaction tank in which the inside of the reaction tank can be easily airtight and the oxidation of the reducing substance by air can be prevented.

  In order to solve the above-mentioned problem, the invention described in claim 1 is to reduce heavy metals by the reducing substance while stirring the heavy metal-containing water to which the reducing substance is added while the air inflow is blocked. The inside of the reaction vessel is hermetically sealed, the supply pipe for the heavy metal containing water is connected to one of the upper part and the lower part, and the discharge pipe for the heavy metal containing water is connected to the other And a first baffle plate provided in the vertical direction on the inner wall of the reaction tank main body and projecting inward from the inner wall, and the supply pipe is By introducing the heavy metal-containing water into the reaction tank main body in a direction along the inner wall of the reaction tank main body, a swirling flow of the heavy metal-containing water is generated from the one side to the other in the reaction tank main body. Connected so that It is characterized in.

  The invention according to claim 2 is the invention according to claim 1, wherein the supply pipe is connected to a lower part of the reaction tank body, and the discharge pipe is connected to an upper part of the reaction tank body. It is characterized by being connected.

  According to a third aspect of the present invention, a gap serving as a flow path for the heavy metal-containing water is formed between the first baffle plate according to the first or second aspect and the inner wall of the reaction vessel main body. It is characterized by being.

  Furthermore, the invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein at least one of an upper part and a lower part in the reaction vessel main body extends in a horizontal direction and the swirl flow. A second baffle plate is provided opposite to.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein a return pipe piped between the upper and lower parts of the reaction vessel main body and a circulation interposed in the return pipe. A circulation line for returning the heavy metal-containing water extracted from the other of the upper or lower part of the reaction vessel body to the one side, and the circulation line is connected to the return pipe. A pH meter that measures the pH of the heavy metal-containing water flowing through the return pipe and a pH adjusting unit that supplies the aqueous alkaline solution in the storage tank to the supply line based on a detection signal from the pH meter. It is characterized by being provided.

In the invention according to any one of claims 1 to 5, the heavy metals are, for example, various heavy metal elements such as selenium, cadmium, hexavalent chromium, lead, zinc, copper, nickel, arsenic, antimony, and metals. Includes elements.
The above-mentioned heavy metal-containing water is a general term for water containing the above heavy metals, and includes various types of wastewater and wastewater generated naturally and artificially. For example, industrial wastewater, sewage, seawater, river water , Water in swamps and lakes, pool water on the surface, water in dams such as rivers, underground water, pool water, culvert water, etc., which contain the above heavy metals.

  In the reaction tank in any one of Claims 1-5, if the heavy metal containing water is supplied in the reaction tank main body by which the inside was airtightly sealed from the supply pipe, the said heavy metal containing water will be the reaction tank main body. By being introduced in the direction along the inner wall, the flow flows as a swirling flow from the supply pipe side toward the discharge pipe side. When this swirling flow flows from the supply pipe side to the discharge pipe side, it collides with the first baffle plate protruding from the inner wall of the reaction vessel main body, thereby forming a horizontal vortex flow and stirring. Is done.

  Thereby, the contact between the heavy metal-containing water and the reducing substance added thereto is promoted, and the heavy metal in the heavy metal-containing water is reduced by the reducing substance and extracted from the containing water. As a result, the heavy metals can be removed from the heavy metal-containing water by solid-liquid separation in the subsequent stage of the reaction tank.

  Thus, according to the reaction tank according to any one of claims 1 to 5, since the inside of the reaction tank body has an airtight structure in which air inflow is blocked, the reaction tank body is made of water containing heavy metals. As a result, the reducing substance added to the heavy metal-containing water is not oxidized by the air, and thus a device for supplying an inert gas to the reaction vessel body and a device for heating to a high temperature are provided. Therefore, efficient reduction and removal of heavy metals can be performed.

  At this time, without using the stirring means penetrating the reaction vessel main body such as a conventional stirrer, while turning the heavy metal containing water supplied to the inside by the connection structure of the supply pipe and the first baffle plate, Since the vortex intrusion is formed and stirred, the reaction vessel main body can be hermetically sealed with an extremely simple structure.

  Although it is possible to connect the supply pipe for the heavy metal-containing water to one of the upper part or the lower part of the reaction tank body and connect the discharge pipe to the other of the upper part or the lower part of the reaction tank body, As in the invention described in Item 2, it is preferable that the supply pipe is connected to the vicinity of the bottom of the reaction tank main body, and the discharge pipe is connected to the vicinity of the ceiling of the reaction tank main body. With such a connection structure, even when a precipitate is generated in heavy metal-containing water due to reduction of heavy metals by a reducing substance, the precipitate is entrained in the heavy metal-containing water supplied from the bottom. Thus, the deposit can be extracted from the discharge pipe to the outside, so that the sediment can be prevented from being deposited on the bottom of the reaction vessel main body. Further, since the precipitate tends to settle in the reaction tank body due to gravity, it takes a lot of time and opportunity for the precipitate and the heavy metal-containing water supplied from the bottom of the reaction tank body to contact and react. And more effective processing can be performed.

  Further, in the invention according to claim 3, since a gap serving as a flow path for the heavy metal-containing water is formed between the first baffle plate and the inner wall of the reaction tank body, the supply pipe side To prevent the formation of a swirling flow toward the discharge pipe from the side and the formation of a dead area in which the flow is prevented at the corner of the joint between the first baffle plate and the inner wall Can do.

  Furthermore, as in the invention described in claim 4, a second baffle plate that extends in the horizontal direction and faces the swirling flow of the heavy metal-containing water on at least one of the upper part and the lower part in the reaction vessel main body. If it is provided, the stirring efficiency can be further increased.

  Moreover, when reducing and removing heavy metals from heavy metal-containing water using the reaction tank according to the present invention, depending on the reducing substance used, the inside of the reaction tank body needs to be maintained within a certain range of alkalinity. . For this reason, it is necessary to measure the pH value of the heavy metal-containing water to which the reducing substance is added and supply an aqueous alkali solution separately so that the pH value is maintained within the above range. In such a case, in the reaction vessel main body, the mixing is still in a non-uniform state due to the agitation described above, so that an error is likely to occur in the pH value detected by the installation location of the pH meter.

  In this regard, according to the invention described in claim 5, a circulation line is provided for returning the heavy metal-containing water extracted from the discharge side of the reaction tank body to the supply pipe side, and the pH is measured in the return pipe of the circulation line. Since the pH meter is provided and the alkaline aqueous solution in the storage tank is supplied to the supply line based on the detection signal from the pH meter, the above-described pH value holding control can be reliably performed. it can.

FIGS. 1-7 shows the best embodiment at the time of applying the reaction tank concerning this invention to the processing plant of heavy metal containing water.
First, the configuration of the processing plant will be described with reference to FIGS. 6 and 7. The processing plant is a reaction unit 1, a solid-liquid separation unit 2 and a filtration unit 3 that are unitized and can be individually transported. The dehydration unit 4 is schematically configured. And this processing plant comprises the said processing units as a whole by connecting each piping part after the said each units 1-4 are conveyed to processing places, such as waste water containing heavy metals, for example. It has come to be.

  The reaction unit 1 includes a storage tank 7 that temporarily stores the waste water and the like discharged from the tank 5 that stores the waste water and the like in the processing place, and ferrous sulfate (reducing substance) in the waste water and the like. And 4 reactors 10a to 10d for reacting the waste water or the like and ferrous sulfate with stirring in the interior where the inflow of air is blocked to produce a reducing iron compound precipitate. Is provided.

  Here, the storage tank 7 is connected to a supply pipe 7a such as drainage at the top, and a flow meter 12 is interposed in the supply pipe 7a. On the other hand, a transfer pipe 7b is connected to the bottom of the storage tank 7 to supply the internal drainage and the like to the vicinity of the bottom of the reaction tank 10a. The transfer pipe 7b is connected to a transfer pump 13 and a flow meter 14. Is intervening. Further, the storage tank 7 is provided with a level detector 15 that detects the liquid level inside and controls the operation of the water pump 6 and the transfer pump 13.

  The addition device 8 includes a tank 16 for storing ferrous sulfate, a liquid feed pump 17 for supplying ferrous sulfate in the tank 16 at a predetermined flow rate, and a discharge pipe 18 of the liquid feed pump 17. In this configuration, the discharge pipe 18 is connected to the downstream side of the flow meter 14 of the transfer pipe 7b. And reaction tank 10b-10d is arrange | positioned sequentially in the back | latter stage of the reaction tank 10a to which the said waste_water | drain etc. to which ferrous sulfate was added are sent from this transfer pipe 7b.

  That is, the four reaction tanks 10a to 10d are provided in series by transfer pipes 20a to 20c, respectively, and the inlet side of each of the transfer pipes 20a to 20c is connected to the upper part of each of the reaction tanks 10a to 10c located in the previous stage. At the same time, the outlet side is connected to the vicinity of the bottom of each of the reaction vessels 10b to 10d located in the subsequent stage. The other end of the transfer pipe 20d connected to the upper part of the final reaction tank 10d is connected to the solid-liquid separation unit 2.

  The solid-liquid separation unit 2 is provided with a thickener 22. The thickener 22 is a well-known device that separates solid-liquid slurry containing iron compound precipitate discharged from the reaction vessel 10d by specific gravity, and has a motor 23a at its center and a shaft 23b that is rotationally driven by the motor 23a. A scraper including a radiating arm-shaped rake 23c connected to the lower end of the shaft 23b and facing the bottom of the thickener 22 is provided. A cylindrical feed well 22a is provided above the thickener 22 so as to surround the shaft 23b, and the supply side end of the transfer pipe 20d is introduced into the feed well 22a.

  Further, a return line 24 and a discharge line 25 which are bifurcated pipes are connected to a solid content outlet 22b provided at the bottom of the thickener 22, and the return line 24 is provided in the reaction unit 1. The mud return pump 26 is connected to the suction side. One end of the return line 27 is connected to the discharge side of the mud return pump 26, and the other end of the return line 27 is connected to the transfer pipe 7b to the first-stage reaction tank 10a. Here, the return line 27 is provided with a flow meter 28 and a condition tank 29, and a water supply line 30 for supplying water into the return line 27 on the upstream side of the flow meter 28 via an on-off valve 30a. It is a branch pipe.

  On the other hand, the discharge line 25 connected to the bottom discharge port 22b of the thickener 22 is sludged from the mud feed line 36 in which the on-off valve 36a and the flow meter 36b are interposed by the mud feed pump 35 provided in the filtration unit 3. It is sent to the storage tank 37. A discharge pipe 38 of the mud storage tank 37 is connected to a suction side of a dehydration pump 39 installed in the dehydration unit 4, and a discharge side of the dehydration pump 39 is connected to a dehydrator 40.

  The mud storage tank 37 includes an agitator 41 for agitating the internal sludge, an ultrasonic level meter 42 for detecting the amount of the sludge and controlling the operation of the mud pump 35 and the opening / closing control of the on-off valve 36a. Is provided. On the other hand, one end portion of the drainage line 43 is connected to the moisture overflow portion 22 c provided on the upper portion of the thickener 22, and the other end portion of the drainage line 43 is installed in the filtration unit 3. The two sand filtration tanks 44 are introduced. Further, the waste water from these sand filtration devices 44 is sequentially sent from a drain line 45 to a water tank 46, a pH adjusting tank 47, and a treated water tank 48, and the treated water is drained from the treated water tank 48.

  Here, the water tank 46 is provided with a level meter 49 for detecting the internal liquid level, and a transfer pump 51 for pumping the internal drainage as service water through the transfer line 50 by a detection signal from the level meter. ing. And the transfer line 50 is the backwashing line 52 which supplies the supplied water as backwashing water of the sand filtration apparatus 44, and the water supply line 30 similarly supplied to the water supply line 30 mentioned above, other washing water, or chemicals A branch pipe is connected to a water supply line 53 for supply as dissolved water.

  The pH adjustment tank 47 includes a pH meter 54 that detects the internal pH value, and a neutralizer tank 55 in order to neutralize the wastewater in the pH adjustment tank 47 based on the detection signal of the pH meter 54. A neutralizing device 57 for adding the sulfuric acid by a pump 56 is provided. In addition, the code | symbol 58 is a stirrer provided in the pH adjustment tank 47 and the treated water tank 48 in the figure.

  Further, the filtration unit 3 is provided with a backwash drain 60 adjacent to the sand filter 44. Then, in this reverse cleaning drainage tank 60, washing water when the sand filtration device 44 is backwashed and dehydration from the dehydrator 40 are introduced through a drainage line 61 and a dehydration line 62, respectively. Further, the reverse cleaning drainage tank 60 has a level meter 63 for detecting the liquid level inside and a drain line or dewatering to the storage tank 7 through a return line 64 based on a detection signal from the level gauge 63. A return transfer pump 65 is provided.

Next, FIGS. 1 to 5 show a first-stage reaction tank 10a incorporated in a processing plant having the above-described configuration.
In these drawings, reference numeral 70 denotes a reaction tank body in the reaction tank 10a, and the upper and lower ends of the cylindrical body 70a are closed by a bottom plate 70b and a top plate 70c. As a result, the inside is hermetically sealed. Annular supply pipe 71 and discharge pipe 72 are provided in the vicinity of the bottom plate 70b and the top board 70c of the reaction vessel main body 70 so as to surround the body portion 70a, and the transfer pipe 7b is connected to the supply pipe 71. And the transfer pipe 20a is connected to the discharge pipe 72.

  Further, the supply pipe 71 is inclined so as to introduce the drainage in the supply pipe 71 in the direction along the inner wall of the reaction tank main body 70 in communication with the supply pipe 71 and the reaction tank main body 70. Branch pipes 71a are provided at four locations at equal intervals in the circumferential direction. Similarly, a branch pipe 72 a that communicates with the supply pipe 71 and the reaction tank main body 70 to guide the drainage in the reaction tank main body 70 to the drain pipe 72 is provided on the inner peripheral side of the discharge pipe 72 in the circumferential direction. Are provided at four locations at equal intervals. These branch pipes 72a are provided so as to incline in the opposite direction to the branch pipe 71a.

  On the other hand, wall surface baffle plates (first baffle plates) 73 are provided at four locations in the circumferential direction on the inner wall of the body portion 70 a of the reaction vessel main body 70. Here, each wall baffle plate 73 is a flat plate member extending from the upper part to the lower part of the body part 70a, and, as shown in FIG. 4, protrudes from the inner wall with its plate surface facing in the circumferential direction. Is arranged. And each wall surface baffle plate 73 is arrange | positioned so that the clearance gap 74 used as flow paths, such as the said waste_water | drain, may be formed between the said inner walls, and a pair of baffle plate support joined to the inner wall in two upper and lower places. 75 is joined.

  In addition, an attachment shaft 76 having one end joined to the top plate 70c and suspended to the vicinity of the bottom plate 70b is provided at the center of the reaction vessel main body 70. As shown in FIG. 2, a wing-type baffle plate (second baffle plate) 77 having a plate surface inclined with respect to the horizontal plane is provided.

  Further, in the reaction tank 10a, one end is connected to the return pipe 78, and the other end is connected to the transfer pipe 7b, and a circulation pump 79 interposed in the return pipe 78, There is provided a circulation line for returning the drainage extracted from the upper part of the reaction tank body 70 to the lower part. The return pipe 78 of the circulation line is provided with a pH meter 80 for measuring the pH of the drainage or the like flowing through the return line 78. Further, as shown in FIG. On the basis of this, there is provided a pH adjusting means for supplying the aqueous alkaline solution in the storage tank 81 to the condition tank 29 by the pump 82 and finally supplying it from the return pipe 78 into the reaction tank body 70 through the transfer pipe 7b. It has been.

  The return pipe 78 is provided with a bypass pipe 83 at a location where a pH meter 80 is interposed. In the figure, reference numeral 84 denotes an air vent pipe provided on the top plate 70c of the reaction tank main body 70.

  The other reaction vessels 10b to 10d have the same configuration as the reaction vessel 10a except that the circulation line and the pH adjusting means are not provided. Transfer pipes 20a to 20c from the previous reaction tanks 10a to 10c are connected to the supply pipes 71, and transfer pipes 20b to 20d to the subsequent reaction tanks 10b to 10d are connected to the discharge pipe 72. ing.

  In the heavy metal-containing water treatment plant having the reaction tanks 10a to 10d having the above-described configuration, each of the units 1 to 4 is transported to the treatment place and connected to each other to assemble the treatment plant. Later, wastewater containing heavy metals stored in the tank 5 of the processing place is sent to the storage tank 7 by the water pump 6. And the said waste_water | drain etc. in this storage tank 7 are supplied to the reaction tank 10a of the first stage from the transfer pipe 7b with the transfer pump 13. FIG. At this time, the ferrous sulfate in the tank 16 is sent from the discharge pipe 18 to the transfer pipe 7b by the reducing iron compound adding device 8 so that a predetermined amount of sulfuric acid corresponding to the supply amount of the drainage or the like is obtained. Add ferrous iron. In parallel with this, a part of the reducing iron compound precipitate separated into solid and liquid in the thickener 22 described later is returned from the return lines 24 and 27 to the reaction vessel 10a.

  Then, the waste water to which the ferrous sulfate is added flows into the annular supply pipe 71 from the transfer pipe 7b, and further enters the reaction tank body 70 at a normal temperature of 10 ° C. to 30 ° C. from the four branch pipes 71a. It is introduced in the direction along the inner wall. As a result, the drainage and the like flow in the reaction vessel body 70 as a swirling flow as indicated by an arrow in the figure from below to above, and at that time, as indicated by a dotted line in FIG. The flow collides with a wall baffle plate 73 protruding from the inner wall of the reaction vessel main body 70, whereby a horizontal vortex flow is formed and stirred. Part of the swirl flow passes through a gap 74 between the wall baffle plate 73 and the inner wall. Further, the swirling flow is stirred in the vertical direction by changing the direction of the upward flow to the downward flow by the airfoil baffle plates 77 provided at the upper and lower portions in the reaction vessel main body 70.

  Then, a part of the drainage or the like flowing out from the upper part of the reaction vessel main body 70 to the discharge pipe 72 is returned again from the return pipe 78 to the supply pipe 71 side by the circulation pump 79. At this time, detection from the pH meter 80 is performed. Based on the signal, the aqueous sodium hydroxide solution supplied from the storage tank 81 by the pump 82 is supplied to the condition tank 29. And in this condition tank 29, it mixes with the iron compound precipitation returned from the return line 27, and is supplied to the reaction tank 10a, The pH value in the reaction tank 10a is 8.5-11, Preferably 9. It is kept in the range of 0-10. Moreover, other parts, such as the said waste_water | drain which flowed out to the discharge pipe 72, are sequentially sent to the subsequent reaction tanks 10b-10d via the transfer pipes 20a-20c.

  Under the above temperature condition and pH value atmosphere, the waste water to which ferrous sulfate is added is stirred in the reaction tanks 10a to 10d in which the air inflow is blocked, thereby causing the oxidation-reduction reaction to occur. A reducing iron compound precipitate consisting of a mixture of last and iron ferrite is formed. And the heavy metal ion contained in the said waste_water | drain etc. is taken in between the layers of the said green last, and becomes the said iron ferrite in the state containing the said heavy metal.

Specifically, the ferrous sulfate added to the waste water or the like is green last (an example of a formula, [Fe (II) ₄ Fe (III) ₂ (OH) ₁₂ ] ²⁺ [SO ₄ nH ₂ O] ^2- ). This green last is a blue-green substance in which a ferrous hydroxide and a ferric hydroxide form a layer, and has a structure in which an anion of a heavy metal is incorporated between layers. The green last is slowly oxidized to become iron ferrite (Fe ₃ O ₄ ), which is a magnetic substance.

For example, hexavalent selenium (SeO ₄ ²⁻ ) contained in the waste water or the like is reduced by ferrous compounds to become tetravalent selenium (SeO ₃ ²⁻ ) and elemental selenium (Se), and It settles in the state taken in between the layers. In this way, the waste water to which ferrous sulfate and the returned reducing iron compound precipitate are added is sequentially sent to the reaction tanks 10a to 10d, and selenium, cadmium, Heavy metals that are contaminants such as hexavalent chromium, lead, zinc, copper, nickel, arsenic, and antimony are effectively removed.

  Next, the waste water from which the heavy metals including the reducing iron compound precipitate are removed is sent to the thickener 22 from the transfer pipe 20d to be subjected to solid-liquid separation, and the slurry containing mainly the iron compound precipitate (solid content). A part is returned to the first-stage reaction tank 10a again from the return lines 24 and 27 as described above.

  On the other hand, the other part of the slurry is stored in the temporary sludge storage tank 37 from the discharge line 25 through the mud feed line 36 by the mud feed pump 35 driven by the detection signal from the ultrasonic level meter 42. Then, the slurry in the sludge storage tank 37 is sent to the dehydrator 40 by the dehydration pump 39, dehydrated, and discharged as the dehydrated cake C. Further, the drainage separated at this time is sent from the drainage line 62 to the backwash drainage tank 60.

  On the other hand, the waste water (moisture) separated by solid-liquid in the thickener 22 is sent from the overflow portion 22c to the sand filtration tank 44 through the drain line 43, and in this sand filtration tank 44, the reducing property remaining in the waste water. After the iron compound precipitate is removed and detoxified, it is sequentially sent from the drainage line 45 to the water tank 46 and the pH adjustment tank 47. In the pH adjusting tank 47, the pH is neutralized by sulfuric acid supplied from the neutralizing device 57 and discharged from the treated water tank 48 to the outside.

  Further, when the differential pressure in the sand filtration tank 44 increases due to clogging over time, the wastewater in the water tank 46 is supplied from the back washing line 52 to the sand filtration tank 44 by the transfer pump 51 and back washing is performed. Done. As a result, the iron compound precipitate collected in the sand filtration tank 44 is sent from the drain line 61 to the backwash drain tank 60. And when the level of the wastewater containing a small amount of iron compound precipitate stored in the backwash drainage tank 60 exceeds a predetermined value, the transfer pump 65 is activated by a detection signal from the level meter 63 that detects this, and the above Waste water containing the iron compound precipitate is sent from the return line 64 to the storage tank 7.

  As described above, according to the reaction tanks 10a to 10d incorporated in the processing plant, since the inside of the reaction tank main body 70 has an airtight structure in which the inflow of air is blocked, the air vent 84 can be used in the initial stage of operation. By exhausting the internal air and filling the reaction tank main body 70 with the drainage or the like, a reducing substance such as ferrous sulfate is not oxidized by the air. Can be efficiently reduced / removed without providing a device for supplying water or a device for heating to a high temperature.

  Further, by supplying the drainage or the like from the supply pipe 71 along the inner wall of the reaction tank main body 70, a swirl flow from the lower part to the upper part of the reaction tank main body 70 is generated, and the wall surface obstructs the swirl flow. The drainage or the like can be effectively agitated by forming a vortex flow by the plate 73 or the wing-type baffle plate 77 or changing the flow direction in the vertical direction. For this reason, since the stirring means which penetrates the reaction tank main body like the conventional stirrer becomes unnecessary, the reaction tank main body 70 itself is made into a very simple structure, and the inside of the reaction tank main body 70 is easily airtightly sealed. be able to.

  Furthermore, since the supply pipe 71 is connected to the vicinity of the bottom of the reaction tank main body 70 and the discharge pipe 72 is connected to the vicinity of the ceiling of the reaction tank main body 70, the reducing iron compound precipitate generated in the drainage or the like is placed at the bottom. Can be sent from the discharge pipe 72 to the subsequent reaction tanks 10b to 10d along with the drainage supplied from the reactor, and thus the sediment can be prevented from being deposited on the bottom of the reaction tank body 70 in advance. can do. Further, since the reducing iron compound precipitation tends to settle in the reaction tank body 70 due to gravity, the iron compound precipitation and heavy metal-containing water supplied from the bottom of the reaction tank body 70 undergo a contact reaction. A lot of time and opportunity can be taken, and more effective processing can be performed.

  In addition, since a gap 74 is formed between the wall baffle plate 73 and the inner wall of the reaction vessel main body 70 as a flow path for the drainage or the like, a swirl flow from the lower portion to the upper portion of the reaction vessel main body 70 is formed. In addition, it is possible to prevent the formation of a dead area in which the flow is prevented at the corner of the joint between the wall surface baffle plate 73 and the inner wall.

  In addition, a return pipe 78 for returning the drainage extracted from the discharge pipe 72 of the reaction tank main body 70 to the supply pipe 71 side is provided, and a pH meter 80 for measuring pH is provided in the return pipe 78 to provide the inside of the reaction tank 10a. Since the pH value is adjusted, the above-described pH value retention control can be reliably performed.

In the above embodiment, when applied to a reaction vessel used in a treatment plant for reducing and removing the heavy metals by adding ferrous sulfate as a reducing substance to water containing heavy metals such as waste water. However, the present invention is not limited to this, and the reaction vessel according to the present invention is not limited to water containing various heavy metals, other ferrous compounds such as ferrous chloride (FeCl ₂ ), It can be widely used for reducing and removing heavy metals by adding other substances having reducibility to heavy metals.

It is a longitudinal cross-sectional view which shows one Embodiment of the reaction tank which concerns on this invention. It is the II-II sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is a perspective view which expands and shows the attachment part of the wall surface baffle plate of FIG. It is a perspective view which expands and shows the attachment part of the wing | blade type baffle plate of FIG. It is a schematic block diagram which shows a part of processing plant in which the reaction tank of FIG. 1 is used. It is a schematic block diagram which shows the other part of FIG.

Explanation of symbols

10a to 10d Reaction tank 70 Reaction tank body 71 Supply pipe 72 Discharge pipe 73 Wall baffle plate (first baffle plate)
74 Clearance 77 Wing-type baffle (second baffle)
78 Return pipe 79 Circulation pump 80 pH meter 81 Storage tank 82 Pump

Claims (5)

A reaction tank for reducing and removing heavy metals with the reducing substance while stirring the heavy metal-containing water to which the reducing substance has been added while the air inflow is blocked,
A reaction tank main body hermetically sealed, the heavy metal containing water supply pipe connected to one of the upper or lower part, and the heavy metal containing water discharge pipe connected to the other, and the reaction tank A first baffle plate provided in the vertical direction on the inner wall of the main body and projecting inward from the inner wall, and the supply pipe supplies the heavy metal-containing water to the reaction tank main body. The reaction is characterized in that the heavy metal containing water is connected so as to generate a swirling flow from the one side to the other side in the reaction tank body by introducing it in the direction along the inner wall of the reaction tank body. Tank.   2. The reaction according to claim 1, wherein the supply pipe is connected to a lower part of the reaction tank body, and the discharge pipe is connected to an upper part of the reaction tank body. Tank.   The reaction tank according to claim 1, wherein a gap serving as a flow path for the heavy metal-containing water is formed between the first baffle plate and the inner wall of the reaction tank main body. .   The second baffle plate that extends in the horizontal direction and faces the swirl flow is provided on at least one of the upper part and the lower part in the reaction vessel main body. Reaction tank.   The heavy metal-containing water extracted from the other of the upper part or the lower part of the reaction tank body, having a return pipe piped between the upper and lower parts of the reaction tank body and a circulation pump interposed in the return pipe A pH line for measuring the pH of the heavy metal-containing water flowing in the return pipe and interposed in the return pipe, and the pH meter. The reaction tank according to any one of claims 1 to 3, further comprising pH adjusting means for supplying an alkaline aqueous solution in the storage tank to the supply line based on a detection signal from the storage tank.

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