JP2005007386A - Sludge washing method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a sludge washing method capable of effectively and continuously treating sludge containing toxic or unwanted components such as heavy metals, and its apparatus. <P>SOLUTION: While the sludge together with a flocculant is charged into the top of a washing column 1, fresh water and a washing agent are supplied thereto from the lower part of the washing column 1. The inside is stirred by a stirrer 6 to flocculate and settle the sludge, at the same time, the toxic or unwanted components inside the sludge are moved in the fresh water. While overflow water is discharged, the settled sludge while washing is extracted from a discharge port 4 at the bottom for recycling. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for cleaning sludge that removes harmful or unnecessary components such as heavy metals and other contaminated soils containing undesired or unnecessary components, sludge in water treatment, waste incineration ash, etc. (hereinafter simply referred to as “sludge”), and It relates to the device.

  Since contaminated soil containing harmful or unnecessary components such as heavy metals, sludge in water treatment, waste incineration ash, etc. can not be landfilled as it is, some kind of cleaning treatment to remove these harmful or unnecessary components is necessary Various proposals have been made. For example, Patent Document 1 discloses a device and a method for purifying contaminated soil by a circulation method. This will be briefly described with reference to FIG.

  FIG. 4 is a schematic view of a cleaning tank showing an embodiment of the prior art described in Patent Document 1. 91 is a cleaning tank with a lid, 92 and 93 are supply ports for a solvent or cleaning agent, and 94 is a discharge port. , 95 is a cleaning agent supply pump, 96 is a circulation pump, 97 is a discharge pump, 98a to 98d are operation valves, F is a filtration filter, and 99 is a supporting portion thereof.

  The lid of the cleaning tank 91 is opened, and sludge to be cleaned is put inside. Since the filtration filter F is laid on the lattice-like support part 99 inside the cleaning tank 91, the introduced sludge is deposited thereon.

  The operation valves 98c and 98d are closed, 98a and 98b are opened, the solvent or cleaning agent is supplied into the cleaning tank 91 from the upper supply port 92 by the supply pump 95, and the solvent or cleaning agent is cleaned in the cleaning tank 91 by the circulation pump 96. After the agent is circulated for a predetermined period of time, harmful or unnecessary components such as oil, PCB, dioxin, etc. in the sludge are extracted into the solvent or cleaning agent to purify the sludge, and then the purified mud remaining in the cleaning tank 91 is removed. The operation valve 98d is opened, and the solvent or cleaning agent in the cleaning tank 91 is discharged by the discharge pump 97.

If the operation valve 98b is closed and the operation valve 98c is opened to supply the solvent or the cleaning agent into the cleaning tank 91 from the lower supply port 93, the clogging of the filter F can be eliminated.
JP 2003-88847 A

  By the way, in the conventional technique described in Patent Document 1, since it is a batch process in which sludge is put into the washing tank 91 by a predetermined amount, the efficiency is low, and it is harmful because the amount of extraction in one circulation is small. In addition, in order to reduce unnecessary components to a predetermined concentration or less, there is a problem that a large number of circulations are required and a long time and a large amount of fresh water are required.

  The present invention eliminates such problems in the prior art and realizes a method and apparatus for cleaning sludge that can efficiently and continuously remove harmful or unnecessary components in sludge with a small amount of fresh water. The purpose is to do.

  In the sludge cleaning method of the present invention, the sludge is added to the top of a vertically long cylindrical cleaning tower together with a flocculant, while fresh water is supplied into the tower from the lower portion of the cleaning tower, and the inside of the tower is stirred to obtain the sludge. Is characterized in that harmful or unnecessary components in the sludge are transferred into the new water at the same time as the coagulated and settled, the overflow water is discharged, and the sludge that has settled while being washed is drawn out from the bottom of the washing tower. In addition, the sludge to which the cleaning agent has been added in advance is added to the top of the vertical cylindrical cleaning tower together with the flocculant, while fresh water is supplied into the tower from the bottom of the cleaning tower, and the inside of the tower is stirred to aggregate the sludge. At the same time as sedimentation, harmful or unnecessary components in the sludge are transferred into the new water, the overflow water is discharged, and the sludge that has settled while being washed is extracted from the bottom of the washing tower. In addition, sludge is added together with a flocculant to the top of a vertically long cylindrical cleaning tower, while fresh water and a cleaning agent are supplied into the tower from the bottom of the cleaning tower, and the inside of the tower is stirred to agglomerate and settle the sludge. At the same time, the harmful or unnecessary components in the sludge are transferred into the new water, and the overflow water is discharged and the sludge that has been washed and washed out is extracted from the bottom of the washing tower, or is washed. The sludge extracted from the bottom of the tower is put together with the flocculant into the top of the next-stage washing tower, and the sludge that settled while being washed by the above-described washing treatment is withdrawn from the bottom of the next-stage washing tower. The cleaning process is repeatedly performed.

  Further, the sludge cleaning apparatus of the present invention is a vertical cylindrical cleaning tower, an inner cylinder attached to the top of the cleaning tower and provided with a sludge inlet and a flocculant injection nozzle, and sludge settled from the bottom of the cleaning tower. A discharge pump for extracting water, a transfer pump connected thereto, a new water nozzle for supplying fresh water and cleaning agent into the tower from the lower part of the washing tower, a stirrer for stirring the inside of the tower, and an overflow from the top of the washing tower Or an overflow tank for receiving overflow water, or a cleaning nozzle for supplying a cleaning agent into the tower from the center of the cleaning tower in addition to the new water nozzle. Alternatively, a plurality of the above-described washing towers are installed, and the discharge port at the bottom of the previous stage is connected to the input port at the top of the next stage through a transfer pump.

  ADVANTAGE OF THE INVENTION According to this invention, the harmful | toxic or unnecessary component ionized, such as a heavy metal, can be removed efficiently and continuously, and there exists an outstanding effect that sludge can be safely used effectively for a landfill and others.

  First, a cleaning tower as a basic unit of the cleaning apparatus of the present invention will be described with reference to FIG. This figure is a conceptual diagram showing the structure of a single washing tower. 1 is a vertically cylindrical washing tower (main body), 2 is an inlet for introducing slurry sludge to be treated, and 3 is an upper part of the washing tower 1 4 is provided at the bottom of the washing tower 1 to discharge the settled contents, 5 is a transfer pump for extracting the contents from the outlet and transferring them, 6 is the washing tower 1 A stirrer composed of a rotating shaft and a plurality of propellers provided in the vertical direction inside, 7 is inserted into the lower part of the washing tower 1, and a fresh water nozzle for supplying fresh water (also referred to as clean water or purified water) into the washing tower 1, Reference numeral 8 denotes a cleaning agent nozzle that is inserted near the middle stage of the cleaning tower 1 and supplies the cleaning agent into the cleaning tower 1. Reference numeral 9 denotes a flocculant injection nozzle that mixes the flocculant with the sludge to be charged. An overflow tank into which overflowing liquid flows, 11 is an overflow tank A overflow pipe pouring off the overflowing water from.

  The washing tower 1 of the present invention is a settling pipe with a rake as a basic structure, and the sludge to be treated is put together with the flocculant into the inner cylinder 3 at the top, and dropped into a tower filled with fresh water, The flocs are generated and settled, and the fresh water rising from below is brought into contact with the cleaning agent in countercurrent, and the flocs that have settled while being washed, that is, the sludge is pulled out from the bottom, and at the same time, harmful and unnecessary components are extracted. It has the function of draining water from the top.

  The harmful or unnecessary components in the sludge targeted by the present invention are ionized by the cleaning agent in the present invention, and these chemical changes cause the harmful or unnecessary components to be ionized and transferred into fresh water, Is washed.

  The cleaning agent is basically an acid such as hydrochloric acid, sulfuric acid or nitric acid, or an alkali such as caustic soda or caustic potash, but an oxidizing agent, reducing agent, enzyme or the like can also be used. Further, for example, when cleaning originally water-soluble sludge such as sea sand purification or when cleaning ionized sludge, no cleaning agent is required.

  The cleaning agent may be added to fresh water. Further, instead of contacting the cleaning agent in the cleaning tower, the cleaning agent may be added to the sludge to be cleaned in advance and then introduced into the cleaning tower together with the flocculant. In particular, when the harmful substance is a heavy metal, it is not easy to ionize in a short time contact, so prior addition is preferable. In these cases, the cleaning agent nozzle 8 in FIG. 1 can be shared by the fresh water nozzle 7 or can be omitted at all. On the other hand, when a large amount of cleaning agent is used, it is supplied using the cleaning agent nozzle 8 in the middle of the cleaning tower, that is, at the position of the equilibrium layer that is intermediate between the downward flow and the upward flow as shown in FIG. Concentration is retained and is most effective.

  Examples of the flocculant include nonionic, anionic, cationic, and other organic polymer systems such as polyacrylamide, polyacrylic acid, polymethacrylic acid ester, polyacrylic acid ester, and polyamidine polymer flocculants. preferable. By aggregating, the apparent specific gravity is increased to promote sedimentation, and the effect of dissolving harmful or unnecessary components can be enhanced by stirring and floc breakage by a transfer pump. The amount added is about 0.01 to 1.0% with respect to the solid content of the sludge.

  Sludge, flocculant, fresh water and cleaning agent are fed into the system, and floc settled at the bottom and overflow water from the top are removed from the system. As will be described later, by installing this washing tower 1 in multiple stages and repeating the same process, the floc taken out from the last washing tower 1 becomes purified mud containing almost no harmful or unnecessary components, and is safe as landfill soil and others. Can be reused. On the other hand, harmful or unnecessary components are extracted into the overflow water from each stage, and these may be collected and treated in a conventionally known water treatment facility.

  The sludge and the flocculant may be separately charged and injected as shown in FIG. 1, or those previously mixed or flocked may be charged. In order to carry out the agglomeration reaction early and efficiently, it is preferable that they are not charged directly into the tower, but are poured into an inner cylinder not mixed with water and dropped into the tower from the soot portion.

  The transfer pump is preferably a centrifugal pump, a gear pump or the like having a high floc crushing capacity. The stirrer is a multi-stage paddle type, and the rotation is low to medium speed of about 10 to 200 rpm.

  FIG. 2 is a block diagram showing an example of a sludge cleaning facility in which the cleaning tower 1 shown in FIG. 1 is combined in four stages. Four washing towers 1a, 1b, 1c, 1d of the same structure are installed side by side, and flocculant, washing agent, and fresh water are charged or injected into each washing tower 1a, 1b, 1c, 1d, The overflow water from the washing towers 1a, 1b, 1c, 1d is finally collected in a water treatment facility. In FIG. 2, since the harmful component content of the overflow water in the second and subsequent stages is extremely low, the overflow water in the subsequent stage is used as new water in the previous stage to reduce the amount of new water used and the load on the water treatment facility. Although an example of the case is shown, it is needless to say that the overflow water of each stage may be collected in one water treatment facility in parallel and the new water may be connected to the new water nozzles of each stage. Furthermore, it is possible to reuse the water after being treated in the water treatment facility as “new water”.

  The sludge to be treated is introduced into the inlet 2a of the first stage cleaning tower 1a, and from the outlet 4a through the transfer pump 5a, through the second stage inlet 2b into the cleaning tower 1b. Similarly, it is finally taken out from the system by the transfer pump 5d from the fourth stage outlet 4d as purified mud.

  In the example of FIG. 2, the sludge is repeatedly subjected to the same washing process four times. According to the experiments by the present inventors, the floc behavior in the first-stage washing tower 1a and the second and subsequent stages There are some differences. This will be briefly described with reference to FIG.

  FIG. 3A is a schematic diagram showing the inside of the first-stage washing tower 1a. Slurry sludge and flocculant are put into the inner cylinder 3, and flocs are generated by the action of the flocculant in the process of dropping into the tower from the soot part, and the diameter gradually increases and settles downward. To do. On the other hand, (b) is a schematic diagram showing the inside of the second and subsequent cleaning towers 1b (1c, 1d). The contents extracted from the first-stage washing tower 1a are once crushed when passing through the transfer pump 5a, so that the flocs are once crushed. Settling in the tower as a floc with little tightness. Compared to the first stage, the sedimentation rate is fast, and the washing efficiency, recovery rate, and concentration rate are high. And it settles and deposits in the range of height h from a bottom part, and forms a sludge zone. As will be described later, the sludge zone height h is determined by the amount of fresh water injected and the amount drawn by the transfer pump. It does not change.

  Stirring has the effect of accelerating the agglomeration reaction and making the flow in the tower uniform and tightening the flocs. At the bottom of the washing tower, the concentration of the slurry rises due to the consolidation effect of the accumulated flocs, and the efficiency is improved by reducing the amount of drawing.

  The change of the component in the Example of this invention between this is demonstrated by experimental data.

  Table 1 shows the properties and analysis results of sludge used in the experiment and fresh water for cleaning. Assuming the heavy metal to be removed, iron ions were added to the sludge, acid was used as the cleaning agent, and the pH value was adjusted to about 4 by adding in advance. In order to grasp the ionization state as an index of the cleaning effect, sodium chloride was added to measure the electrical conductivity. The amount of coarse suspended solids is the remaining amount by 200 mesh wire net filtration based on the sewer test method. In addition, although each numerical value below Table 2 has abbreviate | omitted the unit display, all are the same as Table 1. The experimental apparatus has the shape shown in FIG. 1, and has an inner diameter of the washing tower of 85 mm, an effective height of 500 mm, and a volume of 3 liters.

  Table 2 shows an operation example in which a flocculant is not mixed for comparison and no stirring is performed in the tower. The operating conditions are 30 liters per hour of sludge input from the inlet, 30 liters of fresh water injection for cleaning, 30 liters of content discharged from the bottom outlet, 30 liters of overflow water from the overflow tank, Table 2 shows the properties and analysis results of the overflow water and the discharged contents.

Now
Washing efficiency = Electric conductivity of the input ÷ (Electric conductivity of the effluent-Electric conductivity of fresh water)
When compared with the original sludge in Table 1, the cleaning efficiency in terms of electrical conductivity in the discharge is 2.2, and the cleaning efficiency in terms of iron ion concentration is 2.5. The solids recovery rate, that is, the ratio of the solids of the discharged contents to the sum of the solids of the overflow water and the discharged contents is 48.9%.

  Table 3 shows data when the other conditions are exactly the same and stirring in the column is performed. The stirrer was provided with three paddle-shaped blades in three stages and stirred at 100 rpm. The cleaning efficiency is not so different from Table 2, and the solid recovery rate is rather lowered.

  The following data shows the coagulant mixed in the sludge. Table 4 shows the same operating conditions as in Table 3, except that 0.1% of the organic polymer flocculant was mixed in the amount of solids in the sludge. The amount of fresh water injected is 30 liters per hour as before, but this amount should not exceed the settling rate in the column. Compared with Table 3, the cleaning efficiency is almost the same, but the solids recovery rate is greatly improved.

  Table 5 shows data when the amount of water drawn from the discharge port in Table 4 is halved to 15 liters per hour, and as a result, the amount of overflow water is 45 liters per hour. Other conditions are the same as in Table 4. . As a result of reducing the drawing amount, the recovery rate of suspended solids is slightly reduced, but the cleaning efficiency is almost the same as in Table 4.

  When Tables 2 and 3 are compared with Tables 4 and 5, it can be seen that, even at the pH value, the replacement effect due to the addition of the polymer flocculant appears in the overflowed water and the discharged contents.

  Next, Table 6 shows data when four washing towers are combined in series in four stages as described in FIG. The operating conditions in each stage are: 30 liters of sludge input from the inlet, 30 liters of fresh water injection for washing, 30 liters of content discharged from the bottom outlet, and 30 minutes of overflow water from the overflow tank. In liters, the amount of flocculant mixed in the first stage is 0.1% with respect to the amount of solids, and 0.02% after the second stage. The “cleaning efficiency” for each stage and the “total cleaning efficiency”, which is the total up to that stage, are shown. However, the cleaning efficiency for each stage is almost the same regardless of the electrical conductivity and iron ion concentration. The washing efficiency is improved as the number of stages increases. The final stage shows extremely high values of 24.6 times the electrical conductivity and 55.2 times the iron ion concentration. 99.9%.

  Next, Table 7 shows changes in the cleaning effect in the second stage when the amount of overflow water is changed by changing the drawing amount in the second stage. It can be seen that by reducing the drawing amount, the sludge zone height h increases, but the interface on the upper surface of the sludge zone is stable, the recovery rate does not decrease, and the cleaning efficiency increases significantly.

It is a conceptual diagram which shows the washing | cleaning tower in the washing | cleaning apparatus of this invention. It is a block diagram which shows the sludge washing | cleaning facility of the Example which combined the washing tower shown in FIG. 1 into 4 steps | paragraphs. (A) is a 1st stage, (b) is a schematic diagram which shows the inside of the washing tower after the 2nd stage. It is the schematic of the washing tank in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a-1d Washing tower 2, 2a, 2b Input port 3 Inner cylinder 4, 4a-4d Discharge port 5, 5a-5d Transfer pump 6 Stirrer 7 Fresh water nozzle 8 Cleaning agent nozzle 9 Coagulant injection nozzle 10 Overflow tank 11 Overflow pipe 91 Cleaning tank 92, 93 Supply port 94 Discharge port 95 Supply pump 96 Circulation pump 97 Discharge pumps 98a to 98d Operation valve 99 Support part F Filtration filter

Claims (7)

  Sludge is added to the top of a vertically long cylindrical cleaning tower together with a flocculant, while fresh water is supplied into the tower from the bottom of the cleaning tower, and the inside of the tower is agglomerated and settled at the same time. A method for cleaning sludge, which comprises transferring harmful or unnecessary components into fresh water, discharging overflow water and drawing out sludge that has settled while being washed from the bottom of the washing tower.   While adding sludge to which the cleaning agent has been added in advance to the top of the vertical cylindrical cleaning tower together with the flocculant, fresh water is supplied into the tower from the bottom of the cleaning tower, and the inside of the tower is stirred to coagulate the sludge. At the same time as sedimentation, harmful or unnecessary components in the sludge are transferred into the new water, the overflow water is discharged, and the sludge that has settled while being washed is drawn out from the bottom of the washing tower.   While sludge is added to the top of a vertically long cylindrical cleaning tower together with a flocculant, fresh water and cleaning agent are supplied into the tower from the bottom of the cleaning tower, and the sludge is aggregated and settled by stirring the tower. At the same time, a harmful or unnecessary component in the sludge is transferred into the fresh water, the overflow water is discharged, and the sludge that has settled while being washed is drawn out from the bottom of the washing tower.   The sludge withdrawn from the bottom of the washing tower is put together with the flocculant into the top of the washing tower in the next stage, and the sludge settled while being washed by performing the washing treatment according to any one of claims 1 to 3 A method for cleaning sludge, characterized in that it is extracted from the bottom of the slag and this cleaning process is repeated as necessary.   A vertically long washing tower (1), an inner cylinder (3) attached to the top of the washing tower (2) and a flocculant injection nozzle (9), and the bottom of the washing tower (1) A discharge port (4) for extracting sludge settled from the water, a transfer pump (5) connected thereto, and a new water nozzle (7) for supplying fresh water and cleaning agent into the tower from the lower part of the washing tower (1) ), A stirrer (6) for stirring the inside of the tower, and an overflow tank (10) for receiving overflow water overflowing from the top of the washing tower (1).   The sludge cleaning apparatus according to claim 5, further comprising a cleaning agent nozzle (8) for supplying a cleaning agent from a central portion of the cleaning tower (1) into the tower in addition to the new water nozzle (7).   A plurality of washing towers (1) according to claim 5 or 6 are installed, and the outlet (4) at the bottom of the previous stage is connected to the inlet (2) at the top of the next stage via a transfer pump (5). A sludge cleaning device characterized by that.

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