JPH0512978B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for removing suspended substances such as iron oxides trapped in a packed bed by passing raw water through the packed bed. [Prior art and its problems] In a method of purifying water by passing water through a packed bed, especially a packed bed of ion exchange resin, cruds such as iron oxide with a high specific gravity trapped in the packed bed are removed. Various methods have been proposed. For example, in a condensate desalination equipment for a power generation boiler, water is passed through a demineralization tower filled with ion exchange resin for a certain period of time, and then the ion exchange resin is transferred to a regeneration tower and then backwashed to remove suspended matter (cruds). is being removed. The conventional method will be explained below based on the drawings. FIG. 2 is a schematic diagram showing a commonly used crud removal method, in which reference numeral 1 indicates a regeneration tower;
2 is an ion exchange resin layer in a settled state, 3 is an ion exchange resin layer in a scrubbed state, 4 is an ion exchange resin layer in a backwash state, 5 is a lower water collection device, 6 is an upper water collection device, 7, 8, 9, 10 are pipes for introducing or discharging air or water, 11, 12, 13,
14 indicates a valve provided on the pipe, () indicates a draining process, () indicates an air scrubbing process, ()
indicates the backwashing process. Also, A and A' indicate air, and B indicates backwash water. The following description will be made based on FIG. 2, and only the parts () and () in FIG. 2 that are necessary for the explanation are given the reference numerals. In the method shown in FIG. 2, after the ion exchange resin (hereinafter simply referred to as resin) is transferred to the regeneration tower 1,
Open the valve 11 of the pipe 7 and the valve 13 of the pipe 9, pressurize the air A from the pipe 9, and drain the water through the pipe 7 until the water surface reaches the position _L1 at the top of the resin layer 2 (Fig. 2). Then, valve 11 and valve 13 are closed, and valve 12 is closed.
and open the valve 14 to allow the pipe 10 to pass through the upper water collection device 6.
After scrubbing the resin by introducing air A' into the lower part of the resin layer from the lower water collection device 5 through the pipe 8 while exhausting air from the pipe 8 (Fig. 2), the valve 12 is closed and the valve 1
1 is opened and backwash water B flows from pipe 7 through the lower water collection device.
is introduced into the lower part of the resin layer, and the resin is backwashed while the backwash wastewater is discharged from the pipe 10 via the upper water collection device 6 (FIG. 2). In this method, the above steps (draining - air scrubbing - backwashing) are repeated about three times to increase the crud removal rate. In this method, (1) there is a limit to the flow rate of backwash water (maximum 15 m/h), and the time required to separate (discharge) the crud is long because the backwash water is discharged from the water collection device at the top of the regeneration tower; (2) Due to the limited flow rate of backwash water, it is difficult for heavy crud to be transported to the top of the tower, and (3) After backwashing, air scrubbing is performed again, so water must be drained. There are disadvantages such as increased amount of waste liquid. FIG. 3 is a schematic diagram illustrating an improved method for removing heavy crud;
The apparatus itself and the symbols are the same as those shown in FIG. 2, and only the symbols necessary to explain this improved method have been written. In Figure 3, () is the drain process, () is the air scrubbing process, ()
indicates a rapid draining process, and () indicates a water filling process. In Fig. 3, the draining process in parentheses is the same as that explained in Fig. 2, but after performing air scrubbing for a certain period of time in the air scrubbing process in parentheses, the resin layer is formed by air A introduced from the bottom. During the development, the valves 12 and 14 are closed, and at the same time, the introduction of air A' from the pipe 8 to the resin layer 3 is stopped.
By rapidly opening the valves 11 and 13, air A is forced into the pipe 9 and drained all at once through the pipe 7 (rapid drain step in Fig. 3). Then, after closing the valve 11 and opening the valves 13 and 14 to replenish water from the pipe 10 to the height of _L1 (water filling step in FIG. 3), the process returns to the air scrubbing step. Although this method is effective in removing heavy crud, the amount of drainage per operation is small (only the difference between L ₁ and L ₀ in Figure 3 can be drained), and therefore air scrubbing, rapid draining, and water filling ( ) to () steps 10 to 30
The process is complicated as it needs to be repeated several times. Figure 4 is for explaining a method that improves the method shown in Figure 2 and drains water from an intermediate water collection device after backwashing. Reference numerals 1 to 14 are the same as those in Figure 2. They have the same meaning, 15 is an intermediate water collection device, 16 is its piping, 17 is a valve, () is a drain process, () is an air scrubbing process,
() indicates the backwashing process, and () indicates the draining process from the intermediate water collection device. In the method shown in FIG. 4, the drain step () and the air scrubbing step () are the same as the method shown in FIG. After introducing the water to the height of _L2 , valves 11 and 14 are closed, valves 13 and 17 are opened, and air is forced in from pipe 9, and the backwash water existing above is transferred from the intermediate water collection device to the intermediate water collection device 15 and The water is drained from a drain pipe 16. Although this method requires less time and waste liquid to separate the crud than the method shown in FIG. 2, the removal of heavy crud is not as sufficient as the method shown in FIG. [Object of the invention] The object of the present invention is to improve the drawbacks of the above conventional method,
It is an object of the present invention to provide a method for separating heavy crusts which requires a short separation time and produces a small amount of waste liquid. [Structure of the Invention] The present invention provides a method of scrubbing while simultaneously introducing air and water from the lower part of the packed bed, and (1) passing through the filler provided on the surface layer of the packed bed that is expanded by the scrubbing. (2) discharging water from an intermediate water collection device having a structure that allows only suspended matter and finely divided filler to pass through without letting the water pass through the intermediate water collection device, and exhausting air from the upper part of the intermediate water collection device; This is a method for removing suspended matter and finely divided filler from a packed bed, which is characterized by repeatedly carrying out both the steps of draining water from the device and exhausting the device. In order to improve the drawbacks of the conventional method as described above, the present inventors have developed a method that is effective even for heavy crusts with large particle sizes, that is, crusts that have a high sedimentation rate, and that requires a short separation time and is effective for waste liquid. The present invention was developed as a result of intensive research into a method for removing crud that requires only a small amount of crud. The method of the present invention will be explained based on FIG. In FIG. 1, the same symbols as those shown in FIG. 4 have the same meaning, and S indicates sluicing water introduced together with air A'. In the drain step shown in parentheses in FIG. 1, water is drained to the level (L ₁ ) of the intermediate water collection device 15. The air-water scrubbing steps () and () of the present invention are then repeated. The present invention
Its basic feature is to simultaneously introduce air A' and sluicing water S from the lower water collection device 5 while discharging the air and/or water from the intermediate water collection device 15 through the valve 17 and pipe 16. Heavy crud with a high velocity is conveyed from the lower part of the resin layer to the intermediate water collecting device 15 by the upward flow of air A' and sluicing water S at high velocity, and is removed through the pipe 16. Air-water scrubbing process () shown in Figure 1
In this case, valves 14 and 17 are open, and drainage is carried out from the intermediate water collection device 15 through pipe 16. Since valve 14 is open, exhaust is not carried out from pipe 16, but is discharged from the upper part of the tower. This is done via tube 10. In the air-water scrubbing step (), the valve 14 is closed and the valve 17 is opened, so that exhaust is not carried out from the upper part of the tower, and the flow of water and air is concentrated in the intermediate water collection device 15, and the pipes are 16 and are simultaneously discharged out of the system. In normal backwashing using only water, when draining water from the intermediate water collection device 15, it becomes difficult to drain the resin deposited on the intermediate water collection device. However, in the case of the process (2) of the present invention, in which water and air are simultaneously introduced for scrubbing, the resin layer, especially its surface layer, is shaken violently, so even if the resin is deposited in the intermediate water collection device, the deposited As the resin layer breaks down easily and the "surface" of the intermediate water collection device for drainage and exhaust is constantly renewed, it was confirmed through experiments that there was no problem in draining the crud. The flow rate of air A' from the lower water collection device may be LV50 to 100 m/hour, which is normally used for air scrubbing, and the flow rate of sluicing water S is usually backwash water B.
Slightly smaller than the LV6~15m/hour used in
LV4-10m/hour is preferred. In the method of the present invention, the transport and removal of crud is carried out not only by sluicing water S but also by air, and the flow rate of sluicing water S does not need to be as high as that of conventional backwash water B. . In the present invention, the air-water scrubbing steps () and () are performed alternately, and it is preferable to perform the step () for a long time as shown in the example below. Air-water scrubbing process (): 1 to 5 minutes 〃 (): 0.5 to 2 minutes As an example, the intermediate water collection device 15 has a slit width
It was confirmed that steps () and () could be carried out smoothly by using a wire screen of 200 to 400 μm and making the opening area of the screen sufficiently large. Step () is open to the atmosphere, and the position of the resin surface layer during scrubbing is maintained at position a near the top surface of the intermediate water collecting device 15 as shown in FIG. The surface is constantly updated. Since this is open to the atmosphere and there is some resistance on the surface of the intermediate water collection device during drainage, the position of the resin surface layer is as shown in FIG. 5a. On the other hand, in step (), the valve 14 is closed and exhaust is also performed from the pipe 16, so the inside of the tower is pressurized, and the position of the resin surface layer during scrubbing is at the intermediate water collection device 15 as shown in position b in Fig. 5. It will be below the center of the pipe. In the present invention, step () alone is sufficient to perform (1) peeling off the crud from the resin, and (2) transporting the crud to the intermediate water collecting device 15, among the crud removal actions. However, for another important function, the discharge function from the intermediate water collecting device 15, step () alone is not sufficient. As an example, the wire screen used in the present invention is as shown in FIG. 6, and the crud or fine resin smaller than the width of the slit 18 passes smoothly through the slit and is discharged. Also, if the material is sufficiently larger than the width of the slit 18, it will be fluidized without blocking the slit surface due to the agitation effect during scrubbing. However, the cladding or fine resin having a size close to the slit width gets caught in the slit, which is the discharge surface, and is difficult to be discharged, and also blocks the discharge surface. Therefore, if step () is carried out for a long time, the surface layer of the resin during scrubbing gradually rises beyond position a shown in FIG. Process () solves these drawbacks of Process (). In step (), drainage and exhaust are carried out only through the pipe 16, and the inside of the column is pressurized to 1 to 2 Kgf/cm ² to form fine cladding with a size close to the width of the slit that closes the slit 18 mentioned above. It has the effect of forcibly discharging the hardened resin by applying pressure. Since this discharge action is achieved in a very short time, it is sufficient to complete step () for about 0.5 to 2 minutes. In FIG. 6, an arrow 19 indicates the flow direction of the cladding or finely divided resin, water, and air, and the reference numeral 20
The rods forming the wire screen which is the intermediate water collection device 15 are triangular in shape or similar in shape as shown in FIG. Such a shape is effective for discharging crud and fine resin. Since the width of the slits 21 on the inside of the tube of the wire screen is larger than the width of the slits 18 on the outside of the tube, a cladding having a diameter close to the width of the slit 18 that is caught in the slit 18 on the outside of the tube and blocks the slit 18 in the above-mentioned step (2) is formed. , the forcible removal of the finely divided resin is carried out smoothly. As an example, a device having functions as shown in FIG. 6 is preferable for implementing the present invention. By eliminating step () and performing only step (), the position b of the resin surface layer will be below the center of the intermediate water collection device 15, as shown in Fig. 5, and the entire surface of the pipe of the intermediate water collection device will not be used for draining the crud. It's not a good idea because it won't happen. In this way, the present invention eliminates the drawbacks of performing only step () or only step ().
By repeating [Step ()→Step ()], it is possible to effectively remove crud and fine resin. Hereinafter, the present invention will be explained in detail based on FIG. First, the water level in the regeneration tower 1 is brought to the position (L ₁ ) of the intermediate water collection device 15 through the drain step (). This operation is performed by opening the valves 13 and 17 and connecting the pipes 9 to 1 to 2.
This is done by injecting pressurized air A at kgf/cm ² . In addition, the distance between the intermediate water collecting device 15 and the surface of the resin 2 should be set to a value of 15 to 30% of the height of the resin layer 2 so as to be suitable for the following steps () and (). is preferable. Then, the valve 13 is closed and air A' is introduced from the pipe 8.
The process moves on to step (2) in which sluicing water is introduced through the pipe 7, exhausted through the pipe 10, and drained through the pipe 16 via the intermediate water collecting device 15. The flow rates of air and sluicing water in step () are as follows. Air: LV50~120m/hour Pressure 1~2Kgf/ ^cm2 Slewing water: LV4~10m/hour Such operations can be carried out as part of the mixing operation in the mixed bed, or by the conventional method () shown in Figure 2. Before the scrubbing operation using only air in the process, sluicing water is sometimes introduced for a very short time at LV 2 to 3 m/hour, but the process () of the present invention applies these operations and The time is increased and the flow rate of the sluicing water is increased. If the resin layer is composed of a cationic resin with a high specific gravity, the sluicing water should be LV6~10m/
It is appropriate to set the air LV to 70 to 100 m/hour. In the case of anionic resins with low specific gravity, it is appropriate to set the LV of sluicing water to 4 to 8 m/hour and the LV of air to 70 to 100 m/hour. Step () may take about 2 to 5 minutes, but if the crud is strongly adhered to the resin, the conventional method shown in Figure 2 involves stopping the introduction of sluicing water S and introducing only air before step (). One idea is to perform the steps in parentheses. This is because when the introduction of sluicing water S is stopped, the amount of water in the resin layer 3 decreases, and the resin slurry concentration in the resin layer 3 increases, which increases the rubbing of the resins against each other and makes it easier for the crud to peel off. Next, move on to process (). By keeping the valve 17 open and closing the valve 14, the exhaust air is also routed through the intermediate water collecting device 15 to the pipe 1.
It will be held from 6 onwards. The set values for the flow rates of air A', sluicing water S, etc. may be the same as in step (). In this way, a pressure of 1 to 2 Kgf/cm ² of air A' is applied to the inside of the regeneration tower 1, and the position of the surface layer of the resin layer 3 is lowered as shown by b in FIG. This process forcibly discharges the fine resin and the crud, which has a size close to the width of the slit 18 and is caught in the slit 18 and prevents drainage, and takes about 0.5 to 2 minutes, usually about 1 minute. good. Then, repeat [process () → process ()] again. The number of repetitions is approximately 5 to 15 times in the case of the setting values shown in Table 1 below.

[Table] The intermediate water collection device used in the present invention is preferably a wire screen type as shown in FIG. 6, but any device having the same function may be used. Next, Examples and Comparative Examples will be shown. Comparative example: Cation exchange resin 2600 and anion exchange resin 1400 were transferred from a desalination tower through which water was passed for 30 consecutive days during normal operation of a thermal power plant to a 1600φ x 4000mm ^H cation regeneration tower.
After transferring the anion exchange resin to the anion regeneration tower, the cation exchange resin is used in the cation regeneration tower, and the anion exchange resin is used in the anion regeneration tower (1200 φ x 2800 mm ^H ) under the following conditions according to the conventional method. I did the removal. Conventional method 1 (method shown in Figure 2) Process () 5 minutes Process () Air LV 100 m/hour 15 minutes Process () Backwash water: Cation regeneration tower LV 15 m/hour 30 minutes Anion regeneration tower LV 8 m/hour 30 minutes Process ( ) () Repeat 4 times Conventional method 2 (method shown in Figure 3) Process () 5 minutes 1st time 2nd and subsequent times Process () Air LV100m/hour 15 minutes 3 minutes Process () 2 minutes 2 minutes Process () 3 minutes 3 minutes Number of repetitions of process () () () 15 times Conventional method 3 (method shown in Figure 4) Process () 5 minutes 1st time 2nd time onwards Process () Air LV100m/hour 15 minutes 10 minutes Process () Backwash water: Cation regeneration tower LV15m/hour 6 minutes 6 minutes Anion regeneration tower LV8m/hour 6 minutes 6 minutes Process () 5 minutes 5 minutes Number of repetitions of steps (), (), () 4 times or more The results are shown in Table-2. Example 1 Similar to the comparative example, crud removal was carried out using the same resin from the same demineralization tower through which water was passed for 30 consecutive days during normal operation. The cation regeneration tower and anion regeneration tower used were the same size as in the comparative example. The interior parts of the tower were modified for use in the present invention. The intermediate water collection device used was as follows. Cation regeneration tower: Wire screen slit opening area with 300 μm slits 793 m ² Anion regeneration tower: Wire screen slit opening area with 300 μm slits 440 m ² Both the cation regeneration tower and anion regeneration tower are processed under the following conditions (), (). Process () Air: LV100/hour Slewing water: LV8m/hour 3
Minutes Process () Same as above 1 minute The results are shown in Table-2. In addition, in Table 3, Fe
The concentration is the average iron concentration contained in the resin when the cladding is removed in the cation regeneration tower and the anion regeneration tower and both resins are regenerated, then mixed in the resin mixing tank and transferred to the desalination tower.

〔Effect of the invention〕

As can be seen from Table 2 above, the method of the present invention is superior to the conventional method in terms of cleaning time, amount of cleaning waste water, and amount of air used, making it a great contribution to industry.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the steps of the present invention, FIG.
3 and 4 are process diagrams showing different conventional methods, and FIG. 5 is a diagram showing the position of the resin surface layer during scrubbing in the intermediate water collection device used in the present invention,
FIG. 6 is a diagram showing an example of an intermediate water collection device used in the present invention. 1... Regeneration tower, 2... Resin layer, 5... Lower water collection device,
6...Upper water collection device, 15...Intermediate water collection device, A,
A'...Air, S...Throughing water.

Claims (1)

[Claims] 1 While scrubbing the packed bed by simultaneously introducing air and water from the bottom of the packed bed, (1) the scrubbing does not allow the filling material provided on the surface layer of the packed bed to pass through, and the suspension is a step of draining water from an intermediate water collection device having a structure that allows only substances and finely divided filler to pass through, and exhausting air from the upper part of the intermediate water collection device; (2) draining and exhausting from the intermediate water collection device; 1. A method for removing suspended matter and finely divided filler in a packed bed, the method comprising repeatedly carrying out both steps.