JPH0141393B2 - - 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 bed. [Prior art] When water is purified by passing water through a packed bed, especially a packed bed of ion exchange resin, various methods are used to remove crud such as iron oxide with a high specific gravity trapped in the packed bed. A method is proposed. For example, in a condensate demineralization system for a power generation boiler, after water is passed through a demineralization tower for a certain period of time, the ion exchange resin is transferred to a regeneration tower, and crud is removed by backwashing the ion exchange resin. ing. The conventional method will be explained below based on the drawings. FIG. 1 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, 14 indicates a drain process, 14 indicates an air scrubbing process, and 14 indicates a backwashing process. Hereinafter, explanation will be given based on FIG. 1, and in FIG. 1, only the parts necessary for explanation are given reference numerals. In the method shown in FIG. 1, after the ion exchange resin (hereinafter simply referred to as resin) is transferred to the regeneration tower 1,
The valve 11 of the pipe 7 and the valve 13 of the pipe 9 are opened, air is pumped through the pipe 9, and water is drained through the pipe 7 until the water surface reaches a position _L1 at the top of the resin layer 2 (the first
Then, valves 11 and 13 are closed, valves 12 and 14 are opened, and air is introduced into the lower part of the resin layer from the lower water collecting device 5 through the pipe 8 while exhausting air from the pipe 10 via the upper water collecting device 6. After scrubbing the resin (Fig. 1), close the valve 12 and open the valve 11 to introduce backwash water into the lower part of the resin layer from the pipe 7 through the lower water collection device, and then the upper water collection device 6. Then, the resin is backwashed while discharging the backwash wastewater from the pipe 10 (FIG. 1). In this method, the above steps (drain-air scrubbing-backwashing) are repeated about three times to increase the crud removal rate. In this method, (1) the flow rate of backwash water is limited (max. 15 m/h), and the time required to separate (discharge) the crud 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; (3) After backwashing, air scrubbing is performed again, so the water must be drained. There are drawbacks such as an increase in the amount of waste liquid. FIG. 2 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. 1, and only the symbols necessary to explain this improved method are written. In FIG. 2, the drain process, the air scrubbing process, the rapid drain process, and the water filling process are shown. The drain process in Figure 2 is the same as that explained in Figure 1, but after air scrubbing for a certain period of time in the air scrubbing process, a valve is opened while the resin layer is being expanded by the air introduced from the bottom. 12 and valve 14 are closed to stop the introduction of air from pipe 8 to resin layer 3, and at the same time, valve 11 and valve 1 are closed.
3 is suddenly opened and air is forced into the pipe 9 to open the pipe 7.
(Rapid drain process in Figure 2). Then, the valve 11 is closed, the valve 14 is opened, and water is replenished from the pipe 10 to a height of _L1 (water filling step in FIG. 3), and then the process returns to the air scrubbing step. Although this method is effective for removing heavy crud, the amount of drainage per operation is small (L ₁ in Figure 2).
Therefore, it is necessary to repeat the steps _of air scrubbing, rapid draining, and water filling about 10 to 30 times, making the process complicated. Figure 3 is for explaining a method that is an improvement on the method shown in Figure 1 and drains water from an intermediate water collection device after backwashing. 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, is a backwash process, and is a drain process from the intermediate water collection device . In the method shown in Figure 3, the air scrubbing process with the drain process is the same as the method shown in Figure 1, but in the backwashing process the backwash water introduced from pipe 7 is introduced to the height of L ₃ . After that, valves 11 and 14 are closed, valves 13 and 17 are opened, and pipe 9 is opened.
Backwash water existing above the intermediate water collection device is drained from the intermediate water collection device 15 and drain extraction pipe 16 by pumping air from the intermediate water collection device. This method requires less time to separate the crud and less waste liquid than the method shown in Figure 1, but
Removal of heavy crud is not as efficient as the method shown in FIG. FIG. 4 is a diagram for explaining a method that is an improvement on the method shown in FIG. 3, in which each symbol has the same meaning as the symbol shown in FIG. indicates the backwashing process, indicates the draining process from the intermediate water collection device, and indicates the water filling process. In the method shown in FIG. 4, in the backwashing process, the valve 14 is closed and the inside of the regeneration tower 1 is brought into a pressurized state by introducing backwash water, without exhausting through the pipe 10, and a certain pressure is reached. Then, the valve 17 is opened and this pressure is used to drain water from the intermediate water collecting device 15 and pipe 16 (step). Then, the valve 17 is closed, the valves 13 and 14 are opened, and while exhausting air from the pipe 9, make-up water is supplied through the pipe 14, and the steps 1 to 2 are repeated again. In the method shown in Figure 4, the backwash water is not exhausted when it is introduced, so even if the initial backwash flow rate is increased, the flow rate of the backwash water becomes extremely low as the pressure inside the column increases, and once the water is separated Even if the crud is heavy, it will be located below the intermediate water collection device and cannot be discharged. To avoid this, special consideration is required for the backwash water supply pump, which increases the equipment cost. With the conventional backwashing method described above, it is difficult to transport the backwash water upward to the top of the resin layer and further beyond the resin layer to the discharge outlet at the top of the tower or to the water collection device in the middle of the tower. For heavy crusts with large particle sizes, the method shown in FIG. 2 is preferred. [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) stopping the drainage and exhaust from the intermediate water collecting device and installing it above the intermediate water collecting device; This is a method for removing suspended matter in a packed bed, which is characterized by repeatedly carrying out both steps, including a step of only evacuation from an evacuation 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. The method of the present invention will be explained based on FIGS. 5 and 6. FIG. 5 shows the case where one series of intermediate water collection devices is used, and FIG. 6 shows the case where two series are used. Reference symbols 1 to 17 in FIG. 5 have the same meanings as those shown in FIG. 3, and in FIG.
Except for b indicating a valve, other symbols have the same meanings as those shown in FIG. In FIG. 5, the water level is drained to the level _L1 of the intermediate water collection device 15 by the drain step. Next, air scrubbing is performed while introducing air from the pipe 8 through the lower water collection device 5 and exhausting it from the upper water collection device 6 (step). The air scrubbing step removes the resin-entrained crud from the resin and atomizes large cruds. The process is a conventional method. The air-water scrubbing and intermediate water collection device cleaning steps of the present invention are then carried out. In the present invention, air and water are simultaneously introduced from the lower water collection device 5 while the intermediate water collection device 15
Basically, air and water are discharged through the valve 17 and the pipe 16, and the heavy crud with a high settling velocity is transported from the lower part of the resin layer to the intermediate water collection device by the upward flow of air and water at a high velocity. 15 and removed through a pipe 16. In the air-water scrubbing process shown in Figure 5,
Since the valves 13 and 14 are closed, there is no evacuation from the top of the column, so that the flow of water and air is always concentrated in the intermediate water collection device 15, from which it exits the system via the pipe 16. It is discharged. In normal backwashing using only water, when draining water from an intermediate water collection device, resin accumulates in the intermediate water collection device, making it difficult to drain the crud. However, in the case of the present invention, in which scrubbing is carried out by simultaneously introducing water and air, the resin layer, especially its surface layer, is shaken violently, so even if resin is deposited in the intermediate water collecting device, the deposited resin layer will be removed immediately. The intermediate water collection device is always used as a “surface” for drainage and exhaust.
As a result of the experiment, it was confirmed that there is no problem in ejecting crud since the information is updated. The air flow rate from the lower water collection device is usually LV50~100m/h, which is used in the air scrubbing process.
A smaller LV of 15 to 50 m/h is appropriate, and the water flow rate is preferably LV of 5 to 15 m/h. In the method of the present invention, transportation and removal of crud is carried out not only by water but also by air,
The water flow rate does not need to be as high as in conventional backwashing. Furthermore, to explain in detail the removal status of crud,
Water and air are discharged from the lower half of the cross-section of the pipe of the intermediate water collection device, the majority of which is water. On the other hand, air is mainly exhausted from the upper half of the tube's cross section. Furthermore, the surface layer of the resin layer may exhibit bumping movements due to scrubbing, and at this time a phenomenon is observed in which the resin gradually accumulates on the upper half of the cross section of the tube. This phenomenon becomes larger as the air flow rate increases from LV50 to 100m/h, but even under the design conditions of the intermediate water collection device normally used,
There are no problems with air evacuation between 30 m/h and 30 m/h. In other words, in the lower half of the cross section of the pipe, the "surface" for drainage and exhaust has been updated by the developed resin layer itself, whereas in the upper half, there is no problem with the discharge of water and air during the process. The resin will accumulate little by little. Experiments have also shown that in the water-air scrubbing process, crud is concentrated in a region approximately 100 to 300 mm from the surface of the developed resin layer. Therefore, a water-air scrubbing process was carried out for a certain period of time (3 to 10 minutes) in order to efficiently remove crud from this area and to prevent resin from accumulating in the upper half of the pipe cross-section of the intermediate water collector. The rear valve 17 is closed to stop drainage and exhaust from the intermediate water collection device, and the valve 14 is opened to only exhaust air from the upper water collection device 6 and pipe 10 at the top of the tower, and the developed resin layer is transferred to the intermediate water collection device. by carrying out a cleaning step of the intermediate water collection device which is raised to a height of 100 to 300 mm (L ₂ position), then closing valve 14, opening valve 17 and carrying out another water-air scrubbing step. , 100 to the difference between L ₂ and L ₁ in Figure 5
This is to drain the area where 300mm of crud is concentrated. By repeating the steps (-) as necessary, the crud can be efficiently removed and the resin can be prevented from accumulating in the intermediate water collecting device. In this way, in the air-water scrubbing process, water is continuously collected from the lower water collection device 5.
Because air is introduced, heavy crud with large particle sizes that exist at the bottom of the resin layer and are difficult to remove in normal water backwashing are always transported to the top of the resin layer, in other words, in the middle, by the upward flow of air and water. The water is transported to the water collection device 15 and efficiently removed. Figure 6 shows the case where two intermediate water collection systems are provided, and the conditions are higher flow velocity than in the case of Figure 5, water flow rate LV6~25m/h, air flow rate LV30~
Can be used at 70m/h. When running at such a high flow rate, a large amount of resin will accumulate in the intermediate water collection device, but since there are two series of intermediate water collection devices and they are used alternately, one series can perform exhaust and drainage. Even though a large amount of resin has accumulated in one series, the resin accumulated in the other series has been loosened and the "surface" has been updated to be sufficient for drainage and exhaust, making it fully usable. Therefore, the air-water scrubbing step shown in FIG. 5 is performed more effectively and the time required for this step is reduced accordingly. That is, in FIG. 6, the valve 17a is opened and the pipe 16a is drained from the intermediate water collecting device 15a.
When air and water are being discharged through the intermediate water collecting device 15-b, the resin layer concentrated on one intermediate water collecting device 15-b is loosened, and when it becomes difficult for crud to come out from the intermediate water collecting device 15-a, simply switch the valve, i.e. 17a is closed and 17b is opened to discharge air and water from 15-b. It is more effective to remove crud if the switching time is short, about every 3 to 5 minutes. The intermediate water collection devices 15, 15a, and 15b used in Figures 5 and 6 can be simply a single pipe like the freeboard drain used in the conventional mixed bed system, which corresponds to 35 to 60 mesh. Those with a saran net etc. installed, or 200 ~
A water collection pipe with a 400μm slit will suffice. The present invention will be explained in detail below based on the drawings. First, FIG. 5, which uses one series of intermediate water collection devices, will be explained. The drain step and air scrubbing step are the same as the conventional method, and water is drained (step) to a height of 250 to 400 mm from the surface of the resin layer 3, followed by air scrubbing. The air flow rate at this time is LV50-100m/h, and the air pressure is 2-3Kgf/ ^cm2 . Next, the air-water scrubbing step of the present invention is started, and the air inflow valve 12 and sluicing water inflow valve 11 are opened from the lower water collection device 5, and the drain valve 17 of the intermediate water collection device 15 is opened to remove air and water. The water is introduced into the regeneration tower 1 from the pipes 8 and 7 through the lower water collection device 5, and is scrubbed with air and water while being drained and exhausted from the intermediate water collection device 15. At this time, no exhaust is performed from the top of the tower.
The air flow rate should be lower than the flow rate during air scrubbing, about LV15 to 50 m/h, but depending on the degree of contamination of the target resin, the properties of the cladding of the resin layer, the type of resin, etc. The flow rate of air in each step of and may be adjusted as appropriate. The flow rate of sluicing water is approximately LV3~15m/h. When carrying out the process, air and water are discharged only from the intermediate water collection device, so some resin accumulates around the intermediate water collection device, but since air is introduced, the surface layer of resin layer 3 is Because of the considerable undulation, the resin that has been deposited is broken down one after another, and the deposited part is the upper half of the pipe cross section of the intermediate water collection device 15, as mentioned above, and the amount is small, causing problems in terms of drainage and exhaust. There is very little that will happen. However, after carrying out the process for safely and securely discharging the crud for 3 to 10 minutes, the drain valve 14 of the upper water collecting device 6 is opened, and the drain valve 1 of the intermediate water collecting device 15 is opened.
Step 7 is closed and the process moves to the cleaning process of the intermediate water collecting device. During the process, sluicing water and air continue to be introduced from the lower water collection device, and the water level in the tower rises. Therefore, the surface layer of the resin layer 3 is higher than the position of the intermediate water collection device 15. The purpose of this step is to loosen the resin accumulated in the intermediate water collecting device 15, concentrate the crud in the upper part of the developing resin layer, and efficiently discharge the crud when repeating the next step. The difference between L ₂ and L ₁ is 100 ~
300 mm is sufficient, and the process may take a short time of 1 to 5 minutes. Then return to the air-water scrubbing step again. Repeat the process 3 to 10 times as necessary. After the final step, the valve 12 of the air introduction pipe 8 is closed, and only the backwash water is passed through the lower water collection device to carry out backwashing, which also serves as a water filling step, and the crud removal operation is completed. Next, the case shown in FIG. 6 in which two lines of intermediate water collection devices of the present invention are provided will be explained. , the draining process and air scrubbing process are the same as shown in FIG. In the air-water scrubbing step, the air inlet valve 12 and sluicing water inlet valve 11 of the lower water collecting device 5 are opened, and air and sluicing water are introduced at the same flow rate as described with reference to FIG. Then, the drain valve 17-a of the intermediate water collection device 15-a is opened for 3 to 5 minutes to drain and exhaust water from the pipe 16a, and when it becomes difficult for crud to come out, close the drain valve 17-a.
The drain valve 17-b of the two intermediate water collection devices 15-b is opened. 17-a and 17-b every few minutes like this
Opens and closes to efficiently discharge air and water, that is, exhaust the cladding. The intermediate water collection devices 15-a and 15-b may be set at a height of 200 to 500 mm above the surface layer of the settled resin layer 2. The setting positions of 15-a and 15-b may be at the same height, or may be set at different heights. When creating a height difference, 15-a is set at a position 200 to 300 mm from the surface layer of the resin layer 2. In other words, air scrubbing is performed to separate the crud from the resin and make the crud finer, thereby concentrating the resin slurry. Decide on the position so that it is in the correct position. The other 15-b is installed 300 to 500 mm from the surface of the resin layer 2 and above 15-a to increase the expansion rate of the resin layer so that the crud can be well discharged during air-water scrubbing. It is preferable to Then, if necessary, the process is repeated, and finally, normal backwashing is performed, which also serves as a water filling process, to complete the crud removal operation. Next, Table 1 shows the difference in effectiveness between the conventional method shown in FIGS. 1 and 2 and the method of the present invention shown in FIGS. 5 and 6.

[Table] The values in Table 1 are the total for both regeneration towers.
Table 1 shows the results when water is passed through a thermal power plant during normal operation for 30 consecutive days and then transferred from the desalination tower to the regeneration tower, and the cation resin is removed in the cation regeneration tower and the anion resin is removed in the anion regeneration tower. This shows the results. In the case of the method of the present invention, the cleaning time, the amount of cleaning waste water, and the amount of air are significantly reduced. Also, after these washings, when both resins were mixed and transferred to the desalination tower, the iron concentration in the resin transfer water was the first.
The conventional method shown in the figure is 35 ppm (as Fe), while the conventional method shown in Fig. 2 and the method of the present invention shown in Figs. 5 and 6 are 5 ppm.
(As Fe) It was as follows. From the above results, the method of the present invention can reduce the amount of water in a shorter time than the conventional method.
It can be seen that crud can be removed by changing the amount of air, and the crud removal rate is also good. The present invention has the same crud removal rate as the conventional method shown in Fig. 2, which is said to be effective in removing the heaviest crud, and the operation method is simpler and the amount of air used is smaller. The effect is significant.

[Brief explanation of drawings]

1, 2, 3 and 4 are drawings for explaining the conventional method, and FIGS. 5 and 6 are drawings for explaining the method of the present invention. 1... Regeneration tower, 5... Lower water collection device, 6... Upper water collection device, 15, 15a, 15b... Intermediate water collection device.

Claims (1)

[Scope of Claims] 1 While scrubbing is performed while simultaneously introducing air and water from the lower part of the packed bed, (1) the filling material provided on the surface layer of the packed bed being expanded by the scrubbing is not allowed to pass through; , a step of draining and exhausting water from an intermediate water collection device having a structure that allows only suspended matter to pass; A method for removing suspended matter in a packed bed, characterized by repeatedly carrying out both steps, including a step of only exhausting air from an exhaust device. 2. The method for removing suspended matter according to claim 1, wherein two lines of intermediate water collection devices are provided, and drainage and exhaust are carried out alternately from each line.