JPH02303507A - Method and device for operating ceramics filter - Google Patents

Abstract

PURPOSE:To sufficiently obtain the effect on restoring the treating capacity by backwashing by means of passing fluid in parallel with the surface of the ceramics filter in the flow passage on the side of the liquid to be treated of the ceramics filter right after back washing and operating the filter by a once-through system. CONSTITUTION:The liquid to be treated in a tank 3 is introduced, through a valve 28, a storage tank 30 for the liquid to be treated, a valve 29, a gas-liquid mixer 31, and a valve 6, to the flow passage on the side of the liquid to be treated by the ceramics filter 1 in a housing container 2 by a pump 4 to filter the whole volume of the liquid and the filtrate is discharged to a discharge piping 15 in the once-through system. When the resistance of the filtering of the filter 1 increases, the valve 6 is closed to pressurize a filtrate storage tank 25 and valves 8, 21 are opened to back wash the filter. The back washing water is discharged to a discharge piping 22. The valve 8 is closed after the back washing and the tank 30 is pressurized in the closed state of the valve 23, 28, 6, 32. The valve 23 is then opened and the water to be treated is introduced through the valves 29, 24, 23 to the flow passage on the side of the liquid to be treated by the filter 1. The water is discharged to the piping 22. As a result, the effect of restoring the treating capacity by the back washing is sufficiently obtd.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is useful for removing or concentrating suspended solids in a liquid in the food industry, pharmaceutical industry, atomic crab industry, etc. The present invention relates to a widely used ceramic filter operating method and a ceramic filter device used therein.

(Conventional technology) Ceramic filters made of inorganic compounds such as alumina and silica have excellent strength, heat resistance, and corrosion resistance, and are therefore used in the food and pharmaceutical industries.

It is widely used in fields such as atomic crab industry.

Ceramic filters come in a variety of shapes and operate in a variety of ways, but as the filtration time elapses, solids to be treated are captured on the filter surface.

As a result, the filtration performance gradually decreases, and the resistance when passing through the filter increases, the filtration differential pressure rises, and the treatment flow rate decreases, making it impossible to obtain a predetermined treatment capacity.

Therefore, it becomes necessary to clean the filter to restore processing performance.

Conventionally, filters are cleaned by washing or backwashing (flowing in the opposite direction to the filtration method) with permeate, clean water, or gas, but depending on the type of solids trapped or deposited on the filter surface, Since there are cases where treatment performance is not fully restored by this washing or backwashing alone, the chemical solution has been selected depending on the type of solid material.

An example of an operating method using a conventional ceramic filter will be explained with reference to the system diagram shown in FIG.

The liquid to be treated containing suspended solids in the liquid to be treated tank 3 is
Liquid supply piping 11.13. The liquid is guided to the ceramic filter storage container 2 through the valve 6, flows through the flow path inside the tube of the ceramic filter 1, returns to the liquid to be treated tank 3 through the valve 7 and the circulation piping 14, and is circulated again along the same route.

In the ceramic filter 1 , so-called cross-flow filtration is performed in which a portion of the liquid to be treated passes through the filter in a direction perpendicular to the flow in the flow path inside the tube, and is discharged to the filtrate discharge pipe 15 .

When the liquid to be treated is circulated in this manner, the suspended solids in the liquid to be treated are gradually concentrated. By opening the valve 9, the concentrated liquid is discharged out of the system through the pipe 16. When the concentrated liquid is discharged, the liquid to be treated tank 3 is connected to the pipe 17. New liquid to be treated is supplied via valve 10.

In the cross-flow filtration described above, since the flow direction of the filtrate passing through the filter and the flow direction of the liquid to be treated are different, it has the advantage of suppressing the deposition of solids on the filter surface. It is characterized by a long backwash interval.

What governs the processing performance of cross-flow filtration is the flow rate of the circulating flow, and the higher the flow rate, the larger the processing flow rate and the longer the backwash interval.

Therefore, in order to continue more efficient operation over a long period of time in a ceramic filter operated in a cross-flow type, it is necessary to operate the filter under conditions where the circulation flow rate of the liquid to be treated is increased.

(Problem to be Solved by the Invention) However, if the circulation flow rate of the liquid to be treated is increased in this way, the pump for circulating the liquid to be treated must have a high capacity, and the piping diameter of the circulation line must also be increased. Must. Furthermore, since the pump generates heat, cooling equipment is also required to remove the heat. Due to these factors, there is a problem that the device becomes large-scale.

In contrast to this cross-flow type, there is a so-called once-through type filtration process in which all the liquid to be treated that is supplied to the filter passes through the filter.

This method has the advantage of making the device more compact, but the backwashing interval becomes shorter due to the deposition of solids on the filter surface, and therefore the backwashing frequency increases. If the efficiency is not approximately 100%, the filtration performance will deteriorate rapidly. However, with conventional backwashing in which the filtrate flows in the opposite direction to the filtration process, a sufficient backwashing effect cannot be obtained, making it difficult to put the once-through method into practical use.

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for operating a ceramic filter that operates in a once-through manner and can sufficiently recover the processing capacity through backwashing, and an apparatus therefor. It's about doing.

[Structure of the invention] (Means and effects for solving the problem) The present invention filters the liquid to be treated in a once-through method, and when the filtration pressure increases, backwashing is performed to recover the filtration performance. A method of operating a ceramic filter in which the ceramic filter is repeatedly subjected to filtration treatment after backwashing is characterized in that immediately after backwashing, a fluid is caused to flow parallel to the surface of the ceramic filter in the flow path on the liquid-to-be-treated side of the ceramic filter. Regarding driving methods.

Furthermore, the present invention provides a device for use in the above-mentioned operating method, including:
A processing liquid tank, a ceramic filter storage container that houses a ceramic filter and is equipped with a filtrate discharge pipe and a backwash water discharge pipe, and the liquid to be treated tank and the storage container are connected to store the liquid to be treated. The present invention relates to a ceramic filter device comprising a pipe leading to a container, characterized in that a pressurized liquid tank is disposed upstream of the storage container.

In the ceramic filter device of the present invention, the pressurized liquid tank is installed upstream of the ceramic filter storage container, so immediately after backwashing the ceramic filter, the pressurized liquid tank supplies liquid to the ceramic filter to be treated at a high speed. The filter surface can be effectively cleaned by flowing parallel to the surface of the filter in the liquid side channel. Furthermore, in the ceramic filter device of the present invention, if a gas-liquid mixer connected to the gas introduction pipe is installed downstream of the pressurized liquid tank,
Air and other gases are introduced through the gas introduction pipe, mixed with gas and liquid by the gas-liquid mixer, and the gas-liquid mixed flow is passed through the flow path on the liquid to be treated side of the filter, so that the function of the ceramic filter can be recovered more effectively. be able to. Since these treatments are performed only immediately after backwashing, there is no need to increase the pump capacity, and no cooling device is required to remove heat generated from the pump. In addition, the piping only needs to be made thicker in the parts related to these processes. Therefore, according to the present invention, a once-through ceramic filter can be operated with compact equipment and with excellent backwashing effects. .

(Example) Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram showing one embodiment of the ceramic filter device of the present invention. Note that the same parts as those in FIG. 5 already explained will be described with the same reference numerals. however,
Since the apparatus of the system diagram shown in this figure performs filtration processing in a once-through method, the circulation pipe 14 from the ceramic filter to the liquid to be treated tank 3 shown in FIG. 5 does not exist.

In FIG. 1, a ceramic filter 1 is fixed in a storage container 2. As shown in FIG. On the inflow side of the liquid to be treated in the storage container 2,
There is a liquid supply pipe 13.11 having a valve 6 and a pump 4 and connected to the liquid tank 3, and a backwash water discharge pipe 22 having a valve 21. On the processing liquid inflow side, there is a ceramic filter cleaning pipe 25 which is equipped with valves 23 and 24 and is branched from the liquid supply pipe. Also, a valve 8 is attached to the side of the storage container 2. A filtrate discharge pipe 15 including a filtrate storage tank 25 is connected. Further, between the valve 6 of the liquid supply pipe I3 and the pump 4, a pressurizing pipe 27 equipped with a valve 26 is provided.
and a liquid storage tank 30 with a valve 211.29 is connected thereto. Further, a gas-liquid mixer 31 is installed between the valve 29 and the valve 6 of the liquid supply pipe 13, and an air supply pipe 33 equipped with a valve 32 is connected to the gas-liquid mixer 31.

Next, a method of operating the above device will be explained.

In the once-through method, the liquid to be treated in the liquid to be treated tank 3 is pumped by the pump 4 to the valve 28. To-be-treated liquid storage tank 38, valve 29
．． Gas-liquid mixer 31. The liquid is guided through the valve 6 to the flow path on the liquid-to-be-treated side of the ceramic filter 1 in the storage container 2, and the entire amount is filtered. The filtrate is discharged to discharge pipe I5. When suspended solids adhere to the surface of the ceramic filter on the liquid to be treated side and filtration resistance increases, close the valve 6 to stop the liquid supply.
The filtrate storage tank 25 is pressurized and the valve 8. The valve 21 is opened, the filtrate stored in the filtrate storage tank is flowed in the opposite direction to the filtration treatment method to perform backwashing, and the backwash water is discharged to the discharge pipe 22.

After backwashing, close valve 8, and then valve 23.2g, 6.3
2 is closed, the liquid to be treated storage tank 30 is pressurized, and then,
The valve 23 is opened, and the liquid to be treated stored in the liquid to be treated storage tank 3o is transferred to the valve 29. After passing through the gas-liquid mixer 31, the valve 24. It flows into a ceramic filter cleaning piping 25 equipped with a valve 23 and is led to a flow path on the liquid-to-be-treated side of the ceramic filter 1.

As a result, the surface of the ceramic filter 1 on the liquid-to-be-treated side is cleaned, and the cleaned liquid is discharged to the backwash water discharge pipe 22. At this time, after opening the valve 32 and supplying air through the air supply pipe 33 and sufficiently mixing it with the liquid to be treated in the gas-liquid mixer 31, the liquid to be treated is placed on the side of the liquid to be treated in the ceramic filter 1 in a gas-liquid two-phase flow state. It can also be guided into a flow path.

After backwashing and washing are completed, perform the filtration process again.

Figure 2 shows that the ceramic filter device of this embodiment has the following properties:
It shows the change in filtration differential pressure after backwashing and washing when filtration processing and backwashing and washing are repeated. Shown here is backwash pressure 6
Kg/cm2, amount of backwash water per unit filtration area 0.
After backwashing under the conditions of 0.02 m'/m2, the liquid to be treated was pressurized in the storage tank and the liquid to be treated was flowed for 30 seconds at a flow rate of 5 m/s in the flow path on the liquid to be treated side of the ceramic filter. As a comparative example, the results (broken line) of a conventional backwashing method without a cleaning step after backwashing under the same backwashing conditions are shown.

As is clear from the figure, the filtration differential pressure does not recover sufficiently even after backwashing in the conventional backwashing method that does not have a washing step, but it recovers well when a washing step is added after backwashing according to the present invention. I understand that.

In addition, in Figure 3, with the ceramic filter device of this example, the backwash conditions are fixed at a backwash pressure of 6 kg/cm2 and a backwash water amount per unit filtration area of 0.02 m3/m', and after backwashing, the ceramic filter The results are shown when the flow rate of the liquid to be treated flowing through the liquid to be treated side channel is 1 m/s. The broken line is the same as in Fig. 2 (results of the conventional backwashing method).

From this figure, it can be seen that the cleaning effect is not sufficient when the flow rate of the fluid flowing into the treated liquid side flow path of the ceramic filter after backwashing is 1 m/s. It was found from a separate experiment that the flow rate in this cleaning step was required to be 3 m/s or more.

In addition, Fig. 3 shows that the flow rate is 1 in the cleaning process after backwashing.
The results are shown in which air was supplied from the air supply piping to the flow of the liquid to be treated corresponding to m/s, and the gas-liquid two-phase flow was caused to flow through the flow path on the liquid to be treated side of the ceramic filter. The air supply flow rate in this case is set so that the wall shear stress in a gas-liquid two-phase flow is equivalent to the wall shear stress at a flow rate of 3 m/s in the case of a single-phase liquid flow.
The flow rate was 3.5 times that of the liquid equivalent to 1 m/s.

As is clear from the figure, in the cleaning process after backwashing, the wall shear stress in the gas-liquid two-phase flow is 3 m /
It can be seen that a sufficient cleaning effect can be obtained and the filtration differential pressure can be well recovered by supplying air to the liquid flow to a value equivalent to s.

Next, FIG. 4 shows a system diagram of another embodiment of the apparatus of the present invention.

In this embodiment, the liquid to be treated storage tank 3 of the embodiment shown in FIG.
Instead of the valve 41.0, the cleaning water storage tank 4G to which the pressurized pipe 44 with the valve 42 is connected is connected to the valve 41.0. It is connected to the liquid supply pipe 13 via a pipe 43.

In this example, the same filtration process as in the previous example was performed,
When suspended solids adhere to the surface of the ceramic filter on the liquid-to-be-treated side and the filtration resistance increases, backwashing is performed in the same way. After backwashing, valve 8 is closed, and valves 7.28. 6.32 is closed, pressurize the cleaning water storage tank 40 filled with cleaning water in advance, then open the valve 23 and transfer the cleaning water stored in the cleaning water storage tank 40 to the gas-liquid mixer 3I. and valve 24
．． It is guided to the flow path on the liquid-to-be-treated side of the ceramic filter 1 through a ceramic filter cleaning piping 25 equipped with a valve 23, and the surface of the liquid-to-be-treated side of the ceramic filter 1 is cleaned, and the washed liquid is transferred to the backwash water discharge piping. Discharge at 22. At this time, valve 3
2 is opened, air is supplied through the air supply pipe 33, and after sufficiently mixing with the cleaning water in the gas-liquid mixer 31, the air is introduced into the flow path on the liquid-to-be-treated side of the ceramic filter 1 in a gas-liquid two-phase flow state. You can also do it.

In this example as well, backwashing and cleaning effects similar to those of the previous example were obtained.

As described above, the method and device of the present invention have a high backwashing effect, so they can be used to inspect and replace filter elements, especially when applied to the filtration treatment of suspensions containing solids with high specific radioactivity concentration in nuclear facilities. Radiation exposure associated with this work can be kept low.

[Effects of the Invention] As explained above, according to the operating method of the present invention and the device of the present invention, filtration processing using a once-through method for ceramic filters can be performed using a compact device and with an excellent functional recovery effect due to backwashing. It can be implemented efficiently. In particular, when the present invention is applied in the field of nuclear energy, the radioactivity decontamination effect is significant.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an apparatus according to an embodiment of the present invention. FIGS. 2 and 3 are diagrams showing the recovery status of the filtration differential pressure after backwashing and washing in the embodiment shown in FIG. 1. FIG. 4 is a system diagram showing a device according to another embodiment of the present invention, and FIG. 5 is a system diagram showing a conventional ceramic filter device. 1... Ceramic filter 2... Ceramic filter storage container 3... Liquid to be treated tank 4... Pump 13... Liquid supply pipe 15... Filtration discharge pipe 22... Backwash water discharge pipe 25...Filtrate storage tank 25...Cleaning piping 30...Liquid storage tank 31...Gas-liquid mixer 33...Air supply piping 40...Cleaning water storage tank Agent Patent attorney (8733) ) Yoshiaki Inomata (and 1 others)
given name)

Claims (3)

[Claims] (1) In the operation method of ceramic filters, the liquid to be treated is filtered in a once-through method, and when the filtration differential pressure increases, backwashing is performed to restore the filtration performance, and the filtration process is repeated again. 1. A method of operating a ceramic filter, comprising: flowing a fluid parallel to the surface of the ceramic filter in a flow path on the liquid-to-be-treated side of the ceramic filter immediately after (2) A liquid to be treated tank, a ceramic filter storage container containing a ceramic filter and equipped with a filtrate discharge pipe and a backwash water discharge pipe, and a liquid to be treated by connecting the liquid to be treated tank and the storage container. What is claimed is: 1. A ceramic filter device comprising piping for guiding liquid to the storage container, characterized in that a pressurized liquid tank is disposed upstream of the storage container. (3) The ceramic filter device according to claim 2, wherein a gas-liquid mixer connected to the gas introduction pipe is installed downstream of the pressurized liquid tank.