JPH0316161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a moving bed continuous filter using an air lift pump to transfer soiled material to a material washing section.

This type of moving bed continuous filtration device was developed in Japanese Patent Application Publication No. 53
Those disclosed in JP-A-111062 and JP-A-53-92369 are known. This filtration device uses an air lift pump to lift dirty material along with air bubbles through the air lift pipe and transfer it to the material cleaning section, and the material cleaned in the material washing section is configured to flow down to the upper surface of the material layer. It is something. That is, the above-mentioned
As shown in the figure, a material layer such as sand is filled in a tank 1 to form a material layer, which extends from the bottom of the tank 1 to the material cleaning section 3 located at the top center of the tank 1. An extending air lift pump 8 is provided, and a plurality of inflow pipes 6 branched from the raw water introduction pipe 5 connected to the lower part of the tank 1 are provided above. 7 are arranged. On the other hand, in the air lift pump 8, a ring-shaped air chamber A is provided at the lower part of the air lift pipe 4 through a plurality of air supply holes 4a, and an air blowing pipe 9 is connected to this air chamber A. be.

In such a filter, raw water is passed through the raw water introduction pipe 5.
, flows out from the upper end of the inflow pipe 6 , hits the raw water dispersion umbrella 7 , is diffused in all directions, and is filtered out by passing through the material layer. On the other hand, air is continuously blown from the air blowing pipe 9 connected to the lower part of the air lift layer 4 through the air chamber A and the air supply hole 4a, so that the material 2 inside the air lift pipe 4 is bubbled due to the air lift effect. At the same time, it rises inside the air lift pipe 4. Due to the operation of the air lift pump 8, the material 2 that is contaminated with dirt in the lower part of the tank 1 enters the lower part of the air lift pipe 4, passes through the air lift pipe 4, and passes through the material washing section 3.
The material 2 transferred to and cleaned in the material cleaning section 3 flows down onto the material layer to form a new material layer.

Conventionally, in a moving bed continuous filtration device that uses an air lift pump 8 to transfer the material 2,
The air supplied to operate the air lift pump 8 is increased by the weight of the mixture of material 2 and water in the air lift pipe 4, and in order to raise the air bubbles, the pressure exerted on the air blowing part by this weight is lower than the pressure applied to the air blowing part. It is said that high pressure air is required.
For example, the height of tank 1 is approximately 5100mm and the diameter is approximately 2530mm.
In a moving bed continuous strainer filled with material 2 to a depth of approximately 3200 mm and the inner diameter of the air lift tube 4 being 25 to 32 mm, the air lift pump 8 must be driven in order to ensure smooth startup and stable operation of the strainer. It is said that compressed air at a constant pressure of about 3 kg/cm ³ is always required as air for use. For this reason, as shown in FIG. 1, as an air source for driving the air lift pump 8,
Directly operated air lift pump 8 with high pressure and small air supply per unit power
Using a compressor 10 with a capacity capable of ^continuously driving the The air is blown into the air lift pump 8 through the air pump 14 and through the air blowing pipe 9 with the flow rate adjusted by the air flow rate control valve 15.

The compressor 10 used as a device for supplying air at such a pressure is less efficient than a blower that supplies air at a lower pressure, and because it increases the air pressure more than necessary, it consumes a large amount of energy per unit amount of air. However, there is a drawback that the operating cost per amount of water treated by the moving bed continuous filtration device is high.

In the above-mentioned moving bed continuous filtration device, overwater and washing wastewater are continuously discharged, so there is no need for storage tanks for raw water, overwater, and washing wastewater that were required in the case of conventional semi-continuous filtration devices. This has the advantage that equipment costs are lower than conventional semi-continuous filters. However, as the amount of water to be treated increases, in the case of a conventional semi-continuous filter, the equipment cost of each storage tank accounts for a smaller proportion of the total equipment cost, so the above advantages become relatively smaller. On the other hand, as the amount of water to be treated increases, the drawback of the above-mentioned moving bed continuous filtration device, such as the increase in operating cost, cannot be ignored, and it is difficult to apply the above-mentioned moving bed type continuous filtration device to equipment with a large amount of water to be treated. It has become an obstacle.

In addition, at the time of starting the above-mentioned moving bed continuous filtration device, as shown in FIG. Since the air lift pipe 4 is clogged with material 2, it must be discharged to the material cleaning section 3. However, after the operation has been stopped for a long period of time, the material 2 in the air lift pipe 4 forms a lump, and the above operation has the disadvantage that the air lift pump 8 cannot be started smoothly.

By the way, the inventors of the present invention have discovered that the opportunity to supply high-pressure air of approximately 3 kg/cm ³ or more to the moving bed continuous evaporator is due to the material 2 that has stopped and accumulated in the air lift pipe 4. , due to the weight of the material 2, the frictional force between the material 2 and the airlift pipe 4, the frictional force between the materials 2, and the positional water head difference over the length of the airlift pipe. 8, and the necessary supply time is within a few seconds, and at other times (after transitioning to normal operation), the liquid column of the mixture of material 2 and water in the air lift pipe 4. The apparent weight of the air becomes lighter due to the inclusion of air bubbles, so if we continue to supply low-pressure air at a pressure equal to the water pressure at the point where the air blowing pipe 9 connects to the air lift pipe 4 plus the pressure loss due to piping, etc. I found that it is good. If this moving bed continuous filtration device is used for in-house water in a sewage treatment plant, the air lift pump 8 will be started once at the time of installation of the main filtration device or maintenance performed every few months. Therefore, it has been found that it is possible to accumulate high-pressure air, which is used relatively infrequently, within an appropriate period of time, for example, in an air tank, and use the accumulated air at the required time. .

The present invention has been made based on the above-mentioned circumstances, and after starting the air lift pump by supplying high-pressure gas, the present invention supplies gas at a pressure lower than the high-pressure gas to continue the operation of the air lift pump. Therefore, it is an object of the present invention to provide a method of operating a moving bed continuous filtration unit that can significantly reduce operating costs and facilitate starting of an air lift pump.

Hereinafter, the present invention will be specifically explained with reference to the drawings. In the following description, the same reference numerals are used for parts common to those in FIG. 1, and the description will be omitted.

FIG. 4 shows an embodiment of the apparatus for carrying out the method of the present invention, and shows a case where an air source with a predetermined pressure already exists or a new air source with a predetermined pressure is installed. . Symbol B in the figure is a low-pressure air source. When newly installing this low-pressure air source B, use a blower that has a lower pressure than a compressor, has a large air supply amount per unit power, and has a low operating cost. . And low pressure air source B
are pressure gauge 12, low pressure air valve 16, air flow meter 1
4. Connected to the air blowing pipe 9 via an air flow control valve 15 and a check valve 17. In addition, the symbol C in the figure
is a high-pressure air source, and this high-pressure air source C is connected to the air blowing pipe 9 via an air tank 18, a pressure gauge 12, and a high-pressure air valve 19. Since the high-pressure air source C only needs to store the required amount of air in the air tank 18 over a long period of time before starting the air lift pump 8, a small-capacity compressor may be used. Furthermore, for example, the height of tank 1 is approximately 5100 m and the diameter is approximately 2530 mm.
In a moving bed continuous evaporator filled with material 2 to a depth of about 3200 mm, the length of the air lift tube is about 5000 mm, and the inner diameter is about 25 to 32 mm, the pressure of the low-pressure air is
0.5~0.6Kg/ ^cm3 , and the pressure of high pressure air is usually 3~9.9
Kg/ ^cm3 .

Next, the case where the method of the present invention is implemented using the apparatus shown in FIG. 4 will be explained.

First, before starting air lift pump 8, air tank 1
8 is sufficiently supplied with high pressure air from the high pressure air source C and stored under pressure. In this state, when starting the air lift pump 8, the high pressure air valve 19 is opened and at the same time (or before the high pressure air valve 19 is closed) the low pressure air valve 16 is opened to start supplying air. At this time, the pressure inside the air blowing pipe 9 is
Because it increases due to the high pressure air supplied from 8,
The check valve 17 closes and prevents high pressure air from flowing back into the low pressure air source B. Then, when high-pressure air is supplied, the material 2 stuck in the air lift tube 4 causes a bumping phenomenon in which it ejects all at once, and the flow in the air lift tube 4 starts, causing the material 2 in the air lift tube 4 to rise. Extravasation begins. After supplying high-pressure air for about 0.1 to 10 seconds, when the high-pressure air valve 19 is closed, the air pressure inside the air blowing pipe 9 decreases, and when the pressure becomes lower than the low-pressure air pressure, the check valve 17 opens. Supply of low pressure air is started. As a result, the supply of air to the air lift pipe 4 is continued,
The material 2 is continuously transferred by the air lift pump 8. Further, the amount of material 2 transferred is adjusted by adjusting the amount of air supplied to the air lift pump 8, and the amount of air is adjusted by adjusting the opening degree of the air flow rate control valve 15.
This is done in place of adjusting the pressure loss in the valve, but when using a conventional device, during normal operation, for example, the pressure at the inlet of the air flow control valve 15 is about 3 Kg/cm ³ and the pressure at the outlet is about 0.4. ~0.5Kg/ ^cm3
Therefore, the pressure loss that must be provided by the air flow control valve 15 is as large as approximately 2.6 to 2.5 kg, so the relationship between the operation amount of the air flow control valve 15 and the air flow rate is linearly proportional, which is easy to operate. Although the air flow rate changes greatly due to a slight difference in the opening degree of the air flow control valve 15, it is difficult to finely adjust the air flow rate. At times, the inlet pressure of the air flow control valve is about 0.5Kg/cm ³ and the outlet pressure is about 0.4~0.5
Kg/cm ³ , and the pressure loss caused by the air flow control valve 15 is as small as 0.1 to 0 Kg/cm ³ , and the relationship between the air flow control valve 15 and the air flow rate is approximately linearly proportional, at least within its operable range. Since the air flow rate is followed in a similar relationship, fine adjustment of the air flow rate is easy.

Moreover, FIG. 5 shows an example in which there are high pressure and low pressure air sources, but the high pressure air source C is higher than a predetermined pressure, and the low pressure air source B is lower than the predetermined pressure. , low pressure air is boosted by booster blower 2
0 to a predetermined pressure, and the high pressure air is reduced to a predetermined pressure by a pressure reducing valve 11 before being supplied.

Furthermore, FIG. 6 shows that during normal operation, the amount of air blown into the air lift pipe 4 decreases due to some reason such as blockage of the air lift pipe 4 or the air blowing pipe 9, and the operating state of the air lift pump 8 becomes unstable. In order to prevent this from happening and to operate the air lift pump 8 more reliably, the flow switch 21 is
is installed in the air blowing pipe 9, so that when the amount of air blown into the air lift pipe 4 decreases for some reason, the decrease in the air flow rate for the air lift pump is detected and the air lift pump 8 is immediately activated.
By automatically opening the high-pressure air valve 19 in the same way as at startup, high-pressure air is supplied and the cause of piping blockage is eliminated. And for a short time (0.1-10 seconds)
After supplying high pressure air, the high pressure air valve 19 is automatically closed, normal operation is resumed, and the operation of the air lift pump 8 is restored. Note that the flow switch 21 may be provided between the air flow control valve 15 and the check valve 17, and if the flow rate is checked with the air flow meter 14 shown in FIG. 6 and the flow rate has decreased, the high pressure The air valve 19 may be configured to open automatically.

Furthermore, the reason why the high-pressure air supply time is set to a short time of 0.1 to 10 seconds is because if the high-pressure air is supplied for a longer period of time, the amount of supplied air will be excessive and the air will not be able to escape upward through the air lift pipe 4. First, a phenomenon occurs in which the air flows backward into the material layer from the lower end of the air lift tube 4, and if this air cannot be completely collected by the bubble collecting umbrella 22, the air bubbles stray inside the material layer and locally fluidize. This is because overwatering causes phenomena such as deterioration of water quality. Furthermore, the blower used as the low-pressure air reducer B in this embodiment is generally more efficient than a compressor, and because it compresses air only up to the required pressure, it consumes less energy per unit amount of air. Furthermore, in this embodiment, air was used as the supply gas, but other gases may be used depending on the case.

As explained above, the present invention uses high-pressure air, which consumes a large amount of energy per unit amount of air, only for a short time during startup, and uses low-pressure air, which consumes less energy per unit amount of air, during normal operation. As a result, operating costs can be significantly reduced. For example, a moving bed continuous filtration vessel with an excess area of 5 ^m2
When operating 10 units, the conventional operating method requires at least one 15KW compressor, but with the operating method of the present invention, only one 5.5KW blower is required, reducing the consumption of high-pressure air to drive the air lift pump. Since the energy is so small that it can be ignored, operating costs can be reduced by 1/2 to 1/3. In addition, sand filters have been increasingly used in recent years to supply in-house water for sewage treatment plants that use the activated sludge method, and aeration blowers are already installed in the facilities. If you have a low-pressure air source with sufficient air supply and an appropriate pressure, you can use this to supply low-pressure air, and there is no need to install a new low-pressure air source, reducing equipment costs. Can be reduced. Furthermore, when the air lift pump is started, high-pressure air is blown into the material that is stuck inside the air lift pipe, causing a bumping phenomenon that causes the material to blow out all at once and being discharged outside the air lift pipe. Since the air lift pump can be fluidized advantageously and low-pressure air can be continuously supplied, it has excellent effects such as being able to smoothly operate the air lift pump.

[Brief explanation of the drawing]

Figures 1 to 3 show a conventional moving bed continuous filter, in which Figure 1 is an overall configuration diagram, Figure 2 is a sectional view of the air lift pump, and Figure 3 is the same as in Figure 2.
4 is an overall configuration diagram showing an example of a moving bed continuous filter used for carrying out the present invention, and FIG. 5 is a cross-sectional view taken along the line. FIG. 6 is an overall configuration diagram showing an example of the air lift pump for more reliable operation. 2...Material, 3...Material cleaning section, 8...Air lift pump, B...Low pressure air source, C...High pressure air source.

Claims (1)

[Claims] 1. In the operating method of a moving bed continuous filtration unit configured to transfer the material at the bottom of the material bed to the material washing section using an air lift pump, and to cause the material washed in this material washing section to flow down to the top of the material bed, high pressure After the air lift pump is started by supplying gas, the operation of the air lift pump is continued by continuously supplying gas at a pressure lower than the pressure of the high pressure gas supplied at the time of starting the air lift pump. 1. A method of operating a moving bed continuous filtration device, characterized in that the transfer of .