JPH0211282B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of operating a pressure filter. Generally, a pressure filter is operated by the following method. That is, as shown in Fig. 1, a stock solution supply pump (hereinafter referred to as pump) 1 having a control mechanism for stock solution supply pressure is continuously driven, and a check valve 2 and a pressure indicating regulator (PIC) 3 are attached. A high-pressure single method in which the stock solution is fed under pressure to a pressure filter (hereinafter referred to as a filter) 5 via a stock solution supply pipe (hereinafter referred to as a supply pipe) 4, and the pump 1 is controlled by the PIC 3 to adjust the supply pressure; As shown in FIG. 2, an ordinary pressurizing pump 6 supplies the stock solution to the filter 5 through the supply pipe 4 equipped with a check valve 2, and a branch pipe 7 attached to the supply pipe 4 The stock solution is introduced into the pressure tank 8 whose bottom is attached to the tip of the pump, and when the pressure in the pressure tank 8 reaches the upper limit, the pressure switch (PS) 9 is activated to stop the pump 6.
Thereafter, the stock solution is continuously sent to the filter 5 by the pressure accumulation in the pressurized tank 8. When the pressure in the pressure tank 8 reaches a predetermined lower limit pressure, the pump 6 starts again and filters the filter 5.
And the stock solution is pumped into the pressure tank 8. There is a pressure tank constant pressure method in which filtration is performed by repeating the above operations. In the figure, 10 is a level switch (LS) that interlocks the valve 12 at the liquid level in the pressure tank 8, 11 is a small compressor, 12 is an automatic air supply valve, and 13 is an air check valve. In the above method, the former has the advantage of being able to supply the stock solution at a fairly high pressure depending on the selection of the pump 1; however, during filtration, the operation of the pump 1 must be continued because it is necessary to maintain the supply pressure of the stock solution. There are certain drawbacks. In the latter case, once the pressure in the pressure tank 8 is set at the upper limit, the pump 6 can be stopped until the pressure drops below the set lower limit, so the pump 6 operates intermittently, and its operating time is 1/5 of the former. It has the advantage of being able to be shortened to ~1/4. However, operating the pressure tank 8 within the set pressure range at a relatively high pressure increases the manufacturing cost of the pressure tank 8. In addition, high pressure increases the risk of compressing air, and has the disadvantage of requiring maintenance engineers with advanced technical knowledge to be assigned. This method was unsuitable for economical filtration. By the way, in recent years, water treatment has come to be performed on most wastewater, and finally the discharged sludge is dehydrated. Dehydration of these sludges requires relatively high pressure, so pressure filters are often used. In addition, these sludges are usually in the form of sludge, and in the early stages of filtration, they are filtered at relatively low pressure to prevent leakage from the contact surface of the filter plate of the pressure filtration machine and to reduce the filtration resistance of the initially formed cake. However, as the cake layer on the filter cloth surface becomes thicker and the filtration resistance increases, it becomes necessary to filter at high pressure. For the sludge-like sludge filtration, two-stage filtration using low pressure and high pressure is reasonable. In view of the above circumstances, the present invention aims to provide a method for operating a pressure filter that can be operated easily and economically over a wide range of pressures from low pressure to high pressure. It combines the operating methods of filters and eliminates the drawbacks of each. The method of the present invention will be explained below with reference to the drawings. FIG. 3 shows a pressure filtration apparatus for carrying out the method according to the present invention, and the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the explanation thereof will be omitted.
The branch pipe 7 that communicates the supply pipe 4 and the pressure tank 8 is provided with a pressure tank gate valve 14 that opens and closes the branch pipe 7. Pump 1 also has a built-in supply pressure control mechanism.
It is regulated by PIC3 and starts at the lower limit pressure of PS:9 and stops at the upper limit pressure. Further, the command for the pump 1 in PS:9 can be canceled. Also LS: 1
An interlock is provided in which the valve 12 is automatically opened or closed in response to the upper or lower limit of 0. Next, a method of operating the pressure filtration apparatus configured as described above will be explained. First, the upper and lower limits of PS: 9 and LS: 10 are set, and the pump is turned on and off according to the instructions of PS: 9. Open the pressure tank gate valve 14,
The pump 1 is started and the stock solution is supplied to the filter 5. In this case, the stock solution is introduced into the filter 5 and filtered, and is also introduced into the pressure tank 8 . Pressure tank 8
When the liquid level in the pressure tank 8 slightly exceeds the upper limit of LS10, the air supply valve 12 is opened to introduce air from the compressor 11, and when the liquid level in the pressure tank 8 reaches the set lower limit, the automatic air supply valve 12 is opened. stop. When the raw liquid is further pumped in this state, the liquid level in the pressure tank 8 gradually rises, and the air in the upper space of the pressure tank 8 is compressed and pressure-accumulated. Pressure tank 8
When the internal pressure reaches the set upper limit pressure of PS:9, the pump 1 is stopped, and thereafter the stock solution in the pressure tank 8 is supplied to the filter 5 by the pressure in the pressure tank 8, and filtration is continued. When the pressure in the pressure tank 8 reaches the set lower limit pressure of PS: 9, the pump 1 starts and pumps the stock solution into the pressure tank 8.
Press fit inside. By repeating such an operation for a certain period of time, filtration is performed at a pressure between the upper and lower limits of the set pressure of PS:9. Then, as the cake layer on the filter cloth gradually thickens, the filtration speed will drop rapidly, so the command to pump 1 from PS: 9 is canceled, the pressure tank gate valve 14 is closed at the same time, and pump 1 is turned on by the command from PIC 3. Drive. Following low-pressure filtration, the stock solution is PIC within the set high pressure range.
Pump 1 by the function of the stock solution supply pressure control mechanism of
is controlled and pressurized into the pressure filter 5. In the above, the upper limit pressure of PS: 9 is lower than the set pressure of PIC: 3, and after a certain period of time, the timer shifts from low pressure filtration to high pressure filtration so that pump 1 is operated under control according to the command of PIC: 3. It has become a mechanism like this. When performing low-pressure filtration as described above, economical operation can be achieved by intermittent pump operation, and when high-pressure filtration is required, it can be easily switched to high-pressure filtration by changing the time setting. This makes it possible to dewater sludge, etc., which has hitherto been impossible to filter efficiently, extremely efficiently and economically. For reference, a comparative example in which the same sludge was filtered is shown in the table below.

[Table] As shown above, it can be seen that dehydration is carried out well and that it is an energy-saving operation method.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams of equipment for explaining conventional operating methods. Figure 1 is a diagram of equipment that performs the high pressure single method, Figure 2 is a diagram of the equipment that performs the pressure tank constant pressure method, and Figure 2 is a diagram of the equipment that performs the high pressure single method. FIG. 3 is a diagram of an apparatus for carrying out the method of the invention. 1... Stock solution supply pump with built-in supply pressure control mechanism, 2... Check valve, 3... Pressure indication regulator (PIC), 4... Stock solution supply pipe, 5... Pressure filter,
6... Raw solution supply pump, 7... Branch pipe, 8... Pressure tank, 9... Pressure switch (PS), 10... Level switch (LS), 11... Bebicon, 12...
Air supply automatic valve, 13... Air check valve, 14...
Pressure tank gate valve.

Claims (1)

[Claims] 1. Connect the stock solution supply pipe connecting the pressure filter and the stock solution supply pump to the bottom of the pressure tank through a branch pipe,
The stock solution pumped by the stock solution supply pump is supplied to the pressure filtration machine and is also pressurized into the pressure tank. When the pressure in the pressure tank reaches a predetermined upper limit pressure, the stock solution supply pump is stopped and the pressure tank is closed. In the method of operating a pressure filter, the stock solution in the pressure tank is supplied to the pressure filter by accumulating pressure, and when the pressure in the pressure tank reaches a predetermined lower limit pressure, the stock solution supply pump is driven again. An opening/closing mechanism is provided in the communication section, and a pump capable of controlling the stock solution supply pressure is installed as the stock solution supply pump. When filtration is performed at a low pressure, the opening/closing mechanism of the communication section is opened and a pressure tank is installed, and the stock solution supply pump is turned on and off to pump the stock solution. A method for operating a pressure filter, characterized in that when supplying and filtering at a high pressure, the communicating portion is closed and the stock solution supply pump is continuously driven to supply the stock solution to the pressure filter.