DE3836530C2 - - Google Patents

Description

The present invention relates to a method for loading driven a backwashable filter according to the generic term of Claim 1.

Such a process is essentially based on the US PS 44 82 461 known. Backwash filters are used in many Areas of process engineering. For an optimal To get filter operation from time to time Backwashing is required, the pressure is before and after Filter media constantly measured with sensors, the current Pressure difference determined - e.g. B. with a conventional Process computer of a suitable design - and as the main control variable  used for the initiation and duration of the backwash process. It is e.g. B. a target differential pressure in the computer entered, depending on the type of filter used, the Filter medium and the medium to be filtered depends on the e.g. B. the computer constantly with the current differential pressure is compared. The calculator includes e.g. B. also an operating time counter. There are time intervals for the target filtration time and time intervals for the specified rinsing time, these predetermined time intervals also on the type and condition of the filter, the filter medium and the medium to be filtered. In normal operation the backwashing process takes place after the target filtration time has elapsed initiated, which lasts over the target rinsing time. At the Backwashing process usually drops the current differential pressure below the specified target differential pressure. After that The target filtration time begins to run again.

As a security measure in the known method provided that regardless of the expiration of the target filtration time the backwash sequence is interrupted and the backwash process is initiated if the specified target differential pressure is reached. A faster one Rise in current differential pressure than in Normal operation indicates strong contamination of the filtering medium, clogging of the filter medium or the like  there.

There may be mechanical damage or deficient clamping of the filter medium e.g. B. a crack or hole in a filter cloth or filter fabric, which means that proper filtering can no longer be guaranteed is steady. This can be done with the known method during of the company cannot be determined, as such Damage leads to a drop in the differential pressure, what the computer sees as a sign of normal operation becomes. However, the result is an at least partial flow of the filter with unfiltered medium and accordingly adverse consequences for the downstream process stages. From the English abstract of JP 57- 91 714 A2 it is known to indicate damage of the filter medium exceeds the target filtration time Specify time interval and a comparison to carry out with the filtration time. Is the target filtration time exceeded by the current filtration time, occurs at the end of the specified time interval Display. In the method according to US-PS 44 82 461 can however, this measure does not grab because of the target filtration time is never exceeded.

The object of the present invention is a method to operate a filter that creates damage of the filter medium during operation and without Opening of the filter reveals.

This task is accomplished by a method with the characteristics of the characterizing part of claim 1 solved.

Operation and advantages of the invention are in verbin described with a drawing.

The only drawing represents a schematic block slide grams to the inventive method.

Before going to the details shown in the drawing is discussed in more detail, it should be assumed that each of the described features for themselves or in connection with Merk paint the claims of essential importance to the invention can be.

A medium to be filtered flows through a filter medium, e.g. B. a filter fabric. The filter medium keeps solid pollution cleaning back in the medium and continues striding towards. The contaminants adhere to the side of the filter medium facing the medium to be filtered. The actual fil is in the highly schematic figure ter not shown, since it belongs to the prior art. The Filter means can take on different geometric shapes, it can e.g. B. in one or more parallel planes or be arranged on one or more cylinder jackets.

During the backwash process, the direction of flow in the fil ter vice versa, d. H. a rinsing liquid, e.g. B. filtered Medium, rinses the back of the filter medium solid impurities deposited by a not posed arrangement of lines and valves from the fil ter out.

Pressure sensors measure the pressure P ₁ and P ₂ on both sides of the filter medium during operation and conduct appropriate signals via amplification electronics in accordance with the current pressure difference ΔP to a computer and a memory. The measuring and processing devices used for signals correspond to the prior art and will not be explained further.

In a known comparison circuit, the computer constantly compares the current pressure difference ΔP with a predetermined target differential pressure ΔP ₁ . In a further comparison circuit, the computer also compares the running operating time t with a manually entered target filtration time t ₁ .

Upon reaching the condition .DELTA.P .DELTA.P equal to _1, or t is equal to t _1, whichever condition first exists, the computer outputs a signal "flushing" te to a not shown well-control unit, which initiates the backwash.

Also during the backwash process, as with the filter process, the differential pressure ΔP and the current Operating time t processed in terms of data in the computer.

During the backwashing process, the computer compares ΔP with P ₁ and t with a manually entered target rinsing time t ₂ . After t _{2 has} elapsed and the condition ΔP less than ΔP _{1 has been reached} , the computer sends a signal "flushing finished" to the control unit, which interrupts the backwashing process.

The number of signals given to the control unit and the number of states ΔP equal to ΔP ₁ are counted in a counter and stored in a memory.

After the target rinsing time t _{2 has} elapsed and the condition ΔP less than ΔP _{1 has not been reached} , the backwashing process is continued until the current differential pressure ΔP is less than the predetermined target differential pressure ΔP ₁ . This process is called continuous rinsing.

Furthermore, a time t _{3 is entered} manually in the computer. If the operating time t equals t ₃ , the computer sends a query signal to the memory with the content of whether ΔP _{1 has been reached} during the entered time. If the feedback from the memory to the computer is negative, the computer blocks the backwashing process for an inputable control interval t ₄ or for a selectable number n ₁ of target filtration times t ₁ . If the operating time t equal to t ₄ or equal to n ₁ × t _{1 is} reached, a query signal with the content of whether ΔP _{1 has been} reached is sent to the memory. If this feedback is also negative, the computer sends a "tissue control" signal to the display device. If the feedback is positive, the system switches to normal operation and the cycle starts again with the entered time t ₃ .

As an alternative to t ₃ , a predetermined number of backwashing processes can be entered into the computer.

Through this automatic check during operation indicates that the current differential pressure ΔP is smaller is than it corresponds to normal operation. That leaves the Presumption that damage to the filter medium before lies and triggers a check of the filter. Here defective and / or damaged filter media puts.

A further embodiment of the invention provides that a second target differential pressure ΔP _{2 can be} entered into the computer. ΔP ₂ is higher than ΔP ₁ . If ΔP is equal to ΔP ₂ , the computer gives a "lock" signal to the control unit, which blocks the filtering or backwashing process. At the same time, the computer sends a "filter fault" signal to the display device. An operational fault is recognized from this signal in connection with the recognizable blocked flushing process and appropriate measures are initiated.

Another embodiment of the invention provides that  those shown above, controlled by the computer operations with the automatic system switched off by manually operating controls on the computer can be triggered when z. B. in trial operation or is desired for other reasons.

Further embodiments of the invention provide that the display device is an LC display on which both the number as well as the type of operations or states will be shown. This means that monitoring is always possible maintenance personnel possible. The ad is free program mbare, z. B. "Motor fault" can also be displayed, if an engine required to operate the filter is off falls.

In addition to the pressure signal, there is another configuration device of the invention a temperature sensor in the medium or after the filter medium before (not shown) the one Temperature signal to the computer there in the display device is displayed as a temperature value. Of course it is without further possible, a further comparison circuit in the Calculator in which the temperature value with a manually entered target temperature is compared. At Exceeding the target temperature can, for. B. "Overtemperature" be displayed on the display device.  

With the method it is thus possible to operate a Filters automatically monitor, malfunctions in time to recognize and damage caused by flowing pollution prevent largely.

Claims (7)

1. Method for operating a backwashable filter, in which a filtering process and a backwashing process alternate in succession, in which a current differential pressure is continuously determined in a computer from the pressures on both sides of a filter medium and is compared with a predetermined target differential pressure ΔP ₁ , in which the backwashing process is initiated when the current differential pressure exceeds the predetermined target differential pressure ΔP ₁ and ends after a predetermined target flushing time, if the current differential pressure falls below the predetermined target differential pressure ΔP ₁ , and in which the backwashing process also occurs after a predetermined target filtration time is initiated, even if the predetermined target differential pressure .DELTA.P ₁ has not yet been reached, characterized in that during the successive filtering and backwashing processes, reaching the predetermined target differential pressure .DELTA.P ₁ in a memory f It is held that after a time t ₃ which can be input into the computer, if the predetermined setpoint pressure difference ΔP _{1 has} not been recorded in the memory in this given time t ₃ , the backwashing process is blocked for a control interval t _{4 which} can also be input into the computer, and that, even if the duration of the control interval t₄ the predetermined target differential pressure ΔP₁ has not been recorded in the memory, a display "tissue control" is derived. 2. The method according to claim 1, characterized in that alternatively to the time entered in the computer t₃ one Number of backwashing operations is entered. 3. The method according to claim 1 or 2, characterized net that alternatively to the control interval t₄ a Number of filter operations is entered. 4. The method according to any one of claims 1 to 3, characterized records, by a further target differential pressure ΔP₂, which is higher than ΔP₁ and when it is exceeded the backwash process is blocked. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the automatic control processes by manual control processes can be replaced. 6. The method according to any one of claims 1 to 5, characterized ge indicates that there is also a temperature sensor in the filter is provided which is a display signal via the computer delivers. 7. The method according to any one of claims 1 to 6, characterized ge indicates that the type and number of operating states be shown on an LC display.