JPS62134200A - Measuring method for dehydrated cake separatability of dehydrator - Google Patents

Abstract

PURPOSE:To surely measure the separatability by measuring the separatability quantitavely based on the pressure loss or permeability. CONSTITUTION:The dehydrator has the lower filter cloth 2 and upper filter cloth 1 and after performing the gravitational dehydration by feeding a sludge on the lower filter cloth 2 a squeeze dehydration is performed by the squeezing part which pinches the upper and lower filter cloth 1, 2, and the dehydrated cake C is separated by the scraper 5a, 5b which are arranged in opposition to the upper and lower roll 3, 4. At the cake discharging part thereof, suction means 6, 7 are provided on the back face of the upper filter cloth 1 and lower filter cloth 2. The pressure loss of the filter cloth due to the suction by the suction means 6, 7 is detected by pressure detector 8, 9. This signal is converted into an electrical signal by convertor 10 and computing element 11 measures the separating of the dehydrated cake on this filter cloth based on the pressure loss thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for measuring the peelability of a dehydrated cake in a dehydrator such as a belt press dehydrator that uses a filter cloth to perform dewatering.

[Prior Art] Belt press type dehydrators are commonly used for dewatering sludge and the like. In this dewatering machine, after passing the sludge through gravity, the sludge is squeezed between two upper and lower filter cloths while gradually increasing the pressure, and then the dewatered cake is peeled off naturally or with a scraper if necessary. .

However, if the releasability decreases, the SS recovery rate will deteriorate and various operational problems will occur. In other words, the SS recovery rate is expressed as the ratio of the amount of solids recovered as a dehydrated cake to the amount of solids input, but the amount of unrecovered solids is 85 minutes in the saturated solution and 85 minutes from the filter cloth. It consists of leakage and unpublished gISS remaining on the filter cloth after peeling the cake. Among these, when dewatering is usually good, the SS recovery rate is mostly controlled by the unpeeled 55 minutes remaining on the filter cloth, so if the cake peelability deteriorates, the SS recovery rate will be directly affected. causing a decline. Furthermore, if the filter cloth is not washed sufficiently, unpeeled cake may adhere to the filter cloth due to the fact that the filter cloth is used repeatedly. ! If the cloth becomes clogged, the dewatering capacity will be reduced, and in the case of a belt press type dehydrator, the gravity filtration characteristics will deteriorate, leading to operational problems such as side leaks.

Therefore, the peelability of the dehydrated cake is an important factor in the operational management of the dehydrator.

[Problems to be Solved by the Invention] However, conventionally, there is no method for quantitatively measuring the peelability of dehydrated cake, and an operator visually observes the filter cloth at the cake discharge part of the dehydrator to determine whether it has been peeled off or not. The dehydrator operation was changed based on the adhesion of cake. However, this requires the operator to be constantly or periodically stuck to the cake discharge section, which is not rational and may lead to erroneous judgments, making it impossible to carry out optimal operation.

Therefore, an object of the present invention is to provide a method that can quantitatively measure the peelability of a dehydrated cake.

[Means for Solving the Problems] In order to solve the above problems, the first invention provides at least one of the upper and lower filter cloths after discharging the cake in the cake discharge section of the dehydrator. A suction means is used to draw air from the back side of the filter cloth, the pressure loss is measured, and the removability of the dehydrated cake of the filter cloth is measured based on the pressure loss.

In addition, the second invention is such that in the cake discharge section of the dehydrator, after the cake has been discharged by the scraper, suction is carried out from at least the back side of the lower filter cloth among the upper and lower filter cloths by the suction means, and the pressure loss or this pressure is reduced. In addition to calculating the air permeability converted from the loss, the pressure loss or air permeability of the filter cloth in an undehydrated state is measured in advance as a blank value, and the pressure loss or air permeability after the dehydration and the pressure loss in the undehydrated state are calculated in advance. Alternatively, the ratio to the air permeability is used as an index of cake releasability.

[Function] In the present invention, in order to quantitatively measure the releasability of the dehydrated cake, the releasability is measured by sucking air from the back side of the filter cloth and determining the pressure loss or air permeability converted from this. . The pressure drop or air permeability of a filter cloth in its unused (undehydrated) state is always constant. However, after dehydration,
Cake buildup reduces pressure drop or air permeability.

Its value depends on the cake coverage. Therefore, measuring pressure loss or air permeability is an effective means.

Moreover, the peelability depends on the material, thickness, weaving method, air permeability, etc. of the filter cloth. Therefore, if we ignore these factors and judge only by pressure drop or air permeability, then i!
! When the fabric is renewed, or after a long period of operation, the sludge gets stuck deep inside and cannot be finally removed.
If the condition of the filter cloth changes, we will not be able to respond. Therefore, if we define the ratio of the pressure loss or air permeability after cake peeling to the pressure loss or air permeability of the filter cloth in an undehydrated state as the pressure loss or air permeability maintenance rate, and measure the peelability based on this, we can measure the peelability of the original filter. Even if the properties change due to the type of fabric or long-term operation, it can be easily dealt with.

[Specific examples of the invention] The present invention will be explained in more detail below.

Figures 1 and 2 show how the peelability of a dehydrated cake is measured in a belt press type dehydrator.

The dewatering machine has a lower filter cloth 2 and an upper filter cloth 1, and after sludge is supplied onto the lower filter cloth 2 and dewatered by gravity, it is compressed and dehydrated by a pressing section that sandwiches the upper and lower filter cloths 1 and 2. After this is done, the scrapers 5A, 5 are placed opposite the upper and lower rolls 3.4.
The dehydrated cake C is peeled off by B. The scrapers 5A and 5B may not be used if the peelability is good.

Now, in the present invention, air intake means 6 and 7 are provided for sucking air from the back surface of the lower filter cloth 2 and the lower filter cloth 1.

The suction means 6, 7 preferably each have a filter cloth 1.2.
It is preferable to provide a plurality of a pieces (three pieces in the illustrated example) in the width direction.

As shown in FIGS. 3 and 4, as the suction means 6 and 7, a lattice grid 21 is provided in a box 20 that opens to the back surfaces of the filter cloths 1 and 2, and a grid 21 is provided to the bottom wall of the box 20. A spacer 22 is provided, a sealing material 23 made of a flexible material such as rubber is provided at the opening of the box 20 to prevent air leakage, and a blower 25 is provided for sucking air through communication passages 24A and 24B. It can be configured by

On the other hand, pressure detection points 8.9 are provided in the communication paths 24A and 24B to detect pressure. The signals at the pressure detection points 8 and 9 are converted into electrical signals by the converter 10, and the pressure loss (air permeability) and/or the pressure loss (air permeability) maintenance rate described below are calculated by the calculator 11. The results are recorded on the recorder 12 and are used as control signals for controlling the amount of washing water and other operational management. The amount of washing water can be controlled by controlling the opening/closing or borrowing of a control valve (not shown) attached to the washing water supply piping of the washing device 13, 14. Here, preferably, a plurality of washing water nozzles are provided in the width direction of the filter cloths 1 and 2 corresponding to the groups of air intake means 6 and 7, and the amount of washing water is individually controlled.

Here, the dimensions of the box 20 are preferably approximately 3 to 5 cm in width (il! fabric flow direction) and 10 to 15 cm in length. When inhaling, inhale by each suction means at the same time, intermittently 2 to 3 times per hour, 10 to 10 times per hour.
It is best to do this for about 20 seconds.

Thus, the pressure drop or air permeability of the filter cloth is
It is clearly related to the degree of contamination. If the pressure loss is high, the filter cloth is dirty and the releasability is poor, and if the pressure loss is low, the releasability is good. Further, the relationship between pressure loss and air permeability is shown in FIG. Therefore 1. Cleaning device 1 depending on pressure loss or ventilation
3, 14 can be controlled.

As a result, the amount of washing water, which was conventionally set to a constant approximately 1001/rtrin for the total of upper and lower filter cloths per inch of filter cloth, can be reduced to the minimum amount of water necessary for washing, and a reduction in the amount of washing water can be achieved.

By the way, as mentioned above, pressure loss or air permeability varies depending on the type of filter cloth and the surrounding environment, and therefore cannot be used as an absolute index of releasability. Therefore, after the start of operation or before operation, the pressure loss or air permeability is measured with the filter cloth in an undehydrated state, and this is taken as a blank value Sa, and the ratio of this to the pressure loss or air permeability sb after cake peeling is It is preferable to use the pressure loss or air permeability maintenance rate F as an index of releasability.

In reality, after the start of operation, the time until the cake is discharged is set in advance using a timer, the pressure loss or air permeability Sa during that time is memorized, and it is later determined from sb given as the measured value of cake peeling. Bye.

Further, as the pressure loss or air permeability maintenance rate, the average value of signals from a plurality of pressure gauges provided in the width direction, or the maximum value thereof may be used.

Note that the above example is an example in which pressure loss or air permeability is detected for both the upper and lower filter cloths, but the issue of releasability is
Since it is mainly the lower filter cloth, it is sufficient to measure at least the lower filter cloth. Furthermore, to control the peelability, it is necessary to control the tension pressure of the filter cloth (increasing the pressure will improve the peelability), controlling the filter cloth movement speed (lowering the speed will improve the peelability), or adding a chemical solution. This can be done by controlling the amount, etc.

[Effects of the Invention] As described above, according to the present invention, releasability is quantitatively measured based on pressure loss or air permeability.
Removability can be reliably measured without relying on operator observation.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a cake discharge section of a dehydrator showing an embodiment of the method of the present invention, Fig. 2 is an example of the arrangement of a luminometer with respect to a lower filter cloth, Fig. 3 is a sectional view of the suction means, and Fig. 4 The figure is the plan view,
FIG. 5 is a correlation diagram between pressure loss and air permeability. 1. Upper filter cloth 2. Lower filter cloth 6.
．． 7. ,,,Suction means 8,9. ,,,pressure detection point 13,14. ,,,Cleaning device Fig. 1 Fig. 2

Claims (2)

[Claims] (1) In the cake discharge section of the dehydrator, after the cake has been discharged, suction is taken from at least the back side of the lower filter cloth among the upper and lower filter cloths, the pressure loss is measured, and the pressure loss is calculated based on the pressure loss. A method for measuring dehydrated cake releasability of a dehydrator, the method comprising measuring the dehydrated cake releasability of the filter cloth. (2) In the cake discharge section of the dehydrator, after the cake has been discharged by the scraper, suction is taken from at least the back side of the lower filter cloth among the upper and lower filter cloths by the suction means, and the resulting pressure loss is reduced.
Alternatively, the air permeability converted from this pressure loss is determined, and the pressure loss or air permeability of the filter cloth in the undehydrated state is measured in advance as a blank value, and the pressure loss or air permeability after the dehydration and the undehydrated state are measured in advance. 1. A method for measuring dehydrated cake peelability of a dehydrator, characterized in that the ratio of the pressure loss or air permeability of