JPH06229918A - Method and apparatus for measuring water content of dehydrated cake - Google Patents

Abstract

PURPOSE:To make it possible to measure the water content of dehydrated cake instantly with an infrared-ray moisture meter by decreasing the errors of the water content of the dehydrated cake of the sludge generated from sewage, human waste or an industrial waste-water treating facility. CONSTITUTION:An infrared-ray water moisture meter 2 and a color-difference meter 4 are arranged in the vicinity of the output port of dehydrated cake of a belt-press type dehydrating machine 1. The data of a calibration curve corresponding to the mixing ratio with respect to the mixed sludge of digestive sludge and raw sludge are stored beforehand. The color of the dehydrated cake S, which is discharged from a second filter cloth 12 at the outlet port of the dehydrated cake is measured with the color-difference meter 4. The absorbance of the dehydrated cake S is measured with the infrared-ray moisture meter 2. The calibration curve of the infrared-ray moisture meter 2 is set based on the value of the lightness L of the color of the dehydrated cake S measured with the color-difference meter 4 and the data of the calibrating curve. The absorbance of the dehydrated cake S, which is measured with the infrared-ray moisture meter 3, is converted into the water content with the set calibration curve.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the control of the dehydration process of dehydrating sludge generated from sewage, night soil or industrial wastewater treatment facilities with a belt press type dehydrator, and the post-treatment of dehydrated cake obtained in the dehydration process. The present invention relates to a method for measuring a water content of a dehydrated cake and an apparatus for measuring the water content of a dehydrated cake, which are related to the maintenance and management of the dehydrated cake using an infrared moisture meter.

[0002]

2. Description of the Related Art Conventionally, for example, when sludge is subjected to solid-liquid separation by a belt press type dehydrator, an appropriate amount of a polymer flocculant is added to the sludge to carry out a flocculation reaction, and then the flocculated sludge is run horizontally or almost horizontally. It is fed on the filter cloth for gravity dehydration, and the sludge sandwiched between the filter cloths is squeezed between a plurality of rolls and squeezed and dehydrated by applying the pressing force due to the tension pressure of the filter cloth. Compressed and dehydrated by applying a high pressing force by the tension of the pressure belt from the upper part of the sandwiched filter cloth, and the dehydrated cake is discharged through these dehydrating steps.

By the way, the amount of water contained in such a dehydrated cake, that is, the water content of the dehydrated cake has an important influence on the next process such as incineration or landfill disposal of the dehydrated cake. In other words, the amount of fuel used in incineration, the transportation cost in landfill disposal, and the volume of the disposal site are affected. Therefore, the dehydrated cake should have the minimum water content or the required water content for the maintenance of the incinerator. It was desired to be discharged at a rate.

Therefore, a means for measuring the water content of the dehydrated cake has been proposed. One example is a method in which a small amount of dehydrated cake is sampled, dried with a dryer adjusted to a constant temperature until a constant weight is obtained, and the weight difference before and after drying is measured to calculate the water content. Since this method requires a drying time of several hours or more, there is a drawback in that it is not possible to quickly control the dehydration process.

In another example, an infrared moisture meter is installed on a belt conveyor that conveys the dehydrated cake to an incinerator or a landfill, and the leveling mechanism adjusts the shape of the dehydrated cake on the belt conveyor to adjust the infrared radiation. There is a method of contactlessly measuring the moisture value with an infrared moisture meter while preventing the scattering of incident light and reflected light. Although this method has an advantage that a measured value can be obtained in real time, it has the following problems because it is an indirect measuring method based on the absorbance of infrared rays by moisture.

That is, in the case of sludge generated from sewage, night soil or industrial wastewater treatment facilities, several types of sludge are generated depending on the treatment process, and the amount of sludge sent to the dehydration treatment process differs depending on the type, and is the same. The amount of each type varies depending on the time. For this reason, the dehydrated cake obtained in the dehydration step often changes its properties all the time, and the difference in the properties of this dehydrated cake affects the absorbance of infrared rays, making it difficult to obtain correct measured values.

[0007]

SUMMARY OF THE INVENTION The present invention uses an infrared moisture meter in facilitating management of post-treatment of dehydrated cake of sludge generated from sewage, night soil or industrial wastewater treatment facilities or control of dehydration process. Therefore, it is an object to immediately measure the water content of the dehydrated cake and reduce the measurement error.

[0008]

Means for Solving the Problems The method for measuring the water content of a dehydrated cake of the present invention made to solve the above problems is to measure the water content of a dehydrated cake obtained by solid-liquid separation of sludge with an infrared moisture meter. A method for measuring the water content of a dehydrated cake to be measured, in which the information of the calibration curve of the infrared moisture meter for a plurality of types of dehydrated cakes having different properties is stored, and the color of the dehydrated cake that is the measurement object is measured by a color difference meter. Measured by, set the calibration curve of the infrared moisture meter based on the color information output by the color difference meter and the information of the calibration curve, in the infrared moisture meter the calibration curve is set in the measurement object It is characterized in that the water content of a dehydrated cake is measured.

The dehydration cake water content measuring device of the present invention comprises a color difference meter for measuring the color of the dehydration cake obtained by solid-liquid separation of sludge, and an infrared moisture meter for measuring the water content of the dehydration cake. , Storage means for storing information on the calibration curve of the infrared moisture meter for a plurality of types of dehydrated cakes having different properties, and color information output from the color difference meter and the calibration curve stored in the storage means. Calibration curve setting means for setting a calibration curve of the infrared moisture meter based on the information.

[0010]

According to the method for measuring the water content of the dehydrated cake or the apparatus for measuring the water content of the dehydrated cake of the present invention, the color of the dehydrated cake which is the object to be measured is measured by a color difference meter, and the color information output by the color difference meter is used. , The calibration curve of the infrared moisture meter is set based on the information of the calibration curve of the infrared moisture meter for multiple types of dehydrated cakes of different properties, and the dehydration that is the measurement object with the infrared moisture meter with this calibration curve set The water content of the cake is measured.

The calibration curve of the infrared moisture meter is a curve (or straight line) showing the correlation between the absorbance of infrared rays by the object to be measured and the measured water content. The infrared absorbance of the dehydrated cake correlates with the properties of the dehydrated cake. Further, as will be described later, the properties of the dehydrated cake correlate with the brightness of the color information obtained by the color difference meter. Therefore, an appropriate calibration curve in the infrared moisture meter can be set based on the brightness.

[0012]

EXAMPLE FIG. 1 is a schematic view showing an example in which the method for measuring the water content of a dehydrated cake and the apparatus for measuring the water content of a dehydrated cake of the present invention are applied to a belt press type dehydrator, and FIG. 2 is a dehydrated cake of the example. It is a block diagram of the water content measuring apparatus of.

The belt press type dehydrator 1 is provided with a liquid-permeable endless first filter cloth 11 and a second filter cloth 12.
The filter cloth 11 and the second filter cloth 12 are looped around a number of rollers and are tensioned by the filter cloth tensioning devices 13a and 13b. And the first filter cloth 1
The 1st and 2nd filter cloths 12 respectively run in the direction of the arrow of a figure, and perform the following dehydration process with respect to the sewage, human waste, or the sludge generated from an industrial wastewater treatment facility.

That is, the sludge and the coagulant are sufficiently mixed and reacted in the coagulation and mixing tank 14, and the coagulated sludge 10 is supplied onto the first filter cloth 11 in the natural dehydration section to relatively desorb the coagulated sludge. Easy moisture is dehydrated by gravity, and the desorbed liquid is received by the pan 15a and discharged to the outside. On the other hand, the first filter cloth 11 is reversed by the reversing roll 16a to drop the coagulated sludge 10 onto the second filter cloth 12 in the natural dehydration section, and the water that is relatively easy to be removed by this second filter cloth is dehydrated by gravity. , The desorbed liquid is received by the pan 15b and discharged to the outside.

After passing through the natural dehydration section for dehydrating water by the above gravity, the coagulated sludge is filtered by the first filter cloth 11 and the second filter cloth 12.
It is sandwiched by and is wound around a large number of rolls 16b, and is further squeezed and dehydrated by a squeeze and dewatering section by a pressure belt 17 to form a dehydrated cake S between the first filter cloth 11 and the second filter cloth 12.

Then, the first filter cloth 11 and the second filter cloth 12 are separated by the reversing rolls 16c and 16d, and then the first filter cloth 1
The first and second filter cloths 12 are washed with water by the filter cloth washing devices 18a and 18b, respectively, and fed toward the natural dehydration section.

In this embodiment, a belt press type dehydrator 1
An infrared moisture meter 2 is disposed at the outlet of the dehydrated cake while being held by the moving mechanism 3, and a color difference meter 4 is disposed in front of the infrared moisture meter 2. Then, the color of the dehydrated cake S discharged from the outlet of the dehydrated cake S is measured by the color difference meter 4 and the absorbance of the dehydrated cake S is measured by the infrared moisture meter 2.

As shown in FIG. 2, the color signal output from the color difference meter 4 and the absorbance signal output from the infrared moisture meter 2 are input to the data processing device 5 via the controllers 41 and 21, respectively. The data processing device 5 sets a calibration curve to be used in the infrared moisture meter 2 based on the color signal and the information stored in advance, and converts the absorbance signal into a water content signal based on the calibration curve. Output.

In this embodiment, the infrared moisture meter 2 is used.
Is held at a fixed distance from the second filter cloth 12 by the moving mechanism 3 near the outlet of the dehydrated cake, and the moving mechanism 3 keeps the second filter cloth 12 in the width direction (perpendicular to the running direction of the filter cloth). Direction).

FIG. 7 is a front view of the mounting portion of the infrared moisture meter 2 and the moving mechanism 3, FIG. 8 is a plan view thereof, and FIG. 9 is a side view thereof. The moving mechanism 3 is a pair of left and right L-shaped fixed arms 31.
It is fixed to the frame 1A at the outlet end of the dehydration cake of the belt press type dehydrator 1 by L and 31R, and is attached to the horizontal frame 32 that is stretched over the fixed arms 31L and 31R.
A parallel slide shaft 33 of a book is provided. The slide shaft 33 is mounted at a right angle (parallel to the reversing roll 16d) with respect to the traveling direction of the second filter cloth 12, and holds the moving block 34 slidably in the width direction of the second filter cloth 12.

Further, a motor 35 capable of rotating in the forward and reverse directions is arranged at one end of the upper portion of the horizontal frame 32, and a sprocket 36 is arranged at the other end thereof, and a drive sprocket 35a attached to the drive shaft of the motor 35. A chain 37 is hung between the sprocket 36 and the sprocket 36, and one position of the chain 37 is fixed to the moving block 34.

The infrared moisture meter 2 is fixed to the moving block 34 with its measuring head 2a directed toward the second filter cloth 12 and the reversing roll 16d. The cable 2b of the infrared moisture meter 2 is wound around a horizontal bar 38 laid in parallel with the horizontal frame 32, and its end is connected to the controller 21 of FIG.

With the above construction, the moving block 34 and the infrared moisture meter 2 are kept at a constant distance from the second filter cloth 12 by the drive of the motor 35, and the direction perpendicular to the traveling direction of the second filter cloth 12 is maintained. It will be moved back and forth. The motor 35
Is controlled by a motor controller (not shown), and limit blocks (not shown) mounted near both ends of the slide shaft 33 detect the moving block 34 to switch the moving direction.

The rotation speed of the motor 35 is controlled according to the operating speed of the belt press type dehydrator 1, and the infrared moisture meter 2 is reciprocally moved at a speed synchronized with the traveling speed of the second filter cloth 12. The water content (water content) of the dehydrated cake S on the second filter cloth 12 is measured by the water content meter 2.

In the vicinity of the dewatering cake outlet of the belt press type dewatering machine 1, the dewatering mechanism in the belt pressing type dewatering machine 1 (mechanism of squeezing dewatering unit) discharges the dewatered cake in a sheet form, so that The surface becomes smooth. The dewatering cake with a belt press type dewatering machine is one in which the coagulated sludge, which is dispersed almost evenly in the width direction of the filter cloth, is sandwiched between two filter cloths and is hung on a number of rolls for dewatering treatment. The surface is formed in a flat plate shape and discharged.

The filter cloth wound around the belt press type dehydrator is usually strained by an air cylinder, and has a structure capable of withstanding the sludge supply up to the stroke length limit of the cylinder. When sludge longer than the stroke length of the cylinder is supplied, the cushion limit of the cylinder is exceeded, and thereafter, the filter cloth is broken. Therefore, some measure is usually taken so that the height of the gravity dehydration unit falls within a certain range.

For this reason, the dewatering cake discharged from the belt press type dewatering machine has a flat surface and the thickness thereof is slightly different depending on the properties of the sludge to be dewatered. It is within ± 3 mm.

Therefore, according to this embodiment, not only the surface of the dehydrated cake is smoothed but also the distance between the infrared moisture meter 2 and the surface of the dehydrated cake is kept substantially constant. A measurement error of the moisture value by the infrared moisture meter 2 is reduced. Further, since the non-contact type infrared moisture meter is used, the water content of the dehydrated cake can be instantly measured.

By the way, in the belt press type dewatering machine, as the length of the filter cloth used in the width direction becomes larger, the dehydration property in the width direction, that is, the water content of the dehydrated cake becomes more distributed due to the dewatering mechanism. . For example, as shown in FIG. 10 as an example, the measurement position in the width direction and the measurement result of the water content for a belt press type dehydrator with a filter cloth width of 3 m show that there is a difference in the dehydration property between the center of the filter cloth and the vicinity of both ends. Occurs.

However, according to the apparatus of the above-mentioned embodiment, since the infrared moisture meter 2 can reciprocate in the width direction of the filter cloth (second filter cloth 12), dehydration in the width direction of this filter cloth is possible. By obtaining the average water content of the cake, the actual water content of the dehydrated cake can be grasped.

Further, according to the apparatus of the above-mentioned embodiment, the controller controls the speed of the motor 35 even when the running speed of the filter cloth in the belt press type dewatering machine 1 is changed, and the filter of the infrared moisture meter 2 is filtered. Since the moving speed of the cloth in the width direction can be synchronized with the speed of the filter cloth, it becomes easy to obtain the average value in the width direction with respect to the running distance of the filter cloth.

In describing the setting of the calibration curve in the examples, first, the relationship between the sludge and the calibration curve of the infrared moisture meter will be described. Figure 4 shows the measurement of sludge at a certain sewage treatment plant using an infrared moisture meter, and the absorbance and absolute dry moisture value of the infrared moisture meter (actual water content)
It is a figure which shows an example of the measurement result of.

The measurement conditions were a sample (A) containing only digested sludge,
Regarding the sample (B), which is a mixed sludge of digested sludge and raw sludge, and the sample (C) containing only raw sludge, the operating conditions of the belt press type dehydrator 1 (sludge supply amount, coagulant addition rate, coagulation mixing tank rotation speed, It was set by changing the filter cloth speed, etc.) to discharge a dehydrated cake having a low water content to a high water content, and the absorbance and the absolute dry water value were sampled. In the figure, the same sample with different marks has different measurement dates and operating conditions of the belt press type dehydrator, but the type of sludge and the mixing ratio are constant.

As can be seen from FIG. 4, there is a high correlation between the absorbance and the absolute dry water value in each sample. For reference, the above correlation equations are summarized as follows. (A): y _A = 67.18 + 72.72 x _A , γ = 0.
88 (B): y _B = 65.75 + 65.66x _B , γ = 0.
91 (C): y _C = 64.55 + 55.79 x _C , γ = 0.
93 where x _A , x _B and x _C are the absorbance, y _A , y _B and y _C
Is the absolute dry water value, and γ is the correlation coefficient.

Thus, since each sample has a high correlation, these equations can be used as a calibration curve for each sample. However, when the samples are different, that is, when the properties of the dehydrated cake are different, the calibration curves deviate. It can be seen that Further, it is understood that the deviation of the calibration curve appears as the contact piece (0th order coefficient) and the slope (1st order coefficient) of the calibration curve become smaller as the proportion of raw sludge increases.

On the other hand, the present inventor measured the color of the dehydrated cake using a color difference meter and analyzed the organic matter content (VTS), which is one of the measured component indexes of the dehydrated cake, and found the relationship between them. As a result of investigation, the results shown in FIGS. 5 and 6 were obtained.

FIG. 5 shows the case of digested sludge, and FIG. 6 shows an example of the case where raw sludge is mixed into the digested sludge and the content ratio of the digested sludge gradually decreases to finally produce only raw sludge. . In the figure, the horizontal axis is the sampling point (time), and the vertical axis is the rate of change of VTS when the first measurement value is 1.
In addition, the lightness L of the three elements L, a ^* , and b ^* measured by the color difference meter
The values are shown together.

As shown in FIGS. 5 and 6, in the case of digested sludge, VTS and L value show almost no change, but as shown in FIG. 6, the ratio of the raw sludge gradually begins to be mixed with the raw sludge in the digested sludge. It can be seen that the VTS value increases and the L value also increases at a similar rate as the value increases. That is, it was found that the mixing ratio of digested sludge and raw sludge can be detected by reading the L value by a color difference meter.

Therefore, in the above embodiment, in the data processing device 5 (FIG. 2), dehydration is performed based on the lightness L value of the color signal output from the color difference meter 4 and the calibration curve data stored in the memory 5a. A calibration curve suitable for the properties of the cake is set, and the absorbance signal output from the infrared moisture meter 2 is converted into the moisture content based on the calibration curve set above, and the moisture content data is output.

FIG. 3 is a functional block diagram of the data processing device 5. Next, data processing such as setting of a calibration curve will be described with reference to FIG. The data processing device 5
Is composed of a microcomputer or the like, and realizes each function of FIG. 3 by performing processing based on a control program stored in a program memory (not shown).

First, the color difference meter 4 is operated by the function of the block B1.
The raw data (lightness L value) is fetched at a predetermined sampling period, the noise component is removed by filtering the raw data in block B2, and the sludge property is identified in block B3 based on the lightness L value. Then, in block B4, it is determined whether to change the calibration curve according to the current sludge property.

For example, if the sludge properties have not changed, the calibration curve
If you do not need to change the
Repeat calibration B4 and keep the calibration curve when changing
Judge whether the hold time has elapsed, and
For example, in block B5, based on the lightness L value and the calibration curve data
To determine the calibration curve and determine the zero-order coefficient a of the calibration curve₀And the primary coefficient a
₁Is set in block B11.

The calibration curve in block B5 is determined as follows, for example. As described above with reference to FIGS. 4 to 6, the coefficients a ₀ and a ₁ of the calibration curve suitable for sludge properties are
The ratio of the raw sludge is almost linear, and the ratio of the raw sludge has a constant relationship with the brightness L value. Therefore, for example, the data of the relational expression between the coefficients a ₀ and a ₁ of the calibration curve and the lightness L value in FIG. 4 is stored in the memory 5a as the data of the calibration curve, and the lightness L value and this relational expression are stored in the block B5. Based on this, the coefficients a ₀ and a ₁ of the calibration curve are obtained and the calibration curve is determined.

In the processing of this block B5, the correspondence between the formula (coefficients a ₀ , a ₁ ) of the measuring line of FIG. 4 or the formula in the middle of these calibration curves and the lightness L value is stored in a table or the like. The calibration curve may be determined by storing it and selecting appropriate coefficients a ₀ and a ₁ of the calibration curve from the current lightness L value.

On the other hand, the raw data (absorbance signal) is fetched from the infrared moisture meter 2 by the function of the block B6, the raw data is filtered by the block B7 to remove noise components, and the invalid data is cut by the block B8. Then, in block B9, the absorbance data is averaged based on predetermined sampling data according to the moving position of the infrared moisture meter 2. In block B10, a sensor (not shown) or the like provided in the belt press type dehydrator 1 detects the cut of the dehydrated cake, and when the cut of the dehydrated cake is detected, the block B10 is detected.
At 8, the invalid data is cut.

Then, in block B11, the absorbance data averaged in block B9 is converted into a water content based on the currently set calibration curve, and the water content is output to the outside in block B12. The water content is output to the personal computer 6 or the like, and the personal computer 6 or the like collects and analyzes the water content.

In the above embodiment, an infrared moisture meter and a chromaticity meter are provided at the outlet of the dehydration cake of the belt press type dehydrator so that the leveling mechanism is not required. The present invention can also be applied to a case where the water content is measured by transporting the syrup with a belt conveyor or the like and leveling the dehydrated cake with a leveling mechanism.

In this case, the sludge dewatering means is not limited to the belt press type dewatering machine, but may be a centrifuge, a vacuum dewatering machine, a pressure dewatering machine, a screw press dewatering machine or the like. If a distance meter for measuring the distance to the cake surface is provided and the calibration curve of the infrared moisture meter is further corrected based on this distance, it is possible to eliminate the leveling mechanism and the like.

Further, in the above embodiment, as the plural kinds of sludges having different properties, only the digested sludge in the sewage treatment plant, the mixed sludge of the digested sludge and the domestic sludge, and the example using only the domestic sludge have been described. The plural types of sludge with different properties targeted by are not limited to this. That is, in the moisture content obtained from the absorbance of the infrared moisture meter, if the measured moisture content differs depending on the type of sludge even with the same absorbance, using color information by a color difference meter in addition to the absorbance by the infrared moisture meter, It can be applied to any sludge as long as an accurate water content can be obtained based on the above correlation.

[0050]

As described above, according to the present invention, in order to measure the water content of a dehydrated cake obtained by solid-liquid separation of sludge with an infrared moisture meter, a plurality of types of dehydrated cakes having different properties can be used. Information of the calibration curve of the infrared moisture meter is stored, the color of the dehydrated cake that is the measurement object is measured, and the calibration curve of the infrared moisture meter is determined based on at least the lightness information and the calibration curve information of this color information. I set it, so
The water content can be measured with an appropriate calibration curve according to the properties of the dehydrated cake, and the water content of the dehydrated cake can be measured immediately and the measurement error can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment in which the present invention is applied to a belt press type dehydrator.

FIG. 2 is a block diagram of a water content measuring device for a dehydrated cake according to an example.

FIG. 3 is a functional block diagram of a data processing device according to an embodiment.

FIG. 4 is a diagram showing the correlation between the absorbance of an infrared moisture meter and the measured water content for digested sludge, raw sludge and mixed sludge.

FIG. 5 is a diagram showing an example of a luminance L value when a color difference of a dehydrated cake containing only digested sludge is measured.

FIG. 6 is a diagram showing an example of a luminance L value when a color difference of a dehydrated cake is measured by changing a mixing ratio of digested sludge and raw sludge.

FIG. 7 is a front view of a mounting portion of an infrared moisture meter and a moving mechanism in an example.

FIG. 8 is a plan view of the mounting portion.

FIG. 9 is a side view of the mounting portion.

FIG. 10 is a diagram showing an example of the distribution of dewatering properties in the width direction of the filter cloth of the belt press type dewatering machine.

[Explanation of symbols]

1 ... Belt press type dehydrator, 2 ... Infrared moisture meter, 3 ... Moving mechanism, 4 ... Color difference meter, 5 ... Data processing device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C02F 11/12 ZAB C 7824-4D // B01D 33/048 B30B 9/24 Z (72) Inventor Tomoyuki Hayashi 1-4-9 Kawagishi, Toda City, Saitama Prefecture Organo Research Institute (72) Inventor Toshinobu Imamahama 1-4-9 Kawagishi, Toda City Saitama Prefecture Organo Research Institute (72) Invention Nobuyuki Tsunakawa 4-12-62, Higashi-Shinagawa, Shinagawa-ku, Tokyo Japan Tobacco Inc. (72) Inventor, Masaki Shoji 2-20-46, Horifune, Kita-ku, Tokyo JTE Engineering Co., Ltd.

Claims (4)

[Claims] 1. A method for measuring the water content of a dehydrated cake, comprising measuring the water content of a dehydrated cake obtained by solid-liquid separation of sludge with an infrared moisture meter, the infrared moisture of a plurality of types of dehydrated cakes having different properties. Information of the calibration curve of the meter is stored, the color of the dehydrated cake that is the measurement object is measured by a color difference meter, and the infrared moisture meter is measured based on the color information output by the color difference meter and the information of the calibration curve. The moisture content of the dehydrated cake which is the measurement object is measured by the infrared moisture meter based on the set calibration curve, and the moisture content of the dehydrated cake is measured. Method. 2. A method for measuring the water content of a dehydrated cake, which comprises measuring the water content of a dehydrated cake discharged from a dehydrator, wherein the color measurement by the color difference meter and the water content measurement by the infrared moisture meter are performed. The method for measuring the water content of a dehydrated cake according to claim 1, wherein the method is performed near the outlet of the dehydrated cake of the dehydrator. 3. A color difference meter for measuring the color of a dehydrated cake obtained by solid-liquid separating sludge, an infrared moisture meter for measuring the water content of the dehydrated cake, and a plurality of types of dehydrated cakes having different properties. Storage means for storing the information of the calibration curve of the infrared moisture meter, the calibration curve of the infrared moisture meter based on the color information output from the color difference meter and the calibration curve information stored in the storage means And a calibration curve setting means for setting the above. 4. The color difference meter and the infrared moisture meter,
The water content measuring device for a dehydrated cake according to claim 3, which is arranged so as to face an outlet of the dehydrated cake of a dehydrator for discharging the dehydrated cake which is an object to be measured.