JPS638416B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring water content in sludge and the like containing water.

Moisture measurement methods include absolute dry method, Kafl
Fischer method, gas pressure method, electrical method, relative humidity measurement method, hydrogen atom detection method, infrared absorption method, etc.
Various moisture meters are in the development stage. Generally, a moisture measurement method based on the absolute dry method (gravimetric method) is adopted.
In other words, when measuring the moisture in a substance, the weight of the substance before and after drying is reduced by completely evaporating and removing the moisture contained in the substance by drying it using a drying oven or infrared rays, leaving it in an absolutely dry state. Moisture is measured from the percentage, but in drying methods that use a drying oven or infrared rays, the atmospheric temperature inside the drying oven is raised with a heating element such as a nichrome wire, and the radiant heat is used to heat and dry. Alternatively, there is a method of heating and drying using heat rays emitted from an infrared lamp, and in both cases, the object to be measured is gradually heated and dried from the outside to the inside. As a result, thermal efficiency is very poor, and it takes 4 to 5 hours to completely evaporate and remove water from a high-moisture-containing object to be completely dry, and it takes more than 1 hour even when using infrared rays. It takes a long time to dry, and it takes a long time to measure the moisture content. That is, although moisture measurement using the bone-dry method is accurate, it has the drawback of requiring a long time. Therefore, for example, when drying sludge, etc.,
Even if technology for continuously kneading and solidifying sludge, etc. has been developed, it is not possible to determine the moisture content of sludge in a timely manner, making it difficult to optimize and supply sludge solidifying agents technically and economically. It is becoming.
To solve the above problems, the idea of Utility Model Application No. 52-105828 (Utility Model Application No. 54-33183) uses high frequency waves to heat the object to be measured. However, this invention still requires a considerable amount of time until the object to be measured becomes completely dry, and the disadvantage is that the time required for measurement is also that long.

Furthermore, the invention disclosed in Japanese Patent Application Laid-Open No. 51-136490 has a function of heating an object to be measured using microwaves, measuring the weight of the object at regular intervals, and stopping heating when the weight change is zero. However, it still takes a considerable amount of time, and it also has the disadvantage that it also takes a lot of time to measure.

An object of the present invention is to provide a method and apparatus for measuring moisture using an absolute dry method, which allows measurement to be carried out in an extremely short period of time.

The present invention involves performing high-frequency dielectric heating drying on each object group as objects to be measured having different moisture contents in advance until they reach an absolutely dry state, and measuring the weight of the objects to be measured continuously or intermittently and measuring the elapsed time. By performing automatic weighing, the relationship between the change in moisture loss over time and the initial moisture content of each target group as the object to be measured is recorded, and then the same heating is performed to bring the object to be measured into an absolutely dry state. High-frequency dielectric dry moisture that measures the moisture content of the object to be measured by previously knowing the change in the amount of moisture loss over time and comparing it with the change relationship of the amount of moisture loss over time for the target group as the object to be measured. It is a measurement method.

The device for carrying out the present invention is a device that makes it possible to automatically dry, measure, and record water-containing materials in order to carry out the above-mentioned present invention, and as an embodiment, a device under the high-frequency dielectric heating electrode is used. It is equipped with a rotary table and consists of a device for stopping the rotary table at a fixed position, a lifting device attached to the rotary table, and a weighing device, and a control device and display device that performs modulation, amplification, and calculation processing on the output of the weighing device, and control of a high-frequency dielectric drying furnace. It is equipped with a device.

The moisture measuring method according to the present invention will be described. To measure the water content of sludge, etc., compare the dry state, measure the difference in weight of the object before and after at time intervals, and find the point where the weight difference generally becomes zero, which is considered to be an absolutely dry state. , moisture content is determined by comparing the weight of the object to be measured before drying.

If the weight of the measured object before drying is Wo and the weight of the measured object after drying is Wn, the moisture content is expressed as Wo-Wn/Wo x 100% or Wo-Wn/Wn x 100%.

In the present invention, when the object to be measured is subjected to high-frequency dielectric drying, the object to be measured rapidly approaches a dry state due to internal heat generation. The weight of the object to be measured at that time T ₁ is
If W ₁ is the time after time T ₁ has elapsed, and T ₂ is the time after which time T 1 has elapsed, and W ₂ is the weight of the object to be measured at that time T ₂ , then the rate of decrease in moisture in the object to be measured with respect to the elapsed time, that is, the decrease in water content. The ratio is expressed as △W/△T=W ₂ -W ₁ /T ₂ -T ₁ . In a state approaching an absolutely dry state, the object to be measured rapidly generates heat and moisture is expelled rapidly, and the ratio of the amount of moisture evaporation to time gradually decreases, but the time interval is short overall. Therefore, it is necessary to shorten the time interval ΔT for measuring the object to be measured, or it is necessary to measure it continuously and take it as a differential value dW/dT. Therefore, when performing high-frequency dielectric drying, the weight of the object to be measured must be measured continuously or intermittently at short intervals in a high-frequency dielectric drying furnace. The measured value of the object to be measured in the high frequency dielectric heating furnace needs to be recorded or displayed. For this purpose, the measuring device for the object to be measured converts the weight into an electrical signal, which is processed and recorded and displayed outside the high-frequency dielectric drying oven.

In moisture measurement according to the present invention, when the horizontal axis is the weight of moisture in the object to be measured and time is the vertical axis, and the change in moisture content is expressed as a curve, the curve shows characteristics depending on the properties of the object to be measured. Become. On the other hand, in the present invention, when the properties of the object to be measured are known in advance, the rate of change in the differential value of the change in moisture with respect to the time interval d ² W/dT ² can be calculated so that the object to be measured can be measured without waiting for an absolutely dry state. This allows you to know the moisture content of objects.

If the high-frequency dielectric drying furnace is vacuumed or depressurized to lower the vapor pressure, the object to be measured can be dried more rapidly.

Next, referring to an experimental example of moisture measurement according to the present invention, the high frequency dielectric drying furnace of the present invention used had an industrially assigned frequency of 2450MHz, an effective output of 600W,
It is a 400W and 200W three-type switching device, and when drying sewage sludge is measured, the time to reach an absolutely dry state is 1/10 to 1/30 compared to conventional infrared or electric heating drying ovens. Even when the measured values were statistically processed, there was no difference in measurement accuracy compared to the conventional method.

Next, by changing the sample weight of the object to be measured and looking at its drying characteristics, the time it takes to reach an absolutely dry state over a wide range is almost the same. 5g, 10g,
When changing the sample weight to 30g and 50g, the difference in time until it reaches an absolutely dry state is about 20% at most between the sample weights of 5g and 50g. Just put it in a container.

Under the same conditions, the shape of the sample to be measured with the same weight is determined by the diameter.
When we measured the time it took to reach an absolutely dry state for three types of cylindrical objects: 16φ, 50φ, and 60φ, we found that they were exactly the same, and the drying characteristics of the former and latter two were slightly different. be taken care of.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a high frequency dielectric drying oven equipped with a measuring device of the present invention. Reference numeral 1 denotes an electrode antenna that emits high-frequency radio waves, which are guided by a high-frequency generator 10 such as a magnetron. A stirring blade 2 is mounted below the antenna 1 so as to rotate when the antenna 1 is energized. A rotary table 3 is provided below the antenna 1 so as to be movable up and down as well as rotatably indexable. That is, the axis and rotation of the electric motor 4 are transmitted, and the rotary table 3 is moved freely in the axial direction by, for example, a spline.
is attached, and a lift 6 with rollers 5 pivotally attached to the upper end engages with a guide 8 fixed to the furnace body 7 so as to be able to slide vertically so that the rotary table 3 is stably supported at three or more locations. ing.

The lifts 6 are connected to each other by a cross member 9, which is fixed to the rod end of a lift cylinder 11. The axis of the roller 5 faces in the radial direction of the rotary table 3.

The electric motor 4 is a rotationally indexable pulse motor, a stepping motor, etc., or the electric motor 4 is
If the rotary table 3 is a rotary machine that can only rotate continuously, a dog is provided on the rotary table 3 and a micro switch that engages with the dog is fixedly installed. In general, dogs are installed at positions divided into the circumference of the rotary table 3 by the number of stops on the rotary table 3, but one dog may be provided, and a plurality of microswitches may be provided by equally dividing the circumference (none of these are shown). ). Holes 12 are formed in the rotary table 3 by equally dividing the circumference according to the number of indexes, and a container 13 is fitted into the hole 12 so as to be able to move in and out of the hole 12. The container 13 has a flange on the upper part, and the part below the flange is a cylinder that fits into the hole 12 leaving a slight gap, and the part below the flange is a smaller cylinder. A saucer 15 of the weighing device 14 is located at a position where the rotary table 3 is in the lowered position and contact between the container 13 and the rotary table 3 is broken, and the lower portion of the saucer 15 is connected to the detection section 17 by a connecting rod 16. In the measuring device 14, a detecting section 17 measures the contents of the container 13 via a connecting rod 16, and the measured value is converted into an electric signal and output.

Each of the above devices and parts is housed in a sealed furnace body 7 equipped with an openable/closable door (not shown), and the furnace body 7 is partitioned in the middle by a partition wall 18. The door requires an opening large enough to allow the container 13 to be attached and detached when opened. The furnace body 7 and its door are constructed so that high-frequency radio waves do not have a harmful effect on the human body. Of course, if these are to be operated remotely, the furnace body 7 is not necessary in that respect. Although not shown, when a vacuum pump for evacuating or depressurizing the inside of the furnace body 7 is provided, the measurement time can be more effectively shortened.

FIG. 2 is a block diagram showing a control circuit of the high frequency dielectric drying furnace shown in FIG. The electrical signal sent from the detection unit 17 is modulated and amplified by the modulation amplification circuit 19, sent to the storage/arithmetic unit 21, and stored together with the clock pulse.The differential value of the change in the measured value with respect to the time change is calculated, and the decrease in moisture during that time is calculated. The amount and rate of decline are becoming clear. 2
Reference numeral 2 denotes a recording and display device, which includes a digital readout and a printing device. The storage/arithmetic device 21 is configured to energize and deenergize the high frequency generator 10 via the high frequency control device 23 according to instructions thereof. The equipment control device 24 includes the electric motor 4 and the lift cylinder 11.
When the lift cylinder 11 is a hydraulic cylinder, it is a device that controls and supplies power to a hydraulic tank, a solenoid valve, etc. (not shown). 25 is a power source.

Next, we will discuss moisture measurement using a high-frequency dielectric drying oven.

The object to be measured is collected as a sample and placed in a container 13. When measuring only the moisture content in the object to be measured, it is sufficient to put a sample of the object to be measured, for example, approximately 10 g, into the container 13. If the drying characteristics are known in advance and you want to quickly determine the moisture content in the object to be measured, accurately weigh the sample of the object to be measured and place it in the container 13.
It will be kept in a fairly constant shape.

The door of the furnace body 7 is opened and the containers 13 containing the objects to be measured are inserted into the holes 12 of the rotary table 3, respectively. Next, close the door and press the start button to activate the lift cylinder 11.
The rod end of the rotary table 3 is lowered, and the lift 6 follows the downward roller 5 by gravity via the horizontal member 9, and the rotary table 3 is lowered. The container 13 is a rotary table 13
The sample is placed on the tray 15 at a further distance and weighed, and the signal is converted into an electric signal by the detection section 17, stored in the storage/arithmetic device 21 via the modulation amplification circuit 19, and recorded and displayed by the recording/display device 22 if necessary. Subsequently, a signal is sent from the storage/arithmetic device 21 to the device control device 24, the rod of the lift cylinder 11 rises, the lift 6 rises via the horizontal member 9, and the rotary table 3 is lifted via the rollers 5 and rises. When the end is reached, the electrical signal from the detection section 17 is deactivated, and the motor 4 is indexed to rotate by the equipment control device 24 via the modulation amplification circuit 19 and the storage/arithmetic device 21, and the rotary table 3 is indexed. At this time, the rollers 5 rotate while supporting the rotary table 3. Next, when the container 13 comes above the saucer 15, the rotary table 3 stops, descends, and after the same action as the above-mentioned measuring operation, rises.
3 is weighed together with the object to be measured.

Through the above operations, the initial weight of each object to be measured, including moisture, is measured and stored, and recorded and displayed if necessary. The operation of initially weighing the object to be measured can be omitted when a certain amount of the object to be measured is previously placed in the container as a sample. When this is finished, the high frequency control device 23 is
The signal is sent to the antenna 1 of the high frequency generator 10.
Higher frequency radio waves are emitted. At the same time, the stirring blade 2 rotates, the electric motor 4 is energized by the storage/arithmetic device 21 via the device control device 24 and continuously rotates, and the rotary table 3 rotates. The object to be measured is heated and dried by high-frequency dielectric action. After a certain period of time, the electric motor 4 is deenergized via the equipment control device 24 in response to a signal from the storage/arithmetic device 21, the rotary table 3 stops at the indexed position, and the lift cylinder 1
The rod 1 descends and the rotary table 3 descends, and the container 13 is placed on the tray 15 and weighed.The measured value is outputted as an electric signal by the detection section 17, modulated and amplified by the modulation amplification circuit 19, and stored in the storage/arithmetic device. 21
The signal sent to is stored and calculated, and if necessary, the amount and rate of decrease in moisture at that time are recorded and displayed based on the signal sent to the recording/display device 22. After the computation is completed, a signal is sent to the device control device 24, which forces the lift cylinder 11 upward, and the rod end lifts the lift 6 via the horizontal member 9 and pushes the roller 5. The rotary table 3 is lifted up through the hole 12, the container 13 is housed in the hole 12, and the edges of the container 13 and the saucer 15 are cut. When it is confirmed that the detection value of the detection unit 17 is zero, the electric motor 4 is energized and indexing is performed, and the rotary table 3 is indexed. Subsequently, the lift cylinder 11 is energized downward, and the rotary table 3 is lowered to move to the next container 13.
is placed on the saucer 15, weighed, and sent to the storage/arithmetic device 21, where it is recorded and displayed if necessary. Thereafter, changes in the weight of the objects to be measured in the container 13 placed in the hole 12 are sequentially stored in the same manner and recorded and displayed as necessary. After the rotary table 3 completes indexing for one revolution, it starts rotating continuously again, and after a certain period of time, the rotary table 3
The weight of the objects to be measured in the container 13 held in the container 13 is sequentially measured. These are repeated in the same way. The moisture in the object to be measured in the container 13 begins to rapidly decrease after a while from the beginning, and the rate of decrease in moisture gradually decreases. In the above process, the storage/arithmetic unit 21 calculates the rate of change in moisture content △W/△T each time the measurement is performed, and either △W/△T=0 or △W/△T.
When ≒0, the water content Wo-Wn/Wo or Wo-Wn/Wn is calculated and recorded and displayed, and at the same time a signal is sent to the high-frequency control device 23.
3, the high frequency generator 10 is deenergized and high frequency radio waves from the antenna 1 are no longer radiated. After the final measurement, the rotary table 3 is raised and returned to its original position.

Next, if the properties of the object to be measured are known in advance, the drying characteristics of the object, that is, the characteristic curve with time on the horizontal axis and the change in moisture on the vertical axis, are drawn in advance until it reaches an absolutely dry state. is stored in the storage/arithmetic unit 21, a certain amount of the object to be measured is placed in the container 13, and the hole 12 is
The rotary table 3 is lowered and the container 13 is placed on the saucer 15. In this state, the high frequency generator 10 is energized to dry the object to be measured, and the object to be measured is continuously weighed by the weighing device 14.
The storage arithmetic unit 21 via the modulation amplification circuit 19
The change in moisture over time is calculated as a differential value.
A differential value within a certain range compared with the data calculated as dW/dT and stored in the storage/arithmetic unit 21
With the agreement of dW/dT, the moisture content is calculated by calculating the extension of the moisture loss to the bone dry state. The recording/displaying device 22 may be a printing/recording device, but an oscillograph is suitable. In this case, the rotary table 3 does not rotate.

In the above embodiment, the rotary table 3 is moved up and down by the lift cylinder 11.
Alternatively, the lift cylinder 11 may be eliminated, the rotary table 3 performs only rotational indexing, and the weighing device 14 is mounted so as to be movable up and down, so that the container 13 is lifted by the tray 15 during weighing.

As described above, according to the present invention, since the object to be measured dries rapidly, the change in the moisture reduction rate △W/△T or the differential value dW/dT can be detected rapidly, and the moisture in the object to be measured can be quickly absorbed. The control of the continuous processing process can be improved by timely measuring the moisture content of the object to be measured and supplied to the continuous processing process of the object. Because it is high-frequency dielectric drying, the thermal efficiency is extremely high, and the weight and shape of the object to be measured do not have to be constant, and the amount has very little influence on measurement time and measurement accuracy within a certain range, so it is especially important to use a fixed amount as a sample. There is no need to collect. Furthermore, in order to determine the moisture content of a sample whose properties are known in advance, the measurement can be completed more quickly if the weight of the sample is kept constant.

Since the object to be measured itself generates heat and dries during high-frequency dielectric drying, ventilation may be cooled under the partition wall of the furnace, and it is easy to provide a weight detection device inside the furnace.
In addition, when mixing two or more types of water-containing materials, a high-frequency dielectric drying oven equipped with a rotating table is used.
It is also possible to measure the moisture content at the same time by placing each material in a container and mounting it on a rotating table.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the high frequency dielectric dryness measurement apparatus of the present invention, and FIG. 2 is a block diagram showing the control shown in FIG. 1... Electrode antenna, 3... Rotating table, 4
...Electric motor, 5...Roller, 6...Lift, 7...
... Furnace body, 8 ... Guide, 9 ... Horizontal member, 10 ... High frequency generator, 11 ... Lift cylinder, 12 ...
...hole, 13...container, 14...measuring device, 16...
... Connecting rod, 17 ... Detection section, 18 ... Partition wall, 19
... Modulation amplification circuit, 21 ... Memory calculation device, 22
... Recording display device, 23 ... High frequency control device, 2
4...Equipment control device.

Claims (1)

[Claims] 1. High-frequency dielectric heating drying is performed on each target group as objects to be measured having different moisture contents until they reach an absolutely dry state, and the weight of the objects to be measured is measured continuously or intermittently over an elapsed time. By performing automatic weighing in conjunction with measurement, the relationship between the change in moisture loss over time and the initial moisture content of each target group as the object to be measured is recorded, and then the same heating is performed to ensure that the object to be measured is completely By knowing the change in the amount of moisture loss with respect to time changes before the object becomes dry, the moisture content of the object to be measured is measured by comparing the change relationship of the amount of moisture loss with respect to time changes for the target group as the object to be measured. High frequency dielectric dry moisture measurement method. 2. The high frequency dielectric dry moisture measuring method according to claim 1, wherein the object to be measured is dried in a vacuum or under reduced pressure. 3. Claims that include a circuit that converts a measured value into an electrical output, modulates and amplifies it, stores it over time, processes the differential value of the amount of water loss with respect to time changes, and determines the dry state from the change in the differential value. The high frequency dielectric dry moisture measuring method according to item 1. 4. A high-frequency generator and an electrode for performing high-frequency dielectric inside the furnace body, a holding structure for a container of the object to be measured at a position receiving the dielectric action of the electrode, and a device for measuring the weight of the container that can be engaged with below the holding structure. The high-frequency dielectric dry moisture measuring device is equipped with a detection unit that electrically outputs a measured value to the measuring device, and stores in advance changes in the amount of moisture loss with respect to time changes due to high-frequency heating for each of the target groups as objects to be measured. The electrical output is modulated and amplified to perform memory calculations that include changes in the amount of moisture loss of the object to be measured over time, and from this change in amount of moisture loss, the object to be measured is detected before the object becomes completely dry. A high-frequency dielectric dry moisture measuring device comprising a calculation device for calculating the initial moisture content of an object, a high-frequency control controlled by instructions from the calculation device, a device control device, and a recording/display device. 5 Claim 4 comprising a container holding structure comprising a rotary table capable of vertical movement and indexing rotation.
The high frequency dielectric dry moisture measuring device described in Section 1.