JPS62127656A - Moisture measuring instrument for granule - Google Patents

Abstract

PURPOSE:To easily and precisely measure the moisture of granules by providing a pair of a microwave transmitter and a microwave receiver on upper and lower side walls of a measuring tank and calculating the amount of moisture of a charged body to be measured on the basis of the output signal of the receiver and the signal of a weight measuring instrument. CONSTITUTION:When a specific amount of sand is thrown in the measuring tank 5, a microwave is transmitted by the microwave transmitter 10 to the microwave receiver 12 through the charged sand. The sent microwave is attenuated by the moisture that the sand contains and reaches the microwave receiver 12. The atenuation quantity R of the microwave is proportional to the weight W of the sand after the tare of the measuring tank 5 is removed and the moisture percentage H, so the signals of the microwave receiver 12 and a load cell 6 are sent to an arithmetic display device to calculate and display the amount of moisture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for measuring the moisture content of powder or granular material using microwaves.

[Prior Art] For example, the amount of mixing water for concrete is the biggest factor that influences the quality of concrete, such as the fluidity of fresh concrete and the strength of concrete after hardening. Normally, to make 1m3 of fresh concrete, for example, about 300 cement
kg, sand approximately 800 kg, gravel 1100 kg, main fishing 20
0 kg is used, but it is said that a difference of 5 kg in water amount will result in a difference of approximately 2 cm in the slump of fresh concrete and a difference of 10 to 15 kg/cm2 in compressive strength of concrete after hardening. Generally, the moisture content of gravel is almost constant, but the moisture content of sand fluctuates by about 3 to 15%. Therefore, in order to produce high-quality concrete, one of the most important issues is to accurately grasp the water content of sand during mixing water volume management.

In order to measure the moisture content of this sand, the following moisture measurement method is conventionally known.

(1) Extract a sample of sand to be used from a sand storage tank or transportation system, heat and dry it using electric heat, infrared rays, microwaves, etc., and determine the moisture content from the difference between the weight before drying and the weight after drying. seek.

(2) Insert a capacitance sensor into the sand and determine moisture from changes in capacitance.

(3) Moisture content is determined by irradiating sand with radiation such as gamma rays or neutron beams, scattering or transmitting it, and measuring the amount of attenuation.

(4) Light or infrared rays are irradiated onto the surface of the sand, and moisture content is measured from the degree of reflection and absorption.

(5) Determine moisture by JIS gravimetric method or volumetric method.

[Problems to be solved by the invention] However, all of these methods take too much time,
It has advantages and disadvantages, including a lack of reliability, and has not yet been put into practical use. That is, (a) the sand sample to be measured is temporally and positionally shifted from the sand actually used.

(b) The measurement position is only near the surface of the sand, and the measured values are not representative of the entire surface.

(c) The measurement accuracy is low and there are many fluctuations, so the reliability of the measured values is poor.

(d) Calibration of measuring instruments is complicated and difficult to use.

(e) There are many parts that require manual labor, and automatic measurement is not possible.

Furthermore, depending on the measurement method, it may be greatly affected by factors other than moisture, such as the particle size, composition, and color of the sand itself, salt and alkalinity in the moisture, or the density and density of the loading, and it is difficult to correct for these factors. There are many problems such as requiring complicated operations.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems and to provide a moisture measuring device for powder or granular material that can easily and accurately measure the moisture content of an object to be measured made of powder or granular material. be.

[Means for Solving the Problems] The gist of the present invention to achieve the above-mentioned object is to provide a cylinder having a receiving part for a workpiece made of powder or granular material at its two ends and a discharge gate at its lower end. a measuring tank, a pair of microwave transmitters and a microwave receiver provided on the upper and lower side walls of the measuring tank, a weight detection device for measuring the weight of the measuring tank, and the microwave receiver. A moisture measuring device for powder and granular material, comprising: a calculation device that calculates and outputs the moisture content of the object to be measured filled in the measurement tank from the output signal of the weighing device and the signal from the weight measuring device. It is.

[Embodiments of the Invention] The present invention will be described in detail based on an embodiment in which water content during crushing discharged from the illustrated fresh concrete batcher plant is measured.

In this plant, as shown in FIGS. 1 and 2, an outlet 2 is provided near the bottom of a sand storage bin 1, and a sampling device 3 having a built-in screw conveyor is installed. Below the discharge port 3a of the sampling device 3, a cylindrical measuring tank 5 having a receiving port 4 at the upper end is arranged facing downward. It is supported by a weight detection part for measuring the weight consisting of. The measurement tank 5 is made of an electrically conductive material such as copper or brass and has a rectangular cross section so as not to dissipate microwaves to the outside. Microwave absorbing material 8 is pasted on the inner surfaces of both the upper and lower ends of the measurement tank 5, and the entire inner surface is further covered with a wear-resistant material made of synthetic resin. Further, a microwave transmitter 10 is attached to the side wall near the upper end of the measurement tank 5 via a waveguide 9 made of the same material as the measurement tank 5, and similarly to the side wall near the lower end. A microwave receiver 12 is attached via a waveguide 11 . Further, a discharge gate 14 driven by a power cylinder 13 is provided at the lower end of the measurement tank 5, and a level detection end 15 is provided at the upper end of the measurement tank 5.

The sand discharged from the discharge port 2 of the storage bin 1 passes through the discharge port 3a of the sampling device 3 and is thrown into the measuring tank 5 with the discharge gate 14 closed. When a predetermined amount of sand is put into the measuring tank 5, the output of the level detection end 15 closes the outlet 3a of the sampling device 3, and the microwave is transmitted from the microwave transmitter 10 through the filled sand to the microwave receiver. Fired to 12. The emitted microwaves reach the microwave receiver 12 after being attenuated by the moisture contained in the sand.

This attenuation? Theoretically, a'R is f: the microwave frequency, ε: the talking rate of the object to be measured, tanδ: the dielectric loss tangent, and E
When is the microwave intensity, H is the moisture content, and L is the passing distance, it is given by the following formula.

R = (2πfeε・tan8eE2*H*L) In other words, in this case, f, ε, tanδ, E, and L are constant values, so the amount of attenuation R of the microwave is proportional to the amount of water during the microwave passage. It turns out. Here, since the moisture content differs depending on the loading density of sand even if the moisture content H is the same, the weight of the measurement tank 5 and its attached mechanism is measured by the load cell 6 attached to the pedestal 7, and the moisture measurement due to the density of the sand is corrected.

Since the amount of attenuation R of the microwave is proportional to the weight W of the sand excluding the tare weight in the measurement tank 5 and the moisture content H, the signals from the microwave receiver 12 and the load cell 6 are sent to an arithmetic display device (not shown) to determine the moisture content. Calculate and display the amount. In this case, if the temperature of the sand fluctuates significantly, the water content can be calculated and corrected based on the temperature of the sand.

When the measurement is completed, the discharge gate 14 of the measurement tank 5 is opened and the sand is discharged into the original sand path through the discharge chute. By repeating this operation for each batch mixed by the concrete mixer, the water content of the sand can be continuously and accurately measured. Therefore, by feeding back this signal to the mixing control device of the fresh concrete batcher plant, it becomes possible to accurately correct the amount of mixing water.

FIG. 3 shows the measurement results using a test device using plastering river sand, using a microwave frequency of 3 GHz. In this test, within the range of moisture content of sand used in normal ready-mixed concrete batching plants, the results agreed with the actual measurements using the dry weight method with an error within ±0.1%. Moreover, the average measurement time per measurement was 20 seconds to 30 seconds from sand introduction to sand discharge.

The present invention takes advantage of the fact that the absorption and attenuation of microwaves by water is extremely large compared to other substances, so if the substance has a significantly smaller absorption and attenuation of microwaves than water, It can also be applied to granular materials.

[Effects of the Invention] As described above, the effects of the apparatus for measuring moisture content of powder or granular material according to the present invention can be summarized as follows.

■Since the water content of powder and granules that are the same in time and position as those actually used for kneading can be measured, the amount of water for kneading can be corrected accurately.

■Since the measurement time is extremely short, if necessary, it is possible to measure the moisture content for each batch and correct the amount of crosstalk water.

■Since the attenuation of microwaves by moisture is extremely large, accurate measurements can be made without being affected by the components of powder or other substances such as salt and alkaline content.

■It is economical because no thermal energy is required for measurement.

■Since all measurement operations can be performed electrically, remote control and fully automated measurements are also possible.

[Brief explanation of drawings]

The drawings show an embodiment of the apparatus for measuring the moisture content of powder or granular material according to the present invention, in which FIG. 1 is a front view, FIG. 2 is a side view, and FIG. 3 is a graph of measurement results. 1 is a sand storage bin, 2 is an outlet, 3 is a sampling device, 5 is a measurement tank, 6 is a load cell, 7 is a frame, 9.11
10 is a waveguide, 10 is a microwave transmitter, 12 is a microwave receiver, 14 is a discharge gate, and 15 is a level detection end. Patent applicant: Nippon Cement Co., Ltd., N&D Co., Ltd., Asano Seiki Co., Ltd.

Claims (1)

[Claims] 1. A cylindrical measuring tank with a receiving part for the object to be measured made of powder or granular material at the upper end and a discharge gate at the lower end, and a measuring tank provided on the upper and lower side walls of the measuring tank. A pair of microwave transmitters, a microwave receiver, a weight detection device for measuring the weight of the measurement tank, and an output signal of the microwave receiver and a signal from the weight measurement device to detect the inside of the measurement tank. 1. An apparatus for measuring moisture content of powder or granular material, comprising: a calculation device that calculates and outputs the moisture content of an object to be measured filled in the container. 2. The powder moisture measuring device according to claim 1, wherein microwave absorbing materials are arranged at both upper and lower ends of the measuring tank.