JPH0140945B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for measuring fineness that can be easily and accurately measured, and that can be incorporated into an online system. When using a conventional classifier to determine the fineness based on the weight ratio of the input amount to the classifier and the yield after classification (for example, return powder yield), due to the performance limitations of the classifier, 50% separation is required. The particle size (hereinafter referred to as classification point) is
The particle size is 15 μm or more, and therefore, the correlation between weight ratio and fineness is low, and improvement of this has been desired. As a result of various studies, the present inventors found that 2 to 14μ
The present invention was completed based on the finding that the correlation between the weight ratio and the fineness is very high by classifying the particles at an arbitrary classification point within the range of 5 to 10 μm. That is, the gist of the present invention is that when measuring the fineness of powder by the weight ratio of the amount input to the classifier and the yield after classification using a wind classifier, the classification point is 2.
A method for measuring the fineness of powder, which is characterized by classifying under conditions that exist within the range of ~14 μm. The wind classifier used in the present invention is preferably a vortex classifier, particularly a forced vortex classifier, but any classifier with a classification point within the range of 2 to 14 μm can be used. In the above eddy current classifier, the classification point is 2 to 14 μ
In order to fall within the range of m, the number of revolutions, air volume, etc. of the classification rotor of the wind classifier may be adjusted. The reason why the classification point is limited to 2 to 14 μm is that outside this range, the correlation between the weight ratio and the fineness deteriorates. The fineness in this invention is the specific surface area,
Moreover, the yield after classification is the amount of coarse powder or the amount of fine powder after classification. When performing process control using specific surface area as the fineness, set any point within the range of 2 to 14 μm as the classification point in advance, and use multiple powder samples with different fineness to determine the specific surface area and classification. If you find the relational expression between the front and rear weight ratios, you can use this wind classifier to
By measuring the weight ratio before and after classification, the corresponding specific surface area can be easily determined. The case of measuring the fineness of cement will be explained with reference to FIGS. 1 and 2. In FIG. 1, a screw conveyor, a belt conveyor, an air slide, etc. can be used as the sample transport device 1, and the end thereof is connected to the return path 3, and a sampling gate 2 is installed in front of the end. establish. The classification feeder 4 includes a receiving tank 4' for powder and granular material and a screw feeder 4 for discharging the powder and granular material from the receiving tank, and further includes a weighing scale 5 capable of measuring the entire weight of the receiving tank and the discharge screw feeder. It is provided. The classifier 6 is preferably one disclosed in Japanese Patent Application Laid-open No. 53-76466, and its structure is as shown in FIG.
A classifier with this structure is convenient for setting the classification point to 14 μm or less. 7 is a hopper for coarse powder, which is for receiving the coarse powder discharged from the classifier 6. This hopper 7 is provided with a weight scale 8. 9 is a discharge route. Reference numeral 10 indicates a fine powder collecting device such as a vacuum filter, 11 indicates a discharge path thereof, 12 indicates an air volume control valve, and 13 indicates a blower. 14 is a computing unit connected to each weighing scale 5, 8;
Based on this, the fineness is calculated. FIG. 2 is a detailed diagram of the classifier 6, with 1
5 is a casing, 16 is a powder inlet, 17 is a dispersion blade, 18 is a dispersion disk, 19 is a coarse powder outlet, 2
0 is an outer classification blade, 21 is an inner classification blade, 22 is an auxiliary blade, 23 is a classification rotor, 24 is a balance rotor, 25 is an air inlet, 26 is a fine powder outlet, 2
7 is a vortex casing, 28 is a classification chamber, and 29 is a rotating shaft. The classification mechanism will be explained below with reference to this classifier. (1) Regarding air flow: As shown in FIG. 2, the air sucked in from the air inlet 25 is given a velocity component in the circumferential direction by the auxiliary vanes 22, and enters the classification chamber 28 in a swirling state. The classification rotor 23 and the balance rotor 24 are fixed to a rotating shaft 29 and driven by a drive motor. Therefore, the air in the classification chamber 28 has almost the same peripheral speed as the classification rotor due to the auxiliary blades 22. The role of the balance rotor 24 is to obtain a uniform radial flow on the circumferential surface of the classification chamber and to reduce the pressure loss of the classifier here. The air exiting the balance rotor 24 is guided to the classifier outlet by the swirl casing 27, and is connected to a blower via a cyclone, bag filter, etc. on the way. The air flow at this time is indicated by arrows in the figure. (2) Regarding the flow of powder and granules; Powder and granule raw materials fed into the powder inlet 16 by an appropriate feeding means are carried by the dispersion blade 1 while being carried by the air flow.
7, it is divided almost uniformly on the circumferential surface,
Primary dispersion of the granular material is performed. The powder and granules ejected from the dispersion blade 17 in a substantially tangential direction reach the dispersion disk 1
8, and then transferred to classification chamber 2 in a completely dispersed state.
8. Here, each particle of the granular material is subjected to a centrifugal force due to the rotational flow and a drag force due to the radial flow. Among these particles, coarse particles for which the relationship of centrifugal force>drag force is satisfied are sent to the outside of the classification rotor and taken out from the coarse powder outlet 19 in an air-sealed state using a rotary valve or the like. On the other hand, fine particles for which the relationship of centrifugal force < drag is carried by the airflow to the outside of the device via the balance rotor 24 and the spiral casing 27, and are collected by a collection device such as a cyclone or bag filter. . In the case of this classifier, the classification point is adjusted by changing the rotational speed of the classification rotor 23 and balance rotor 24 or the amount of air passing through the classification chamber 28. Using such a measuring device, the fineness of a powder or granule is measured as follows. The powder and granules that are to become products are continuously sampled during the manufacturing process, and approximately
Conveys with a capacity of 500Kg/H. Further, the sample is supplied to the supply feeder 4 by opening the gate 2 provided on the sample transporter 1. In this case, the sampling amount is approximately 30 kg and the opening time requires 3 to 4 minutes, but at other times the gate 2 is closed and the sample enters the return path 3 and joins the product. The weight is measured at the supply feeder 4 after and before sampling, and the net weight of the sample is calculated by subtracting the weight. This sample is gradually fed to the classifier 6 by the feeder 4'',
Classification is performed as described above. The classification point in this case is 5
The coarse powder obtained is placed in a coarse powder hopper 7, where the weight before and after classification is measured, the net weight is obtained by subtraction, and the fineness is calculated by a calculator. The coarse powder after the measurement is sent to the discharge route 9. On the other hand, the fine powder after classification is collected by a fine powder collection device 10 and sent to a discharge path 11. In the computing unit 14, the fineness is obtained by the following equation. _y =aX+ _b y _: Specific surface _area (Blane value) _cm ² _/ g : After classification 〃 W ₃ : Weight of coarse powder hopper after classification W ₄ : Before starting classification 〃 a, b: Coefficients The above classifier when the classification point is changed from 1.0 to 19.0μm The relationship between the weight ratio of the amount of coarse powder after classification to the input amount and the specific surface area (Blaine value) is shown in FIG. 3 and the table below.

【table】

[Table] From this result, the classification point is 2 to 14μm, especially 5 to 14μm.
It can be seen that if it is selected within the range of 10 μm, there is a high correlation with the fineness. According to the present invention, the fineness of powder can be measured accurately, quickly, and easily. Therefore, in industries that handle powder such as cement, it is possible to measure the fineness of powder during the manufacturing process. It can be suitably applied.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a measuring device for carrying out the method of the present invention, Fig. 2 is a longitudinal sectional view of a classifier used in the method of the present invention, with one side omitted, and Fig. 3 is the above-mentioned 2 is a chart showing the relationship between the weight ratio (%) of the amount of coarse powder after classification to the amount input to the classifier and the specific surface area (Blaine value) when the classification point is changed in the classifier. 1... Sample transporter, 2... Sampling gate, 4... Classification feeder, 5, 8... Weight scale, 6... Classifier, 7... Hopper for coarse powder.

Claims (1)

[Claims] 1. When measuring the fineness of powder using a wind classifier based on the weight ratio between the amount input into the classifier and the yield after classification, classify under the conditions that the 50% separated particle size is within the range of 2 to 14 μm. A method for measuring the fineness of powder, which is characterized by: