RU2267117C1 - Method of determining time of mixing loose materials - Google Patents

Abstract

FIELD: investigating or analyzing materials.

SUBSTANCE: method comprises processing the image of the surface of specimens sampled from the mixing device each specified time interval. The maximum homogeneity can be judged by the minimum in the plot of the dependence of brightness of image color on duration of mixing.

EFFECT: enhanced accuracy.

4 cl, 2 tbl

Description

The invention relates to techniques for producing ceramic and cermet materials, and in particular to methods for controlling the homogeneity of a mixture, for example, containing nanosized metal powder, and can be used in the chemical and pharmaceutical industries.

A known method for determining the homogeneity of the charge [Method for determining the quality of mixing bulk materials. A.S. USSR 347070. MKI B 01 F 3/18, G 01 N 23/00 / Vekhtsyus L. I., Yarashyunas K. I., publ. 03/16/71.], Including the introduction into the mixed mass of short-lived radioactive isotopes. The disadvantage of this method is the difficulty of working with short-lived isotopes, the need for special equipment for measuring radioactivity in the charge volume and the inevitable contamination of the charge with extraneous impurities.

There is also known a method for determining the uniformity of a granular mixture [Method for determining the uniformity of a granular mixture. Application No. 2002106464, prior, dated 12.03.02.//Ivanova A.P. et al.], including sampling operations, light scattering measurements using three photometric devices, and the conversion of optical density into an electrical signal, the value of which is used to judge the degree of charge uniformity.

The disadvantage of this method is the complexity of the hardware design, insufficient sensitivity and accuracy of determining the degree of homogeneity of the charge. This is especially true for mixtures in which one of the components is not a macro component, but an additive in an amount measured in units and tenths of a percent. In addition, photometry is difficult in gray mixtures that do not have a pronounced color.

Closest to the proposed invention is a method for determining the quality of the prepared mixture while optimizing its mixing time [Method for preparing the molding mixture. A.S. SU 1106578 A, B 22 D 5/00, 07.08. 1984. - Bull. No. 29 // Kurchenko A.B. and etc.]. The method includes measuring the power consumption of the mixer during mixing of the components. The optimal time for unloading the mixture is determined by the minimum power consumed by the mixing, following after the first absolute maximum.

The disadvantage of this method is the complexity of the hardware design and the limitation of its applicability by devices such as a propeller mixer, the power consumption of which substantially depends on the resistance of the material to the movement of the blades, and cannot be used for other devices (mixers with a crankshaft, drum-type devices, twin-shaft mixers, etc. P.). In addition, the sensitivity of the method does not allow to solve the problem when adding coarse particles of ultrafine reagent in the form of an additive in a small amount (0.1-5% wt.).

The task of the invention is to simplify the operation of controlling the degree of homogeneity of the mixture with a simultaneous increase in the accuracy of determining the optimal required homogenization time.

The task is achieved by using the computer color model RGB (Red - red, Green - green, Blue - blue) to process a computer image of the surfaces of the samples of the mixture taken from the mixing device and molded in the form of a flat cylinder (tablets).

The application of the color model method is based on the fact that in the process of mixing blends containing highly dispersed components, for example, an oxide-metal charge containing nanodispersed metal, the aggregates of nanodispersed particles are loosened and, as a result, the mixture is gradually darkened. Almost all oxides are white, many silicate materials are light-colored (beige, light brown, etc.). When co-grinding or mixing the components of the metal-oxide mixture, the oxide serves as a dispersant for aggregates of nanodispersed metal particles, and the metal, distributed over the oxide particles, paints it in gray color, since the tone level of the self-coloring of the finely dispersed metal is quite low (dark gray, almost black color). The RGB program has 256 level tone gradation. White color corresponds to the maximum brightness value with RGB coordinates (256, 256, 256), black - zero. All other colors and tone levels have intermediate values. Using the histogram tool of this program, it is possible to estimate the brightness of the image in digital form, and, therefore, an objective comparison of the color of individual objects. The essence of the developed method for assessing the homogeneity of a metal-oxide mixture is that the determination of the optimal duration of the mixing process is carried out according to the schedule for changing the intensity (brightness) of the color of the mixture. Optimum-sufficient can be considered a point in time at which a color change is not observed.

Example.

To assess the optimal time and quality of mixing a mixture containing 99% wt. oxide and 1% wt. nanodispersed metal, at certain intervals, a small sample is taken from the total mixture, the size of which does not affect the overall composition of the mixture. Samples are formed from the selected material in the form of flat cylinders (tablets) with a diameter of 20-25 mm and a height of 4-5 mm.

The surface of the samples is scanned using any computer program that allows this, with an increase of 100 - 200% (figure 1, table 1). The resulting image is processed using computer RGB color models using Adobe Photoshop, including operations:

- selection of the edited area in the range of 22500-37000 pixels (figure 2, table 2);

- checking the dynamic range of the image by plotting a histogram (Fig.3 a, b);

- plotting the dependence of the brightness value and the standard deviation of the brightness of the color of the sample of the mixture from the mixing time (figure 4);

- fixing the time at which the color tone stops changing. In the future, when preparing the charge from these components, you can adhere to the mixing time determined in this way.

Figure 4 shows that the minimum brightness of the color is achieved with a duration of mixing of this mixture of 740 minutes (12 hours 20 minutes). This time can be considered the minimum necessary for the homogenization of this mixture.

When scanning samples from pressed mixtures, an object magnification of at least 100% and not more than 200% should be selected. With a smaller increase, the sensitivity to the variation in color intensity decreases, and accordingly, the accuracy of determining the optimal homogenization time of the powder mixture suffers (Table 1). With an increase of more than 200%, only part of the object is analyzed, this also reduces its accuracy, in addition, an increase above 200 is inconvenient for work, because in this range, the display's ability to resolve individual fragments is exceeded. The most convenient increase for working with objects having a diameter of 20-25 mm is - 100%.

The size of the analyzed area at the same magnification of the object also determines the value of the standard deviation and a fixed range of variation in the brightness of the color (values reflecting the sensitivity of the method to changes in uniformity and level of color tone). Under the conditions of the experiment (the diameter of the scanned object is 25 mm, the increase during scanning is 100%), the optimal range is 22500-37000 pixels, which corresponds to 30-50% of the image area of the scanned sample. Analysis of the area of the maximum possible size (34000-37000 pixels) gives the most complete picture of the nature of the color of the object. A smaller square, if necessary, allows you to select a defect-free pressing section. When processing an area smaller than 22500 pixels (less than 30% of the sample area), the sensitivity of the method decreases (Table 2).

The possibility of analyzing the degree of charge homogeneity using RGB computer color models was tested and confirmed by a direct research method - microprobe analysis on a Camebax instrument in characteristic metal radiation. Analysis of microprobe data shows that the uniformity of the distribution of metal in the mixture monotonously increases according to the mixing time and for this mixture reaches a limit value with a mixing time of 740 minutes (12 hours 20 minutes).

Table 1 Mixing time of two analyzed mixtures Enlarging an image of an object during scanning Range of brightness variation (max-min), rel. units The average standard deviation in the mixing time interval 10-40 minutes fifty thirteen 3,730 10-40 minutes 100 14 4,843 10-40 minutes 200 14 4,842 table 2 Mixture components The analyzed area, pixel. Range of brightness change, rel. units The average standard deviation,% Talc-aluminum 8910 7 4,442 Kaolinite aluminum 9568 6 4,525 Talc-aluminum 22500 fifteen 4,857 Kaolinite aluminum 22500 16 4,951 Kaolinite aluminum 34320 17 5,150 Talc-aluminum 36099 17 5,425

Claims (1)

A method for determining the mixing time of bulk materials, including sampling from a mixing apparatus, measuring the sample parameter depending on the mixing time and determining the mixing time to a minimum on the specified dependence, which corresponds to the achievement of the maximum possible homogeneity of the mixture, characterized in that the sample is pre-compressed in the form of tablets receive a tablet image on a scanner; process the resulting image using computer RGB color models to obtain bright histograms ty, which is used as the measured parameter of the sample.

Images