Talc (Mg 3 Si 4 O 10 [ OH] 2) is a hydrated magnesium aluminum silicate mineral, a density of about 2.75g / cm 3, as a white crystalline substance, chemical stability, high melting point, specific heat Large, thermal conductivity, electrical conductivity, low shrinkage, strong oil absorption, acid and alkali resistance, as an excellent functional raw materials and fillers, widely used in rubber, plastics, coatings, paper, medicine and other industries. With the development of modern industry, the requirements for the fineness of talc powder are getting higher and higher, especially the ultrafine talcum powder (average particle size less than 10μm), which is currently in short supply in domestic and foreign markets. At present, the method for preparing ultrafine talc powder is mainly dry mechanical force pulverization, but various ultrafine pulverizing equipment generally have high energy consumption and low efficiency. Studies have shown that the most direct way to improve grinding efficiency and reduce energy consumption is to add grinding aids. For the study of talc grinding aids, Wu Yishan et al [1] comprehensively considered the factors affecting grinding, and proposed triethanolamine as the best grinding aid, and found the grinding time in the experiment of gradually considering the influencing factors of grinding separately. Optimal conditions. YANG Hua-ming et al [2] through the use of sodium hexametaphosphate was stirred ultrafine grinding mill talc, obtained ultra-fine powder of an average particle size of less than 1μm. Based on the previous research results, the authors used orthogonal experiments to fully consider the interaction of various grinding factors and conducted new experimental research. First, research methods (1) Sample properties and main equipment Test talcum powder, talcum powder from Qixia Milky Way Co., Ltd., average particle diameter D50 21.57μm, D90 is 47.76μm. Chemical composition (wt%): SiO 2 , 60.9; MgO, 3l. 3 ; CaO, 0.04; Fe 2 O 3 , 0.01. The experimental grinding equipment is a small ball mill modified by a three-roll four-bar mill. The cylinder has a diameter of 8.10 cm and an effective volume of 506.28 cm 3 ; the grinding medium is a steel ball. After the optimization experiment, the test conditions of the grinding machine were determined: the rotation speed was 91.5 r/min; the medium filling rate was 40%; and the 12 mm: 6 mm ball diameter mass ratio was 3:4. The laser particle size analyzer CILAS-l064 was used to measure the D50 and D90 before and after the sample test. The NDJ-9S digital viscometer was used to measure the viscosity change of the slurry to investigate the dispersion effect of the grinding aid. The photoelectron spectrometer (XPS) was used. ) K-Alpha, to detect the final contamination of talc by steel balls. The grinding aids for the test were ammonium chloride (solid, chemically pure), triethanolamine (viscous liquid, technical grade) and sodium hexametaphosphate (solid, analytical grade). In order to minimize the chemical composition of talc and to adjust the pH of the slurry, deionized water is used to adjust the slurry. (2) Test plan The main factors affecting the grinding efficiency and energy consumption are the pulp concentration, the grinding environment such as pH, the type and amount of grinding aid (the mass ratio with the slurry [3] . The test procedure is as follows: weigh 200g of the original talcum powder Adding deionized water to the corresponding ratio, adjusting the pH of the slurry with hydrochloric acid and NaOH solution, adding a certain amount of grinding aid to the slurry, stirring and mixing, and then placing the slurry into the mill containing the steel ball, after sealing Grinding for 1 h. The final test test index has the change of viscosity μ (the difference between the viscosity of the slurry after the original slurry and the grinding aid), ΔD50 (the difference between the sample D50 and the original D50) and ΔD90 (the sample) The difference between D90 and the original D90. The L827 orthogonal experiment considering the interaction of factors was designed. The specific factors and levels considered are shown in Table 1. Because of the interaction between the various factors, this has not been considered in the previous experimental research, and the experimental results obtained have a certain deviation from the objective reality. Starting from the actual situation, the experimental process and results of this test program are shown in Table 2 and Table 3. Second, the results of the discussion In the orthogonal experiment where the grinding aid is ammonium chloride and sodium hexametaphosphate, △D50 is used as the test index. According to Y2, the order of influence factors of each factor is: A×B>B×C>B>A >C>A×C>D; with △D90 as the experimental index, the conclusion drawn from Y3 is: C>B×C>A>B>A×C>A×B>D. The K1 and K2 values ​​of the average group of indicators. When the test index is viscosity, it is necessary to consider A×C (A and C interaction) after considering the D, A, and B factors successively. The calculation results are shown in Table 4. From the perspective of the change of slurry viscosity, the best experimental condition selected is A1B1C2D2, that is, ammonium chloride is selected as the grinding aid, the grinding environment is acidic environment (pH=5.5±0.1), and the grinding aid dosage is 0.3% of the pulp. The concentration of the slurry is 50%; using the same analytical method, from the angle of △ D50 analysis, the best test condition is A1B1C2D1, that is, ammonium chloride is selected as the grinding aid, and the grinding environment is acidic environment (pH=5.5± 0.1), the amount of grinding aid is 0.3% of pulp and the concentration of pulp is 50%; from the angle of △D90, the best test condition is A1B2C2D1, that is, ammonium chloride is selected as grinding aid, and the grinding environment is alkali. Sexual environment (pH=9.4±0.1), the amount of grinding aid is 0.3% of pulp and the concentration of pulp is 50%. Based on the results of various indicators, the best experimental conditions derived from △D50 produce the best grinding aids, so the best experimental plan determined initially is as follows: ammonium chloride is selected as the grinding aid, and the grinding environment is acidic. (pH=5.5±0.1), the amount of grinding aid is 0.3% of pulp and the concentration of pulp is 50%. Due to the obvious oxidation phenomenon when cleaning steel balls during the test with ammonium chloride as a grinding aid. In view of the loss of the steel ball, triethanolamine was used instead of ammonium chloride for the orthogonal test. From Table 3, ΔD50 and ΔD90. The experimental results show that the grinding effect of triethanolamine is obviously better than that of ammonium chloride, and the loss of the steel ball is small during the whole test. The orthogonal test with triethanolamine and sodium hexametaphosphate as grinding aids is carried out. The best experimental conditions are: acidic environment (pH=5.5±0.1), the dosage is 0.5% of pulp quality, and the pulp concentration is 50%. The photocatalytic spectrometer (XPS) K-Alpha was used to test the dry superfine talcum powder and the talc powder after grinding and grinding. It was found that the content of Fe was below 0.01%, which basically met the food. Industrial requirements for grade talc. However, in the question about steel ball contaminated samples, there is a new discovery: the phenomenon of large content of C in talc powder, about 20% (excluding the atomic content after hydrogen), but wet method Grinding of grinding aids is less than dry conditions, and the entrainment of C elements can be reduced by nearly 7 percentage points. In ultra-fine grinding, the phenomenon that the steel ball C element is brought into the talc powder is beneficial to the environmental application of the talc powder (such as the application of the adsorption of talc powder in water treatment), but in food and medical applications, Subsequent removal processing is required. Third, the application In the ultrafine grinding of a certain ball-to-material ratio, there is a phenomenon of ultrafine powder balance particle size (limit particle size), but further grinding after adding a grinding aid can reduce the equilibrium particle size to achieve ultrafine fineness. Degree requirements. In this study, the best experimental scheme of ultrafine talc grinding determined above was used to further ultrafine grinding of talc powder (D50=3.25μm, D90=12.57μm) with balanced particle size to achieve reduction of talcum powder. The purpose of balancing the particle size. The particle size distribution of talc before and after ultrafine grinding is shown in Figure 1. After drying the talc powder by ultra-fine grinding with wet grinding aid, XPS detection showed that the atomic number of N, Cl and C (accounting for the percentage of the total number of atoms in the sample after removal of H) was 0.93%, respectively. 32.46%, 21.88%. Considering the safety of ultrafine talcum powder in food and medicine, the choice of grinding environment and grinding aid should be considered comprehensively and the subsequent impurity removal treatment should be strengthened. When selecting grinding aids for industrial applications, the economic and environmental requirements and the quality requirements of abrasive products should be considered in consideration of the types and dosages of grinding aids [4]. As a grinding aid, triethanolamine (irritating to the skin) and ammonium chloride, based on the above considerations, ammonium chloride has the advantages of low cost and environmental friendliness relative to triethanolamine. Fourth, the conclusion (1) Using the orthogonal experiment of factor interaction, the best grinding aid for ultrafine grinding talc was found to be triethanolamine (the amount is 0.5% of the pulp quality), and the best experimental conditions are acidic environment (pH=5.5). ±0.1), the pulp concentration is 50%, and the triethanolamine at this time has the best dispersion and grinding efficiency. (2) Adding triethanolamine to wet-grind talc powder with a balanced particle size, and further reducing the equilibrium particle size can be obtained. (3) From the perspective of economy and environmental protection, compared with triethanolamine, ammonium chloride is selected as a grinding aid, which has the advantages of safety and low cost. However, there is a phenomenon that ammonium chloride corrodes steel balls in the test. Replace the steel ball with a grinding medium of corundum or ceramic. (4) When using steel ball wet superfine grinding, attention should be paid to the influence of C element and grinding aid on the content of talc. For different purposes, appropriate follow-up should be taken. Coated Steel Pipe,Steel Pipe With Pe Coating,Pe Coating For Steel Pipe,Inner Layer Coated Steel Pipe SHANDONG DONGHONG PIPE INDUSTRY CO., LTD , https://www.donghongpipe.com