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CN-121978268-A - Method for identifying aluminum ash contained in low-grade bauxite

CN121978268ACN 121978268 ACN121978268 ACN 121978268ACN-121978268-A

Abstract

The invention relates to the technical field of chemical analysis, in particular to a method for identifying aluminum ash contained in low-grade bauxite, which comprises the following steps of primarily judging the aluminum ash contained in a bauxite sample to be identified if precipitated particles exist, determining the aluminum ash by utilizing wet chemistry and XRF working curves, and determining the aluminum oxide content of the bauxite to be identified if the aluminum oxide content measured by S2.1 is lower than the aluminum oxide content measured by S2.2 by more than 0.8 percent, wherein the aluminum ash is determined to be contained in the bauxite sample to be identified. The invention combines two methods of wet chemical determination (750-800 ℃ alkali melting) and XRF determination (1050-1100 ℃ high-temperature melting), utilizes the solubility (melting) difference of insoluble phases in aluminum ash at different temperatures, realizes the accurate identification of aluminum ash, establishes a double judgment standard of combining 'observed precipitated particles' and 'measured value difference of more than or equal to 0.8 percent', and improves the reliability of identification results.

Inventors

  • BAI WANLI
  • WU XUGUANG
  • Hu Zongxi
  • CUI JUNFENG
  • LIU SHUIHONG
  • CHEN XIU
  • ZHAO YAFEI

Assignees

  • 中铝山西新材料有限公司

Dates

Publication Date
20260505
Application Date
20251215

Claims (6)

  1. 1. A method for identifying that low-grade bauxite contains aluminum ash, which is characterized by comprising the following steps: S1, primarily judging aluminum ash, namely weighing a bauxite sample to be identified with a certain mass, adding sodium hydroxide into a crucible according to a proportion, melting and melting the bauxite sample in a muffle furnace at 750-800 ℃ for not less than 20min, taking out the bauxite sample, adding deionized water for cooling, transferring the melted bauxite sample into a 250mL volumetric flask with hydrochloric acid and boiling water for dissolving the melted bauxite sample, fixing the volumetric flask to a volume, cooling the volumetric flask to room temperature, standing the volumetric flask for more than 30min, and observing whether undissolved precipitate particles exist in the volumetric flask; S2, aluminum ash determination: S2.1, weighing supernatant in the volumetric flask in the step (1), adding lactic acid, shaking uniformly, adding EDTA solution, shaking uniformly, adding xylenol orange indicator, neutralizing with ammonia water until the solution is purple red, immediately adjusting to yellow with hydrochloric acid, adding water for dilution, heating and boiling for 2-5min, adding acetic acid-sodium acetate buffer solution with pH=5.2-5.7 while hot, shaking uniformly, cooling to room temperature, supplementing xylenol orange indicator, titrating with 0.020mol/L zinc nitrate standard solution until the solution is purple red, immediately adding potassium fluoride solution, boiling for 3-5min, taking down to room temperature, supplementing xylenol orange indicator, titrating with 0.020mol/L zinc nitrate standard solution to purple red as a second end point, recording the volume V of zinc nitrate standard solution consumed by the second end point, and calculating the mass fraction (%) of aluminum oxide content according to the formula (1): Wherein m is the mass of a corresponding bauxite sample to be identified in the measured supernatant, the unit is gram and g, 0.001 is 1mL of zinc nitrate standard solution, the unit is gram and g, and V-the second end point consumes the volume of the zinc nitrate standard solution, the unit is milliliter and mL; S2.2, weighing a certain mass of bauxite sample to be identified, which is the same as that in the step (1), in a platinum yellow crucible, adding a mixed solvent of anhydrous lithium tetraborate and lithium metaborate, then adding an ammonium nitrate aqueous solution to a weighing substance of the platinum yellow crucible, pre-oxidizing for 10-15min at 650-700 ℃, then melting for at least 15min at high temperature, and injecting a melt into a mold to cool to form a glass sheet sample; S2.3, if the content of alumina measured by S2.1 is lower than that of alumina measured by S2.2 by more than 0.8%, determining that the bauxite sample to be identified contains aluminum ash.
  2. 2. The method of claim 1, wherein the alumina content of the bauxite to be identified is less than 60%.
  3. 3. The method for identifying the aluminum ash contained in the low-grade bauxite according to claim 1, wherein the mass of the bauxite sample to be identified which is weighed in the step (1) is 0.20g-0.30g, and the mass of the added sodium hydroxide is 10-12 times of the mass of the bauxite sample to be identified.
  4. 4. The method for identifying the aluminum ash contained in the low-grade bauxite according to claim 1, wherein the mass of the bauxite sample to be identified weighed in the step (3) is 0.50-0.70 g, and the mass of the added mixed solvent is 10-15 times of the mass of the bauxite.
  5. 5. The method according to claim 1, wherein in the step (3), the mass ratio of the anhydrous lithium tetraborate to the lithium metaborate is 12-67:22-33.
  6. 6. The method according to claim 1, wherein in the step (3), the high-temperature melting temperature is 1050 ℃ to 1100 ℃.

Description

Method for identifying aluminum ash contained in low-grade bauxite Technical Field The invention relates to the technical field of chemical analysis, in particular to a method for identifying that low-grade bauxite contains aluminum ash. Background Bauxite is a basic raw material for producing alumina, and its quality directly affects the efficiency and cost of alumina production. Bauxite grade is generally measured in terms of its alumina (Al 2O3) content and aluminum to silicon ratio (mass ratio of Al 2O3 to SiO 2). With the increasing exhaustion of high-quality bauxite resources, a part of suppliers are pursuing economic benefits, and secondary aluminum ash (an industrial waste material containing insoluble aluminum-containing phases such as alpha-alumina, aluminum magnesium spinel, metallic aluminum, aluminum nitride and the like, which is generated in the aluminum industry) is doped into low-grade bauxite so as to artificially improve the apparent alumina content and the aluminum-silicon ratio of the ore, thereby selling the ore according to the price of the high-grade ore. However, these aluminum-containing phases in aluminum ash have high chemical stability under the conventional bayer process alkaline leaching conditions, are extremely difficult to dissolve, not only cannot contribute effective aluminum resources for alumina production, but also can enter red mud as solid waste, increase the solid waste treatment burden, dilute the concentration of effective aluminum, and reduce the production efficiency. In addition, aluminum ash, which typically contains higher fluoride, can enter the solution system as the process proceeds and long-term accumulation can corrode production equipment. Currently, conventional methods for chemical composition analysis of bauxite include mainly wet chemical analysis and X-ray fluorescence spectroscopy (XRF). Wet chemical analysis is a classical quantitative analysis method, for example, chinese patent CN104133036a discloses an analysis method for determining alumina in bauxite, which adopts sodium hydroxide to melt and decompose a sample, uses lactic acid to mask titanium after acid dissolution, and then determines the content of alumina by a potentiometric titration method, and aims to improve the accuracy and precision of the determination result. However, the aim of the wet chemical analysis or XRF analysis is to determine the total content of elements, and it is not possible to distinguish effectively between alumina of different phase origin in the sample, i.e. between readily soluble boehmite or gibbsite from natural bauxite and poorly soluble alpha-alumina from aluminium ash. For distinguishing whether bauxite is doped with aluminum ash, the current industry mainly relies on X-ray diffraction (XRD) to carry out phase analysis, and judgment is made by detecting whether characteristic phases of aluminum ash such as alpha-alumina, aluminum magnesium spinel, metallic aluminum, aluminum nitride and the like exist in a sample. However, the XRD equipment is expensive, which greatly increases the cost of alumina factories, is not popular in most alumina production enterprises, and leads to the need of sending samples to third-party detection institutions for analysis, which not only increases the detection cost, but also is more serious in that the detection period is long and the timeliness is serious, and cannot meet the real-time quality control requirements of mass raw material in-factory inspection and continuous production. Disclosure of Invention Aiming at the problems that in the prior art, a bauxite supplier mixes secondary aluminum ash into low-grade bauxite to improve the aluminum-silicon ratio, the existing XRD identification method depends on a third-party detection mechanism to cause insufficient timeliness and alumina factories generally lack XRD equipment, the invention provides a method for identifying that the low-grade bauxite contains aluminum ash. In order to achieve the above purpose, the technical scheme of the invention is as follows: A method for identifying that low-grade bauxite contains aluminum ash, comprising the steps of: s1, primarily judging aluminum ash, namely weighing a bauxite sample to be identified with a certain mass, adding sodium hydroxide in proportion, melting for not less than 20min at 750-800 ℃ in a muffle furnace, taking out, adding deionized water, cooling, transferring the melted cake into a 250mL volumetric flask with hydrochloric acid and boiling water, fixing the volume, cooling to room temperature, standing for more than 30min, and observing whether undissolved precipitate particles exist in the volumetric flask; S2, aluminum ash determination: S2.1, weighing supernatant in the volumetric flask in the step (1), adding lactic acid, shaking uniformly, adding EDTA solution, shaking uniformly, adding xylenol orange indicator, neutralizing with ammonia water until the solution is purple red, immediately adjusting to yello