Mining Industry

Analysis of the chemical and mineral composition of rocks and ores

General-Purpose X-ray diffractometer DRON-7(M) and DRON-8

X-ray diffractometers DRON-7 and DRON-8 are efficiently used for qualitative and quantitative analysis of mineral compositions of ores and surrounding rocks, as well as in mineral processing, and for control of mining tailings.

The Chemistry of Coal.

X-ray fluorescence energy dispersive general purpose spectrometer BRA-135F

Coal is the main fuel to produce electricity and to cast iron. World coal consumption and production is more than 9 billion tones. That's why chemical composition of coals is important for both from an environment point of view and contamination of melted metal with harmful impurities. In order to determine ultimate composition of coals, 3 (three) methods are applied: chemical analysis (arbitrary but the most difficult analysis), atomic emission spectroscopy with inductively coupled plasma and X-ray spectroscopic analysis. All these methods give an opportunity to define 13 oxides: SiO₂^, Al₂O₃, Fe₂O₃, CaO, MgO, Na₂O, K₂O, P₂O₅, TiO₂, MnO₂, SrO, BaO and SO₃. The first stage of all methods is a sample preparation - oxidation of coal under analysis. Thereafter, ash dissolving is required for arbitrary analysis and atomic emission spectroscopy; for melting of ash with borax flux – for X-ray spectroscopic analysis.

Methods produce results equal within repeatability and reproducibility; arbitrary analysis of any elements provides for better results.

Coal composition includes sulphur as sulphur of organic compounds, pyrites sulphur and sulphate sulphur. Due to microabsorption effect reliable determination of total sulphur by means of XRF analysis is possible in individual objects only.

Carbon electrodes used as anodes during aluminium smelting include oil coke annealed up to 1200 – 1300 ^OC for the desulfurization. Content of sulphur and some other elements is determined by means of X-ray spectroscopic analysis.

Codes provide for control of composition of coal ash and coke by means of atomic emission spectroscopy and X-ray spectroscopic analysis.

Determination of Germanium in Ash of Coals

X-ray fluorescence energy dispersive general purpose spectrometer BRA-135F

Germanium is a less-common element percentage abundance of which is 1.510-4%. However, content of Ge in ash of hard coals is within the range of 0.001 – 1%, that allows to use coal ash of some deposits for extraction of germanium. In order to determine content of germanium in coals it is recommended to use photocolorimetry with oxidation of coals to prepare samples followed by ash dissolving and separation of interfering elements. Energy dispersive spectrometer BRA-18 of Bourevestnik, Inc. (earlier model of BRA-135) demonstrated the possibility of reliable determination of germanium in coal ash by means of XRF analysis.

Detection of uranium and new nuclear fuel - thorium

Specialized X-ray wavelength dispersive analyzer ARF-7

The main application of ARF-7 Analyzer – detection of uranium and new nuclear fuel - thorium in rocks, ores and process products over a wide concentration range from 10-4 % and higher. Fig. 2 shows a design spectrum of uranium and elements closed to analytical line of uranium (13.618 keV), lines – Rb Кα (13.375 keV) and Sr Кα (14.145 keV) with energy resolution from 40 to 180 eV. It should be noted that resolution of wavelength-dispersive spectrometers as per Soller and Johansson in the first order is about 180 eV in this area of spectrum. Resolution of the best energy dispersive instruments is of the same order. Taking into account that percentage abundance of Rb and Sr in hundred times exceeds percentage abundance of uranium (0.0003%), the advantage of ARF-7 to determine low content of U is clear.

Currently, the procedure for determination of uranium within concentration range of 0.0001 – 10%, based on standard-background method [82] is developed and approved by VIMS Research Institute especially for ARF-7. Noncoherent scattered radiation intensity of X-ray tube molybdenum with Mo anode is used as a background. Fig. 3 and 4 shows calibration results as per standard samples of uranium and thorium ores.

According to the figure, the applied procedure provides for positive determination of uranium within the concentration from 0.0001% and higher. Analogous results were obtained for thorium.

Table contains results of accuracy and repeatability of uranium detection in samples of enterprises by means of ARF-7 analyzer within content range from 3 to 200 g/t in case of multiple measurements by different operators during 2 months. Obtained results demonstrate stability of the instrument operation and adequacy of developed procedure.

Evaluation of accuracy and repeatability of ARF-7 operation during 2 months.
CО	C_A	С_R	ΔC	ПТ	ВА	ПВ	n
СА-1	2.9	2.8	-0.1	1.1	0.52	1.6	31
БИЛ-1	12	13.1	1.2	3.8	1.0	1.9	25
СОП 7-11	19	19.5	0.5	6.1	0.9	3.0	23
СОП 6-11	21	20.0	1.0	5.9	1.4	2.9	21
СОП 8-11	34	35.1	1.1	9.5	1.1	4.8	24
СГ-1	63	63.9	0.9	15.1	2.1	7.6	25
СОП 12-11	96	96.7	0.7	24.0	1.7	11.5	24
СОП 13-11	118	118.9	0.9	21.2	2.2	10.6	26
СОП 14-11	180	182.3	2.3	32.4	4.7	16.2	25
СОП 38-84	200	198.4	-1.6	36.0	4.1	18.0	25

СО – Standard sample
C_A< - Certified concentration, g/t
С_R – Measured concentration (average value), g/t
ΔC - Analysis accuracy (ΔC=СR - CA), g/t
ПТ - procedure accuracy factor (error range at Р=0.95), g/t
ВА - analysis repeatability (root-mean-square deviation σC_R), g/t
ПВ - procedure repeatability factor (error range at Р=0.95), g/t
n – number of measurements

Analysis of Ores of Rare Elements

Specialized X-ray wavelength dispersive analyzer ARF-7

Except uranium and thorium ARF-7 instrument could be applied to analyse rocks for rare and trace elements detection. Table 7 showing analyzer's capabilities contains wavelength l (А), energy Е(keV), Bragg angles q (degrees), instrument half-width D_1/2 (eV) of analytical lines Re, W and Ta and limits of detection of С₀ (g/t) in filler with effective atomic number 11.5 without any interfering elements. The main interfering lines and distance to them DЕ (eV) are given hereto.

During calculation of limits of detection exposure time of 100 s is supposed with usage of X-ray tube with Мо or, in particular cases, with Ag anode in mode of 50 kV/3 kW.

Conditions of Au, Re, W and Ta determination in rocks and ores by means of ARF-7 analyzer
Line	λ (А)	Е(keV)	θ (deg.)	Δ_1/2 (eV)	С₀ (ppm)	Interfering lines, ΔЕ (eV)
Au Lβ₁	1.0835	11.442	9.33	43	2.7	WLγ₁ PbLη	158 94
Re Lβ₁	1.2386	10.010	10.68	39	4.0	HgLα₁ PbLs WLβ₂ GeKα₁	21 42 98 124
W Lβ₁	1.2816	9.6724	11.05	38	5.0	Au Lα₁ ZnKβ₂ ZnKβ₁	41 13 102
Ta Lβ₁	1.3270	9.343	11.45	36	7.9	BiLl HfLβ₂ GeKα₁	77 4 92
Au Lα₁	1.2764	9.713	11.01	38	3.4	WLβ₃ BiLt WLβ₁ ZnKβ₂ ZnKβ₁	104 17 41 56 144
Re Lα₁	1.4329	8.6525	12.37	35	-	WLη ZnKα₁	65 14
W Lα₁	1.4764	8.3975	12.76	34	9.0	NiKβ₅ NiKβ₁	69 134
Ta Lα₁	1.5220	8.1461	13.16	34	15	NiKβ₁ CuKα₁	119 100

As it appears from Table high resolution of analyzer enables elimination of lines aliasing of many interfering elements. In case of absence of interfering elements detection limits for aurum, tantalum, tungsten and rhenium are some g/t. These values may be substantially reduced with increasing exposure time, selection of optimal thickness of primary radiation filter and width of receiving slit.

Taking into account the abundance of interfering elements, distance to their lines and intensity of these lines, Lb₁ lines can serve as optimal analytical lines for Au, Re, W and Ta.

Analysis of the chemical and mineral composition of the intermediate products at various stages of the process

X-ray wavelength dispersive flowstream pulp analyzer AR-35

The main application of analyzer AR-35 for analysis of pulps and solutions is the following:

automated systems of analytical monitoring and automated process control systems of flotation plants of non-ferrous metal polymetallic ore mining and processing enterprises (Fe-Cu-Zn-Pb, Fe-Ni-Co-Ni, Cu-Mo, Mo-W with difficult and branched flotation circuits);
hydrometallurgical limits of extraction and refining non-ferrous, rare and trace elements (Co, Ni, In, Tl, Sc, Y, rare-earth elements, Nb, Ta, Mo, W, Re, U).