LIBS-tehnoloogia rakendamine eesti maavarade ekspress-analüüsiks
The caloricity and the water content are the main quantities which determine the oil shale quality. At the same time during the mining the values of these quantities vary in a wide limit. Obtaining of certificated laboratory data is a time-consuming procedure and thus the results do not reflect the actual situation. Up to now the express-estimation of the quality is based on visual observation and often the results differ considerably from the laboratory ones. These circumstances cause a large loss of the raw material and an increase of the environmental pollution. The aim of the present project is to work out a new method allowing the on-line determination of the oil-shale quality on the running conveyer belt. The method uses the technology of laser induced breakdown spectroscopy (LIBS). In case of LIBS a shot of powerful laser vaporises and ionises the target material. The radiation of the evaporated material enables to find the elemental composition of the target material. LIBS is non-invasive, useable remotely and sensitive for both heavy and light elements. Besides, the method is a high speed one and it demands minimum target preparation. Intensities of spectral lines belonging to different elements are related to the composites of the material studied. Using the relationship between the LIBS spectrum and oil shale composition it is possible to find the oil shale caloricity and water content. Planned activities have two main phases. During the first phase samples of the oil shale powder are tested. The samples with different caloricity are prepared by Estonian Energy Mines. Varying the humidity of samples, LIBS spectra are recorded. Solving a system of equations which links intensities of spectral lines and oil shale composition, the caloricity and the water content are found. The reliability of results obtained by LIBS is compared with those recorded by independent methods used at different laboratories. The second phase deals with the LIBS signal statistics caused by uneven size of oil shale pieces and random orientation their facets. For these studies a laboratory mock up of the conveyer belt will be used. The caloricity is found from the processing of 1000 spectra, each of them is recorded from different pieces and normalised by the zero-order spectrum. Further data treatment is made using methods of chemometry. The recording of spectra and further data processing last few tens of second.