Uso de ferramentas estatísticas básicas objetivando a redução do nível de flúor em reservas de carvão mineral

Abstract

Through the coordinated and guided use of statistical tools, combined with a detailed study of the flow of disposal, homogenization, transport and loading of the coal produced, it was possible to reduce the level of fluor and optimize the mineral coal reserve of a large Brazilian mining company in Mozambique. To develop this mixture of different coals and thus generate a new product, low fluorine coal to be destined for the Chinese market, all the processes after the plant had to be changed. It was necessary to fragment the production of pre-selected coals to compose this new product, generating great challenges due to the limited space in the plants' storage yard, combined with the need to homogenize piles of different fluor levels, seeking to optimize the coal reserve without exceed the limit required by the customer. All production was sampled and the results were monitored through a control chart, aiming to increase the assertiveness of the project, the samples were sent to different laboratories of global reference and their results were validated through the Students t test. The homogenization process was necessary to be applied in several stages of the formation of the ships, starting with the loading of the trains that transported the coal from the city of Moatize to the port in the city of Nacala. In the original process, the locomotive was composed of only one type of coal derived from only a single pile produced. However, to keep the level below 200 ppm, it was necessary to change this process, starting to load the locomotive with stacks of opposite fluor levels, forming a locomotive of known average fluor.7 For the formation of ships in the port of Nacala, it was also necessary to change the process of formation of piles and loading of ships. In the original process, all locomotives destined for the ship were unloaded, forming only one pile, which would be taken up again in the ship's loading process. However, to form a low-fluor ship with a high homogenization index, we divided the locomotives into two piles in different yards, thus enabling the simultaneous resumption of piles, considerably increasing the homogenization of the low-fluor ship destined for the Chinese market. The Chinese market is quite challenging due to restrictions regarding the level of fluorine in imported coals, especially in the south of the country where the water already has a high value of diluted fluorine. The results obtained in the monograph demonstrate the potential that can be achieved with the application of statistics in industrial processes, 2021 ended with 6 ships unloaded in Chinese ports and an exclusive low-fluor coal contract for the year 2022.