Preparation of Lime by Roasting the Limestone Deposits of Strezovci (Republic of Kosovo) and Its Use for the Aluminothermic Production of Calcium Metal

The goal of producing and processing limestone ore (mostly CaCO3 ) is to obtain high-quality refractory materials based on lime (CaO). Lime is the raw material for obtaining calcium metal as a strategic and fundamental component in lead metallurgy (production of refined lead, Pb-Ca alloys in the battery and cable industry, ferroalloys production with the addition of silicon and calcium, production of alloy steel and high-quality steel). This paper explores the preparation of lime by roasting the limestone deposits of Strezovci (Republic of Kosovo) and its use for obtaining calcium through the aluminothermic process. Through research and analysis of the chemical composition of certain types of lime, its suitabi- lity for obtaining calcium metal was determined, and by analyzing the samples of the slag, determined was the possibility of its use in the production of fire-resistant cement for which the evaluation is needed. Based on previous research, the following was chosen: optimal composition of the cast, volume of added reducing agents, and conditions of the reduction process performance: temperature-time and initial vacuum. According to the authors’ knowledge, not one Southeast European country has applied this method, and it includes the use of by-products (slag), which can cause environmental pollution. The goal of this research was to prepare lime by roasting limestone of domestic origin in order to obtain calcium metal through the aluminothermic process. The procedure of calcium metal production includes the following operations: decarbonatization of limestone ore (CaCO3 ), grinding of the obtained lime (CaO), homogenization of CaO and alumina, agglomeration, and aluminothermic reduction in vacuum furnaces. For the efficiency of the process, the most important technological operations are decarbonatization and reduction, provided the other operations are performed correctly. The estimated total world capacity for production of calcium metal is 25 000 – 27 000 tons/year. The mass fraction of calcium in manufactured calcium metal is minimum 97 %. In recent years, some western countries are producing calcium metal with 99.99 % of Ca, through redistillation and zonal refining. In the countries of Southeastern Europe and former Yugoslavia, the largest consumers were lead metallurgy, battery and cable industries, the steel industry and the producers of friction alloys. Based on the given results, the manufactured calcium metal can also be placed on other world markets. These studies have shown that the preparation of lime by roasting the limestone depo-