Waste to Product or Process – Industrial Symbiosis Examples of Aurubis Bulgaria Copper Smelter

Verka Stoinaova, Lukan Gerov, Krasimira Nedeleva, Asen Saraev, Vanya Stoyanova

In recent years, recycling and recovery of by-products as well as waste reduction have become increasingly important topics for the industry. Waste reduction and recycling is often achieved by managing or treating various intermediate and waste materials in order to produce usable and valuable materials. This paper describes two cases of environmentally sound processes, which have been implemented recently in Aurubis Bulgaria – a custom copper smelter and refinery. The first case is related to the measures taken for the improvement of the air quality in/around the smelter. In order to improve the capture of fugitive emissions and to further reduce the overall emissions from the smelter, a number of improvements were made in the ventilation system over the flash smelting furnace, Pierce Smith converters and in the space under the roof. To treat the increased volume of ventilation gases an additional gas cleaning system had to be added to the existing one. Sulfacid technology was chosen because of the final product, it produces weak sulphuric acid (10 – 13 %) with technical purity, which is used in the sulphuric acid plant for dilution of the acid from the absorption towers. As a comparison, the existing off-gas treatment plant generates gypsum as a waste product. Therefore, with this new technology SO2-containing gases, which have not been fully utilized before are converted into a product with added value rather than gypsum. The main environmental benefits of the implemented technology are: • Utilization of waste gases • Generation of a useful product • Use of a zero-waste technology The second case includes a deep preliminary investigation of the impurities behaviour in the existing refinery in Aurubis Bulgaria. The internal study was a response to the ever increasing complexity of the raw materials and anodes as a consequence. The goal was to preserve the operational capacity, the process effectiveness and the product quality, while ensuring full compliance with the environmental standards. An analysis of the refinery operation showed that spent electrolyte, which was usually neutralized in the waste water treatment plant (WWTP), could be partially recycled back to the refinery circulations. The results achieved during the tests confirmed the hypothesis that the refinery can both operate and control the parameters by recirculation of the waste spent electrolyte. This modification led to: • Reduction of the amount of waste water, which needs to be treated in the WWTP, resp. decrease of the operational expenditure at the WWTP • Decrease of the quantity of generated gypsum for landfilling • Return to the process and subsequent extraction of part of the valuable components (Cu and sulphuric acid) • Increased flexibility of the refinery in relation to impurities management.