Thermodynamic study of NOx and SO2 formation and possible reduction during Pb waste recycling

S. Demčáková : Thermodynamic study of NOX and …, Holistic Approach Environ. 11(2021) 3, pp. 78 - 84 THERMODYNAMIC STUDY OF NOX AND SO2 FORMATION AND POSSIBLE REDUCTION DURING Pb WASTE RECYCLING Silvia Demčáková*, Hedviga Horváthová* * Technical University of Košice, Faculty of Materials, Metallurgy and Recycling, Institute of Recycling Technologies, Slovakia corresponding author: Silvia Demčáková, e-mail: This work is licensed under a Creative Commons Attribution 4.0 International License Professional paper Received: May 13th, 2020 Accepted: June 29th, 2020 HAE-1962 https://doi.org/10.33765/thate.11.3.2 ABSTRACT With the increasing demand for electricity due to the increasing economic boom, there is an excessive production of emissions that natural processes cannot cope with. Fortunately, there are various technological solutions for capturing harmful substances from produced emissions. However, the European Union aims to prevent the formation of emissions in the process of industrial production itself. In order to achieve this, it is necessary to reconcile the interests of individual European Union member states by the implementation of regulations into laws, to monitor short-term and long-term changes in air quality, and also to put into practice increasingly effective methods of capturing emissions from the air. This paper offers an example of thermodynamic calculation of quantities by appropriate software in the process of recycling waste from the metallurgical industry and possibilities of technological improvement in emission reduction. Keywords: air quality, SO2 emissions, NOx emissions, lead accumulators, HSC chemistry 6.1 INTRODUCTION The annual increase in energy demand and consumption forces power plants to produce more and more electricity and heat. Consequently, it also increases the production of more polluting gases, especially in urban areas. In the production of thermal energy, the combustion of fossil fuels produces harmful gaseous chemical compounds, such as carbon dioxide (CO2), sulphur dioxide (SO2), nitrogen oxides (NOx), unburnt hydrocarbons (UHCs), as well as solid particles. Road transport also accounts for a significant proportion, accounting for almost 60 % of emissions in the European Union (EU). SO2 and NOx belong to the gaseous pollutants produced by the combustion of fossil fuels. With secondary pollutants derived from SO2 and NOx, such as sulphuric acid (H2SO4), nitric acid (HNO3), they are harmful to humans and the natural environment [1]. Acid rains containing weak sulphuric and nitric acids enter the soil, leaching out elements such as calcium, manganese, sodium, potassium, 78 S. Demčáková: Thermodynamic study of NOX and …, Holistic Approach Environ. 11(2021) 3, pp. 78 - 84 which significantly deteriorates its quality and consequently the quality of watercourses. As a result of insufficient water supply, trees in forests dry up and die. The adverse effect of acid rains is also reflected in buildings, erosion of statues and corrosion of metal structures. That is why the issue of SO2 and NOx emissions is still very topical - one of the critical problems in pollution control and air quality management. The European Pollutant Release and Transfer Register (E-PRTR) covers the 27 EU member states as well as Iceland, Lichtenstein, Norway, Serbia, and Switzerland. The EPRTR contains data reported from approximately 30,000 industrial installations per year, 65,000 different economic activities, including nine industrial sectors: energy, metal production and processing, metallurgical and chemical industries, waste and wastewater management, paper and wood-processing industries, meat and livestock production, agriculture and other activities [2]. The data from the register is processed into an interactive map of European countries in Figure 1, which provides information on air quality based on the European Air Quality Index. The European Air Quality Index shows the status of short-term air quality at each of over 2,000 monitoring stations across Europe. The index consists of an interactive map of local air quality by measuring stations based on five key pollutants that harm human health and the environment: particulate matter (PM2.5 and PM10), ground-level ozone (O3), nitrogen dioxide (NO2) and sulphur dioxide (SO2). European Union legislation sets air quality standards for short (hourly/daily) and long (annual) periods. Therefore, the index does not reflect the long-term (annual) air quality situation, which may vary significantly [3]. Circles on the map represent the locations of air quality monitoring stations. Based on data from the interactive map, air quality in most of Europe is good. Less satisfactory results are from the southern part of Europe, where air quality is moderate to poor. Good air quality is achieved when the concentration of the five measured pollutants, such as particle matters PM2.5 and PM10, and NO2, O3 and SO2 are ranging between 0 to 10, 20, 40, 50, 100 µg/m3, respectively [3]. Figure 1. Current air quality (20 April 2020, 12:00 h) across all cities based on the European Air Quality Index [3] The Copernicus Atmosphere Monitoring Service (CAMS) provides continuous information on atmospheric composition values in Europe and worldwide [4]. The service analyses the current situation forecasts for the next days, and also shows a look back into the past on air quality and atmospheric composition, ozone and UV radiation, emissions, climate change and solar radiation. The output is, for example, an interactive map of changes in the concentration of ozone, nitrogen and sulphur oxides, carbon monoxide, particle matters PM10 and PM2.5 or secondary inorganic aerosols on the surface of the earth or 500 - 3000 m above the surface in μg/m3. The information about pollution could be viewed in time scale 24 hours before real-time and provides the air quality forecast for the next 96 hours. The output can be also a report on the air condition, which can be generated after registration on the service page with feedback for 30 days. From Figure 2 it is evident that in 2017 the most greenhouse gases in the European Union were produced by Luxembourg (20 t/person/year) and the least by Lichtenstein (5.1 t/person/year) [5]. NOx and SO2 emissions can potentially occur during the hydrometallurgical processing of raw materials/intermediates to obtain useful metals. These may be intermediate products resulting from the processing of various metalcontaining ores, e.g., sulphide concentrates of metals [6]. They also occur, for example, in 79 S. Demčáková: Thermodynamic study of NOX and …, Holistic Approach Environ. 11(2021) 3, pp. 78 - 84 the recycling of electrical and electronic waste or in the recycling of lead-acid batteries, where leaching of stone and slag (lead melting intermediates) in nitric and sulfuric acid produces NOx or SO2 emissions [6, 7]. process of leaching of individual phases of stone and slag containing Pb by (...truncated)