Int. Journal of Renewable Energy Development 7 (1) 2018: 1-6 Page | 1 © IJRED – ISSN: 2252-4940, 15 th February 2018, All rights reserved Contents list available at IJRED website Int. Journal of Renewable Energy Development (IJRED) Journal homepage: http://ejournal.undip.ac.id/index.php/ijred Effects on NOx and SO2 Emissions during Co-Firing of Coal With Woody Biomass in Air Staging and Reburning Nihad Hodžić a , Sadjit Metović a, *, Anes Kazagić b a University of Sarajevo, Faculty of Mechanical Engineering,Vilsonovo setaliste 9, 71000 Sarajevo, Bosnia and Herzegovina b Elektroprivreda BiH d.d. - Sarajevo Power utility, Vilsonovo setaliste 15, 71000 Sarajevo, Bosnia and Herzegovina ABSTRACT. Co-firing coal with different types of biomass is increasingly being applied in thermal power plants in Europe. The main motive for the use of biomass as the second fuel in coal-fired power plants is the reduction of CO2 emissions, and related financial benefits in accordance with the relevant international regulations and agreements. Likewise, the application of primary measures in the combustion chamber, which also includes air staging and/or reburning, results in a significant reduction in emission of polluting components of flue gases, in particular NOx emissions. In addition to being efficient and their application to new and future thermoblocks is practically unavoidable, their application and existing conventional combustion chamber does not require significant constructional interventions and is therefore relatively inexpensive. In this work results of experimental research of co-firing coals from Middle Bosnian basin with waste woody biomass are presented. Previously formed fuel test matrix is subjected to pulverized combustion under various temperatures and various technical and technological conditions. First of all it refers to the different mass ratio of fuel components in the mixture, the overall coefficient of excess air and to the application of air staging and/or reburning. Analysis of the emissions of components of the flue gases are presented and discussed. The impact of fuel composition and process temperature on the values of the emissions of components of the flue gas is determined. Additionally, it is shown that other primary measures in the combustion chamber are resulting in more or less positive effects in terms of reducing emissions of certain components of the flue gases into the environment. Thus, for example, the emission of NOx of 989 mg/ 3 n m measured in conventional combustion, with the simultaneous application of air staging and reburning is reduced to 782 mg/ 3 n m , or by about 21%. The effects of the primary measures applied in the combustion chamber are compared and quantified with regard to conventional combustion of coals from Middle Bosnian basin. Keywords: Co-firing, coal, biomass, reburning, NOx emissions Article History: Received: November 5 th 2017; Revised: January 6 th 2018; Accepted: February 1 st 2018; Available online How to Cite This Article: Hodžić, N., Kazagić, A., and Metović, S. (2018) Experimental Investigation of Co-Firing of Coal with Woody Biomass in Air Staging and Reburning. International Journal of Renewable Energy Development, 7(1), 1-6. https://doi.org/10.14710/ijred.7.1.1-6 *) Corresponding author: metovic@mef.unsa.ba 1. Introduction Greenhouse gas emissions as a cause of global warming, primarily carbon dioxide CO2 as well as other undesirable flue gas components such as NOx and SO2, have been enormously increased for the last seven decades, Figure 1a. Various scenarios of temperature increase on Earth up to year 2100, out of which a critical scenario with a 2 °C increase in temperature is set, Figure 1b. Likewise, with the aim of limiting and reducing greenhouse gas emissions as the cause of global warming of the planet Earth, the measures and recommendations expressed through protocols and agreements, such as the Kyoto Protocol of 1997 and the Paris Agreement of 2015/16, will continue to evolve. The intention is to substitute the use of fossil fuels in final energy production through the application of appropriate new technical and technological measures and in particular by the introduction of renewable energy sources, thus reducing the CO2 emissions by 40% by 2050. Multi-fuel operation of coal fired power stations, running co-firing different kind of biomass with coal, is nowadays mainly done to provide fuel mix diversity in order to reduce CO2 emissions, improve security of supply and reduce operational costs by fuel cost optimization. In the last decade, significant progress was made in the utilization of biomass in coal-fired power plants. Over 250 units worldwide have either tested or demonstrated co-firing of biomass or are currently co-firing on a commercial basis, as reported by KEMA (Kema 2009). Coal is often replaced with up to 30% of biomass by weight in pulverised coal based power plants, as in Belgium, Canada, Denmark, Finland, the Netherlands, Sweden, United Kingdom,