Citation: Krzywanski, J.; Czakiert, T.; Zylka, A.; Nowak, W.; Sosnowski, M.; Grabowska, K.; Skrobek, D.; Sztekler, K.; Kulakowska, A.; Ashraf, W.M.; et al. Modelling of SO 2 and NO x Emissions from Coal and Biomass Combustion in Air-Firing, Oxyfuel, iG-CLC, and CLOU Conditions by Fuzzy Logic Approach. Energies 2022, 15, 8095. https:// doi.org/10.3390/en15218095 Academic Editor: Dimitrios C. Rakopoulos Received: 26 September 2022 Accepted: 26 October 2022 Published: 31 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Modelling of SO 2 and NO x Emissions from Coal and Biomass Combustion in Air-Firing, Oxyfuel, iG-CLC, and CLOU Conditions by Fuzzy Logic Approach Jaroslaw Krzywanski 1, * , Tomasz Czakiert 2 , Anna Zylka 1, * , Wojciech Nowak 3 , Marcin Sosnowski 1 , Karolina Grabowska 1 , Dorian Skrobek 1 , Karol Sztekler 3 , Anna Kulakowska 1 , Waqar Muhammad Ashraf 4,5 and Yunfei Gao 6 1 Faculty of Science and Technology, Jan Dlugosz University in Czestochowa, A. Krajowej 13/15, 42-200 Czestochowa, Poland 2 Department of Advanced Energy Technologies, Faculty of Infrastructure and Environment, Czestochowa University of Technology, Dabrowskiego 73, 42-200 Czestochowa, Poland 3 Faculty of Energy and Fuels, AGH University of Science and Technology, Mickiewicza 30, 30-059 Krakow, Poland 4 Centre for Process Systems Engineering, Department of Chemical Engineering, University College London, Gower Street, London WC1E 6BT, UK 5 Department of Mechanical Engineering, University of Engineering and Technology, University of Engineering & Technology, Lahore 54890, Punjab, Pakistan 6 Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27607, USA * Correspondence: j.krzywanski@ujd.edu.pl (J.K.); a.zylka@ujd.edu.pl (A.Z.); Tel.: +00-48-343615970 (J.K.) Abstract: Chemical looping combustion (CLC) is one of the most advanced technologies allowing for the reduction in CO 2 emissions during the combustion of solid fuels. The modified method combines chemical looping with oxygen uncoupling (CLOU) and in situ gasification chemical looping combustion (iG-CLC). As a result, an innovative hybrid chemical looping combustion came into existence, making the above two technologies complementary. Since the complexity of the CLC is still not sufficiently recognized, the study of this process is of a practical significance. The paper describes the experiences in the modelling of complex geometry CLC equipment. The experimental facility consists of two reactors: an air reactor and a fuel reactor. The paper introduces the fuzzy logic (FL) method as an artificial intelligence (AI) approach for the prediction of SO 2 and NO x (i.e., NO + NO 2 ) emissions from coal and biomass combustion carried out in air-firing; oxyfuel; iG-CLC; and CLOU conditions. The developed model has been successfully validated on a 5 kW th research unit called the dual fluidized bed chemical looping combustion of solid fuels (DFB-CLC-SF). Keywords: SO 2 ; NO x ; oxyfuel; iG-CLC; CLOU; artificial intelligence; fuzzy logic 1. Introduction The fluidized bed combustion of coal or a co-combustion with the biomass under the oxyfuel conditions, as well as chemical looping combustion (CLC) or chemical-looping with oxygen uncoupling combustion processes (CLOU), seem to be the most promising technologies, with a high application potential which meets the requirements for the reduc- tion in gaseous pollutant emissions [1–3]. Carbon dioxide sequestration (CCS) technologies reduce CO 2 emissions to the atmosphere. The following are distinguished among CCS technologies: pre-combustion capture, oxyfuel combustion, and post-combustion capture. The chemical looping combustion is classified as a CCS technology. Due to the high con- centration of CO 2 in the exhaust gas, the CLC process is less energy-consuming and more effective than other CCS technologies. This is because there is no need to build additional installations for CO 2 separation [4,5]. Two processes are distinguished depending on the Energies 2022, 15, 8095. https://doi.org/10.3390/en15218095 https://www.mdpi.com/journal/energies