Environmental aspects of heat recovery systems of boiler plants Nataliia Fialko, Raisa Navrodska, Malgorzata Ulewicz, Georgii Gnedash, Sergii Alioshko and Svitlana Shevcuk E3S Web Conf., 100 (2019) 00015 Published online: 10 June 2019 DOI: 10.1051/e3sconf/201910000015