Possibilities and generated emissions of using wood and lignin biofuel for heat production

Abstract

Energy (including thermal) needs are growing rapidly worldwide thus leading to increased energy production. Considering stricter requirements for the employment of non-renewable energy sources, the use of biofuel in energy facilities appears as one of the best options, having high potential for growth that will increase in the long run both in the Baltic region and the European Union as a whole. This publication investigates the possibilities of using various blends of biofuel containing lignin for heat production and emissions to the air during combustion processes. The paper examines the chemical composition of lignin and bottom ash and explores the impact of a different ratio of lignin in the fuel mixture, the effect of the power of biofuel combustion plants (boilers) and the influence of fuel supply to the combustion chamber on gaseous pollutants (CO, NOx, SO2) and particulate matter emissions. The results of the conducted study demonstrate that, in contrast to pure lignin, the concentrations of alkali metals, boron and, to a lesser extent, nickel and chlorine have increased the most in bottom ash. The use of lignin can effectively reduce the need for conventional biofuel by 30–100% and to increase the temperature of exhaust gases. The lowest emissions have been observed using a mixture of 30% of lignin and biofuel at the lowest range of power (2.5–4 MW). Under the optimal oxygen/temperature mode, carbon monoxide concentrations are approximately 20 mg/Nm3 and those of nitrogen oxides–500 mg/Nm3. Particulate matter emissions reach 150 mg/Nm3, and hence applying air treatment equipment is required.