Thermal Energy and Exhaust Emissions of a Gasifier Stove Feeding Pine and Hemp Pellets

Abstract

This paper presents the results of research on the energetic use of self-combusted hemp pellets and co-firing with pine pellets. The tests were carried out with the use of a boiler equipped with a Lester Projekt Company gasifying burner and an automatic fuel feeding system. The boiler is equipped with an additional heat exchanger that enables the simulation of any heat load. The experimental stand so built guaranteed to obtain results adequate to the real operating conditions. The research material consisted of pellets made of waste biomass of the Futura 75 sowing hemp and pine sawdust pellets. The experiment was carried out in five proportions by mass of mixtures of both fuels (C-hemp, P-pine): 0:100 (P100), 25:75 (C25/P75), 50:50 (C50/P50), 75:25 (C75/P25), 100:0 (C100). For each variant, the following were determined: effective boiler power, boiler energy balance, boiler energy efficiency, the volumetric composition of flue gas (carbon monoxide, carbon dioxide, hydrogen, sulfur dioxide, nitrous oxide), excess air coefficient and the dust content of particle matter—PM10, PM2.5. The heating value was also determined for hemp pellets and pine sawdust pellets, accordingly 17.34 and 19.87 MJ·kg−1. The obtained test results were related both to the volume of exhaust gases leaving the boiler and to one kilowatt hour of heat produced. The obtained test results showed that the boiler fed with pine pellets achieved the highest thermal power (P100)—14.17 kW, while the smallest—hemp pellets (C100)—4.92 kW. The CO2 emissivity increased with the addition of pine pellets, from 26.13 g (C100) to 112.36 g (P100) relating to 1 m3 and from 430.04 g (C100) to 616.46 g (C25/P75) relating to 1 kWh of heat. In terms of dust emissions, it was found that the combustion of hemp pellets and mixtures thereof is a little worse than that of pine pellets.