Heating and emission properties of waste biomass in burner furnace

Abstract

The issue of energy utilization of waste material is a subject of the International and European policy in the field of waste management. The article responds to constantly increasing requirements for the production and operation of devices for energetic utilization of waste. The use of these materials as a fuel in small combustion plants faces many technical and economic challenges. Stricter legislative requirements will focus more on the quality of used biofuels and operating conditions of combustion devices.Other authors show good results during wood biomass combustion in small combustion devices (Johansson et al. 2003;Eskilsson et al. 2004). It is vital to know the properties of biofuels, which sufficiently characterize them. For larger combustion devices equipped with gas cleaning and combustion process control, fuel quality is not so critical. It is important to recognize two types of pellet fuel: for industrial and small residential combustion devices (Olsson et al. 2003;Obernbergera, Theka 2004).The options for reducing emissions of incomplete combustion process include uniform fuel supply, sufficiently high temperature in the combustion chamber and sufficient intake of secondary or tertiary air or choice of optimal moisture of biofuel. The main fuel parameters (net calorific value, water content and energy density etc.) affect design of the combustion device and its control in many ways. For example, water content in biomass has an influence on adiabatic temperature of combus- Utilization of waste suitable as a fuel for small combustion devices is a very important issue. Therefore, this article analyzes selected waste materials from agriculture and maintenance of municipal vegetation. The pellet samples from composting had very high ash content (22.39 and 36.85% wt.), which resulted in low values of net calorific value (12.66 and 10.24 MJ/kg), but also in bad properties of these samples in high concentration of harmful emission. Other problematic fuel samples were pellets from maintenance of city vegetation and reed canary grass, for which high concentration of carbon monoxide was measured during combustion process. The device used for these experiments is based on burner furnace. Combustion conditions could be improved by more uniform fuel supply to the burner and better control of combustion air. Boiler with advanced combustion control can reach better results during combustion process. Results in this article are valid for tested materials combusted in simple pellet burner with limited ability to control combustion process.