Detailed Operational Mapping of a Grate Fired Biomass Combustion Plant for Improved Combustion Process Control

Abstract

Biomass combustion plants in Norway are facing stricter emission regulations and lower profitability, mostly due to low energy prices. Hence, performance optimization through improved combustion process control and/or retrofitting becomes very attractive to existing plants. However, the trial and error approach usually applied by the plant operator is time and cost consuming, and offers no guarantee of success. Increased combustion process knowledge on the other hand has the potential to provide the necessary input to improved combustion control strategies. The outcome of the improved control strategies can be lower emission levels, improved efficiencies, increased plant capacity or/and reduced maintenance costs. In this study, a measurement campaign was carried out at a 10 MW grate fired plant burning wood briquettes. The aim of the measurement campaign was to map the concentrations of a number of gaseous species inside the combustion chamber, at different locations and at varying operating conditions. Together with continuously measured flue gas concentrations and plant operational data, the measurements provide valuable information for combustion control strategies as well as for validation of modelling approaches, or input to these. Computational Fluid Dynamics (CFD) is the ultimate design tool for bioenergy plant combustion and heat transfer sections, however, cost-effective sub-models need to be developed. The measurement campaign carried out provides useful data for CFD modelling of the plant, both for modelling of the fuel bed, the freeboard and flue gas emission levels.