Agro Fossil Free - Energy efficient straw boiler with low nox emission

General Description

Increased use of renewable energy is important for fulfilling EU’s climate and energy goals. Biomass e.g. straw can contribute to the substitution of fossil energy. However, straw combustion might cause environmental problems due to harmful emissions of particles, NOx etc. The aim of the project described in this paper is to develop and document a new boiler design with high energy efficiency and low NOx emission. The boiler is designed for two‐stage combustion with two combustion chambers. Compared to a standard straw boiler significant reduction in NOx can be obtained. Partial recirculation of flue gas can increase the NOx reduction. Stable fuel intake, air staging strategy by control and regulation of primary air supply, secondary air and flue gas recirculation are key factors to obtain high energy efficiency and low emissions at the same time. This work deals with primary measures for NOx reduction with focus on controlling the combustion process. Secondary measures with treatment of the flue gases, e.g. injection of ammonia or urea may be appropriate in other cases.

The project is a collaboration between the company Maskinfabrikken REKA A/S and Aarhus University, Department of Electrical and Computer Engineering This paper presents the status and obtained results of the project.