CFD Simulations for the Development of a novel Solid Biomass-fired Combustor

The interest of decentralized energy production by means of biomass-fired combustion is increasing in the last few years. This is the result of an increasing CO₂-awarness and high prices for fossil fuels. The use of biogenic combustibles provides many advantages particularly with regard to CO₂-emissions. The development of appropriate designs of combustion systems for these fuels is rather challenging, cost intensive and often time-consuming. Therefore the application of advanced simulation tools like computational fluid dynamics is of vital importance in an early stage.

The aim of this work is to design and devise an innovative combustion chamber with a thermal output of 500kW operating with solid biofuel in form of compressed biomass bales. Several construction relevant facts have to be considered in order to maintain stable bale combustion and minimize gaseous emissions such as VOCs, carbon monoxide and nitrogen oxide. The determination of essential combustion parameters like residence time distribution, mixing behavior of flue gas with secondary air and temperature distribution is accomplished by means of CFD.

With the result of the simulation, a suitable design of the individual combustion zones can be developed applying a repetitive approach. Furthermore, experiments are carried out to enable the validation and calibration of the calculation models and their parameters. Regarding the improvement of the control engineering, prefabricated parts of the plant such as valves for the fresh and recycled air are investigated by CFD and supported by experiments. The results are used to design and improve the control of the fresh and recycled gas-flow, which is important to accomplish a stable combustion performance.