Mathematical modelling of straw combustion in a 38 MWe power plant furnace and effect of operating conditions

As one of the most easily accessible renewable energy resources, straw can be burned to provide electricity and heat to local communities. In this paper, mathematical modelling methods have been employed to simulate the operation of a 38 MWe straw-burning power plant to obtain detailed information on the flow and combustion characteristics in the furnace and to predict the effect on plant performance of variation in operating conditions. The predicted data are compared to measurements in terms of burning time, furnace temperature, flue gas emissions (including NOx), carbon content in the ash and overall combustion efficiency. It is concluded that straw burning on the grate is locally sub-stoichiometric and most of the NO is formed in the downstream combustion chamber and radiation shaft; auxiliary gas burners are responsible for the uneven distribution of temperature and gas flow at the furnace exit; and fuel moisture content is limited to below 25% to prevent excessive CO emission without compromising the plant performance. The current work greatly helps to understand the operating characteristics of large-scale straw-burning plants.