Abstract
The study attempts to evaluate the impact of combustion of torrefied willow (Latin: Salix viminalis) and palm kernel shell (Latin: Elaeis guineensis) on the heat exchange in a 140 t/h PC boiler through an analysis of 6 cases for different boiler loads (60 %, 75 % and 100 %) and a comparison with coal combustion. The analysis is premised on a 0-dimensional model based on the method presented in [15, 16, 17] and long-standing experimental measurements. Inter alia , the following results are presented: the temperature distribution of flue gases and the working medium (water/steam) in characteristic points of the boiler as well as heat transfer coefficients for each element thereof. The temperature distribution of both fluids and the heat transfer coefficients are similar for all analysed fuels for each boiler load. However, the flue gas temperature at the outlet is higher in the case of torrefied biomass combustion. Due to that, there is an increase in the stack loss, which involves a decrease in the boiler efficiency. The conclusion is that torrefied biomass combustion is possible in a PC boiler without the need to change the boiler construction. However, it would be less effective than coal combustion.
Highlights
Due to the environmental policy of the European Union, there is a steady increase in the use of biomass for energy generation
This study attempts to evaluate the impact of the combustion of torrefied palm kernel shell (PKS) and willow on the heat transfer in a 140 t/h pulverized coal-fired (PC) boiler through an analysis of changes in fuel and boiler load
It was further assumed that thermal efficiency of the boiler heating surfaces is reduced by 20 % compared to coal combustion
Summary
Due to the environmental policy of the European Union, there is a steady increase in the use of biomass for energy generation. Owing to that, it burns longer and the heating conditions in the furnace are more common to coal combustion [10]. Previous work has focused on the possibilities of using torrefied biomass instead of coal in existing boilers without changing the boiler construction. Compared to other types of biomass, it is characterized by a higher LHV, a lower content of ash and a smaller amount of potassium and sodium in ash. It contains less sulphur and chlorine than other types of agro biomass. In the case of thermal calculations of the furnace, the KTI method was used [15, 16, 17], while thermal calculations of the boiler convection part was based on the method presented in [18]
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