Modelling of Biomass Combustor: Final assignment energy from biomass

Modelling of Biomass Combustor: Final assignment energy from biomass

Ammerlaan, R.
Van den Hill, E.J.
Kaas, A.W.S.
Verburg, M.W.

Mechanical, Maritime and Materials Engineering

Process and Energy

2010-04-12

In this study a 1.1 MW fluidized bed combustor is modeled. A literature study is performed on aspects which determine the characteristics of the combustor. A model is set up and calculations for the design of the Fluidized Bed Combustor (FBC) are performed. Characteristics are calculated for the Fluidized Bed (FB) and Freeboard Zone (FBZ). Matlab is used to perform simulations and generate specific parameters for the design of the FBC. The report starts with an introduction on the FBC, from the sustainable and technological point of view. In Chapter 1 a short overview of the history of biomass is given, from where the link to the FBC design is made. The general aspects of a FBC are stated. Chapter 2 shows the results of the literature study. In particular attention is paid to the formation of greenhouse gasses, which play an important role in power generation and thus in FBC’s. Possibilities to reduce these pollutants are mentioned. It is explained why the formation of thermal NOX is primarily dependent on the temperature and stoichiometry. In the model the formation of thermal NOX is neglected, since the reaction temperature is too low to generate significant amounts of NOX. Fuel NOX seems to contribute in a larger amount to the NOX formation, but the contribution is still unsignificant in the model. The formation of Carbon Monoxide (CO) plays a more important role. This formation is directly related to the mixing of fuel and air at sufficient temperature. To reduce the CO formation, an optimal air to fuel ratio and a greater residence time are suggested. In Chapter 3 the design of the model is presented. This chapter starts with the outcome of the literature study, where the principles of the FBC are described. After that, a list of assumptions is presented. The overview of the assumptions is specified and worked out for the different reactor zones in the FBC: the Fluidized Bed, the Splashing Zone and the Freeboard Zone. Chapter 4 elaborates on the air speed in the FBC. The air speed affects important running characteristics such as the behavior of the sand particles in the bed, the burning efficiency and the formation of greenhouse gasses. It is also an important parameter for the determination of the dimensions of the FB and FBZ. This chapter concludes with a section including numeric values and results of the calculations are presented, which in turn are used for the calculations on the combustor model. The complete model is presented in Chapter 5. Detailed calculations on the model are explained, starting with the combustion reactions. This model description includes molar ratio’s, caloric values and mass flows. Furthermore specific energy balances are shown for each section of the combustor. Finally, the wall losses are defined. A summary of the results can be found in Chapter 6. Results of energy balances and efficiency are presented and a clarification of the temperature profile is given. This document concludes with a discussion on the obtained results and the limitations of the model.

biomass
combustor

http://resolver.tudelft.nl/uuid:0fc53a4b-5339-4af4-9dc7-20a4203570c4

Delft University of Technology

Institutional Repository

report

(c) 2010 Ammerlaan, R.; Van den Hill, E.J.; Kaas, A.W.S.; Verburg, M.W.