EXPERIMENTAL STUDY ON THE COMBUSTION OF SEVERAL VEGETABLE OILS IN AN EMULSION BURNER: EFFECT OF FATTY ACID PROFILE OF VEGETABLE OILS ON COMBUSTION PROCESSES

摘要

The use of vegetable oils as a fuel in burners is an alternative which offers certain advantagesrncompared to their use in engines, the most important being that existing facilities can be switched from biofuels tornoils by simply varying the burner adjustments. In addition, it is possible to use current vegetable oil extractionrnfactories. Moreover, certain stages of the vegetable oil refining process may even be removed. Herein, we present thernresults obtained in the combustion of six different vegetable oils in an emulsion burner for heating purposes. Therndifferences observed in the combustion processes of these oils with regard to gas emissions and energy efficiencyrncould not be explained by only taking into consideration conventional parameters such as density, kinematicrnviscosity, elemental analysis, HHV and LHV among others. At this point, we reasoned that knowledge of the fattyrnacid profile of the oils might help us to understand their different behaviour in the combustion process. To explorernthis possibility, we studied six vegetable oils: rapeseed, soybean, sunflower, coconut, palm, and a commercialrnmixture-seed. To study the relationship of the fatty acid composition with energy efficiency and gas emissions, workrnwas conducted in six stages. First, we described the use of vegetable oils as a fuel. The fatty acid composition of allrnthe oils was then determined by high-resolution 1H NMR spectroscopy. Third, we developed an experimental facilityrnto burn the oils, said facility comprising a steel-sheet air-cooled constant pressure combustion chamber. The facilityrnis equipped with an analyser which allows gas emissions from the combustion process to be measured. We thenrncarried out 54 tests (nine for each oil), varying fuel flow in the emulsion and excess air in the burner. Experimentalrntesting was performed following well-defined conditions to ensure reproducibility of assays. Finally, the link betweenrnthe fatty acid composition and the result of the combustion process in each vegetable oil was analysed.