OH LIF-thermometry was applied to premixed ethanol flames at atmospheric pressure in a burner for three flame conditions. Flame temperatures were simulated from energy equation with PREMIX code of CHEMKIN software package for comparison. A kinetic modeling based on a model validated through chemiluminescence measurements and on a set of reactions for nitrogen chemistry was evaluated. Marinov's mechanism was also tested. Sensitivity analysis was performed for fuel-rich flame condition with Φ = 1.34. Simulated temperatures from both reaction mechanisms evaluated were higher than experimental values. However, the proposed kinetic modeling resulted in temperature profiles qualitatively very close to the experimental.

Uma modelagem cinética foi avaliada para reproduzir a quimiluminescência experimental dos radicais excitados OH*, CHO*, CH* e C2* formados na combustão de C2H2/O2 em uma câmara fechada. Um mecanismo reacional com 37 espécies e 106 reações elementares foi validado para a combustão de C2H2/O2 com fi=1.00 e fi=1.62, através das medidas de quimiluminescência. Para isso foram incluídas reações de formação e de decaimento dos radicais excitados. As simulações foram realizadas com o pacote KINAL; o programa DIFF foi utilizado para resolver as equações diferenciais ordinárias e o programa ROPA para realizar a análise das velocidades de produção. Houve uma boa concordância entre os perfis de quimiluminescência experimental e simulado de todos os radicais e para ambas reações. Os resultados mostraram que o CH tem um papel central na formação dos radicais. As reações: H + O2 = OH* + O; CH + O = CHO*; C2H + O2 = CH* + CO2 e CH2 + C = C2* + H2 são as principais rotas reacionais para reproduzir os perfis experimentais.

Kinetic modeling to reproduce the experimental chemiluminescence of OH*, CHO*, CH* and C2* excited radicals formed in C2H2/O2 combustion in a closed chamber was evaluated. A reaction mechanism with 37 species and 106 elementary reactions for C2H2/O2 combustion at phi=1.00 and phi=1.62 was validated through chemiluminescence measurements, where formation and decay reactions of excited radicals are included. KINAL package was used for simulations. Ordinary differential equations were solved by the DIFF program and production rate analysis were acquired by the ROPA program. There was good agreement between experimental and simulated chemiluminescence profiles of all radicals for both combustions. The results showed CH has a meaningful role in the production of excited radicals. Reactions: H + O2 = OH* + O; CH + O = CHO*; C2H + O2 = CH* + CO2 and CH2 + C = C2* + H2 were the main reactions paths used to reproduce the experimental profiles.

Neste trabalho, realizou-se o estudo dos materiais particulados emitidos na combustão de óleo residual do tipo 4B e na requeima de gás natural aplicada à combustão deste óleo numa fornalha em escala piloto. Os tamanhos, as morfologias e a distribuição dos elementos inorgânicos nas partículas foram analisados por microscopia eletrônica de varredura acoplado a um espectrômetro de energia dispersiva de raio-X (EDS). Foram observados três tipos de partículas: cenosferas esféricas, compactas e lisas de 0,6 a 1,5 mim; cenosferas com poucos poros de aproximadamente 10-20 mim e cenosferas porosas na faixa de 20-50 mim. O particulado emitido na combustão de óleo residual apresenta predominantemente as pequenas cenosferas compactas e lisas, enquanto que o emitido no processo de requeima mostra preferencialmente as cenosferas maiores e porosas. As microanálises de EDS mostraram principalmente Al e Si nas partículas menores e S e V nas cenosferas com poucos poros e nas cenosferas porosas e maiores.

In this work, a study of the particulate matter emitted from standard residual oil combustion and from natural gas reburning during oil combustion in a pilot scale furnace was carried out. The sizes, morphologies and chemical element distribution of particles were analyzed through scanning electron microscopy coupled to an X-ray energy dispersive spectrometer (EDS). The microscopy results show three sorts of particles: spherical, very compact and smooth cenospheres with sizes of 0.6-1.5 mum; cenospheres with a few pores with sizes of 10-20 mum and larger porous cenospheres with sizes of 20-50 mum. The particulate emitted from standard oil combustion shows predominantly spherical and very compact small cenospheres, with a smooth surface, while those emitted from the reburning process present a majority of larger porous cenospheres. The EDS microanalysis showed mainly Al and Si in the smaller cenospheres and mostly S and V in the cenospheres with a few pores and in the larger porous cenospheres.

Neste trabalho, realizou-se um estudo da formação de partículas de fuligem durante a combustão de misturas de C2H2/O2 em diferentes razões C/O. A evolução temporal e a fração de volume das partículas de fuligem foram obtidas através da extinção de um feixe de laser. Constatou-se que o tempo total de formação da fuligem nas chamas de C2H2/O2 com razão C/O > 0.75 ou de C2H2/O2/Ar com razão C/O = 1.00 é de cerca de 3.0-4.0 ms, após o início da reação. O máximo de emissão dos radicais excitados e o máximo da pressão nestas reações, ocorrem praticamente neste mesmo intervalo de tempo. Observou-se a formação de partículas de fuligem compactas e aproximadamente esféricas com 60-150 nm de diâmetro. Entretanto, os agregados não são compactos e mostram uma estrutura de rede que se assemelha a de um aerogel.

An experimental study of soot formation in C2H2/O2 flames at different C/O ratios in a closed chamber was carried out. The evolution temporal behavior and the volume fraction of soot particles were determined by laser extinction. It was found that total time for the soot formation phenomenon in flames from C2H2/O2 with C/O ratio > 0.75 or C2H2/O2/Ar with C/O ratio = 1.00 was around 3.0-4.0 ms after ignition. At almost the same time the excited radicals reached their maximum emission intensity and the gases under combustion reached their maximum pressure. The micrographs show compact and approximately spherical soot particles with diameters within 60-150 nm. However, soot aggregates are not compact and they present a netlike structure similar to that of an aerogel.