1. Soot Formation in the Diffusion Flames of Eugenol, Anisole and Some Hydrocarbon Liquid Fuels A. R. Lea-Langton 1 * F. A. Atiku 1, K.D. Bartle 1, J. M. Jones 1, M. Pourkashanian 2, and A. Williams 2 1 Energy Research Institute, SPEME, University of Leeds, UK 2 Energy Technology and Innovation Institute, SPEME, University of Leeds, UK * Email: pmfaa@leeds.ac.uk Introduction Particulate matter and other emissions produced from biomass and bio-oil combustion are associated with adverse health and changes to atmospheric chemistry. The nature and composition of the bio- derived soot and aerosols is different from hydrocarbon soot. Conventional soot mechanisms do not fully describe soot formation from the biomass and bio-oil due to the role of oxygenates in bio-fuels. Objectives To generate a fundamental base of knowledge of the size, chemical and physical properties, formation rate and basic mechanism of biomass derived soot. To examine the physical and chemical properties of soot derived from different biomass-oils and compare with biomass-oil derived soot and soot from hydrocarbon flames. Determination of sooting tendencies in the flame environment as a function of temperature, residence time and burning velocity, including investigation of gas-phase composition on soot yield. To study the morphology of microscopic soot and laminar burning velocities for measuring sooting propensities of the burned fuel. To investigate the structures of the flames and explore soot structure evolution from burning biomass oil and petroleum based products. Wick Burner tests Soot Characterisation Sooting propensities Figure 9: Scanning electron microscopy (SEM) of soots Figure 7: Pyrolysis-gcms of anisole soot Conclusions Figure 10: Transmission electron microscopy (TEM) of soots Figure 8: Particle size distribution from anisole wick burner flame Soot formation mechanism Figure 6: filtered flames for different oils Fuel B pt 0c Smoke Point, mm Mass burning rate, mg/s C/H ratio Emission factor mg soot/ gfuel n-heptane98.413.54.60.440.25 n-decane174.127.05.40.450.18 furfural161.716.04.81.2527.0 anisole15411.04.70.87517.1 Eugenol2546.51.40.83132.2 furfural/eugenol 50/50 -123.1-52.2 Figure 4 : Smoke point apparatus Analytical scale combustion has employed a basic wick burner combustion test of biomass pyrolysis products and hydrocarbon oils. Fuels tested included: Hydrocarbons: n-heptane, decane Biomass derived oils: anisole, furfural and eugenol. Blends of these fuels were also tested. Characterization of flame and burning particles included:  Mass flow rate  Photography  Particle range size analysis (DMS)  Opacity Experimental Results The origin of soot in biomass or heavy fuel oil flames has been investigated via Pyrolysis-GC-MS. Soot formation, mechanism shows how soot properties and kinetics are related to reaction conditions. The use of kinetic modelling improves understanding of the fundamental chemistry in biomass-oil combustion and can be applied to mitigate emission levels. The presence of oxygen in the bio-oils leads to changes in the combustion mechanism compared to hydrocarbon fuels. Consistent particle size results are seen by electron microscopy and on-line particle size DMS analysis. The degree of structural order within the soot is to be analysed further using high resolution TEM.. Combustion of fuels leads to the emissions of flue gases and particulate components including polycyclic aromatic hydrocarbon (PAHs). The origin of PAH during pyrolysis of biomass derived oils has been investigated. The mechanism of black carbon (soot) emanating from the burning has been observed to follow the following mechanism; ‘Hydrogen Abstraction Carbon Addition’ HACA as in case of decane and heptane Thermolysis of phenols derived from lignin – generating a single and most importantly two ring aromatics via CPD i.e instead of dehydrogenation and demethylation, the instantaneous primary reaction is decarboxylation or elimination of CO 2 to produce cyclopentadiene It has been also found that, eugenol as a function of lignin, shows on oxidative pyrolysis it produces mainly benzene, toluene and C-2 benzenes, while anisole and furfural assumes to follow similar route of producing PAH. Table 1 demonstrates the boiling point, smoke point, mass burning rate, carbon to hydrogen ratio and soot emission factor for all the fuels upon combustion. It can be seen that, eugenol produces least smoke point value of 6.5 while n-decane has the highest value up to 27, indicating that n-decane produces less soot than the eugenol which was the highest soot producer. Figure 5 shows the Van Krevelen analysis of the soot samples based on the elemental analysis. Clearer differences are observed between the fuels which are associated with the initial degree of atomicity. Figure 6 compares images of the flames for different fuels. Clear differences are observed between the hydrocarbon fuels and the oxygenbated bio-oils, of which eugenol was observed to be highly sooting. A filter was used to observe the change in reaction zones. The order of sooting propensity is heptane<decane<anisole=furfural<eugenol A high speed soot sampling system was developed in order to collect samples for Transmission Electon Microscopy (TEM), as shown in Figure 3. The soot sampling system allows rapid and contolled collection of soot at different flame heights. The set-up comprises of a wick burner as a source of flame and TEM grid holder. The grid holder is attached to a compressed air driven piston. A magnetic control system is used. Py-GC-MS analysis showed a wide range of oxygenated species, an example is shown in Figure 7. These species are consistent with the model proposed earlier. DMS particle size analysis showed peak particle size to be <200nm as shown in Figure 8. These are easily respirable. Acknowledgements Measurement of sooting tendencies was achieved using Seta smoke point apparatus as shown in Figure 4. Soot Characterisation Detailed soot characterisation was performed using the following techniques: Electron microscopy- SEM and TEM to analyse the particle size and structure. Py-GC-MS for at a range of pyrolysis temperatures to investigate soot formation routes. PAH analysis to assess adsorbed species on the particulate. Elemental analysis to evaluate relative composition od Carbon, Hydrogen, Oxygen, Nitrogen. Thermogravimetric analysis to indicate relative amounts of volatile organic species (organic carbon) and elemental carbon (black carbon). We would like to thank EPSRC Supergen BioEnergy for support and also Dr Nicole Hondow and Dr Adrian Cunliffe for technical assistance Analysis using electron microscopy showed particle sizes typically in the range of 10nm- 60nm. These particles had agglomerated to form chains, consistent with the larger particle sizes observed by DMS analysis.. Onion-like structures typical of graphite were observed using TEM. Further data analysis is on-going to establish any differences between the soot formed from different fuels (Figure 10) Table 1: Fuel properties and burning characteristics Figure 5 Van Krevelen analysis of soots Figure 1: Proposed soot formation mechanism Figure 3: Schematic of soot sampling Figure 2: wick burner tests Chimney Scale Guide Gallery Candle screw Candle