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W1P001 EFFECTS of BURNING RENEWABLE FUELS in a VARIABLE GEOMETRY LOW SWIRL INJECTOR OPERATED in a BOILER ENVIRONMENT Vincent G

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W1P001 EFFECTS OF BURNING RENEWABLE FUELS IN A VARIABLE GEOMETRY LOW SWIRL INJECTOR OPERATED IN A BOILER ENVIRONMENT Vincent G. McDonell, Nathan Kirksey, University of California, Irvine, United States At the University of California, Irvine Combustion Laboratory a low swirl injector with a variable blockage is being used in a boiler to fire varying compositions of renewable fuels. The goal is to develop a relationship between the emissions and stability of the burner to the blockage and fuel composition. To change the geometry of the injector, or the swirl number, an adjustment is made to the blockage in the center of the injector. In order to determine how the flowfield or turbulence levels have changed with the different blockages a method of laser imaging called reactive particle image velocimetry is used. From the developed vector fields a wealth of information can be gathered, including: the turbulence intensity, the flame height, and the turbulent flame speed. Compiling all this information results in a turbulence level for each blockage, as well as, changing flame heights; in addition, the turbulent flame speeds for the differing fuel compositions can be determined as a by-product. Current research aims to investigate the improvements on stability of the flame resulting from adjustments to the blockage on the low swirl injector. The idea is that by using a larger blockage, which will lower the injector speed, it will bring a slower burning biogas fuel closer to the injector point thus improving stability. Another important tool used when determining stability is a fiber optic probe. The probe can measure the flame luminosity and fluctuations in real time to give feedback in regards to the stability. As a flame is leaned or moved closer to blowoff the flickering increases while the luminosity decreases this can be correlated to the stability of the flame through the use of the fiber optic probe. Emissions data is an essential part of the testing, as such; an emission analyzer tracks the changes in emissions due to the wide variety of blockages, fuels, and equivalence ratios present during the testing. Lastly, the current development is in developing a speed of sound gas composition sensor. This sensor was used to correctly identify binary hydrocarbon mixtures in the past; the future goal is to outfit the device with more sensors in order to identify almost any fuel composition for use as an indicator for industrial applications. Industrial boilers operating on landfill gas do not know the composition of the fuels they are burning during the majority of their operation; this sensor would be a low cost device to ensure proper tuning of the boiler for emissions and stability depending on the actual fuel composition. [email protected] W1P002 OXYGEN-ENRICHED CO-COMBUSTION OF BIOMASS FOR CCS APPLICATIONS William Nimmo, Mohamed Pourkashanian, Sam Pickard, Leeds University, United Kingdom Biomass combustion and Carbon Capture and Storage (CCS) individually represent significant options for decarbonising the power generation sector and when combined may permit a carbon-neutral or even carbon-negative process. Despite this potential, little research has been published that examines the combustion of biomass in atmospheres with application in CCS processes. This work reports on laboratory-scale and bench-scale testing of biomass and coal combustion in atmospheres enriched in O2 and CO2 which are relevant for retrofitting power stations for oxyfuel combustion. At bench-scale, thermogravimetric analysis shows substituting N2 as the combustion diluent with CO2 has little impact on the combustion properties of the fuels but that increasing the O2 concentration accelerates combustion of coal and biomass chars. Results from cofiring three biomasses with coal at 20kW scale suggest substitution of N2 with CO2 significantly reduces temperatures, carbon burnout and emissions of NO while combustion in O2-enriched conditions has the opposite effects. Emissions of NO and SO2 were found to reduce compared to air in combustion atmospheres enriched with O2 and CO2 while combustion temperatures and carbon burnout slightly increased. Comparing a typical oxyfuel combustion atmosphere (30% O2 in CO2) with combustion in air finds that the former is more reactive for all fuels during both the combustion of volatiles and char oxidation stages during Thermo-Gravimetric Analysis (TGA) and that the elevated [O2] particularly accelerated the char-oxidation stage of the combustion process. Little difference was observed when N2 was replaced with CO2 as the diluent since at temperatures typical in TGA gasification reactions have little impact and the increased heat capacity of the atmosphere is negated by the TGA control system. Unstaged cofiring (15%th) of each of the biomasses at 20kW scale showed that the heat capacity of the fluid was important and temperatures in CO2-enriched combustion atmospheres were lower than those that were N2-based, delaying combustion and reducing NO emissions. O2-enrichment and biomass blending were both observed to improve carbon burnout with the former tending to increase NO emissions, while biomass blending tended to effect slight reductions compared to coal firing mainly due to changes to local [O2] and temperatures near the burner. Emissions of SO2 were reduced during cofiring and during combustion in atmospheres enriched with CO2 and O2 though a full sulphur balance could not be performed to suggest further reasons for this. SEM images of ash samples support the relative combustion efficiencies with a increasing tendency for smaller, spherical particles in the ash with increasingly efficient combustion observed during O2-enrichment. [email protected] W1P003 EFFECT OF CATALYTIC PRE-COMBUSTION ON FLAME STABILITY IN HIGHLY CONCENTRATED CO2 Toshinori Nagai, Takeshi Yokomori, Keio University, Japan Oxy-fuel combustion attracts attention as an effective solution of reducing CO2 emission. However, highly concentrated CO2 destabilizes the combustion. In this study, the catalytic pre-combustion was used for the improvement of the flame stability in highly concentrated CO2. The experiments and numerical calculation were performed to elucidate the influence of the catalytic pre-combustion on the flame stabilization. The burner consisted simply of a Pt catalyst pipe with 5 mm in diameter confined by a quartz tube with 40 mm in diameter. The CH4/O2/CO2 mixture was jetted out from the Pt catalyst pipe. The mixture inlet velocity V and equivalence ratio f were varied. For comparison, the CH4/O2/N2 mixture was also used. The volumetric ratio of O2 to CO2 (or N2) was 3:7. The O2/CO2 (or N2) mixture flowed at 0.2 m/s in the circumference of the jet. In the numerical calculation, a two-dimensional axisymmetric model was implemented into the CFD code ANSYS-Fluent 14.0. Gas phase and surface reaction mechanisms consisted of 57 reactions involving 18 species and 24 reactions involving 11 species, respectively. In addition, DO model was adopted as a radiation model and the emissivity of the gas phase was calculated with WSGG model. The thermal conduction of the catalyst was also taken into account. In the experiment, the blow off velocity of the flame stabilized at the downstream of the catalyst typically increased with increasing the equivalence ratio. The blow off velocity in the CH4/O2/CO2 mixture showed lower than that in the CH4/O2/N2 mixture even with and without the catalytic combustion. The blow off velocity with the catalytic combustion was lower than that without the catalytic combustion at the lower equivalence ratio. This is because the catalytic combustion consumed reactants, so that the reactants were insufficient to sustain the flame at the downstream side of the catalyst. On the other hand, the blow off velocity with the catalytic combustion is higher than that without the catalytic combustion at the higher equivalence ratio. This is because the high temperature mixture including the high reactivity intermediates such as CO and H2 generated by the catalytic combustion stabilized the gas phase reaction. These results show that the catalytic combustion can effectively act on the flame stabilization at the higher equivalence ratio. [email protected] W1P004 SIMPLE METHODOLOGY FOR CONSTRUCTING OVERALL REACTION MECHANISMS USING A MICRO FLOW REACTOR WITH A CONTROLLED TEMPERATURE PROFILE Shogo Onishi, Kaoru Maruta, Hisashi Nakamura, Takuya Tezuka, Susumu Hasegawa, Tohoku University, Japan Multi-dimensional combustion simulations play an important role in developing engines and combustors. However, the computational cost of simulation with chemical reactions is proportional to the cube of the number of species. Therefore, there is a demand for the construction of chemical reaction mechanisms which are able to obtain reasonable answer with small simulation cost. The objective of this study is to develop simple methodology for constructing overall reaction mechanisms of ethanol/air for the engineering-purpose combustion simulation of ethanol scramjet engines operated under reduced pressure conditions. The construction of overall reaction mechanisms was made by fitting for the dependence of inlet mean flow velocity on the weak flame location in the author's original flow reactor. Weak flame is characterized as the initiation of ignition while itself is observed as stable flames. This unique characteristic of the weak flames was employed for the construction of overall reaction mechanisms in this study. The dependence
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