Biomass fast pyrolysis liquid (or bio-oil) is a cellulose based alternative fuel with the potential to displace fossil fuels in stationary heat and power applications. To better understand the combustion behavior and emissions of bio-oil, a 10 kW spray burner was designed and constructed. The effect of swirl, atomization quality, ignition source energy, air/fuel preheat, and equivalence ratio on the stability and emissions of bio-oil spray flames was investigated. A blend of 80% pyrolysis liquid and 20% ethanol by volume was used during the tests. Since the fuel is not fully distillable, it is important to have good atomization, thorough mixing, and increased recirculation to promote the burnout of nonvolatile material and decrease CO and hydrocarbon emissions. Air and fuel preheat are also important for reducing these emissions, although subsequent fuel boiling within the nozzle should be avoided in order to maintain flame stability. The amount of total primary air and atomizing air that can be used to improve turbulence, mixing, droplet burnout, and overall combustion quality is limited by the low volatility and tighter lean blow-out limit associated with bio-oil. The NO x produced in these flames is dominated by the conversion of fuel bound nitrogen. In order to reduce the NO x emissions without refining the fuel, the use of staged combustion is recommended.

Biomass fast pyrolysis liquid (or bio-oil) is a cellulose based alternative fuel with the potential to displace fossil fuels in stationary heat and power applications. To better understand the combustion behavior and emissions of bio-oil, a 10 kW spray burner was designed and constructed. The effect of swirl, atomization quality, ignition source energy, air/fuel preheat, and equivalence ratio on the particulate matter emissions of bio-oil spray flames was investigated. A blend of 80% pyrolysis liquid and 20% ethanol by volume was used during the tests. Increasing the residence time of spray droplets in the hot combustion zone by increasing the swirl number promotes the burnout of solid residues. Decreasing the mean diameter of fuel droplets by increasing the atomizing air flow rate has a similar effect. Ignition source energy, air/liquid fuel preheat, and equivalence ratio have either a weak or ambiguous effect on the measured particulate emissions. The residual material collected from the exhaust is composed of both carbonaceous matter and fly ash. However, the majority of particulate matter consists of ash, even at relatively poor combustion conditions. These results suggest that it is possible to provide enough oxygen availability and residence time for droplets to undergo nearly complete burnout during combustion. Under such conditions, the total particulate matter emissions could be further mitigated by reducing the inherent ash content in the fuel.

Hemp-seed pyrolysis bio-oil was upgraded in a batch laboratory-scale pressure reactor under 800 psi (cold) hydrogen gas at 350−365 °C using a non-alkaline, nontoxic Fe x O y /SiO2/TiO2 catalyst [reduced red mud (RRM)] obtained by the reduction of red mud with HOAc/HCCOH. The upgraded liquid obtained was separated into stable organic and aqueous phases. Comparative analyses between the crude oil and the organic and aqueous phases of upgraded products showed that the RRM-upgraded bio-oil is composed of fewer carbonyl-containing and polar oxygenated compounds but more saturated hydrocarbons. The upgraded oil phases are less viscous than the native oil and stable against resin formation for at least 60 days. The catalytic activity of RRM is related to its ability to catalyze both deoxygenation and cracking reactions that convert reactive components (aldehydes, ketones, and carboxylic acids), which make the oil unstable over time, into less reactive deoxygenated products.