# Co-Firing of Fast Pyrolysis Bio-Oil and Heavy Fuel Oil in a 300-kW\({}_{\text{th}}\) Furnace
## 1 Introduction
Many researchers have reported that biodiesel can be blended with diesel from 5% to 30%, and there are no big problems running a diesel engine with B20 (20% biodiesel blend with 80% diesel by volume) [14; 15]. Moreover, co-firing bio-oil with fossil fuels like coal [16; 17] and natural gas [18] has been investigated, particularly at large power plants. The Red Arrow Products Company in the USA has co-fired bio-oil (produced by Rapid Thermal Processing) with coal in a boiler equipped with a 20-MWe Stoker burner with a five percent share of thermal input by bio-oil. It was found that the power plant operated with no notable problems after cost-efficient boiler modifications to allow for co-firing bio-oil with coal, and no negative impacts were noticed in emission levels, operation and maintenance programs, or ash handling [16]. [PERSON] et al. [17] also reported co-firing fast pyrolysis bio-oils in a coal-fired power plant. Additionally, pyrolysis bio-oil has also been co-fired with natural gas in a combined cycle power station of 350 MWe in Harculo in the Netherlands [18]. Bio-oil can be used as a replacement for conventional fossil fuels in existing industrial boilers. However, some modifications to the combustion system and operating conditions are required in order to improve combustion for co-firing bio-oil with fossil fuels, since some problems might take place during the usage of standard equipment constructed for firing fossil fuels [19]. For instance, the existing burner must be replaced with a modified oil burner or a newly designed bio-oil burner (such as a burner head configuration) for firing bio-oil. In addition, the pumping, piping, oil preheating, and valve systems must also be specially designed for bio-oil. The usage of bio-oil to completely replace fossil fuels has some limitations, since bio-oil has bad properties, such as high viscosity, poor volatility, coking, and corrosiveness. These limitations cause the primary challenge in the combustion process and industrial applications. However, a low blend ratio of bio-oil to petroleum-derived oil (low bio-oil content) has advantages, such as the fact that it can occur without modification of the burner and boiler sections, and can be easily combusted in existing industrial boilers and furnaces. Moreover, biofuels like biodiesel, ethanol, and butanol are made from agricultural crops, leading to food security issues and an increase in energy costs. On the other hand, bio-oil derived from fast pyrolysis of woody biomass (such as wood waste and other non-edible feedstocks) does not cause the problem of food security or the increase in energy prices. In a recent study, we performed heating experiments for suspended droplets of bio-oil/diesel blends and bio-oil/heavy fuel oil (HFO) blends to examine microexplosion and ignition behaviors [20]. Bio-oil used in the experiments was produced from fast pyrolysis processing of lauan wood. The results showed that ignition did not occur when the bio-oil/HFO blends had lower mixing ratios of bio-oil below 50%. However, with high blending ratios (not less than 60%), ignition could occur. Moreover, the bio-oil/HFO blends were observed to take a longer time than the bio-oil/diesel blends to finish burning. Considering the practical applications of fast pyrolysis bio-oil in industrial furnaces and boilers, further study is required to achieve a better understanding of the combustion characteristics and pollutant emissions when co-firing bio-oil with HFO. In the present study, therefore, an existing 300-kW\({}_{\text{th}}\) multi-fuel combustion test furnace was utilized without any modifications to explore the combustion and emissions characteristics of bio-oil/HFO blends. We aim to examine the feasibility of using these blends as a replacement for HFO in industrial applications.