Bio-oil, also called pyrolysis liquid biofuel, is made from the pyrolysis of waste biomass and provides a carbon-neutral alternative fuel. This study focuses on optimizing swirl burners for use with bio-oil. Spray combustion of bio-oil/ethanol blends was previously studied using a 10 kW swirl burner. The previous burner had a small combustion chamber with no refractory lining. It was not feasible to stabilize flames of bio-oil without blending with ethanol, and the pollutant emissions were relatively high. In this study, the burner is upgraded by implementing a refractory-lined combustion chamber and increasing the size of the chamber to investigate the relationship between the burner design and combustion performance of bio-oil. The main reasons for upgrading the burner are to eliminate ethanol addition to bio-oil, stabilize the pure bio-oil flame, achieve lower pollutant emissions, and make the burner more comparable to industrial bio-oil burners. In addition to flame stability, fuel boiling inside the nozzle and nozzle coking are two other challenges that require some optimization and adjustments in the setup. After modification of the new burner configuration and adjustment of the operating parameters, the pure bio-oil flame is stabilized with minimal nozzle coking and gaseous exhaust emissions. The new burner has a significantly lower amount of heat loss and, hence, a higher gas temperature within the combustion chamber compared to the previous burner. The effects of operating conditions on the gaseous pollutants are also investigated. CO and unburned hydrocarbon emissions are extremely sensitive to the operating parameters, such as the equivalence ratio, swirl number, and atomizing air flow rate. Moreover, the pilot flame energy and primary air preheat temperature play important roles in ignition quality of bio-oil, flame stability, and nozzle coking. The dominant mechanism for NOx emissions is the conversion of fuel-bound nitrogen. The new burner also has decreased particulate matter emissions compared to the previous burner by achieving higher temperatures, which favors burnout of char particles within the flame.