Atomization characteristics of pyrolysis oil derived from waste tires

Abstract

The atomization characteristics play a key role in the highly efficient combustion of pyrolysis oil derived from waste tires. In this study, the fuel properties of tire pyrolysis oil (TPO) were initially studied, and then a high-speed camera and a phase Doppler particle analyzer were employed to characterize the atomization feature of TPO. The influence of pressure and nozzle orifice diameter on atomization characteristics such as spray angle, droplet velocity, and droplet size distribution was investigated. The results showed that TPO had a high calorific value of about 43.6 MJ/kg and a low viscosity of 3.84×10^–6 m²/s at 40 °C, which made it have the potential to be used as an alternative fuel. Higher pressure expanded the spray angle and extended the spray in both the axial and radial directions. With increasing pressure, spray angle and droplet velocity raised, and the increase in crushing effect of air reduced the Sauter mean diameter (SMD) of the droplets. To obtain proper atomization quality for combustion, the pressure is expected to be higher than 1.25 MPa. With increasing nozzle orifice diameter, droplet velocity increased, and the SMD of the droplets increased as well due to weakened crushing effect of the orifice. Therefore, the pressure must be increased to maintain the atomization quality when using a nozzle with a larger orifice. Due to the lower viscosity, the velocity and particle size distribution of TPO droplets after atomization were smaller than those of diesel droplets. The extremely small carbon black contained in TPO also contributed to the breaking of droplets and played a certain role in the size reduction of the oil droplets, but it may cause the risk of nozzle blockage. In summary, TPO showed great atomization characteristics for alternative fuel applications.

Graphical abstract