(273h) Simulation of Particulate Matter Formation during Heating Different Cooking Oils Using Aspen Plus
Evaporation of organic constitutes of cooking elements such as cooking oils, with subsequent cooling and supersaturation of vapor phase results in particle formation. Experimental studies can help us to understand source emission rates and size distributions of formed PM. However, experimental measurements of some physical properties such as supersaturation level of produced organic vapor, viscosity and surface tension of formed particles and partitioning of chemicals among the gas and particulate phases might be hard or even impossible. In this study, we tried to build a simulation tool using Aspen Plus simulation software which is extensively used in chemical processes to estimate such physical properties. This software works at steady state conditions, with ability to predict physical properties of thousands of chemicals. Aspen Plus also performs mass and energy balances, and includes advanced thermodynamic models to predict phase equilibria of complex chemical mixtures. It is also used to simulate chemical reactions with provided kinetics data by the users. In this study, heating six cooking oils including canola, soybean, safflower, sunflower, olive and peanut were simulated. The approach was to first predict the evaporation of triglycerides from heated oils, mixing with air containing VOCs and ozone, and then minimizing the Gibbs energy of the resulting supersaturated vapor at constant temperature and pressure. Then, PM emission rate due to homogeneous nucleation can be estimated. The experimental data in the literature were used to tune simulation parameters. The effects of indoor RH and temperature were also studied on PM emission rates of the heated oils. The current simulation model is being developed to account for cooking oil smoking as well as heterogeneous nucleation. The current approach in simulating cooking PM emissions can be utilized for simulating indoor air chemistry involving phase equilibria and reactions.