Evaluation of ignition and self-heating risks in bio-char storage by numerical simulation

Sammanfattning: The move from fossil fuels is getting more relevant throughout the globe, mainly for it getting more costly to emit CO$_2$. The steel industry is one of the biggest contributor of the CO$_2$ emissions, and is therefore very motivated to reduce their emissions. One way to reduce the emissions is to go from coal to bio-char as a reducing agent. BEST(Bio-energy and sustainable technologies) is a research institute in Austria, and have been tasked to do research on bio-char and what problems that may occur with changing from coal to bio-char. One problem with bio-char is that it is prone to self ignition. This project aims is to develop a numerical model that can simulate self heating within bio-char stockpiles. The tool will be for a one-dimensional case using Cartesian coordinates. The calculations are based on the SIMPLE algorithm for Navier-Stokes equations, which is widely used within CFD calculations. This tool has been used to do sensitivity analysis for multiple variables and parameter studies for kinetic parameters related to the oxidation that occurs when bio-char is exposed to oxygen. Results show that oxygen concentration is the limiting factor to how much heat is released within the bag during simulations. Results also show that the accurate descriptions of reaction schemes and their rate expressions is very important to get results that is in line with real world scenarios.