Technical Report 1, c4e-Preprint Series, Cambridge

Soot Formation in Turbulent Reacting Flows - a PDF Based Approach Applied to Carbon Black Production

ref: Technical Report 1, c4e-Preprint Series, Cambridge

Authors: Michael Balthasar, Fabian Mauss, Anthony Knobel, and Markus Kraft

Associated Theme: Particle Processes

Abstract

The purpose of this work is to propose a detailed model for the formation of soot in turbulent reacting flow and to use this model to study a carbon black furnace. The model is based on a combination of a detailed reaction mechanism to calculate the gas phase chemistry, a detailed kinetic soot model based on the method of moments, and the joint composition probability density function (PDF) of these scalar quantities. Two problems, which arise when modelling the formation of soot in turbulent flows using a PDF approach, are studied. A consistency study of the combined scalar-soot moment approach reveals that the molecular diffusion term in the PDF-equation can be closed by the IEM and Curl-type mixing models, whereas the Binomial-Langevin model is not suitable. An investigation of different kernels for the collision frequency of soot particles shows that the influence of turbulence on particle coagulation is negligible for typical flame conditions and the particle size range considered. The model is used to simulate a furnace black process, which is the most important industrial process for the production of carbon blacks. Good agreement between the calculated soot yield and data measured in an industrial furnace black reactor is achieved. The effect of the mixing intensity on soot yield and different soot formation rates is investigated. In addition the influence of different operating conditions such is temperature and equivalence ratio in the primary zone of the reactor is studied.

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