Simulation of the dynamic behaviour of the gas released during the pyrolysis process, when it passes through a gas cyclone

Abstract

A computational fluid dynamic (CFD) model was applied for a cyclone used in a conversion unit in Ostrava (Czech Republic). The purpose of this work was to investigate the labor conditions of the cyclone and provide the information how to optimize it for a good behavior of the gas which is released during the pyrolysis process. In accordance with the main objective, the modelling provided the knowledge of the temperature distribution over the gas inside the cyclone, the range of velocity values, the path lines of the gas and the trajectory of the heavy particles, for different operational conditions. The CFD computer code FLUENT was used for the three dimensional simulation and Gambit as pre-processor to generate the model and create the mesh. Operational data was used to model the cyclone and the gas in the simulations. The RNG k-ε turbulence model together with wall functions and species characterization was adapted for characterization of the gas behaviour and also the simulation was executed in double precision (ddp) mode. The simulations have pointed out that a good range of values to the boundary conditions principally a good value of mass flow can influence in a positive or negative way the behavior of the gas inside the cyclone. In this work was observed that for the conditions which the cyclone is working the efficiency is not good, the mass flow is too small therefore the cyclone should be small.