Paul T Ogunlela, Donald Giddings, Chris Bennett, Stefan Born, Margot Klaassen, Isaac Gennissen, Richard Farnish
Abstract: Pneumatic conveying of finely pulverised coal particles is an important process in the steelmaking industry, used to transport coal to the blast furnace. Erosive wear caused by high velocity particles impacting on the inner wall surfaces of pneumatic conveying riser pipes causes a severe problem in the steel-making industry. Continuous erosion left unmaintained eventually leads to pipe punctures. This paper aims to help minimise the erosive wear in industrial risers by investigating the effects of different particle sizes on the wear rates in industrial coal conveying ducts to control the grind size in industrial gas-solid flow processes and optimise reduced wear. Computational fluid dynamics (CFD) simulations and 4 semi empirical erosion models were used to analyse these effects, with an Eulerian-Lagrangian technique to model the multiphase gas-solid flow in the riser. The continuous phase (air) was modelled by solving Eulerian Reynolds-averaged Navier Stokes equations and the discrete phase (coal) was modelled using the Lagrangian discrete phase model (DPM) approach. The particle sizes investigated ranged from 1 to 1000 µm. The results showed the curves for each erosion model representing the changes in erosive wear with an increase in particle size for each erosion model. Every model showed similar curve shapes but varied in degree of wear rates. The curves of each model showed a steady increase in wear between particle diameters of 1 and 150 µm, followed by a sharp increase in wear at 200 µm, with the maximum erosion rates recorded between 300 and 350 µm. Subsequently, the wear rates began to drop, with a steady decrease in wear with particle diameters between 600 and 1000 µm. The behaviour of the curves was characterised by analysing the Stokes’ number and kinetic energy at each particle size. It was concluded that the sharp increase at 200 µm occurred, due to the number of particles (which possess sufficient kinetic energy) and the number density escaping the continuous phase and impacting the riser walls. Larger particles may have possessed greater individual kinetic energies; however, the fewer particles tend to impact the riser walls at higher particles sizes due to significantly lower number densities, resulting in a decrease in wear rates.
Keywords: Particle, wear, size, erosive, model, rate, impact, pipe.
Date Published: June 6, 2022 DOI: 10.11159/jffhmt.2022.006View Article