Analysis of heat-up, devolatilization, and ignition of coal particles using point-particle DNS

It is acknowledged that pulverized coal combustion (PCC) will remain a major source of electrical energy, due to a growing energy demand and coal being abundant and cheap. To reduce CO2 emissions, retrofitting coal power plants with oxy-fuel combustion technology is a viable option. Burning coal in O2-rich conditions leads, however, to temperatures that exceed burner limits. For mitigation, a part of the exhaust stream is re-injected into the burner. This changes the burning conditions significantly, which necessitates investigations of O2-/CO2-rich combustion in oxy-coal burners.

We present an examination of coal particles that cluster in reactive turbulence using point-particle DNS. Mimicking typical burning conditions, the mass loadings are about 0.1, Stokes numbers are about 1, and the Taylor-scale Reynolds number is about 50. In a precursor simulation, particles are randomly seeded in a turbulent base flow to obtain statistically homogeneous and isotropic initial conditions. The particles are heated up by the hot gases and devolatilize, followed by volatile combustion in the gas phase. Simulation results are assessed in terms of instantaneous contour plots, spatially averaged statistics, and joint probability distributions of relevant combustion quantities.