Experimental and numerical analysis of dilute gas-particle flow in a pipe section

Abstract

Coal-fired power plants depend on the milling and conveying of Pulverised Coal (PC), where the coal is milled down and then distributed through a network of pipes, using pneumatic transport, to individual burners that feed the boilers. These systems can be plagued by various operational problems due to varying flow conditions, which can even lead to unplanned plant breakdowns and illegal emission of pollutants. The quality of PC gas-particle mixtures and flow stability can be improved by online measurement of particle mass flow and size distributions. A Particle Flow Test Loop (PFTL) was available that includes a blower fan providing gas flow for the system, a solid particle feeder to mix particles with the gas, a number of long pipe sections, and finally, a cyclone separator and gas cleaning system. To enable particle flow measurements, a new pipe test section for the PFTL was designed and analysed using computational fluid dynamics (CFD) simulations. The multiphase software code Neptune CFD by EDF was used in conjunction with Ansys Fluent and Siemens Star-CCM+. The final design was manufactured and fitted to the PFTL and can accommodate measurement devices such as an offline isokinetic sampler as well as online laser-based devices. Two-phase CFD modelling was used to predict cross-sectional solid concentrations for comparison with experimental measurements of particle velocity and particle size distribution. In this paper, selected results from the gas-particle flow simulations are presented, together with comparisons to experimental measurements taken inside the PFTL test section.