Growth rates and morphology of dry particulate fouling under variable process conditions

Particulate Fouling is a complex phenomenon and is governed by various process conditions. It is imperative to elucidate the effects of individual parameters governing the fouling process for better understanding and to aid in numerical modeling. Most of the experimental studies on fouling involve in-situ measurements in the process plants where the individual effects of process conditions are difficult to evaluate. Controlled lab scale experiments that have been reported are limited to a few. In this direction, a controlled high temperature experimental facility has been built to study dry particulate fouling under varying process conditions. Experiments have been conducted for a range of process parameters like: gas phase velocity, particle size distribution, particle mixtures, deposition probe materials and geometries. An optical technique is developed to measure the evolution of fouling layer growth with time. The particle deposition and fouling layer growth is measured for a single cylinder to avoid the complexities associated with the flow dynamics of multiple tube arrays. It is found that the gas phase velocity plays a vital role in the overall process. Experiments with a square tube with its sides inclined at various angles to the mainstream flow direction indicated a reduction in deposition. A cylindrical tube oriented at an angle to the flow also indicated reduced fouling tendency. The geometry of the heat exchanger tube influences the deposition process and by modifying the geometry dry particulate fouling can be reduced.