Recent Developments in Flow Modelling For Fluidized Dense-Phase Gas-Solids Transport of Fine Powders by Prof. S S Mallick | Department of Energy Science and Engineering

Location and Date:

Friday, March 11, 2016, 5:00 pm, LT 202

Abstract

This paper presents results of an ongoing investigation being carried out at the newly developed Laboratory of Particle and Bulk Solids Technologies, Thapar University on the flow modelling of fine powders during the pneumatic transport. An accurate prediction of total pipeline pressure drop is of paramount importance for the reliable design of pneumatic transport systems. Due to the highly concentrated and turbulent nature of the gas-solids mixture, fundamentally understanding the flow mechanism and accurately modelling solids friction factor have only made limited progress so far. Under the present study, a two-layer based model has been developed by separately considering the solids friction contributions of the non-suspension (dense) bed of powders flowing along the bottom of pipe and the suspension (dilute-phase flow) of particles occurring on top of the non-suspension layer. Volumetric loading ratio and dimensionless velocity have been used to model the non-suspension dune flow layer. The volumetric loading ratio term incorporates the effect of product volume occupancy inside the pipeline, which is believed to be a better representation of flow conditions compared to mass ratio (solids loading ratio). A solids impact and friction term and dimensionless velocity have been used to model the dilute-phase suspension flow due their established reliability. Model for solids friction have been developed using the straight-pipe conveying data of two types of fly ash, cement and ESP dust (median particle diameter: 7 to 30 μm; particle density: 2300 to 3637 kg/m³; loose-poured bulk density: 610-1080 kg/m³). The developed models were validated for their scale-up accuracy and stability by using them to predict the pressure drops in five larger and longer pipelines (69 mm I.D. x 168 m long; 105 mm I.D. x 168 m long; 69 mm I.D. x 554 m long, 65 mm I.D. x 254 m long and 80/100 mm I.D. x 407 m long pipes) and by comparing the experimental versus predicted conveying characteristics. The two-layer model provided improved accuracy compared to existing models indicating that the model is able to adequately address the dense- to dilute-phase transition criteria. Furthermore, a semi-fundamental model for pressure fop for fluidized powder flow under very dense-phase condition has been developed using the stress values of powders. Initial scale-up validation of this model has shown excellent capabilities. Several existing models to predict minimum transport or pipeline blockage condition during pneumatic conveying have been evaluated, which showed that the existing models can become unreliable under certain flow conditions. Based on the test results of 21 different powders conveyed through 37 pipelines, a unified model for the minimum transport boundary has been developed that represented gas Froude number as a function of solids loading ratio and particle Froude number. The model has been validated on the minimum transport boundary data of 3 different products, conveyed through 6 pipelines. Comparisons between experimental blockage boundary and predicted results have shown that the new particle Froude number and solids loading ratio based model provides more accurate and stable predictions compared to the other existing models. The developed models for solids friction and minimum transport boundary would enable industry to reliably design fluidized dense-phase pneumatic transport system, that would typically reduce the energy cost by 50% compared to the conventional dilute-phase system.

Keywords: fluidized dense-phase, pneumatic conveying, solids friction factor, two-layer model, scale-up validation, minimum transport

Bio-sketch:

Dr. S.S. Mallick is working as Assistant Professor at the Department of Mechanical Engineering, Thapar University. Dr. Mallick completed his B.E (Mechanical) from Bengal Engineering College in 2001, M.TECH from IIT Delhi in 2005 and PhD in gas-solid transport systems from the University of Wollongong, Australia in the year 2010. Before switching over to academics, Dr. Mallick worked as a consulting engineer for Development Consultants Private Limited (Kolkata/Delhi) for 5 years, where he designed bulk solids transport system used in several thermal power plants. He has developed the Laboratory for Particle and Bulk Solids Technologies Thapar University, funded by DST and CSIR (through sponsored research projects). Dr. Mallick has published about 25 SCI listed Journal Papers in relevant areas of Powder Technology (gas solids transport, nanofluid heat transfer etc). His laboratory has produced 2 PhD, 15 ME thesis, has undertaken several consulting projects and organized/organizing major International conference (PGBSIA 2013, 2016) and workshops in last 5 years. Dr. Mallick was awarded the “Teaching Excellence Award” at Thapar University in the year 2015.