An investigation into flow mode transition and pressure fluctuations for fluidized dense-phase pneumatic conveying of fine powders

This paper presents the results of an ongoing investigation into the fluctuations of pressure signals due to solids-gas flows for dense-phase pneumatic conveying of fine powders.Pressure signals were obtained from pressure transducers installed along different locations of a pipeline for the fluidized dense-phase pneumatic conveying of fly ash(median particle diameter 30μm;particle density 2300kg/m~3;loosepoured bulk density 700kg/m~3) and white powder(median particle diameter 55 u.m;particle density1600kg/m~3;loose-poured bulk density 620kg/m~3) from dilute to fluidized dense-phase.Standard deviation and Shannon entropy were employed to investigate the pressure signal fluctuations.It was found that there is an increase in the values of Shannon entropy and standard deviation for both of the products along the flow direction through the straight pipe sections.However,both the Shannon entropy and standard deviation values tend to decrease after the flow through bend(s).This result could be attributed to the deceleration of particles while flowing through the bends,resulting in dampened particle fluctuation and turbulence.Lower values of Shannon entropy in the early parts of the pipeline could be due to the non-suspension nature of flow(dense-phase),i.e.,there is a higher probability that the particles are concentrated toward the bottom of pipe,compared with dilute-phase or suspension flow(high velocity),where the particles could be expected to be distributed homogenously throughout the pipe bore(as the flow is in suspension).Changes in straight-pipe pneumatic conveying characteristics along the flow direction also indicate a change in the flow regime along the flow.     

An investigation into flow mode transition and pressure fluctuations for fluidized dense-phase pneumatic conveying of fine powders

This paper presents the results of an ongoing investigation into the fluctuations of pressure signals due to solids–gas flows for dense-phase pneumatic conveying of fine powders. Pressure signals were obtained from pressure transducers installed along different locations of a pipeline for the fluidized dense-phase pneumatic conveying of fly ash (median particle diameter 30 μm; particle density 2300 kg/m³; loose-poured bulk density 700 kg/m³) and white powder (median particle diameter 55 μm; particle density 1600 kg/m³; loose-poured bulk density 620 kg/m³) from dilute to fluidized dense-phase. Standard deviation and Shannon entropy were employed to investigate the pressure signal fluctuations. It was found that there is an increase in the values of Shannon entropy and standard deviation for both of the products along the flow direction through the straight pipe sections. However, both the Shannon entropy and standard deviation values tend to decrease after the flow through bend(s). This result could be attributed to the deceleration of particles while flowing through the bends, resulting in dampened particle fluctuation and turbulence. Lower values of Shannon entropy in the early parts of the pipeline could be due to the non-suspension nature of flow (dense-phase), i.e., there is a higher probability that the particles are concentrated toward the bottom of pipe, compared with dilute-phase or suspension flow (high velocity), where the particles could be expected to be distributed homogenously throughout the pipe bore (as the flow is in suspension). Changes in straight-pipe pneumatic conveying characteristics along the flow direction also indicate a change in the flow regime along the flow.     

Validated scale-up procedure to predict blockage condition for fluidized dense-phase pneumatic conveying systems

This paper presents results of an ongoing investigation into modelling fluidized dense-phase pneumatic conveying of powders. For the reliable design of dense-phase pneumatic conveying systems, an accurate estimation of the blockage boundary condition or the minimum transport velocity requirement is of sig- nificant importance. The existing empirical models for fine powder conveying in fluidized dense-phase mode are either based on only a particular pipeline and product or have not been tested for their accuracy under a wide range of scale-up conditions. In this paper, a validated test design procedure has been devel- oped to accurately scale-up the blockage boundary with the help of a modelling format that employs solids loading ratio and Froude number at pipe inlet conditions using conveying data of two different samples of fly ash, electro-static precipitation （ESP） dust and cement （particle densities： 2197-3637 kgJm3; loose poured bulk densities： 634-1070kg/m3; median size： 7-30 l~m）. The developed models （in power func- tion format） have been used to predict the blockage boundary for larger diameter and longer pipelines （e.g. models based on 69 mm I.D. ~ 168 m long pipe have been scaled up to 105 mm I.D. and 554 m length）. The predicted blockage boundaries for the scale-up conditions were found to provide better accuracy compared to the existing models.     

Experimental investigation into transient pressure pulses during pneumatic conveying of fine powders using Shannon entropy

This paper presents the results of an ongoing investigation into transient pressure pulses using Shannon entropy. Pressure fluctuations (produced by gas–solid two-phase flow during fluidized dense-phase conveying) are recorded by pressure transducers installed at strategic locations along a pipeline. This work validates previous work on identifying the flow mode from pressure signals (Mittal, Mallick, & Wypych, 2014). Two different powders, namely fly ash (median particle diameter 45 μm, particle density 1950 kg/m³, loosely poured bulk density 950 kg/m³) and cement (median particle diameter 15 μm, particle density 3060 kg/m³, loosely poured bulk density 1070 kg/m³), are conveyed through different pipelines (51 mm I.D. × 70 m length and 63 mm I.D. × 24 m length). The transient nature of pressure fluctuations (instead of steady-state behavior) is considered in investigating flow characteristics. Shannon entropy is found to increase along straight pipe sections for both solids and both pipelines. However, Shannon entropy decreases after a bend. A comparison of Shannon entropy among different ranges of superficial air velocity reveals that high Shannon entropy corresponds to very low velocities (i.e. 3–5 m/s) and very high velocities (i.e. 11–14 m/s) while low Shannon entropy corresponds to mid-range velocities (i.e. 6–8 m/s).