Effect of particle size distribution on pressure drop and concentration profile in pipeline flow of highly concentrated slurry

doi:10.1016/j.ijmultiphaseflow.2005.03.003

International Journal of Multiphase Flow

Volume 31, Issue 7, July 2005, Pages 809-823

https://doi.org/10.1016/j.ijmultiphaseflow.2005.03.003 Get rights and content

Abstract

The experiments were conducted in 54.9 mm diameter horizontal pipe on two sizes of glass beads of which mean diameter and geometric standard deviation are 440 μm & 1.2 and 125 μm & 1.15, respectively, and a mixture of the two sizes in equal fraction by mass. Flow velocity was up to 5 m/s and overall concentration up to 50% by volume for each velocity. Pressure drop and concentration profiles were measured. The profiles were obtained traversing isokinetic sampling probes in the horizontal, 45° inclined and vertical planes including the pipe axis. Slurry samples of the mixture collected in the vertical plane were analyzed for concentration profiles of each particle batch constituting the mixture. It was found that the pressure drop is decreased for the mixture at high concentrations except 5 m/s and a distinct change of concentration profiles was observed for 440 μm particles indicating a sliding bed regime, while the profiles in the horizontal plane remains almost constant irrespective of flow velocity, overall concentration and slurry type.

Introduction

Liquid–solid two phase flow is widely employed in the chemical and mining industries in slurry pipelines and is encountered in natural phenomena such as river mechanics. It has been the endeavour of researchers around the world to develop accurate models for pressure drop and concentration distribution in slurry pipeline. Pressure drop is one of the most important technical parameters to be evaluated by the designer for designing a pipeline slurry transportation system, and is the parameter, which dictates the selection of pump capacity. Several studies for pressure drop prediction in slurry flow are available in literature (Wasp et al., 1977, Doron et al., 1987, Gillies et al., 1991; Sundqvist et al., 1996, Mishra et al., 1998, Ghanta and Purohit, 1999, Wilson et al., 2002, Schaan et al., 2000, Kaushal and Tomita, 2002, Kumar et al., 2003, etc.). Concentration distribution may be used to determine the parameters of direct importance (mixture and solid flow rates) and the secondary effects such as wall abrasion and particle degradation. The recent works of Kaushal and Tomita (2002) and Kumar et al. (2003) are worth mentioning in the field of concentration distribution in slurry pipeline.

Most of the earlier studies on slurry pipeline systems are based on moderate volumetric concentrations of solids (say up to 26%). Much larger concentrations now coming into common use show more complicated behaviour. Also in any practical situation, the solids are coarser in size with broad particle grading being transported at large flow velocities. The flow characteristics of such slurries are studied experimentally in the present study, which will be analyzed to bring out the effect of particle size distribution on pressure drop and concentration profile.

Section snippets

Experimental equipment

A test loop was built to obtain flow rates, concentration profile, pressure drop and flow patterns. The test loop is laid horizontally in the Powder Technology Laboratory of KIT, Japan. A schematic layout and plan view along with the important dimensions of the rig are presented in Fig. 1. The pipe inside diameter is 54.9 mm. The rig consists of 22 m long recirculating pipe loop, 200 l capacity slurry tank, 150 l capacity water tank and a centrifugal pump to maintain the slurry flow. The pipe loop,

Material used and its properties

Spherical glass beads with mean diameters of 125 μm, 440 μm and a mixture of the two sizes have been used to prepare the slurry for the present study. The mixture was prepared by adding 125 μm and 440 μm particles in proportion of 50/50 by mass to the pipe loop. However, the mass ratio MR was not always 50/50 in the flow, and generally the coarser particle size circulated more in the pipeline, in particular, when the concentration is high, which is shown in Table 2(c). The average specific gravity

Experimental results

The measurement was done by monotonously increasing or decreasing flow velocity, V_m, for a given particle concentration. It took about 7 min to complete measurement for a given flow velocity and concentration. The temperature rise during measurement was large when the particle size was 440 μm and the flow velocity was high, but was weakly dependent on the concentration. The overall average temperature rise was about one degree at most between measurements. During the measurement we did not

Conclusions

Following conclusions have been drawn on the basis of present study:

1.
The particle concentration profile is measured for high concentration slurry transport where the maximum overall area-average concentration is 50% by volume employing coarse particles and higher flow velocities up to 5 m/s.
2.
Narrow grading particles tend to have high frictional losses, while broad grading particles have low frictional losses at high concentrations.
3.
Concentration in the horizontal plane remains almost constant

References (10)

P. Doron et al.
Slurry flow in horizontal pipes—Experimental and modeling
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D.R. Kaushal et al.
Solids concentration profiles and pressure drop in pipeline flow of multisized particulate slurries
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U. Kumar et al.
Effect of particle gradation on flow characteristics of ash disposal pipelines
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Effect of particle size distribution on pressure drop and concentration profile in pipeline flow of highly concentrated slurry

Abstract

Introduction

Section snippets

Experimental equipment

Material used and its properties

Experimental results

Conclusions

Int. J. Multiphase Flow

Int. J. Multiphase Flow

Powder Technol.

Powder Technol.

Powder Technol.