Hydraulic Conveying
Hydraulic Conveying/Slurry Transportation
Introduction
The efficient hydraulic transportation of particulates is crucial across many industrial sectors such as mining, dredging and nuclear. The key is to reduce to the volume water consumed in the process while increasing concentration.
There are typically four flow regimes in a horizontal pipe describing the solid phase concentration profile. These are, flow with a stationary bed, flow with a moving bed, heterogeneous flow and pseudo-homogeneous.
The characterisation of these slurry flow regimes is useful for the design, optimisation and control of processes involving slurry flows. It is also useful for research purposes by providing experimental data to develop, optimise and validate empirical and numerical multi-phase flow models.
Solution
Industrial Tomography Systems (ITS) has successfully developed and applied Electrical Resistance Tomography (ERT) to slurries in pipes.
ERT measurements can be used to characterise the slurry flow regime as a function of operating conditions such as velocity, solids concentration and particle characterisation.
Solid Volume Fraction and Velocity Measurement
For example in mineral processing the monitoring of clay based drilling mud’s for the oil industry and the monitoring of long distance hydraulic conveying systems have received attention. In drilling cuttings there is a requirement to measure the velocity and concentration of a given phase as the product of multiplying the bulk velocity by the concentration may not sufficiently estimate the volumetric flux. ERT is well suited to monitor drill cuttings in water-based mud’s. An example of such a measurement of the distribution of the local axial velocity of the cuttings is shown below.
Local solids volume fraction distribution and axial velocity using a dual-plane ERT system.
Flow Regime Characterisation
A major concern in pumping of slurries is pipe wall damage due to an inappropriate flow regime. ERT has been demonstrated to successfully visualise the slurry flow regime from pseudo-homogeneous to moving bed. Moreover direct interpretation of the ERT measurements facilitated the identification of transitions between homogeneous and heterogeneous slurry flow regime.
Benefits
It has been demonstrated that ERT can be applied to slurry transportation processes. The benefits to the end-user include:
-
Improved process design
-
Process optimisation
-
Process control
-
Reduced wear and tear on pipes
-
Multi-phase flow model development
References:
Williams, R.A. (2005) Mineral and material processing, Process Imaging for Automatic Control, Scott, McCann, Taylor and Francis, pp 359-400
Giguére, R., Fradette, L., Mignon, D. and Tanguy, P.A. (2008) Characterisation of slurry flow regime transitions by ERT, Chemical Engineering Research and Design, Vol. 86, pp 989-996
Wang, M., Jones, T.F. and Williams, R.A. (2003) Visualisation of asymmetric solids distribution in horizontal swirling flows using electrical resistance tomography, Trans IChemE, Volume 81, Part A, pp854-861
Print page
Bookmark page
