**6. Slurry pipe applications and challenges**

This section discusses application examples of ERT in slurry pipe flow over a variety of slurries ranging from synthetic laboratory slurries to industrial tailings samples.

**Figure 10** shows LBP images from a CSIRO test in a 50-mm NB pipe rig examining the transition from horizontal to vertical flow for a polymer solution/crushed glassbased suspension based on data presented in [34]. The sample results here showed that the stratification could be maintained, change side, or be destroyed in the pipe depending on flow conditions which, in the case of constant carrier fluid rheology,

#### **Figure 8.**

*Comparison between reference data and sample pipe rig data for high-conductivity tailings. Conventional differential 2D LBP processing. Both images are at the same (arbitrary) scale. As originally published and presented at the BHR 20th International conference on Hydrotransport, Melbourne, Australia, 3rd–5th may 2017, [24].*

**Figure 9.**

*Comparison between homogenous and stratified ERT images using absolute 2.5D processing on the same data as* **Figure 8***. Conductivity images shown. As originally published and presented at the BHR 20th International conference on Hydrotransport, Melbourne, Australia, 3rd–5th may 2017, [24].*

could be superficial velocity. Further results from [34] showed that the distribution of solids in the vertical pipe was a function of the rheology of the carrier fluid and the pipe velocity for a fixed 4x diameter bend as the transition element from horizontal to vertical, with some conditions leading to the stratification being maintained in the vertical pipe. It should be noted that the yield stress of the carrier fluid could statically support the dispersed coarse particles in the vertical pipe, but not a bed of solid particles thus leading to particle settling on shutdown. Hence, the design of a system to vertically convey coarse solids would need to take account of the observed behavior and ideally guarantee particle dispersion.

**Figure 11** shows LPB images taken from a pipe test with a synthetic clay/sand/ gravel slurry during a pipe test for evaluating rheology additives [14]. The effect of the pipe velocity on the degree of suspension is clear from the ERT images.

An industrial slurry was supplied to CSIRO for pipe tests as a complete slurry; thus, it was not possible to obtain a separate reference from a homogenous carrier fluid. Thus, a reference had to be obtained from a homogenous mix of the slurry as

**Figure 10.**

*ERT images for flow around a vertical pipe bend. Adapted from data presented in [34].*

#### **Figure 11.**

*Synthetic clay/sand/gravel slurry at 80% w/w solids.*

supplied in order for the data acquisition to occur. It was known that there were coarse particles in the slurry, but the slurry overall had the appearance of a high-yield-stressbased suspension. A view of the slurry slump test together with ERT results obtained from the 2.5D absolute imaging approach as described in Section 5.3 are shown in **Figure 12**, showing stratified behavior, even with a high yield stress carrier fluid.

A data set for very high-conductivity tailings is shown in **Figure 13** which shows ERT images plotted on the flow curve for two concentrations of the tailings from [24].

#### **Figure 12.**

*High yield stress slurry conductivity images showing stratification. As originally published and presented at the BHR 20th International conference on Hydrotransport, Melbourne, Australia, 3rd–5th may 2017, [24].*

#### **Figure 13.**

*Flow curve and ERT for high-conductivity tailings at two concentrations in a 100-NB pipe. Color represents conductivity. As originally published and presented at the BHR 20th International conference on Hydrotransport, Melbourne, Australia, 3rd–5th may 2017, [24].*

The ERT data shown were processed using the absolute 2.5D ERT approach. The ERT system had to be operated at its highest possible current setting (75 mA) to obtain usable data in the 100-mm diameter pipe rig.

The slurries tested in **Figures 12** and **13** were supplied as complete slurries; thus, there was no possibility to separately obtain a reference image from a homogenous carrier fluid. The procedure was then to use a dummy section of pipe with an ERT sensor to obtain a reference from a homogenized sample of the slurry as shown in **Figure 14**. It is conceded that this approach involves a compromise; however, it was possible to obtain data sufficient to demonstrate that the slurry flows were stratified under shear in the pipe which was the primary objective of the tests. The significance of the stratified flow is that predictive models are required to take this behavior into account for correct predictions of industrially sized pipe flows as discussed in [35] and subsequent publications up to [36].

While many of the results described earlier are in the laminar flow regime, the CSIRO group has also investigated the turbulent pipe flow regime using ERT as described recently in [37]. For this work, ERT was used to obtain solids concentration *Electrical Resistance Tomography Applied to Slurry Flows DOI: http://dx.doi.org/10.5772/intechopen.107889*

**Figure 14.** *Dummy pipe section for obtaining ERT references of homogenous slurries.*

data for comparison with a DNS-DEM model for weakly turbulent coarse-particle non-Newtonian suspensions.

Other practical challenges relevant to the use of ERT in pipe flow were as follows:


industrial slurries of higher conductivity to obtain usable data. In practice, it was found to be useful to obtain reference data at several different injection currents before introducing coarse solids. This procedure allowed choice of a suitable current for the majority of the test campaign, once initial slurry measurements had been made.

