Transporting viscous fluids using minimal energy

Fluids like crude oil and highly concentrated emulsions are very viscous (thick or sticky).

Considerable pumping pressure is required to transport them, even when large diameter pipes are used, which makes the process extremely energy-intensive.

Researchers are therefore trying to ascertain ways to reduce the effective viscosity of these fluids so that the huge savings in energy consumption can lead to reduced transportation cost, and therefore a smaller overall carbon footprint for such industries.

One such researcher is Sumit Tripathi from the IITB-Monash Research Academy, who is working on a project titled, 'Development of Model to predict rheology/properties of High Internal Phase Emulsion' under the supervision of Prof Amitabh Bhattacharya, Prof Ramesh Singh, and Prof Rico Tabor. This work is supported by Orica Mining Services (Australia), one of the Academy's industry partners.

The IITB-Monash Research Academy is a Joint Venture between IIT Bombay and Monash University, Melbourne, and operates a graduate research program in Mumbai. Research is conducted by scholars like Sumit in both countries, whilst studying for a dually-badged PhD from both organizations.

Fig 1 : A sketch of water-lubricated core-annular flow (CAF)
(image drawn by Sumit Tripathi)

Researchers have come around to the view that core annular flow (CAF) is the most economic and effective way to reduce the pumping energy associated with the transportation of viscous fluids, says Sumit. "In a CAF," he explains, "highly viscous fluids are lubricated by a thin boundary film of low viscosity fluid (such as water) present near the pipe wall. The pumping pressures are balanced by the wall shear stress associated with low viscous annular fluid. The lubricated flow requires a pressure drop (and therefore energy) that is comparable to pumping low viscosity annular fluid alone, and depends only weakly on the viscosity of the core fluid."

Simply put, researchers like Sumit are lubricating the viscous fluid with water near the pipe walls. Their final aim is to use minimal energy and water to transport high viscosity fluids via this method. For complex fluids, such as highly concentrated emulsions, they also aim to understand how this minimal energy is related to the rheological properties of the fluid. Rheology is the branch of physics that studies the deformation and flow of matter.

Extensive literature is available on CAFs, says Sumit, including models for levitation, stability studies, empirical studies of energy efficiency of different flow types and empirical correlations giving the pressure drop vs. mass flux. However, almost all the studies have been reported for Newtonian fluids, and little is known about the suitability of highly viscous non-Newtonian fluids having complex rheology to be transported as CAFs.

Fig. 2: Typical cryogenic scanning electron microscopy (Cryo-SEM) image of high internal phase emulsion (image taken at Cryo-FEG-SEM, central facility of IIT Bombay)

Sumit is, therefore, minutely examining the transport characteristics and rheology of concentrated emulsions, especially the High Internal Phase Emulsions (HIPEs).

Explaining why this can get complex, he says, "Identifying the exact behaviour of HIPEs requires a detailed parametric study. HIPEs show significant variability in their properties at different measurement length-scales, meaning that a holistic approach bridging individual droplet measurements right up to bulk pipe flow is required. The rheology of HIPE also depends on droplet size and their distribution in the emulsions. Understanding the effects of various parameters such as viscosity, volume fraction of fluids, interfacial tension, salt concentration, droplet interaction, etc.' on the flow characteristics are required to investigate the suitability of HIPEs for transportation as core-annular flows via pipelines."

Prof Murali Sastry, CEO, IITB-Monash Research Academy, is confident that the work being carried out by Sumit and his fellow researchers will have a huge impact on process industries dealing with highly viscous complex fluids.

"The IITB-Monash Research Academy was conceived as a unique model for how two leading, globally focussed academic organisations can come together in the spirit of collaboration to deliver solutions and outcomes to grand challenge research questions facing industry and society," says Prof Sastry. "We are expecting that Sumit and his team will comment on factors that affect the rheology of a wide variety of industrially-relevant high internal phase emulsions. These factors include mixing time, salt concentration, methods of formulation and selection of a suitable emulsifier. For a particular emulsion (having huge viscosity) they should be able to report the percentage reduction in pressure-drop when it is transported as water-lubricated core-annular flow. This could be a possible solution for transporting high viscosity complex fluids through pipelines, especially within chemical plants."

Industries like petroleum, food, cosmetics, paints, health-care, etc—which routinely handle such fluids at various stages of processing—will be keenly watching Sumit's progress.

Research scholar: Sumit Tripathi, IITB-Monash Research Academy

Project title: Development of model to predict rheology/properties of high internal phase emulsion

Supervisors: Prof Amitabh Bhattacharya, Prof Ramesh Singh, Prof Rico Tabor

Contact details: sumit.tripathi@monash.edu

This story was written by Mr Krishna Warrier based on inputs from the research student and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.