A pump efficiency test rig, designed and built by researchers based at the Flow Process Research Centre, was recently used to test the characteristics of sewage sludge and paper pulp waste fluids in Stockholm.
The centre, which is based in the Civil Engineering and Survey Department at the Cape Town campus, is tasked with researching problems that relate to the flow of industrial fluids.
The researchers have expertise in making precise measurements of the viscous characteristics (called rheology) of complex fluids, and then relating these characteristics to the flow of industrial fluids and pumping systems.
The test rig, which was shipped to Stockholm earlier this year, was used by the researchers to test the characteristics of these fibrous suspensions.
The team, Prof Rainer Haldenwang, Dr Veruscha Fester and Mr Richard du Toit recently returned from Stockholm, where they spent several weeks conducting tests.
Prof Haldenwang said: “It took us only two days to assemble the rig and to do the water tests, showing that the rig is truly portable, despite its physical size.”
He said the portability of the test rig and ease of reassembly stems directly from Mr du Toit’s unique modular design of the test loop and its support structures.
“Without him it would have taken much longer,” said Prof Haldenwang.
The team’s host and project partner in Stockholm, Dr Richard Holm, who works for Innventia, a paper pulp research institute, was also impressed that the facility was operational in such a short time.
A research facility at Hammarby Sjöstadverk in Stockholm, operated by the Swedish Environmental Research Institute and the Royal Institute of Technology, supplied centrifuged sludge.
Two types of sludge (lysed and unlysed) from another water treatment plant, were also tested to determine their viscous properties. In total, eight sludges and three concentrations of fibre suspensions were tested over a period of three weeks.
Prof Haldenwang said one significant achievement was finding the characteristic pump curve for fibre suspensions in laminar flow, which is a huge point of debate in this area of research and rarely obtained experimentally.
The project sponsors, which include the Swedish International Development Cooperation Agency and Tillväxtverket, a Swedish Agency for Economic and Regional Growth, were impressed by the amount of test work completed.
They were also pleased to witness the efficient pumping of very viscous slurries by centrifugal pumps at a much lower pumping power than is often the case in industry. The sponsors indicated that they would like to see the results implemented in industry.
Prof Haldenwang said the results of the tests are invaluable for further research.
He said they are now planning to conduct an audit of the type of pumps and energy usage in local sewage treatment plants, and to demonstrate how knowledge of the viscous properties of sludge can be used to monitor and control pumps for optimum use of energy.
By Candes Keating
Written by CPUT News
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