Tubular membranes replaced at South Africa coal plant
More than 2,500 tubular reverse-osmosis (TRO) membrane modules have been replaced at a South African coal-to-liquids refinery by Veolia‑owned Membratek in a subcontract.To keep up with improved production performance at its refinery in Secunda, Sasol Limited has successfully completed a R 13 million (US$ 1.24 million) upgrade of its water treatment plant. The TRO plant helps to reuse water from the facility's ash water system for various refinery processes, reducing overall raw water intake while limiting the release of potentially harmful pollutants into surface water systems.
The TRO plant was originally designed and built in 2001 by Veolia Water Solutions & Technologies South Africa, then known as Weir Envig. The recent upgrade was foreseen in the plant's original designs, which significantly reduced engineering time during changeover while ensuring maximum plant uptime.
The expansion was implemented and commissioned by Malutsa, a 70% black-owned water projects company affiliated with the Veolia Water multinational.
"Membratek was subcontracted to manufacture 2,620 unique 4.3 m TRO membrane modules," says Abrie Wessels, regional general manager at Veolia. "These modules are ideally suited to the harsh conditions, such as high turbidity, organics and salinity experienced at this unit. After Sasol's own pilot studies, Membratek membranes proved to be the best solution for this application."
Featuring a large 12 mm bore construction and a robust design, Membratek's TRO membranes were chosen for Sasol's most recent upgrade based on their unique ability to resist fouling, even in highly demanding operating circumstances. "The membranes are superb at dealing with the variable nature of the feed water, requiring minimal pretreatment and chemical conditioning which reduces running costs significantly," says Wessels.
Regular mechanical cleaning using a sponge ball will further reduce operational costs of the TRO plant, while regular testing on site, facilitated by the unique membrane train design, ensures that membranes at the end of their useful lifespan are identified and replaced with minimal impact on standard plant operations.
"On average, Membratek tubular membranes have proven to have a typical lifetime of 4-5 years at this Sasol plant. Due to the modular nature of the system, membrane replacement is an easy and non-invasive task facilitated by a steady supply of replacement modules," says Wessels.