COLOGNE, GERMANY, Sept. 18, 2105 -- In December 2014, LANXESS, a specialty chemicals company based in Germany, provided a total of 630 Lewabrane RO (reverse osmosis) B400 HR (high rejection) membrane elements to a water treatment plant at a major oil refinery in the city of Bratislava, Slovakia. These systems have been running stably and reliably for over eight months.
The RO facility at the refinery of Slovnaft -- a member of the Hungarian MOL Group and a supplier of refinery products in Slovakia, producing a broad range of petrochemical raw materials -- currently serves as the largest reference project in Europe for LANXESS brackish water membrane elements, said Alexander Scheffler, director, Membrane Business in the LANXESS Liquid Purification Technologies business unit.
The raw water for the plant is sourced from the Danube and contains between 320 and 400 mg/l dissolved solids with seasonally fluctuating organic fractions; further, it displays an electric conductivity of up to 580 μS/cm. During treatment, it first undergoes chemical pretreatment (coagulation, flocculation) and ultrafiltration, before continuing to the RO system, which is divided into five separate lines, each equipped with 126 membrane elements.
The three-stage demineralization facility can turn out up to 135 cubic meters of permeate per hour and line, and the maximum conductivity falls far below the target value stipulated by the operator of 15 μS/cm. The system has a permeate yield of up to 85 percent. In the subsequent cleaning stage, mixed-bed ion exchange resins from LANXESS' Lewatit line are used to remove any remaining ionic compounds. The facility produces fully demineralized water that is available as boiler feed water for water-steam circuits and other technical purposes.
Calculations in the planning phase conducted with the LewaPlus design software, developed specifically for Lewabrane and Lewatit products, already showed that permeate conductivities of less than 10 μS/cm could be expected. Accordingly, this meant less of a burden on the mixed-bed ion exchange resins. "We met all these expectations, and that makes us very optimistic about easily fulfilling all the performance guarantees we granted to the customer," Scheffler said.
Compared to the other membrane elements used in previous years, the new system displays significantly longer dwell times. "We used to have to go through the cleaning regimen every four to six weeks, but the magnitude of pressure decline and the conductivity did not increase with the elements from LANXESS until after four months," said Peter Šrámek, head of Slovnaft refinery. "After cleaning, the elements were back up to the same performance level as when they went into operation."
Overall, the longer intervals between cleanings reduced the consumption of cleaning chemicals and increased the availability of the RO lines. Similarly, the low salt content of the permeate extends the regeneration intervals of the mixed-bed ion exchange system, further cutting costs.
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LANXESS is a specialty chemicals company with sales of EUR 8.0 billion in 2014 and about 16,300 employees in 29 countries. The company is currently represented at 52 production sites worldwide. The core business of LANXESS is the development, manufacturing and marketing of plastics, rubber, intermediates and specialty chemicals. LANXESS is a member of the leading sustainability indices Dow Jones Sustainability Index (DJSI World and DJSI Europe) and FTSE4Good. For more information, visit www.lanxess.com.