Two reverse-osmosis (RO) elements based on polyamide thin-film composite membranes have been launched by German chemicals company Lanxess.
The Leverkusen-based company, spun off from chemical giant Bayer in 2005, is promising to add other element types soon to its product range, which already includes ion-exchange resins.
The main field of application for the Lewabrane RO membrane separation elements is desalination of brackish water for industrial applications, including the production of boiler feedwater for power stations. RO membrane and ion-exchange water treatment processes complement each other well, and the highly treated water quality helps to prolong the service life of equipment such as turbines and steam generators with protection against fouling, scale formation and corrosion.
Another application for the spiral-wound Lewabrane elements is preparation of feedwater for electrodeionization (EDI) applications. High-performance RO membranes can provide a reduced load on the downstream EDI process improving cost performance.
“The combination of RO membrane separation and ion-exchange ensures that efficiency and economy can go hand in hand in this and similar applications. This is true synergy,” says Alan Sharpe, manager of strategic projects in Lanxess’ Ion Exchange Resins business unit.
Membrane elements in the Lewabrane RO product family meet top quality standards and comply with all requirements for industrial use. With a standard length of 40 in (1,016 mm) and a diameter of 8 in, Lewabrane RO B400 HR has an active membrane surface area of 400 ft² (37.2 m²).
Salt rejection is 99.7% for a daily permeate flow rate of 37.9 m³ (average value under standard industry reference conditions; salt concentration in the feed: 2,000 ppm, 225 psi (15.5 bar), pH 7, 25°C, and a single element recovery of 15%).
The Lewabrane RO B090 HF 4040 element has the same length but a diameter of only 4 in and an active membrane surface area of 90 ft² (8.7 m²). Thanks to a new anti-telescoping design, the surface area of the membranes exceeds that of other commercially available elements by almost 6%, says Lanxess.
The element owes its superior average permeate flow rate of 2,500 GPD (9.4 m³/d) under standard conditions at a rejection level of 99.5% to the greater active surface area of the RO membrane available inside the RO element.