Designing with Turbochargers: Case Studies for Ultra High Pressure RO Operation

The current ~1,200 psi environment for membrane desalination and concentration was established at the turn of the millennium. At that time, system recovery was limited by the operating range of RO membranes, which could handle a maximum brine TDS of ~90,000 ppm. However, demand for higher RO pressures to address feed salinity and concentration requirements conflict with efforts to reduce capital cost and energy consumption, requiring advanced membrane solutions for increased recovery and concentration. The emergence of RO membranes capable of handling brine TDS of up to 120,000 ppm and rated for operation under Ultra High Pressure (UHP) conditions (1,800 psi), along with high pressure pumps, turbochargers, pressure vessels and couplings rated for UHP operation, opens new horizons for RO system recovery. The key benefit of this is to reduce the volume of brine that must be concentrated further using an evaporator or crystallizer, or sent for disposal. Operating at elevated recovery rates and pressures carries operational challenges. Pressure must be distributed appropriately throughout the RO system to ensure effective membrane performance. This paper presents an overview of the options available to RO system designers using turbochargers. The designs outlined differ in application, but share several crucial benefits, most importantly: 1. Elimination of the need for a break tank between RO stages 2. Reduction of automation and auxiliary equipment requirements 3. Straightforward and reliable operation. The rising number of UHP RO projects worldwide, most notably a three-stage brine concentration facility in Poland and a two-stage brine mining pilot in Saudi Arabia, have demonstrated that we can push the limits of RO recovery while maintaining low energy consumption and low fouling potential. Today’s generation of UHP systems represent the final process evolution in RO, a convergence of established practices, innovative design, and new technology to make UHP a reliable, commercially viable solution.

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