Energy Recovery Device
In sea water reverse osmosis (SWRO) process, most of the hydraulic energy feed into was wasted in the form of a pressurized brine waste stream discharged from the membranes. Therefore, recover wasted discharged energy has been a primary driver for innovation and development of SWRO energy recovery device.
Their effectiveness and reliability of energy recovery devices were widely considered to have made large-scale SWRO economically viable through recent advances in the energy recovery technology. Below are two type of energy recovery device which were widely applied in various SWRO plants:
One or more nozzles direct the SWRO reject stream onto a tangential-flow pump turbine directly connected to a centrifugal impeller spinning in the SWRO feed stream. The feed stream, partially pressurized by a high-pressure pump, is boosted by the turbocharger impeller to the SWRO feed pressure.
The turbocharger and the high-pressure pump are not directly connected, providing a degree of flexibility in the operation of these devices. Also, turbochargers have a relatively small footprint and are easy to install. A typical SWRO process with a hydraulic turbocharger is illustrated as diagram below.
Pressurized feed water from the pressure exchanger combines with the discharge of the high-pressure pump to feed the membranes. The high pressure pump operates at the full membrane pressure but supplies only the flow rate of the permeate.
A booster pump in series with pressure exchanger is necessary to circulate high-pressure water through the membranes. A typical SWRO process with pressure exchanger is illustrated in diagram on the left.