With the development of seawater desalination technologies (reverse osmosis), SWRO is the main way that can produce fresh water from seawater or blackish water in the 21st century today, however, there are still many issues on the cost of operating. And the energy consumption for seawater reverse osmosis (SWRO) is one of main factors that affect the cost of desalination product. Energy reduction is therefore imperative.
The function of Energy recovery device is to reduce energy consumption and cost by recycling and reusing the pressure energy from RO system high pressure concentrated seawater. Energy Recovery Device (ERD) is the key to energy-saving in the operation of any seawater reverse osmosis (SWRO) desalination products, in which PX Pressure Ex-changer device is the most efficient solution available today and can reduce the energy consumption of seawater reverse osmosis (SWRO) systems by up to 60 percent.
The cost of power consumption accounts for the largest proportion, which is around 30% of the total RO operating cost. Typically for large facilities (>50,000m3/d), the ERD that reduces energy consumption is only a fraction of the initial capital cost (1-2%) of the entire plant, but offer major return on investment through energy savings.
Above mentioned picture is showing PX Working Principle:
1. The PX Pressure Ex-changer energy recovery device promotes pressure transfer from the high pressure brine reject stream to a low-pressure seawater feed stream by putting the two streams into the state of direct and momentary contact in the ducts of a rotor. The rotor is installed into a ceramic sleeve between two ceramic end covers with precise clearances.
2.When injecting high-pressure water, it can create a hydrodynamic bearing without almost friction. The rotor spinning inside the hydrodynamic bearing is the only moving part in the PX device. At any time, half of the rotor ducts are exposed to the high-pressure stream and half to the low-pressure stream. When the rotor turns, the ducts pass a sealing area that separates high and low pressure. Thus, the ducts that contain high pressure are separated from the adjacent ducts containing low pressure by the seal formed with the rotor’s ribs and the ceramic end covers.
3. When the rotor turns every time, this pressure exchange process is repeated for each duct, so that the ducts are continuously filling and discharging. At a nominal speed of 1,200 rpm, 20 revolutions are completed every second.
KYsearo larger scale seawater desalination system (above 120 TPD) will equip ERI’s energy recovery device, which can curtail energy consumption to 3~4 KWH per cubic meter product water, comparing with the system without ERD 6~7 KWH, reducing the running cost up to 49%.