Seawater desalination system and energy recovery apparatus

An energy recovery apparatus for converting pressure energy of concentrated seawater discharged from a reverse-osmosis membrane-separation apparatus to pressure energy of seawater in a seawater desalination system for producing fresh water from the seawater by supplying the seawater pressurized by a pump to the reverse-osmosis membrane-separation apparatus to separate the seawater into fresh water and concentrated seawater, the energy recovery apparatus comprising:

• a cylindrical chamber having a space for containing concentrated seawater and seawater therein, the chamber being installed such that a longitudinal direction of the chamber is placed in a vertical direction;
• a concentrated seawater port provided at a lower part of the chamber for supplying and discharging the concentrated seawater, the concentrated seawater port being positioned on a central axis of the cylindrical chamber;
• a seawater port provided at an upper part of the chamber for supplying and discharging the seawater, the seawater port being positioned on the central axis of the cylindrical chamber;
• a first flow resistor provided at a concentrated seawater port side in the chamber;
• and
• a second flow resistor provided at a seawater port side in the chamber;
• wherein the first flow resistor provided at the concentrated seawater port side and the second flow resistor provided at the seawater port side each comprise a first perforated circular plate, the first perforated circular plate comprising a central area with a predetermined diameter, and a circumferential area outside the predetermined diameter, the central area having no holes and the circumferential area having holes formed over the circumferential area,
• wherein the predetermined diameter of the central area of the first perforated circular plate for the first flow resistor is substantially equal to an inner diameter of the concentrated seawater port,
• wherein the predetermined diameter of the central area of the first perforated circular plate for the second flow resistor is substantially equal to an inner diameter of the seawater port,
• wherein the first flow resistor and the second flow resistor each comprise a second perforated circular plate having holes that are regularly spaced over an entire surface of the second perforated circular plate,
• the second perforated circular plate of the first flow resistor is placed more distant from the concentrated seawater port than the first perforated circular plate of the first flow resistor, and
• the second perforated circular plate of the second flow resistor is placed more distant from the seawater port than the first perforated circular plate of the second flow resistor.