Reverse osmosis methods
A reverse osmosis system includes a pressure vessel comprising first and second ports. Membranes disposed in the pressure vessel, permeate water and block permeation of dissolved solids from concentrate flowing between the first and second ports. A high pressure pump includes an inlet and an outlet. A circulation pump includes an inlet and an outlet and is configured to circulate the concentrate between the first and second ports. A valved circulation apparatus is configured to select between a forward flow mode and a discharge mode of the system. In the forward flow mode, the circulation pump inlet is connected to the second port and the circulation pump outlet is connected to the first port. In the discharge mode, the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the first port and production of permeate is prevented.
1 . A method of reverse osmosis comprising:
selecting a forward flow mode of a reverse osmosis system, via a valved circulation apparatus of the system, wherein a circulation pump outlet of a circulation pump of the system is connected to a first port of a pressure vessel of the system and a circulation pump inlet of the circulation pump is connected to a second port of the pressure vessel;
pressurizing concentrate, via a high pressure pump of the system, to flow through the pressure vessel in a forward flow direction from the first port to the second port;
permeating water from the concentrate via reverse osmosis through one or more membranes of one or more membrane modules disposed in the pressure vessel, as the concentrate flows in the forward flow direction;
flowing the water as a permeate out of a permeate outlet of the pressure vessel;
blocking permeation of dissolved solids from the concentrate through the membranes, as the concentrate flows in the forward flow direction;
circulating, via the circulation pump, the concentrate back from the second port to the first port in the forward flow direction;
selecting a forward discharge mode of the system, via the valved circulation apparatus,
wherein the circulation pump inlet is connected to a high pressure pump inlet of the high pressure pump and the circulation pump outlet is connected to the first port;
discharging the concentrate from the system through a first discharge line connected to the second port when the system is in the forward discharge mode;
pressurizing the concentrate, via the high pressure pump, to a pressure that is greater than a predetermined threshold osmotic pressure of the system; and
preventing production of permeate by closing a permeate discharge valve connected to the permeate outlet.
2 . The method of claim 1 , comprising:
selecting a reverse flow mode, via the valved circulation apparatus, wherein the circulation pump inlet is connected to the first port and the circulation pump outlet is connected to the second port;
pressurizing the concentrate, via the high pressure pump, to flow through the pressure vessel in a reverse flow direction from the second port to the first port;
permeating water from the concentrate via reverse osmosis through the membranes disposed in the membrane modules, as the concentrate flows in the reverse flow direction;
flowing the water as a permeate out of the permeate outlet of the pressure vessel;
blocking permeation of dissolved solids from the concentrate through the membranes, as the concentrate flows in the reverse flow direction; and
circulating, via the circulation pump, the concentrate back from the first port to the second port in the reverse flow direction.
3 . The method of claim 2 , comprising:
selecting a reverse discharge mode, via the valved circulation apparatus, wherein the circulation pump inlet is connected to the high pressure pump inlet and the circulation pump outlet is connected to the second port;
discharging the concentrate from the system through a second discharge line connected to the first port when the system is in the reverse discharge mode;
pressurizing the concentrate, via the high pressure pump, to a pressure that is greater than a predetermined threshold osmotic pressure of the system; and
preventing production of permeate by closing the permeate discharge valve connected to the permeate outlet.
4 . The method of claim 3 , comprising:
switching the modes in sequential order:
from the forward flow mode to the reverse discharge mode,
from the reverse discharge mode to the reverse flow mode,
from the reverse flow mode to the forward discharge mode, and
from the forward discharge mode to the forward flow mode.
5 . The method of claim 1 , comprising:
positioning an orifice in the first discharge line, wherein the orifice is sized to provide a predetermined pressure drop in the first discharge line that reduces pressure fluctuations caused by switching from the forward flow mode to the forward discharge mode.
6 . The method of claim 3 , comprising:
positioning a first orifice in the first discharge line, wherein the first orifice is sized to provide a first predetermined pressure drop in the first discharge line that reduces pressure fluctuations caused by switching from the forward or reverse flow mode to the forward discharge mode; and
positioning a second orifice in the second discharge line, wherein the second orifice is sized to provide a second predetermined pressure drop in the second discharge line that reduces pressure fluctuations caused by switching from the forward or reverse flow mode to the reverse discharge mode.