Integrated pumping and/or energy recovery system

The positive displacement, energy recovery pump of claim 9 wherein

• the first valve means comprises input valve means and output valve means, wherein:
• the input valve means comprises means for coupling the first fluid from the input header into the first working volume of the first cylinder when the piston stroke direction causes the first working volume within the first cylinder to expand, and into the second working volume of the second cylinder when the piston stroke direction causes the second working volume within the second cylinder to expand, and
• the output valve means comprises means for allowing the first fluid to flow under pressure to the output header from the first working volume of the first cylinder when the piston stroke direction causes the first working volume of the first cylinder to contract, and to flow from the second working volume of the second cylinder when the piston stroke direction causes the second working volume of the second cylinder to contract;
• wherein the first fluid enters the first working volume of the first cylinder during the same piston stroke that it is pumped from the second working volume of the second cylinder, and enters the second working volume of the second cylinder during the same piston stroke that it is pumped from the first working volume of the first cylinder;
• whereby pumping occurs during each piston stroke direction.

An energy recovery pump comprising:

• a fluid pump having a first piston rod which reciprocates between a bottom dead center (BDC) position and a top dead center (TDC) position during one pump cycle, the BDC position being separated from the TDC position by a linear distance L;
• a cylinder housing having an inside diameter D and having first and second piston chambers therein;
• first and second pistons slidably connected in tandem within said first and second piston chambers, respectively, the first piston having a diameter of approximately D and having an upper and lower surface, and the second piston also having a diameter of approximately D and having an upper and lower surface, the lower surface of the first cylinder being mechanically linked with the upper surface of the second cylinder by a second piston rod, at least one of the first and second pistons being mechanically linked for reciprocating motion with said first piston rod, whereby both the first and second pistons slide within their respective first or second piston chambers within said cylinder housing a distance L as the first piston rod reciprocates between the BDC and TDC positions;
• the first piston chamber being divided into first and second working volumes by the first piston, with the volume within the first piston chamber partially bounded by the upper surface of the first piston comprising the first working volume, and the volume within the first piston chamber partially bounded by the lower surface of the first piston comprising the second working volume;
• the second piston chamber similarly being divided into third and fourth working volumes by the second piston, with the volume within the second piston chamber partially bounded by the upper surface of the second piston comprising the third working volume, and the volume within the second piston chamber partially bounded by the lower surface of the second piston comprising the fourth working volume;
• a feed line;
• a pressurized output line;
• an energy recovery line;
• a discharge line;
• first valving means for establishing fluid communication between the feed line and whichever of the first or fourth working volumes is expanding as the first and second pistons move within their respective first and second piston chambers, and for establishing fluid communication between the pressurized output line and whichever of the first or fourth working volumes is contracting as the first and second pistons move within their respective first and second piston chambers, whereby a fluid made available through the feed line will flow into whichever of the first or fourth working volumes is expanding and will then be pumped therefrom under pressure to the pressurized output line when the first or fourth working volume is subsequentlv contracting;
• and
• second valving means for establishing fluid communication between the energy recovery line and the second working volume, and between the discharge line and the third working volume, whenever the first piston rod is at its BDC position;
• and for establishing fluid communication between the energy recovery line and the third working volume, and between the discharge line and the second working volume, whenever the first piston rod is at is TDC position;
• whereby the energy recovery line is in fluid communication with whichever of the second or third working volumes is about to expand so that a pressure force associated with a pressurized fluid made available in the energy recovery line assists in moving the first and second pistons during the pump cycle by working against the lower surface of the first piston within the second working volume, or against the upper surface of the second piston within the third working volume, whichever working volume is about to expand;
• and
• whereby the discharge line is alternately placed in fluid communication with whichever of the second or third working volumes is about to contract so that a fluid present in the second or third working volumes will be discharged therethrouqh as the working volume contracts,
• said controlled power means including means for creating a dwell period during which the piston is stopped at the end of each forward and backward stroke and a control unit for selectively opening and closing the second valving means only during one of the dwell periods so that wear on said valving means is significantly reduced.

An energy-recovery pump comprising:

• first and second sealed chambers each having an inlet port, an outlet port, an energy-recovery port and a discharge port;
• first and second pistons mounted for movement within said first and second sealed chambers, respectively, each piston having a front side and a back side;
• a common piston shaft interconnecting said first and second pistons so that they move in unison;
• a controlled power source coupled to the interconnected pistons that applies a force thereto to cause said first and second pistons to move within their respective sealed chambers in a pump cycle;
• wherein the pump cycle comprises a forward-stroke portion during which the first piston reduces a first working volume within the first chamber, which volume is partially bounded by the front side of the first piston, and a back-stroke portion during which the first piston moves to reduce a second working volume within the first chamber, which volume is partially bounded by the back side of the respective piston, said second chamber having working volumes corresponding to the first and second working volumes of the first chamber,
• said inlet and outlet ports being in fluid communication with said first working volume and said energy-recovery and discharge ports being in fluid communication with said second working volume,
• an input header in fluid communication with an input fluid source;
• an output header in fluid communication with each output port;
• a return header for carrying fluid which was pumped through the outlet header back to the pump;
• check valves in the input header leading to each inlet port;
• check valves in the output header associated with each outlet port;
• whereby a fluid received into the first working volume of the first chamber during the back-stroke portion of the pump cycle is pumped therefrom through its output port during the following forward-stroke portion of the pump cycle, and further whereby fluid received into the corresponding volume of the second chamber during the forward-stroke portion of the pump cycle is pumped therefrom through its output port during the next back-stroke portion of the pump cycle, whereby each forward-stroke or back-stroke of the pump cycle pumps fluid to the output header;
• energy-recovery valves that selectively open and close to establish fluid connections between the energy-recovery ports and the return header;
• discharge valves that selectively open and close to permit flow from the discharge ports;
• and
• a control unit which includes means for creating a dwell period during which the pistons are stopped at the end of each forward or back stroke and means for selectively opening and closing the energy-recovery and discharge valves only during the dwell periods, wherein the energy-recovery valve associated with the first chamber and the discharge valve associated with the second chamber are opened following completion of the back-stroke portion and before commencement of the forward-stroke portion of the pump cycle so that the energy-recovery port of the first chamber is connected to the return header while the discharge port thereof is closed, and wherein following completion of the forward-stroke portion and before commencement of the back-stroke portion of the pump cycle, the energy-recovery valve of the first chamber is closed and its discharge valve is opened;
• whereby fluid under pressure in the return header provides force to the back side of the first piston during the forward-stroke portion of the pump cycle, and to the front side of the second piston during the back-stroke portion of the pump cycle, thereby supplementing the forward-stroke and back-stroke forces provided by the controlled power source.

The combination of a filtering unit and a positive displacement, energy recovery, fluid pump that is driven by a controlled reciprocating power source, wherein an input fluid stream is pumped to the filtering unit at a high pressure, and wherein an outlet fluid stream exits the filtering unit under lower pressure, comprising:

• a first piston mounted for reciprocating movement within a first cylinder so as to separate said first cylinder into first and second working volumes whereby, when the first piston reciprocates within the first cylinder, the first working volume increases as the second working volume decreases, and vice versa;
• a second piston mounted for reciprocating movement within a second cylinder so as to separate said second cylinder into first and second working volumes whereby when the second piston reciprocates within the second cylinder, the first working volume increases as the second working volume decreases, and vice versa;
• a common piston rod interconnecting said first and second pistons;
• linkage means for mechanically linking the controlled reciprocating power source to the first and second interconnected pistons so that both are reciprocated by the power source at the same time, wherein the first working volume of the first cylinder and the second working volume of the second cylinder increase in volume at the same time, and vice versa;
• means for establishing fluid communication between a source of input fluid and whichever of the first working volumes is increasing in volume during a piston stroke so as to receive the input fluid;
• means for establishing fluid communication between the filtering unit and an output port on whichever first working volume is decreasing in volume during a piston stroke, whereby the fluid therewithin is pumped to the filtering unit;
• energy recovery valving means for establishing fluid communication between the lower pressure outlet fluid stream exiting from the filtering unit and whichever second working volume that is increasing in volume during a piston stroke, whereby the lower pressure outlet fluid assists the reciprocating power force in driving either the first or second piston to pump fluid from that respective cylinder on the forward stroke;
• discharge valving means for opening and closing a discharge port on each cylinder in communication with the second working volume, whereby the fluid contained within the second working volume is discharged through the discharge port as the second working volume decreases on the rearward stroke, and
• a control unit which includes means for creating a dwell period during which each of said interconnected pistons is stopped at the end of each forward and rearward piston stroke;
• and means for selectively opening and closing the energy recovery valving means and the discharge valving means only during the dwell periods,
• whereby wear on such valving means is significantly reduced.

The combination of three energy-recovery pumps and a semipermeable membrane filtering unit which produces a permeate stream and a concentrate stream, each said pump comprising:

• a cylinder having an inside diameter D and having first and second piston chambers therein;
• first and second pistons slidably interconnected by a common piston rod so as to reciprocate in tandem within said first and second piston chambers, respectively, between a bottom dead center (BDC) position and a top dead center (TDC) position, the BDC position being separated from the TDC position by a linear distance L, the pistons having diameters of approximately D and having upper and lower surfaces, the lower surface of the first piston being mechanically linked with the upper surface of the second piston by the common piston rod, one of the first and second pistons being mechanically linked for reciprocating motion with a drive piston rod, whereby both the first and second pistons slide within their respective first or second piston chambers within said cylinder housing a distance L between the respective BDC and TDC positions;
• the first piston chamber being divided into first and second working volumes by the first piston, with the volume within the first piston chamber partially bounded by the upper surface of the first piston comprising the first working volume, and the volume within the first piston chamber partially bounded by the lower surface of the first piston comprising the second working volume;
• the second piston chamber being similarly divided into third and fourth working volumes by the second piston, with the volume within the second piston chamber partially bounded by the upper surface of the second piston comprising the third working volume, and the volume within the second piston chamber partially bounded by the lower surface of the second piston comprising the fourth working volume;
• a feed line;
• a pressurized line leading to the filtering unit;
• an energy recovery line carrying the concentrate stream from the filtering unit;
• a discharge line;
• first valving means for establishing fluid communication between the feed line and whichever of the first or fourth working volumes is expanding as the first and second pistons move within their respective chambers, and for establishing fluid communication between the pressurized line to the filtering unit and whichever of the first or fourth working volumes is contracting, whereby fluid made available through the feed line flows into whichever of the first or fourth working volumes is expanding and is thereafter pumped through the pressurized output line when that working volume is subsequently contracting;
• and
• second valving means including energy recovery valves and discharge valves for establishing fluid communication between the energy recovery line and the second working volume, and between the discharge line and the third working volume, whenever the first piston rod is at its BDC position;
• and for establishing fluid communication between the energy recovery line and the third working volume, and between the discharge line and the second working volume, whenever the first piston rod is at is TDC position;
• whereby the pressure of the concentrate stream in the energy recovery line in whichever of the second or third working volumes is about to expand assists in driving the first and second pistons during the pumping stroke thereof, while the discharge line is alternately in fluid communication with whichever of the second or third working volumes is about to contract so that fluid present therein will be discharged therethrough, the diameter of the common piston rod being sized so that the maximum value of the second working volume is less than the maximum value of the first working volume by a factor R which is equal to the ratio between the volume of flow to the filtering unit and the desired volume of flow of the concentrate stream;
• a controlled reciprocating power means mechanically linked to said drive piston;
• a control unit including means for creating a dwell period during which the first and second pistons are stopped at the end of each forward and rearward piston stroke and means for controlling the movement during each piston stroke to create an acceleration period, a constant velocity period, and a deceleration period;
• and
• the control unit also including means for selectively opening and closing the energy-recovery valves and the discharge valves of the second valving means only during one of the dwell periods so that wear thereupon is significantly reduced;
• and
• said combination including means which controls the three controlled reciprocating power means so that the timing of movement of said drive piston rods is such that a phase differential of 120.degree. is produced between the movements of the pistons in the respective cylinders in each of the three pumps.