Common-rod series hydraulic compressors

Abstract

A multi-cylinder fluid compressor for compressing a working fluid. The compressor includes a first gas compression cylinder, divided into axially aligned compression chambers by a first reciprocating gas piston, and a second gas compression cylinder, divided into axially aligned compression chambers by a second reciprocating gas piston. The gas compression cylinders are axially aligned and the reciprocating gas pistons are driven by a common piston rod extending through the compression cylinders and operably connected with the reciprocating gas pistons. The common piston rod is reciprocally driven by a hydraulic fluid supply system to reciprocally drive the reciprocating gas pistons. The compressor system may be operated as a multi-stage compressor system by conveying working fluid outlet from one compression chamber to the inlet of another compression chamber. Cooling may be provided between stages. One application for the compressor is in a vapor recovery system for drawing low pressure vapors that can accumulate above hydrocarbon liquids in a tank.

1 . A multi-cylinder fluid compressor operable to compress a working fluid, said multi-cylinder fluid compressor comprising:
 a first gas compression cylinder, divided into first and second axially aligned compression chambers by a first reciprocating gas piston, each of the first and second compression chambers of the first gas compression cylinder having an inlet and an outlet;   a second gas compression cylinder, divided into third and fourth axially aligned compression chambers by a second reciprocating gas piston, each of the third and fourth compression chambers of the second gas compression cylinder having an inlet and an outlet;   wherein the first gas compression cylinder and the second gas compression cylinder are axially aligned;   wherein the outlets of the first and second gas compression cylinders are positioned at a bottom of the first and second gas compression cylinders;   a common piston rod extending through said first and second axially aligned compression cylinders and operably connected with the first reciprocating gas piston and the second reciprocating gas piston;   first and second hydraulic cylinders positioned at opposite ends of the multi-cylinder fluid compressor, with the first and second compression cylinders therebetween to axially drive the common piston rod;   wherein the first and second hydraulic cylinders are adapted to be actuated by a hydraulic fluid supply system to reciprocally drive the common piston rod and thereby the first reciprocating gas piston and the second reciprocating gas piston   wherein the first hydraulic cylinder is at a head of the first gas compression cylinder and has a first hydraulic piston operatively connected to the piston rod to drive the piston rod in a first axial direction, and wherein the second hydraulic cylinder is at a head of the second gas compression cylinder and has a second hydraulic piston operatively connected to the piston rod to drive the piston rod in a second axial direction, the second axial direction opposite the first axial direction;   wherein the multi-cylinder fluid compressor further comprises a first buffer chamber, comprising a variable annular space between the common piston rod and the first hydraulic piston extending between the head of the first gas compression cylinder and the first hydraulic piston, and a second buffer chamber, comprising a variable annular space between the common piston rod and the second hydraulic piston extending between the head of the second gas compression cylinder and the second hydraulic piston.   
     
     
         2 . The multi-cylinder fluid compressor of  claim 1 , further comprising:
 a seal device between the common piston rod and the first gas compression cylinder and a seal device between the common piston rod and the second gas compression cylinder;   a piston seal device between the first reciprocating gas piston and the first gas compression cylinder; and   a piston seal device between the second reciprocating gas piston and the second gas compression cylinder.   
     
     
         3 . (canceled) 
     
     
         4 . The multi-cylinder fluid compressor of  claim 1 , further comprising a first hydraulic piston seal device between the first hydraulic piston and the first hydraulic cylinder and a second hydraulic piston seal device between the second hydraulic piston and the second hydraulic cylinder. 
     
     
         5 . The multi-cylinder fluid compressor of  claim 1 , wherein the outlets of the first gas compression cylinder are in fluid communication with the inlets of the second gas compression cylinder to provide a multi-stage fluid compressor. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled) 
     
     
         9 . (canceled) 
     
     
         10 . The multi-cylinder fluid compressor of  claim 1 , wherein the first buffer chamber and the second buffer chamber are pressurized, pressure equalized, vented, fluidly connected, or combinations thereof. 
     
     
         11 . The multi-cylinder fluid compressor of  claim 2 , wherein the inlets of the first and second gas compression cylinders are positioned at a top of the first and second gas compression cylinders. 
     
     
         12 . (canceled) 
     
     
         13 . The multi-cylinder fluid compressor of  claim 2 , wherein one or more of the inlets or the outlets or both of the first and second gas compression cylinders are radial. 
     
     
         14 . The multi-cylinder fluid compressor of  claim 2 , wherein one or more of the inlets or the outlets or both of the first and second gas compression cylinders are axial. 
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . The multi-cylinder fluid compressor of  claim 2 , wherein the first and second gas compression cylinders are adjacent, and connected by a connector plate. 
     
     
         18 . The multi-cylinder fluid compressor of  claim 2 , further comprising a variable volume pocket fluidly connected with at least one of the first, second, third, and fourth compression chambers. 
     
     
         19 . The multi-cylinder fluid compressor of  claim 2 , wherein each of the inlets and the outlets of the first, second, third, and fourth compression chambers are in fluid communication with a respective one-way check valve. 
     
     
         20 . The multi-cylinder fluid compressor of  claim 2 , wherein the piston seal devices include one or more wear rings. 
     
     
         21 . The multi-cylinder fluid compressor of  claim 5 , further comprising:
 a third gas compression cylinder, divided into fifth and sixth axially aligned compression chambers by a third reciprocating gas piston, each of the fifth and sixth compression chambers of the third gas compression cylinder having an inlet and an outlet;   wherein the third gas compression cylinder is substantially axially aligned with the first gas compression cylinder and the second gas compression cylinder;   wherein the common piston rod is operably connected to the third reciprocating gas piston;   wherein the outlets of the second gas compression cylinder are in fluid communication with the inlets of the third gas compression cylinder;   a seal device between the common piston rod and the third gas compression cylinder; and   a piston seal device between the third reciprocating gas piston and the third gas compression cylinder.   
     
     
         22 . The multi-cylinder fluid compressor of  claim 1 , further comprising the hydraulic fluid supply system. 
     
     
         23 . A method of recovering vapor from a tank containing liquid hydrocarbons, the method comprising:
 delivering a flow of the vapor to a first gas compression cylinder of a multi-cylinder fluid compressor, the first gas compression cylinder divided into first and second axially aligned compression chambers by a first reciprocating gas piston;   operating the first reciprocating gas piston to increase pressure of the vapor delivered to the first and second compression chambers to provide a flow of pressurized vapor;   delivering the flow of pressurized vapor from a bottom of the first gas compression cylinder to a second gas compression cylinder of the multi-cylinder fluid compressor, the second gas compression cylinder divided into third and fourth axially aligned compression chambers by a second reciprocating gas piston;   operating the second reciprocating gas piston in common with the first reciprocating gas piston, to further increase pressure of the pressurized vapor delivered to the third and fourth compression chambers to provide a flow of further pressurized vapor; and   delivering the flow of further pressurized vapor from the third and fourth compression chambers from a bottom of the second gas compression cylinder.   
     
     
         24 . (canceled) 
     
     
         25 . The method of  claim 23 , wherein operating the second reciprocating gas piston in common with the first reciprocating gas piston comprises starting the operating, stopping the operating, setting a speed of the operating, adjusting a speed of the operating, maintaining the speed of the operating, or combinations thereof. 
     
     
         26 . The method of  claim 25 , wherein operating the second reciprocating gas piston in common with the first reciprocating gas piston is responsive to pressure of the vapor in the tank.