An apparatus and method for compressing fluid

Abstract

The invention provides an apparatus for compressing a first fluid. The apparatus comprises a compressor piston comprising a piston cylinder and a piston assembly slidably mounted therein. The piston assembly comprises first and second spaced apart piston members defining a space therebetween. The space is configured to contain a second fluid used to cause compression of the first fluid. The piston assembly further comprises means for feeding second fluid to the space between the first and second piston members.

1 . An apparatus for compressing a first fluid, the apparatus comprising a compressor piston comprising a piston cylinder and a piston assembly slidably mounted therein, wherein the piston assembly comprises first and second spaced apart piston members defining a space therebetween, which space is configured to contain a second fluid used to cause compression of the first fluid, and means for feeding second fluid to the space between the first and second piston members. 
     
     
         2 . An apparatus according to  claim 1 , wherein the apparatus comprises a storage tank configured to store the second fluid therein, and the means for feeding the second fluid to the space between the first and second piston members comprises a pump and at least one second fluid feed conduit extending between the storage tank and the space between the piston members along which the fluid is fed, preferably wherein the pump is activated during the non-compression stage and the second fluid disposed in the space between the first and second piston members is fluidly connected to the storage tank via at least one second fluid leakage conduit. 
     
     
         3 . An apparatus according to  claim 2 , wherein the second piston member comprises a valve configured to control the flow of the second fluid through the at least one second fluid feed conduit into the space between the piston members, preferably wherein the valve comprises biasing means configured to bias the valve into a closed configuration in the second fluid feed conduit, more preferably wherein the biasing means comprises a spring, optionally a helical spring or a cup spring. 
     
     
         4 . An apparatus according to  claim 3 , wherein the second piston member comprises actuation means configured to activate the valve in response to a change in pressure on the first seal or in response to the position of the first piston member with respect to an actuation set-point, preferably wherein the pump is configured to pump the second fluid from the storage tank, through the open valve activated by the actuation means, and along one or more conduit into the space between the first and second piston members. 
     
     
         5 . An apparatus according to  claim 4 , wherein the actuation means is configured to open the valve when the pressure on the first seal increases, and activate the pump to pump second fluid through the valve and/or the actuation means is configured to close the valve when the pressure on the first seal decreases, and deactivate the pump to prevent pumping of second fluid, and/or wherein when the pressure on the first fluid side of the first seal increases due to leakage of the second fluid through the second seal, the first piston member is configured to be urged towards the second piston member, thereby resulting in the actuation means opening the valve, and/or wherein the pre-stress tension of the biasing means exerted on the actuating means substantially corresponds to the weight of the first piston member and the friction created between the cylinder tube and the first seal. 
     
     
         6 . An apparatus according to  claim 4 , wherein the actuation means is configured to open the valve when the position of the first piston member reaches the actuation set-point and/or the actuation means is configured to close the valve when the position of the first piston member moves beyond the actuation set-point. 
     
     
         7 . An apparatus according to  claim 1 , wherein the first piston member is configured to oscillate within the cylinder tube, and is sealed with the cylinder tube by a first radial seal, optionally a stem seal or a piston seal, and the second piston member is configured to oscillate within the cylinder tube, and is sealed with the cylinder tube by a second radial seal, optionally a stem seal or a piston seal, and the first piston member is substantially centrally mounted on the second piston member, and is guided concentrically thereby. 
     
     
         8 . An apparatus according to  claim 1 , wherein the first fluid that is to be compressed contacts one side of the first piston member, and the second fluid contacts the opposite side of the first piston member, preferably wherein the apparatus comprises a leakage cycle return line to the space between the first and second piston members, because, during use of the compressor piston, any leakage of the second fluid at the second seal is automatically balanced out by a replenishment flow of second fluid. 
     
     
         9 . An apparatus according to  claim 1 , wherein the second piston member comprises one or more conduits which extend radially outwardly from the valve to the space between the piston members, preferably wherein the one or more conduits extend diagonally from the valve to the space between the piston members. 
     
     
         10 . An apparatus according to  claim 1 , wherein the pressure difference between the side of the first piston member contacting the first fluid, and the side contacting the second fluid is less than 75 Bar, 50 Bar, 25 Bar, 15 Bar, 10 Bar, 5 Bar, or less than 3 Bar and the compressor piston is configured to increase the pressure of the first fluid to between 100 bara and 1500 bara. 
     
     
         11 . An apparatus according to  claim 1 , wherein the first fluid comprises gas, such as natural gas, fuel gas, hydrogen, gaseous hydrocarbon, liquefied combustion gas, nitrogen, helium, oxygen, and a noble gas, such as argon, or a mixture thereof and the second fluid comprises liquid, which is substantially incompressible, preferably wherein the second fluid comprises an ionic liquid, an LOHC (liquid organic hydrogen carrier), semiheavy water (HDO), deuterium oxide (heavy water), water, or hydraulic oil, or a mixture thereof. 
     
     
         12 . An apparatus according to  claim 1 , wherein the apparatus is configured to use an ionic liquid cushion disposed between the piston assembly and the first fluid to be compressed, preferably wherein the ionic liquid cushion comprises or consists of a substantially pure ionic liquid, or a mixture of an ionic liquid and LOHC. 
     
     
         13 . An apparatus according to  claim 1 , wherein the apparatus comprises:
 an oscillating compressor and/or a hydraulically driven compressor; and/or   a liquid piston compressor and/or an ionic compressor; and/or   a single-stage compressor or a multi-stage compressor; and/or   a plunger functionally connected to one or more displacement pistons configured to oscillate within a housing, and configured to displace the second fluid to and from the compressor piston, thereby compressing the first fluid therein, preferably wherein oscillation of the or each displacement piston driven by the plunger is facilitated by a lubricant which is fed into the housing via at least one inlet, wherein the lubricant is hydraulic oil, LOHC or an ionic liquid, or mixtures thereof.   
     
     
         14 . A method of compressing a first fluid, the method comprising:
 feeding a first fluid into a compressor piston comprising a piston cylinder and a piston assembly slidably mounted therein, wherein the piston assembly comprises first and second spaced apart piston members defining a space therebetween, which space is configured to contain a second fluid used to cause compression of the first fluid; and   feeding a second fluid to the space between the first and second piston members, and compressing the first fluid.   
     
     
         15 . A method according to  claim 14 , wherein the method uses an apparatus comprising a compressor piston comprising a piston cylinder and a piston assembly slidably mounted therein, wherein the piston assembly comprises first and second spaced apart piston members defining a space therebetween, which space is configured to contain a second fluid used to cause compression of the first fluid, and means for feeding second fluid to the space between the first and second piston members.