Supercritical water used fuel oil purification apparatus and process

Abstract

This invention relates to feeding and discharging fluids to and from a high-pressure process and is described using the example of supercritical water treatment of used oil. The apparatus ( 109 ) comprises a fluid feed pump ( 112 ) that feeds unprocessed process fluid into a high-pressure process ( 100 ), a fluid discharge pump ( 114 ) and a fluid pressure buffer system ( 107 ).

What is claimed is: 
     
         1 . A Fluid feed and discharge apparatus for feeding a process fluid to and from a relatively high pressure process including a process infeed and a process out-feed such that, respectively, unprocessed process fluid is fed into and processed process fluid is fed from the high pressure process, the apparatus comprising:
 at least one fluid feed pump for feeding unprocessed process fluid into the high pressure process;   at least one fluid discharge pump for discharging the processed process fluid fed from the high pressure process;   a fluid pressure buffer system including at least one buffer fluid pump that is in fluid communication with the fluid feed and fluid discharge pumps;   
       wherein:
 the fluid feed and fluid discharge pumps each comprise a free piston reciprocally mounted within a cylinder dividing the cylinder into process fluid and buffer fluid sections, the process fluid sections of the cylinders each having a valve controlled inlet and outlet and the buffer fluid sections of the cylinders being in fluid communication by means of the fluid pressure buffer system; 
 the fluid feed pump is connected, at its inlet, to a supply of unprocessed process fluid under relatively low pressure and, at its outlet, to a process in-feed by means of which unprocessed process fluid is fed to the process under process pressure; 
 the fluid discharge pump is connected, at its inlet, to a process out-feed by means of which processed process fluid is fed to the fluid discharge pump under process pressure and, at its outlet, to a processed fluid discharge facility under relatively low pressure; 
 the fluid feed and fluid discharge pumps each include valve means configured alternately to open and close the process fluid sections of the cylinders to relatively high process pressure and relatively low fluid in-feed and discharge pressure in alternating high- and low-pressure cycles in which:
 in the low-pressure cycle, the fluid feed pump inlet and outlet are open and closed respectively to connect the process fluid section of the fluid feed pump to the supply of unprocessed process fluid under relatively low pressure and the fluid discharge pump inlet and outlet are closed and open respectively to connect the process fluid section of the fluid discharge pump to the discharge facility under relatively low pressure; and 
 in the high-pressure cycle, the fluid feed pump inlet and outlet are closed and open respectively to connect the process fluid section of the fluid feed pump to the process by way of the process in-feed and the fluid discharge pump inlet and outlet are open and closed respectively to connect the process fluid section of the fluid discharge pump to the process by way of the process out-feed; 
 
 and the buffer fluid pump is repeatedly operable:
 in the low-pressure cycle, to reciprocate the pistons in the fluid feed pump and fluid discharge pump under the relatively low supply pressure of unprocessed process fluid filling the process fluid section of the fluid feed pump and to discharge the processed process fluid from the process fluid section of the fluid discharge pump to the discharge facility; 
 
 and
 in the high-pressure cycle, to reciprocate the pistons in the fluid feed pump and fluid discharge pump under the relatively high process pressure of processed process fluid filling the process fluid section of the fluid discharge pump and to feed the unprocessed process fluid in the process fluid section of the fluid feed pump by way of the process in-feed to the process under process pressure. 
 
 
     
     
         2 . The fluid feed and discharge apparatus of  claim 1  in which the free pistons reciprocally mounted within the fluid feed and fluid discharge pumps are no more than hydraulically linked to the fluid pressure buffer system. 
     
     
         3 . The fluid feed and discharge apparatus of  claim 1  in which at least one of the free pistons reciprocally mounted within either or both the fluid feed and fluid discharge pumps is mechanically linked to the fluid pressure buffer system, the free piston being connected by means of a piston rod to a piston reciprocally mounted within the buffer fluid pump. 
     
     
         4 . The fluid feed and discharge apparatus of  claim 1 , wherein the unprocessed process fluid is fed from a fluid supply assembly comprising at least two pumps driven in a predetermined ratio to mix and feed the unprocessed process fluid in an equivalent ratio. 
     
     
         5 . The fluid feed and discharge apparatus of  claim 1 , wherein the fluid discharge pump includes a mini-piston configured to penetrate and occlude an enlarged mini-cylinder formed about the opening of the fluid discharge pump outlet, the mini-piston being configured to enter the mini-cylinder and to raise the pressure in the mini-cylinder between the mini-piston and the fluid discharge pump inlet valve to a pressure at or near process pressure. 
     
     
         6 . The fluid feed and discharge apparatus of  claim 1 , further comprising a pipeline pig cleaning system including a pig insertion station, a fluid feed pump pig holdback assembly, a fluid discharge pump pig holdback assembly and a pig recovery station, the pig system including a plurality of pipeline pigs that are configured for feeding into the fluid lines of the apparatus at the pig insertion station and transportation through the fluid lines by the movement of the process fluid through the lines, the fluid feed pump inlet and outlet and the fluid discharge pump inlet and outlet being configured as through-flow, valve controlled lines connected on either side of a combination inlet/outlet line extending from the fluid feed pump and the fluid discharge pump, respectively. 
     
     
         7 . The fluid feed and discharge apparatus of  claim 6  wherein the pig insertion station includes an intermittently operable pig holdback assembly that is configured to release a predetermined quantity of pigs intermittently into the apparatus fluid lines in the low-pressure cycle of the fluid feed and fluid discharge pumps, the pig release being timed to ensure that the pigs are released into the fluid line only when the fluid feed pump inlet valve is fully open and fluid is flowing to the fluid feed pump. 
     
     
         8 . The fluid feed and discharge apparatus of  claim 1 , further comprising at least two additional pumps configured to operate as fluid accumulators, the first pump being open to the process in-feed end of the fluid feed pump and configured to operate as an unprocessed fluid accumulator, the second pump being open to the process out-feed end of the fluid discharge pump and configured to act as a processed fluid accumulator, both accumulators being acted upon by a plunger pump that is in fluid communication with the accumulators and configured to operate the accumulators in contraflow to the fluid feed and fluid discharge pump assembly. 
     
     
         9 . The fluid feed and discharge apparatus of  claim 1 , wherein the apparatus is configured for supercritical water treatment of used oil. 
     
     
         10 . A method of feeding and discharging a process fluid to and from a relatively high pressure process that includes a process in-feed and a process out-feed such that, respectively, unprocessed process fluid is fed into and processed process fluid is fed from the high pressure process, the method comprising:
 from at least one fluid feed pump, feeding unprocessed process fluid into the high pressure process;   from at least one fluid discharge pump, discharging the processed process fluid fed from the high pressure process;   wherein the fluid feed and fluid discharge pumps each comprise a free piston reciprocally mounted within a cylinder dividing the cylinder into process fluid and buffer fluid sections, the process fluid sections of the cylinders each having a valve controlled inlet and outlet and the buffer fluid sections of the cylinders being in fluid communication by means of the fluid pressure buffer system;   connecting a fluid pressure buffer system including at least one buffer fluid pump, in fluid communication with the fluid feed and fluid discharge pumps;   connecting the fluid feed pump, at its inlet, to a supply of unprocessed process fluid under relatively low pressure and, at its outlet, to a process in-feed by means of which unprocessed process fluid may be fed to the process under process pressure;   connecting the fluid discharge pump, at its inlet, to a process out-feed such that processed process fluid is fed to the fluid discharge pump under process pressure and, at its outlet, to a processed fluid discharge facility under relatively low pressure;   the fluid deed and fluid discharge pumps each including valve means configured alternately to open and close the process fluid sections of the cylinders to relatively high process pressure and relatively low fluid in-feed and discharge pressure in alternating high- and low-pressure cycles and the method including the steps of operating the valves such that:
 in the low-pressure cycle, the fluid feed pump inlet and outlet are open and closed respectively to connect the process fluid section of the fluid feed pump to the supply of unprocessed process fluid under relatively low pressure and the fluid discharge pump inlet and outlet are closed and open respectively to connect the process fluid section of the fluid discharge pump to the discharge facility under relatively low pressure; and 
 thereby exposing the process fluid sections of the fluid discharge and fluid feed pump cylinders to low/ambient pressure 
 in the high-pressure cycle, the fluid feed pump inlet and outlet are closed and open respectively to connect the process fluid section of the fluid feed pump to the process by way of the process in-feed and the fluid discharge pump inlet and outlet are open and closed respectively to connect the process fluid section of the fluid discharge pump to the process by way of the process out-feed; 
 thereby exposing the process fluid sections of the fluid discharge and fluid feed pump cylinders to process pressure; 
   and operating the buffer fluid pump repeatedly:
 in the low-pressure cycle, to reciprocate the pistons in the fluid feed pump and fluid discharge pump under the relatively low supply pressure of unprocessed process fluid filling the process fluid section of the fluid feed pump and to discharge the processed process fluid from the process fluid section of the fluid discharge pump to the discharge facility; and 
 in the high-pressure cycle, to reciprocate the pistons in the fluid feed pump and fluid discharge pump under the relatively high process pressure of processed process fluid filling the process fluid section of the fluid discharge pump and to feed the unprocessed process fluid in the process fluid section of the fluid feed pump by way of the process in-feed to the process under process pressure. 
   
     
     
         11 . The method of  claim 10 , further comprising feeding the unprocessed process fluid from a fluid supply assembly comprising at least two pumps and driving the pumps in a predetermined ratio to mix and feed the unprocessed process fluid in an equivalent ratio. 
     
     
         12 . The method of  claim 10 , further comprising, in a transition between high- and low pressure cycles, operating the pumps and valves such that the pressure across the pump pistons and valves is substantially equal at all times. 
     
     
         13 . The method of  claim 10 , wherein the method is for supercritical water treatment of used oil. 
     
     
         14 . (canceled) 
     
     
         15 . (canceled)