US 3350890 A
Description (OCR text may contain errors)
Nov. 7, 1967 L. T. COPE 3,350,890
PROCESS FOR TRANSFERRING LIQUEFIED GASES Filed Jan. 5, 1966 LOU/5 r COPE INVENTOR.
F paw/979; 7,
AGENT United States Patent 3,350,890 PROCESS FOR TRANSFERRING LIQUEFIED GASES Louis T. Cope, Atlanta, Ga, assignor to Olin Mathieson Chemical Corporation Filed Jan. 5, 1966, Ser. No. 518,920 3 Claims. (CI. 62-45) ABSTRACT OF THE DISCLOSURE Liquefied gas is transferred from a storage container to a receiving container by pumping liquid for 1 to 30 seconds, discharging gas from the storage container for 1 to 30 seconds and alternating these operations until the receiving container is filled with liquefied gas.
This invention relates to a method for the transfer of liquefied gases from a first container to a second coritainer. The method is applicable to all of the commonly liquefied gases including, for example, carbon dioxide, ammonia, chlorine, methane, ethylene oxide and various Freons. The invention is described below more particularly with respect to carbon dioxide.
Carbon dioxide is commonly stored in bulk storage plants throughout the country under a pressure usually in the range of from 280 to 305 p.s.i.g. and at a temperature of about 0 F. The containers are insulated and refrigerated to maintain liquid and gas under these conditions. Various pumps are known to the art for the purpose of transferring liquid carbon dioxide from such storage containers to smaller containers having capacities usually ranging from 5 to 150 pounds. The prior art has generally required pumps for this purpose to be capable 3 of pumping against a pressure differential of several hundred p.s.i. Such pressures were required because the liquid being pumped into the receiving container is heated rapidly on contact with the Warm container. Pressure in the container rises and, by the time the container is filled, the pressure in the container often corresponds to ambient temperature, for example, about 800 p.s.i.g. or more.
Low priced cylinder filling pumps, for example, the SCS LT pump, has a rated capacity of about '6 pounds of CO per minute and requires a 2 H.P. motor plus a gear reduction device in order to develop enough power to pump against high pressures. Such prior systems require a heavy source of current for the electrically operated pump and may cost from $1500 to $2000.
llf standard CO cylinders had a vapor return line, the cylinders could be filled by gravity. A pump to raise the pressure about 100 psi. above storage pressure would fill the cylinders much faster.
One object of this invention is to provide a method for filling liquefied gas cylinders in common use by means avoiding the necessity of expensive, high pressure pumps requiring correspondingly expensive valves, fittings and pipes. Another object is to provide a method which is inexpensive, rapid and effective for filling containers with liquefied gas under pressure. The method of this invention requires only readily available equipment and the cost of the equipment at present market prices is about $200.
The method of this invention transfers liquefied gas from a storage container to a receiving container by (1) pumping said liquefied gas at a pressure exceeding the pressure in said storage container into said receiving container for a period of from 1 to 30 seconds, (2) discharging vaporized gas from said receiving container into said storage container for a period of from 1 to 30 seconds and repeating said 1) pumping and said (2) discharging until said receiving container is filled With liquefied gas.
Advantageously a circulation is first established by priming the pump with liquefied gas from the storage container by pumping through an open line to atmospheric pressure. As soon as liquid is being pumped, it is valved through a line returning to the storage container. With the receiving container valved to the discharge side of the pump, the valve in the circulation line to the storage container is closed and liquid flows into the receiving container. After a period of from 1 to 30 seconds, for example, about 5 seconds, an alternating valve in the line from the discharge side of the pump is opened to return vaporized gas to the storage container for a similar period. These periods of filling with liquid and removal of vaporizcd gas are alternated until the receiving container is sufiiciently filled. The alternating valve is closed, the valve in the circulation line is opened and the valve in the line to the receiving container is closed. The container is removed and replaced by another receiving container to be filled and the process is repeated. The system is shut down by closing all the valves, shutting down the pump and opening one of the valves from the pump to the atmosphere or suitable discharge vent.
Advantageously, the alternating valve controlling the flow of liquid into the receiving container and the flow of vaporized gas therefrom is electrically operated. It is suitably a gate valve or other type of valve operable by a solenoid. A timer controls the current to the solenoid and opens and closes the valve at preset intervals. The flow of liquid into the receiving container and the flow of vaporized gas from the receiving container are both rapidly pulsating. After the pressure of gas in the receiving container is relieved, liquefied gas flows thereinto at lower differential pressure. The pump is suitably a low cost, standard gear pump or other suitable type generally used for circulating systems and designed to pump against pressures of up to about psi.
The figure herewith illustrates the method of the invention in which pump 11 is arranged to remove liquid from storage container 12 via line 13 controlled by valve 34 to transfer the liquid into line 14. Gas is returned to storage container 12 via line 15 controlled by valve 35. Line 14 carries branches 16, 17 and 18 with valves 1?, 20 and 21 respectively. Valve 19 is a safety valve, valve 20 controls the How in circulation line 17 and valve 21 controls the flow in line 18 to container 22. Line 14 terminates in alternating valve 23 which controls flow into gas return line 15. Alternating current is supplied via lines 24 through master switch 25 and lines 26 to pump 11. Current also fiows via lines 27 through control switch 28 and lines 29 to timer clock 30 in timer 31. The clock opens and closes the circuit in lines 32 to solenoid 33 which opens and closes valve 23 at preset intervals.
In operation, valves 34 and 35 are opened, master switch 25 is closed and pump 11 is operated with container 22 detached, valve 21 open and valve 2%) closed until the pump is primed with liquefied gas from storage container 12. Valve 20 is opened and valve 21 is closed, establishing circulation in line 17. Container 22 is attached and valves 20 and 21 are reversed. Control switch 23 is closed starting the clock 30 in timer 31. It is set to energize solenoid 23 to open and close valve 23 at 5 second intervals. When valve 23 is closed, liquid flows into container 22. When valve 23-is open, gas from line 14, pump 11 and container 22 flows via line 15 back to storage container 12. When container 22 is filled, control switch 28 is opened, valve 29 is opened and valve 21 is closed. Container 22 is replaced by an empty container to be filled and the process is repeated to fill as many containers as desired. To discontinue operations, control switch 28 and master switch 25 are opened, valves 34 and 35 in lines 13 and 15 are closed and valve 21 is opened.
Example In a system essentially as shown in the attached figure, gaseous and liquid carbon dioxide was stored in a storage container at 300 p.s.i.g. and F. The pump was a small gear pump operated by a fractional horsepower motor and was capable of developing about 100 p.s.i.g. pressure above that of the liquid supplied to it. The pump Was primed with liquid carbon dioxide by discharging to atmospheric pressure until the pump was cooled and filled with liquid. The discharge valve was closed and the valve to a circulation line was opened, circulating liquid back to the storage container.
The first of several small cylinders to be filled was connected to the filling line, the cylinder valve was opened and the valve in the filling line was opened. The valve in the circulating line was closed and current was supplied to the timer and through it to the solenoid operating the alternating valve. The timer was set to open and close the alternating valve on a 5 second cycle. When the valve was closed, liquid carbon dioxide was introduced into the cylinder at pressures up to 400 p.s.i.g. When the valve was opened, gaseous carbon dioxide vaporized mainly from the cylinder was returned at pressures decreasing to 300 p.s.i.g. In about 1% minutes the pound cylinder was substantially filled with liquid carbon dioxide. Current was cut off to the alternating valve which then remained closed, the valve in the filling line was closed and the valve in the circulating line was opened. The filled cylinder was disconnected. Additional cylinders were similarly filled.
What is claimed is:
1. Method for transferring liquefied gas from a storage container to a receiving container by (1) pumping said liquefied gas at a pressure exceeding the pressure in said storage container into said receiving container for a period of from 1 to seconds, (2) discharging vaporized gas from said receiving container into said storage container for a period of from 1 to 30 seconds and repeating said (1) pumping and said (2) discharging until said receiving container is filled wtih liquefied gas.
2. Method of claim 1 in which said pumping pressure exceeds the pressure in said storage container by less than p.s.i.g.
3. Method of claim 1 in which said liquefied gas is carbon dioxide.
References Cited UNITED STATES PATENTS 2,362,984 1l/ 1944 Boshkoff 6253 2,387,894 10/1945 Fannin 62-55 3,234,746 2/1966 Cope 62-53 LLOYD L. KING, Primary Examiner.