A METHOD OF EMPTYING GAS CONTAINERS AND MEANS THEREFOR

Abstract: A method for discharging gas-filled containers to a gas pressure that is lower than a first pressure (P1), whereby the gas in the containers is discharged to a process station (A) or environment in which the first pressure (P1) is maintained. Gas from a first container (1) is made to flow through an ejector (9) to a process station (A), and a second container (2), charged with a gas to a second pressure (P2) is connected via the low-pressure inlet on the injector (9) to the flow of gas through the ejector, whereupon the flow of gas from the first container (1) draws gas from the second container (2). A means for carrying out the method comprising a first gas container (1) charged with a pressure substantially higher than P1 which is connected to an ejector (9) via a line (8) fitted with a valve (7), the gas from the first container (1) being discharged via the ejector to the process station (A) and at least one other container (2), charged with gas at a pressure approximately equal to or less than the first pressure (P1) connected to the gas flow from the first container (1) via a line (1) via a line (14) fitted with a line (17).

Description: A me hod of emptying gas containers and means therefor The present invention concerns a method for discharging gas filled containers to a gas pressure lower than a first pressure, whereby the gas is discharged to a process station environment having the same pressure as the first pressure. Industrial gases in particular are transported and store at a very high pressure, e.g. 200 bar. Depending on the application in question, the gas removed from the containers. used at a variety of pressures, ranging from atmospheric pressure to fairly high pressures, such as 40 bar for certain chemical processes. When gas is to be transferred to a process station with working pressure of 40 bar, only 80% of the gas can be drawn off, if the container initially is charged with gas to a pressure of 200 bar. The remaining 20% cannot be raised to th working pressure of 40 bar without the use of pressure-raisin equipment, such as compressors. However, the use of compressor is both expensive and complicated. Consequently, only 80% of the capacity of the gas container is exploited, with 20% of th gas in the container being transported back and forth between he process station and the filling station. The object of the present invention is to provide a metho and a means of discharging containers filled with gas to a recipient pressure below the working pressure or ambient pressure, without the use of compressors. This object is obtained according to the preamble of clai 1, which method is characterized in that gas in a first container is induced to flow through an ejector to a process station, a second container, containing gas at a second pressure, is connected to the gas flow through the ejector via the ejector's low-pressure inlet, whereupon the gas flow from the first container draws gas from he second container. Preferred embodiments are apparent from the subclaims. The nature of the present invention and its aspects will be more readily understood from the following brief descriptio of the accompanying drawing and discussion related thereto. In the accompanying drawing fig. 1 shows a pressure reduction set-up in four stages; and fig 2 shows a pressure reduction set-up in three stages. Fig 1 shows a pressure reduction set-up for discharging gas containers in four stages to a pressure substantially lower than that against which the containers are working. The working pressure, designated PI, is usually largely constant and is the existing pressure in a process station A or the environment. A container 1 filled to the usual level at a pressure P , e.g 200 bar, is connected via a line 8 fitted with a valve 7 to the high-pressure inlet of an ejector 9. The outlet of the ejector 9 is connected to a line 20, preferably equipped with a valve 21, which is connected to the process station A, whose pressure is PI. A line 13 connected to a low-pressure inlet on the ejector 9 has three branch lines 14, 15 and 16, each of which is fitted with a valve 17, 18 and 19, respectively. All valves 7, 21, 17, 18 and 19 can be set to at least two positions, fully open and fully closed. Each branch line is connected to its own gas-charged container 2, 3 and 4, respectively. When container 1 is connected to line 8 it contains gas at a pressure Pm. When the pressure in container 1 is Pm, container 4 of containers 2, 3 and 4 is charged to the highest pressure P7, which is generally corresponding to the working pressure Pi, container 2 is charged to the lowest pressure P2 and container 3 is charged to a pressure P5, which lies between pressure P7 and pressure P2. Using the method according to the invention, gas is made to flow from container 1, in which the gas pressure at the onset is Pm, through the ejector 9 to the process station A. Valve 17 being open, the gas in container 2 is in communication with the ejector 9 via the low-pressure inlet, with valves 18 and 19 being closed. The gas flowing from container 1 through the ejector 9 draws gas from container 2, causing the pressure inside container 2 to be reduced further. When a predetermined quantity of gas has been discharged from container 1, i.e. when the pressure inside this container has been reduced to a predetermined value P3 the pressure inside container 2 will have been reduced from P2 to P4. As soon as the pressure in container 1 has been reduced to P3, valve 17 is closed and valve 18 is opened. The gas flo ing from container 1 now draws gas from container 3. When the pressure inside container 1 has been reduced to a predetermin second pressure P6, the pressure in container 3 will have bee reduced to approximately P2, which was the initial pressure inside the second container 2. Valve 18 is now closed and val 19 opened so that gas from the fourth container will be drawn to the process station A. When the pressure in container 1 ha been reduced to P8, the pressure in the fourth container 4 wi have been reduced to P5, whereupon valve 19 is closed. If P8 substantially higher, gas will flow from this container to th process station without gas being drawn from any other container via the low-pressure inlet of the ejector 9, until the pressure in the container 1 is roughly equal to PI. The pressures PI and P7 are then also roughly equal. Valve 7, whic can be a valve on the container, is then closed, and container 1 is connected to line 14 in place of container 2, which is almost empt . In the next stage, a new container 5 containing gas at a pressure Pm is connected. When the valve 7 in line 8 is opened valve 18 in line 15 is also opened, since container 3 now has the lowest pressure P2 of the three containers 3, 4 and 1, respectively, connected to line 13. When the pressure in container 3 has been reduced to P4, valve 18 in line 15 is closed and valve 19 opened, with the pressure in container 5 having been reduced to P3. Once the pressure in container 5 ha been reduced to P6, valve 19 is closed and valve 17 opened, an when the pressure in container 5 has been reduced to P8, valve 17 is closed. The pressure in container 1 will now have been reduced to P5, which is lower than PI. There ter, the pressur in container 5 is allowed to be reduced to PI, whereupon the container, with valve 7 closed, is connected to line 15 in place of container 3, which is now almost empty and having a pressure P4. The third stage process in a similar way: a sixth container, charged with gas to the pressure Pm is connected to line 8 and the procedure is repeated in the fourth stage. The set-up shown i Fig. 2 is similar to that in Fig. 1, except that here the method comprises only three stages, which may often be sufficient. Those parts in Fig. 2 that are identical to parts in Fig. 1 are given the same reference numerals . When gas is released from container 1 and allowed to flow through the ejector 9 to the process station, in which the pressure PI, e.g. 40 bar, is maintained, valve 18 is open. The pressure in container 3 is P50. When the pressure in container 1 has been reduced from Pm to P30, which in this example is 100 bar, valve 18 is closed and valve 19 opened to connect the gas in container 4 with the flow of gas from container 1 through the ejector 9. At the time valve 19 is opened, the pressure in container 4 is P70, which is approximately equal to PI, i.e. 40 bar. When the pressure in container 1 has been reduced to P60, which in this example is 50 bar, valve 19 is closed. The pressure in container 4 has now been reduced to P50, which is approximately 10 bar. Since the propelling force from container 1, where the pressure is 50 bar or lower, is sufficient to draw any * substantial quantity of gas from container 4, valve 19 can be closed as the pressure in container 1 is reduced to approximately PI. When the pressure in container 1 is PI, valve 7 is closed and container 1 is connected to line 15 in place of container 3, which is now almost empty. A new container 5, charged with gas to a pressure Pm, is connected to line 8 and valves 7 and 19 are opened simultaneously. The pressure in container 4 is P50, i.e. 10 bar. When the pressure in container 5 has been reduced to P30, i.e. 100 bar, valve 19 is closed and valve 18 opened. The pressure in container 4 is P50, which, in this example is 2 bar. When the pressure in container 5 has been reduced to P60, i.e. 50 bar, valve 18 is closed, breaking the communication between the gas flow from container 5 and container 1, and the pressure in container 5 is then lowered to PI, i.e. 40 bar. In the third stage, container 5 is disconnected from line 8, and then connected to line 16 in place of container 4. A container 6, charged to a pressure Pm is now connected to line 8 in place of container 5. Valves 18 and 7 are then opened simultaneously, whereupon the flow of gas from container 6 draws gas from container 1, which, at the time valve 18 is opened is charged with gas to the pressure P50, i.e. 10 bar. When the pressure in container 6 has been reduced P30, valve 1 is closed and valve 19 opened, container 5 in communication with the flow of gas from container 6, and the pressure in container 1 has been reduced to P2, i.e. 2 bar. Thus, this method makes it possible to reduce substantially the quantity of gas that is transported back an forth between the filling station and the process station.

Claims: CLAIMS 1. Method of discharging gas from gas filled containers to a gas pressure that is lower than a first pressure (PI) , whereby the gas in the containers is transferred to a process station (A) or environment, in which the first pressure (PI) is maintained, c h a r a c t e r i z e d in that gas from a first container (1) is made to flow through an ejector (9) to the process station (A), a second container (2), containing gas at a second pressure (P2) is connected to a low-pressure inlet of the ejector (9), whereby the gas flow from the first container (1) draws gas from the second container (2). 2. Method according to Claim 1, c h a r c t e r i z e d in that the gas connection between the second container (2) and the ejector (9) is broken when the pressure in the first container (1) has been reduced to a predetermined third pressure (P3), whereby the gas pressure in the second container (2) has been reduced to a fourth pressure (P4), and in that a third container (3), charged with a fifth pressure (P5), which is higher than the second pressure (P2), is connected to the gas flow from the first container (1) via the low-pressure inlet of the ejector (9), whereupon the flow of gas from the first container (1) draws gas from the third container (3). 3. Method according to Claim 2, c h a r a c t e r i z e d in that the gas connection between the third container (3) and the ejector (9) is broken when the pressure in the first container (1) has been reduced to a predetermined sixth pressure, whereby the gas pressure in the third container (3) has been reduced to the second pressure (P2), and in that a fourth container (4), containing gas having a seventh pressure (P7), which is higher than the fifth pressure (P5), is connected to the gas flow from the first container (1) via the low-pressure inlet of the ejector (9), whereupon the gas flow from the first container (1) draws gas from the fourth container (4). 4. Method according to Claim 2, c h a r a c t e r i z e d in that the gas connection between the third container (3) and the gas flow from the first container (1) is broken when the pressure in the container (1) has been reduced to a predetermined sixth pressure (P6), whereby the gas pressure in the third container will have been reduce to the second pressure (P2), and in that gas from the first container (1) is possibly made to flow to the process station (A) until the pressure in the container (1) is approximately equal to PI, whereupon the first container (1) is replaced by a fifth container (5), which is charged with gas to an eighth pressure (P8), the gas connection between the third container (3) and the ejector (9) is reestablished and gas from the fifth container (5) is made to flow through the ejector (9) until th pressure in the fifth container (5) has been reduced to the third pressure, whereby the pressure in the third container has been reduced to the fourth pressure (P4) . 5. Method according to Claim 4, c h a r a c t e r i z e d in that the gas connection between the third container (3) and the ejector (9) then is broken and the first container is connected to the ejector (9), which container (1) is replacing the third container (3) . 6. Apparatus for discharging container filled with gas to a gas pressure that is lower than a first pressure (PI), whereby the gas in the containers is discharged to process station (A) or environment in which the first pressure (PI) is maintained, c h a r a c t e r i z e d in that it comprises a first gas container (1), charged with gas at a pressure substantially higher than (PI), being connected to an ejector (9) via a line (8) fitted with a valve (17), whereby the gas from the container (1) is discharged via the ejector (9)to the process station (A), and at least a gas container (2), charged with gas at a pressure approximately equal to or less than the first pressure (PI), which container (2) can be connected via a line (17) fitted with a valve (14) to the flow of gas from the first container (1) .

Inventors: AHLBLAD KARL JOHAN, AHLBLAD, KARL, JOHAN
Applicants: AGA AB, AGA AKTIEBOLAG
Application year: 1987
Main classification: F17C7
IPC codes: F17C7