Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D19/00—Degasification of liquids
  • B01D19/0005—Degasification of liquids with one or more auxiliary substances
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D19/00—Degasification of liquids
  • B01D19/0042—Degasification of liquids modifying the liquid flow
  • B01D19/0047—Atomizing, spraying, trickling

Definitions

• the invention relates to a method of extracting unwanted gas from a. liquid and has particular application in extracting dissolved air from sea water which is to be pumped into oil wells drilled in the sea bed.
• the yield can be increased by forcing sea water into the well to occupy the space formerly occupied by gas and oil.
• oxygen dissolved in the sea water is reduced to levels of 0.05 parts per million and less, blockage of the reservoir media can occur due to biological growths.
• great difficulty is experienced in removing the required amount of dissolved air from sea water, particularly at the low temperatures which prevail around offshore oil rigs.
• Dissolved gas can be removed from a liquid by adding chemicals which react with the gas.
• this method is normally quite expensive due to difficulties in the transportation and handling of these chemicals when used in offshore systems.
• Another technique is to heat the liquid, preferably to its boiling point. This usually involves excessive energy consumption and, in at least some cases, the liquid must be cooled before it can be used.
• Another method of extracting unwanted gas from a liquid comprises the steps of depressurising the liquid and then passing additional gas through the liquid so as to bring the liquid into intimate contact with the additional gas.
• this method also requires multi- stages, and good gas-liquid contact if excessive consumption of additional gas is to be avoided.
• This purpose is achieved by first pressurising the liquid containing the'unwanted gas, and adding additional gas to the liquid all or part of which is dissolved in the liquid, and then depressurising the liquid so that on desorption of at least part of the additional gas, at least part of the original gas is also stripped from the liquid.
• a method of extracting unwanted gas from a liquid comprising the steps of pressurising the liquid and dissolving additional gas in the pressurised liquid, and then depressurising the liquid so that on desorption of at least part of the additional gas, at least part of the original gas is also stripped from the liquid.
• the additional gas may be of different composition to the unwanted gas and chosen so that, where the unwanted gas is chemically unacceptable, any residual additional gas will be chemically acceptable.
• the unwanted gas is oxygen
• the additional gas can be non-oxidising gas such as nitrogen or a hydrocarbon gas.
• all or part of this gas may be recycled, and all or part of the recycled gas may be passed through a catalytic burner which will remove the unwanted gas from the recycled stream.
• Figure 1 is a schematic arrangement of preferred apparatus for carrying out the invention, incorporating two gas desorbers as disclosed in UK Patent Specification No. 1401 591 ?
• Figure 2 is a schematic arrangement of apparatus similar to that shown in Figure 1, but employing only one gas desorber as disclosed in UK Patent Specification No. 146I 591 ? and
• Figure 3 is a schematic arrangement of a further apparatus for carrying out the invention in a two stage process.
• first and second gas desorbers 1 and 2 have inlet pipes 3 and 4, respectively.
• Each inlet pipe is connected to two nozzles 5 which each has a convergent orifice connected to a four-part desorption tube 6.
• the cross- section of desorption tube 6 increases abruptly between its adjacent parts.
• Pressurised liquid fed through the inlet pipes 3 and 4 issues from the nozzles 5 n the form of divergent jets and, as a result of the reduction in pressure in these jets, at each abrupt change in cross- section of the desorption tube 6, dissolved gas comes out of solution and forms bubbles 7. These bubbles rise to the surface 8 of liquid 9 contained in receptacles 10 and is removed by vacuum suction pumps 11.
• a float 12 operates an actuator 13 when the liquid surface & reaches a predetermined level and the actuator 13 then causes operation of. liquid extraction pump 14.
• the liquid extraction pump 14 of the first device 1 discharges liquid containing a small amount of dissolved gas at pressure into chamber 15. Additional gas from tank 16 is also fed into the chamber 15 so as to dissolve in the liquid. This liquid is then fed through inlet pipe 4 into the second gas desorber 2 where the process of gas desorption is repeated and, as a result, at least part of the gas remaining in the liquid fed to the chamber 15 is withdrawn from the liquid with at least part of the additional gas from tank 16.
• sea water having about ten parts per million of dissolved oxygen is fed into inlet pipe 3 at the rate of 100 thousand gallons per hour.
• the level of dissolved oxygen in the liquid 9 n the receptacle 10 of the first desorber 1 may be reduced to one part per million and this is fed by liquid extraction pump 14, at a pressure of 3 Bars into the chamber 15- Pressurised nitrogen is then fed from tank 16 into chamber 15 so as to ensure that the nitrogen is dissolved in the liquid.
• the liquid with the dissolved nitrogen is then passed through the second desorber 2 which could be at or above atmospheric pressure in order to prevent ingress of further air, ⁇ fo as to maintain the low level of dissolved oxygen.
• the receptacle 10 of the second desorber 2 can therefore also act as a sea water storage vessel for supplying the higj pressure injection pump necessary to force the sea water into the oil well.
• the level of dissolved oxygen in the liquid 9 of the second desorber 2 may be reduced to one hundred parts per billion before it is removed by the pump 14.
• the additional gas was nitrogen, another non-oxidising gas, such as hydrocarbon gas, could be used.
• the second desorber 2 of the apparatus shown in Figure 1 has been replaced by a simple discharge device 17 having a pressure reduction valve 18 at the discharged end of the inlet.pipe 4 from the chamber 15.
• Liquid 19 in receptacle 20 of the discharge device 17 is free of the dissolved gas which escapes in the form of bubbles 21 and this liquid can be withdrawn from the receptacle 20 through valve 22.
• the apparatus of Figure 3 is similar to the apparatus of Figure 1 (and therefore where similarity exists identical reference numerals have been used) but modified so that "the extraction of unwanted gas from the pressurised liquid takes place in two stages. Moreover the apparatus of Figure 3 also utilises the advantages of recycling any undissolved additional gas in the gas desorbers 1 and 2, thus providing economies when a sparingly soluble gas such as nitrogen is used.
• raw pressurised liquid in the inlet pipe 3 instead of being passed directly to the nozzles 5 as in the Figure 1 embodiment, enters a chamber 23 into which additional gas from a tank 24 is fed to dissolve in the liquid.
• the pressurised liquid with the additional gas is then fed to the nozzles 5 of the first device 1, where the process of gas desorption takes place and as a result, at least part of the unwanted gas is withdrawn from the liquid and comes off as bubbles 7 together with any undissolved additional gas.
• the gases from the first gas desorber device 1 are ext r zte ⁇ by the vacuum suction pump 11 as before, but instead of being delivered to atmosphere they are passed through a catalytic burner 25 to clean off the unwanted gas.
• the purified gas now in the form of the additional
• OMPI " gas is delivered to the chamber 15 in the inlet pipe 4 througj. delivery pipe 26 to combine with the additional gas being fed into that chamber 15 from tank 16 for subsequent delivery with the pressurised liquid from extraction pump 14, to the nozzles 5 of the second gas desorber device 2.
• both devices 1 and 2 are operated at atmospheric pressure but-an alternative arrangement would have device 1 operating at a higher pressure than device 2 so that the liquid extraction pump 14 and the pump U in delivery pipe 26, would not be needed.

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• 1983
  • 1983-01-17 EP EP83900428A patent/EP0111488A1/de not_active Withdrawn
  • 1983-01-17 JP JP83500444A patent/JPS59500165A/ja active Pending
  • 1983-01-17 WO PCT/GB1983/000005 patent/WO1983002402A1/en not_active Application Discontinuation
  • 1983-09-14 NO NO833302A patent/NO833302L/no unknown

Non-Patent Citations (1)

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