Liquid purification or separation – Processes – Chemical treatment
Patent
1996-01-11
1998-03-10
Nessler, Cynthia L.
Liquid purification or separation
Processes
Chemical treatment
210763, C02F 170
Patent
active
057257817
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for exhaustive catalytic deoxygenation of water of various origins and most particularly of seawater. It also relates to the catalyst employed for making use of the said process and also deals with the preparation of this catalyst.
The maintenance of oil deposits, especially offshore deposits, at pressure and/or the improved recovery of the oil oblige the producers of offshore oil to inject seawater into the deposit being exploited. Such a process makes it necessary for this water to be treated before injection into the deposit. This is why a bactericidal chlorination treatment is generally carried out first of all, followed by a multistage filtration so as to remove any suspended matter that could give rise to possible blockages in the device for injecting this seawater and also in the deposit and in the production wells. Finally, exhaustive deoxygenation of the seawater must be carried out after filtration, otherwise it is to be feared that very considerable risk of corrosion of the plant will arise, with financial consequences that can be imagined.
To bring about of the abovementioned deoxygenation of seawater, the techniques conventionally employed are stripping using oxygen-free gases or the application of partial vacuum. These two techniques are today proven and effective because they make it easily possible to achieve a residual oxygen content in the treated seawater which is of the order of 50 ppb (1 ppb=1.times.10.sup.-7 % by weight).
These techniques also have some intrinsic disadvantages. It is known, for example, that gas stripping always acidifies the water a little because of the CO.sub.2 which is always present. In addition, the traces of oil which are entrained in the stripping gas, despite the most efficient demisting techniques, may present problems of blocking throughout the production plants. The use of vacuum degassing towers does not present any difficulties of this kind but, on the other hand, has the disadvantage of using rotary machines which must be reliably maintained and the operation of which requires the installation of structures which are particularly costly at sea.
It is known that the oxygen present in low concentration in fresh water can be removed by in-situ reaction with hydrogen, predissolved in the water to be treated, carried out in contact with a solid catalyst based on palladium or platinum, dispersed on a granular solid support. Thus, reference U.S. Pat. No. 4,789,488 describes a process of this type for the deoxygenation of boiler waters which contain of the order of 8 ppm of oxygen in the dissolved state, by employing a catalyst based on finely divided palladium or platinum on a support consisting of a polystyrene anion-exchanger resin and by operating at temperatures of between approximately 15.degree. C. and 40.degree. C.
Reference U.S. Pat. No. 3,052,527 relates to the removal of the oxygen present in water by passing a stream of the water to be treated through a bed of an activated absorbent consisting of palladium or platinum deposited on activated carbon, which absorbent contains hydrogen that is chemisorbed by keeping the said adsorbent in a hydrogen atmosphere between two passes of the water to be treated in contact with the bed of activated adsorbent.
Reference EP-A-0 316 569 proposes a process for the removal of the oxygen present in water, especially drinking water, by catalytic hydrogenation in the presence of a catalyst consisting especially of palladium and/or of platinum on a support formed by, for example, activated carbon. In this process the water to be treated is sprayed onto a bed of the said catalyst placed in a reaction zone filled with hydrogen, the water is allowed to flow or trickle through the catalyst bed and the treated water is then removed out of the said zone. The process is used at temperatures ranging from 0.degree. C. to 100.degree. C. and especially at temperatures close to the ambient and at hydrogen pressures ranging from 1 to 10 bars and in particular from the ambien
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Barbier Jacques
Bousquet Jacques
Volle Jean-Luc
Elf Aquitaine Production
Nessler Cynthia L.
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