WO2001085622A1

WO2001085622A1 - Apparatus and method for de-oxygenating a fluid

Info

Publication number: WO2001085622A1
Application number: PCT/GB2001/002067
Authority: WO
Inventors: Edward Gobina
Original assignee: The Robert Gordon University
Priority date: 2000-05-11
Filing date: 2001-05-11
Publication date: 2001-11-15
Also published as: AU5648001A; GB0011277D0; GB0227746D0; GB2378699A; GB2378699B

Abstract

An apparatus (1) and method for use in de-oxygenating water, in particular sea water for use offshore where it may be injected into hydrocarbon reservoirs to increase the recovery rate of the hydrocarbons. The apparatus (1) comprises a substantially porous member (12) being provided with a catalyst means such as palladium and at least one inlet (16, 18) and one outlet (20, 22) for input of the oxygenated water and recovery of the de-oxygenated water. The sea water and hydrogen are introduced into the apparatus (1), the hydrogen typically being dispersed by the porous member (12). Excess oxygen in the water reacts with the hydrogen, thus de-oxygenating the water.

Description

"Apparatus and Method for De-oxygenating a Fluid"

The present invention relates to an apparatus and method for de-oxygenating a fluid, and particularly, but not exclusively, relates to an apparatus and method for de-oxygenating water such as sea water. The present invention also finds utility in the removal of nitrates from ground water and in the food industry for increased efficiency of the hydrogenation of fats and oils.

Conventionally, it is known to use water injection systems to increase the lifespan of oil and gas wells. These water injection system comprise injecting water into the production zone of the well, thereby increasing the pressure of total fluid within the production zone such that the production rate of produced fluids (including hydrocarbons and injected water) is increased. However, it is important to be able to inject de-oxygenated water into the well, since the dissolved oxygen in the water is highly likely to corrode ferrous wellhead and subsea 1 structures, which can mean extremely costly remedial

2 work being required. 3

4 One example of a conventional de-oxygenation system,

5 which is particularly useful on offshore platforms is

6 the "Seaject" (™) offered by Axsia Serck Baker, such

7 as is described in the November 1999 edition of

8 Offshore magazine. However, the economics of

9 offshore platforms is such that it is important to be LO able to reduce the size and weight of equipment used, LI including de-oxygenation equipment.

L2

L3 According to a first aspect of the present invention,

L4 there is provided an apparatus for use in

L5 hydrogenating a fluid, the apparatus comprising a

L6 substantially porous member being provided with a

L7 catalyst means, and at least one inlet port for the

L8 fluid and a hydrogenating material, and at least one

L9 outlet port for the substantially hydrogenated fluid,

20 the apparatus being arranged such that at least the

21 hydrogenating material is capable of contacting the

22 catalyst means and reacting with an oxidisable

23 component in the fluid. 24

25 According to a second aspect of the present

26 invention, there is provided a method of

27 hydrogenating a fluid, the method comprising

28 providing a substantially porous member having a

29 catalyst means, and at least one inlet port for the

30 fluid and a hydrogenating material, and at least one outlet port for the substantially hydrogenated fluid; and passing the fluid and the hydrogenating material into the substantially porous member such that at least the hydrogenating material contacts the catalyst means and reacts with an oxidisable component in the fluid.

The fluid may be water, and may be seawater. The oxidisable component may be oxygen which may be dissolved in the water/sea water. Alternatively, the fluid may be ground water, and the oxidisable component may be nitrates dissolved in the water. Alternatively, the oxidisable component may be unsaturated fat or unsaturated oil. Preferably, the substantially porous member is a membrane, and is preferably porous to gas. Preferably, the membrane is formed from a ceramic material. Typically, the hydrogenating material is hydrogen gas (H₂) .

The membrane may be tubular, and may be impregnated with the catalyst means. Alternatively, the catalyst means may be formed on an inner surface of the membrane, or may be provided within a bore of the membrane. Preferably, the catalyst means is a noble metal, and may be platinum metal or alternatively may be palladium metal, or may be nickel metal.

Typically, a second inlet port may be provided for the hydrogenating material, and the first inlet port may be provided for the fluid to be hydrogenated. A second outlet port may be provided for exhausting unused hydrogenating material .

According to a third aspect of the invention there is provided a method of impregnating the substantially porous member of the first or second aspects of the invention with a catalyst means, the method comprising the steps of dipping the member into a salt solution to coat the member and drying the coated member.

Preferably, the method further comprises the steps of reducing the coated member with hydrogen at elevated temperatures .

According to a fourth aspect of the invention there is provided a method for adding a layer onto the substantially porous member of the first or second aspects of the invention wherein the layer is provided on the member by dipping the member into a precursor to coat the member then drying the coated member.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: -

Fig. 1 is a schematic view of an apparatus for de-oxygenating sea water, in accordance with the present invention; Fig. 2a is a first alternative arrangement for the apparatus of Fig. 1 with the oxygenated water having been pre-mixed with Hydrogen gas; Fig. 2b is a second alternative arrangement of the apparatus of Fig. 1; Fig. 2c is a third alternative arrangement of the apparatus of Fig. 1; and Fig. 2d is a schematic representation of the apparatus of Fig. 1.

Fig. 1 shows a catalytic reactor 10 within a compact de-oxygenation system generally designated at 1. The catalytic reactor 10 comprises a tubular membrane 12 which is preferably surrounded by a tubular stainless steel shell 14. The membrane 12 may be formed from a material such as ceramic, the material being substantially porous, particularly to a gas such as hydrogen .

The catalytic reactor 10 comprises a first input port 16, a second input port 18, and a first output port 20.

A first embodiment 25 of the catalytic reactor is shown in Fig. 1, wherein a catalyst, such as a noble metal, is provided on the inner surface of the bore 31 of the tubular membrane 12, such as in the form of a coating provided thereon. A second embodiment 27 of reactor 10 is also shown in Fig. 1, where the second embodiment 27 is provided with a catalyst, such as a noble metal, provided in a matrix 29 which is located within the bore 31 of the tubular membrane 12 to provide a solid porous tube. The matrix 29 may be formed from a porous material, such as ceramic, and may preferably be formed from the same material as the tubular membrane 12, where the matrix 29 may be formed from crushing the ceramic material, mixing it with the catalyst, and inserting it into the bore 31.

The catalyst is preferably a noble metal, such as platinum or palladium.

A method of de-oxygenating water, such as sea water on an offshore platform, will now be described. Sea water, with oxygen naturally dissolved therein, is pumped into the first inlet port 16, and flows through the bore 31, since the first inlet port 16 is coupled directly to the bore 31. Substantially pure hydrogen, created by a hydrogen generator 33 is fed into the second input port 18. The hydrogen will travel through the side wall of the porous tubular member 12, since the second input port 18 is coupled directly to the sidewall of the porous tubular member 12, and thereafter through the inner surface of the bore 31, such that it mixes with the oxygenated sea water within the bore 31. However, the hydrogen will also travel through axial length of the side wall of the tubular member 12 along its length, defusing through the inner surface of the bore 31. The hydrogen generator is provided with a fresh water supply, and with a power supply, and is also provided with a coolant supply, which may be the seawater.

In the case of the first embodiment 25 of the reactor 10, the hydrogen (H₂) will be activated by the catalyst formed on the inner surface of the tubular membrane 12, and will hence react with the oxygen (0₂) within the sea water according to the following equation: -

to create pure water (H₂0) , and hence the sea water (which has now been de-oxygenated and which includes the pure water produced by the chemical reaction) is permitted to exit the bore 31 through output port 20.

In the case of the second embodiment 27 of the reactor 10, the hydrogen (H₂) reacts with the catalyst within the solid porous tube 31 and with the free oxygen within the sea water, such that pure water (H₂0) is produced, and again the sea water (which has been de-oxygenated, and which includes the pure water) exits the tubular membrane 12 through the output port 20.

As shown in Fig. 2c, the first embodiment 25 of the reactor 10 can be provided with a second output port 22, such that any surplus of hydrogen gas (H₂) that does not pass through the inner surface of the bore 31 can travel out of the side wall of the tubular member 12, such that it may be recycled for subsequent use by exiting through the second output port 22. A schematic diagram of the apparatus of Fig. 1 is shown in Fig. 2d with the addition of a second output port 22, with the first embodiment 25 of the reactor 10 in use.

Alternatively, the second embodiment 27 of the reactor 10 is shown in Fig. 2a, with the hydrogen gas (H₂) and the oxygenated sea water (H₂0 + 0₂) being pre-mixed and thereafter pumped into the first inlet port 16. Alternatively, as shown in Fig. 2b, the hydrogen gas (H₂) and oxygenated sea water can be pre-mixed and inserted into the first inlet port 16, and can react with a combination of the first 25 and second 27 embodiments; that is, the catalyst being provided in the matrix 29 within the bore 31, and also being provided on the inner surface of the bore 31 in a coating thereon, such that the de-oxygenated sea water passes out of the reactor 10 through second outlet port 22.

Alternatively, the porous ceramic membrane 12 may be impregnated with the catalyst material, such as a noble metal, and preferably may be impregnated with a noble metal such as platinum or palladium.

The embodiments of the present invention provide the advantages that weight is minimised, and hence a compact de-oxygenation system is provided. In addition, the small size of the catalyst, which is highly disbursed within the membrane 12 matrix will enhance the reaction rate and eliminate mass transfer resistance which is often encountered in more traditional packed bed configurations, such as that currently used in the "Seaject" ™ process. In addition, the use of a pre-mixer for pre-mixing the hydrogen and sea water can be eliminated since the hydrogen defuses through the membrane 12 in the form of a very fine mist. A further advantage is the elimination of micro-bubbles. Further advantages of this reactor 10 configuration include operational flexibility, for instance : -

1) Multi-pass operation with different hydrogen partial pressure per pass; 2) Continuous versus batch operation; and 3) Operation with either pre-mixed or separated reactants.

The porous ceramic membrane tube 12 may be an alpha- alumina tube, of 8mm to 50mm outer diameter and 5mm to 47mm inner diameter, having between 50nm and 180nm pores. The permeating portion of the membrane may be in the region of lm in length, and the remaining portions may be glazed with an Si0₂ - BaO - CaO sealant at 1100°C. The layer onto which the catalyst is to be impregnated may be a gamma-alumina layer formed with a boemite solution. The concentration of the boemite sol may be maintained at 0.6 mol/L. With the lower end of the support tube plugged, the outer surface of the unglazed portion may be dipped in the boemite solution for 1 to 5 minutes. After dipping, the membrane may be air-dried overnight . The dry membrane may then be heated to between 700-750°C at a rate of l°C/min. It may be necessary to repeat this dripping - drying - firing sequence for up to a total of three processings to achieve the required gamma- alumina layer thickness on this membrane.

The catalyst may be deployed in the gamma-alumina layer by wet impregnation. This would involve dipping the membrane in the metal salt solution, drying and reducing at a temperature between 400- 450°C in a stream of hydrogen. This will ensure a highly dispersed metal within the thin gamma-alumina layer.

The working temperature of the method may be in the range of 0°, 10° and 15 °C, although the efficiency of the system may be increased with increased temperatures, although this may result in higher running costs.

Modifications and improvements may be made to the embodiments without departing from the scope of the invention. For instance, the membrane 12 can be used to remove nitrates from water, since nitrate is an oxidisable component. Alternatively, the membrane 12 can be used to transfer hydrogen into unsaturated fats and/or unsaturated oils, which will result in the production of saturated fats and/or saturated oils respectively. In this latter scenario, it is preferred that a noble metal catalyst, such as nickel, is used.

Claims

1. An apparatus for use in hydrogenating a fluid, the apparatus comprising a substantially porous member being provided with a catalyst means, and at least one inlet port for the fluid and a hydrogenating material, and at least one outlet port for the substantially hydrogenated fluid, the apparatus being arranged such that at least the hydrogenating material is capable of contacting the catalyst means and reacting with an oxidisable component in the fluid.

2. An apparatus as claimed in claim 1, wherein the substantially porous member is a membrane.

3. An apparatus as claimed in claim 2, wherein the membrane is made from a ceramic material .

4. An apparatus as claimed in any preceding claim, wherein the substantially porous member is tubular.

5. An apparatus as claimed in any preceding claim, wherein the substantially porous member is impregnated with the catalyst means.

6. An apparatus as claimed in claim 5, wherein a layer is provided on the substantially porous member, the catalyst means being impregnated into the layer.

7. An apparatus as claimed in claim 6, wherein the layer is gamma alumina.

8. An apparatus as claimed in any preceding claim, wherein the catalyst means is provided on an inner surface of the substantially porous member.

9. An apparatus as claimed in any preceding claim, wherein the catalyst means is provided within a bore of the substantially porous member.

10. An apparatus as claimed in claim 9, wherein the catalyst means is provided within a matrix support.

11. An apparatus as claimed in any preceding claim, wherein the catalyst means is a noble metal.

12. An apparatus as claimed in claim 11, wherein the catalyst means comprises at least one of platinum, palladium and nickel.

13. An apparatus as claimed in any preceding claim, wherein the fluid is water.

14. An apparatus as claimed in claim 13, wherein the fluid is sea water.

15. An apparatus as claimed in any preceding claim, wherein the oxidisable component is oxygen.

16. An apparatus as claimed in any one of claims 1 to 14, wherein the fluid is water, and the oxidisable component is a nitrate.

17. An apparatus as claimed in any one of claims 1 to 14, wherein the oxidisable component is at least one of unsaturated fat and unsaturated oil .

17. An apparatus as claimed in any preceding claim, wherein the hydrogenating material is hydrogen gas.

18. An apparatus as claimed in any preceding claim, wherein a second inlet port is provided for the hydrogenating material, and the first inlet port is provided for the fluid to be hydrogenated.

19. An apparatus as claimed in any preceding claim, wherein a second outlet port is provided for exhausting unused hydrogenating material.

20. A method of hydrogenating a fluid, the method comprising providing a substantially porous member having a catalyst means, and at least one inlet port for the fluid and for a hydrogenating material, and an outlet port for the substantially hydrogenated fluid; and passing the fluid and the hydrogenating material into the substantially porous member such that at least the hydrogenating material contacts the catalyst means and reacts with an oxidisable component in the fluid.

21. A method as claimed in claim 20, wherein the hydrogenating material passes through at least a portion of the substantially porous member.

22. A method as claimed in claim 21, wherein the hydrogenating material is diffused after passing through the substantially porous member.

23. A method of impregnating the substantially porous member of any preceding claim with a catalyst means, the method comprising the steps of dipping the member into a salt solution to coat the member and drying the coated member.

24. A method as claimed in claim 23, wherein the method further comprises the steps of reducing the coated member with hydrogen at elevated temperatures.

25. A method for adding a layer onto the substantially porous member of any preceding claim, wherein the layer is provided on the member by dipping the member into a precursor to coat the member then drying the coated member.