The present invention concerns a marine platform, preferably an underwater machine, comprising:
- a reforming unit suitable for producing a syngas from at least one fuel, the syngas
comprising dihydrogen at a first volume concentration, carbon dioxide and carbon
10 monoxide;
- a filtration unit suitable for filtering the syngas and producing a filtered gas
comprising dihydrogen at a second volume concentration that is greater than the first
concentration, carbon monoxide at a third volume concentration and carbon dioxide at a
fourth volume concentration; and
15 - at least one fuel cell.
The invention also concerns a corresponding method.
In said marine platform, the reforming unit produces hydrogen-rich syngas intended
to be converted to electricity in the fuel cell in the presence of dioxygen. A filtration unit is
added to produce a filtered gas proportionally comprising more dihydrogen than syngas.
20 Nevertheless, drops in fuel cell performance have been ascertained which can be
remedied by purging the cell. However, said purging creates a risk of polluting the inner atmosphere of the marine platform with compounds contained in the filtered gas such as carbon monoxide.
It is therefore one objective of the invention to provide a marine platform having
25 better performance whilst maintaining safety.
For this purpose, the subject of the invention is a marine platform of the type
described above, further comprising a methanation unit configured to receive the filtered
gas and to transform this gas into a treated gas, the methanation unit being configured to
synthesize methane from the dihydrogen and carbon monoxide contained in the filtered
30 gas, the treated gas comprising carbon monoxide at a fifth volume concentration of less
than 1 ppm, the fuel cell being configured to receive the treated gas and to produce electricity.
In particular embodiments, the marine platform comprises one or more of the following characteristics taken alone or in any possible technical combination:

2
- the methanation unit is configured to allow the passing into the treated gas of at least 97 % of the carbon dioxide contained in the filtered gas;
- the methanation unit comprises a catalyst comprising nickel and/or c ruthenium;
- the third concentration is less than 500 ppm, preferably less than 300 ppm, and
5 more preferably less than 150 ppm;
- the second concentration is greater than 90 %, preferably greater than 95 %, and more preferably greater than 97 %;
- the fourth concentration is between 50 and 200 times the third concentration;

- the filtered gas is received in the methanation unit at a temperature of between 200 10 °C and 350 °C, preferably lower than 300° C, and more preferably lower than 250 °C;
- the filtration unit comprises a metal membrane; and
- the filtered gas is composed of at least 99.9 volume % of dihydrogen, carbon
monoxide, carbon dioxide, water vapour and methane.
A further subject of the invention is a method comprising the following steps:
15 - obtaining a marine platform such as described above;
- in the reforming unit, producing the syngas from at least the fuel;
- filtering the syngas and producing the filtered gas in the filtration unit;
- in the methanation unit, receiving the filtered gas and transforming the filtered gas into the treated gas; and
20 - in the fuel cell, receiving the treated gas and producing electricity.
The invention will be better understood on reading the following description given solely as an example and with reference to the appended drawing in which Figure 1 is a schematic view of a marine platform of the invention.
With reference to the single Figure 1, a marine platform 1 is described according to
25 the invention.
For example, the marine platform 1 is an underwater machine, or as a variant a surface construction.
The marine platform 1 comprises at least one source 3 suitable for providing a fuel
5, and advantageously a source 5A suitable for providing dioxygen 5B and a source 6A
30 suitable for providing steam 6B.
The marine platform comprises a reforming unit 7 suitable for producing a syngas 9 from the fuel 5, dioxygen 5B and steam 6B.
The marine platform 1 comprises a filtration unit 11 suitable for filtering the syngas
9 and to produce a filtered gas 13 enriched with dihydrogen, and to produce one or more
35 residues 15.

3
In one particular embodiment, the marine platform 1 comprises one or more tanks 17 to stock the residue(s) 15.
In another embodiment, not illustrated, the residues are discharged outside the
marine platform 1. The tanks 17 are therefore unnecessary.
5 The marine platform 1 comprises a methanation unit 19 configured to receive the
filtered gas 13 and to transform the same into a treated gas 21. The marine platform 1
comprises a fuel cell 23 configured to receive the treated gas 21 and to produce electricity
25. The marine platform 1 advantageously comprises a source 27 suitable for providing an
oxidizer 29 to the fuel cell 23. The marine platform optionally comprises a tank 31 suitable
10 for storing one or more residues 33 originating from the fuel cell 23.
In the example, the residues 33 are water which is advantageously used to produce at least part of the steam 6B in source 6A.
The fuel 5 is advantageously a mixture of hydrocarbons, or methanol.
The mixture of hydrocarbons is diesel oil for example or any other usual fuel on a
15 marine platform.
The source 3 is a dedicated fuel tank for example, or a fuel tank also used for propelling the marine platform
The reforming unit 7 for example is suitable to carrying out steam reforming and produces the syngas 9 comprising dihydrogen a first high volume concentration, carbon 20 dioxide, carbon monoxide, methane and water vapour.
Advantageously the reforming unit 7 is also suitable for conducting a SHIFT reaction (or « water-gas shift reaction ») to obtain the syngas 9.
The SHIFT reaction is the reaction CO + H2O → CO2 + H2.
The filtration unit 11 advantageously comprises one or more metal membranes, for
25 example in the form of plates or tubes. The filtration unit 11 is adapted for removing some
compounds from the syngas 9 to obtain the filtered gas 13 and residue(s) 15 which are sent to the storage tank(s) 17 or are discharged outside the marine platform 1.
The filtration 11 unit comprises seals or welds to obtain gas tightness between the
syngas 9 and the filtered gas 11 i.e. between upstream and downstream of the filtration unit
30 11. These sealing elements can lose their efficacy throughout the lifetime of the system,
which can translate as an increase in the quantity of residual carbon monoxide in the composition of the filtered gas 11. It is therefore advantageous to have a methanation unit 19 to reduce the impact of these transfers.

4
The filtered gas 13 comprises dihydrogen at a second volume concentration greater than the first concentration, carbon monoxide at a third volume concentration, and carbon dioxide at a fourth volume concentration.
The second concentration is advantageously greater than 90 vol %, preferably
5 greater than 95 vol %, and more preferably greater than 97 vol %.
The third concentration is advantageously less than 500 ppm, preferably less than 300 ppm, and more preferably less than 150 ppm.
Advantageously, the fourth concentration is between 50 and 200 times the third
concentration. In other words, there is between 50 and 200 times more carbon dioxide in
10 moles than carbon monoxide in the filtered gas 13.
In the filtered gas 13, the other components are chiefly methane and water vapour. Advantageously, the filtered gas is composed of at least 99.9 volume % of dihydrogen, carbon monoxide, carbon dioxide, water vapour and methane.
The filtered gas 13 is received for example in the methanation unit at a temperature
15 of between 200 °C and 350 °C, preferably lower than 300 °C, and more preferably lower
than 250 °C.
The methanation 19 unit is configured to synthesize methane from the dihydrogen
and carbon monoxide contained in the filtered gas 13. The methanation unit is selective in
that methanation, in moles, takes place more on the carbon monoxide than on the carbon
20 dioxide present in the filtered gas. The methanation unit 19 advantageously comprises a
catalyst comprising nickel and/or ruthenium for example.
Advantageously, at least 97 % of the carbon dioxide contained in the filtered gas 13 does not react in the methanation unit 19 and is found in the treated gas 21.
The treated gas 21 comprises carbon monoxide at a fifth volume concentration of
25 less than 1 ppm.
The fuel cell 23 for example is of proton-exchange membrane type (PEM).
The oxidizer 29 is dioxygen or air for example.
The operation of the marine platform 1 can be inferred from its structure and will now
be briefly described.
30 The fuel 5 arrives in the reforming unit 7 from the tank 3. The reforming unit 7
produces syngas 9 from the fuel 5, dioxygen 5B and steam 6B.
The syngas 9 is then filtered by the filtration unit 11 which produces the filtered gas
13 enriched with dihydrogen and depleted of carbon monoxide and optionally of carbon
dioxide. This also produces the residue(s) 15 which are stored in the tank(s) 17 or
35 discharged outside the marine platform 1.

5
The filtered gas 13 is then methanized by the methanation unit 19 which produces
the treated gas 21. In the methanation unit 19, a large fraction of the carbon monoxide
contained in the filtered gas 13 reacts with the dihydrogen to form methane. On the other
hand, by means of the selectivity of methanation, very little of the carbon dioxide contained
5 in the filtered gas 13 reacts with the dihydrogen, which limits the consumption of dihydrogen.
Overall, methanation allows the concentration of carbon monoxide in the treated gas 21 to be reduced to a value of less than 1 ppm, without consuming too great a quantity of dihydrogen which is then converted to electricity by the fuel cell 23.
The fuel cell 23 uses the oxidizer from the source 27 and produces the waste 33
10 stored in the tank 31. The waste 33 here is water and is advantageously used to produce
the steam 6B.
By means of the above-described characteristics, and of the methanation unit 19 in
particular, the fuel cell 23 receives a very low concentration of carbon monoxide and
maintains its performance (electricity yield) for longer time.
15 In addition, when the fuel cell 23 is purged, there is a reduced risk of polluting the
atmosphere on board with compounds such as carbon monoxide or carbon dioxide.
The marine platform 1 therefore has improved safety.

WE CLAIMS

A marine platform (1), preferably an underwater machine, comprising:
- a reforming unit (7) suitable for producing a syngas (9) from at least one fuel (5),
5 the syngas (9) comprising dihydrogen at a first volume concentration, carbon dioxide and
carbon monoxide,
- a filtration unit (11) suitable for filtering the syngas (9) and producing a filtered gas
(13) comprising dihydrogen at a second volume concentration that is greater than the first
concentration, carbon monoxide at a third volume concentration and carbon dioxide at a
10 fourth volume concentration, and
- at least one fuel cell (23),
characterized in that it also comprises a methanation unit (19) configured to receive
the filtered gas (13) and to transform it into a treated gas (21), the methanation unit (19)
being configured to synthesize methane from the dihydrogen and carbon monoxide that are
15 present in the filtered gas (13), the treated gas (21) comprising carbon monoxide at a fifth
volume concentration of less than 1 ppm, the fuel cell (23) being configured to receive the treated gas and produce electricity.
2. The marine platform (1) according to claim 1, wherein the methanation unit (19)
20 is configured to allow the passing into the treated gas of at least 97 % of the carbon dioxide
contained in the filtered gas.
3. The marine platform (1) according to claim 1 or 2, wherein the methanation unit
comprises a catalyst comprising nickel and/or ruthenium.
25
4. The marine platform (1) according to any of claims 1 to 3, wherein the third
concentration is less than 500 ppm, preferably less than 300 ppm, and more preferably less
than 150 ppm.
30 5. The marine platform (1) according to any of claims 1 to 4, wherein the second
concentration is greater than 90 %, preferably greater than 95 %, and more preferably greater than 97 %.
6. The marine platform (1) according to any of claims 1 to 5, wherein the fourth
35 concentration is comprised between 50 and 200 times the third concentration.

7
7. The marine platform (1) according to any of claims 1 to 6, wherein the filtered
gas (13) is received in the methanation unit at a temperature comprised between 200 °C
and 350 °C, preferably lower than 300 °C, and more preferably lower than 250 °C.
5
8. The marine platform (1) according to any of claims 1 to 7, wherein the filtration
unit (11) comprises a metal membrane.
9. The marine platform (1) according to any of claims 1 to 8, wherein the filtered
10 gas (13) is composed of at least 99.9 volume % of dihydrogen, carbon monoxide, carbon
dioxide, water vapour and methane.
10. A method comprising the following steps:
- obtaining a marine platform (1) according to any of claims 1 to 9;
15 - in the reforming unit (7), producing the syngas from at least the fuel (5);
- filtering the syngas (9) and producing the filtered gas (13) in the filtration unit (11);
- in the methanation unit (19), receiving the filtered gas (13) and transforming the filtered gas (13) into the treated gas (21), and
- in the fuel cell (23), receiving the treated gas (21) and producing electricity.