Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
2002-02-08
2004-11-30
Tsang-Foster, Susy (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S010000, C429S006000, C423S648100, C423S651000, C423S215500
Reexamination Certificate
active
06824902
ABSTRACT:
The invention relates to a process and a device for the production of electricity from hydrocarbons and that uses a fuel cell.
The applications may relate to stationary systems or on-board systems for the production of electricity or co-generation of electricity/heat.
The technological background is illustrated by Patent U.S. Pat. No. 5,897,970 and Patent Applications WO 99/46032, WO 00/78443 and JP 06 111844 (Patent Abstracts of Japan, Vol. 018, No. 382 (E-1580), Jul. 19, 1994).
Systems for the production of electricity from hydrocarbon feedstocks that comprise a fuel cell and a “fuel processor” making it possible to transform fuel (the hydrocarbon feedstock) into a gas mixture H2/CO/CO2/H2O) or synthesis gas, making it possible, optionally after treatment, to feed a fuel cell, are already known.
Different types of fuel processors are known, in particular systems that use vaporeforming of hydrocarbons for their transformation of rich gas into H2/CO/CO2/H2O. The partial oxidation of POX (for “partial oxidation”) is also known. This technique uses a burner that operates with an amount of oxidant (air or oxygen) that is less than the combustion stoichiometry. Water is often added to the oxidant and/or to the hydrocarbon feedstock to improve the hydrogen production and to reduce or to eliminate the soot formation. This soot production is the main problem of partial oxidation, in particular with the liquid hydrocarbon feedstocks that often contain aromatic and olefinic compounds that are soot precursors.
The autothermal process (or ATR) that comprises a partial oxidation and a catalytic reforming of the hot gaseous effluents of the partial oxidation are also known.
There, too, soot formation is a very significant problem, whereby the soot deactivates the catalyst if it exists in too large an amount.
The elimination of soot contained in a synthesis gas that is obtained from a partial oxidation unit is a known industrial problem: the operation is performed by washing the gas and recovering soot by water.
It was also already proposed to use a soot filter for industrial units. For example, U.S. patent application Ser. No. US 1999-271741 indicates the problem of eliminating soot corresponding to “1 to 3%” of the carbon of the feedstock in the form of “unreacted soot,” by alternate combustion in two candle filters. The feedstocks that are mentioned are carbon, black liquor and hydrocarbon fuels.
The candle filters are bulky devices that are more suitable for industrial units than for providing small amounts of hydrogen-rich gas, for example for feeding fuel cells.
Furthermore, very compact soot filters that are used for the filtration of effluents of diesel engines are known.
These filters are clearly incompatible with amounts of soot such as those mentioned above.
SUMMARY OF THE INVENTION
The first object of the invention is a process and a device that make it possible to produce electricity in a fuel cell that is fed by a gas that was obtained by partial oxidation and that has no soot problem.
The second object of the invention is a process and a simplified and economical device for eliminating soot.
For this purpose, the invention describes a process for the production of electricity in a fuel cell from hydrocarbons that comprise a partial oxygenation stage of hydrocarbons, characterized in that
a) A stream
2
that contains a hydrocarbon feedstock with boiling points that are less than about 400° C. is fed
b) The stream is preheated to a temperature of at least 200° C., enough so that said stream is entirely evaporated,
c) An air-carrying gaseous oxidant stream
1
is fed, and the oxidant stream is preheated to a temperature of at least 400° C.
d) The two gaseous streams are reacted in a partial oxidation zone
3
or chamber, whereby the operating conditions of this chamber are in the following range:
Dwell time in the chamber of between 100 and 1200 milliseconds
Output temperature of the chamber of between 1150 and 1650° C.
Pressure of the chamber of between 0.1 and 1.5 MPa, and preferably 0.15 MPa to 0.8 MPa whereby the output temperature of the chamber is adequate so that at least 90% of the carbon of the feedstock is converted into CO or CO2 and that the amount of soot contained in the effluent is less than 0.1% by weight relative to the feedstock, preferably between 0.5 ppm and 100 ppm (1 ppm=1 part per million)
e) The effluent of the chamber is cooled to a temperature of between 200° C. and 1050° C. and preferably between 500° C. and 900° C.
f) The cooled effluent is circulated in at least one zone for recovery and treatment of soot that comprises a first circuit
6
comprising at least a first filter
7
and a second circuit
41
that are mounted in parallel; a stage for filtration of the effluent in the first filter is carried out for a period of time in order to deposit soot there; the first filter containing the soot is regenerated in the presence of a gas that contains oxygen for another period of time, and during said other period of time, the cooled effluent is circulated in the second circuit, whereby said first filter has a high density such that the filtration surface area/useful volume ratio is between 80 and 5000 m
−1
and a hydrogen-rich effluent that is exiting the recovery zone is recovered
g) A fuel cell
10
is fed by at least a portion of the effluent that is exiting the recovery zone.
The oxidation chamber that is equipped with at least one burner can be a stirred chamber or a piston-flow chamber or a mixed-flow chamber.
The particle filters are generally compact. In general, filters made of ceramic whose filtration surface area/filter volume ratio is the highest possible will preferably be selected, knowing that the back pressure generated by the filter under these conditions is lower.
It is possible to obtain excellent filtration results with a filtration surface area/filter volume ratio of in general between 80 m
−1
and 5000 m
−1
and preferably between 150 and 1500 m
−1
, thereby reducing the regeneration frequency. The filters that are generally recommended can be those that are used to retain the particles of diesel engines in the automobile industry that have an efficiency that is higher than 70%, preferably higher than 90% and more particularly between 93 and 98%, as is the case for multitube filters with a honeycomb structure. It is advantageously possible to use monoliths that are made of ceramic, cordierite or silicon carbide with greater than 90% efficiency or filters with ceramic fibers that are wound around cylinders that are pierced with holes, with an efficiency that is higher than 75% but with lower back pressure.
It is also possible to use filters with ceramic- or glass-woven fibers or with sintered metals that are compatible with the temperature of the effluents that circulate in the filter, higher than the soot combustion temperature.
According to a characteristic of the invention, the second circuit of the recovery zone can contain at least one filter. It can contain a catalyst for vapor reforming recovered soot to gasify it while the first filter is in a regeneration period.
According to a variant, it is possible to regenerate the filter of the second circuit in the presence of a gas that contains oxygen for at least a portion of the period of time of the filtration stage in the first filter.
The effluents that are obtained from the regeneration of the first filter by soot combustion can be mixed with the effluent that circulates in the second circuit and introduced into the fuel cell. According to a variant, these regeneration effluents can be withdrawn from the first filter.
According to another characteristic of the invention, the gaseous oxidant stream and/or the hydrocarbon feedstock can contain the water vapor in an H
2
O/hydrocarbon mass ratio of between 0.1 and 2.0, preferably between 0.4 and 1.2.
The fuel cells can be an electrolyte-type cell with solid oxide (SOFC) with little sensitivity to impurities, a polymer electrolyte cell (PEMFC type) or a phosphoric acid cell, whereby the latter two ce
Boucot Pierre
Lenglet Eric
Martin Gérard Henri
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Tsang-Foster Susy
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