Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including heat exchanger for reaction chamber or reactants...
Reexamination Certificate
1999-06-18
2001-02-20
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including heat exchanger for reaction chamber or reactants...
C048S06200R, C048S076000, C048S117000, C048S127900, C422S198000, C422S198000, C431S007000, C431S268000
Reexamination Certificate
active
06190623
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydrogen generating apparatus and, more particularly, to a hybrid reforming reactor which is suitable for use as a hydrogen generation system or as an electric power generation system when used in conjunction with a fuel cell.
BACKGROUND OF THE INVENTION
The use of fuel cells to generate electrical power for electricity or to drive a transportation vehicle relies upon the generation of hydrogen. Because hydrogen is difficult to store and distribute, and because hydrogen has a low volumetric energy density compared to fuels such as gasoline, hydrogen for use in fuel cells will have to be produced at a point near the fuel cell, rather than be produced in a centralized refining facility and distributed like gasoline. To be effective, hydrogen generation for fuel cells must be smaller, simpler, and less costly than hydrogen plants for the generation of industrial gasses. Furthermore, hydrogen generators for use with fuel cells will have to be integrated with the operation of the fuel cell and be sufficiently flexible enough to efficiently provide a varying amount of hydrogen as demand for electric power from the fuel cell varies.
Hydrogen is widely produced for chemical and industrial purposes by converting materials such as hydrocarbons and methanol in a reforming process to produce a synthesis gas. Such production usually takes place in large facilities which are rarely turned down in production for even a few days per year. In addition, the operation of the industrial hydrogen production facilities are often integrated with associated facilities to improve the use of energy for the overall complex. Synthesis gas is the name generally given to a gaseous mixture principally comprising carbon monoxide and hydrogen, but also possibly containing carbon dioxide and minor amounts of methane and nitrogen. It is used, or is potentially useful, as feedstock in a variety of large-scale chemical processes, for example: the production of methanol, the production of gasoline boiling range hydrocarbons by the Fischer-Tropsch process and the production of ammonia.
Processes for the production of synthesis gas are well known and generally comprise steam reforming, autothermal reforming, non-catalytic partial oxidation of light hydrocarbons or non-catalytic partial oxidation of any hydrocarbons. Of these methods, steam reforming is generally used to produce synthesis gas for conversion into ammonia or methanol. In such a process, molecules of hydrocarbons are broken down to produce a hydrogen-rich gas stream. A paper titled “Will Developing Countries Spur Fuel Cell Surge?” by Rajinder Singh, which appeared in the March 1999 issue of
Chemical Engineering Progress
, page 59-66, presents a discussion of the developments of the fuel cell and methods for producing hydrogen for use with fuel cells. The article particularly points out that the partial oxidation process is a fast process permitting small reactors, fast startup, and rapid response to changes in the load, while steam reforming is a slow process requiring a large reactor and long response times, but operates at a high thermal efficiency. The article highlights one hybrid process which combines partial oxidation and steam reforming in a single reaction zone as disclosed in U.S. Pat. No. 4,522,894.
Modifications of the simple steam reforming processes have been proposed to improve the operation of the steam reforming process. In particular, there have been suggestions for improving the energy efficiency of such processes in which the heat available from the products of a secondary reforming step is utilized for other purposes within the synthesis gas production process. For example, processes are described in U.S. Pat. No. 4,479,925 in which heat from the products of a secondary reformer is used to provide heat to a primary reformer.
The reforming reaction is expressed by the following formula:
CH
4
+2H
2
O→4 H
2
+CO
2
where the reaction in the reformer and the reaction in the shift converter are respectively expressed by the following simplified formulae (1) and (2):
CH
4
+H
2
O→CO+3 H
2
(1)
CO+H
2
O→H
2
+CO
2
(2)
In the water gas shift converter which typically follows a reforming step, formula (2) is representative of the major reaction.
U.S. Pat. No. 4,925,456 discloses a process and an apparatus for the production of synthesis gas which employs a plurality of double pipe heat exchangers for primary reforming in a combined primary and secondary reforming process. The primary reforming zone comprises at least one double-pipe heat exchanger-reactor and the primary reforming catalyst is positioned either in the central core or in the annulus thereof. The invention is further characterized in that the secondary reformer effluent is passed through which ever of the central core or the annulus is not containing the primary reforming catalyst countercurrently to the hydrocarbon-containing gas stream.
U.S. Pat. No. 5,181,937 discloses a system for steam reforming of hydrocarbons into a hydrogen rich gas which comprises a convective reformer device. The convective reformer device comprises an outer shell enclosure for conveying a heating fluid uniformly to and from a core assembly within the outer shell. The core assembly consists of a multiplicity of tubular conduits containing a solid catalyst for contacting a feed mixture open to the path of the feed mixture flow such that the path of the feed mixture flow is separated from the heating fluid flow in the outer shell. In the process, an autothermal reformer fully reforms the partially reformed (primary reformer) effluent from the core assembly and supplies heat to the core assembly by passing the fully reformed effluent through the outer shell of the convective reforming device.
U.S. Pat. No. 5,595,833 discloses a process and apparatus for operating a solid oxide fuel cell stack and includes an adiabatic pre-reformer to convert about 5 to 20% of the hydrocarbon fuel into methane, hydrogen, and oxides of carbon At startup the pre-reformer is used to perform partial oxidation with methanol to heat the solid oxide fuel stack to a temperature of about 1000° C. When the temperature of the region of the pre-reformer reaches about 500° C. the methanol flow is terminated.
WO 97/45887 discloses a hydrodesulfurizer assembly which is thermally coupled with process gas heat exchangers and a shift converter. The hydrodesulfurizer assembly is employed to cool the reformer effluent prior to passing the cooled reformer effluent to the shift converter zone.
WO 98/13294 discloses a process for removing carbon monoxide from a gas stream by subjecting the gas stream to a first stage high temperature selective catalytic methanation to lower the carbon monoxide concentration, followed by a second stage low temperature selective catalytic methanation to further lower the residual carbon monoxide concentration in the gas stream to a carbon monoxide concentration below 40 ppm.
U.S. Pat. No. 4,943,493 discloses a fuel cell power plant which integrates the operation of a reformer to convert a hydrocarbon fuel into a hydrogen-rich fuel which is passed to the anode side of a fuel cell. A portion of the anode exhaust stream is withdrawn from the fuel cell and passed to a burner zone wherein the anode exhaust gas stream is mixed with an oxidant stream and combusted to provide heat to the reformer. U.S. Pat. No. 4,943,493 discloses the problem of monitoring and controlling the flame temperature in the burner zone and claims an indirect approach to maintaining the flame temperature with a range which results in complete combustion of the fuel and avoids a very high flame temperature which may exceed the temperature resistance of the burner liner materials. The reference discloses the control of the composition of the burner gas by bypassing a portion of the anode waste gas to maintain an adiabatic flame temperature between about 1150° C. (2100
20
F.) and about 1480° C. (2700° F.) whereby the he
Doshi Kishore J.
Sanger Robert J.
Senetar John J.
Towler Gavin P.
Vanden Bussche Kurt M.
Ridley Basia
Silverman Richard P.
Tomei John G.
Tran Hien
UOP LLC
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