JP2014519177A - Hybrid system of fuel cell and reciprocating gasoline / diesel engine - Google Patents

Abstract

The hybrid fuel cell plant includes a fuel cell, a fuel fuel, and a fuel reformer that mix hydrocarbon fuel and steam with each other upstream of the fuel cell. The reformer converts hydrocarbon fuel and steam partially or fully into a reformed fuel stream containing hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ). The fuel cell receives the reformed fuel stream at or above atmospheric operating pressure, and further receives an air stream containing oxygen (O ₂ ) and nitrogen (N ₂ ) at or above atmospheric operating pressure. Under pressure, it produces a hot exhaust stream containing lean air, non-oxidized CO, and residual H ₂ . O ₂ mole fraction of lean air is lower than O ₂ mole fraction of the fuel cell inlet air. When the reformed fuel and air stream is received at a pressure above atmospheric pressure, a hot exhaust stream is generated at a pressure above atmospheric pressure. An internal combustion or external combustion engine generates power directly or indirectly in response to a pressurized fuel cell hot exhaust stream to increase the efficiency of the fuel cell power plant.
[Selection] Figure 1

Description

  The present invention relates generally to fuel cell power plants, and more specifically, incorporates a Rankine cycle, such as an organic Rankine cycle (ORC), uses an internal combustion or external combustion engine downstream of the anode of the fuel cell, The present invention relates to a fuel cell power plant driven by unconverted fuel that exits the fuel cell to achieve a higher overall plant efficiency than can be achieved with the fuel cell power plant.

  A fuel cell is an electrochemical energy conversion device that has demonstrated the potential for relatively high efficiency and low pollution in power generation. Fuel cells generally provide a direct current (DC) that can be converted to an alternating current (AC), for example, via an inverter. The DC or AC voltage can be used to power motors, lights, and many appliances and systems. The fuel cell may be operated in fixed, semi-fixed, or portable applications. Certain fuel cells, such as solid oxide fuel cells (SOFC), may be operated on large scale power generation systems that provide electricity to meet industrial and municipal needs. Another fuel cell may be useful for smaller portable applications such as powering an automobile, for example.

  Fuel cells generate electricity by electrochemically combining fuel and oxidant across an ion conductive layer. This ion conductive layer, also called fuel cell electrolyte, may be liquid or solid. Common types of fuel cells include phosphoric acid (PAFC), dissolved carbonate (MCFC), proton exchange membrane (PEMFC), and solid oxide (SOFC), generally all named after these electrolytes. It is named. In practice, fuel cells are integrated electrically in series within a fuel cell assembly for generating power at an effective voltage or current. Thus, an interconnect structure may be used to connect or couple adjacent fuel cells in series or in parallel.

  In general, fuel cell components include an electrolyte and two electrodes. The reaction that generates electricity is generally performed at an electrode where a catalyst is placed to promote the reaction. In order to increase the surface area for chemical reaction, the electrode is configured as a groove, a perforated layer or the like. The electrolyte propagates charged material from one electrode to the other, and the others are substantially impermeable to both fuel and oxidant.

  In general, a fuel cell generates electricity by converting hydrogen (fuel) and oxygen (oxidant) into water. When air is used as the oxidant, nitrogen in the air is substantially inert and normally passes through the fuel cell. Hydrogen fuel may be provided by local reforming (eg, on-site steam reforming) of carbon-based feedstocks, such as reforming more readily available natural gas and other hydrocarbon fuels and feedstocks. Examples of hydrocarbon fuels include natural gas, methane, ethane, propane, methanol, synthesis gas, and other hydrocarbons. Hydrocarbon fuel reforming to produce hydrogen that enhances the electrochemical reaction may be incorporated into the operation of the fuel cell. Further, such reforming may be performed inside and / or outside the fuel cell. If hydrocarbon reforming is performed outside the fuel cell, the associated external reformer may be located remotely from or in close proximity to the fuel cell.

A fuel cell system that can reform hydrocarbons inside and / or outside of the fuel cell can provide advantages such as simplified design and operation. For example, hydrocarbon steam reforming reactions are usually endothermic reactions, so internal reforming within a fuel cell, or external reforming in an adjacent reformer, is usually due to an endothermic electrochemical reaction of the fuel cell. The generated heat can be used. Furthermore, a catalyst that is active in the electrochemical reaction of hydrogen and oxygen in the fuel cell to generate electricity can also promote internal reforming of the hydrocarbon fuel. For example, in SOFC, when a nickel catalyst is placed on an electrode (for example, the anode) to sustain an electrochemical reaction, the active nickel catalyst also reforms the hydrocarbon fuel into hydrogen (H ₂ ) and carbon monoxide (CO). it can. Furthermore, reforming the hydrocarbon feed can produce both hydrogen and CO. Therefore, fuel cells such as SOFC that can utilize CO as a fuel (in addition to hydrogen) generally utilize reformed hydrocarbons and for internal and / or external reforming of hydrocarbon fuels. Is a more attractive candidate.

  The ability of a fuel cell to convert hydrocarbon fuel to electrical energy is limited by the loss mechanism in the battery that generates heat and by the partial use of the fuel. The reforming of the primary fuel of the hydrocarbon in the conventional combined cycle fuel system is performed upstream of the fuel cell. The exhaust gas from the combustion cell containing non-oxidized fuel and combustion products is then sent to an exhaust gas burner, from which heat can be taken into the combined cycle system and possibly into the fuel reformer. Today's fuel cell examples typically achieve about 50% conversion efficiency.

US Patent Application Publication No. 2008/187789

  In light of the above, there is a need to provide technology that further increases the efficiency of a fuel cell plant by increasing the efficiency of the fuel cell.

An exemplary embodiment of the present invention is a hybrid fuel cell plant comprising:
A fuel cell;
Hydrocarbon fuel and steam were mixed with each other upstream of the fuel cell, and the hydrocarbon fuel and steam were characterized including hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ). A fuel reformer configured to partially or fully convert to a fuel stream, wherein the fuel cell receives the reformed fuel stream at atmospheric operating pressure or above and further oxygen ( An air stream containing O ₂ ) and nitrogen (N ₂ ) is received at or above atmospheric working pressure, and the fuel cell reacts to the reformed fuel stream and air stream to produce lean air, non-oxidized Producing a high temperature exhaust stream comprising CO and residual H ₂ ;
O ₂ mole fraction of lean air with low fuel reformer than O ₂ mole fraction of the fuel cell inlet air,
An internal or external combustion engine configured to generate electricity in response to a hot exhaust stream generated by a fuel cell;
The hybrid fuel cell plant includes a high temperature exhaust stream generated by the fuel cell and a Rankine cycle driven by heat recovered from at least one of the high temperature exhaust gas generated by the combustion engine.

According to another embodiment, a method for generating power by a hybrid fuel cell plant comprises:
Reforming the hydrocarbonaceous fuel with a vapor stream upstream of the fuel cell plant by an external reformer to produce a substantially pure hydrogen fuel stream therefrom at atmospheric operating pressure or above; ,
Generating an air flow at or above atmospheric working pressure;
In response to the reformed fuel and air stream, including carbon monoxide and residual hydrogen such that the O ₂ mole fraction of the lean air stream is lower than the O ₂ mole fraction of the fuel cell inlet air; A step of generating a high temperature exhaust stream including a lean air stream by the fuel cell, wherein the reformed fuel and air stream flows into the fuel cell at a pressure above atmospheric pressure; Is generated, and
Driving the combustion engine in response to the high temperature exhaust flow of the fuel cell to generate electricity;
Providing a fuel cell plant having an efficiency of 60% or more by generating electric power by Rankine cycle in response to exhaust heat recovered from both the high temperature exhaust flow and the high temperature exhaust of the fuel cell generated by the combustion engine; , Including.

  The above and other features, aspects, and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which like characters represent like parts throughout the drawings.

When the lean air produced by the fuel cell is deficient, additional air is fed to the combustion engine, producing a hot exhaust stream containing the lean air used to feed the downstream combustion engine FIG. 1 is a schematic diagram illustrating a hybrid fuel cell plant according to an embodiment that uses a fuel cell that operates with pressurized reformed fuel. A fuel cell operating with pressurized reformed fuel is used to generate a hot exhaust stream that is used to supply a downstream combustion engine, and a fuel cell for generating additional power 1 is a schematic diagram illustrating a hybrid fuel cell plant that also uses an organic Rankine cycle (ORC) driven by exhaust gas generated by both combustion and / or combustion engines.

  Although the above drawings show alternative embodiments, as discussed in the description, other embodiments of the invention are also contemplated. In any case, this disclosure presents exemplary embodiments of the present invention for purposes of illustration and not limitation. Many other modifications and embodiments within the scope and spirit of the principles of the present invention can be devised by those skilled in the art.

  The embodiments described herein with reference to the drawings advantageously provide a fuel cell plant efficiency of 60% or greater, which is also 70% or greater in certain embodiments using the combustion engine principles described herein. Even high efficiency. Any size combustion engine can be used downstream of the fuel cell, including a gasoline engine with a minimum output power of 100 kW, thus simplifying the combined embodiment of the fuel cell and combustion engine described herein. Can be advantageously deployed to provide distributed energy.

  As discussed, other embodiments of the invention are also contemplated. The principles described herein can be varied by using the principles described herein, which can be readily applied to comparable fuel cell technologies that are not strictly solid oxygen fuel cells or dissolved carbonate fuel cells, for example. A simple exhaust heat recovery cycle and methods incorporating these cycles are also possible.

  FIG. 1 operates with pressurized reformed fuel 17 to produce a hot exhaust stream 14 that is ultimately supplied to a combustion engine 16 according to one embodiment, such as, but not limited to, solid oxygen fuel. 1 is a schematic diagram showing a hybrid fuel cell plant 10 using a fuel cell 12 that may be a battery (SOFC) or a dissolved carbonate fuel cell (MCFC). According to certain embodiments, the hot exhaust stream 14 may be used to be fed directly to the combustion engine 16 or first cooled to remove excess water before being fed to the combustion engine 16. Also good. The combustion engine 16 may be, but is not limited to, a 4-cylinder reciprocating engine, a 2-cylinder reciprocating engine, a 2-cylinder opposed piston engine, or a gas turbine.

Pressurized hydrocarbon fuel 11 such as CH ₄ contains pressurized hydrocarbon fuel and steam, hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ) upstream of the fuel cell 12. The pressure is mixed with the pressure 13 in a reformer 18 which functions to convert partially or completely into a pressurized reformed fuel stream. The fuel cell 12 receives a pressurized reformed fuel stream 17 containing H ₂ , CO, and CO ₂ and further receives a pressurized air stream 15 containing oxygen (O ₂ ) and nitrogen (N ₂ ), While generating electricity, in response to the pressurized fuel stream 17 and the pressurized air stream 15, a hot exhaust stream 14 containing lean air, non-oxidized CO, and residual H ₂ is generated.

  The hot exhaust stream 14 typically contains a significant amount of water as the vapor phase. Therefore, it is generally more desirable to remove excess water before supplying the hot exhaust stream 14 to the combustion engine 16. A condenser or flash condenser 22 is used, and some or all of such water flowing into the condenser 22 at a pressure above atmospheric pressure is cooled and removed. A Rankine cycle as described herein may be used to recover the exhaust heat of the fuel cell 12 and the combustion engine 16.

The hybrid fuel cell plant 10 further includes a compressor 20 that functions to compress the exhaust gas stream condensed before entering the combustion engine 16 disposed downstream of the fuel cell 12. In general, the anode of a fuel cell (SOFC) 12 can utilize about 80% of the pressurized reformed fuel 17 that may include a carbon monoxide reaction. Unconverted H ₂ and CO fuel flows from the anode of the fuel cell 12 and joins the pressurized exhaust stream 14. By adding an internal combustion or external combustion engine 16 downstream of the fuel cell 12 as shown in FIG. 1, the unconverted portion of the reformed fuel 17 is eventually consumed, generating additional power, and a fuel cell plant Ten creative conversion efficiencies can be significantly increased.

Additional fuel 19 may be added to the fuel cell anode exhaust stream 14 to enrich the combustion stream entering the combustion engine 16 and optimize engine performance. Air for downstream combustion may be drawn from the atmosphere or, optionally, from the exhaust of the fuel cell cathode. Fuel cell cathodes provide a flow of less O ₂ than atmosphere, and therefore, when used instead of air drawn from the atmosphere for downstream combustion, NOx emissions are reduced.

  The pressure at which combustion is performed in both the anode and the downstream engine 16 may be atmospheric pressure, or may be pressure higher than atmospheric pressure. When the pressure is above atmospheric pressure, a higher pressure is maintained throughout the anode and cathode of the fuel cell. According to one embodiment, the atmosphere is compressed by a turbocharger or compressor-turbine system 40 that is driven by exhaust flow from the combustion engine 16 as shown in FIG. This pressurized air can be used to generate power to preheat fuel and air and / or drive the compressor, but is not limited thereto. Oxygen ions move from the pressurized air stream, which is also mixed with the fuel in the anode that has increased in pressure, and ultimately produces a pressurized anode exhaust stream 14 that is fed downstream to the combustion engine 16 and is electrically Is generated. According to one embodiment, the condenser 22 removes excess water from the exhaust stream 14 as described. A compressor 20 located downstream of the condenser 22 further increases the operating pressure of the exhaust stream before it is used by the combustion engine 16.

According to one embodiment shown in FIG. 2, the Rankine cycle 32, such as, but not limited to, a DReSCO-type CO ₂ Rankine cycle, includes an anode exhaust stream 14 and a final exhaust stream exiting the downstream combustion engine 16. Heat is recovered simultaneously. FIG. 2 uses a fuel cell 12 operating with pressurized reformed fuel 17 to produce a hot exhaust stream 14 that is ultimately supplied to a combustion engine 16 and to generate additional power. 1 is a schematic diagram illustrating a hybrid fuel cell plant 30 according to one embodiment using an organic Rankine cycle (ORC) 32 driven by waste gas produced by both the fuel cell 12 and / or the combustion engine 16. The Rankine cycle 32 may further use a condenser to remove water from the fuel cell exhaust before being used by the combustion engine 16.

  The above described embodiment described with reference to FIGS. 1 and 1 operates to increase the efficiency of the fuel cell plant above the current practical limit of 50% by increasing the efficiency of fuel use. Simulation results show that the overall efficiency of some embodiments of the hybrid system can be increased to 65%, including the heat consumed by the reformer 18, even if the effects due to the Rankine cycle are excluded. It has been shown. The overall system efficiency can theoretically be over 70%.

  These embodiments further increase the efficiency of the fuel cell plant beyond that achievable using conventional gas turbines, thus creating a basis for selecting a fuel cell system over the prior art. Since any size combustion engine may be used downstream of the fuel cell 12, including a 100 kW minimum gasoline engine, the combined fuel cell and combustion engine 10,30 system is as described herein. Can be easily deployed for distributed energy generation. Conventional fuel cell power plants simultaneously use lean air generated by the fuel cell cathode to reduce the possibility of using a high pressure fuel cell incorporating a combustion engine and Rankine cycle and to reduce NOx emissions of the combustion engine. Did not recognize that it was generated and used.

In summary, the hybrid fuel cell plant 10, 30 has been described herein. In each of these embodiments, the reformed fuel 11 and the pressurized steam 13 pressurized on the upstream side of the fuel cell 12 are mixed with each other at an increased pressure, and the hydrocarbon fuel 11 and the steam 13 are mixed with hydrogen. A fuel cell 12 and a fuel reformer configured to partially or fully convert into a reformed fuel stream 17 comprising (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ). And a quality device 18. The fuel cell 12 is configured to receive a reformed fuel stream 17 that includes H ₂ , CO, and CO ₂ , and a pressurized air stream 15 that further includes oxygen (O ₂ ) and nitrogen (N ₂ ). In response to the pressurized reformed fuel stream 17 and the pressurized air stream 15 to produce a hot exhaust stream 14 containing lean air, non-oxidized CO, and residual H _2. It is configured. An internal combustion or external combustion engine 16, which may be a reciprocating gasoline engine, generates power directly in response to a hot exhaust stream 14 or after removal of water from the exhaust stream 14 and / or compression of the exhaust stream 14.

  While certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. Accordingly, the appended claims are intended to cover all such modifications and changes as fall within the true spirit of this invention.

Claims (25)

A hybrid fuel cell plant,
A fuel cell;
Hydrocarbon fuel and steam are mixed with each other upstream of the fuel cell, and the hydrocarbon fuel and steam contain hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ). A fuel reformer configured to partially or fully convert into a traited fuel stream, wherein the fuel cell is configured to pressure the reformed fuel stream at atmospheric operating pressure or higher. And receiving an air stream containing oxygen (O ₂ ) and nitrogen (N ₂ ) at an atmospheric operating pressure or higher, and the fuel cell includes the reformed fuel stream and air stream To produce a high-temperature exhaust stream containing lean air, non-oxidized CO, and residual H ₂ , wherein the O ₂ mole fraction of the lean air is lower than the O ₂ mole fraction of the fuel cell inflow air. The genitalia,
An internal combustion or external combustion engine configured to generate electricity in response to a hot exhaust stream generated by the fuel cell;
A hybrid fuel cell plant comprising: a Rankine cycle driven by heat recovered from both the hot exhaust stream generated by the fuel cell and the hot exhaust gas generated by the combustion engine.   The hybrid fuel cell plant according to claim 1, wherein the fuel cell is a solid fuel cell.   The hybrid fuel cell plant according to claim 1, wherein the fuel cell is a dissolved carbonate fuel cell.   The hybrid fuel cell plant according to claim 1, wherein the fuel cell comprises both a solid oxygen fuel cell and a dissolved carbonate fuel cell. The hybrid fuel cell plant according to claim 1, wherein the Rankine cycle comprises a DReSCO type CO ₂ Rankine cycle.   The hybrid fuel cell plant according to claim 1, wherein the Rankine cycle is an organic Rankine cycle.   The hybrid fuel cell plant of claim 1, further comprising a turbocharger or a compressor-turbine system driven by hot gas produced by the combustion engine to produce compressed air.   A recuperator configured to extract heat from at least one of a high-temperature exhaust gas flow and a high-temperature exhaust gas generated by the combustion engine to further heat the compressed air flowing into the cathode of the fuel cell 3; The hybrid fuel cell plant according to claim 7 further provided.   The hybrid fuel cell plant of claim 1, further comprising a compressor configured to further compress the pressurized exhaust stream generated by the fuel cell before being used by the combustion engine.   The apparatus further comprises a condenser configured to cool the pressurized exhaust stream generated by the fuel cell prior to use by the combustion engine and to remove water from the pressurized exhaust stream generated by the fuel cell. The hybrid fuel cell plant according to claim 1.   The hybrid fuel cell plant according to claim 1, wherein the combustion engine is a reciprocating gasoline engine.   The hybrid fuel cell plant according to claim 1, wherein the combustion engine is a gas turbine.   The hybrid fuel cell plant of claim 1, wherein the reformer, fuel cell, combustion engine, and Rankine cycle are all configured to provide a fuel cell plant that operates at an efficiency of about 60% or greater.   The hybrid fuel cell plant of claim 1, wherein the reformer, fuel cell, and Rankine cycle are both configured to provide a fuel cell plant that operates with an efficiency of about 65% or greater.   The hybrid fuel cell plant of claim 1, wherein the reformer, fuel cell, and Rankine cycle are both configured to provide a fuel cell plant that operates with an efficiency of about 70% or greater.     The hybrid fuel cell plant of claim 1, wherein the reformer, fuel cell, and Rankine cycle are both configured to provide a fuel cell plant that operates with an efficiency of between about 50% and about 75%. A method of generating electric power by a hybrid fuel cell plant, comprising:
Reforming the hydrocarbonaceous fuel with a vapor stream upstream of the fuel cell plant by an external reformer to produce a substantially pure hydrogen fuel stream therefrom at atmospheric operating pressure or above; ,
Generating an air flow at or above atmospheric working pressure;
In response to the reformed fuel and air stream, carbon monoxide and residual hydrogen are included so that the O ₂ mole fraction of the lean air stream is lower than the O ₂ mole fraction of the fuel cell inlet air. A high temperature exhaust stream including a lean air stream is generated by the fuel cell, and when the reformed fuel and air stream flow into the fuel cell at a pressure higher than atmospheric pressure, A step in which a hot exhaust stream is generated;
Driving a combustion engine in response to the high temperature exhaust flow of the fuel cell to generate electric power;
A fuel having an efficiency of between 50% and about 75%, generating electric power through a Rankine cycle in response to exhaust heat recovered from at least one of the high temperature exhaust flow and high temperature exhaust of the fuel cell generated by the combustion engine Providing a battery plant.   The method of generating electric power with a hybrid fuel cell plant according to claim 17, wherein driving the combustion engine includes driving a reciprocating gasoline engine.   The method of generating electric power with a hybrid fuel cell plant according to claim 17, further comprising the step of compressing air above atmospheric pressure by a turbocharger or compressor-turbine system driven by hot exhaust gas generated by the combustion engine. .   In order to further heat the pressurized air generated by the turbocharger or compressor-turbine system, the recuperator recovers heat from at least one of the high temperature exhaust stream and the high temperature exhaust gas of the fuel cell generated by the combustion engine. The method of generating electric power by a hybrid fuel cell plant according to claim 19, further comprising the step of extracting by:   18. The method of claim 17, further comprising condensing the hot exhaust stream generated by the fuel cell and removing water from the hot exhaust stream generated by the fuel cell before being used by the combustion engine. A method of generating electric power by a hybrid fuel cell plant.   The method of generating electrical power with a hybrid fuel cell plant according to claim 21, further comprising the step of compressing the condensed hot exhaust stream generated by the fuel cell before being used by the combustion engine.   The method of generating electric power with a hybrid fuel cell plant according to claim 17, wherein generating the high temperature exhaust stream comprises generating a high temperature exhaust stream with a solid oxygen fuel cell or dissolved carbonate type fuel.   The step of generating electric power by Rankine cycle in response to waste heat recovered from at least one of the high-temperature exhaust flow and high-temperature exhaust of the fuel cell generated by the combustion engine includes the step of generating electric power by the organic Rankine cycle. A method for generating electric power by a hybrid fuel cell plant according to claim 17. The step of generating electric power by Rankine cycle in response to waste heat recovered from at least one of the high-temperature exhaust flow and high-temperature exhaust of the fuel cell generated by the combustion engine generates electric power by the DReSCO-type CO ₂ Rankine cycle The method of generating electric power by the hybrid fuel cell plant according to claim 17 including the step of: