System and method for early detection of contaminants in a fuel processing system

System and method for early detection of pollutants in fuel processing system

<p>10. . . Fuel treatment system</p><p>12. . . Fuel processor</p><p>14. . . Fuel cell assembly</p><p>16. . . Feed assembly</p><p>18. . . raw material</p><p>20. . . Water logistics</p><p>twenty four. . . Hydrogen generation area</p><p>26. . . Initial hydrogen stream</p><p>30. . . Separation area</p><p>32. . . Hydrogen screening membrane</p><p>34. . . Product hydrogen stream</p><p>36. . . By-product logistics</p><p>38. . . Refined area</p><p>40. . . Methanation catalyst bed</p><p>42. . . Refined product logistics</p><p>44. . . Reorganization area</p><p>50. . . Control System</p><p>52. . . Sensor assembly</p><p>54. . . Controller</p><p>56. . . Memory part</p><p>58. . . Isolation valve</p><p>60. . . Exhaust gas logistics</p><p>80. . . User interface</p><p>82. . . Display area</p><p>84. . . User signaling device</p><p>86. . . User input device</p>

Fig. 1 is a schematic diagram of a fuel processing system according to the present invention.

Fig. 2 is Fig. 1 showing another embodiment of the fuel processing system according to the present invention.

Fig. 3 is a flowchart illustrating the method for early detection of pollutants according to the present invention.

Fig. 4 is a schematic front view of a user interface for the fuel treatment system according to the present invention.

Invention field

The present invention generally relates to a fuel processing system, and more particularly to a system and method for early detection of impending failure of a hydrogen purifier in the fuel processing system.

Background and overview of the invention

The fuel processing system includes a fuel processor or hydrogen generation assembly, which generates hydrogen; and a fuel cell assembly, which generates electricity and water from hydrogen and air. Because the fuel cell is extremely sensitive to certain pollutants, care must be taken to prevent the hydrogen fed to the fuel cell assembly from containing more than acceptable pollutants. Therefore, before the contaminated product stream reaches the fuel cell assembly, it is necessary to detect the contaminants in the product hydrogen stream from the fuel processor.

The present invention provides a system and method for detecting impurities in the hydrogen product stream of a fuel processing system, which has sufficient time to prevent the impurities from reaching the fuel cell assembly associated with the fuel processor.

When referring to the following detailed description and the accompanying drawings, those skilled in the art can understand many other features of the present invention. Among them, the preferred embodiments incorporating the principles of the present invention are disclosed as purely exemplary examples.

Schematic description

Fig. 1 is a schematic diagram of a fuel processing system according to the present invention.

Fig. 2 is Fig. 1 showing another embodiment of the fuel processing system according to the present invention.

Fig. 3 is a flowchart illustrating the method for early detection of pollutants according to the present invention.

Fig. 4 is a schematic front view of a user interface for the fuel treatment system according to the present invention.

Detailed description and best mode of the present invention

The fuel treatment system is shown in Figure 1 and is labeled 10. The system 10 includes a fuel processor 12 and a fuel cell assembly 14. The fuel cell assembly 14 includes at least one fuel cell, and typically includes a plurality of fuel cells coupled together. The fuel cell assembly receives the hydrogen from the fuel processor and generates electricity as a result. The reason is that the hydrogen reacts with oxygen to form water. Then, the current generated by the fuel cell assembly is used to meet the load imposed by one or more related devices, such as vehicles, homes, generators, boats, and so on. Examples of suitable fuel cells include proton exchange membrane (PEM) fuel cells and alkaline fuel cells.

The fuel processor 12 is a device or assembly of devices suitable for generating hydrogen from a single or multi-component feedstock containing one or more feed streams via any suitable mechanism. Examples of suitable fuel processors include steam reformers. Examples of suitable mechanisms include vapor recombination, partial oxidation, incandescent recombination and pyrolysis of hydrocarbons or alcohol, and the electrolysis of water. It should be understood that the raw materials of the fuel processor 12 vary according to the specific form of the fuel processor used. For example, when the fuel processor 12 is a steam reformer, the feedstock typically contains water and alcohol or hydrocarbons. Self-heating recombination includes a water component or stream that serves as a part of the raw material, however, pyrolysis and partial oxidation do not.

For the purpose of illustration, the following description will generally describe the fuel processor 12 and its various specific embodiments. The reason is that, within the scope of the present invention, the fuel processor 12 can be any device or a series of devices that produces hydrogen. And in this article, it is implemented like a steam reformer.

A feed assembly 16 is shown in FIG. 1, which transfers raw material and water streams 18 and 20 to the fuel processor 12. The feed assembly 16 contains one or more pumps that draw logistics from a supply source (not shown). When the feedstock is soluble in water, such as methanol, the feed assembly may include a mixing chamber where the feedstock and water are premixed before being delivered to the fuel processor. Streams 18 and 20 can also be preheated before being passed to the fuel processor, or even evaporated. When the water stream is not required for the special mechanism through which the fuel processor 12 generates hydrogen, it should be understood that the fuel assembly 16 will not include the water stream 20.

The fuel processor 12 includes a hydrogen generation area 24 in which hydrogen is generated. This initial hydrogen stream 26 typically contains impurities, which must be removed before the hydrogen produced can be passed to the fuel cell assembly 14. In the context of a stream reformer, this zone can mean a reformation zone in which raw materials and water are catalytically reacted to produce a hydrogen stream containing hydrogen and by-products (or a reformed product stream). The by-products of the recombination reaction include carbon dioxide and carbon monoxide.

Stream 26 reaches a separation zone or separation assembly 30 where the hydrogen is at least partially purified to produce a product hydrogen stream 34 that contains at least a substantial portion of the hydrogen in stream 26. The separation zone 30 removes at least a portion of impurities from the stream 26, resulting in a product hydrogen stream 34 having a higher concentration of hydrogen than the stream 26. Zone 30 can retain or consume the removed portion of stream 26, or it can discharge the removed portion as by-product stream 36, as shown in FIGS. 1 and 2. A suitable form of separation zone contains one or more hydrogen screening membranes 32 that allow hydrogen to pass through to produce a product stream 34, while the remaining components of stream 26-which cannot pass through the membrane(s)-form a byproduct stream 36. The byproduct stream 36 will typically contain unreacted feedstock, some hydrogen, carbon dioxide, and carbon monoxide. Suitable hydrogen screening membranes include membranes formed of palladium, palladium alloys, or ceramics. The separation zone 30 may contain any other suitable device, or use any other suitable mechanism for purifying hydrogen, such as an adsorbent bed or a catalytic reactor. Examples of adsorbent beds include zeolite and carbon beds. Examples of catalytic reactors include water-gas shift reactors and selective oxidation reactors.

Sometimes, the product stream contains components other than hydrogen. This can happen, for example, when there are small leaks or other defects in the film(s) in the separation area. Therefore, the product stream can also contain several concentrations of carbon dioxide and carbon monoxide. Therefore, it is preferable that the fuel processor 12 includes a refining area that reduces the concentration of components harmful to the fuel cell assembly 14 below an acceptable level. In FIG. 2, a fuel processing system 10 is shown, which includes a fuel processor provided with this polishing region 38. In the refining zone 38, the concentration of non-hydrogen components in the product stream is reduced, and the specific goal is to reduce the concentration of components harmful to the fuel cell assembly 14 below an acceptable level.

For example, zone 38 may contain one or more methanation catalyst beds 40, which convert carbon monoxide and carbon dioxide in the product stream into methane and water according to the following reaction formula: CO ₂ +4H ₂ =CH ₄ +2H ₂ OCO+3H ₂ =CH ₄ +H ₂ O Because methane and water do not damage the fuel cell assembly 14, as long as the concentration of carbon monoxide and carbon dioxide is below the acceptable minimum content, the refined product stream 42 will not impair the operation of the assembly 14, as discussed in more detail below.

Sometimes, the product stream 34 also contains several concentrations of unreacted raw materials and water, which also pass through the separation zone 30. Therefore, the refining area 38 may further include a recombination area 44 to convert any unreacted raw materials into hydrogen, carbon dioxide and carbon monoxide. This increases the amount of hydrogen produced by the fuel processor, thereby improving the efficiency of the fuel processor. However, it can be understood that the recombination zone of the purification zone 38 must be upstream of the methanization bed(s) so that any carbon monoxide and carbon dioxide produced in the second recombination zone can be converted into components that will not damage the fuel cell components.

An example of a suitable logistics reorganization fuel processor with one of the refining areas is disclosed in the co-application US Patent Application No. 09/291,447, the disclosure of which is incorporated herein by reference. It should be understood that the second recombination area is not important to the present invention, and any other appropriate method may be used in the refining area to remove or reduce the concentration of components harmful to the fuel cell assembly 14. It should also be understood that the present invention can be implemented with a fuel processor that lacks a refining area.

Regardless of the specific configuration of the fuel processor, the separation zone may experience failure, that is, a significant loss in hydrogen selectivity. For example, in membrane-based purification regions, this can happen if there are physical defects in the hydrogen separation membrane, or if the membrane has tears or other holes during operation. In the event of this failure, the concentration of carbon dioxide and carbon monoxide in the product stream will increase sharply. A fuel processor that includes a refining zone can reduce these concentrations to a certain extent, however, the concentration of carbon monoxide and carbon dioxide may exceed the capacity of the refining zone 38.

The product stream that remains unchecked and reaches the fuel cell assembly will contain carbon dioxide and carbon monoxide in concentrations exceeding the acceptable minimum. Of particular concern is the concentration of carbon monoxide because the concentration of carbon monoxide as low as several parts per million may poison or permanently damage fuel cell components. Carbon dioxide is less dangerous for fuel cell components, but it also limits the concentration of carbon dioxide if desired, because it will lower the voltage of the fuel cell components and may be converted to carbon monoxide.

In order to protect the fuel cell assembly 14 from damage if the product stream contains harmful components with a concentration above the acceptable threshold content, the system 10 further includes a control system 50 that monitors the composition of the product stream leaving the fuel processor. The control system 50 includes a sensor assembly 52, which includes one or more sensors capable of detecting the concentration of specific components in the product stream. For example, the sensor assembly 52 may include a sensor that can detect the concentration of carbon monoxide in the product stream, a sensor that can detect the concentration of carbon dioxide, and the like. It should be understood that the assembly 52 may include one or more sensors that can detect the concentration of any selected components or potential impurities in the product stream. The sensor assembly 52 can additionally, or alternatively, measure the composition of the entire product stream.

The sensor assembly 52 communicates with a controller 54 via any suitable communication path. For example, the detector can send an electrical (for example, voltage or current) signal to the controller. Other, non-dedicated paths include optical signals, waveforms, or any other signals that can be received by the controller and quickly changed into control signals. The controller 52 compares the measured concentration with an acceptable threshold, such as may be stored in the memory portion 56 of the control system. Preferably, the memory part includes a nonvolatile component that stores a threshold value. Within the scope of the present invention, the sensor assembly may not only detect the composition of the product stream, but also compare the measured concentration(s) with the corresponding storage value(s) at the same time. In this embodiment, when one or more threshold concentrations are exceeded, the sensor assembly sends a signal to the controller.

When any threshold concentration is exceeded, the controller 54 automatically isolates the fuel cell assembly to prevent the contaminated product stream from reaching the assembly. The isolation of the fuel cell assembly can be implemented in any suitable manner. For example, an isolation valve 58 is shown in circles 1 and 2, which, when activated by the control system 50, prevents the product stream from reaching the fuel cell assembly. As shown, valve 58 diverts the product stream to an exhaust gas stream 60. The system 10 can be described as including an isolation assembly that includes any suitable mechanism to prevent the product hydrogen stream from flowing to the fuel cell assembly when activated. For example, the assembly may contain one or more isolation valves.

The sensor assembly 52 must measure the concentration of the product stream far enough upstream of the isolation valve 58 so that there is enough time to measure the composition of the stream, determine whether the stream is contaminated above the acceptable content, and then, before the stream reaches the component In the past, fuel cell components were isolated. Therefore, it is preferable that the sensor assembly 52 analyze the product stream located upstream of the isolation valve and as far away as possible from the isolation valve.

In the specific embodiment of the fuel processing system shown in FIG. 1, the control system 50 can measure the concentration of carbon monoxide or carbon dioxide in the product stream 34. The concentration of carbon monoxide must be less than 10 ppm (parts per million) to prevent the control system from isolating the fuel cell components. Preferably, the system limits the concentration of carbon monoxide to less than 5 ppm, and even more preferably, less than 1 ppm. The concentration of carbon dioxide can be greater than the concentration of carbon monoxide. For example, a concentration of carbon dioxide of less than 25% is acceptable. Preferably, the concentration is less than 10%, even more preferably, less than 1%. A particularly preferred concentration is less than 50 ppm. It should be understood that the acceptable minimum concentration presented here is an example, and different concentrations than those presented here can be used and are within the scope of the present invention. For example, a particular user or manufacturer may require a minimum or maximum concentration content or range that is different from those specified here.

When the fuel processor includes a refined area, such as the fuel processor shown in FIG. 2, other concentrations can be measured to replace or in addition to the above-mentioned concentrations. For example, because carbon dioxide and carbon monoxide are converted into methane and water in the methanation part of the refining area, the concentration of methane or water can be monitored. The acceptable methane concentration in the product stream 42 is less than 1%. Preferably, the concentration of methane is less than 1000 ppm, and even more preferably, less than 300 ppm. The acceptable water concentration in the product stream 42 is less than 5000 ppm. Preferably, the concentration of water is less than 1000 ppm, even more preferably, less than 300 ppm.

It should be understood that not all components measured are necessarily harmful to the fuel cell assembly. For example, neither methane nor water will damage fuel cell components. However, the concentration of these components can be measured because they indicate a malfunction in the separation area of the fuel processor. Because the refining area acts as an initial protective measure to remove carbon dioxide and carbon monoxide from the product stream within its capacity, detecting products from the refining area can provide advance detection of faults in the separation area. For example, long before the concentration of carbon dioxide or carbon monoxide exceeds the determined maximum content, it is possible to detect that the concentration of methane or water exceeds the acceptable threshold content. Therefore, detecting methane or water can detect faults earlier than detecting carbon monoxide or carbon dioxide.

Water provides earlier detection than methane because it is produced in stoichiometrically larger quantities than methane. Moreover, the detection of water may be better because water/humidity sensors are currently less expensive and less likely to interfere with other components of the product stream. Of course, as discussed above, it is preferable for the system to detect more than one component to ensure that the fuel cell assembly is detected before poisoning. Similarly, it is desirable that the sensor assembly 52 contains redundant sensors for any selected components in case one of the detectors is damaged or becomes inoperable.

Monitoring carbon dioxide must also be able to detect earlier than monitoring carbon monoxide, because the relative concentration of carbon dioxide in the product stream will increase earlier than carbon monoxide. This is because carbon monoxide is more reactive than carbon dioxide, so it will be converted into methane and water more quickly than carbon dioxide in the purification zone.

Within the scope of the present invention, the control system including the sensor assembly 52 can detect and isolate fuel cell components in response to the concentration of components (elements, compounds, ions, etc.) not discussed here. As long as an appropriate detector can detect the desired component, the controller 54 can store the relevant critical concentration value for the component, and if the critical value is exceeded, the fuel cell assembly is automatically isolated.

The above-mentioned method for preventing damage to the fuel cell assembly 14 by early detection of the failure of the fuel processor 12 is schematically shown at 62 in FIG. 3. At 64, measure the composition of the product stream. As discussed, this can include measuring the components of the entire product stream, or investigating the concentration of selected components in the stream. At 66, the measured concentration or concentration(s) are compared with the stored threshold value. These thresholds correspond to the acceptable threshold concentrations of the measured components, and if exceeded, at 68, the fuel cell assembly is isolated. If it does not exceed any critical value, the product stream is repeatedly monitored to provide periodic-preferably continuous-monitoring of the product stream.

In addition to isolating the fuel cell assembly, the control system 50 can additionally control the operation of the fuel processing system in response to a detected fault of the fuel processor. For example, the product stream must be used or discarded-now in the form of the waste gas stream 60. For example, the stream can be vented to the atmosphere. However, as desired, use the logistics 60 for other purposes. Because it is no longer applicable to the feed of the fuel cell assembly 14, it does not mean that it has no value. For example, the stream 60 may serve as fuel for the combustion unit to provide heat to the fuel processing system 10 or other devices. This combustion can occur when the fuel cell components are isolated, or the stream can be stored for future use. It can also be stored for future use instead of serving as a fuel for the combustion unit.

The control system 50 can also automatically stop the additional raw material so as not to be transferred to the fuel processor 12. Because the priming of the control system has already occurred, the signal of the fuel processor failure has been sent out, and then no additional fuel needs to be consumed until the failure is repaired. Because this typically involves shutting down the fuel processor, the control system can also automatically cause the fuel processor to start its shutdown sequence. Because the fuel cell assembly has been isolated, the hydrogen stream is no longer received from the fuel processor, and the load applied to the fuel cell assembly must also be controlled so that the capacity of the assembly to meet the load is not exceeded. The control system 50 can automatically trigger this control of the applied load. In addition to the above safety steps, the control system 50 may also trigger a response system, which may include an alarm or other appropriate devices to alert the user that the fuel processor has or is about to fail, and the fuel cell assembly is no longer processed from the fuel. The device receives the hydrogen stream.

The above-mentioned steps of the method of the present invention can be implemented by the control system, which are shown in 70-78 of FIG. 3. However, none of these steps are indispensable, and it is preferable to implement any or all of these steps with the system or method according to the present invention.

The control system 50 can be implemented in digital or analog circuits or a combination of the two. For example, the controller may contain software executed on the processor, or it may be an analog circuit. Regardless of how the controller 54 is implemented, it may-but not necessarily-include a user interface. An example of the user interface is shown in Fig. 4, and is marked as 80 as a whole. The interface 80 allows the user to monitor the operation of the controller and/or interact with it.

As shown, the interface 80 includes a display area 82 in which information is presented to the user. For example, the display area 82 may display the current value measured by the sensor assembly 52. As discussed, this may include all components of the product stream, or the concentration of selected components. Other information about the operation and performance of the fuel processing system may also be displayed in area 82. Also shown in FIG. 4 is a user signaling device 84 that warns the user when the acceptable threshold has been exceeded and the fuel cell assembly has been isolated. The device 84 may include a warning device, a light, or any other appropriate mechanism or mechanism(s) to alert the user.

The user interface 80 may also include a user input device 86 through which the user connects with the control system. For example, the input device 86 may allow the user to adjust the threshold concentration value and/or select the specific component or component(s) to be investigated. The input device 86 may include any suitable device for receiving user input, including rotary dials and switches, buttons, keyboards, keyboards, mice, touch screens, and so on.

It should be understood that within the scope of the present invention, the fuel processing system may include a control system without a user interface, and the user interface does not need to include all the components described herein. The above-mentioned elements have been collectively illustrated in Fig. 4, however, they can be implemented independently within the scope of the present invention. For example, the user interface may include a plurality of display areas, and each area can display one or more of the aforementioned user information. Similarly, a single user input device can be used, and the input device can include a display that prompts the user to enter the requested value or allows the user to touch between the input screens.

Although the present invention has been disclosed in a preferred form, the specific embodiments disclosed and described herein should not be regarded as restrictive, as various changes are possible. It is intended that any single term used herein does not exclude the use of more than one element, and embodiments using more than one specific element are within the spirit and scope of the present invention. The applicant regards the subject matter of the present invention as including all novel and non-obvious and easy-to-understand combinations and sub-combinations of the various elements, characteristics, functions, and/or properties disclosed herein. In the disclosed embodiments, no single characteristic, function, element or property is indispensable to all the embodiments. The following patent applications define specific combinations and sub-combinations, which are considered novel and non-obvious and easy to understand. After the amendment of the scope of the patent application or the proposal of the scope of the new patent application in this application or related applications, other combinations and sub-combinations of features, functions, components, and/or properties can be declared. The scope of this patent application, no matter their scope is wider, narrower or equal to the scope of the original patent application, is also deemed to be included in the subject matter of the applicant's invention.

Symbol description of main components

10. . . Fuel treatment system

12. . . Fuel processor

14. . . Fuel cell assembly

16. . . Feed assembly

18. . . raw material

20. . . Water logistics

twenty four. . . Hydrogen generation area

26. . . Initial hydrogen stream

30. . . Separation area

32. . . Hydrogen screening membrane

34. . . Product hydrogen stream

36. . . By-product logistics

38. . . Refined area

40. . . Methanation catalyst bed

42. . . Refined product logistics

44. . . Reorganization area

50. . . Control System

52. . . Sensor assembly

54. . . Controller

56. . . Memory part

58. . . Isolation valve

60. . . Exhaust gas logistics

80. . . User interface

82. . . Display area

84. . . User signaling device

86. . . User input device