HK1090754B - Architectural hierarchy of control for a fuel processor - Google Patents

Description

Architectural hierarchy for controlling fuel processors

Technical Field

The present invention relates to fuel processors and, more particularly, to control systems for fuel processors.

Background

Fuel cell technology is a more convenient energy source that additionally employs fossil fuel combustion. Fuel cells typically produce electricity, water, and heat from fuel and oxygen. More specifically, fuel cells produce electricity from chemical redox reactions and are significantly superior to other forms of electricity production in terms of cleanliness and efficiency. Typically, fuel cells use hydrogen as the fuel and oxygen as the oxidant. The power generated is proportional to the rate of consumption of the reactants.

A significant drawback that prevents widespread use of fuel cells is the lack of a widely distributed hydrogen infrastructure. Hydrogen has a relatively low volumetric energy density and is more difficult to store and transport than the hydrocarbon fuels currently used by most power generation systems. One way to overcome this difficulty is to use a "fuel processor" or "reformer" to convert the hydrocarbons into a hydrogen-rich gas stream that can be used as a feed for the fuel cell. In order to be used as a fuel for most fuel cells, hydrocarbon-based fuels, such as natural gas, LPG, gasoline, and diesel, are required to be converted. Current processes use a multi-step process combining an initial conversion process with several purification processes. The most common of this initial process is: steam reforming ("SR"), autothermal reforming ("ATR"), catalytic partial oxidation ("CPOX"), or uncatalyzed partial oxidation ("POX"). The cleanup processes often include a combination of desulfurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation, among others. Additional processes include hydrogen selective membrane reactors and filters.

Thus, a wide variety of fuels can be used, some of which are blended with fossil fuels, but the ideal fuel is hydrogen. If the fuel is, for example, hydrogen, the combustion is very clean and, in fact, only water remains after the heat has been dissipated and/or consumed, and the electricity has been consumed. Most of the immediately available fuels (e.g., natural gas, propane, gasoline) and even the less common ones (e.g., methanol and ethanol) include hydrogen in their molecular structure. Thus, some fuel cell embodiments utilize a "fuel processor" to process a particular fuel to produce a relatively pure hydrogen gas stream for use as a fuel for the fuel cell.

Although fuel cells have been in the past for centuries, their technology is still considered to be immature. The reasons for this condition are numerous and difficult to resolve. However, recent political, commercial, and environmental conditions have stimulated increased interest in fuel cell technology. This growing interest in turn has created increased space for technological development.

Despite the increased development space, it still has its own problems. Fuel cell designs, particularly those using fuel processors, are often complex. Consider the Fuel Processor design described in U.S. patent application 10/006,963 entitled "Compact Fuel Processor for Producing a Hydrogen Rich Gas", filed 12/5/2001 in the name of inventor Curtis L.Krause et al and published 7/18/2002 (publication No. US2002/009410A 1). In this design, the anode tailgas oxidation chamber temperature is a function of the catalyst charge, the air flow and its space velocity, and the oxygen to carbon ratio at a given space velocity. The number of light factors is sufficient by itself to make control of the temperature a difficult task. Furthermore, changes in fuel type-for example, from natural gas to hydrogen-greatly affect all of these variables. Thus, the problem of difficulty in control is exacerbated as fuel processor designs change.

It is an object of the present invention to solve, or at least mitigate, one or all of the above problems.

Disclosure of Invention

A control technique for use in a fuel processor is disclosed herein. In one aspect, a control system includes a subsystem manager that controls operation of a respective physical subsystem of each of a plurality of physical subsystems in a fuel processor. These subsystem managers take their guidance from the master control manager. In a second aspect, the subsystem managers collectively form a layer that works in conjunction with a second layer that can interface the subsystem managers with their respective physical subsystems, and a third layer that can interface the subsystem managers with the second layer. In a third aspect, a master control manager manages the operation of each physical subsystem through the corresponding subsystem manager, directs the transition of the state of the subsystem managers, and searches for interactions between the subsystem managers by the master control manager.

The invention discloses a device, comprising: a fuel processor comprising a plurality of physical subsystems; a control system, comprising: a first layer comprising a plurality of subsystem managers, each subsystem manager capable of controlling a respective one of the physical subsystems; a second layer capable of interfacing the subsystem managers with their corresponding physical subsystems; a third layer capable of interfacing the subsystem manager with the second layer; and a main control manager capable of controlling the fuel processor through the subsystem managers, wherein each subsystem manager comprises: an information exchange module through which the subsystem manager determines feasibility of a request event and confirms measures for implementing the requested event; and a physical module with which the information exchange module negotiates to confirm the measures for implementing the requested event; and a control module with which the physical module negotiates to determine what action should be taken to implement the requested event.

The invention also discloses a device comprising: a fuel processor comprising a plurality of physical subsystems; a control system, comprising: a plurality of devices each controlling a physical subsystem; first means for interfacing a plurality of respective control means with respective physical subsystems; second means for interfacing a plurality of respective control means with the first means; and means for controlling the fuel processor by the plurality of respective control means, wherein each of the plurality of respective control means comprises: information exchange means by which the respective control means determines the feasibility of the requested event and confirms the measures for realizing the requested event; and a measure confirming device with which the information exchange device consults to confirm a measure for implementing the requested event; and means with which the action confirmation means consults to determine what action should be taken to effect the requested event.

The invention also discloses a control system for a fuel processor, comprising: a plurality of subsystem managers, each subsystem manager capable of controlling a respective one of a plurality of physical subsystems of the fuel processor; a main control manager capable of controlling the fuel processor through the subsystem managers, wherein each subsystem manager comprises: an information exchange module by which the subsystem manager obtains a determination of the feasibility of the requested event and confirms measures for implementing the requested event; and a physical module with which the information exchange module negotiates to confirm the measures for implementing the requested event; and a control module with which the physical module negotiates to determine what action should be taken to implement the requested event.

Drawings

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 illustrates one embodiment of a control system implemented in accordance with the present invention;

FIGS. 2A and 2B, conceptually illustrate a computing device, which may be used in implementing the embodiment of FIG. 1;

FIG. 3 illustrates one embodiment of a fuel processor controlled in accordance with the present invention;

4A-4F illustrate in detail the physical subsystems of the fuel processor of FIG. 3;

FIG. 5 illustrates an embodiment of the control system of FIG. 1 for use in controlling the fuel processor of FIG. 3;

FIG. 6 illustrates the structural hierarchy of the subsystem managers of the control system in accordance with the present invention, first shown in FIG. 5;

FIG. 7 is a state machine for a physical subsystem of a specific embodiment of the present invention; and

fig. 8 schematically illustrates a reforming process of the fuel processor autothermal reformer first shown in fig. 3.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Detailed Description

Illustrative embodiments of the invention are now described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, such a development effort, even if complex and time-consuming, is a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.

The present invention is generally directed to methods and apparatus for controlling a "fuel processor," or "reformer," that is, an apparatus for converting hydrocarbon fuel to a hydrogen-rich gas. The term "fuel processor" will be used herein. The method and apparatus in the embodiments presented herein control a compact processor to produce a hydrogen-rich gas stream from a hydrocarbon fuel for use by a fuel cell. However, in other embodiments, other fuel processors may be used. Further, the apparatus and methods described herein contemplate other possible applications, including any application in which a hydrogen-rich stream is desired. The present method and apparatus may also be used in embodiments that are not applicable to the production of gas streams. Thus, although the invention is described herein as being used in connection with a fuel cell, the scope of the invention is not limited to such an application.

FIG. 1 illustrates one embodiment of a control system 100 designed, constructed, and operated in accordance with the present invention. The control system 100 includes a master control manager 102, and a plurality of physical subsystem managers 104. The number of subsystem managers 104 is not critical to the invention. Thus, FIG. 1 shows N SUBSYSTEM MANAGERs 104 as SUBSYSTEM MANAGER₀-SUBSYSTEM MANAGER_NAnd (4) marking. The number N may, in theory, be any number, although it will be apparent to those skilled in the art, having the benefit of this disclosure, that certain practical limitations may be imposed on the implementation of the specific details. However, the number of subsystem managers 104 is not critical to practicing the invention.

The control system 100 is large software implemented on a computer, such as the rack-mounted computing device 200 shown in fig. 2A and 2B. It should be noted that the computing device 200 need not be rack-mounted in all embodiments. In fact, in this regard, any given embodiment is not critical to the practice of the invention. The computing device 200 may be implemented as a personal computer, workstation, notebook, or laptop computer, or even an embedded processor.

The computing device 200 shown in fig. 2A and 2B includes a processor 205 in communication with a memory 210 over a bus system 215. The memory 210 may include a hard disk and/or random access memory ("RAM") and/or removable memory such as a floppy magnetic disk 217 and an optical disk 220. The memory 210 is encoded with a data structure 225, an operating system 230, user interface software 235, and application programs 265 that store the data sets obtained as described above. The user interface software 235, in conjunction with the display 240, implements a user interface 245. The user interface 245 may include peripheral I/O devices such as a key or keyboard 250, a mouse 255, or a joystick 260. The processor 205 operates under the control of an operating system 230, which may be virtually any operating system known in the art. The application 265 is called by the operating system 230 upon power-up, reset, or both, depending on the implementation of the operating system 230. In the illustrated embodiment, the application 265 comprises the control system 100 shown in FIG. 1.

Thus, at least some aspects of the present invention are typically implemented as software on a suitably programmed computing device, such as the computing apparatus 200 shown in FIGS. 2A and 2B. The instructions may be encoded on, for example, the memory 210, the floppy disk 217, and/or the optical disk 220. Accordingly, the present invention, in one aspect, comprises a programmed computing device for implementing the methods of the present invention. In another aspect, the invention includes a program storage device encoded with instructions that, when executed by a computing device, perform the method of the invention.

Some portions of the detailed descriptions herein are therefore presented in software as a process involving symbolic representations of operations on data bits within a memory of a computing system or computing device. These descriptions and representations are the most effective means used by those skilled in the art to convey the substance of their work to others skilled in the art. The processes and operations require physical manipulations of physical quantities. Generally, though not necessarily, these quantities take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated or otherwise as may be apparent, throughout the present disclosure, these descriptions refer to the action and processes of an electronic device, that manipulates and transforms data represented as physical quantities (electronic, magnetic, or optical) within some electronic device's memories into other data similarly represented as physical quantities within the memories, or in transmission or display devices. Examples of terms labeling such descriptions are, without limitation, the terms "processing," "computing," "calculating," "determining," "displaying," and the like.

In the illustrated embodiment, control system 100 controls a fuel processor, i.e., fuel processor 300 of FIG. 3. Fuel processor 300 includes several modular physical subsystems, namely:

an autothermal reformer ("ATR") 302 that performs an oxidation-reduction reaction to reform the fuel input to fuel processor 300 into a reformate for fuel cell 303;

an oxidizer ("ox") 304, which in the illustrated embodiment is an anode tailgas oxidizer ("ATO"), that mixes steam, fuel, and air to produce a fuel mixture that is sent to the ATR302 as a process feed stream;

a fuel subsystem 306 that delivers an input fuel (natural gas in the illustrated embodiment) to the oxidizer 304 for mixing into a process feed stream delivered to the ATR 302;

a water subsystem 308 that delivers water to the oxidizer 304 for mixing into the process feed stream to the ATR 302;

an air subsystem 310 that delivers air to the oxidizer 304 for mixing into the process feed stream to the ATR 302; and

the thermal subsystem 312 controls the operating temperature of the ATR302 by circulating a coolant (e.g., water) throughout the device.

Specific embodiments of the ATR302, oxidation chamber 304, fuel subsystem 306, water subsystem 308, air subsystem 310, and thermal subsystem 312 are depicted in fig. 4A-4F.

FIG. 4A illustrates one embodiment of fuel subsystem 306. The fuel subsystem 306 includes a fuel source 402 and provides feedstock ATO1, ATO2 to two different sections of the oxidation chamber 304. As previously mentioned, the fuel in the illustrated embodiment is natural gas, but may be other types of hydrocarbons. The hydrocarbon fuel may be in a liquid or gaseous state under ambient conditions, as long as it is capable of vaporization. The term "hydrocarbon" as used herein includes organic compounds having C-H bonds which are capable of producing hydrogen from partial oxidation or steam reforming reactions. The presence of atoms other than carbon and hydrogen in the molecular structure of the complex is not excluded. Thus, fuels suitable for use with the methods and apparatus disclosed herein include, but are not limited to, hydrocarbon fuels such as natural gas, methane, ethane, propane, butane, naphtha, gasoline, and diesel fuel, and alcohols such as methanol, ethanol, propanol, and the like. The sulfur trap 408 receives fuel from the fuel source 402 through a check valve 404 and a solenoid valve 406. The desulfurized fuel is then filtered by a filter 410 and fed to the oxidation chamber 304 through two lines 411, 413 including a control valve 412 and a flow meter 414.

Fig. 4B illustrates one embodiment of the water subsystem 308. The bucket 416 receives water from a water source 418 through a check valve 404 and a solenoid valve 406. In the illustrated embodiment, the barrel 416 also receives water from the cathode (not shown) of the fuel cell 303 via a return line 420. The pressure and volume in the barrel 416 is also controlled by a pressure reducing check valve 426 and a drain 417, wherein the drain 417 passes through the solenoid valve 406 to a drain tank 419. Water 424 in tank 416 is pumped by pump 421 to oxidation chamber 304 under the direction of controller 428 through line 425 including filter 410 and mass flow meter 427. The damper 430 dampens oscillations or undulations of the pumped water 424 on the way to the oxidation chamber 304. Air 423 is also fed to the oxidation chamber 304 via line 427.

Fig. 4C illustrates one embodiment of air subsystem 310. A compressor 432, including a motor 434, receives filtered air from the outside atmosphere via an air inlet 436, filter 410, and flow meter 414 and forces it into a barrel 438. Air from barrel 438 is then distributed to oxidation chamber 304 through two feeds ATO6, ATO7 on lines 440, 442 including flow meter 414 and control valves 444, 446. Air from the drum 438 is also distributed to the ATR302 through the feed ATR1 on line 447 including flow meter 414 and control valves 444, 446.

Fig. 4D illustrates one embodiment of the oxidation chamber 304. The oxidation chamber 304 receives fuel, water, and air from the fuel subsystem 306, water subsystem 308, air subsystem 310, and ATR302 via lines 413, 440, 427, 429, via feeds ATO2, ATO3, ATO5, ATO7, via a plurality of check valves 426, as described above. Feedstock ATO5 originates from a water separation system (discussed further below) integrated with ATR 302. Hot air 429 from the cathode (not shown) of the fuel cell 303 also flows back into the oxidation chamber 304. Exhaust 431 from the anode (not shown) of fuel cell 303 flows back to water separator 448, which water separator 448 separates the water and discharges to drain 419 via solenoid valve 406. The dehydrated anode return stream is then sent through check valve 426 to oxidation chamber 304 via line 450. The fuel, air, and dehydrated anode return streams are then mixed in the mixing chamber 452 prior to introduction into the barrel 454 of the oxidation chamber 304. The resulting mixture is then heated by electric heater 456.

Still referring to fig. 4D, the oxidation chamber 304 also receives fuel, air, and water from the fuel subsystem 306, the water subsystem 308, and the air subsystem 310 via feedstocks ATO1, ATO6, and ATO3 on lines 411, 442, and 425, respectively. Lines 411 and 442 are protected by check valve 426. The air and water received on lines 411 and 442 enter enclosed coil 458. The water received on line 425 enters the enclosed coil 460. The heated air, water, and fuel mixture in barrel 454 heats the contents of closed coils 458, 460, which are then mixed in mixer 462 and delivered to ATR302 via feed ATR2 on line 464. The oxidation chamber 304 is connected to a waste gas port 463 by a line 465.

Figure 4E illustrates one embodiment of the thermal subsystem 312. Water 466 is fed into the bucket 416 from a water source 468. It should be noted that the water source 468 is different from the water source 418 of the water subsystem 308 shown in FIG. 4B. The water 424 from the water source 418, in the illustrated embodiment, is deionized and the water 466 is not. Water 466 is circulated through portions of the ATR302 and its associated subsystems via feed ATR3, PROX1, L1, L2 on lines 471-. The water 466 previously recycled to the ATR302 is returned to the thermal subsystem 312 via feed TS1 on line 476. The ATR302 assembly directs the heat of the incoming water 466 through heat exchanger 478 and out to the ambient environment. The illustrated embodiment also employs a fan 480 to facilitate heat exchange.

Fig. 4F illustrates one embodiment of ATR 302. The ATR302 includes several stages 482a-482e that include a number of heat exchangers 478 and electric heaters 456. Each heat exchanger 478 receives temperature controlled water 466 from the thermal subsystem 312 (best shown in FIG. 4E) on lines 470-472 and returns the water on line 476. The exception is a heat exchanger 478 in a preferential oxidation ("prox") stage 482, which heat exchanger 478 receives water 466 from thermal subsystem 312 on line 473 and returns the water to water drum 416 via line 476 and feedstock TS 1. The reformate gas exiting the ATR302 passes through the prox 486, is heated by a heat exchanger 478, dewatered by a water separator 448, filtered, and finally delivered to the anode (not shown) of the fuel cell 303 (shown in fig. 3). The illustrated embodiment also includes a self-cracking tablet 484, which self-cracking tablet 484 cracks when the ATR302 is overpressurized, allowing the contents of the ATR302 to be discharged to the oxidation chamber 304 via line 440 and feedstock ATO 7.

Returning now to FIG. 3, each ATR302, oxidation chamber 304, fuel subsystem 306, water subsystem 308, air subsystem 310, and thermal subsystem 312 comprise physical subsystems that are controlled by one of the subsystem managers 104. Accordingly, one embodiment of a control system 100 for use with the embodiment of fuel processor 300 of FIG. 3 is illustrated in FIG. 5, which includes:

the main control manager 502, through these subsystem managers, manages control of the fuel processor 300:

a fuel subsystem manager 504 for controlling the delivery of fuel to the ATO 306 for mixing into the process feed stream delivered to the ATR 302;

a water subsystem manager 506 for controlling the delivery of water to the ATO 306 for mixing into the process feed stream delivered to the ATR 302;

an air subsystem manager 508 for controlling the delivery of air to the ATO 306 for mixing into the process feed stream delivered to the ATR 302;

an ATO subsystem manager 510 for controlling the mixing of the steam, fuel, and air to produce a fuel mixture that is passed to the ATR302 as a process feed stream;

an ATR subsystem manager 512 for controlling the oxidation-reduction reaction in the ATR302, which ATR302 reforms the fuel input to the fuel processor 300 into a reformate for use by the fuel cell 303; and

the thermal subsystem manager 514, through the thermal subsystem 312, controls the operating temperature in the ATR 302.

Thus, each subsystem manager 504-.

The control system 500 also includes an additional layer that facilitates modularity of the control system in a hierarchical manner. More specifically, control system 500 includes a hardware dependent layer 516 and a "compatibility" layer 518. Aspects of the hardware dependent control functionality are separated and integrated into the dependent hardware layer 516. For example, referring to FIG. 4A, to increase the flow of fuel 402 to the oxidation chamber 304, one or both of the control valves 414 are opened. A control signal (also not shown) is then transmitted from the control system 500 to an actuator (also not shown) that controls the valve 414, and the characteristics of the signal are hardware dependent. The functions of actually generating and transmitting the control signal are concentrated into the dependent hardware layer 516. Thus, if, for example, hardware in fuel subsystem 306 needs to change from one model to another, then only dependent hardware layer 516 has to be modified. Compatibility layer 518 translates instructions issued by subsystem manager 504 and 514 so that they are compatible with the hardware of fuel processor 300. For example, a subsystem manager 504, 514, may request an event using a particular unit of measure. The hardware required to implement the request may fetch instructions in the second unit of measure. The compatibility layer 518 translates instructions issued by the subsystem manager 504-514 in the first unit of measure into instructions in the second unit of measure employed by the hardware so that they can be implemented by the dependent hardware layer 516.

The illustrated embodiment of the control system 500 further includes a diagnostic layer 520 that also facilitates modularity of the control system in a hierarchical manner. Each subsystem manager 504-. More specifically, subsystem manager 504 monitors 514 for a "shutdown" condition, i.e., a sufficiently important error condition worth shutting down fuel processor 300. The error conditions detected by subsystem manager 504 and 514 are reported to master control manager 502 via diagnostic layer 502.

Each subsystem manager 504-514 also contains a modular internal structure 600, shown conceptually in FIG. 6. Each subsystem manager 504-514 employs the modular internal structure 600 to direct its traffic in the corresponding physical subsystem 302, 304-312. Each subsystem manager 504-514 includes:

the information exchange module 605, the specific subsystem manager 504 and 514 pass through the information exchange module 605 to determine the feasibility of implementing the event requested by the other subsystem manager 504 and 514 through the main control manager 502, and confirm the measures for implementing the requested event;

a diagnostic module 610, the diagnostic module 610 communicating with the diagnostic layer 520 through the information exchange module 605 to report an error condition;

a physical module 615 with which the information exchange module 605 negotiates to confirm that the action requiring the event is implemented, and a diagnostic module communicates with the physical module 615 to obtain information regarding the error condition; and

the control module 620, the physical module 615, and the control module 620 negotiate to determine what action should be taken to implement the requested event, and the diagnostic module communicates with the dependent hardware layer 516 through the compatibility layer 518 through the control module 620 to obtain this determined information.

In other embodiments where the control system 500 omits the diagnostic layer 520, the diagnostic module 610 may be omitted from the subsystem manager 504 and 514.

Returning to FIG. 5, in the illustrated embodiment, the subsystem managers 504 and 514 cooperate with each other by communicating with each other as required by their information exchange modules 605 through the master control manager 502. For example, consider the situation in which the oxidation chamber 304 of FIG. 3 is first shown, a drop in feed pressure is sensed from the fuel subsystem 306, which fuel subsystem 306 is also first shown in FIG. 3. Then the ATO subsystem manager 510 may request an increase in fueling. In the illustrated embodiment, the increase in fuel should be considered an "event". The ATO subsystem manager 510 issues a request by the message exchange module 605 shown in fig. 6, which the message exchange module 605 notifies the primary control manager 502. The master control manager 502 forwards the request to the appropriate physical subsystem manager, in this case the fuel subsystem manager 504.

The fuel sub-system manager 504 accepts the request via its own message exchange module 605, and the fuel sub-system manager 504 checks whether it is in the appropriate state to implement the request (discussed further below). If the requested event is allowable and feasible, then fuel subsystem manager 504 implements the requested event. The message exchange module 605 instructs the physical module 615 to implement the required event. The message exchange module 605 queries the controller module 620 what action must be taken. The information exchange module 605 then notifies the physical module 615 of those actions that must be taken. The physical module 615 then issues instructions corresponding to those measures to a hardware actuator (not shown) by relying on the hardware layer 516 to traverse the compatibility layer 518.

The master control manager 502 also controls the operational status of the entire system 300 through the subsystem managers 504 and 514. Consider, for example, state diagram 700 of FIG. 7, which represents the operational states of and transitions between subsystem managers 504 and 514. Each subsystem manager 504-514 transitions through eight different states, although not through all eight states in any duty cycle:

an "open" state 702;

a "manager check" state 704 in which the subsystem managers 504 and 514 check the operational readiness of their respective physical subsystems 302 and 312;

a "manual operation" state 706 in which the operator can direct the operation of the entire system;

a "preheat" state 708 in which the fluid of the heating unit and the overall system 300 is preheated or precooled to a level designated for their normal operation;

a "start" state 710 in which the entire system 300 begins operating in a start condition;

a "run" state 712 in which the entire system 300 is operating under steady state conditions;

an "off state 714 in which the physical subsystems of the overall system shut down their work to the end of the work cycle plan; and

an "emergency shutdown" state 716 in which physical subsystems are shut down in response to the occurrence or detection of an emergency condition in one or more of the physical subsystems.

Although each subsystem manager 504-514 transitions through the same eight state transitions, the tasks assigned to each subsystem manager 504-514 will be unique from the perspective of the requirements of their corresponding physical subsystem 302-312. For example, the tasks performed by the fuel subsystem manager 504 in the run state 712, unlike the tasks performed by the ATR subsystem manager 512 in the run state, give differences in the operation and function of the fuel subsystem 306 and ATR302, both the fuel subsystem 306 and ATR302 being shown in fig. 3.

Returning now to FIG. 7, from the tripped state 702, the subsystem manager 504 transitions 514 either into the manager check state 704 or into the manual operation state 706. From the manual operation state 706, the subsystem manager 504-514 can only transition to either the shutdown state 714 or the emergency shutdown state 716. From the manager check state 704, the subsystem manager 504-514 may transition through the preheat state 708, the startup state 710, and the run state 712 in this order. The subsystem manager 504 can transition from any other state, either into the off state 714 or into the emergency off state 716.

Referring now to fig. 5 and 7, the operator may choose whether to enter the manual operating state 706 when powering up or when initializing the system, i.e., leaving the off state 702. If the operator does not select the manual operation state 706, then the master control manager 502 assumes control. In the manual state 706, the operator may select a percentage of the workload amount and the system is ramped up to a set point at a specified level, but still implement the control logic. That is, subsystem managers 504 and 514 still cooperate with each other through master control manager 500 as described above.

Assuming now that the operator is not assuming manual control, master control manager 502 signals each subsystem manager 504 and 514 to transition to manager check state 704. Thus, each subsystem manager 504-514 performs tasks related to the manager check state 704. When the various subsystem managers 504 and 514 have completed their tasks associated with the manager check state 704, they signal this fact to the master control manager 502. The master control manager 502 waits until all subsystem managers 504 and 514 have signaled that they have completed, and then the master control manager 502 signals the subsystem managers 504 and 514 to transition to the preheat state 708.

The above process is repeated as subsystem manager 504 transitions 514 through the remaining states. It should be noted that subsystem manager 504-514 only transitions to the next state when master control manager 502 signals subsystem manager 504-514 to transition to the next state. It should also be noted that master control manager 502 signals subsystem manager 504 and 514 to transfer only when all subsystem managers 504 and 514 are ready to transfer. Thus, subsystem managers 504 and 514 transfer their state in a synchronized manner under the direction of master control manager 502.

Referring now to FIG. 5, master control manager 502 controls the overall operation of fuel processor 300 in two ways. First, communications between each subsystem manager 504 and 514 are routed through master control manager 502. Second, master control manager 502 controls the operational state of subsystem manager 504 and 514.

Referring now to fig. 3 and 5, the operation of fuel processor 300 under the control of control system 500 is illustrated. Upon power-up or reset, the fuel processor 300 and the control system 500 either transition from the tripped state 702 to the manager check state 704 or to the manual operation state 706, depending on operator input. Assuming again that the operator is not assuming manual control, master control manager 502 signals subsystem manager 504 and 514 to transition to manager check state 704, in which subsystem manager 504 and 514 check the operational readiness of their respective physical subsystems. Once each subsystem manager 504-514 signals the master control manager 502 that their corresponding physical subsystem has passed the manager check, the master control 502 signals the subsystem manager 504-514 to transition to a preheat state 708 in which the heating units or fluids of the corresponding physical subsystem are preheated or precooled to a level specified by their normal operation.

Once all subsystem managers 504-514 signal that their respective physical subsystems have completed the warm-up task, the master control manager 502 signals them to transition to a startup state 710 in which the entire system 300 begins operating under startup conditions 710. It will be apparent to those skilled in the art having the benefit of this disclosure that fuel processor 300 cannot simply be put into production. For example, the oxidation chamber 304 cannot begin mixing the process feed stream until it has fuel, water, and air that can mix. Likewise, the ATR302 cannot begin reforming fuel until it has received sufficient process feed stream from the oxidation chamber 304. Thus, in startup state 710, out-of-range pressures, volumes, etc. are not triggered, and a shutdown error condition is tolerated until fuel processor 300 reaches steady state operation.

Once all subsystem managers 504-514 signal that their respective physical subsystems have reached a steady state operating condition, master control manager 502 signals that they transition to run state 712. In the run state 712, the entire system 300 is operating under steady state conditions. The overall function of fuel processor 300, as shown in fig. 4A, is to reform fuel 402 for use by fuel cell 303. Thus, the operation of the fuel processor 300, surrounding the operation of the ATR302, and the delivery of fuel (shown in FIG. 4A), air (shown in FIG. 4C), and water (shown in FIG. 4B) from the fuel subsystem 306, water subsystem 308, and air subsystem 310 to the ATR302 is central.

FIG. 8 depicts a flowchart of a general process, illustrating the process steps included in an illustrative embodiment of the present invention. The following description taken in conjunction with FIG. 8 is entitled "Compact Fuel Processor for Producing a Hydrogen RichGas" from U.S. patent application 10/006,963, filed on 5.12.2001 in the name of inventor Curtis L.Krause et al and published on 18.7.2002 (publication No. US2002/009410A 1). It will be appreciated by those skilled in the art that some amount of progressive processing is necessary in the flow of reactants through the reactor as disclosed herein. The feedstock to fuel processor 300 includes hydrocarbon fuel, oxygen, and water. The oxygen may be in the form of air, oxygen-enriched air, or substantially pure oxygen. The water may be introduced as a liquid or as a vapor. The compositional percentages of the feed components, as determined by the desired operating conditions, are discussed below. The effluent stream of a fuel processor according to the present invention comprises hydrogen and carbon dioxide and can also include some water, unconverted hydrocarbons, carbon monoxide, impurities (such as hydrogen sulfide and ammonia), and embedded components (such as nitrogen and argon, particularly where air is used as a feed stream component).

Process step a is an autothermal reforming process in which two reactions, partial oxidation (equation I below) and optionally steam reforming (equation II below), are carried out in combination in blocks 482a and 482b of fig. 4A to convert feed stream F to a synthesis gas containing hydrogen and carbon monoxide. Equations I and II below are exemplary reaction equations in which the hydrocarbon under consideration is methane:

CH₄+1/2O₂→2H₂+CO (I)

CH₄+H₂O→3H₂+CO (II)

the ATR302 receives a fuel stream F from the oxidizer 304 on line 434 as shown in fig. 4D and 4F. Higher oxygen concentrations in the feed stream favor partial oxidation, while higher water vapor concentrations favor steam reforming. Thus, the oxygen to hydrocarbon and water to hydrocarbon ratios are parameters that characterize the effects on operating temperature and hydrogen production.

The operating temperature of the autothermal reforming step a, which may range from about 550 c to about 900 c, depends on the feed conditions and the catalyst. These ratios, temperatures, and feed conditions are all examples of parameters controlled by the control system of the present invention. The illustrated embodiment uses a catalyst bed of partial oxidation catalyst with or without a steam reforming catalyst in block 482 a.

Returning now to fig. 8, process step B is a cooling step, performed in block 482c of fig. 4F, for cooling the synthesis gas stream from step a to a temperature of from about 200 c to 600 c, preferably from about 375 c to 425 c, to optimize the temperature of the synthesis gas effluent for the next step. This cooling method may be accomplished with fins, heat pipes, or heat exchangers, depending on the design criteria, and the need to use any suitable type of coolant to recover/reuse the heat from the gas stream. The illustrated embodiment uses water 466 received from water 466 on line 470 as shown in fig. 4E and 4F.

Referring again to fig. 8, process step C is a purification step, performed in block 482C, and using zinc oxide as a hydrogen sulfide absorbent. One of the main impurities of the hydrocarbon stream is sulfur, which is converted to hydrogen sulfide by the autothermal reforming step a. The treatment core used in step C preferably comprises zinc oxide and/or other materials capable of absorbing and converting hydrogen sulfide, and may also comprise a support (e.g., monolith, extrudate, particulate material, etc.). The sulfur removal is accomplished by converting hydrogen sulfide to water according to the following reaction scheme III:

H₂S+ZnO→H₂O+ZnS (III)

the reaction is preferably carried out at a temperature of from about 300 ℃ to 500 ℃ and more preferably from about 375 ℃ to 425 ℃. The temperature is also controlled by the control system of the present invention.

Referring again to fig. 8, the effluent stream is then sent to a mixing step D implemented at block 482D, where water received from the water subsystem 308 is optionally added to the gas stream. The addition of water, as it evaporates and supplies more water for the water gas shift reaction of process step E (discussed below), lowers the temperature of the reactant stream. The water vapor and other effluent stream components are mixed as they pass through the central portion of the intercalation material, such as ceramic beads or other similar materials that efficiently mix and/or assist in the evaporation of the water. In addition, any added water may be introduced with the feedstock and the mixing step may be repeated to provide better mixing of the oxidant gas in the CO oxidation step G (discussed below). The temperature of this step D is also controlled by the control system of the present invention.

Returning to fig. 8, process step E, which is performed in block 482E, is a water gas shift reaction that converts carbon monoxide to carbon dioxide according to equation IV:

H₂O+CO→H₂+CO₂ (IV)

the concentration of carbon monoxide is preferably below that which can be tolerated by the fuel cell, typically below 50 ppm. In general, the water-gas shift reaction can occur at temperatures from 150 ℃ to 600 ℃, depending on the catalyst used. Under such conditions, most of the carbon monoxide in the gas stream is converted in this step. The temperature and concentration are further parameters that the control system of the present invention controls.

Referring again to fig. 8, process step F, which is performed in block 482e, is a cooling step performed by heat exchanger 478 in the illustrated embodiment. The heat exchanger 478 lowers the temperature of the gas stream to produce an effluent that is preferably at a temperature in the range of about 90 c to about 150 c. In the process of step F, oxygen from air subsystem 310 is also added on line 498 as shown in FIG. 4C and FIG. 4F. Oxygen is consumed by the reaction of the treatment step G described below.

Process step G, performed in block 482G, is an oxidation step in which substantially all of the remaining carbon monoxide is converted to carbon dioxide in the effluent stream. The treatment is carried out in the presence of a catalyst to oxidize the carbon monoxide. There are two reactions in process step G: the desired carbon monoxide oxidation (equation V) and the undesired hydrogen oxidation (equation VI), listed thereafter:

CO+1/2O₂→CO₂ (V)

H₂+1/2O₂→H₂O (VI)

low temperatures favor preferential carbon monoxide oxidation. Since both reactions generate heat, it is advantageous to optionally include a cooling unit, such as a cooling coil, placed during the process. The operating temperature of the treatment process is preferably maintained in the range of about 90 c to about 150 c. Process step G reduces the carbon monoxide concentration to preferably a minimum of 50ppm, which is a concentration suitable for use in fuel cells.

The effluent leaving the fuel processor is a hydrogen-rich gas containing carbon dioxide and other components that may be present, such as water, embedded components (e.g., nitrogen, argon), residual hydrocarbons, and the like. The produced gas can be used as a feedstock for fuel cells or for other applications requiring a hydrogen-rich feed stream. The produced gas may optionally be forwarded for further processing, such as removal of carbon dioxide, water, or other components.

Finally, the work cycle ends. If the termination is planned, then master control manager 502 signals subsystem manager 504 and 514 to transition to the off state 714 at the appropriate time. As described above, subsystem managers 504-514 monitor for the occurrence of their respective physical subsystem error conditions through their diagnostic modules 610 shown in FIG. 6. Some error conditions permit the operation of fuel processor 300 to be shut down. If such a "shut down" error condition is detected, its subsystem manager 504 is detected 514, and the error is reported to master control manager 502 via diagnostic module 610 and diagnostic layer 520 shown in FIG. 5. The main control module 502 then signals the subsystem manager 504 and 514 to transition to the emergency shutdown state 716.

The modular design resulting from the hierarchical nature of the present invention has the flexibility to allow control systems to be expanded. Entire subsystems may be removed, added, and/or replaced to test, evaluate, and modify subsystem designs without major adjustments to the control system. The control algorithm is not hardware dependent except for a hardware dependent layer which contains meter calibration data. Thus, various types of meters can be added, removed, or replaced without affecting the control system as a whole and without requiring much reprogramming. Thus, the present invention allows for quick and easy expansion of the present process control system, yet facilitates the close insertion of new subsystems. The present invention also allows developers to build control software for a variety of physical subsystems, which may be relatively simple in performance, on an individual or on different teams of developers. This advantage is particularly useful in rapidly evolving technologies, such as fuel processor/fuel cell designs with complex control systems.

And finally, the detailed description is finished. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.

Claims (24)

1. An apparatus, comprising:

a fuel processor comprising a plurality of physical subsystems;

a control system, comprising:

a first layer comprising a plurality of subsystem managers, each subsystem manager capable of controlling a respective one of the physical subsystems;

a second layer capable of interfacing the subsystem managers with their corresponding physical subsystems;

a third layer capable of interfacing the subsystem manager with the second layer; and

a main control manager capable of controlling the fuel processor through the subsystem manager,

wherein each subsystem manager comprises:

an information exchange module through which the subsystem manager determines feasibility of a request event and confirms measures for implementing the requested event; and

a physical module with which the information exchange module negotiates to confirm the measures for implementing the requested event; and

a control module with which the physical module negotiates to determine what action should be taken to implement the requested event.

2. The apparatus of claim 1, wherein the physical subsystem comprises:

a first subsystem capable of reforming a fuel, air, and steam mixture;

a second subsystem capable of mixing fuel, air, and vapor with the gas and air to produce a mixture and transferring the mixture to the first subsystem;

a third subsystem capable of delivering fuel to the second subsystem;

a fourth subsystem capable of delivering water to the second subsystem;

a fifth subsystem capable of delivering air to the second subsystem; and

and the sixth subsystem can manage the working temperature of the first subsystem.

3. An apparatus according to claim 2, wherein the fuel is a hydrocarbon.

4. An apparatus according to claim 3, wherein the hydrocarbon is a gas or a liquid.

5. The apparatus of claim 3, wherein the hydrocarbon comprises one of natural gas, coal gas, liquid petroleum gas, gasoline, and diesel.

6. The apparatus of claim 1, wherein the control system further comprises a fourth layer through which the subsystem managers can report error conditions in their respective physical subsystems.

7. The apparatus of claim 6, wherein each subsystem manager further comprises a diagnostic module that negotiates with the control module and the physical module to monitor a fault condition of the physical subsystem.

8. The apparatus of claim 1, wherein the master control manager is capable of controlling the fuel processor by directing state transitions of the subsystem managers and seeking interaction between the subsystem managers.

9. The apparatus of claim 1, further comprising a fuel cell.

10. The apparatus of claim 9 wherein the fuel cell is a PEM fuel cell.

11. An apparatus, comprising:

a fuel processor comprising a plurality of physical subsystems;

a control system, comprising:

a plurality of devices each controlling a physical subsystem;

first means for interfacing a plurality of respective control means with respective physical subsystems;

second means for interfacing a plurality of respective control means with the first means; and

means for controlling the fuel processor by the plurality of respective control means,

wherein each of the plurality of respective control devices comprises:

information exchange means by which the respective control means determines the feasibility of the requested event and confirms the measures for realizing the requested event; and

means for confirming the measure with which the information exchange means consults to confirm the measure for implementing the requested event; and

means with which the means for action validation consults to determine what action should be taken to implement the requested event.

12. The apparatus of claim 11, wherein the physical subsystem comprises:

a first subsystem capable of reforming a fuel, air, and steam mixture;

a second subsystem capable of mixing fuel, air, and vapor with the gas and air to produce a mixture and transferring the mixture to the first subsystem;

a third subsystem capable of delivering fuel to the second subsystem;

a fourth subsystem capable of delivering water to the second subsystem;

a fifth subsystem capable of delivering air to the second subsystem; and

and the sixth subsystem can manage the working temperature of the first subsystem.

13. The apparatus of claim 11, wherein the control system further comprises means by which the respective control means can report error conditions in their respective physical subsystems.

14. The apparatus of claim 11 wherein the fuel processor control means controls the fuel processor by directing a transition in the state of the respective control means and seeking interaction between the respective control means.

15. The apparatus of claim 11, further comprising a fuel cell.

16. A control system for a fuel processor, comprising:

a plurality of subsystem managers, each subsystem manager capable of controlling a respective one of a plurality of physical subsystems of the fuel processor;

a main control manager capable of controlling the fuel processor through the subsystem managers,

wherein each subsystem manager comprises:

an information exchange module by which the subsystem manager obtains a determination of the feasibility of the requested event and confirms measures for implementing the requested event; and

a physical module with which the information exchange module negotiates to confirm the measures for implementing the requested event; and

a control module with which the physical module negotiates to determine what action should be taken to implement the requested event.

17. The control system of claim 16, further comprising:

a first layer capable of interfacing subsystem managers with their corresponding physical subsystems;

the second layer can interface the subsystem manager with the first layer.

18. The control system according to claim 17, wherein the control system further comprises a third layer through which the subsystem managers can report error conditions in their respective physical subsystems.

19. The control system according to claim 16, wherein the control system further comprises a layer through which the subsystem managers can report error conditions in their respective physical subsystems.

20. The control system of claim 16, wherein each subsystem manager further comprises a diagnostic module that negotiates with the control module and the physical module to monitor the physical subsystem for fault conditions.

21. The control system of claim 16, wherein the main control manager is capable of controlling the fuel processor by directing a transition of the state of the subsystem managers and seeking interaction between the subsystem managers.

22. The control system of claim 21, wherein the subsystem manager transitions between a plurality of states, the plurality of states comprising:

an open circuit state;

at least one operating state into which the subsystem can be transferred from the off state; and

at least one off state into which the subsystem can transition from any of the operating states.

23. A control system according to claim 22, wherein the at least one operating condition comprises at least one of:

a manual state into which the subsystem can transition from the off state;

the manager checks the state, the subsystem can be transferred from the open state to enter the state;

a preheating state, wherein the subsystem can be transferred from the manager checking state to enter the state;

a startup state, into which the subsystem may transition from the preheat state; and

the run state, the subsystem may transition from the startup state into which it is entered.

24. A control system according to claim 22, wherein the at least one off state comprises at least one of:

a standard off state; and

an emergency off state.