Combinational control strategy for fuel processor reactor shift temperature control

A method and apparatus for use in controlling the reaction temperature of a fuel processor are disclosed. The apparatus includes a fuel processor reactor, the reactor including a water gas shift reaction section; a temperature sensor disposed within the reaction section; a coolant flow line through the reaction section; and an automated control system. The automated control system controls the reaction temperature by determining a first component for a setting adjustment for the actuator from the measured temperature and a setpoint for the measured temperature; determining a second component for the setting adjustment from a hydrogen production rate for the fuel processor; and determining the setting adjustment from the first and second components.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a fuel processor, and, more particularly, to a control system for use in a fuel processor.

2. Description of the Related Art

There are numerous uses for pure hydrogen or hydrogen-enriched gas streams. For instance, fuel cells—a promising alternative energy source—typically employ hydrogen as a fuel for generating power. Many industrial processes also employ hydrogen or hydrogen-enriched gas streams in a variety of fields for the manufacture and production of a wide assortment of end products. However, pure hydrogen is not available as a natural resource in a form that can be readily exploited. As an example, natural gas, a hydrocarbon-based fuel, is frequently found in large subterranean deposits that can be easily accessed and transported once tapped. Nature does not provide such deposits of hydrogen.

One way to overcome this difficulty is the use of “fuel processors” or “reformers” to convert hydrocarbon-based fuels to a hydrogen rich gas stream which can be used as a feed for fuel cells. Hydrocarbon-based fuels, such as natural gas, liquid petroleum gas (“LPG”), gasoline, and diesel, require conversion for use as fuel for most fuel cells. Current art uses multi-step processes combining an initial conversion process with several clean-up processes. The initial process is most often steam reforming (“SR”), autothermal reforming (“ATR”), catalytic partial oxidation (“CPOX”), or non-catalytic partial oxidation (“POX”). The clean-up processes are usually comprised of a combination of desulfurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation. Alternative processes include hydrogen selective membrane reactors and filters.

More particularly, the ATR performs a water-gas shift reaction that reduces CO concentration and increases H2production rate. This reaction is exothermal and sensitive to the temperature. Shift reaction temperature control is therefore a significant element for continuously making stable, low CO concentration and high H2yield reformate. And, better temperature control provides a more consistent, higher quality end product.

SUMMARY OF THE INVENTION

The invention is a method and apparatus for use in controlling the reaction temperature of a fuel processor. The apparatus comprises a fuel processor reactor, the reactor including a water gas shift reaction section; a temperature sensor disposed within the reaction section; a coolant flow line through the reaction section; and an automated control system. The automated control system controls the reaction temperature by determining a first component for a setting adjustment for the actuator from the measured temperature and a setpoint for the measured temperature; determining a second component for the setting adjustment from a hydrogen production rate for the fuel processor; and determining the setting adjustment from the first and second components.

While the invention is susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments herein described in detail by way of example. 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 OF THE INVENTION

The present invention is generally directed to method and apparatus for controlling the reaction temperature of a “fuel processor,” or “reformer,” i.e., an apparatus for converting hydrocarbon fuel into a hydrogen rich gas. The term “fuel processor” shall be used herein. In the embodiment illustrated herein, the method and apparatus control a compact processor for producing a hydrogen rich gas stream from a hydrocarbon fuel. However, other fuel processors may be used in alternative embodiments. Furthermore, many possible uses are contemplated for the apparatus and method described herein, including any use wherein a hydrogen rich stream is desired. For instance, synthesis gas streams derived from gasification or otherwise that comprise hydrogen and CO are commonly subjected to water gas shift reactions to convert CO to hydrogen and CO2. The method and apparatus may also be used in embodiments not applicable to the production of gas streams.

FIG. 1illustrates an apparatus100including a fuel processor102fed a fuel104and operating under an automated control system106, represented by a computing apparatus108. The fuel processor102reforms the fuel104to produce a reformate110. The automated control system106controls the process by which the fuel processor102reforms the fuel104into the reformate110. The design of the fuel processor102, and the reforming process, will depend to a large degree on the fuel104input to the fuel processor102and the end use to which the reformate110will be put.

The fuel processor102may be a self-contained auto-thermal reforming (“ATR”) fuel processor that converts pipeline-quality natural gas to fuel cell grade fuel, although the invention may be practiced with alternative fuels and end applications. For instance, the reformate110may be output to a pressure swing adsorber (“PSA”) unit115for the production of a purified hydrogen, or a hydrogen enriched gas stream112. Means other than a PSA may be utilized for purifying or concentrating hydrogen. The purified hydrogen112can then be stored and/or distributed to an end application such as powering a fuel cell112, such as a conventional Proton Exchange Membrane Fuel Cell (“PEMFC”), also known as a Polymer Electrolyte Fuel Cell (“PEFC”), for example.

As previously mentioned, the fuel in the illustrated embodiment is natural gas, but may be some other type of hydrocarbon. The hydrocarbon fuel may be liquid or gas at ambient conditions as long as it can be vaporized. As used herein the term “hydrocarbon” includes organic compounds having C—H bonds which are capable of producing hydrogen from a partial oxidation or steam reforming reaction. The presence of atoms other than carbon and hydrogen in the molecular structure of the compound is not excluded. Thus, suitable fuels for use in the method 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 fuel processor102provides a hydrogen-rich effluent stream, or “reformate,” as indicated by the graphic110, to the fuel cell112or the PSA unit115, for example. The reformate110, in the illustrated embodiment, includes hydrogen and carbon dioxide and can also include some water, unconverted hydrocarbons, carbon monoxide, impurities (e.g., hydrogen sulfide and ammonia) and inert components (e.g., nitrogen and argon, especially if air was a component of the feed stream). Note, however, that the precise composition of the reformate110is implementation specific and not material to the practice of the invention.

FIG. 2illustrates one particular embodiment of the fuel processor102of the illustrated embodiment. The fuel processor102comprises several modular physical subsystems, namely:an autothermal reformer (“ATR”)210that performs a partial oxidation and a steam reforming reaction to reform the fuel104into the reformate110;an oxidizer (“Ox”)214, which is an anode tailgas oxidizer (“ATO”) in the illustrated embodiment, that preheats water216, fuel104, and air218for delivering a heated fuel mixture, or “process feed stream”,220to the ATR210;a fuel subsystem222, that delivers an input fuel104to the oxidizer214for preheating and inclusion in the process feed stream220delivered to the ATR210;a water subsystem224, that delivers the water216to the oxidizer214for conversion to steam and inclusion in the process feed stream220delivered to the ATR210;an air subsystem226, that delivers air218to the oxidizer214for mixing into the process feed stream220delivered to the ATR210; anda thermal subsystem228, that controls temperatures in the operation of the ATR210by circulating a coolant216therethrough.
One particular embodiment of the ATR210is disclosed more fully below. The fuel subsystem222, water subsystem224, air subsystem225, and thermal subsystem228may be implemented in any manner known to the art suitable for achieving the operational characteristics of the oxidizer214and ATR210.

FIG. 3is a general process flow diagram illustrating the process steps300included in the illustrative embodiments of the present invention as performed by the ATR210to produce the reformate110, first shown inFIG. 1. The following description associated withFIG. 3is adapted from U.S. patent application Ser. No. 10/006,963, entitled “Compact Fuel Processor for Producing a Hydrogen Rich Gas,” filed Dec. 5, 2001, in the name of the inventors Curtis L. Krause, et al., and published Jul. 18, 2002, (Publication No. US2002/0094310 A1).

The fuel processor102process feed stream220includes a hydrocarbon fuel, oxygen, and water mixture, as was described above. The oxygen can be in the form of air, enriched air, or substantially pure oxygen. The water can be introduced as a liquid or vapor. The composition percentages of the feed components are determined by the desired operating conditions, as discussed below. The fuel processor effluent stream (not shown) of the present invention includes hydrogen and carbon dioxide and can also include some water, unconverted hydrocarbons, carbon monoxide, impurities (e.g., hydrogen sulfide and ammonia) and inert components (e.g., nitrogen and argon, especially if air was a component of the feed stream).

Process step A is an autothermal reforming process in which, in one particular embodiment, two reactions, a partial oxidation (formula I, below) and an optional steam reforming (formula II, below), are performed to convert the feed stream220into a synthesis gas containing hydrogen and carbon monoxide. Formulas I and II are exemplary reaction formulas wherein methane is considered as the hydrocarbon:
CH4+½O2→2H2+CO  (I)
CH4+H2O−>3H2+CO  (II)
The process feed stream220is received by the processor reactor from the oxidizer214, shown inFIG. 2. A higher concentration of oxygen in the process feed stream220favors partial oxidation whereas a higher concentration of water vapor favors steam reforming. The ratios of oxygen to hydrocarbon and water to hydrocarbon are therefore characterizing parameters that affect the operating temperature and hydrogen yield.

The operating temperature of the autothermal reforming step A can range from about 550° C. to about 900° C., depending on the feed conditions and the catalyst. The ratios, temperatures, and feed conditions are all examples of parameters that can be controlled by the control system of the present invention. The illustrated embodiment uses a partial oxidation catalyst and a steam reforming catalyst in reforming process step A.

Process step B is a cooling step for cooling the synthesis gas stream from process step A to a temperature of from about 200° C. to about 600° C., preferably from about 375° C. to about 425° C., to prepare the temperature of the synthesis gas effluent for the process step C (discussed below). This cooling may be achieved with heat sinks, heat pipes or heat exchangers depending upon the design specifications and the need to recover/recycle the heat content of the gas stream using any suitable type of coolant. For instance, the coolant for process step B may be the coolant216of the thermal subsystem228.

Process step C is a purifying step and employs zinc oxide (ZnO) as a hydrogen sulfide absorbent. One of the main impurities of the hydrocarbon stream is sulfur, which is converted by the autothermal reforming step A to hydrogen sulfide. The processing core used in process step C preferably includes zinc oxide and/or other material capable of absorbing and converting hydrogen sulfide, and may include a support (e.g., monolith, extrudate, pellet, etc.). Desulfurization is accomplished by converting the hydrogen sulfide to zinc sulfide in accordance with the following reaction formula III:
H2S+ZnO→H2O+ZnS  (III)
The reaction is preferably carried out at a temperature of from about 300° C. to about 500° C., and more preferably from about 375° C. to about 425° C.

Still referring toFIG. 3, the effluent stream may then be sent to a mixing step D in which water216received from the water subsystem224, both shown inFIG. 2, is optionally added to the gas stream. The addition of water lowers the temperature of the reactant stream as it vaporizes and supplies more water for the water gas shift reaction of process step E (discussed below). The water vapor and other effluent stream components are mixed by being passed through a processing core of inert materials such as ceramic beads or other similar materials that effectively mix and/or assist in the vaporization of the water. Alternatively, any additional water can be introduced with the feed220, and the mixing step can be repositioned to provide better mixing of the oxidant gas in the CO oxidation step G (discussed below). This temperature can also controlled by the control system of the present invention.

Process step E is a water gas shift reaction that converts carbon monoxide to carbon dioxide in accordance with formula IV:
H2O+CO→H2+CO2(IV)
The concentration of carbon monoxide in the final reformate should preferably be lowered to a level that can be tolerated by fuel cells, typically below 50 ppm. Generally, the water gas shift reaction can take place at temperatures of from 150° C. to 600° C. depending on the catalyst used. Under such conditions, much of the carbon monoxide in the gas stream is converted. This temperature and concentration are more parameters that are controlled by the control system of the present invention.

Referring still toFIG. 3, process step F is a cooling step. Process step F reduces the temperature of the gas stream to produce an effluent having a temperature preferably in the range of from about 90° C. to about 150° C. Oxygen from an air subsystem (not shown) is also added to the process in step F. The oxygen is consumed by the reactions of process step G described below.

Process step G is an oxidation step wherein almost all of the remaining carbon monoxide in the effluent stream is converted to carbon dioxide. The processing is carried out in the presence of a catalyst for the oxidation of carbon monoxide. Two reactions occur in process step G: the desired oxidation of carbon monoxide (formula V) and the undesired oxidation of hydrogen (formula VI) as follows:
CO+½O2→CO2(V)
H2+½O2→H2O  (VI)

The preferential oxidation of carbon monoxide is favored by low temperatures. Since both reactions produce heat it may be advantageous to optionally include a cooling element such as a cooling coil, disposed within the process. The operating temperature of processs step G is preferably kept in the range of from about 90° C. to about 150° C. Process step G reduces the carbon monoxide level to preferably less than 50 ppm, which is a suitable level for use in fuel cells. Where a purification unit such as a pressure swing adsorption unit is disposed downstream of fuel processor102for removing CO and other impurities, the preferential oxidation reaction of step G can be omitted.

The reformate110exiting the fuel processor102is a hydrogen rich gas containing carbon dioxide and other constituents which may be present such as water, inert components (e.g., nitrogen, argon), residual hydrocarbon, etc. Product gas may be used as the feed220for a fuel cell or for other applications where a hydrogen rich feed stream is desired. Optionally, product gas may be sent on to further processing, for example, to remove the carbon dioxide, water or other components.

In some embodiments, the water gas shift of the ATR210employs non-pyrophoric shift catalyst(s), not shown. Non-pyrophoric shift catalysts are those that typically do not increase in temperature more than 200° C. when exposed to air after initial reduction. Non-pyrophoric shift catalysts may be based on precious metals, e.g., platinum or non-precious metals, e.g., copper. A commercially available non-pyrophoric shift catalyst suitable for use with the present invention is the SELECTRA SHIFT™ available from:
Engelhard Corporation 101 Wood Avenue Iselin, N.J. 08830 (732) 205-5000
However, other suitable non-pyrophoric shift catalysts may be used.

During reforming operations of ATR210, reformate and optionally additional steam are directed through the shift catalyst bed. Care should be taken to assure that liquid water does enter the shift bed as liquid water will coat and potentially degrade the catalyst. The shift reaction temperature is maintained at a temperature below about 300° C. The shift catalyst can withstand transient temperatures that exceed such temperatures for short periods of time of less than about 60 minutes, preferably less than about 45 minutes, and more preferably less than about 30 minutes. However, even during such transient periods, the reaction temperature should be less than about 400° C., preferably less than about 375° C. and more preferably less than about 350° C. Should the shift catalyst be subjected to over-temperature conditions for an extended period of time, the activity of the catalyst can irreversibly change to favor a methanation reaction.

The shift catalyst requires regeneration in order to maintain its activity. Regeneration of the shift catalyst can be achieved through oxidation. Specifically, the flow of steam to the reformer and to the shift catalyst bed is interrupted so that only air flows through the shift bed. After the reactor has been purged, oxidation of the shift catalyst bed is allowed to proceed. Regeneration of the catalyst bed through oxidation can be allowed to proceed more slowly at lower temperatures, e.g. by maintaining the shift bed at a temperature about 220° C. overnight, or may be driven more quickly at higher temperatures, e.g. by maintaining the shift bed at a temperature up to about 400° C. for about hour or more. During regeneration, care should be taken to ensure that neither liquid water nor steam flow through the shift catalyst bed.

FIG. 4conceptually depicts one particular implementation of the ATR210. The ATR210may be implemented with any suitable design known to the art. The ATR210comprises several stages401-405, including several heat exchangers409and electric heaters (not shown). The reformer shift bed412, i.e., the sections401-402, is functioning to perform the water gas shift reaction, discussed above relative toFIG. 3, which reduces CO concentration and increases H2production rate.

Each of the heat exchangers409receives temperature controlled coolant (not shown) from the thermal subsystem228, shown inFIG. 2, over the lines IN1-IN3, respectively, and returns it over the lines OUT1-OUT3, respectively. The flow rate for the coolant in each line is controlled by a respective variable speed (i.e., positive displacement) pump415-417. The pumps415-417are controlled by the automated control system106, shown inFIG. 1, by signals received over the lines A1-A3, respectively. In alternative embodiments, a single pump may supply coolant under pressure over the lines IN1-IN3and the flow rate may be controlled by flow control valves such as the flow control valve418. Those in the art having the benefit of this disclosure will appreciate that this figure is simplified by the omission of some elements not material to the practice of the invention in this particular embodiment. For example, the heat exchangers mentioned above and various inputs and outputs to the sections403-405have been omitted for the sake of clarity and so as not to obscure the present invention.

The shift bed412also includes a plurality of sensors T1-T4disposed therein. The precise number of temperature sensors Txis not material to the practice of the invention, although a greater number will typically provide a finer degree of control. In the illustrated embodiment, the temperature sensors T1-T4are thermocouples, but other types of temperature sensors may be used in alternative embodiments. The automated control system106uses the temperature sensors T1-T4to monitor actual temperatures at various locations within the shift bed412. Temperature detection points are selected based upon the structure of the cooling/heating system and should be selected so that the measured temperatures reflect true reaction temperatures rather than localized temperatures adjacent the heat exchange coils409.

Note that the temperature sensors T1and T2both measure temperature near the same heat exchanger409in a detail that is implementation specific. That particular heat exchanger409includes only a single coolant input IN1. Most of the temperature sensors T1-T4measure temperature downstream from a catalyst bed section containing a heat exchanger409. T1is supposed to read the temperature immediately downstream from the uppermost catalyst bed (not shown). However, during installation and shipping the bed can shift and settle so that T1is measuring an air temperature rather than a bed or reaction temperature. Thus, a second sensor T2is added to monitor the upper section401of the ATR210. When T1and T2are sensing different temperatures, the control system106takes the higher of the two temperatures. Typically, there usually is only a minor difference between the two temperatures.

Preheating and water cooling maintain the temperature in the shift bed412within a desired reaction temperature range. In order to achieve this objective, in an enlarged shift reactor, multiple heat exchange coils409may provide localized temperature control. In the illustrated embodiment, the elongated shift bed412utilizes three different heat exchange coils409for controlling the temperature of the shift bed412. The reaction temperature control strategy varies as a combination result of H2production rate, shift reaction stage, shift bed vertical temperature gradient and the temperature detecting points in a manner described more fully below. A robust shift temperature control loop is developed for the reformer to generate stable and high quality H2product.

FIG. 5conceptually illustrates a control loop500employed by the illustrated embodiment in accordance with the present invention. The settings for each of the variable speed pumps415-417is controlled by a respective control loop500. The control technique of the present invention employs, in the illustrated embodiment, the complete system modeling effect (the reformer as a whole, including ATR section, ZnO section, shift section, production rate, etc.), develops a dynamic PID control loop to the plant response, and testing data are used to compensate the model offset to improve the robustness of the controller.

More particularly, system modeling takes into account the target hydrogen production rate based upon current flow rates, upstream temperature profiles, reaction stage and shift bed temperature gradient due to heat loss and exothermal reaction effect. A system model for each section of the shift bed can be generated from reactions and conditions upstream, the geometries of the reactor(s), the feed to that section of the bed, and the shift catalyst(s) used etc. Various modeling techniques of this type are known to the art, and any suitable modeling technique may be employed. The system modeling is used to generate set points to be used for the temperature control. These set points include the predicted reformate composition, flow rate and temperature that will be entering a particular shift bed section. Thus, the system modeling generates a group of setpoints for the temperatures measured by the temperature sensors T1-T4. The system modeling also produces a set of results correlating, for example, the temperatures that may be measured by the temperature sensors T1-T4and the H2production rate of the ATR210.

More particularly, the model (not shown) used by the illustrated embodiment was developed using Aspen Plus and Aspen Custom Modeler. These software packages are commercially available from:
Aspen Technology, Inc. Ten Canal Park Cambridge, Mass. 02141-2201USA Phone: +1-617-949-1000Fax: +1-617-949-1030email: info@aspentech.com
However, other suitable modeling software known to the art may be employed in alternative embodiments.

The model has both steady-state and dynamic capabilities. The performance of the fuel processor102is estimated by the model from thermodynamic parameters that result in a desired state at the given temperature and pressure. Reaction conversions and compositions are determined from either kinetic data available in literature for such typical reactions or estimated from models based on experiments conducted in the laboratory for specific reactions. The desired H2purity and flow rate for the reformate110are specified and the model calculates natural gas flow, air flow (calculated back from the optimum O2/C ratio), and water flow (calculated back from the optimum Steam/Carbon ratio).

The resulting temperature of the ATR210is calculated as the adiabatic temperature rise resulting from minimizing the free energy of the ATR reaction. The composition of reformats is determined by the model (from thermodynamic and reaction parameter estimations). Using this composition, the model then calculates the desired speed needed for the end use from empirical correlations.

FIG. 6illustrates one particular embodiment of a method600practiced in accordance with another aspect of the present invention. More particularly, the method600is a method for use in controlling the reaction temperature of a fuel processor, i.e., the temperature in the shift bed412, shown inFIG. 4, of the ATR210, first shown inFIG. 2, of the fuel processor102, first shown inFIG. 1. The method600is for the control of a temperature in a single location, e.g., the temperature measured by the temperature sensor T1. However, the method600can be applied in serial or in parallel to control the temperature in a plurality of locations throughout the shift bed412or elsewhere in the ATR210. Application of the method600will be illustrated in the context of the control loop500, shown inFIG. 5. However, alternative embodiments may implement the method600using control loops of alternative design.

The method600begins by determining (at603) a first component503for a setting adjustment506for an actuator governing a measured temperature509in a reaction section of a reactor from the measured temperature509and a setpoint512for the measured temperature. The setpoint512is determined as a part of the modeled results discussed above. The measured temperature509is the temperature measured by the temperature sensor Txat the point of interest in the shift bed412, shown inFIG. 4, at which the temperature sensor Txis disposed. In the illustrated embodiment, the difference515between the setpoint512and the measured temperature509is input to a proportional-integral-derivative (“PID”) controller518, such as is known in the art. The output of the PID controller518is the first component503.

The method600also determines (at606) a second component521for the setting adjustment506from a H2production rate524for the fuel processor102. In the illustrated embodiment, at least selected portions of the modeled results previously discussed are tabulated in a form indexable by the H2production rate. Thus, the modeled results527may be, for instance, a look-up table wherein various setting adjustments for the actuator are indexed by the H2production rate to which they correlate. Note that the modeled results527are typically generate a priori by modeling the operation of the fuel processor102in a variety of operating scenarios to obtain this information. Note also that the determination of the first and second components503,521may be performed in parallel or in serial.

The method600then determines (at609) the setting adjustment506from the first and second components503,521. In the illustrated embodiment, the first and second components503,521are summed to obtain the setting adjustment506, although alternative embodiments may use more sophisticated techniques for the determination. The setting adjustment506is then signaled to the actuator over the line Ay. Note that the setting adjustment506may be 0, i.e., no change is needed because the measured temperature509suitable matches the setpoint512. However, at any given time, at least one of, and sometimes all of, the first component503, the second component521, and the setting adjustment506will be non-zero.

Note that, in some circumstances, the first and second components503,521could work in opposite directions with one telling a pump to increase flow and the other telling the pump to decrease flow. Thus, in the illustrated embodiment, the two components503,521are not given equal weight in controlling the coolant flow. Specifically, the H2production rate and the information from the look up table, i.e., the second component521, is the dominant component. The first component503that is derived from sensed temperatures509and the setpoints512, is used to fine tune the pump speed. By way of example, the second component521might instruct a given pump to operate at 50% of capacity, while the first component focuses on the error and may adjust the pump speed by ±5% of capacity.

The method600, shown inFIG. 6, and the control500, shown inFIG. 5, are implemented as parts of the automated control system106in software in the form of a control application residing on the computing device108, both shown inFIG. 1. The automated control system106, as a whole, is largely implemented in software on a computing apparatus, such as the rack-mounted computing apparatus700illustrated inFIG. 7AandFIG. 7B. Note that the computing apparatus700need not be rack-mounted in all embodiments. Indeed, this aspect of any given implementation is not material to the practice of the invention. The computing apparatus700may be implemented as a desktop personal computer, a workstation, a notebook or laptop computer, an embedded processor, or the like.

The computing apparatus700illustrated inFIG. 7AandFIG. 7Bincludes a processor705communicating with storage710over a bus system715. The storage710may include a hard disk and/or random access memory (“RAM”) and/or removable storage such as a floppy magnetic disk717and an optical disk720. The storage710is encoded with a data structure725storing the data set acquired as discussed above, an operating system730, user interface software735, and an application765. The user interface software735, in conjunction with a display740, implements a user interface745. The user interface745may include peripheral I/O devices such as a key pad or keyboard750, a mouse755, or a joystick760. The processor705runs under the control of the operating system730, which may be practically any operating system known to the art. The application765is invoked by the operating system730upon power up, reset, or both, depending on the implementation of the operating system730. In the illustrated embodiment, the application765includes the control system106illustrated inFIG. 1.

Thus, at least some aspects of the present invention will typically be implemented as software on an appropriately programmed computing device, e.g., the computing apparatus700inFIG. 7AandFIG. 7B. The instructions may be encoded on, for example, the storage710, the floppy disk717, and/or the optical disk720. The present invention therefore includes, in one aspect, a computing apparatus programmed to perform the method of the invention. In another aspect, the invention includes a program storage device encoded with instructions that, when executed by a computing apparatus, perform the method of the invention.

Some portions of the detailed descriptions herein may consequently be presented in terms of a software-implemented process involving symbolic representations of operations on data bits within a memory in a computing system or a computing device. These descriptions and representations are the means used by those in the art to most effectively convey the substance of their work to others skilled in the art. The process and operation require physical manipulations of physical quantities. Usually, 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 quantifies. 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 (electronic, magnetic, or optical) quantities within some electronic device's storage into other data similarly represented as physical quantities within the storage, or in transmission or display devices. Exemplary of the terms denoting such a description are, without limitation, the terms “processing,” “computing,” “calculating,” “determining,” “displaying,” and the like.

Thus, returning toFIG. 4, the ATR210includes a plurality of temperature sensors T1-T4disposed within the shift bed412at points of particular interest. The control application765residing in the storage710of the computing apparatus700, shown inFIG. 7A-FIG.7B, includes a control loop500, shown inFIG. 5, for each of the sensors T1-T4. The data structure725includes the modeled results comprising at least the setpoints512for the sensors T1-T4and the second components521and their correlated H2production rates524.

The shift reaction temperature in the shift bed412, shown inFIG. 4, is usually a constant number at a certain given reaction stage. The system model (not shown) generates an amount of coolant needed for each section401,402of the shift bed412based upon the current reformer feeding rate and what is occurring upstream from that section of the shift bed412. The control loops500use these numbers as the targeting set points512. The temperature sensors T1-T4, positioned in different locations of the shift bed412, provide feedback of the reaction temperature during steady-state operations, to the control loops500. The reaction temperature feedback forms a closed loop control on the desired temperatures, i.e., the setpoints512. The dynamic PID controllers518in the control loops500automatically adjust the plant response time according to the dynamic change of the shift bed temperatures feedback. As shown inFIG. 8, the controller produces stable reaction temperatures across each section of the bed and could be programmed to provide a uniform temperature across the bed.

FIG. 9is a block diagram of a filtering technique in accordance with the present invention used to filter the temperature measurements1009, shown inFIG. 10. As is shown inFIG. 9, the filter900comprises a store903of at least one historical sensor measurement; a store906of potential cut-off frequencies, and a filter909having a dynamic cut-off frequency. The filter909may be a low pass filter, a high pass filter, or a band pass filter, depending on the implementation. Each potential cut-off frequency in the store906is associated with a respective potential difference912between a sensor measurement915and the stored historical sensor measurement918. The filter909has a cut-off frequency921dynamically selected from the stored potential cut-off frequencies906on the basis of a difference912between the stored historical sensor measurement918and the current sensor measurement915. In operation, the filter900first determines a difference912between a current sensor measurement915and a historical sensor measurement918. The filter900then dynamically selects a cut-off frequency921for a filter909for the current sensor measurement915from the difference912to obtain a filtered output927.

More particularly, the current sensor measurement915is sampled into the data acquisition system every 100 milliseconds and converted to a digital format by the analog-to-digital (“A/D”) converter930. A preliminary low-pass filter933with a fast response characteristic preliminarily filters the current sensor measurement915. The preliminary low-pass filter933employs a constant cut-off frequency to preliminarily filter certain frequencies that will be known to be noise in the particular implementation. The preliminary low-pass filter933is optional from the standpoint of the invention since, in some embodiments, the sensors (not shown) through which the measurements are taken may be of sufficient quality that they produce minimally low levels of noise. Similarly, the context in which the invention is employed may be such that environmental factors might not introduce significant levels of noise. However, in general, a preliminary low-pass filter933will be desirable in most applications.

A few historic sampling points in the store903are compared with the current sensor measurement915to determine the rate of change of this particular process variable represented by the current sensor measurement915. More particularly, as will be discussed further below, the historical sensor measurement918is actually an average of four past sensor measurements915. Each filtered sample of the sensor measurement915, is returned to the historical sensor measurement store903through a feedback936to populate the store903. The cut-off frequency store906containing the rate of changes versus cut-off frequencies is used to set the cut-off frequency921of the low pass filter909.

In this particular embodiment, the decision making process of the cut-off frequency is updated during each sampling period to avoid filtering out the true sensor signal. More particularly, as those in the art having the benefit of this disclosure will appreciate, the filtering technique is applied over time through multiple iterations as the current sensor measurement915is sampled. In each iteration, the historical sensor measurement918is an average of four past sensor measurement915. Periodically, a sensor measurement915for the current iteration is transmitted to the store to take the place of the sensor measurement915, which is then purged. In this way, when the process parameter represented by the current sensor measurement915is in a steady state, high frequency signals, which are apparently the noises, are filtered out. When the process parameter is in a dynamic change state, the cut-off frequency921is shifted up to avoid filtering out the true signal.

Note that, in the embodiment ofFIG. 9, the cut-off frequency921is a piecewise linear function of the difference912. In the illustrated embodiment, if the difference (d) is 3%≦d≦10% (full scale), then the cutoff frequency is set to 0.01-0.2 (normalized, Z-domain). In such an embodiment, the precise parameters of the relationship will be a function of implementation specific considerations, such as the type of process being monitored and how rapidly it is expected to change. In the illustrated embodiment, which the monitored process is a water-gas shift reaction in an autothermal reformer, which is not expected to change rapidly during normal or steady state operations. Some alternative embodiments might even choose to use some other type of relationship.

FIG. 10illustrates the functional components of the filter900inFIG. 9. More particularly,FIG. 10illustrates in a block diagram the transfer function1000of the 1storder filter900inFIG. 9in the z-domain. Note that, in this embodiment, there are four flip-flops1003. Each stores the difference between a respective historical sensor measurements918(only one indicated) and the current sensor measurement915. The absolute values1006(only one indicated) of the differences912(only one indicated) are then averaged and the averaged historical sensor measurement918is used to obtain the cut-off frequency921from the cut-off frequency look-up table906. Note also that the delays1009(only one indicated) for the flip-flops1003differ, and that, collectively, they store the four historical sensor measurements918.

Still referring toFIG. 10, because the filter900is taking readings so fast, the historical sensor measurements915in the store903should not be too close to the current sensor measurement915. The delays1009are shown in the form of Z−x, where x is the number of readings preceding the current reading. Thus, Z−3indicates the third sensor measurement915preceding the current sensor measurement915, Z−10indicates the tenth sensor measurement915preceding the current sensor measurement915, etc. The value of x is arbitrary but should be large enough so that the historical sensor measurement915is not too close to the current sensor measurement915.

Returning toFIG. 1, in operation, the apparatus100must first be initialized, or started-up. In general terms, the fuel processor102start-up involves lighting off oxidizer214, bringing the oxidizer214to operating conditions lighting off the ATR210and then bringing the ATR210to operating conditions. The oxidizer214light off is the state of the oxidizer214when there is an ongoing catalyzed reaction between the fuel and air in a desired temperature range. Similarly, the ATR210light off is the state of the ATR210when it is considered to have an ongoing catalyzed reaction between the components of the process feed stream220received from the oxidizer214. The start-up procedure will largely be implementation specific, depending on the design of the ATR210and the oxidizer214and their inter-relationship.

Once the fuel processor102is started-up, it goes into its operational cycle. The operational cycle comprises steady-state operations for the process flow300, discussed above relative toFIG. 3. It is during the operational cycle that the method600, shown inFIG. 6, is implemented by the automated control system106. The temperature sensors T1-T4continuously sense their respective temperatures, but the control loop500, shown inFIG. 5, is only implemented during the operational cycle. The method600is performed for each of the temperatures measured by the temperature sensors T1-T4in parallel. The method600may be performed continuously or at periodic intervals, depending on the implementation.

Eventually, the operational cycle ends, and the fuel processor102is shutdown. The shutdown may be planned, as in the case for maintenance, or unplanned, as when a shutdown error condition occurs. Either way, a part of the shutdown is the termination of method600, shown inFIG. 6. The oxidizer214and ATR210, respectively, are, in general terms, purged and cooled. On transition to the shutdown state, the air subsystem226, the water subsystem224, and the thermal subsystem228are providing air218, water216, and thermal control to the oxidizer214and the ATR210. As with the start-up, the shutdown procedure will largely be implementation specific, depending on the design of the ATR210and the oxidizer214and their inter-relationship. In the illustrated embodiment, the ATR210is first purged and shutdown, followed by the oxidizer214purge and shutdown.