JP4912742B2 - Hydrogen generator and fuel cell system - Google Patents

Description

  The present invention relates to a hydrogen generator and a fuel cell system, and more particularly to an improvement in a technique for removing carbon monoxide gas from a gas of a hydrogen generator.

  A conventional hydrogen generator includes a reformer for a reforming reaction, a shifter for a shift reaction, and a selective oxidizer for a selective oxidation reaction. A hydrogen-rich hydrogen-containing gas in which carbon oxide gas (CO) is reduced to a predetermined concentration or less is generated.

  The reformer has, for example, a reforming catalyst body filled with a reforming catalyst made of a noble metal such as ruthenium (Ru), platinum (Pt), or Rh (rhodium), and is composed of at least carbon and hydrogen. A hydrogen-rich hydrogen-containing gas is generated from a raw material gas containing an organic compound and steam by a steam reforming reaction using a reforming catalyst.

  The shift device has a shift catalyst body filled with a shift catalyst made of a noble metal such as Pt, a copper (Cu) -zinc (Zn) -based material, or an iron (Fe) -chromium (Cr) -based material. CO in the contained gas is removed to a concentration level of about 1% by the shift reaction using the shift catalyst.

  The selective oxidizer has a selective oxidation catalyst body filled with a selective oxidation catalyst made of a noble metal such as Ru or Pt, and thereby in a hydrogen-containing gas (hereinafter referred to as “post-transformation gas”) discharged from the shift converter. Is previously mixed with air and then removed to a level below a predetermined CO concentration (for example, 20 ppm or less) by an oxidation reaction using a selective oxidation catalyst.

  A method for detecting a catalyst state in the hydrogen generator and a countermeasure for catalyst deterioration have already been proposed so that CO in the gas generated by such a hydrogen generator can be appropriately removed.

  For example, there is a hydrogen generator that introduces a technique for detecting an appropriate state of the shift catalyst based on the temperature of the shift catalyst body. More specifically, based on the temperature of the shift catalyst body, the CO concentration in the post-shift gas is grasped, and based on the CO concentration and the selective oxidation catalyst body temperature, There is a hydrogen generator configured to increase the air for oxidation reaction and appropriately remove CO by a selective oxidizer by expecting an increase in CO concentration in the gas (see Patent Document 1). Further, a decrease in the catalytic activity of the shift catalyst body is detected based on the temperature of the shift catalyst body, and as one countermeasure against this, increasing the amount of water supplied to the shift catalyst body is cited (see Patent Document 2).

Further, a hydrogen generation apparatus is already provided that can adjust the air cooling operation by a cooling fan toward the selective oxidizer so that the temperature of the selective oxidation catalyst body becomes an appropriate temperature based on the temperature of the selective oxidation catalyst body (patent). Reference 3).
JP 2003-277011 A JP 2003-217636 A JP 2003-212509 A

  In the hydrogen generators described in the above Patent Documents 1 to 3, as described below, there is a lack of appropriate consideration for a decrease in the catalytic activity (reactivity) of both the reforming catalyst body and the shift catalyst body. The present inventors are thinking.

  For example, as the total operation time of the hydrogen generator is prolonged and the total number of operations for starting or stopping the hydrogen generator is increased, sintering (aggregation) of the main reaction part (upstream end part) that becomes high temperature in the shift catalyst body, First, the catalytic activity of the shift catalyst body is reduced by various factors such as water wetting at the upstream end of the shift catalyst body and heat shock (for example, thermal damage due to sudden change in temperature of the shift catalyst body). It becomes biased and manifests at the upstream end of the medium.

  As a result, the main reaction portion of the shift catalyst body is likely to gradually transition from the upstream portion to the downstream portion of the shift catalyst body with the passage of time due to the uneven distribution of the catalytic activity reduction region.

  And if the main reaction part of a shift catalyst body changes with progress of time, it is thought that the correlation between the temperature of a shift catalyst body and the amount of CO in gas after shift is also changing with progress of time. For this reason, when transition of the catalytic activity of such a shift catalyst body is assumed, if the temperature detection location of the shift catalyst body is not appropriate, there is a high possibility that the amount of CO in the gas after shift will be difficult to predict. .

  Furthermore, there is a possibility that a reduction in the catalytic activity of the reforming catalyst body and a reduction in the catalytic activity of the reforming catalyst body may be caused by prolonging the total operation time of the hydrogen generator and increasing the total number of operations.

  If the catalytic activity of the reforming catalyst body decreases, the CO amount in the hydrogen-containing gas, that is, the CO amount in the gas supplied to the shift catalyst body changes.

  Then, the correlation between the temperature of the shifter and the predicted amount of CO in the gas after the shift is shifted according to the state of the catalytic activity of the reforming catalyst body being lowered. The prediction becomes more complex and uncertain.

  On the other hand, in anticipation of a decrease in the catalytic activity of the reforming catalyst body or the shift catalyst body, the air to the selective oxidizer can be used to cope with CO in the post-shift gas that is expected to increase due to this decrease. It is envisaged that the next best measure is to supply a large amount in advance.

  However, if such a measure is adopted, in the initial state of the hydrogen generator (the stage in which the catalytic activity of the reforming catalyst body and the shift catalyst body has not been lowered), it is inevitably necessary for the amount of CO in the gas after the shift. As a result, an excess amount of air is supplied, and excess oxygen gas after CO oxidation in the selective oxidizer may oxidize hydrogen gas coexisting with the oxygen gas. For this reason, the hydrogen gas generated by the reforming reaction of the reformer is extinguished by the oxidation reaction of the surplus oxygen gas in the initial state of the hydrogen generator, and there is a disadvantage that the generation efficiency of hydrogen gas is reduced.

  The present invention has been made in view of such circumstances, and a hydrogen generator capable of accurately calculating an estimated value of CO concentration in the gas after the shift when the catalytic activity of the shift catalyst and the reformed catalyst is lowered. The purpose is to provide. In particular, the present invention relates to hydrogen capable of supplying CO selective oxidation air for removing CO in the gas after the modification to the selective oxidizer without excess or deficiency when the catalytic activity of the modification catalyst and the reforming catalyst is lowered. An object is to provide a generation device.

In order to solve the above problems, a hydrogen generator according to the present invention includes a reformer that generates a hydrogen-containing gas by a reforming reaction using a raw material gas containing an organic compound composed of at least carbon and hydrogen, A hydrogen-containing gas flowing through the shift catalyst body to reduce the carbon monoxide gas in the hydrogen-containing gas by a shift reaction; and the temperature of the upstream portion of the shift catalyst body in the hydrogen-containing gas flow direction. Air is supplied to the hydrogen-containing gas discharged from the upstream temperature detector for detecting, the downstream temperature detector for detecting the temperature of the downstream portion of the shift catalyst body in the flow direction of the hydrogen-containing gas. An air supply device, a selective oxidizer for reducing carbon monoxide gas in the hydrogen-containing gas discharged from the transformer by an oxidation reaction with the air, and a control device, System Device, the upstream temperature detector to obtain a change in a more sensed Ru temperature change and said downstream temperature sensor in the temperature detected by, corresponding to each of the previous SL temperature change, from the transformer The carbon monoxide gas concentration increase contribution in the discharged hydrogen-containing gas is estimated, and the amount of the air supplied from the air supply unit is calculated based on the carbon monoxide gas concentration increase contribution and the flow rate of the source gas. It is a device that controls the flow rate.

  The temperature detected by the upstream temperature detector is information reflecting, for example, a decrease in catalyst activity due to the reforming catalyst body. For this reason, according to the above configuration, since the temperature due to the decrease in the catalytic activity can be separated and grasped for each of the reforming catalyst body and the shift catalyst body, the gas after the shift is reduced when the catalytic activity of the shift catalyst body and the reforming catalyst body is decreased. It is expected that the estimated CO concentration in the medium can be estimated more accurately.

  As a result, when the catalytic activity of the shift catalyst body and the reforming catalyst body is lowered, the CO selective oxidation air for removing CO in the gas after the shift can be supplied to the selective oxidizer without excess or deficiency.

The control device acquires at least one of the total operation time information and the total operation number information of the hydrogen generator, and based on the total operation time information and / or the total operation number information, It is used to control the flow rate of air not good. Thus, CO concentration estimated value calculating more appropriately performed Runode transformer after gas for selective oxidation device, the CO selective oxidation air to remove CO transformer after the gas just proportion can be supplied Become .

  The fuel cell system according to the present invention includes a hydrogen generator, an oxidant gas supplier, a reducing agent gas supplied by the hydrogen generator, and an oxidant supplied by the oxidant gas supplier. And a fuel cell that generates electricity using gas.

  According to the present invention, when the catalytic activity of the shift catalyst body and the reforming catalyst body is lowered, a hydrogen generator capable of accurately calculating the estimated CO concentration in the gas after the shift can be obtained. When the catalytic activity of the catalyst body is lowered, a hydrogen generator capable of supplying CO selective oxidation air for removing CO in the gas after the transformation without excess or deficiency to the selective oxidizer is obtained.

  Hereinafter, preferred embodiments will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a hydrogen generator according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a hydrogen generator 100 mainly includes a reformer 11 having a reforming catalyst body (not shown) for reforming reaction, and a shifter 13 having a shift catalyst body 12 for shift reaction. And a selective oxidizer 14 having a selective oxidation catalyst body (not shown) for oxidation reaction.

  The reformer 11 includes a source gas supply unit 15 for adjusting the flow rate of a source gas containing an organic compound composed of at least carbon and hydrogen, and supplying the source gas to the reformer 11; A reforming water supplier 16 for adjusting the flow rate and supplying it to the reformer 11 and a burner 17 for heating the reforming catalyst body inside the reformer 11 to an appropriate temperature are provided. Yes.

  Since the raw material gas supply device 15 and the reforming water supply device 6 are each configured to be able to adjust the flow rate of the supply (raw material gas or water), these supply devices 15 and 16 are, for example, the supply material It may be a supply pump (driving means) capable of changing the discharge flow rate, and is a fluid mechanism that combines a supply source of a supply and a supply flow rate adjusting valve provided in a flow path downstream of the supply source. There may be.

  The shift converter 13 includes a shift catalyst body 12 and a gas flow path (not shown) for allowing the hydrogen-containing gas to flow through the shift catalyst body 12 inside the reaction vessel. An upstream temperature detector 18 (for example, a thermistor or a thermocouple) that directly contacts the upstream end of the shift catalyst body 12 (the hydrogen-containing gas inlet of the shift catalyst body 12) and directly detects the temperature, and the shift catalyst body 12 And a downstream temperature detector 19 (for example, a thermistor or a thermocouple) that directly detects this temperature in contact with the downstream end of the catalyst (gas outlet after the shift of the shift catalyst body 12).

  Thus, by obtaining the temperatures of the paired portions of the shift catalyst body 12, that is, the upstream end portion and the downstream end portion of the shift catalyst body 12, the CO concentration estimated value in the shift gas can be accurately calculated as will be described in detail later. become.

The selective oxidizer 14 includes a selective oxidant air supply device 22 (for example, a blower capable of changing the air amount or this blower capable of adjusting and supplying a predetermined amount of air to the transformed gas flowing toward the selective oxidizer 14. And a combined fluid mechanism of the air amount adjusting valve), and after this, the gas after the modification and the air are mixed, and then this mixed gas is sent to the selective oxidizer 14.

  Further, a gas outlet port 21 for discharging the gas that has passed through the selective oxidation catalyst body to the outside is disposed at an appropriate position of the selective oxidizer 14, and thereby generated by the hydrogen generator 100 and the CO concentration. The hydrogen-containing gas (hydrogen gas) reduced to a predetermined level or less can be discharged toward a hydrogen gas utilization device (for example, a fuel cell) via the gas outlet port 21.

The control device 20 is constituted by, for example, a microprocessor, and as shown by a dotted line in FIG. 1, the raw material gas supply device 15 and the reforming water supply device 16 and the selective oxidation air supply device 22 (hereinafter referred to as “supply device”) of the hydrogen generation device 100. ”) To control the operation of these feeders 15, 16, 22 .

For example, the control device 20 is also electrically connected to an upstream temperature detector 18 and a downstream temperature detector 19 for detecting the temperature of the shift catalyst body 12, and as will be described in detail later, a pair obtained by these detectors 18 and 19. Based on the data (a pair of temperatures), the operation control (air flow rate adjustment) of the selective oxidized air supply device 22 as the control target of the control device 20 is performed.

  Note that the control device in this specification refers to any of a control device group in which a plurality of control devices cooperate to control the overall operation of the hydrogen generator 100 and a single control device in which these control devices are integrated. Also means. Therefore, this control device 20 may also serve as control of the overall operation of the hydrogen generation device 100, and each device (for example, the reformer 11) in the hydrogen generation device 100 is controlled by another control device (not shown). The temperature control and gas flow rate adjustment may be executed.

  Next, a series of hydrogen generation operation examples by the hydrogen generator 100 will be described.

  However, since the gas generation here is based on a known reaction, only a brief description will be given.

  The reformed water supplied from the reformed water supply unit 16 to the reformer 11 is evaporated by heating of the burner 17 to become steam, and this steam is mixed with the source gas supplied from the source gas supplier 15. And supplied to the reforming catalyst body of the reformer 11.

The reforming catalyst body is heated to a high temperature suitable for the reforming reaction (here, 600 to 700 ° C.) by the burner 17, whereby hydrogen-containing gas (precisely, H ₂ gas, CO and CO) is generated from the raw material gas and water vapor. The reforming reaction of generating a mixed gas such as _two gases proceeds by the catalytic action of the reforming catalyst body.

Further, CO in the hydrogen-containing gas is removed by performing a shift reaction of CO in the hydrogen-containing gas with water vapor (H ₂ O) by a shift reaction based on the catalytic action of the shift catalyst body 12 of the shift converter 13. . The gas after CO removal by the shift catalyst body 12 is supplied to the selective oxidizer 14 as the shift-after gas.

  This transformed gas is mixed with the air supplied from the selective oxidation air supplier 22 and then supplied to the selective oxidizer 14. By the oxidation reaction based on the catalytic action of the selective oxidation catalyst body of the selective oxidizer 14, After the modification, CO in the gas is further removed to a lower concentration (for example, 20 ppm or less).

  In this way, the hydrogen generator 100 discharges the hydrogen-rich product gas (hydrogen-containing gas) from which CO is almost removed through the gas outlet port 21 provided in the selective oxidizer 14 to the outside.

  Next, the operation for calculating the estimated CO concentration in the post-transform gas based on the pair of temperatures in the shift catalyst body 12 that characterizes this embodiment will be described.

  First, the relationship between the estimated value of the CO concentration in the post-transformation gas and the temperature of the shift catalyst body was verified using simple experiments and analysis simulations.

  FIG. 2 is a graph showing the correlation between the temperature of the shift catalyst body (horizontal axis) and the CO concentration (vertical axis) using the number of times the water of the shift catalyst body is wet as a parameter. The result of having verified the dependence of the catalyst activity (reactivity) by the frequency | count of water wetting is shown.

<Outline of simple experiment>
Approximately 6.5 ml of a copper (Cu) -zinc (Zn) -based catalyst as a cylindrical (rod-shaped) catalyst is packed in a stainless steel tube (single tube) having a diameter of about 1 inch.

  Then, a gas corresponding to the hydrogen-containing gas discharged from the reformer 11 (more specifically, containing 10% of CO) is sent from one end of the single tube after charging the shift catalyst. Further, the CO concentration in the dry gas from which moisture has been removed after passing through this single tube is detected by a gas chromatograph installed at the other end of the single tube.

Here, as shown in FIG. 2, a single tube filled with a shift catalyst body that is not immersed in water (referred to as “initial single tube” in FIG. 2), and a shift catalyst body that has been immersed once in water is charged. A single tube (refers to “single water once single tube” in FIG. 2) and a single tube filled with a modified catalyst body after being immersed twice in water (refers to “double water wet single tube” in FIG. 2) Between the temperature of the shift catalyst bodies in these single tubes (temperatures in steps of about 10 ° C. within the range of about 165 ° C. to 245 ° C.) and the CO concentration detected by the gas chromatograph Was requested.
<Results of simple experiment>
According to FIG. 2, the catalyst temperature of the shift catalyst body is appropriately changed in the range of about 165 ° C. to 245 ° C., and the CO concentration measured by gas chromatography is increased every time the number of times of water wetting is increased compared to the initial single tube. It shows an increasing trend.

  For example, when the temperature of the shift catalyst body is set to 200 ° C., the CO concentration in the gas passing through the initial single pipe is reduced to about 0.5%, compared with the gas passing through the single pipe once wet. The CO concentration increases, for example, the CO concentration in the gas is about 1.2%, the CO concentration in the gas that has passed through the single tube twice wet is about 1.5%. In this way, it was confirmed that the catalytic activity of the shift catalyst body was reduced by increasing the number of times the shift catalyst body was wetted with water.

Here, the behavior of the catalytic activity decrease due to the wetness of the shift catalyst body was verified by a simple experiment, but in an actual hydrogen generator, the local temperature depending on the conditions of starting, operating and stopping the hydrogen generator It is estimated that the catalyst activity of the shift catalyst body will decrease due to the rise, etc., depending on various factors such as sintering, heat shock and carbon deposition of each catalyst body, as well as when the shift catalyst body gets wet. Is done.
<Transition of the main reaction part of the shift catalyst body due to a decrease in the catalytic activity of the shift catalyst body>
The shift reaction by the shift catalyst body is an exothermic reaction based on the following formula (1).

CO + H ₂ O → H ₂ + CO ₂ -41.2 kJ / mol (1)
Here, in the case where the catalytic activity of a part of the shift catalyst body is lowered due to some factor and the case where it is not, the CO concentration in the gas passing through this part and flowing downstream is understood from the result of the above simple experiment. It is thought to change as it is done.

  For example, if it is assumed that the upstream end of the gas flow of the shift catalyst body has caused the catalytic activity to decrease by two times of water wetting, the CO concentration in the gas passing through the upstream end and flowing downstream is In the state where the temperature of the medium is kept at 200 ° C., it is expected to increase by about 1.0% from 0.5% (catalytic activity unreduced) to 1.5%.

  Then, when the catalytic activity of the upstream end portion of the shift catalyst body is reduced in this way, the CO corresponding to the CO concentration difference (1.0%) between the two is equal to the upstream end portion based on the formula (1). Without contributing to the exothermic reaction, it passes through the upstream end portion of the shift catalyst body as it is and flows downstream. As a result, the temperature of the upstream end portion of the shift catalyst body is lower than that when the catalytic activity does not decrease. Lower. On the other hand, the downstream temperature of the shift catalyst body becomes higher than the case where the catalytic activity does not decrease due to an increase in shift reaction heat resulting from the high concentration of CO. That is, it is estimated that the temperature at the upstream end portion of the shift catalyst body decreases while the temperature at the downstream side of the shift catalyst body increases.

  In this way, the main reaction part of the shift catalyst body shifts when the catalytic activity at the upstream end of the shift catalyst body decreases compared to the case where it does not.

  From the examination contents by the simple experiment described above, it is assumed that the temperature of the gas supplied to the shift catalyst body and the CO concentration in the gas are constant (however, this assumption is based on the hydrogen generator 100 of FIG. 1). In the situation where the converter 13 is incorporated into the converter catalyst, it is highly possible that the converter catalyst 13 does not hold as will be described later. By detecting the temperature in the vicinity of the gas outlet with a temperature detector such as a thermocouple or thermistor, a decrease in the catalytic activity of the shift catalyst body can be predicted based on such temperature, and as a result, the CO concentration in the gas after shift The inventors consider that the estimated value can be calculated appropriately.

Next, in order to ascertain the validity of the calculation of the estimated CO concentration in the post-transformation gas based on the temperature of the shift catalyst body, whether the shift catalyst body has a reduced catalytic activity or not. The behavior of the temperature distribution and the behavior of the CO concentration distribution were determined by analytical simulation.
<Analysis model and input conditions of analysis model>
An analysis target (analysis mesh area) for a cylindrical shift catalyst body, assuming that a cylindrical space (length: 100 mm) is filled with a copper (Cu) -zinc (Zn) -based material (change catalyst), is a computer. Modeled above.

  Here, all analysis meshes assuming the presence of a copper (Cu) -zinc (Zn) -based material as an analysis model when the catalytic activity of the shift catalyst body does not decrease (hereinafter referred to as “normal shift catalyst body model”) In addition, the reaction rate of the copper (Cu) -zinc (Zn) -based material is input.

  Further, as an analysis model when the catalytic activity of the shift catalyst body is reduced (hereinafter referred to as “change catalyst body deterioration model”), an analysis mesh that assumes the presence of a copper (Cu) -zinc (Zn) -based material is used. For the upstream analysis mesh, the frequency factor of the Arrhenius equation for predicting the chemical reaction rate is 1/3 so that the reactivity of the copper (Cu) -zinc (Zn) -based material becomes 1/3. Is set to Thereby, an analytical model in which the catalytic activity is intentionally reduced can be obtained.

  However, this analysis model has an analysis mesh region (length: 18 mm) corresponding to an alumina layer that does not contribute to the shift reaction on the upstream side of the shift catalyst for the purpose of reproducing an actual product on a computer as much as possible. An analysis mesh is formed by modeling a region (length: 25 mm) constituting the space portion on the upstream side, and boundary conditions are set using the upstream end portion of the space portion as a reference end of the transformer 13.

  Note that the catalytic activity of the reforming catalyst body included in the reformer 11 as well as the shift catalyst body 12 may decrease due to an increase in the total number of operations and / or the total operation time of the hydrogen generator 100. If the catalytic activity of the reforming catalyst body decreases, the reforming catalyst body outlet temperature decreases, and the CO concentration in the reformed gas decreases. That is, the conditions of the reformed gas supplied to the shift catalyst body 12 vary depending on the state of the reformed catalyst body. Therefore, both in the initial stage where the catalytic activity of the reforming catalyst body has not decreased (hereinafter referred to as “no reforming catalyst deterioration”) and in the case where it has deteriorated (hereinafter referred to as “having reforming catalyst deterioration”). The reformed gas component and the flow rate corresponding to the above are input as boundary conditions at the reference end of the shift catalyst body. However, since the gas temperature at the reference end of the shift catalyst body is controlled to a constant value of about 250 ° C. by the temperature control means in the hydrogen generator, the gas temperature boundary condition at the reference end is analyzed to be a constant value of 250 ° C. It was.

Furthermore, appropriate gas property conditions and boundary conditions other than the above are input so that the gas composition assuming the rated operation of the actual hydrogen generator can be reproduced.
<Analysis simulation results>
FIG. 3 is a diagram showing the distribution of the temperature (° C.) inside the shift catalyst body of the shift catalyst body normal model and the shift catalyst body deterioration model with respect to no reforming catalyst deterioration and with reforming catalyst deterioration. The horizontal axis is the distance along the gas flow direction from the reference end of the gas (alumina part is 25 mm to 43 mm, the shift catalyst body part is 43 mm to 143 mm), and the temperature of the shift catalyst body is the vertical axis, and analysis by combination of each catalyst body model It is the figure which showed the simulation result.

  FIG. 4 is a diagram showing the distribution of CO molar concentration (%) in the product gas in the analysis simulation of FIG. The horizontal axis represents the distance along the gas flow direction from the reference end of the transformer 13, and the vertical axis represents the CO molar concentration.

  That is, in FIG. 3 (or FIG. 4), the temperature distribution (or CO molar concentration distribution) (shown by a thick solid line) inside the shift catalyst body of the shift catalyst body normal model for the unconditional condition of the reforming catalyst, and the reforming catalyst The temperature distribution (or CO molar concentration distribution) inside the shift catalyst body of the shift catalyst body deterioration model for unconditional deterioration (shown by a thick dotted line), and the shift catalyst body of the shift catalyst normal model for the reforming catalyst deterioration condition Internal temperature distribution (or CO molar concentration distribution) (illustrated by a thick one-dot chain line) and internal temperature distribution (or CO molar concentration distribution) of the modified catalyst deterioration model of the reforming catalyst deterioration model for the condition of reforming catalyst deterioration (thick) (Illustrated by a two-dot chain line).

  When the temperature distributions of the normal model of the shift catalyst and the deterioration model are compared under the condition that the reforming catalyst deterioration is unconditional or the condition of the reforming catalyst deterioration is shown in FIG. It can be seen that the temperature of the model is higher than the temperature of the deterioration model. This is because the main reaction part is located in the vicinity of the upstream end in the normal model of the metamorphic catalyst body, so the effect of the temperature rise due to the catalytic reaction heat (exothermic reaction) in this part is also affected by the heat conduction in the alumina layer. To reduce the temperature drop in the alumina layer, and the reactivity of the catalyst with respect to the temperature of the normal model shift catalyst body is higher than that of the deterioration model catalyst. This is due to the fact that the heat of catalytic reaction is higher than that of the degradation model.

  According to the CO concentration distribution of FIG. 4, first, the CO concentration at the reference end of the transformer 13 varies depending on whether the reforming catalyst body normal model and the deterioration model are unconditional and deterioration conditions of the reforming catalyst. This is considered to be a phenomenon that occurs due to the deterioration of the reactivity with respect to the catalyst temperature as the reforming catalyst deteriorates and the main reaction position of the reforming catalyst body moving downstream. That is, since the reforming reaction is an endothermic reaction, the temperature at the outlet of the reforming catalyst body is lowered if the main reaction position exists on the downstream side of the reforming catalyst body. The post-reforming gas composition at the outlet of the reforming catalyst body is substantially determined by the temperature at the outlet of the reforming catalyst body. Therefore, the CO concentration in the post-reforming gas becomes lower as the reforming catalyst body deteriorates. As a result, the CO concentration in the reformed gas supplied to the transformer 13 differs depending on whether the reforming catalyst body has deteriorated. Therefore, not only depends on whether the shift catalyst body is normal or deteriorated, but the CO concentration in the shift gas in consideration of the situation whether the reforming catalyst body is normal or deteriorated is shown in FIG. It is predicted that it is determined as follows.

  According to the above analysis simulation results, the appropriate temperature of the shift catalyst body is a physical quantity that also reflects the deterioration state of the reforming catalyst body and correlates with the CO concentration in the post-shift gas discharged from the shift catalyst body. And can be considered.

  For this reason, the CO concentration estimated value in the gas after the shift can be calculated more appropriately by picking up the temperatures of both the shift catalyst near the upstream end and the downstream end of the shift catalyst.

  In short, regarding the temperature of the downstream portion of the shift catalyst body shown in FIG. 3 (for example, the value on the horizontal axis in FIG. 3 is around 100 to 143), the temperature distribution of the shift catalyst body normal model (thick solid line and thick dashed line) While there is a significant temperature difference between the temperature distribution of the shift catalyst deterioration model and the temperature distribution of the conversion catalyst deterioration model (thick dotted line and thick two-dot chain line), the unconditional temperature distribution of the reforming catalyst (for example, the conversion catalyst deterioration model) The temperature distribution indicated by the thick dotted line) and the temperature distribution of the reforming catalyst deterioration condition (for example, the temperature distribution indicated by the thick two-dot chain line in the case of the shift catalyst body deterioration model) The temperature difference in the vicinity is extremely small, and even if the temperature is picked up, there is a possibility that the two cannot be distinguished significantly. Therefore, if the temperature of the upstream portion of the shift catalyst body shown in FIG. 3 (for example, the numerical value on the horizontal axis in FIG. 3 is around 43 to 70) is used, the temperature distribution without reforming catalyst deterioration and the presence of reforming catalyst deterioration are present. A significant temperature difference is recognized between the temperature distribution of the conditions and the two can be appropriately distinguished.

  Here, a specific method for calculating the CO concentration in the post-transform gas based on the upstream end temperature and the downstream end temperature of the shift catalyst body will be exemplified.

  FIG. 5 shows the post-transformation associated with each of the change in the upstream end temperature Tsu detected by the upstream temperature detector 18 and the change in the downstream end temperature Tsd detected by the downstream temperature detector 19. It is an image figure (henceforth a "temperature-CO density | concentration figure") which showed the change of CO density | concentration distribution in gas. In this case, the catalytic activity of both the shift catalyst body 12 and the reforming catalyst body is not lowered [“Tsu = Tsu (0), Tsd = Tsd (0) of black circles in the figure; CO concentration: CO = 0.5 % ”From the point of“% ”, after a certain period of time as the total number of operations of the hydrogen generator and / or the increase in the total number of operations, the catalytic activity of the shift catalyst body 12 and the reforming catalyst body decreases. The white circle of “Tsu = Tsu (1), Tsd = Tsd (1); CO concentration: 1.0% point” is shown.

  Of course, when the present technology is applied to the hydrogen generator 100, the change in the upper and lower temperature detectors 18 and 19 and the change in the CO concentration in the transformed gas, which are calculated or actually measured by an analysis simulation or an actual machine durability test. Based on the correlation result between them, a completed drawing of the temperature-CO concentration diagram needs to be prepared in advance.

In the temperature-CO concentration diagram shown in FIG. 5, during the increase in the CO concentration in the transformed gas, the temperature change of the upstream temperature detector 18 due to the decrease in the catalytic activity of the reforming catalyst body [for example, The CO concentration increase contribution corresponding to “Tsu (1) −Tsu (0)” and the temperature change of the downstream temperature detector 19 due to the decrease in the catalytic activity of the shift catalyst body 12 “For example,“ Tsd ( 1) -Tsd (0) "" and the corresponding CO concentration increases contribution is, although included in atomically, CO concentration increased contribution corresponding to the temperature change of the two is the detection of these as already described Since the separation by the pair of temperatures of the shift catalyst body 12 by the vessels 18 and 19 is possible, each CO concentration increase contribution can be estimated appropriately, thereby improving the accuracy of the temperature-CO concentration diagram.

  Note that such data of the temperature-CO concentration chart is stored in advance in a storage unit (not shown) of the control device 20, and can be appropriately read from the storage unit by the control device 20.

  Therefore, according to the present embodiment, the control device 20 acquires a pair of temperatures detected by each of the upstream temperature detector 18 and the downstream temperature detector 19 and converts the temperature based on such a pair of temperatures. The CO concentration estimated value in the transformed gas discharged from the vessel 13 can be calculated with high accuracy.

  Next, an operation example of CO removal by the selective oxidizer 14 that can cope with an increase in CO concentration due to a decrease in the catalytic activity of the reforming catalyst body and / or the shift catalyst body 12 as described above will be described.

  Here, the operating conditions of the hydrogen generator 100 using the raw material gas 13A are rated (flow rate of the raw material gas 13A: 4.0 L / min), and the CO concentration before and after the catalytic activity decrease in the gas after the transformation is The operation example will be described on the assumption that the ratio is changed from 0.5% (catalytic activity unreduced) to 1.0% (catalytic activity decreased).

Since the CO in the gas after the transformation is removed by a CO oxidation reaction (a reaction that oxidizes CO with oxygen in the air and converts it into CO ₂ ) by the selective oxidizer 14 (selective oxidation catalyst body), the CO is oxidized. If so, the required amount of oxygen should be half of CO (O ₂ /CO=0.5).

However, in the gas after the transformation, a large amount of hydrogen is present in addition to CO (hydrogen is very easy to react with oxygen), and the CO concentration by the selective oxidizer 14 is sufficiently ensured. From the viewpoint of removing oxygen to 20 ppm or less, excess oxygen of O ₂ /CO=1.5 to ₂ (3 to 4 times oxygen atom with respect to CO) is required in the selective oxidizer 14.

Here, when the catalytic activity of the catalyst body has not decreased, 0.5% of CO is contained in the transformed gas, and this flow rate conversion value may be the raw material gas flow rate during the rated operation of the hydrogen generator 100. CO flow rate is 0.1 L / min. For this reason, the air flow rate supplied to the selective oxidizer 14 from the selective oxidizer air supply 22 so that O ₂ / CO = 2 is about 1.0 L / min.

On the other hand, when the catalytic activity of the catalyst body is reduced, 1.0% of CO is contained in the transformed gas, and this flow rate conversion value is CO 2 if the raw material gas flow rate during the rated operation of the hydrogen generator 100. The flow rate is 0.2 L / min. For this reason, the air flow rate supplied to the selective oxidizer 14 from the selective oxidizer air supply 22 so that O ₂ / CO = 2 is about 2.0 L / min.

  In this way, the control device 20 sequentially monitors the calculated estimated CO concentration value and the raw material gas flow rate by the raw material gas supplier 15, and removes CO in the post-transformation gas based on these values. The selective oxidation air supplier 22 can supply the CO selective oxidation air without excess or deficiency.

[Modification 1]
In the first embodiment, an example in which the control device 20 calculates the estimated CO concentration value in the gas after the transformation based on the temperature-CO concentration diagram has been described. In consideration of the total operating time information and the total number of operation information of the hydrogen generator 100, an estimated CO concentration value in the transformed gas is calculated, and the supply amount of CO selective oxidation air is controlled based on the estimated value. As a result, the characteristics of the hydrogen generator 100 can be further stabilized. That is, from the results of the durability test of the hydrogen generator 100 and the durability test of the catalyst alone, the CO concentration in the post-transformation gas with respect to the total operation time and the total number of operations is predicted. Compared with the predicted CO concentration value in the gas after the transformation, the result of the higher CO value is regarded as the CO concentration in the gas after the transformation of the hydrogen generator 100 at that time, and CO selective oxidation air is supplied. To do. By doing so, it is possible to realize a hydrogen generating apparatus that suppresses the CO concentration in the generated gas from the hydrogen generating apparatus 100 as much as possible and supplies the generated gas in a stable CO state. This is for supplying a stable generated gas even when the amount of gas supplied by the hydrogen generator 100, the amount of water, the temperature value being sensed, etc. deviate for some reason.

  Then, in addition to the temperature-CO concentration chart, the control device 20 more accurately converts the post-transformation gas based on the total operating time information-the CO concentration data in the hydrogen-containing gas and the total operation frequency information-the CO concentration data in the hydrogen-containing gas. As a result, it is expected that the air flow rate by the selective oxidizing air supply device 22 for removing CO in the gas after the transformation can be controlled more appropriately.

[Modification 2]
In the first embodiment, upstream and downstream temperature detectors 18 and 19 of the shift catalyst body 12 are installed at two locations, an upstream end portion and a downstream end portion of the shift catalyst body 12, and upstream and downstream of the shift catalyst body 12. Although the example in which the temperature on the side is directly detected has been described, the location and number of such temperature detectors are changed and corrected appropriately according to the catalytic reaction status of the reforming catalyst body and / or the shift catalyst body 12. Also good.

  For example, the temperature detection portion of the shift catalyst body 12 does not necessarily have to be a mode in which the temperature of the shift catalyst body is directly detected like the upstream end portion or the downstream end portion of the shift catalyst body 12. Even if the temperature detector is installed in such a manner that the temperature of the upstream portion and the downstream portion of the shift catalyst body 12 in the flow direction of the hydrogen-containing gas can be indirectly detected, the temperature intended in this specification can be appropriately obtained. It is done. For example, a temperature detector may be installed at a suitable position inside the transformer 13 so as to detect the temperature of the gas flowing into and out of the shift catalyst body 12, and the transformer is detected so as to detect the surface temperature of the container of the transformer 13. You may install a temperature detector in the 13 surface suitable place. The temperature of the upstream portion and the downstream portion of the shift catalyst body 12 can be indirectly obtained by correcting the data obtained in this way by utilizing the correlation with the directly obtained temperature.

(Embodiment 2)
As an application example of the hydrogen generator 100 described in Embodiment 1, a fuel cell system 110 including a fuel cell 30 that generates and exhausts heat using a hydrogen-rich hydrogen-containing gas supplied from the hydrogen generator 100 is provided. is there.

  FIG. 6 is a block diagram showing a schematic configuration of the fuel cell system according to Embodiment 2 of the present invention.

  The fuel cell system 110 mainly includes a hydrogen generation device 100, a fuel cell 30, and a heat recovery device 32.

  The fuel cell 30 is a known polymer electrolyte fuel cell, and the description of the internal configuration of the fuel cell 30 is omitted here. The hydrogen generator 100 is an apparatus according to the first embodiment, and the description of the hydrogen generator 100 is omitted.

  The anode of the fuel cell 30 communicates with the hydrogen generator 100 via the gas outlet port 21 of the hydrogen generator 100, whereby the hydrogen-containing gas (fuel gas) discharged from the hydrogen generator 100 is converted into fuel. It is supplied to the anode of the battery 30. Further, the cathode of the fuel cell 30 communicates with the air supply blower 31, whereby air (oxidant gas) discharged from the blower 31 is supplied to the cathode of the fuel cell 30.

  The heat recovery device 32 is, for example, a hot water generating device provided with a hot water storage tank (not shown), and circulates the cooling water in the hot water storage tank so as to pass through the inside of the fuel cell 30 to keep the inside of the fuel cell 30 at an appropriate temperature. In addition, the exhaust heat generated during power generation of the fuel cell 30 can be recovered by heat exchange with the cooling water. Further, the hot water in the hot water storage tank is subjected to an appropriate purification process and then sent as reforming water to the reforming water supplier 16 (see FIG. 1) of the hydrogen generator 100.

  The fuel cell system 110 can supply the power generated by the fuel cell 30 to an appropriate power load terminal (not shown), and can supply the heat recovered by the heat recovery device 32 to an appropriate heat load terminal (not shown). It is configured.

  That is, in this fuel cell 30, the hydrogen-containing gas supplied to the anode and the air supplied to the cathode react (power generation reaction), and a power generation operation for generating generated power is executed. Is generated. The power generated by the fuel cell 30 is supplied to the power load terminal and used. The exhaust heat from the fuel cell 30 is recovered by the heat recovery device 32, supplied to the thermal load terminal, and used for various purposes. The hydrogen-containing gas (fuel offgas) discharged from the anode of the fuel cell 30 without being used for the power generation reaction is led to the burner 17 (see FIG. 1) of the hydrogen generator 100, where the combustion fuel of the burner 17 is burned. Used as

  According to the present embodiment, even if the catalytic activity decreases in a part of the reformed and / or modified catalyst body due to long-term operation of the hydrogen generator 100 or the like, the high quality ( As a result, the fuel cell 30 can maintain highly efficient and stable power generation and exhaust heat for a long period of time.

  Here, the fuel cell system 110 is illustrated as one usage form of the hydrogen generation technique according to the first embodiment, but such a technique is a hydrogen utilization technique other than the fuel cell (for example, a turbine combustor, an engine, or the like). Can also be diverted.

  The hydrogen generator of the present invention can accurately calculate the estimated CO concentration in the gas after the conversion when the catalytic activity of the conversion catalyst body and the reforming catalyst body is reduced. For example, the hydrogen generation device for the home fuel cell system It is useful as a supply device.

It is the block diagram which showed schematic structure of the hydrogen generator which concerns on Embodiment 1 of this invention. It is a diagram showing the correlation between the shift catalyst temperature and the CO concentration, using the number of water wetting of the shift catalyst body as a parameter, In the normal shift catalyst body model and the shift catalyst deterioration model, the horizontal axis represents the distance along the gas flow direction of the shift catalyst body with respect to the upstream end of the shift catalyst body, and the vertical axis represents the shift catalyst temperature. It is the figure which showed the analysis simulation result of the correlation between both. In the normal conversion catalyst body model and the deterioration catalyst body deterioration model, the horizontal axis indicates the distance along the gas flow direction of the shift catalyst body with respect to the upstream end of the shift catalyst body, and the vertical axis indicates the CO molar concentration. It is the figure which showed the analysis simulation result of the correlation between. It is a temperature-CO density | concentration figure. It is the block diagram which showed schematic structure of the fuel cell system which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Reformer 12 Transformation catalyst body 13 Transformer 14 Selective oxidizer 15 Raw material gas supply device 16 Reformed water supply device 17 Burner 18 Upstream temperature detector 19 Downstream temperature detector 20 Control device 21 Gas outlet port 22 Selective oxygen air supply 30 Fuel cell 31 Blower 32 Heat recovery device 100 Hydrogen generator 110 Fuel cell system

Claims (3)

A reformer that generates a hydrogen-containing gas by a reforming reaction using a raw material gas containing an organic compound composed of at least carbon and hydrogen;
A shifter configured to reduce the carbon monoxide gas in the hydrogen-containing gas by a shift reaction by passing the hydrogen-containing gas through the shift catalyst body;
An upstream temperature detector for detecting the temperature of the upstream portion of the shift catalyst body in the flow direction of the hydrogen-containing gas;
A downstream temperature detector for detecting the temperature of the downstream portion of the shift catalyst body in the flow direction of the hydrogen-containing gas; and
An air supply for supplying air to the hydrogen-containing gas discharged from the transformer;
A selective oxidizer for reducing carbon monoxide gas in the hydrogen-containing gas discharged from the transformer by an oxidation reaction with the air;
A control device,
The control device, the upstream temperature detector to obtain a change in a more sensed Ru temperature change and said downstream temperature sensor in the temperature detected by, corresponding to each of the previous SL temperature changes, the modified The carbon monoxide gas concentration increasing contribution in the hydrogen-containing gas discharged from the vessel is estimated, and the carbon monoxide gas concentration increasing contribution and the flow rate of the source gas are used to supply the air supply device A hydrogen generator that controls the flow rate of air. Wherein the control unit obtains at least one of total operating time of the hydrogen generator information and total operating count information, on the basis of the total operating time information and / or the total operating count information, the air The hydrogen generator according to claim 1, wherein the flow rate is controlled . The hydrogen generator according to claim 1 or 2 ,
An oxidant gas supply,
A fuel cell that generates electricity using the reducing agent gas supplied by the hydrogen generator and the oxidizing gas supplied by the oxidizing gas supplier;
A fuel cell system comprising:

Images