JP4073227B2 - Operation method of hydrogen-containing gas generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention adds oxygen to a hydrogen-containing gas produced by reforming raw fuel, selectively oxidizes carbon monoxide contained in the hydrogen-containing gas, and The present invention relates to a method for operating a hydrogen-containing gas generation apparatus including a carbon monoxide remover that reduces the concentration of carbon oxide to a predetermined concentration or less.
[0002]
[Prior art]
A fuel cell is a device that generates electricity by chemically reacting hydrogen and oxygen. Usually, the oxygen can be obtained from air, and hydrogen can be obtained from a gas containing alcohol or hydrocarbon. Here, when hydrogen is obtained from a gas containing alcohol or hydrocarbon, it is necessary to reform the hydrocarbon into a hydrogen-containing gas using a hydrogen-containing gas generator.
[0003]
In a typical hydrogen-containing gas generator, a raw fuel supply unit that supplies raw fuel and a desulfurization that performs desulfurization of the raw fuel are provided on a main path from the supply of raw fuel containing hydrocarbons to the generation of hydrogen-containing gas. A desulfurizer to perform, a reformer that reacts raw fuel and water after desulfurization to generate a hydrogen-containing gas, and carbon monoxide contained in the hydrogen-containing gas using a carbon monoxide conversion catalyst to form hydrogen and carbon dioxide The carbon monoxide is selectively oxidized by selectively oxidizing a small amount of carbon monoxide in the hydrogen-containing gas that has passed through the transformer, and further reducing the concentration of carbon monoxide contained in the hydrogen-containing gas. A carbon remover is provided.
[0004]
Here, methane (CH_Four) Is supplied as raw fuel gas, the reforming reaction performed in the reformer is represented by the following chemical reaction formula.
[0005]
[Chemical 1]
CH_Four+ H₂O → 3H₂+ CO
CH_Four+ 2H₂O → 4H₂+ CO₂
[0006]
Specifically, a step is performed in which the reforming catalyst provided in the reformer is heated to a temperature at which the reforming reaction is activated, and the raw fuel gas and steam react on the surface of the reforming catalyst. Is called. After that, using a copper-zinc-based or iron-chromium-based carbon monoxide conversion catalyst provided in the transformer, a conversion treatment is performed in which carbon monoxide and water are reacted to convert them into carbon dioxide and hydrogen. .
[0007]
Furthermore, in the polymer electrolyte fuel cell, since it is known that the electrode catalyst of the fuel cell is poisoned by the presence of carbon monoxide, in order to avoid this, in the generated hydrogen-containing gas, A carbon monoxide remover that reduces the concentration of carbon monoxide contained in a trace amount to a predetermined concentration or less has been provided in the subsequent stage of the transformer.
[0008]
Specifically, the carbon monoxide remover contains a catalyst layer having a carbon monoxide removal catalyst formed by supporting a noble metal such as ruthenium, rhodium, platinum, palladium on a carrier such as alumina. As the hydrogen-containing gas and oxygen (air) are supplied to the catalyst layer and the reaction shown in the chemical reaction formula below is activated, the carbon monoxide contained in the hydrogen-containing gas is shown in the chemical reaction formula below. The concentration of carbon monoxide contained in the hydrogen-containing gas is reduced to tens of ppm or less.
[0009]
[Chemical formula 2]
2CO + O₂→ 2CO₂
[0010]
In the above chemical reaction formula, the theoretical value of the number of moles of oxygen required to selectively oxidize carbon monoxide is ½ of the number of moles of carbon monoxide, but the monoxide contained in the hydrogen-containing gas. In order to sufficiently oxidize carbon, in practice, oxygen having a mole number approximately twice the mole number of carbon monoxide has been added.
[0011]
[Problems to be solved by the invention]
In a fuel cell, the amount of raw fuel supplied to the reforming process is increased or decreased according to the output power of the fuel cell. In order to increase the output power of the fuel cell, the raw fuel supplied to the reforming process is increased. When the change is made to increase the supply flow rate of the gas, the reforming reaction and the shift reaction are not stable until a predetermined period has elapsed from the start of the change, and one of the hydrogen-containing gases supplied to the carbon monoxide remover is not stable. The problem arises that the carbon oxide concentration increases and the amount of oxygen used to selectively oxidize carbon monoxide is insufficient. As a result, the electrode catalyst of the fuel cell is poisoned.
[0012]
Furthermore, in view of the above problem, when the amount of oxygen to be added is further increased, not only the carbon monoxide is oxidized, but also hydrogen generated by the reforming process is oxidized. This leads to a problem that the amount of hydrogen required for power generation by the battery decreases.
[0013]
The present invention has been made in view of the above-described problems, and its purpose is to selectively select carbon monoxide even when the supply flow rate of the raw fuel supplied for the reforming process is changed. The present invention provides a method for operating a hydrogen-containing gas generating apparatus that can be oxidized and removed.
[0014]
[Means for Solving the Problems]
  The first characteristic configuration of the operation method of the hydrogen-containing gas generation device according to the present invention for solving the above-mentioned problems is,originalOxygen is added to the hydrogen-containing gas generated by reforming the fuel to selectively oxidize carbon monoxide contained in the hydrogen-containing gas, and the concentration of carbon monoxide in the hydrogen-containing gas is reduced. An operation method of a hydrogen-containing gas generation apparatus including a carbon monoxide remover that reduces to a predetermined concentration or less, wherein a change in which the supply flow rate of the raw fuel to be subjected to reforming increases is a predetermined change period The ratio of the oxygen addition amount at a predetermined time during the change period and the predetermined period after the change period to the oxygen addition amount before the change start is the raw fuel before the change start. The oxygen addition amount during the change period and the predetermined period is adjusted to be larger than the ratio of the supply flow rate of the raw fuel at the predetermined time to the supply flow rate ofThe oxygen addition amount after elapse of the predetermined period is such that the ratio of the oxygen addition amount after elapse of the predetermined period to the oxygen addition amount before the start of change is relative to the supply flow rate of the raw fuel before the change start. The amount is adjusted to be equal to the ratio of the supply flow rate of the raw fuel after the change period.In the point.
  The second characteristic configuration of the operation method of the hydrogen-containing gas generation device according to the present invention for solving the above-described problem is that oxygen is added to the hydrogen-containing gas generated by reforming the raw fuel. A hydrogen-containing gas generating device comprising a carbon monoxide remover that selectively oxidizes carbon monoxide contained in the hydrogen-containing gas and reduces the concentration of carbon monoxide in the hydrogen-containing gas to a predetermined concentration or less. In the operation method, when a change in which the supply flow rate of the raw fuel to be subjected to the reforming process is increased requires a predetermined change period, the oxygen addition amount before the start of the change is changed during the change period. The ratio of the oxygen addition amount at a predetermined time during the predetermined period after the change period is larger than the ratio of the supply flow rate of the raw fuel at the predetermined time to the supply flow rate of the raw fuel before the change start. As before The amount of oxygen added during the change period and the predetermined period is adjusted, and the length of the predetermined period is the supply of the raw fuel at the end of the change period with respect to the supply flow rate of the raw fuel before the start of the change. The length is adjusted to a length expressed as a function of the flow rate ratio or its equivalent.
[0015]
  A first method of operating a hydrogen-containing gas generator according to the present invention for solving the above-mentioned problemsthreeThe characteristic configuration of the firstOr secondIn addition to the characteristic configuration of the above, the amount of oxygen added during the change period and the predetermined period is a ratio of the supply flow rate of the raw fuel at the predetermined time to the supply flow rate of the raw fuel before the start of change or an equivalent thereof It is in the point that it is adjusted to the quantity expressed as a function of the quantity.
[0018]
  The operation and effect will be described below.
  According to the first characteristic configuration of the operation method of the hydrogen-containing gas generation device according to the present invention, when a change in which the supply flow rate of the raw fuel supplied to the reforming process is increased, the oxygen addition before the start of the change is performed. The ratio of the oxygen addition amount at a predetermined time during the change period and the predetermined period after the change period to the amount is from the ratio of the raw fuel supply flow rate at the predetermined time to the raw fuel supply flow rate before the change start. The amount of oxygen added during the change period of the supply flow rate and during the predetermined period after the change period (while the reforming reaction is not stable) is adjusted, so that the concentration of carbon monoxide in the hydrogen-containing gas However, the problem of insufficient oxygen used to selectively oxidize the carbon monoxide does not occur even when the temperature rises compared to before the start of the change.
  In addition, when a change in which the supply flow rate of the raw fuel supplied to the reforming process is increased, after a predetermined period after the change period, that is, the reforming reaction is stabilized, After the carbon monoxide concentration is stabilized, the ratio of the oxygen addition amount after the predetermined period to the oxygen addition amount before the change start is the supply flow rate of the raw fuel after the change period to the supply flow rate of the raw fuel before the change start. Since the amount of oxygen added is adjusted to an amount equal to the above ratio, an appropriate amount of oxygen can be added to selectively oxidize carbon monoxide in the hydrogen-containing gas.
  Further, according to the second characteristic configuration of the operation method of the hydrogen-containing gas generation device according to the present invention, as described in the first characteristic configuration, the concentration of carbon monoxide in the hydrogen-containing gas is compared with that before the start of the change. In the case where the amount of oxygen used to selectively oxidize the carbon monoxide does not arise, the problem of the raw fuel used in the reforming process does not occur. When a change is made to increase the supply flow rate, the length of the predetermined period is the ratio of the supply flow rate of the raw fuel at the end of the change period to the supply flow rate of the raw fuel before the start of the change, or Since it is adjusted based on the amount expressed as a function of the equivalent amount, it is suitable for the period in which the state in which the concentration of carbon monoxide in the hydrogen-containing gas is increased in the selective oxidation step of carbon monoxide than before the start of the change. Period, in hydrogen-containing gas It can be added to suitable amount of oxygen to increase the amount of carbon monoxide concentrations. As a result, there is no problem that the amount of oxygen used to selectively oxidize carbon monoxide in the hydrogen-containing gas is insufficient. Further, there is no problem that the hydrogen generated by the reforming process is oxidized.
[0019]
  A first method of operating a hydrogen-containing gas generator according to the present inventionthreeAccording to this characteristic configuration, when a change is made in which the supply flow rate of the raw fuel supplied for the reforming process is increased, the oxygen addition amount during the change period and during the predetermined period is the same as that before the start of the change. In the selective oxidation step of carbon monoxide, the hydrogen-containing gas is adjusted based on the ratio expressed as a function of the ratio of the supply flow rate of the raw fuel at the predetermined time to the supply flow rate of fuel or the equivalent amount thereof. A suitable amount of oxygen can be added to the degree of increase in the concentration of carbon monoxide. As a result, there is no problem that the amount of oxygen used to selectively oxidize carbon monoxide in the hydrogen-containing gas is insufficient. Further, there is no problem that the hydrogen generated by the reforming process is oxidized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
First, the configuration of a hydrogen-containing gas generator in which an operation method according to the present invention is implemented will be described with reference to the drawings.
The hydrogen-containing gas generating device illustrated in FIG. 1 is a device that receives supply of raw fuel gas to generate a hydrogen-containing gas, and supplies the hydrogen-containing gas to a fuel cell. Accordingly, the hydrogen-containing gas generator includes a desulfurizer 1 that desulfurizes raw fuel (raw fuel gas) containing hydrocarbons, and a steam generator that vaporizes water by water heating means (not shown) to generate water vapor. 2, a reformer 3 that reacts desulfurized raw fuel gas with water vapor to generate a hydrogen-containing gas, a transformer 4 that transforms carbon monoxide contained in the hydrogen-containing gas into carbon dioxide, and a transformer And a carbon monoxide remover 5 for oxidizing a small amount of carbon monoxide present in the hydrogen-containing gas that has passed through 4 to further reduce the concentration of carbon monoxide contained in the hydrogen-containing gas.
[0023]
The desulfurizer 1 uses methane gas (CH_Four) And a city gas to which a sulfur compound is added as an odorant is used as a raw fuel gas, it is first used as an apparatus for removing the sulfur compound by desulfurizing the raw fuel gas. The In this desulfurization treatment, a desulfurization method is used in which hydride obtained by adding hydrogen to the raw fuel gas and reacting both with a catalyst is adsorbed on zinc oxide or the like. The hydrogen added to the raw fuel gas for desulfurization includes a method of directly supplying from a separately provided hydrogen tank, and a method of returning and using the hydrogen-containing gas generated in the reformer 3.
[0024]
The reformer 3 reacts the desulfurized raw fuel gas (methane gas) with the steam supplied from the steam generator 2 by the catalytic action of the reforming catalyst, thereby generating a hydrogen-containing gas containing hydrogen and carbon monoxide. It is a device to generate. During this reaction, the reforming catalyst is maintained at a temperature of, for example, 650 ° C. to 750 ° C. by a reforming catalyst heating means (not shown), and methane gas and water vapor are reformed according to the following chemical reaction formula to generate hydrogen A contained gas is produced.
[0025]
[Chemical Formula 3]
CH_Four+ H₂O → 3H₂+ CO
CH_Four+ 2H₂O → 4H₂+ CO₂
[0026]
The raw fuel gas is not limited to the city gas mainly composed of methane, and a gas containing various hydrocarbons such as propane and butane can be used.
[0027]
The transformer 4 is a device that transforms carbon monoxide contained in the hydrogen-containing gas supplied from the reformer 3 into carbon dioxide. The reason why carbon monoxide is converted to carbon dioxide is to prevent electrode poisoning that occurs when carbon monoxide is supplied to the fuel cell 6. At this time, the carbon monoxide conversion catalyst that converts carbon monoxide into carbon dioxide is maintained at a temperature of, for example, 150 ° C. to 250 ° C. by a temperature adjusting means (not shown) for adjusting the temperature of the catalyst, Carbon monoxide and water vapor are converted according to the following chemical reaction formula by the catalytic action of the carbon monoxide conversion catalyst.
[0028]
[Formula 4]
CO + H₂O → CO₂+ H₂
[0029]
The carbon monoxide remover 5 adds oxygen to the hydrogen-containing gas that has been subjected to the transformation treatment in the transformer 4, and the carbon monoxide contained in a trace amount in the hydrogen-containing gas is represented by the following chemical reaction formula. This is a device that selectively oxidizes to reduce the concentration of contained carbon monoxide to a predetermined concentration or less. The oxygen added in this oxidation step can utilize air.
[0030]
[Chemical formula 5]
2CO + O₂→ 2CO₂
[0031]
By using the hydrogen-containing gas generating apparatus as described above, the hydrogen-containing gas whose carbon monoxide concentration is reduced to tens of ppm or less is supplied to the fuel cell 6. Poison is suppressed. As a result, the operation of the fuel cell 6 can be continued without reducing the power generation efficiency in the fuel cell 6.
[0032]
Hereinafter, an operation method of the hydrogen-containing gas generation device according to the present invention, in particular, an oxidation process of carbon monoxide in the carbon monoxide remover 5 will be described in detail with reference to the drawings.
[0033]
As described above, the supply flow rate of the raw fuel supplied to the reformer 3, the supply flow rate of water vapor, and the oxygen addition amount for selectively oxidizing carbon monoxide contained in the hydrogen-containing gas are adjusted. Although it is necessary, it is performed by adjusting the opening degree of the valve V1, the valve V2, and the valve V3 by the control unit 7. The control unit 7 is configured to be able to monitor the direct current output from the fuel cell 6. In order to know the direct current output from the fuel cell 6, it may be measured using a normal direct current ammeter.
[0034]
In the oxidation step performed in the carbon monoxide remover 5, the carbon monoxide remover 5 converts a first mole number of oxygen at a constant ratio with respect to the mole number of carbon monoxide contained in the hydrogen-containing gas after the shift treatment. The selective oxidation reaction of carbon monoxide is performed. Here, when the operation of the hydrogen-containing gas generator is performed with the valve V1 and the valve V2 being opened at a constant degree, the reformer 3 shown in the chemical reaction formula 3 and the chemical reaction formula 4 and Since the reaction in the transformer 4 is also performed stably, the concentration of carbon monoxide contained in the hydrogen-containing gas after the transformation treatment is also in a constant state. Therefore, the control unit 7 controls the opening degree of the valve V3 (the amount of oxygen added) so as to maintain a constant state.
[0035]
Here, the fuel cell 6 increases or decreases the supply flow rate of the raw fuel supplied to the reforming process in accordance with the output power of the fuel cell, but increases the output power of the fuel cell 6 (increases the direct current). In addition, the control unit 7 performs control to increase the supply flow rate of the raw fuel used for the reforming process.
[0036]
When the output power of the fuel cell 6 is changed, the control unit 7 adjusts the opening degree of the valve V1 and the valve V2, and supplies the reformer 3 with raw fuel and steam in amounts corresponding to the changed output power. . Here, when the change is made such that the ratio of the supply flow rate of the raw fuel at the predetermined time t during the change period to the supply flow rate of the raw fuel before the start of the change becomes a (t) = a × t, Since the concentration of carbon monoxide contained in the hydrogen-containing gas after the transformation treatment in the vessel 4 also changes, the control unit 7 newly adjusts the opening of the valve V3 and is used for selective oxidation of carbon monoxide. It is also necessary to change the supply flow rate of oxygen from y to Y (t).
[0037]
FIG. 2 illustrates the supply flow rate of the raw fuel used for the reforming process at time t in order to increase the output power of the fuel cell 6.₁To time t₂The number of moles of carbon monoxide and the number of moles of oxygen added to the hydrogen-containing gas after the modification treatment when a change that is doubled during the period (change period) is performed (FIG. 2A). It is a graph which shows the change (FIG.2 (b)). In FIG. 2, the amount of oxygen added is represented by the number of moles. As shown in FIG. 2B, in this embodiment, the time t at which the supply flow rate of the raw fuel is changed.₁Until now, the number of moles of oxygen added is set to twice the number of moles of carbon monoxide.
[0038]
As described above, when the supply flow rate of the raw fuel supplied to the reforming process is changed, as shown in FIG. 2B, the amount of carbon monoxide contained in the hydrogen-containing gas also increases. . However, during the change period (time t₁To time t₂The ratio of the supply flow rate of the raw fuel at a predetermined time t: (a) is changed so that the coefficient a is large (that is, the supply flow rate of the raw fuel per unit time is large). In some cases, the amount of carbon monoxide in the hydrogen-containing gas during the change period, and a predetermined period after the change period (time t₂To time t_Three2), the amount of carbon monoxide in the hydrogen-containing gas changes following the increase in raw fuel as illustrated in FIG. 2B (in other words, the amount of carbon monoxide generated increases) Is not in a state in which the carbon monoxide concentration in the hydrogen-containing gas does not change), as illustrated in FIG. 3, the carbon monoxide concentration in the hydrogen-containing gas is temporarily increased so that the carbon monoxide concentration temporarily increases. After the generation amount increases, after a predetermined period, a change that returns to the carbon monoxide concentration in the hydrogen-containing gas before the start of change and stabilizes is shown.
[0039]
Specifically, in FIG. 3, the supply flow rate of the raw fuel supplied to the reformer 3 is changed from a 50% operating state of maximum output per unit time to an operating state of 75% (changed to 1.5 times). Carbon monoxide generated in this case (ratio of supply flow rate of raw fuel after unit time to supply flow rate of raw fuel before start of change: a (t) = 1.5 × t) (%) In the hydrogen-containing gas and when the operation is changed from 50% of the maximum output per unit time to 100% operation (changed to 2 times) Graph of change with time of concentration (%) of carbon monoxide generated in hydrogen-containing gas in ratio of supply flow rate of raw fuel after unit time to supply flow rate: a (t) = 2 × t) Is shown. From FIG. 3, the larger the increase per unit time in the supply flow rate of raw fuel, the higher the concentration (%) of carbon monoxide contained in the hydrogen-containing gas before the start of the change. It turns out that the period until it returns to a density | concentration becomes long.
[0040]
Therefore, during the change period (time t₁To time t₂And during a predetermined period after the change period (time t₂To time t_ThreeAs shown in FIG. 2 (b), the amount of oxygen added during (between) and during the change period (time t₁To time t₂And during a predetermined period after the change period (time t₂To time t_ThreeThe ratio of the oxygen addition amount at a predetermined time t during (between) is larger than the ratio of the raw fuel supply flow rate at the predetermined time t to the raw fuel supply flow rate before the start of change (waveform A). It is necessary to adjust by the control unit 7. That is, as shown in the waveform B of FIG. 2B, the ratio of the oxygen addition amount at the predetermined time t during the change period and during the predetermined period after the change period to the oxygen addition amount before the change start is the change start. It can be said that an oxygen addition amount that is equivalent to the ratio of the raw fuel supply flow rate at the predetermined time t to the previous raw fuel supply flow rate is not sufficient for the selective oxidation of carbon monoxide.
[0041]
Here, during the change period (time t₁To time t₂And a predetermined period after the change period (time t)₂To time t_ThreeThe oxygen addition amount Y (t) at a predetermined time t during (b) is a ratio of the raw fuel supply flow rate at the predetermined time t to the raw fuel supply flow rate before the change start: a (t) = a × It can be expressed by the following formula as a function of t. In the case of performing an operation for reducing the output power of the fuel cell 6, the oxygen supply amount is not changed, and the ratio of the oxygen addition amount after the change to the oxygen addition amount before the change start is changed. An amount of oxygen equal to the ratio of the raw fuel supply flow rate after the start of change to the raw fuel supply flow rate before the start is added.
[0042]
[Expression 1]
Y = y (1 + K × a (t)) (K is a proportional constant)
a (t) = a × (t−t₁(T₁≦ t ≦ t₂)
a (t) = a (t₂<T ≦ t_Three)
[0043]
Further, a predetermined period (time t) after the change period of the raw fuel supply flow rate₂To time t_ThreeIs a transient period until the reforming reaction is stabilized after the supply flow rate of the raw fuel is changed, and during this period, as described above, the time t₂The amount of oxygen used to selectively oxidize carbon monoxide during the selective oxidation step of carbon monoxide by adding oxygen equal to the amount of oxygen added at the end of the change period. Generation | occurrence | production of the problem that an addition amount is insufficient can be suppressed.
[0044]
Furthermore, time t_ThreeIs the time when the reforming reaction after the change of the supply flow rate of the raw fuel supplied to the reforming process is stabilized, and thereafter the selection of carbon monoxide performed in the carbon monoxide remover 5 In the oxidation step, after a predetermined period after the change period with respect to the oxygen addition amount before the start of change has elapsed (time t_ThreeThe ratio of the oxygen addition amount in the subsequent period) is equal to the ratio of the supply flow rate of the raw fuel at the end of the change period to the supply flow rate of the raw fuel before the start of change: Y / y = a) is supplied.
[0045]
Also, time t₂To time t_ThreePeriod (predetermined period after the change period): Also for T, the ratio of the raw fuel supply flow rate at the end of the change period to the raw fuel supply flow rate before the change start: Can be expressed as
[0046]
[Expression 2]
T = k × a (k is a proportional constant)
[0047]
FIG. 4 shows an example of two cases in which the amount of increase in raw fuel per unit time is different from each other.₁To time t₂Period (change period) and time t₂To time t_ThreeAmount of oxygen added during the period (predetermined period after the change period), and time t₂To time t_ThreeIt is a figure explaining length T of this period (predetermined period after a change period).
[0048]
FIG. 4A shows a state before the start of change (time t₁) For the raw fuel supply flow rate₂Is the example in which the ratio of the supply flow rate of raw fuel at b is b₂To time t_ThreeThe length of the period is T_bIt is represented by Further, FIG. 4B shows a state before the start of change (time t₁) For the raw fuel supply flow rate₂Is a case where the ratio of the supply flow rate of the raw fuel at b ′ is b ′, and the time t₂To time t_ThreeThe length of the period is T_{b '}It is represented by However, b <b ′.
[0049]
In this case, as described with reference to FIG. 3, the period until the reforming reaction is stabilized as the ratio of the supply flow rate of the raw fuel after the change period to the supply flow rate of the raw fuel before the change start is larger. However, in the operation method of the hydrogen-containing gas generation device according to the present invention, the larger the ratio of the supply flow rate of the raw fuel after the change period to the supply flow rate of the raw fuel before the change start, according to Equation 2, Time t₂To time t_ThreePeriod: When T is set to be long, an excessive amount of oxygen is supplied during a period in which the reforming reaction is unstable, and carbon monoxide in the hydrogen-containing gas is selectively oxidized. It is possible to suppress the occurrence of a problem that the amount of oxygen used in order to make it insufficient.
[0050]
In the above-mentioned formulas 1 and 2, the ratio of the supply flow rate of the raw fuel after the change to the supply flow rate of the raw fuel before the change start: oxygen addition amount Y as a function of a (t), and time t₂To time t_ThreeAlthough the derivation with respect to the length: T is derived, the equivalent amount of the ratio a (t) applicable to the equations 1 and 2 is as follows with respect to the direct current output of the fuel cell 6 before the start before the change. There is a ratio of the direct current output of the fuel cell 6 after the change period. Specifically, when the operation state of the fuel cell 6 is changed from an operation state of 50% of the maximum output amount of direct current per unit time to an operation state of 75% (when changing to 1.5 times), Since the control unit 7 performs control to change the supply flow rate of the raw fuel to 1.5 times per unit time, it can be said that both are equivalent. However, when an equivalent amount other than a: an increase amount of raw fuel per unit time is applied to Equations 1 and 2, it is necessary to appropriately change the values of the coefficients K and k in Equations 1 and 2. .
[0051]
(Example)
A specific example will be described by taking as an example the case where the direct current output of the fuel cell 6 is changed from 50% operation of the maximum output amount to 75% operation (1.5 times) during the elapsed time of 1 second (change period). Do. That is, a = 1.5 can be set in Equation 1 and Equation 2. As in the above-described embodiment, the time t₁To time t₂Is the change period and time t₂To time t_ThreeIs a predetermined period after the change period. Therefore, based on the above-described embodiment, the oxygen addition amount: Y and the length of the predetermined period after the change period: T can be expressed by the following formula 3.
[0052]
[Equation 3]
Y = y × (1 + K × 1.5 × (t−t₁)) (T₁≦ t ≦ t₂)
Y = y × (1 + K × 1.5) (t₂<T ≦ t_Three)
Y = y × 1.5 (t_Three<T)
T = t_Three-T₂
[0053]
In this case, the proportionality factors K and k, the oxygen addition amount y before the start of change, and the length of the predetermined period after the start of change: T are known, and the oxygen addition amount Y at time t after the change period is derived. Can do.
[0054]
<Another embodiment>
<1>
In the embodiment described above, the oxygen addition amount during the change period in which the supply flow rate of the raw fuel is changed and in the predetermined period after the change period is the predetermined amount after the change with respect to the supply flow rate of the raw fuel before the change start. As an example of the case where it is expressed as a function of the ratio of the supply flow rate of raw fuel at the time or its equivalent amount, an example in which the oxygen addition amount is linearly changed as in the case of Equation 1 and FIG. 2 will be described. However, the amount of oxygen added in the present invention is not limited to the above case. For example, when the oxygen addition amount is changed nonlinearly according to the ratio of the raw fuel supply flow rate at the predetermined time after the change to the raw fuel supply flow rate before the change start or a quadratic function of the equivalent amount, etc. It doesn't matter.
[0055]
<2>
Time t_ThreeHowever, the amount of oxygen added thereafter may not be decreased instantaneously as described in the above embodiment, but may be gradually decreased. For example, there is a method for reducing the amount of oxygen added as shown in FIG. 5 (a) and 5 (b) are the same graphs as the method for reducing the oxygen addition amount described with reference to FIGS. 2 (a) and 2 (b), but FIG. It is shown in order to clarify the difference. In the case of FIG. 5C described here, the time t after the reforming reaction is stabilized._ThreeRather, the time t when the reforming reaction starts to stabilize_Three’(T_Three’<T_Three) Gradually reduce the amount of oxygen added. Where time t_ThreeThe decrease rate of the oxygen addition amount represented by the slope of the subsequent graph is adjusted by the degree of stability of the reforming reaction.
[0056]
As a result, the time t between the case shown in FIG. 5B and the case shown in FIG.₁To time t_FourThe total value of the oxygen addition amounts up to is smaller in the case shown in FIG. Accordingly, since an excessive oxidation reaction of hydrogen generated in the reformer 3 is suppressed, the amount of hydrogen in the hydrogen-containing gas at the outlet of the carbon monoxide remover 5 is secured, and power generation in the fuel cell is stably performed. be able to.
[0057]
<3>
In the above embodiment, the case where oxygen is supplied only to the carbon monoxide remover 5 to perform selective oxidation of carbon monoxide has been described. However, a carbon monoxide removal catalyst is separately installed for other devices, Alternatively, selective oxidation of carbon monoxide may be performed. For example, the same equipment as the carbon monoxide remover 5 may be added to the fuel cell 6 so that the selective oxidation of carbon monoxide described in the above-described embodiment can be performed also in the fuel cell 6. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a hydrogen-containing gas generator.
FIG. 2A is a graph of the change over time of raw fuel, and FIG. 2B is a graph of the change over time of the number of moles of carbon monoxide and the number of moles of supplied oxygen.
FIG. 3 is a graph showing changes in the amount of carbon monoxide generated when the supply flow rate of raw fuel is changed.
FIGS. 4A and 4B are graphs of changes over time in the number of moles of carbon monoxide and the number of moles of oxygen supplied when the amount of increase in raw fuel per unit time is different.
FIG. 5A is a graph of the change over time of raw fuel, FIG. 5B is a graph of the change over time of the number of moles of carbon monoxide and the number of moles of oxygen supplied, and FIG. It is a graph of another time change of the number of moles of carbon, and the number of moles of oxygen supplied.
[Explanation of symbols]
1 Desulfurizer
2 Steam generator
3 Reformer
4 Transformer
5 Carbon monoxide remover
6 Fuel cell
7 Control unit

Claims (3)

Oxygen is added to the hydrogen-containing gas generated by reforming the raw fuel to selectively oxidize carbon monoxide contained in the hydrogen-containing gas, and the concentration of carbon monoxide in the hydrogen-containing gas An operation method of a hydrogen-containing gas generation device comprising a carbon monoxide remover that reduces the concentration to a predetermined concentration or less,
When a change in which the supply flow rate of the raw fuel to be subjected to the reforming process is increased takes a predetermined change period,
The ratio of the oxygen addition amount at a predetermined time during the change period and the predetermined period after the change period to the oxygen addition amount before the change start is the predetermined time with respect to the supply flow rate of the raw fuel before the change start. The oxygen addition amount during the change period and the predetermined period is adjusted to be larger than the ratio of the supply flow rate of the raw fuel ,
The oxygen addition amount after the predetermined period has passed is the ratio of the oxygen addition amount after the predetermined period with respect to the oxygen addition amount before the change start to the supply flow rate of the raw fuel before the change start. A method for operating a hydrogen-containing gas generation device, which is adjusted to an amount equal to a ratio of a supply flow rate of the raw fuel after a period . Oxygen is added to the hydrogen-containing gas generated by reforming the raw fuel to selectively oxidize carbon monoxide contained in the hydrogen-containing gas, and the concentration of carbon monoxide in the hydrogen-containing gas An operation method of a hydrogen-containing gas generation device comprising a carbon monoxide remover that reduces the concentration to a predetermined concentration or less,
When a change in which the supply flow rate of the raw fuel to be subjected to the reforming process is increased takes a predetermined change period,
The ratio of the oxygen addition amount at a predetermined time during the change period and the predetermined period after the change period to the oxygen addition amount before the change start is the predetermined time with respect to the supply flow rate of the raw fuel before the change start. The oxygen addition amount during the change period and the predetermined period is adjusted to be larger than the ratio of the supply flow rate of the raw fuel,
The length of the predetermined period is adjusted to a length expressed as a function of the ratio of the supply flow rate of the raw fuel at the end of the change period to the supply flow rate of the raw fuel before the start of the change or an equivalent amount thereof. Of operating a hydrogen-containing gas generator. The amount of oxygen added during the change period and the predetermined period is expressed as a function of the ratio of the supply flow rate of the raw fuel at the predetermined time to the supply flow rate of the raw fuel before the change start or an equivalent amount thereof. The operation method of the hydrogen-containing gas production | generation apparatus of Claim 1 or 2 adjusted to quantity .

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