JP5545496B2 - Method for estimating hydrogen permeation rate, hydrogen production apparatus and operation method thereof - Google Patents

Description

  The present invention relates to a method for estimating the permeation rate of hydrogen through a separation membrane, a hydrogen production apparatus using this method, and an operation method thereof.

  A hydrogen production apparatus that selectively extracts hydrogen from a hydrogen-containing gas is effective and suitable for efficient production of hydrogen gas fuel and the like. As the hydrogen separation membrane, as described in JP-A-2009-227487 (Patent Document 1), a Pd alloy thin film, an Nb alloy thin film, a pure Nb thin film, and the like are known.

  In Japanese Patent Laid-Open No. 2006-265076, a hydrogen-containing gas is supplied to a hydrogen production apparatus by a compressor, the pressure difference is set to 0.1 to 10 atm, particularly 1 to 5 atm, and the temperature is set to 20 to 650 ° C. , Hydrogen separation through a membrane is described (paragraph 0021).

JP 2009-227487 A JP 2006-265076 A

  In general, the higher the temperature and the greater the differential pressure between the primary side and the secondary side of the hydrogen production apparatus, the greater the amount of hydrogen permeating through the hydrogen separation membrane. Hydrogen permeation varies depending on the operating temperature.

  Conventionally, there has been no hydrogen separation membrane design method capable of obtaining a high hydrogen permeation amount even with a low hydrogen pressure difference.

As will be described later, the present invention reverses the conventional wisdom of using the hydrogen permeation coefficient φ and the original Fick's law and the Siebel's law when evaluating the hydrogen separation membrane, and uses the chemical potential difference. and proposed by the alloy design considering hydrogen bonding probability of the secondary chamber side, not possible with the conventional method, the design method of high accuracy hydrogen separation membrane obtained a high hydrogen permeation rate even with a low pressure difference To do.

  Although Group 5A metals such as Nb (niobium) and V (vanadium) have lower raw material costs and high hydrogen permeability compared to the most widely used Pd (palladium) hydrogen permeable alloys. Because of its high solute hydrogen concentration, hydrogen embrittlement is likely to occur, making it difficult to use as a hydrogen permeable membrane. However, hydrogen embrittlement can be avoided by adding an element that suppresses the solid solution hydrogen concentration such as W (tungsten) to the group 5A metal, and a high hydrogen permeation rate can be obtained by obtaining a large difference in hydrogen concentration. A hydrogen separation membrane capable of achieving both a high hydrogen permeation rate and hydrogen brittleness resistance can be obtained.

In Patent Document 1, by adding an element that suppresses the solid solution hydrogen concentration to Nb, hydrogen embrittlement can be avoided and a high hydrogen permeation rate can be obtained by obtaining a large difference in hydrogen concentration. A hydrogen separation membrane and a hydrogen separation method capable of obtaining a hydrogen separation membrane capable of achieving both permeation rate and hydrogen embrittlement resistance are described. As described above, conventionally, the hydrogen permeability of hydrogen separation membranes has been evaluated using the hydrogen permeability coefficient φ = DK (D: diffusion coefficient, K: Siebel coefficient), but in the case of Nb alloy, the Siebels rule cannot be applied. Therefore, in patent document 1, temperature and pressure conditions are determined using a PCT curve (pressure composition temperature curve), and hydrogen separation is performed. This method increases the rise of the PCT curve (pressure composition temperature curve) from the low pressure region while suppressing the concentration of the solid solution hydrogen, and makes the region with a gentle gradient (the region where hydrogen is stabilized and easily dissolved) more This is a technique for shifting to a high pressure (for example, 0.1 MPa in the case of Nb).
Fick's law J = D · ΔC / d (J: flux, D: diffusion coefficient, ΔC: hydrogen concentration difference (C is not H / M in Fick's law), d: film thickness) J = φ · Δ√P / d (P: hydrogen pressure, Δ√P: difference in square root of hydrogen pressure on both sides of the membrane), so far, the hydrogen permeation amount has been approximately the square root of hydrogen pressure with Pd alloys, etc. However, the test data revealed that the proportional relationship between the difference in the square root of the hydrogen pressure and the hydrogen permeation rate does not hold (see FIG. 14 (a)).

In the present invention, the hydrogen permeation rate is not Fick's law, but the equation using the chemical potential difference J = C ₁ · F · B · Δμ / d (C ₁ : primary chamber side solute hydrogen concentration, F: secondary Chamber side hydrogen bond probability, B: mobility, Δμ: chemical potential difference), and the value of potential difference Δμ is the hydrogen partial pressures P (Inlet) and P (Outlet) on the process side and permeate side. Therefore, it can be calculated as Δμ = RT / 2 × ln (P (Inlet) / P (Outlet)), and based on the knowledge that it can be calculated from the permeation condition (operating condition), the hydrogen of the hydrogen separation membrane It is an object of the present invention to provide a method capable of predicting the permeation rate with high accuracy, a hydrogen production apparatus employing the method, and an operation method thereof.

The method for estimating the hydrogen permeation rate of the present invention (Claim 1) is to provide a hydrogen permeation rate of the membrane in a hydrogen separation process in which a raw material gas is supplied to the primary chamber and hydrogen permeated through the hydrogen separation membrane is taken out from the secondary chamber. In the estimation method, the hydrogen partial pressure P _{1 in} the primary chamber, the hydrogen partial pressure P _{2 in the} secondary chamber and the temperature T, the hydrogen chemical potential difference Δμ between the primary chamber and the secondary chamber, and the hydrogen permeation rate J The hydrogen permeation rate estimation method for obtaining the hydrogen permeation rate from this relationship when the hydrogen partial pressure in the primary chamber is P ′ ₁ and the hydrogen partial pressure in the secondary chamber is P ′ ₂ The primary chamber side solid solution hydrogen concentration C ₁ determined by the material of the hydrogen separation membrane, the primary chamber hydrogen partial pressure P ₁ , the secondary chamber hydrogen partial pressure P _2, and the temperature T, and the secondary chamber a product C ₁ · F · Δμ the side of the hydrogen bond probability F and [Delta] [mu, the thickness d of the hydrogen permeation rate J and a hydrogen separation membrane To previously obtain a relation between the product of J · d, the hydrogen partial pressure in the primary chamber 'and _1, a hydrogen partial pressure of the secondary chamber P' P seek J · d value when the ₂ from the relationship The hydrogen permeation rate is obtained from the J · d value.

Estimation method of the hydrogen permeation rate of the present invention, an estimate of the hydrogen permeation rate ^{J (mol · m -2 · s} -2) J = C 1 · F · B · (RT / 2) · (ln (P ' ₁ / P' ₂ )) / d
Calculated in.

However,
C ₁ : concentration of dissolved hydrogen in the primary chamber B: hydrogen mobility: a constant determined by the temperature and the material of the membrane, and C when the pressure on the secondary chamber is sufficiently high so that the value of F becomes 1 _This is the slope of a straight line when ₁ · Δμ is plotted on the horizontal axis and J · d is plotted on the vertical axis.
F: 2 a primary chamber side hydrogen bonding probability, at a pressure region where hydrogen bonding is not rate limiting the hydrogen permeation is 1, K · C ₂ using secondary chamber side dissolved hydrogen concentration C ₂ is at a pressure area for the rate-limiting It can be expressed as ^4/9 .
K: proportional constant R: gas constant T: temperature (K)
P ′ ₁ : Hydrogen partial pressure in the primary chamber P ′ ₂ : Hydrogen partial pressure in the secondary chamber d: Film thickness (m)

When the pressure in the secondary chamber is low, hydrogen atoms that have permeated through the hydrogen separation membrane are less likely to form hydrogen molecules by binding on the surface of the hydrogen separation membrane, so the hydrogen bonding reaction becomes the rate-limiting step, It was experimentally shown that the hydrogen flow rate was lowered. For example, in the case of a Pd—Ag alloy, especially when the permeation side pressure is 120 kPa or less, the proportionality constant between J · d and C ₁ · Δμ does not match if the permeation side pressure conditions are different (see FIG. 14 (c)), It is necessary to consider the collision establishment of the hydrogen atoms in the secondary chamber on the two-dimensional surface of the bond, F = K · C ₂ ^4/9 (C ₂ : secondary chamber side solute hydrogen concentration). When the relationship between J · d and C ₁ · C ₂ ^4/9 · Δμ was examined in consideration of the secondary chamber side hydrogen bond probability, it became clear that the relationship was proportional. (See FIG. 14 (d)).

As the solid solution hydrogen concentrations C ₁ and C ₂ , a volume molar concentration (molH / m ³ ) may be used, or a molar fraction (H / (M + H)) may be used approximately. To calculate the volume molar concentration, it is necessary to take into account the volume expansion due to the solid solution of hydrogen, the thermal expansion of the lattice, the change in the lattice constant due to alloying, etc., and collect these basic data There is a need. On the other hand, the molar fraction can be easily determined from the atomic ratio (H / M) determined by PCT measurement.

  As this hydrogen separation membrane, Nb, Nb alloy, Ta, Ta alloy, V, V alloy or Pd, Pd alloy are suitable. Among them, Nb or Nb alloy membrane is suitable, but not limited thereto.

The operation method of the hydrogen production apparatus of the present invention (Claim 3 ) is a method of operating a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane, wherein the membrane area A (m ² ) and The gas pressure and temperature of the primary chamber and the secondary chamber are controlled so that the product J · A with the J value estimated by the method according to claim 1 or 2 becomes a target hydrogen extraction amount. To do.

  In the operation method of the hydrogen production apparatus, the pressure in at least the secondary chamber may be set to atmospheric pressure or lower. Even in the pressure in the primary chamber, the pressure may be lower than the atmospheric pressure as long as it is higher than the pressure in the secondary chamber.

The hydrogen production apparatus according to the present invention (Claim 5 ) is a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane, and the membrane area A (m ² ) and the hydrogen production apparatus according to claim 1 or 2 Gas pressure control means and temperature control means for controlling the gas pressure and temperature of the primary chamber and the secondary chamber so that the product J · A with the J value estimated by the above method becomes the target hydrogen removal amount. It is characterized by this.

When the present inventor conducted various experiments, the hydrogen permeation rate of the hydrogen separation membrane is linearly related to the difference Δμ in the chemical potential of hydrogen between the primary chamber and the secondary chamber, typically in a linear proportional relationship. For example, it was confirmed that the estimation was made with high accuracy by the above formula J = C ₁ · F · B · (RT / 2) · (ln (P ′ ₁ / P ′ ₂ )) / d.

  This estimated value is obtained when the Siebels law is applied to the conventional Fick's law (J = φ · Δ√P / d, where Δ√P is the difference between the hydrogen separation membrane and the square root of the hydrogen pressure on both sides, d is the film thickness, It was confirmed that φ was consistent with the measured value with higher accuracy than constant)).

  In the hydrogen production apparatus, since the material and film thickness d of the hydrogen separation membrane are determined in each apparatus, the ratio of the gas pressure on the primary side and the secondary side of the hydrogen production apparatus is a set value or a set range. By controlling the gas pressure on the primary side and the secondary side so that the temperature of the hydrogen production apparatus is controlled, the target hydrogen permeation rate can be obtained, and hydrogen can be produced at the target production volume. Hydrogen can be removed from the production equipment.

  According to the present invention, the condition (1) is set according to the present invention so that the potential difference between the primary side and the secondary side of the film is increased even under the condition of a low concentration difference, which has been conventionally considered to reduce the hydrogen permeation amount. A high hydrogen permeation amount can be obtained by operating the hydrogen production apparatus by setting the secondary side and secondary side hydrogen gas pressures). Therefore, according to the present invention, it is not always necessary to pressurize the process side of the hydrogen production apparatus to a high pressure with a compressor, and a highly efficient hydrogen production apparatus can be designed and manufactured.

  By setting the pressure in the secondary chamber to atmospheric pressure or less, leakage of hydrogen from the secondary chamber is prevented, and the gas pressure in the primary chamber is relatively low.

It is sectional drawing of the module for hydrogen permeation tests. It is the schematic which shows the module for hydrogen permeation tests arrange | positioned in an electric furnace. It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph showing the relationship between J · d value and ^{_{C 1 · C 2 4/9 · Δμ}} . It is a graph which shows a PCT curve. It is a graph which shows a PCT curve. It is a graph which shows a PCT curve. It is a graph which shows a PCT curve. It is a graph for demonstrating a hydrogen permeation characteristic. It is a flowchart of a hydrogen production apparatus.

  Hereinafter, the present invention will be described in more detail.

  The hydrogen separation membrane used in the present invention is preferably a group 5A metal of Nb, V, or Ta or an alloy thereof, Pd or a Pd alloy, and Nb or an Nb alloy is particularly preferable.

  Specifically, pure Nb, Nb—W alloy (W content 0.01-50 wt%), Nb—W—Mo alloy (W content 0.01-50 wt%, Mo content 0.01-50 wt%) ), Nb—Ru alloy (Ru content 0.01 to 50 wt%), Ta—W alloy (W content 0.01 to 50 wt%), V—W alloy (W content 0.01 to 50 wt%), Pd—Ag alloy (Ag content: 10 to 30 wt%) and the like are exemplified, but not limited thereto.

  The thickness of the metal or alloy film is preferably 1 to 500 μm, particularly about 10 to 50 μm, but is not limited thereto. In the case of a hydrogen separation membrane other than Pd or Pd alloy, a thickness of several tens to several hundreds nm made of Pd or Pd alloy (for example, Pd—Ag alloy (Ag content: 10 to 30 wt%)) is formed on both sides of the membrane. Form a layer.

  This hydrogen separation membrane may be superposed on a porous support or a support plate having grooves on the surface, or may be formed on the surface of the porous body. As a porous body, any of a metal material, a ceramic material, etc. may be sufficient.

  As a hydrogen production apparatus equipped with a hydrogen separation membrane, the hydrogen separation membrane is installed in a container called a housing, casing, vessel or the like, and has a primary chamber and a secondary chamber separated by a hydrogen separation membrane. The structure is not particularly limited as long as it further has heating means as required. The form of the film may be any form such as a flat film type and a cylindrical type.

  The raw material gas supplied to this hydrogen production apparatus may be any gas that contains hydrogen, such as a hydrocarbon steam reformed gas, a fuel cell off-gas, a biogas containing hydrogen, and a gas generated from a biomass gasification furnace. However, the present invention is not limited to this.

  The operating temperature of the device (specifically, the gas temperature on the primary side) is usually about 300 to 600 ° C., particularly about 400 to 550 ° C., although it depends on the composition of the film.

Gas pressure _{P 1} on the primary side is about 0.1~4.0MPa particularly 0.5~0.9MPa practical but not limited thereto. Gas pressure P ₂ on the secondary side, the hydrogen permeation rate of the target is determined by taking into consideration the primary pressure P ₁ so as to obtain preferred. Note that the gas pressure on the secondary side may be equal to or lower than the atmospheric pressure. In this way, hydrogen leakage from the secondary side is prevented, and the primary pressure P ₁ is relatively low.

  In the hydrogen permeation rate estimation method of the present invention, the raw material gas is supplied to the primary chamber, and the hydrogen permeation rate of the membrane when hydrogen is taken out from the secondary chamber is estimated.

Experimental data used as the basis for finding out this estimation method are shown in Examples 1 to 7 and FIGS. 3 to 9 later. 3 to 9 show that a pure Nb film or various alloy films are incorporated into the hydrogen permeation test module shown in FIGS. 1 and 2 and the temperature and the gas pressure in the primary chamber and the secondary chamber are variously changed to allow hydrogen permeation. Product J · d of hydrogen permeation rate J and hydrogen separation membrane thickness d when the velocity was measured, solid solution hydrogen concentration C ₁ , variable C ₂ ^{4/9 of} secondary hydrogen bond probability F, and chemistry it is a graph showing the relationship between the product ^_C 1 _{· C} ^{2 4/9} _· Δμ potential [Delta] [mu.

  First, the structure of the hydrogen permeation test module will be described with reference to FIGS.

  In this hydrogen permeation test module 1, a hydrogen separation membrane 4 is disposed between a rear end face of a gas introduction pipe 2 and a front end face of a gas extraction pipe 6 via gaskets 3 and 5. A nut 7 is fitted on the introduction pipe 2, and a cap nut 8 is engaged with a flange portion 6 a at the tip of the extraction pipe 6.

  The cap nut 8 is extended to the introduction tube 2 side, and a male screw on the outer peripheral surface of the nut 7 is screwed into a female screw on the inner peripheral surface. The leading end of the nut 7 comes into contact with the flange portion 2 a at the rear end of the introduction pipe 2, whereby the extraction pipe 6 is attracted to the introduction pipe 2 side through the cap nut 8, and the rear end surface of the introduction pipe 2 and the extraction pipe 6 are The hydrogen separation membrane 4 is sandwiched between the front end face via the gaskets 3 and 5.

  The gaskets 3 and 5 have an annular shape of the same size, and the area of the inner hole is the membrane permeation area A of the hydrogen separation membrane 4. The cap nut 8 is provided with a small hole 8a for a gas leak test.

In the module used in the examples described later, the inner hole of the gasket is 5.6 mm, but the diameter of the contact portion between the gasket and the membrane sample when tightened with the VCR is 7.1 mm, and the effective membrane permeation area A Is 39.6 mm ² (3.96 × 10 ⁻⁵ m ² ).

  The hydrogen permeation test module 1 is installed in an electric furnace 10 as shown in FIG. 2, the raw material gas is supplied to the introduction pipe 2, and the hydrogen gas is taken out from the extraction pipe 6.

  The gas pressures in the introduction pipe 2 and the extraction pipe 6 are detected by pressure sensors (not shown), respectively. This gas pressure is controlled by a pressure control valve or the like.

  As the source gas, high purity hydrogen having a purity of 99.99999% or more was used. The hydrogen gas that permeated the membrane 4 was recovered in a recovery container (not shown).

As detailed in the Examples 1-7, and the temperature of the furnace 10, the primary-side feed gas pressure P ₁ and the secondary side gas pressure P ₂ Various varied hydrogen permeation rate J and the hydrogen permeable membrane 4 The product J · d with the film thickness d is plotted on the vertical axis, and the solid solution hydrogen concentration C ₁ of the metal or alloy constituting the hydrogen permeable membrane 4 and the variable C ₂ ^{4 / 9} , the product C ₁ · C ₂ ^4/9 · Δμ with the difference Δμ in the chemical potential of hydrogen between the primary side and the secondary side is plotted on the horizontal axis. As shown in FIGS. It was found that there was a linear relationship between In addition,
Δμ = (RT / 2) · ln (P ₁ / P ₂ )
It is. Thus, since Δμ is marked as a logarithmic function of the pressure ratio, it is possible to realize a large Δμ even under low pressure conditions.

The solid solution hydrogen concentrations C ₁ and C ₂ can be obtained from the actual measurement values of the PCT measurement shown in FIGS. This solute hydrogen concentration is a value uniquely determined by the film composition, temperature and pressure.

As the solid solution hydrogen concentrations C ₁ and C ₂ , a volume molar concentration (molH / m ³ ) may be used, or a molar fraction (H / (M + H)) may be used approximately. To calculate the volume molar concentration, it is necessary to take into account the volume expansion due to the solid solution of hydrogen, the thermal expansion of the lattice, the change in the lattice constant due to alloying, etc., and collect these basic data There is a need. On the other hand, the molar fraction can be easily determined from the atomic ratio (H / M) determined by PCT measurement.

As shown in FIGS. 3 to 9, since a linear relationship exists between J · d and C ₁ · C ₂ ^4/9 · Δμ, the proportional constant B is used to determine that J · d = C ₁ · C ₂ ^4/9・ K ・ B ・ Δμ
Can be expressed as In the pressure region where the secondary chamber side hydrogen concentration is high and the hydrogen bond does not limit the hydrogen permeation, F = 1. By dividing both the left and right sides of this equation by d, the equation representing the hydrogen permeation rate J J = C ₁ .B・ Δμ / d
Is obtained. B is a constant representing the slope (gradient) of the straight line of each graph (FIGS. 3 to 9), and represents the ease of movement of hydrogen atoms in each film, so it is referred to as “mobility”. be able to. This mobility B is a value uniquely determined by the film composition and temperature.

In a pressure region where the hydrogen concentration on the secondary chamber side is high and hydrogen bonding does not control hydrogen permeation, the B value at each temperature is obtained by obtaining a linear relationship between J · d and C ₁ · Δμ in advance,
J = C ₁ · B · Δμ / d
= C ₁ · B · (RT / 2) · ln (P ₁ / P ₂ ) / d
J is calculated by substituting C ₁ value, B value, T value, and P ₁ / P ₂ value for.

  By multiplying the J value thus obtained by the membrane area A, the amount of hydrogen produced per unit time at the operating temperature T of the hydrogen production apparatus can be calculated.

In the present invention, it is also possible to directly determine the hydrogen permeation rate J from the P ₁ / P ₂ value without previously determining the B value and the C ₁ value.

That is, as shown in FIGS. 3 to 9, there is a linear relationship between C ₁ · C ₂ ^4/9 · Δμ and J · d, and the slope of this straight line is determined by the temperature of the hydrogen production apparatus.

Therefore, the relationship between C ₁ · C ₂ ^4/9 · Δμ and J · d shown in FIGS. 3 to 9 is determined for each material of the hydrogen separation membrane 4 at predetermined temperature increments. On the other _hand, calculates the chemical potential difference Δμ = (RT / 2) · ln (P 1 / P 2) from the value of P 1 / _{P 2,} and the [Delta] [mu, straight line shown in FIG. 3 - FIG. 9 at a temperature T J · d is obtained from the relationship. Since the d value (film thickness) is known, the hydrogen permeation rate J (mol · m ⁻² · s ⁻¹ ) can be obtained by dividing this J · d value by d.

  Further, by multiplying the J value by the membrane area A, the amount of hydrogen production per unit time can be predicted.

The relationship between the J · d value and the C ₁ · C ₂ ^4/9 · Δμ shown in FIGS. 3 to 9 is stored in the memory of the computer, and the P ₁ / P ₂ value or the P ₁ value and the P ₂ value are stored. The value may be input to a computer to calculate the J value and output it.

The temperature for obtaining the target hydrogen production amount, may be stored P ₁ value and P ₂ value (or P _{1 /} P ₂ value) in a memory of the computer, so that the target hydrogen production amount temperature, P ₁ The value and the P ₂ value (or P ₁ / P ₂ value) may be controlled.

  In the case of FIG. 3 (Nb), the temperature T is in increments of 20K, and in the case of FIG. 4 to FIG. 6 (Nb alloy), the temperature T is in increments of 50K. It is possible to estimate the hydrogen permeation rate with high accuracy. In the case of the temperature between the step sizes, for example, in the case of 703K for a pure Nb film, the straight line gradient or J · d value may be approximately calculated by proportionally dividing from the values of 693K and 713K. Also, the slope B (mobility) of each straight line in the graphs shown in FIGS. 3 to 6 is plotted on the vertical axis, and the reciprocal of each temperature (K) that is a parameter in FIGS. 3 to 6. Plotting on the horizontal axis (Arrhenius plot) gives an almost linear relationship. Since the relationship between the mobility and the temperature can be approximated by an exponential function in this way, the mobility for a specific temperature is calculated from the approximate expression, and J · d is calculated by integrating with c · Δμ. be able to. Thus, the J · d value at an unknown temperature can be calculated quantitatively.

  If the step size is made fine, the gradient value or J · d value can be obtained without a profound calculation, or approximate calculation can be performed with high accuracy.

  In the present invention, the configuration and structure of the hydrogen production apparatus are not particularly limited. Examples of the configuration of a hydrogen production apparatus that can be employed in the present invention are shown in FIGS. 15 (a), (b), and (c).

  In FIG. 15A, a raw material gas such as hydrocarbon is compressed by the compressor 21 and supplied to the hydrogen separation reformer 22. The hydrogen separation type reformer 22 includes a hydrogen reforming catalyst and a hydrogen separation membrane. The hydrogen separation type reformer 22 is supplied with steam from the boiler 24 and is given heat by the combustor 23 to perform reforming and hydrogen separation. Hydrogen from the hydrogen separation reformer 22 is taken out via the heat exchanger 25. The off gas is recovered by the heat exchanger 26 and then supplied to the combustor 23 via the pressure regulating valve 29. Heat is also recovered by the heat exchangers 27 and 28 from the combustion exhaust gas of the combustor 23 and the boiler 24, respectively. Heat supplied to the boiler 24, combustion air, fuel, and the like is performed by the heat recovered by the heat exchangers 25 to 28.

  In FIG. 15B, a hydrogen-containing gas containing hydrogen gas is supplied to the hydrogen separator 31, and the hydrogen separator 31 is heated by the combustor 32. The separated hydrogen is taken out through the heat exchanger 33. The off-gas is taken out through the heat exchanger 34, and a part or all of the off-gas is supplied to the combustor 32 through the pressure regulating valve 36 as necessary. The heat of the combustion exhaust gas is recovered by the heat exchanger 35. The fuel gas and air to the combustor 32 are heated by the recovered heat.

  In FIG. 15 (b), the combustor 32 is used. However, when there is a heat source that generates high-temperature waste heat, the high-temperature waste heat is guided to the heater 37 as shown in FIG. 15 (c). The hydrogen separator 31 may be heated.

  Examples 1 to 7 will be described below.

[Example 1 (pure Nb film)]
In the hydrogen permeation test module shown in FIGS. 1 and 2, a hydrogen separation membrane 4 having a thickness d = 0.5 mm made of pure Nb (purity 3N or more) was used.

693K The temperature of the furnace 10, 713K, 733K, 753K or a 773 K, a primary hydrogen partial pressure _{P 1} and the secondary side hydrogen partial pressure _{P 2} is variously changed, per unit time hydrogen permeation amount Q (mol / s The hydrogen permeation rate J (mol · m ⁻² .s ⁻¹ ) per unit membrane area was determined by dividing the Q value by the membrane area A (m ² ).

Further, at each temperature, the chemical potential difference Δμ = RT / 2 · ln (P ₁ / P ₂ ) between the primary side and the secondary side is calculated based on each P ₁ / P ₂ value. The solid solution hydrogen concentrations C ₁ and C ₂ on the primary chamber side and the secondary chamber side were obtained from the results of 10 PCT curves, and this C ₁ · C ₂ ^4/9 · Δμ and the J · d value were plotted. This is shown in FIG.

In FIG. 3 (a), the molar concentration (molH / m ³ ) is used as the solid solution hydrogen concentrations C ₁ and C ₂ . When C ₁ · C ₂ ^4/9 · Δμ is plotted on the horizontal axis and J · d is plotted on the vertical axis, these values indicate a proportional relationship, and the slope of the straight line indicates the mobility. FIG. 3 (b) uses the molar fraction (H / (M + H)) as the solid solution hydrogen concentrations C ₁ and C ₂ . As in FIG. 3 (a), C ₁ · C ₂ ^4/9 · Δμ and J · d are approximately proportional to each other, and the J · d value can be estimated even if the molar fraction is used as the solute hydrogen concentration. You can see that it is possible. The method using the mole fraction is simple and industrially useful as compared with the case of using the volume molar concentration (molH / m ³ ) requiring complicated calculation. Accordingly, in Examples 2 to 7 described later, molar fractions are used as the solid solution hydrogen concentrations C ₁ and C ₂ .

As shown in FIG. 3, there is a linear relationship between C ₁ · C ₂ ^4/9 · Δμ and J · d, and the slope of the straight line varies with temperature (ie, temperature is a parameter). This gradient was found to increase with increasing temperature T.

Therefore, if the relationship shown in FIG. 3 is obtained for each temperature, the J · d value is obtained from Δμ calculated from the T value and the value of P ₁ / P ₂ and the linear relationship of FIG. Since the d value (film thickness) is known, the hydrogen permeation rate J (mol · m ⁻² .s ⁻¹ ) is obtained by dividing this J · d value by the d value, and this J value is determined as the film area A Can be used to accurately estimate the amount of hydrogen produced per unit time under operating conditions where the operating temperature is T and the primary and secondary pressures are P ₁ and P _2. It became clear.

[Examples 2 to 7]
Nb-5Ru film (Example 2), Nb-5W film (Example 3), Nb-5W-5Mo film (Example 4), Ta-5W film (Example 5), V-5W film as hydrogen separation membranes (Example 6) A Pd-26Ag film (Example 7) was used, and tests were performed in the same manner as in Example 1 except that the temperatures were set as indicated in each figure. The relationship between the J · d value and the C ₁ · C ₂ ^4/9 · Δμ value is shown in FIGS.

Note that the solid solution hydrogen concentration C _1, C ₂ values for each alloy were used measured values. FIGS. 10 to 13 show the relationship (PCT curve) between the pressure (P), the solid solution hydrogen concentration (C) and the temperature (T) of pure Nb, Nb-5Ru, Nb-5W and Nb-5W-5Mo. Show.

As shown in FIGS. 4 to 9, it is recognized that a linear relationship exists between the J · d value and the C ₁ · C ₂ ^4/9 · Δμ value in Examples 2 to 7 as well. Further, as shown in FIGS. 3 to 6, the linear gradient increases as the temperature T increases.

Therefore, by obtaining the relationship shown in FIGS. 3 to 9 for each hydrogen separation membrane at different temperatures, Δμ calculated from the T value and the P ₁ / P ₂ value, and FIGS. The J · d value is obtained from the linear relationship in FIG. Then, this J · d value is divided by the d value to obtain a hydrogen permeation rate J (mol · m ⁻² .s ⁻¹ ), and the operating temperature is set to T by multiplying this J value by the membrane area A. It is possible to estimate with high accuracy the amount of hydrogen produced per unit time under the operating conditions in which the primary and secondary pressures are P ₁ and P ₂ .

DESCRIPTION OF SYMBOLS 1 Hydrogen permeation test module 2 Gas introduction pipe 3, 5 Gasket 4 Hydrogen separation membrane 6 Gas extraction pipe 7 Nut 8 Cap nut 10 Electric furnace 21 Compressor 22 Hydrogen separation type reformer 25-28, 33-35 Heat exchanger 31 Hydrogen separator

Claims (5)

In a method for estimating a hydrogen permeation rate of a membrane in a hydrogen separation process in which a raw material gas is supplied to a primary chamber and hydrogen that has permeated the hydrogen separation membrane is taken out from the secondary chamber.
Determined a primary chamber and a chemical potential difference of the hydrogen and the secondary chamber Δμ determined by the primary chamber of the hydrogen partial pressure P _1, the secondary chamber of the hydrogen partial pressure P ₂ and temperature T, the relationship between the hydrogen permeation rate J Leave
A hydrogen permeation rate estimation method for obtaining a hydrogen permeation rate from this relationship when the hydrogen partial pressure in the primary chamber is P ′ ₁ and the hydrogen partial pressure in the secondary chamber is P ′ ₂ ,
Solid solution hydrogen concentration C ₁ of the hydrogen material of the separation membrane and the hydrogen partial pressure P ₁ of the primary _chamber, the secondary chamber the hydrogen content of the pressure P ₂ and the primary chamber side determined by the temperature T, of the secondary chamber-side hydrogen bonding The relationship between the product C ₁ · F · Δμ of the probability F and Δμ and the product J · d of the hydrogen permeation rate J and the film thickness d of the hydrogen separation membrane is obtained,
From this relationship, the J · d value when the hydrogen partial pressure in the primary chamber is P ′ ₁ and the hydrogen partial pressure in the secondary chamber is P ′ ₂ is obtained.
It is this J · d values hydrogen permeation speed determined Ru estimation of hydrogen permeation rate method from the estimated value of the hydrogen permeation rate ^{J (mol · m -2 · s} -2)
J = C ₁ · F · B · (RT / 2) · (ln (P ′ ₁ / P ′ ₂ )) / d
The hydrogen permeation rate estimation method characterized by the above-mentioned calculation.
However,
C ₁ : concentration of dissolved hydrogen in the primary chamber B: constant determined by the temperature and the material of the membrane, and when the pressure on the secondary chamber is sufficiently high so that the value of F is close to ₁ , C ₁ · Δμ F is the slope of the straight line when plotting on the horizontal axis and J · d is plotted on the vertical axis F: The hydrogen bond probability of the secondary chamber, which is 1 in the pressure region where the hydrogen bond does not control hydrogen permeation, In the pressure-controlling pressure region, it can be expressed as K · C ₂ ^4/9 using the secondary chamber side solid solution hydrogen concentration C ₂ .
K: proportional constant R: gas constant T: temperature (K)
P ′ ₁ : Hydrogen partial pressure in the primary chamber P ′ ₂ : Hydrogen partial pressure in the secondary chamber d: Film thickness (m) 2. The method for estimating a hydrogen permeation rate according to claim 1, wherein the hydrogen separation membrane is made of Nb, Nb alloy, Ta alloy, V alloy or Pd alloy. In a method of operating a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane,
The gas pressures in the primary and secondary chambers so that the product J · A of the membrane area A (m ² ) and the J value estimated by the method according to claim 1 or 2 becomes a target hydrogen extraction amount. A method for operating a hydrogen production apparatus, wherein the temperature is controlled. 4. The method for operating a hydrogen production apparatus according to claim 3, wherein the pressure in at least the secondary chamber is set to atmospheric pressure or lower. In a hydrogen production apparatus having a primary chamber and a secondary chamber separated by a hydrogen separation membrane,
The gas pressures in the primary and secondary chambers so that the product J · A of the membrane area A (m ² ) and the J value estimated by the method according to claim 1 or 2 becomes a target hydrogen extraction amount. A hydrogen production apparatus comprising gas pressure control means and temperature control means for controlling temperature.

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