JP2008111419A - Oxygen separation gas turbine combined system - Google Patents

Abstract

The present invention provides an oxygen separation gas turbine combined system that improves energy efficiency by avoiding a decrease in oxygen separation efficiency due to the use of another temperature raising means for heating raw material air.
An oxygen separation device 1 for separating oxygen using a separation membrane made of an oxide ion permeable oxide and a gas turbine 9 are combined. Part or all of the high-pressure air generated in the compression unit 10 of the gas turbine 9 is heated by heat exchange, and high-purity oxygen is separated by the separation membrane. After the oxygen-depleted air after oxygen separation is heated using auxiliary heating means, it is used for heating high-pressure air and driving the gas turbine 9.
[Selection] Figure 1

Description

  The present invention relates to an oxygen separation gas that produces both oxygen and electric power by combining a gas turbine with an oxygen separation device that separates high-purity oxygen from air using a separation membrane made of an oxide ion-permeable oxide. The present invention relates to a turbine complex system.

  Oxygen separation technology using oxide ion permeable oxides separates two gases with different oxygen partial pressures, so that oxygen is oxidized in the form of oxide ions from the high oxygen partial pressure side to the low side. It is based on a phenomenon that penetrates inside. Among the oxide ion permeable oxides, in the case of mixed conductive oxides having both electron conductivity, the balance of charges accompanying the movement of oxide ions is compensated by the movement of electrons, so that oxygen can be removed without an external circuit. It has the feature that permeation persists.

  The difference in oxygen partial pressure, which is the driving force for oxygen separation, is realized by, for example, compressing the oxygen-containing mixed gas (air, etc.) to increase the oxygen partial pressure to normal pressure or lowering the separation side Is done. In addition, the oxygen separation rate is proportional to the absolute temperature, and the oxide ion conductivity itself of the separation membrane material increases as the temperature rises. Therefore, the oxygen separation rate can be increased as the temperature increases. However, since the metal material to be used is limited in the high temperature range, a temperature range of 700 ° C. to 950 ° C. is usually selected.

  One characteristic of oxygen separation technology using oxide ion-permeable oxides is high-purity oxygen separation. In order to increase the efficiency of oxygen separation, the thickness of the separation membrane is made as thin as possible. This is because, in principle, only oxygen can permeate if a thin film without defects through which gas molecules can pass is formed. Another feature is the possibility of inexpensive oxygen production. By supplementing the energy required for high temperature and high pressure of the raw material air by recovering energy from the exhaust gas, the power required per unit volume (electric power consumption) is reduced to oxygen PSA (Pressure Swing Adsorption), which is an existing oxygen production facility. ) And based on the trial calculation results that it can be lower than cryogenic separation.

  One of the reasons why these two features are not yet in practical use is that energy efficiency has not reached the expected level.

  One method for improving energy efficiency is a method of using heat exchange with exhaust gas for raising the temperature of the raw material air. However, a normal heat exchanger has a problem that it is a multi-pipe heat exchanger having many fins in order to increase the heat transfer area and increase the heat exchange efficiency, and is extremely expensive. In addition, since the heat transfer medium is a metal, the temperature obtained by heat exchange is up to about 500 ° C., and in order to raise the temperature to 700 ° C. or higher necessary for oxygen separation, it is necessary to take another temperature raising means. there were.

  On the other hand, a heat storage type heat exchanger using a ceramic honeycomb or ball as a medium and utilizing heat storage and heat dissipation is known. For example, Patent Document 1 discloses that economic efficiency can be improved by using a regenerative heat exchanger for heat exchange with exhaust gas emitted from a power generation unit for heating air or fuel gas of a high-temperature fuel cell. Yes. Patent Document 2 discloses a system that uses a regenerative heat exchanger to effectively use the amount of heat held by a high-temperature gas such as a product gas of a coal gasifier in the system. Application to oxide fuel cells (SOFC) is described.

  In the case of a fuel cell, since the power generation involves an exothermic reaction, the exhaust gas temperature is higher than the raw material gas temperature. Accordingly, in the field of fuel cells, it is not always necessary to provide another temperature raising means by using a heat storage type heat exchanger. On the other hand, in the case of oxygen separation, there is no exothermic reaction like a fuel cell, and conversely there is heat dissipation outside the system, so the exhaust gas (oxygen-poor air) is always lower in temperature than the raw material gas (air). . Therefore, even if the heat storage type heat exchanger is used, the heating of the raw material gas is still insufficient, and it is necessary to compensate for the shortage by another means. Conventionally, it has been common to separate the heat recovery of the exhaust gas and the heating of the source gas in order to make the oxygen separation device simple.

  As another method for raising the temperature of the raw material air, a method of mixing the fuel with the raw material air and burning it is known in addition to the method of electrically heating as the simplest method. However, economical merits cannot be sufficiently enjoyed by the method of electrically heating, and the method by combustion of raw material air is not necessarily an effective method for the reasons described below.

  In other words, in the case of oxygen separation, unlike the oxide fuel cell and the membrane reactor, a decrease in oxygen concentration due to combustion of raw material air appears remarkably. In the field of oxide fuel cells and membrane reactors, raw material air is used as an oxygen supply source, and fuel such as hydrogen or hydrocarbon gas is supplied on the opposite side across an oxide ion permeable oxide. Since the driving force for the movement of oxide ions is proportional to the logarithm of the oxygen partial pressure ratio on both sides, the moving speed of oxide ions is almost determined by the state of the fuel side surface where the oxygen partial pressure is extremely low. Therefore, it can be said that the oxygen partial pressure on the raw material air side is hardly reflected. On the other hand, in the case of oxygen separation, when obtaining oxygen at normal pressure, the oxygen partial pressure on the permeate side is constant at 0.1 MPa, which significantly reflects the state of the oxygen partial pressure on the feed air side. .

For easy understanding, it is assumed that the oxygen concentration in the raw material air is reduced from 21% to 16% by the temperature raising method by the combustion of the raw material air. For oxide fuel cells and membrane reactors, assuming the oxygen partial pressure on the fuel side surface is 1.0 × 10 ⁻¹⁰ MPa,
1 − [Ln (0.016 / 10 ^-10 ) / Ln (0.021 / 10 ^-10 )] = 0.014
As a result of the decrease in oxygen concentration, the transfer speed is only decreased by 1.4%. On the other hand, in the case of oxygen separation, if the pressure of the raw material air is 1.0 MPa,
1 − [Ln (0.16 / 0.1) / Ln (0.21 / 0.1)] = 0.36
This is a 36% decrease.

  As described above, although it is effective in the field of oxide fuel cells and membrane reactors, the method of raising the temperature by mixing the fuel with the raw air and combusting has the problem that the separation efficiency is greatly reduced in the case of oxygen separation. there were.

  Further, a method of connecting a gas turbine is known as a method for recovering high-temperature and high-pressure energy of oxygen-poor air discharged by oxygen separation. For example, as described in Patent Document 3 and Patent Document 4 filed previously by the present inventors, the high-pressure air generated in the compression section of the gas turbine is once branched into the oxygen separation section and the oxygen poor discharged from the oxygen separation section. This is a method for returning converted air to the turbine section. The gas fluid for driving the turbine decreases due to the oxygen separation, and the power generation amount decreases.However, since the reduced power generation amount can be regarded as the amount of power required for the oxygen separation, the total energy is taken into account as a combined production system of oxygen and power. Efficiency is improved.

  However, since the temperature range necessary for oxygen separation is lower than the gas turbine driving temperature, the oxygen-poor air returned to the turbine section drives the expansion turbine through a combustion process inside the gas turbine. That is, the high-temperature and high-pressure air necessary for driving the turbine is not used for heating the raw material air, and it is necessary to take another temperature raising means in order to heat the raw material air to a temperature necessary for oxygen separation.

  In the field of oxide fuel cells similar to oxygen separation, for example, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9, and Patent Document 10 are disclosed in Japanese Patent Application Laid-Open An energy recovery method is disclosed. As described above, since the exhaust gas temperature is higher than the raw material gas temperature, it is not always necessary to provide a temperature raising means. Even if a heating method based on combustion of raw material air is applied as another temperature raising means, the fuel cell does not have a great influence as described above. That is, although the technologies disclosed in the field of fuel cells are technologies specific to fuel cells, these technologies cannot be applied to oxygen separation as they are.

JP-A-7-135014 JP-A-11-223482 JP 2005-281027 A JP 2005-28297 A JP-A-3-286150 JP-A-8-45523 Japanese Patent Laid-Open No. 10-297901 JP 2003-254004 A JP-A-2005-1993 JP 2006-100223 A

  The present invention has been made as a result of aiming at the development of a system related to an oxygen separation apparatus excellent in energy efficiency in view of the above-mentioned problems. In other words, we reviewed the system that connects the gas turbine to the oxygen separation technology using oxide ion conductive oxide, which is a high temperature process, and avoided the decrease in oxygen separation efficiency due to the use of another heating means for heating the raw air The purpose is to improve energy efficiency.

The gist of the present invention for solving the above-mentioned problems is as follows.
(1) A system in which an oxygen separation device that separates oxygen using a separation membrane made of an oxide ion permeable oxide and a gas turbine are combined, and the high-pressure air generated in the compression section of the gas turbine A part or the whole is heated by heat exchange, high-purity oxygen is separated by the separation membrane, and oxygen-depleted air after oxygen separation is heated using an auxiliary heating means. An oxygen-separated gas turbine combined system characterized by being used for heating and driving of the gas turbine.

(2) The oxygen-separated gas turbine combined system according to (1), wherein the auxiliary heating unit is a heating unit that mixes fuel with the oxygen-poor air and uses combustion heat of an oxidation catalyst.
(3) The oxygen-separated gas turbine combined system according to (1) or (2), wherein a heat storage heat exchanger is included as means for heating the high-pressure air by heat exchange of the oxygen-poor air.
(4) The oxygen-separated gas turbine combined system according to any one of (1) to (3), wherein the temperature of the high-pressure air heated by the heat exchange is 700 ° C. or higher and 950 ° C. or lower.
(5) A combined heat generation is performed by the gas turbine and the steam turbine by connecting an exhaust heat recovery boiler to the exhaust port of the gas turbine and driving the steam turbine. ) Any oxygen separation gas turbine combined system.
(6) The oxygen separation gas turbine combined system according to any one of (1) to (5), wherein a pressure reducing means is provided on the oxygen separation side.
(7) The oxygen-separated gas turbine combined system according to any one of (1) to (6), wherein the oxide ion-permeable oxide is substantially a cubic perovskite oxide.

  According to the present invention, since the high-temperature and high-pressure energy of oxygen-poor air is effectively used, the decrease in oxygen concentration in high-pressure air can be reduced, realizing a high oxygen transmission rate and reduction in power consumption. Is done. As a result, in addition to high-purity oxygen production, which is a feature of oxygen separation using solid electrolyte oxide, low-cost oxygen production that has conventionally been pointed out on the desk is actually possible.

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a system in which an oxygen separator and a gas turbine are combined as a preferred embodiment of the present invention. This is because part or all of the high-pressure air generated in the compression section of the gas turbine is heated by heat exchange, and high-purity oxygen is separated by the oxygen separation pipe. The oxygen-poor air after separation is further heated by using auxiliary heating means, and then is an oxygen separation gas turbine combined system used for heating high-pressure air and driving a turbine. Details of this system will be described below with reference to FIG.

  A plurality of oxygen separation tubes 4 are placed in the separation device main body 1 so as to separate the space 2 and the space 3. The oxygen separation tube 4 has a structure in which an ultrathin film is formed on a porous support tube, and has a strength for maintaining a pressure difference generated between the space 2 and the space 3 in the porous support tube portion. The actual oxygen separation is performed in the thin film portion. The thicknesses of the porous support tube and the thin film are appropriately selected based on the following viewpoints. The porous support tube needs to have a certain thickness or more in consideration of the pressure difference to be held. On the other hand, if the thickness is too large, ventilation resistance is generated and the oxygen transmission rate is lowered. Generally, it is selected in the range of 0.5 mm to 10 mm. The thinner the thin film, the more advantageous it is to increase the oxygen permeation rate. However, if the film is too thin, the gas easily escapes through the defective portion, which causes a decrease in the purity of the separated oxygen. Generally, it is selected in the range of 1 μm or more and 1 mm or less.

  Since a plurality of oxygen separation tubes 4 are placed on the separation device main body 1 so as to separate the space 2 and the space 3, not only gas leakage by the separation tube main body but also a place for holding the separation tube (not shown) In this case, a complete gas seal is applied. In the space 2 and the space 3, the oxygen partial pressure in the space 2 is always higher than the oxygen partial pressure in the space 3, and oxygen permeates from the space 2 to the space 3. For example, a combination of space 2 / space 3 = high pressure air / normal pressure oxygen or high pressure air / depressurized oxygen. Here, a case where atmospheric pressure oxygen is separated from high-pressure air will be described.

  The raw air 6 is taken into the compression section 10 of the gas turbine 9 and the high-pressure air whose temperature has been increased by the amount corresponding to adiabatic compression enters the heat exchanger 6 and is further heated. Oxygen separation is performed in the separator main body 1, and the separated oxygen is recovered from the oxygen discharge port 5. The oxygen-depleted air is further heated by the combustor 8 after being mixed with the fuel 7 and returned to the expansion turbine section 11 of the gas turbine via the heat exchanger 6.

  The combustor 8 may be of a burner type that emits a normal flame, but the flame disappears unless measures are taken to maintain stable combustion using oxygen-depleted air with a reduced oxygen concentration. It may not be true. As a means for easily realizing stable combustion of oxygen-poor air, a catalytic combustor using a catalyst that promotes fuel oxidation is preferably used. This raises the temperature by oxidation heat on the surface of the catalyst without generating a flame, and is maintained at a temperature necessary for the expression of catalytic ability by the oxidation heat, so that continuous combustion is possible. In addition, since a fuel supply amount is automatically controlled by monitoring a thermometer installed in the vicinity of the catalyst, stable temperature control is performed.

Next, as a more desirable embodiment, an example in which a regenerative heat exchanger is used as means for heating high-pressure air by heat exchange of oxygen-poor air is shown in FIG. 2, and the composite system will be described according to this.
The high-pressure air generated in the compressor 10 of the gas turbine enters the heat storage heat exchanger 16A through the open / close valve 15A. Heat is received from the medium stored in the previous stage, heated to a temperature at which oxygen can be separated, and then introduced into the space 2 of the separation apparatus body 1. Oxygen is recovered from the oxygen outlet 5. The oxygen-poor air is mixed with the fuel 7 supplied through the opening / closing valve 18B and heated by the heater 8B, and then is cooled while raising the temperature of the medium of the heat storage heat exchanger 16B, and the opening / closing valve 17B. And is returned to the expansion turbine section 11 of the gas turbine.

  When the medium of the heat storage heat exchanger 16B is sufficiently heated (heat storage), the opening / closing valves 15A, 15B, 17A, and 17B are operated to switch the flow path pattern. Simultaneously with the switching of the flow path pattern, the opening / closing valve 18B is closed and 18A is opened, thereby operating the heater 8A and heating the heat storage medium of the heat storage heat exchanger 16A.

If the high-pressure air can be raised to a temperature capable of oxygen separation of 700 ° C. or more and 950 ° C. or less by the heat storage heat exchanger 16A or 16B, it is not necessary to use auxiliary heating means before the oxygen separation, and in the raw material air Therefore, it is more desirable as a complex system. However, even if the temperature is less than 700 ° C., the amount of oxygen consumed for the temperature increase is small, so even if some auxiliary heating means is used in combination, it does not depart from the present invention.
Next, a system configured as a combined power generation of a gas turbine and a steam turbine will be described. FIG. 3 is an example in which a steam turbine is added to the system of FIG. 1 and will be described below with reference to FIG. 3, but a steam turbine can also be added to FIG.

  The exhaust gas 13 discharged from the gas turbine has heat in a medium temperature range such as 300 ° C. to 500 ° C., for example, so that steam is generated in the exhaust heat recovery boiler 19 using this exhaust heat, and the steam turbine 20 Drive. As a result, the combined power generation of the gas turbine and the steam turbine can be performed, and the energy efficiency can be further increased.

  Note that the gas turbine combined with the oxygen separator is appropriately selected depending on the scale of the oxygen separator. For smaller scales, a micro gas turbine may be used.

  In the above-described oxygen separation gas turbine combined system, the separated oxygen side can be separated under reduced pressure. For this purpose, an appropriate pressure reducing means connected to the oxygen separation side (space 3) is provided. Although recovery of energy required for decompression is difficult, the driving force for oxygen permeation increases, so that the target oxygen can be separated with fewer oxygen separation tubes. In addition, when a micro gas turbine is used in a small-scale system, the pressure of the raw material air generated from the compression unit may be insufficient. In such a case, the merit of reducing the pressure on the separated oxygen side is particularly large. . In any case, whether to depressurize the separation side may be determined in consideration of the total oxygen production cost.

Oxide ion permeable oxides used in the oxygen separation gas turbine combined system include bismuth oxide, ceria, zirconia, perovskite oxide, pyrochlore oxide, etc., at 10 ⁻² Scm ⁻¹ or more at 850 ° C. An oxide having the following oxide ion conductivity is preferably used. Among them, a substantially cubic perovskite oxide having a high oxide ion conductivity is most preferably used. Here, the term “substantially” means that even a perovskite oxide that is approximately cubic crystal is actually limited to a cubic perovskite oxide because the crystal structure is actually slightly distorted. It is not.

The oxygen separation gas turbine combined system shown in FIG. 1 and the conventional gas turbine-equipped system (comparative example) shown in FIG. 4 were used, and the oxygen production power intensity in each case was compared. The oxygen separation apparatus performed oxygen separation at 850 ° C. The results are shown in FIG. FIG. 5 is a plot of the oxygen production rate on the horizontal axis and the power generation amount on the vertical axis. In both cases, a decrease in power generation amount was observed as the oxygen production amount increased. oxygen production unit power consumption, in conventional systems, the electric power consumption rate 0.28kW time / m ³ - the oxygen, in the system according to the present invention, the 0.22 kW during / m ³ - was found to be oxygen. Thus, it was confirmed that the present invention can reduce power by 21%.

It is a specific example of the preferable oxygen separation gas turbine combined system of this invention, Comprising: It is a figure which shows the oxygen separation gas turbine combined system which heats oxygen-poor air, heats high pressure air, and drives a turbine. FIG. 2 is another preferred specific example of the combined system shown in FIG. 1, and is a view showing an oxygen separation gas turbine combined system using a heat storage type heat exchanger for heat exchange. FIG. 5 is a view showing still another preferred specific example of the combined system shown in FIG. 1, and an oxygen separation gas turbine combined system that performs combined power generation of a gas turbine and a steam turbine using exhaust gas discharged from the gas turbine. . It is a figure which shows the conventional typical gas turbine coexisting system used in order to compare oxygen production electric power intensity. It is the figure which showed the relationship between the oxygen production amount and electric power generation amount of the composite system by this invention, and a conventional system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxygen separator main body 2 Space between oxygen separation pipe outer surface and oxygen separator main body 3 Space between oxygen separation pipe inner surface and oxygen separator main body 4 Oxygen separation pipe 5 Separation oxygen outlet 6 Heat exchanger 7 Fuel 8 Combustion 8A Combustor A
8B Combustor B
9 Gas Turbine 10 Compressor 11 Expansion Turbine 12 Raw Material Air 13 Exhaust Gas 15A Open / Close Valve A (For Raw Air)
15B Open / close valve B (for raw air)
16A Regenerative heat exchanger A
16B Regenerative heat exchanger B
17A Open / close valve A (for oxygen-poor air)
17B Open / close valve B (for oxygen-poor air)
18A Fuel valve A
18B Fuel valve B
19 Waste heat recovery boiler 20 Steam turbine 21 First combustor 22 Second combustor

Claims (7)

A system in which an oxygen separation device that separates oxygen using a separation membrane made of an oxide ion permeable oxide and a gas turbine are combined,
Part or all of the high-pressure air generated in the compression section of the gas turbine is heated by heat exchange, high-purity oxygen is separated by the separation membrane, and oxygen-depleted air after oxygen separation serves as auxiliary heating means. An oxygen-separated gas turbine combined system, wherein the combined system is used for heating the high-pressure air and driving the gas turbine after the temperature is raised.   2. The oxygen separation gas turbine combined system according to claim 1, wherein the auxiliary heating unit is a heating unit that mixes fuel with the oxygen-poor air and uses combustion heat of an oxidation catalyst.   The oxygen-separated gas turbine combined system according to claim 1, wherein a heat storage heat exchanger is included as means for heating the high-pressure air by heat exchange of the oxygen-poor air.   The oxygen-separated gas turbine combined system according to any one of claims 1 to 3, wherein a temperature of the high-pressure air heated by the heat exchange is 700 ° C or higher and 950 ° C or lower.   5. The combined power generation is performed by the gas turbine and the steam turbine by connecting an exhaust heat recovery boiler to an exhaust port of the gas turbine and driving the steam turbine. The oxygen separation gas turbine combined system according to item.   6. The oxygen separation gas turbine combined system according to claim 1, further comprising a decompression unit on an oxygen separation side.   The oxygen-separated gas turbine combined system according to any one of claims 1 to 6, wherein the oxide ion-permeable oxide is substantially a cubic perovskite oxide.

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