JPH06226099A - Composite catalyst body for high-temperature combustion - Google Patents

Abstract

PURPOSE:To maintain combustion performance in the case an inlet temp. is lowered by providing the catalyst bodies deposited with catalyst components mainly composed of platinum which is lower in low-temp. activity than palladium catalysts but is higher in low-temp. activity than manganese substitution type hexa-aluminate catalysts as an intermediate layer of the composite catalyst body. CONSTITUTION:The first catalyst bodies A and B formed by depositing the catalyst active components mainly composed of the palladium having the highest activity to methane on heat resistant honeycomb base bodies of cordierite, etc., then the second catalyst bodies C formed by depositing the catalyst active components mainly composed of the platinum on heat resistant honeycomb base bodies and further, the third catalyst bodies D, E, F and G formed by directly molding the manganese substitution type hexa-aluminate as honeycombs are successively arranged in the formost part where a gaseous mixture 11 composed of gaseous fuel and air flows in. The respective catalysts realize the highest catalyst activity while maintaining the long-term activity in the respective temp. regions from low to high temps. with such combination.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to nitrogen oxides (NO _x ).
The present invention relates to a composite catalyst body for catalytic combustion, which is used in a combustor such as a gas turbine in order to suppress the generation of gas.

[0002]

2. Description of the Related Art A gas turbine cogeneration system that uses natural gas as a fuel, a combined gas turbine power generation system for power generation, and the like can significantly improve thermal efficiency, and thus can save resources and energy. Is being watched as. In these systems, it is an indispensable condition to significantly reduce the amount of NO _x generated in order to prevent environmental pollution. Currently, as a method of significantly reducing the amount of NO _{x in} the exhaust gas from a gas turbine,
The selective catalytic reduction method with ammonia (SCR method) has reached the stage of practical application. However, this NO _x reduction method has the problems that (a) the use of ammonia, which is a dangerous substance, is essential, and (b) the initial cost and running cost are high. Law is drawing attention.

The catalytic combustion method is, for example, Japanese Patent Publication No. Sho-53-374.
As disclosed in Japanese Patent Publication No. 85, a lean premixture of fuel and air is heated to 1500 ° C. using a honeycomb-shaped combustion catalyst.
The following is a method of stably burning and significantly reducing the generation of NO _x . A typical configuration example of a gas turbine combustor to which this combustion method is applied is shown in FIG. The entire combustor is mainly composed of a precombustor 1, a premixer 3, a catalyst cassette 5 and a bypass air valve 7. The precombustor 1 is composed of a normal flame combustion burner, operates at a high combustion amount when the turbine starts, and preheats the air introduced into the combustor to the catalytic combustion start temperature during steady state, so that low combustion is performed. Operated in quantity. The premixer 3 mixes the preheated air C with the main fuel A to form a uniform air-fuel mixture.
Since the catalyst cassette 5 has a structure in which a plurality of honeycomb-shaped fuel catalyst bodies divided in the axial direction are loaded and fixed by a metal frame, the lean premixed gas formed by the premixer 3 is stably combusted in the catalyst layer, generation of the NO _x is greatly suppressed. The bypass air valve 7 is used to supply air for adjusting the inlet temperature (combustion exhaust gas temperature) of the turbine T and the maximum temperature of catalytic combustion. In order to realize a catalytic combustor having such a structure, it is necessary to develop a combustion catalyst that satisfies the following requirements.

(1) Combustion can be started from the lowest possible inlet temperature. The temperature of the air introduced into the gas turbine combustor is about 300 ° C. The lower the catalytic combustion start temperature, the more the pre-combustion amount can be reduced and the total NO _x amount can be reduced. The goal of reducing the amount of NO _x in the catalytic combustor is
About one-tenth or less of _the amount of NO _x reduction No measures turbine, 40p
Ultra low NO _{x of} pm (converted to 0% oxygen) should be achieved, and in order to achieve that, the catalyst inlet temperature needs to be 450 ° C. or lower.

(2) The catalyst outlet temperature is required to be higher than the operating maximum temperature of the current cogeneration gas turbine, which is about 1100 ° C. If the temperature is lower than that, the energy efficiency is lowered and the practicality is lost.

(3) A combustion efficiency of 99% or more is achieved at the catalyst outlet.

(4) The linear velocity passing through the catalyst layer should be at least 3 m / s in terms of an empty cylinder at an operating pressure of 10 ata and 0 ° C. The smaller the flow velocity is, the larger the combustor needs to be in order to increase the throughput, and the practicality is lost.

(5) The pressure loss rate of the catalyst layer is 3% or less. Higher pressure loss rates reduce turbine efficiency.

(6) The catalyst active life should be at least 8000 hours or more for practical use.

The present inventors have already developed a composite catalyst as a combustion catalyst that meets the above conditions (see Japanese Patent Laid-Open No. 4-161253). In this composite catalyst body, a first catalyst body having a catalyst component mainly composed of palladium supported on a heat-resistant honeycomb substrate and a manganese-substituted hexaaluminate are directly formed into a honeycomb stream from the inlet side through which the air-fuel mixture is introduced. It has a structure in which a plurality of second catalyst bodies are arranged.

The present inventor then conducted a turbine mounting test using a 150 KW class turbine with a pressure ratio of 8.5 on a catalytic fuel unit of the type shown in FIG. 1 using a catalyst having a diameter of 220 mm, and further conducted an experiment. As a result of advancing research on combustion activity in the chamber, the above-mentioned composite catalyst (1)
It has been found that it is rather difficult to achieve the conditions of (4) and (4).

As a result of further study on the cause of this, the present inventor has found that the manganese-substituted hexaaluminate catalyst arranged in the downstream of the composite catalyst body maintains sufficient combustion progress under the high pressure condition of the turbine. 8 to do
An inlet temperature of 00 ° C. or higher is required, while it is difficult to stably achieve an outlet temperature of 800 ° C. or higher with a palladium catalyst arranged in the upstream, and as a result,
It was found that the difference in the activities of the two catalysts makes it difficult to maintain the combustion performance when the inlet temperature is reduced.

[0013]

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to solve the problems of the conventional composite catalyst body composed of the first catalyst body and the second catalyst body.

[0014]

Means for Solving the Problems The present inventor has conducted extensive studies in view of the problems of conventional composite catalysts, and as a result, the low temperature activity is lower than that of the palladium catalyst as the intermediate layer of the composite catalysts. , A composite catalyst body having a catalyst body having a platinum-based catalyst component supported on a heat-resistant honeycomb substrate having higher activity at a low temperature than a manganese-substituted hexaaluminate catalyst has a function meeting the above-mentioned object. I found that.

That is, the present invention provides a composite catalyst body having the following structure: A composite catalyst body for high temperature combustion used in a device for catalytically burning a fuel gas-air mixture, comprising: (1) a catalytic activity mainly composed of palladium on a heat-resistant honeycomb substrate, which is located at an inlet side into which the mixture gas flows. First carrying component
A catalyst body of (2), which is located on the downstream side and has a heat-resistant honeycomb substrate on which a catalytically active component mainly composed of platinum is carried.
And (3) a plurality of third catalyst bodies which are located on the further downstream side thereof and which are formed into a honeycomb shape of manganese-substituted hexaaluminate. .

The composite catalyst body according to the present invention comprises a first catalyst body located on an inlet side into which a fuel gas-air mixture flows,
It comprises a second catalyst body located on the downstream side and a third catalyst body located on the downstream side. Below, each catalyst body is demonstrated in detail.

First Catalyst Body The first catalyst body has a honeycomb substrate made of a heat-resistant material, which carries palladium as a catalytically active component and nickel oxide as a co-catalyst if necessary, and further as a carrier component. Lanthanum oxide and / or barium oxide and / or silicon oxide-containing alumina.

The honeycomb substrate is not particularly limited as long as it has heat resistance up to about 1200 ° C., but it can be obtained as a mass-produced product at low cost, has a low coefficient of thermal expansion, and has a thermal shock resistance. Those made of high cordierite are preferred. The opening ratio and the number of cells per square inch are not particularly limited, but in order to make the active area and the pressure loss during combustion appropriate while supporting the catalytically active component, 60 to 70% and It is preferable to set it to about 100 to 200 cells / 1 square inch.

The first catalyst body carries 50 to 150 g / l of palladium as a catalytically active component, based on the honeycomb volume, and, if necessary, 20 to 20 parts of nickel oxide.
Carries 70 g / l. Palladium has the highest methane oxidation activity, which is the main component of natural gas, and functions as the main catalyst for reducing the catalyst inlet temperature as much as possible. Generally, the larger the supported amount of palladium, the better the stability of the catalytic activity, but the maximum supported amount is determined within the above range in consideration of factors such as physical limit and cost. To be Nickel oxide used as needed is
It functions as a co-catalyst that controls the thermal stability of the activity of the palladium catalyst to some extent. In order to achieve the same purpose, MgO, Ce ₂ O ₃ , ZrO ₂ or the like may be added instead of nickel oxide or together with nickel oxide.

The first catalyst body further carries 50 to 200 g / l of alumina containing lanthanum oxide as a carrier component of the catalytically active component on the basis of honeycomb volume. As the carrier component, 50 under heating conditions of 1100 ° C. for 5 hours
Other substances may be used as long as they maintain a specific surface area of m ² / g or more. Such materials include alumina containing barium oxide and / or silicon oxide. Lanthanum oxide, barium oxide, and silicon oxide all have the function of preventing the crystal growth of porous intermediate alumina made of a polycrystalline body and maintaining a high specific surface area. , Alumina weight 3 to
It is about 25%. Since such a carrier component covers the wall surface of the honeycomb substrate with the catalytically active component in a dispersed state and is porous and has a high specific surface area, it facilitates the diffusion of the reactant into the catalytically active component.

The first catalyst body can be prepared by various methods and is not particularly limited. For example, palladium, which is a catalytically active component, is easily sintered and particles grow under combustion conditions, so the particle diameter is 0.02 to 1.5 μm.
Used as metal particles in the range of about m, if necessary, an amorphous powder such as nickel oxide as a cocatalyst and an amorphous powder of lanthanum oxide- and / or barium oxide-containing alumina as a carrier component, A preferable example is a method in which water is added to the mixture, the mixture is placed in a ball mill, stirred and mixed to prepare a uniform slurry, the honeycomb substrate is dip-coated, dried, and heat-treated at about 900 ° C.

The first catalyst body is capable of burning and developing natural gas from about 400 ° C. under the rated combustion conditions of the gas turbine.

However, the palladium-based catalyst body as the first catalyst body cannot obtain long-term activity stability under the condition that the gas phase temperature at the catalyst layer outlet is 800 ° C. or higher. This is for the following reason. That is,
Palladium promotes an oxidation reaction by a mechanism mediated by oxygen adsorbed on the surface at a temperature lower than 800 ° C and has high reaction activity, but at a temperature higher than 800 ° C,
It has the property that oxygen adsorbed on the surface is completely desorbed and the oxidation activity is significantly reduced. NiO, MgO, Ce ₂
Cocatalysts such as 0 ₃ and ZrO ₂ exert an effect of suppressing the tendency to some extent, but the suppressing effect is not sufficient. Therefore,
When an excessive reaction such that the gas phase temperature at the catalyst outlet becomes 800 ° C. or higher is carried out in the palladium catalyst layer, the palladium shifts from the oxidized state to the reduced state in the intermediate portion of the catalyst, and the activity becomes Since the transition region including abrupt changes is included, a combustion oscillation phenomenon occurs in which the catalyst wall temperature and the combustion activity periodically change with a considerably large amplitude. Such combustion vibration promotes the growth of palladium particles, which causes the catalytic activity to significantly deteriorate.

Therefore, in the composite catalyst body according to the present invention, the palladium-based catalyst, which is the first catalyst body, has a temperature not higher than the catalyst outlet temperature, that is, not higher than about 750 ° C., which enables stable operation without the transition region of the reaction mechanism. Operate with. In the first catalyst body, a certain amount of reaction contact time is required to start combustion from about 400 ° C. and to perform combustion up to about 750 ° C. Therefore, the layer height is at least 20 mm and less than 60 mm. And Although it is possible to form the first catalyst body in one layer, it is preferable to divide the first catalyst body into two or more layers to reduce the layer height per layer. That is, since the catalyst for practical use has a large diameter, it is unavoidable that a certain temperature and combustion concentration distribution occur in the radial direction of the catalyst inlet due to the structural design limit of the combustor. Such a distribution induces a combustion distribution in the surface of the catalyst, especially at the beginning of combustion. Since this combustion distribution secondarily induces the inflow velocity distribution of the air-fuel mixture into the catalyst layer, the combustion distribution tends to be further promoted. If, for example, a combustion distribution of 200 ° C. or higher occurs in the plane of the catalyst layer, the manganese-substituted hexaaluminate catalyst in the wake may be broken due to thermal stress. The inconvenience that stability is also impaired occurs. On the other hand, when the catalyst layer is divided into two or more layers and combustion is performed in a state where an empty cylinder is formed in the middle, the temperature of the air-fuel mixture in the intermediate empty cylinder is
Since the effect of equalizing the concentration, the flow velocity, etc. is produced, the occurrence of combustion distribution can be reduced. Further, when the catalyst body is divided into two layers, in the catalyst of the first layer, the particle size of palladium is reduced or the amount of palladium supported is increased in order to express the activity as high as possible. It is advantageous that the catalyst can be configured in reverse to the catalyst of the first layer in order to improve durability.

In the first catalyst body, as described above, a catalyst containing palladium as a main component is used to exhibit low-temperature activity and the catalyst outlet temperature is a temperature at which the palladium catalyst can operate stably, that is, about 750 ° C. or less. And

Second catalyst body On the other hand, the temperature at which combustion can proceed with the highly heat-resistant manganese-substituted hexaaluminate catalyst (third catalyst body described later) used in the downstream, particularly under high pressure and high-speed conditions of the gas turbine. 800 ° C or higher is required.

Therefore, in the present invention, the first catalytic body and the third catalytic body are used.
In the middle of the catalyst body of No. 2, a second catalyst body is provided which is capable of combustion progress at about 650 ° C. and gives a catalyst outlet temperature of 800 ° C. or higher.

In the second catalyst body, a honeycomb substrate made of a heat-resistant material carries platinum as a catalytically active component and nickel oxide as a co-catalyst if necessary, and lanthanum oxide and a lanthanum oxide as a carrier component. It supports alumina containing barium oxide and / or silicon oxide.

As the honeycomb substrate, the same material and structure as those of the first catalyst body can be used.

The second catalyst body carries about 10 to 40 g / l of platinum as a catalytically active component, based on the honeycomb volume, and, if necessary, about 10 to 40 nickel oxide.
It carries g / l. Nickel oxide improves the thermal stability of the second catalyst body and exerts the effect of improving the durability. Similar effects are achieved when oxides of copper, chromium, cobalt, manganese, etc. are used instead of or together with nickel oxide.

Similarly to the first catalyst body, the second catalyst body further carries 50 to 200 g / l of alumina containing lanthanum oxide as a carrier component of the catalytically active component. It is similar to the case of the first catalyst body that alumina containing barium oxide and / or silicon oxide may be used instead of or together with alumina containing lanthanum oxide.

Platinum, which is the main catalytically active component of the second catalyst, has different characteristics from palladium and has a high combustion starting temperature of about 600 ° C, but there is no change in the reaction mechanism even at 800 ° C or higher. , Maintain high catalytic activity. Therefore, once the reaction is started, the reaction proceeds rapidly,
On the surface of the catalyst, the temperature rises to near the adiabatic theoretical combustion temperature of the air-fuel mixture, platinum particles evaporate or volatilize, or the activity deteriorates due to sintering or the like, and there is a tendency that the practicality is lost. Therefore, in the present invention, by coating the surface of the platinum catalyst layer coated on the honeycomb substrate with a porous inert carrier component, and controlling the reaction rate on the catalyst surface by the diffusion rate of the reactant, the platinum particle surface Inhibits rapidly progressing reactions.

In preparing the second catalyst body, first,
In the same manner as in the preparation of the first catalyst body, relatively large platinum particles of about 0.05 to 1 μm (and, if necessary, a catalytically active component consisting of a cocatalyst such as nickel oxide) and a carrier component are provided on the honeycomb substrate. A catalyst containing a catalytically active component and a carrier component is prepared using a slurry containing Then, the catalyst layer is coated with a slurry containing only the carrier component in the same manner to form a carrier layer. It is desirable to use the same carrier component as that used for forming the catalyst layer in the carrier layer that serves as the diffusion barrier layer for the reactants, in order to make the coefficient of thermal expansion uniform and prevent peeling. The carrier layer is similar to the case of the first catalyst body described above,
Even after heat treatment at 1100 ° C. for 5 hours, the specific surface area is 50 m ² /
It is preferably g or more. The carrying amount is 10 to 1
A range of 00 g / l is suitable. If the supported amount is too small, the effect of controlling the diffusion of the reactant becomes poor and the catalyst activity is likely to deteriorate.

As the method for preparing the second catalyst body, a method is used in which platinum particles are coated in advance with a porous carrier component, which is mixed with the carrier component and coated in the same manner as above. May be.

At a high temperature of over 1000 ° C., the second catalyst body has problems such as evaporation of platinum, volatilization and volatilization of the carrier, sintering of the carrier, reaction of the catalyst component with the carrier, peeling of the coating component, and the like, and durability. . Therefore, in the present invention, the bed height of the second catalyst is 4
The catalyst outlet temperature is set to about 0 mm or less (more preferably about 15 to 30 mm), the catalyst outlet temperature is set to about 850 ° C. or less, and the following third catalyst body is provided in the subsequent flow.

Third Catalyst Body The third catalyst body provided downstream of the second catalyst body has a layered crystal structure composed of a total of 1 mol of an alkaline earth metal oxide and a rare earth metal oxide and 6 mol of alumina. Is based on a complex oxide having the formula (this is called hexaaluminate), the aluminum atom of which is replaced by manganese having a catalytic action while maintaining its crystal structure. It is a catalyst body having the above composition.

[0037] _{A 1 -x Z x Mn y Al} 12-y O 19-α (1) ( where, A is Sr, represents at least one Ba and Ca; Z represents La and / or Pr; x = 0.1
˜0.4, preferably 0.2; y = 0.5 to 2.0, preferably 1.0; −1 ≦ α ≦ 1) The third catalyst body is represented by the above formula (1). A plurality of manganese-substituted hexaaluminates formed into honeycomb shapes having different sintering temperatures and specific surface areas are used.

Of these plural third catalyst bodies, the catalyst body close to the second catalyst body has a specific surface area of 8 to 20 m.
Increase to about ² / g. As a result, even under high pressure and high linear velocity combustion conditions such as in a gas turbine,
It is possible to progress combustion at a temperature of 00 ° C. or higher (this third catalyst body having a high specific surface area is hereinafter referred to as “third catalyst body A”). The third catalyst body A is prepared, for example, as follows.
First, a manganese-substituted hexaaluminate raw material powder having a composition corresponding to the above formula (1) is prepared by adding an aqueous solution containing a manganese salt to an alkoxide solution of a rare earth metal such as aluminum, lanthanum, and strontium, or an alkaline earth metal. After disintegrating, gelling and drying, 1000 ~
It can be prepared by sintering at about 1100 ° C., crushing and classifying to an appropriate size. At this time, the rare earth metal may be added to the manganese salt solution as a water-soluble salt. Then, according to a conventional method, water and, if necessary, an organic molding aid are added to the obtained raw material powder, and the mixture is kneaded, extruded into a honeycomb shape, dried, and then about 115
Sinter at 0 to 1250 ° C. The specific surface area and strength of the third catalyst body A can be appropriately adjusted by selecting the composition and particle size of the raw material powder, the kneading strength, the molding pressure, the sintering temperature, the sintering time and the like. As a honeycomb formed body, an opening ratio of 60 to 70% and a cell number of about 200 to 300 per square inch satisfy both strength and activity, which is preferable. The material constituting the third catalyst body A is an alumina-based material, which is more preferable than the cordierite honeycomb used as a preferable material for the first and second catalyst bodies.
It has the drawbacks of high thermal expansion coefficient and low thermal shock resistance.
To compensate for this drawback, the height of one catalyst layer of the third catalyst body A is within 30 mm (more preferably about 15 to 25 mm).
The stress generated by thermal expansion is reduced as much as possible by using at least one of them, and the destruction of the catalyst body itself is prevented.

The third catalyst body A is prepared by sintering at a relatively low temperature of about 1150 to 1250 ° C. in order to improve low temperature activity. Therefore, the catalyst temperature of the third catalytic body A is 1
Under conditions exceeding 100 ° C, sintering proceeds for a long time,
It cannot be used because it contracts. Under such conditions, the gas phase temperature at the catalyst outlet must be set to less than 1100 ° C. Therefore, if the third catalyst body A is arranged after the second catalyst body, a gas turbine combustor can be obtained. The target catalyst outlet temperature of 1100 ° C is not reached.

To this end, the third catalytic body A is subsequently sintered at about 1250 to 1350 ° C. and has a specific surface area of about 3 to
8 m ² / g of the third catalyst body (hereinafter referred to as the third
Of the catalyst body B). The third catalyst body B is obtained by subjecting the manganese-substituted hexaaluminate powder material represented by the above formula (1) to honeycomb extrusion molding by the same method as that of the third catalyst body A, and drying the material. 1250
It is prepared by sintering at ˜1350 ° C. This third catalyst body B
Has a layer height of 30 mm or less (more preferably 15 to
25 mm) and at least one is used. As a result,
Catalyst temperature 1200 ° C or lower, catalyst outlet temperature 1100-12
Natural gas can be completely burned under the condition of 00 ° C. When the specific surface area of the third catalyst body B is less than 3 m ² / g, the catalytic activity becomes too low. Therefore, under the condition that the pressure loss rate of the catalyst layer is 3% or less, which is the target of natural gas, Complete combustion cannot be achieved.

The composite catalyst body according to the present invention comprises a plurality of catalyst bodies each including at least one first catalyst body, second catalyst body, third catalyst body A and third catalyst body B. The installation interval is 5 to 10 mm.
In addition, the specific surface area of the third catalyst body A is larger than the specific surface area of the third catalyst body B.

Hereinafter, the present invention will be described in more detail with reference to the embodiments of the composite catalyst body of the present invention.

FIG. 2 schematically shows an embodiment of the composite catalyst body for high temperature combustion according to the present invention, which is applicable to combustion under high pressure and high linear velocity, particularly in a gas turbine combustor. In this composite catalyst body, in the foremost part where the fuel gas (natural gas) -air mixture 11 flows, a heat-resistant honeycomb substrate such as cordierite is made to support a catalytically active component mainly composed of palladium. A and B corresponding to the above catalyst body, and then a heat resistant honeycomb substrate such as cordierite having a catalytically active component mainly composed of platinum supported thereon, the catalytic activity of which is controlled for the purpose of controlling the surface reaction. C corresponding to the second catalyst body coated with an inert diffusion barrier layer on the layer, and D, E corresponding to the third catalyst body in which the manganese-substituted hexaaluminate is directly honeycomb-molded.
F and G are sequentially arranged. In the third catalyst body, D and E on the front side were sintered at about 1200 ° C., their specific surface area was about 13 m ² / g, and F and G on the back side were baked at about 1300 ° C. And the specific surface area is about 7 m ² / g.

The height of each catalyst layer is 20 mm, and the distance between each catalyst layer is about 10 mm. The catalyst layer space is held by a metal or ceramic material (not shown) having a shape that suppresses the flow resistance as much as possible. The outside of each catalyst body is
It is covered with a heat insulating material 13 and fixed with a metal frame 15. The composite catalyst body according to the present invention is of course not limited to the one shown in the figure, and in particular, in the third catalyst body, the distribution of high surface area by low temperature sintering and low surface area by high temperature sintering is determined according to combustion conditions. It goes without saying that it can be appropriately changed according to Also, for the first catalyst body, for example, when it is applied to low pressure combustion, the apparent reactivity is higher than that under high pressure conditions due to the characteristics of the reaction mainly containing palladium. The layer height of the medium may be lowered.

When the above-mentioned high-temperature combustion composite catalyst body is burned under the combustion conditions applied to the gas turbine as described above, in the first catalyst layer, the combustion is started from the inlet temperature of about 400 ° C. Combustion is performed up to a phase temperature of 750 ° C or lower. The air-fuel mixture containing unburned fuel enters the second catalyst body and is burned until the outlet gas phase temperature of 800 to 850 ° C is reached. Finally, the air-fuel mixture containing unburned fuel enters the third catalyst body and is completely combusted, and combustion exhaust gas 17 having a gas phase temperature of 1100 to 1200 ° C. at the catalyst outlet is obtained.

[0046]

According to the present invention, the following remarkable effects are achieved.

1) In the composite catalyst body of the present invention,
(A) Arranging the first catalyst body mainly composed of palladium, which is the most active against methane, which is the main component of natural gas, in the forefront part, and (b) installing the diffusion barrier layer on the surface in the middle part. By arranging the second catalyst body mainly composed of platinum, which suppresses excessive reaction progress, (c) a third catalyst body in which a manganese-substituted layered aluminate having high-temperature heat resistance is directly formed into a honeycomb at the final stage. Are arranged. Among these catalyst bodies, the second catalyst body exerts sufficient combustion activity from the temperature of 650 to 700 ° C., which can prevent the activity reduction of the palladium catalyst and the combustion oscillation accompanying it, and the catalyst activity is exhibited. Also, without causing an excessive reaction, it is possible to contribute to the temperature rise up to a temperature of 800 to 850 ° C. at which the activity of the manganese-substitution type layered hexaaluminate catalyst which is the third catalyst body is sufficiently exhibited. Therefore, by the above combination, the highest catalyst activity can be exhibited while maintaining the long-term activity of each catalyst in each temperature range from low temperature to high temperature.
Therefore, in a large-diameter catalyst, there is some degree of catalyst inlet temperature, air-fuel mixture concentration, flow velocity fluctuation, etc., and even under severe combustion conditions such as in a gas turbine combustor operated under high pressure and high linear velocity, natural gas Combustion starts from below 450 ° C, and almost no NOx is generated.
Complete combustion is possible at 200 ° C or lower, and its combustion performance can be maintained for a long time.

2) When the composite catalyst body according to the present invention having the above structure is incorporated in the catalytic combustor shown in FIG.
The amount of flame combustion in the part where NO _x is generated is 1/7 of the main fuel
The amount of NO _x generated is 40 ppm (0 ₂
Ultra low NO _x of 0% or less) can be easily achieved. Therefore, a flue gas denitration device is not required, and a compact and low-cost NO _x reduction means can be obtained.

3) The composite catalyst body according to the present invention can be applied not only to natural gas but also to combustion of LPG fuel and kerosene fuel.

4) When the temperature of the gas turbine rises, it is of course possible to add secondary fuel to the wake of the composite catalyst body according to the present invention and to perform gas phase combustion. When the composite catalyst body according to the present invention is used, the catalyst outlet temperature can be set to a high temperature, which facilitates the progress of gas phase combustion in the wake and realizes a compact hybrid combustion system that combines catalyst combustion and gas phase combustion. it can.

[0051]

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Experimental Apparatus FIG. 3 is a sectional view showing the outline of an experimental apparatus for combustion measurement under atmospheric pressure. The entire catalyst portion including the catalyst bodies 21a to 21g has a heat insulating material 23 to prevent heat loss.
Is kept warm by and is held by the metal frame 24. The periphery of the metal frame 24 is also kept warm (not shown).
The catalyst portion is divided into 7 layers and installed at intervals of about 10 mm.

The combustion measurement is mainly carried out by thermocouples T-0 to T-7 having a diameter of 1 mm installed between the catalyst bodies and a thermocouple installed in the catalyst honeycomb passages (details are shown in FIG. 4).
And the exhaust gas sampling pipe 25 and the gas analyzer 27 installed at a distance of 30 mm from the outlet of the catalyst layer. The front and rear of the honeycomb passage having the thermocouple inserted therein are filled with a ceramic coating material to block the gas flow (not shown). Temperature measurements are taken at 15 second intervals. The unburned hydrocarbons in the exhaust gas are measured by the FID type hydrocarbon meter 27a, and CO and CO ₂ are non-dispersion type infrared absorption type measuring instruments 2
By 7b, oxygen by magnetic oxygen analyzer 27c, NO _x
Are analyzed by the chemiluminescence measuring device 27d. The fuel-air mixture consisting of the air from the line 31 and the natural gas from the line 33 preheated by the preheater 29 is left in the leftward direction in FIG. 3 in a uniformly mixed state and adjusted to a predetermined inlet temperature. And is used for catalytic reaction. All combustion measurement experiments were carried out using natural gas (containing approximately 88% of methane) supplied in the city.

FIG. 5 shows a catalytic combustor 41 whose outline is shown in FIG.
It is a side view which shows the outline of the test apparatus which mounted | worn with the gas turbine 43. The operating conditions of the turbine engine are a turbine inlet temperature of 910 ° C., a rated output of 150 KW, and a pressure ratio of 8.
5. Compressor outlet air temperature is 350 ° C. Load adjustment
An eddy current type electric dynamometer 45 is used. Exhaust gas analysis is performed by sampling at the outlet of the gas turbine 43 on the exhaust duct 47 side, using the same instrument as shown in FIGS. 3 and 4 above. The catalyst layer temperature is measured in the same manner as in FIG. 4 by setting 28 thermocouples having a diameter of 1 mm in the catalyst layer (not shown).

Preparation of each catalyst body 1) First catalyst body A cordierite honeycomb substrate having 200 cells per 1 square inch, an opening ratio of 69%, and a layer height of 20 mm was placed on a palladium powder having an average diameter of 1 μm and nickel oxide. After coating the catalytic material with a mixed sol of powder and alumina powder containing 8.3 wt% of lanthanum oxide powder, 90
It heat-processed at 0 degreeC for 3 hours, and prepared two cordierite carrying | support palladium catalyst bodies.

Table 1 shows the amounts of Pd, NiO and Al ₂ O ₃ -La ₂ O ₃ supported in the two types of catalyst bodies obtained.

[0057]

[Table 1]

2) Second catalyst body A cordierite honeycomb substrate having 200 cells per 1 square inch, an opening ratio of 69%, and a layer height of 20 mm was used, and platinum powder having an average diameter of 0.2 μm, nickel oxide powder, and After coating a mixed sol of alumina powder containing 8.3% by weight of lanthanum oxide, heat treatment was carried out at 900 ° C. for 3 hours to prepare a cordierite-supported platinum catalyst. Further, an alumina powder sol containing 8.3 wt% of lanthanum oxide was applied to the supported platinum catalyst and heat-treated at 900 ° C. for 3 hours to prepare four types of catalyst bodies having an inert diffusion barrier layer.

[0059] Pd of the four catalyst in the obtained, NiO and Al ₂ O ₃ -La ₂ Al of O loading of ₃ and an inert diffusion barrier layer ₂ O ₃ -La ₂ O ₃ weight Table 2 Shown in. The catalyst body 2D is a comparative catalyst body having no inert diffusion barrier layer.

[0060]

[Table 2]

3) Third Catalyst Body Under a nitrogen atmosphere, aluminum isopropoxide and strontium metal were dissolved in isopropyl alcohol at 80 ° C. for 5 hours. Then, a mixed aqueous solution containing lanthanum acetate and manganese acetate was added dropwise to the obtained solution to carry out hydrolysis. After aging the reaction solution for 12 hours, the obtained suspension was dried under reduced pressure at 80 ° C., calcined at 500 ° C., and then calcined at 1100 ° C. for 5 hours.
A manganese-substituted hexaaluminate crystal powder represented by the composition formula Sr _0.8 La _0.2 MnAl ₁₁ O _19-α was obtained.
Add water and a small amount of an organic molding aid to this crystal powder,
After sufficiently kneading, it was extruded into a honeycomb shape. The molded body was sintered at 1200 ° C. for 5 hours or 1300 ° C. for 5 hours to obtain third catalyst bodies A and B, respectively. Each of these catalyst bodies was a honeycomb structure having 300 cells per square inch, an opening ratio of 65%, and a layer height of 20 mm.
Table 3 shows the sintering temperature and the BET specific surface area of the third catalyst bodies A and B.

[0062]

[Table 3]

4) Composite Catalyst Body The first to third catalyst bodies obtained as described above were combined as shown in Table 4 to form a composite catalyst body.
In Table 4, for example, "1A" means the first catalyst body 1A shown in Table 1, and the same applies to the other.

[0064]

[Table 4]

Experiments and Results 1) Atmospheric Pressure Experiment <Experimental Method> The composite catalyst bodies having a diameter of 50 mm shown in Example 1, Comparative Examples 2 and 3 and Comparative Examples 1 and 2 were attached to the experimental apparatus shown in FIG. A combustion experiment was conducted as follows at atmospheric pressure.

City-supplied natural gas (sulfur content 7 mg / N
m ³ and total calorific value 11,000 Kcal / Nm ³ ) as fuel, and air with 21% oxygen as an oxygen source, catalyst inlet temperature 4
Combustion was carried out under the conditions of 00 ° C., adiabatic theoretical combustion temperature of 1200 ° C. (fuel gas concentration of 3.0%), and linear velocity of 3.5 Nm / sec in terms of catalyst inlet empty cylinder.

<Results> FIG. 6 is a graph showing the measurement results of the catalyst layer wall temperature of the first-stage and second-stage catalyst bodies.

The temperature of the palladium catalyst body in the first stage was 800 ° C. or lower for all the tested catalyst bodies, and an excessive reaction did not occur on the palladium catalyst, and stable combustion was performed. Is shown. In addition, there was almost no difference between the catalyst bodies. On the other hand, the temperatures of the second-stage catalyst bodies showed remarkable differences as follows.

In Example 1, Example 2 and Example 3 in which an inert diffusion barrier layer was provided in the second stage and a second catalyst body containing platinum whose surface reaction was controlled was placed, manganese substitution was carried out. Although the temperature of the second catalyst body is higher than that of Comparative Example 2 in which the type layered hexaaluminate catalyst body is in the second stage, the maximum temperature is controlled to 950 ° C or lower. On the other hand, in Comparative Example 1 in which the diffusion barrier layer is not provided in the second stage, the catalyst temperature reaches 1100 ° C.

From the above results, when the inert diffusion barrier layer is provided on the surface of the platinum catalyst as the second catalyst,
It is clear that the high speed surface reaction rate of the platinum catalyst can be controlled and the surface temperature can be lowered to the temperature level where the durability of the catalyst can be secured. Therefore, since the activity is improved as compared with the high temperature heat resistant manganese-substituted hexaaluminate catalyst installed in the latter stage, it is clear that the combustion performance of the composite catalyst body can be significantly improved.

Actually, under each condition, 1
The combustion was continued for 000 hours, and during that period, the temperatures measured at three points in the catalyst layer and one point at the outlet did not change at all from the initial stage and no catalyst deterioration was observed.

FIG. 7 is a graph showing the results of comparison of the combustion performance of the composite catalyst bodies in Example 1, Example 2 and Comparative Example 2. In Examples 1 and 2, since the activity was satisfactorily developed in the second-stage catalyst, the combustion was completed on the upstream side of the catalyst layer, and the combustion performance was significantly improved. it is obvious.

2) Turbine installation test results <Test method> Using a catalyst having a diameter of 220 mm, a prototype catalytic combustor whose basic structure is shown in FIG. 1 was prepared, and the rated output was 150 KW, the pressure ratio was 8.5, and the combustor inlet. Air temperature 3
A turbine mounting test was conducted using a 50 ° C. turbine. When preparing the catalyst, an integrally molded product having a particle diameter of 220 mm was used as a cordierite honeycomb. The manganese-substituted hexaaluminate catalyst was molded into a four-divided circle, and the manganese-substituted hexaaluminate was adhered to form a disc. The combinations of the catalyst bodies were Example 4, Example 5, Comparative Example 2 and Comparative Example 3 (see Table 4).

<Results> Examples 4 and 5 In the manganese-substituted hexaaluminate catalyst layer surface during the transition operation from the turbine start by the precombustor 1 to the catalytic combustion mode in which the precombustion amount is reduced and the load input operation. A stable turbine operation was achieved without a temperature difference of 200 ° C. or higher.

Further, the combustion performance at the rated load of 150 KW is as follows, and a good result exceeding the target value was obtained.

That is, in Example 4, the catalyst inlet temperature = 41
Under the conditions of 0 ° C., adiabatic theoretical combustion temperature = 1150 ° C., catalyst inlet hollow linear velocity = 3.5 m / s (0 ° C., 8.5 atm conversion), a combustion efficiency of 99% or more is obtained, and NO _x is It became 15 ppm (oxygen 0% conversion). 20 in this state
After 0 hours of continuous combustion, no tendency of decreasing the catalytic activity was observed.

Furthermore, in Example 5, the catalyst inlet temperature = 4
Under the conditions of 25 ° C., adiabatic theoretical combustion temperature = 1150 ° C., catalyst inlet empty linear velocity = 3.5 m / s (0 ° C., 8.5 atm conversion), a combustion efficiency of 99% or more was obtained, and NO _x
Was 25 ppm (oxygen 0% conversion). 2 in this state
After continuous combustion for 00 hours, the tendency of activity decrease is
After all it was not recognized.

Comparative Example 2 In the transition operation from the start of the turbine by the precombustor 1 to the catalytic combustion mode in which the precombustion amount is reduced and the load application operation, a temperature of 200 ° C. or higher in the plane of the manganese-substituted hexaaluminate catalyst layer. A difference occurs, combustion performance fluctuates,
Reproducibility was not obtained in turbine operation.

Comparative Example 3 In the transition operation from the start of the turbine by the pre-combustor 1 to the catalytic combustion mode with a reduced pre-combustion amount and the load input operation, the manganese-substituted hexaaluminate catalyst layer has a temperature of 200 ° C. or higher. There was no temperature difference and stable durbin operation was possible. However, the catalyst inlet temperature could not be lowered to 500 ° C. or lower, and NO _x could not be reduced to 75 ppm (oxygen 0% conversion) or lower.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a gas turbine combustor applied to a catalytic combustion method.

FIG. 2 is a sectional view showing an example of a high temperature combustion composite catalyst body according to the present invention.

FIG. 3 is a cross-sectional view showing an outline of an experimental apparatus for combustion measurement under atmospheric pressure used in Examples.

FIG. 4 is a cross-sectional view showing a temperature measurement system in FIG.

FIG. 5 is a side view showing an outline of a test apparatus in which the catalytic fuel device whose outline is shown in FIG. 1 is attached to a gas turbine.

FIG. 6 is a graph showing the measurement results of the catalyst layer wall temperature of the used first-stage and second-stage catalyst bodies in Examples and Comparative Examples.

FIG. 7 is a graph showing the results of comparing the combustion performance of composite catalyst bodies in Examples 1 and 2 and Comparative Example 2. 1 ... Precombustor 3 ... Premixer 5 ... Catalyst cassette 7 ... Bypass air valve 11 ... Fuel-air mixture 13 ... Insulation material 15 ... Metal frame 17 ... Combustion exhaust 21a to 21g ... Catalyst body 23 ... Insulation material 24 ... Metal frame 25 ... Exhaust gas sampling pipe 27 ... Gas analyzer 29 ... Preheater 31 ... Air supply line 33 ... Natural gas supply line 41 ... Catalytic combustor 43 ... Gas turbine 45 ... Eddy current electric dynamometer 47 ... Exhaust duct

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location F01N 3/28 301 J F23D 14/16 B (72) Inventor Shinichi Adachi Hirano, Chuo-ku, Osaka-shi, Osaka 4-1-2 Machi Osaka Gas Co., Ltd. (72) Inventor Takayuki Inoue 4-1-2 Hiranocho Chuo-ku, Osaka City, Osaka Prefecture Osaka Gas Co., Ltd. (72) Inventor Nakahira Takashi Osaka, Osaka Prefecture 4-1-2 Hirano-cho, Chuo-ku, Osaka, Japan (72) Inventor Toshio Matsuhisa 7-2-10 Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture (72) Takashi Tanioka Takatsukadai, Nishi-ku, Kobe-shi, Hyogo 1-5-5 Kobe Steel Ltd. Kobe Research Institute

Claims (6)

[Claims] 1. A composite catalyst for high temperature combustion used in a device for catalytically burning a fuel gas-air mixture, comprising:
(1) a first catalyst body which is located on the inlet side where the air-fuel mixture flows and which carries a catalytically active component mainly composed of palladium on a heat-resistant honeycomb substrate; and (2) a heat-resistant honeycomb body which is located on the subsequent flow side. A second catalyst body carrying a catalytically active component mainly composed of platinum on the substrate; and (3) a plurality of third catalysts formed on the downstream side and formed with manganese-substituted hexaaluminate in a honeycomb shape. A composite catalyst for high temperature combustion characterized by comprising a medium. 2. The first catalytic body as a catalytically active component,
50 g / l to 150 g / palladium per honeycomb volume
1 and, if necessary, nickel oxide of 20 to 70 g / l, and 50 to 200 g / l of lanthanum-containing alumina as a carrier component. Combustion composite catalyst body. 3. The high temperature combustion composite catalyst body according to claim 1, wherein the first catalyst body is composed of two layers and the height of each layer is 10 to 30 mm. 4. The second catalytic body as a catalytically active component,
It carries 10 to 40 g / l of platinum per honeycomb volume and 10 to 40 g / l of nickel oxide if necessary,
Alumina 50-2 containing lanthanum as a carrier component
The composite for high temperature combustion according to any one of claims 1 to 3, wherein the catalyst coating layer carrying 00g / l and comprising a catalytically active component and a carrier component is coated with a combustion-inert porous layer. Catalyst body. 5. The third catalyst is a manganese substituted hexa-aluminate powder prepared by an alkoxide method has been directly honeycomb molded as a starting material, the composition _{A 1-x Z x Mn y} Al _{12- y} O _{19- α} (However, A is S
at least one of r, Ba and Ca; Z is at least one of La and Pr; x = 0 to 0.3; y = 0.5
˜2.0; −1 ≦ α ≦ 1), and the height of one of them is 10 to 25 mm, wherein the composite catalyst body for high temperature combustion according to any one of claims 1 to 4. 6. A third catalyst body composed of a plurality of:
Sintered at 1150 to 1250 ° C in the previous stage and had a specific surface area of 8 to 2
Those having a specific surface area of 3 to 8 m ² / g were obtained by arranging those having a specific surface area of 0 m ² / g so as to have a total layer height of at least 20 mm or more and sintering at a temperature of 1250 to 1350 ° C. Claim 1 arrange | positioned so that it may become 20 mm or more.
A composite catalyst body for high temperature combustion according to claim 5.