JPS6241511A - Combustion catalyst system and its process for combustion - Google Patents

Abstract

PURPOSE:To provide a catalyst system in which a combustion gas temperature is increased, a loss of pressure is low and a durability is attained by a method wherein a catalyst layer having as major active constituent a palladium, platinum and nickel oxide is arranged at a front-stage and another catalyst layer having as an active constituent a platinum is arranged at a rear-stage. CONSTITUTION:Fire-retardant fuel mainly of methane is processed such that an ignition characteristic of methane caused by palladium oxide is prevented from being decreased in the presence of small amount of platinum at the front- stage catalyst near an inlet port of the catalyst system, low temperature ignition characteristic can be maintained over a long period of time. Presence of the nickel as its oxide ensures a stable supplying of oxygen to palladium, so that it is possible to increase a combustion gas temperature to about 600-900 deg.C at a high speed and a high pressure. the combustion is continued and promoted farther in the presence of platinum at the rear-stage catalyst near an outlet port of the catalyst layer, and thus the combustion gas temperature can reach 750-1,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a catalyst system for catalytically combusting fuel and a combustion method using the same.

Specifically, the present invention catalytically burns flame-retardant methane or a natural gas fuel mainly composed of methane together with molecular oxygen on a catalyst to produce nitrogen oxides (hereinafter referred to as NOx) and -carbon oxides (hereinafter referred to as CO). ), unburned hydrocarbons (
The present invention provides a catalyst system and a combustion method using the same for obtaining a combustion gas substantially free of harmful components such as tJHc) and using the calorific value thereof as various energy sources.

More specifically, the present invention involves the use of methane, which is said to be relatively flame-retardant among hydrocarbons, or a natural gas fuel containing methane as a main component, at a low temperature using a catalyst together with molecular oxygen at normal to high pressures and high linear velocities. ignite the fuel, raise the temperature to a temperature sufficient to induce secondary combustion, and then introduce secondary fuel as necessary to combust the remaining unburned fuel and secondary fuel to achieve the desired purpose. The present invention provides a catalyst system suitable for use in a combustion system that raises the temperature of the present invention or higher temperatures, and a combustion method using the same.

<Technical Background of the Invention and Problems Therein> A diluted a-mixture gas in which fuel is mixed with air at a low concentration that does not fall within the combustible range is introduced into a catalyst layer and catalytically combusted on the catalyst to obtain high-temperature combustion gas. Catalytic combustion systems are known.

Furthermore, using such a catalytic combustion system, e.g.
When obtaining combustion gas from 00°C to 1500°C, even if air is used as the oxygen source, N.

× rarely or never occurs, and c
It is also well known that it can be obtained substantially free of o and uHc.

Various systems have been proposed that utilize this clean, high-temperature combustion gas to generate heat or power, and general industrial exhaust gas treatment and thermal power recovery systems have already been put into practical use.

In addition, in recent years, in response to increasing NOx regulations, research has been conducted to utilize this high-temperature combustion gas as a primary power source such as a gas turbine for power generation.

When used for these purposes, the combustion gas is normally brought to a high temperature of 1000 to 1300°C under 6 to 15 atmospheres, and there is a tendency for the combustion gas to reach even higher temperatures and pressures to improve the efficiency of gas turbines. It is in.

Under such conditions, when a normal catalyst is used, it deteriorates rapidly due to the high temperature, and in the worst case, the catalyst carrier becomes null 1.
- There is a possibility that it will come down, fly off, and damage turbine blades.

As a combustion method that achieves the same purpose while avoiding deterioration and damage to the catalyst as described above, a part of the fuel is combusted in the catalyst layer, the gas temperature is raised to a temperature that induces secondary combustion, and then The remaining unburned fuel is secondaryly combusted behind the catalyst layer, or if necessary, secondary fuel is introduced and the remaining unburned fuel and newly added secondary fuel are combusted secondarily. A combustion method has been discovered that produces clean combustion gas at or above the desired temperature.

Here, the temperature required to induce secondary combustion is determined by the type of fuel, residual fuel concentration (theoretical adiabatic combustion gas temperature), linear velocity, etc., and varies widely depending on the type of fuel.

In other words, in the case of easily flammable fuels such as propane and light oil, a temperature of about 700°C is sufficient under normal usage conditions;
If flame-retardant methane or natural gas whose main component is methane is used as fuel, 75
A high temperature of 0 to 1000°C is required.

<Object of the Invention> The object of the present invention is to ignite flame-retardant fuel, mainly methane, at high linear velocity and under high pressure with as low humidity as possible, and to raise the combustion gas temperature to a temperature of 750 to 1000 ° C. It is also an object of the present invention to provide a catalyst system having low pressure loss and durability, and to provide a method for effectively utilizing the catalyst system.

<Summary of the Invention> The present inventors have focused on the excellent characteristics of noble metal catalysts, and have completed the present invention as a result of intensive research to overcome the drawbacks seen in conventional catalysts.

That is, the catalyst system according to the present invention has two catalyst layers: a catalyst that can be ignited at a relatively low temperature used in the first layer, and a high-temperature combustible catalyst that can tear the combustion gas temperature up to 750 to 1000 degrees Celsius used in the second layer. The catalyst used in the first layer consists of palladium, platinum, and nickel as active components, and the catalyst used in the second layer consists of platinum as an active component, and , so that the temperature does not exceed 1000°C.

According to the present invention, the presence of a small matrix of platinum in the front stage catalyst near the entrance of the catalyst system prevents the deterioration of methane ignition performance due to palladium oxidation, making it possible to maintain low-temperature ignition performance for a long period of time. At the same time, the presence of nickel as an oxide stably supplies oxygen to palladium, making it possible to raise the combustion gas temperature to 600 to 900°C at high linear velocity and high pressure. It has been found that the presence of platinum in the post-catalyst further promotes combustion, allowing the combustion gas to reach a temperature of 750 to iooo<0>C.

As a result, the catalyst layer as a whole is capable of igniting methane or a natural gas fuel containing methane as a main component at high linear velocity, high pressure, and low temperature, and raising the combustion gas to a temperature of 750 to 1000 degrees Celsius. Moreover, it has become possible to maintain this performance for a long time.

Furthermore, in the present invention, the catalyst system is a three-stage system, with a catalyst layer containing palladium and platinum as active components in the first stage, a catalyst layer containing palladium and nickel oxide as active components in the middle stage, and a catalyst layer containing platinum as active components in the second stage. It has been found that a system equipped with a catalyst layer that has a catalyst layer of

By further configuring the front stage catalyst into two stages, with the first half being a catalyst layer containing palladium and platinum as active components, and the second half (middle stage) being a catalyst layer containing palladium and nickel as active components, the combustion activity of the front stage catalyst is further increased. This means that it is possible to improve the

In this case, the temperature is raised to a temperature in the range of 500 to 800°C in the front catalyst layer, and 650°C in the middle catalyst layer.
temperature in the range of ~900°C, and in the downstream catalyst layer 8
Combustion activity is maintained at a high level by subjecting each MU to a temperature in the range of 00 to 1000°C.

<Function> In the present invention, the catalysts for the former layer and the latter layer are prepared separately, and both catalysts may be directly connected or a space may be provided between them, or they may be placed on an integrated carrier. A completed catalyst may be obtained by supporting a front layer catalyst at the inlet portion and a rear layer catalyst at the outlet portion.

The shape of the catalyst is preferably a monolith type for the purpose of reducing pressure loss. Any monolith support commonly used in the field can be used, in particular cordierite, mullite, alpha alumina, zirconia, titania, titanium phosphate, aluminum titanate, petalite, subodumene, aluminosilicate, silica. Magnesium acid, zirconia spinel, zircon
Heat-resistant ceramic materials such as mullite, silicon carbide, and silicon nitride, and metal materials such as Kanthal and Feclaroy are used.

The cell size of the monolithic carrier is preferably large as long as the combustion efficiency is not reduced, and each catalyst layer may have the same cell size or a combination of different cell sizes. ~400t? Those from 1999 are used.

The total amount of catalyst layer varies depending on the inlet linear velocity used, but
The length of 50 to 500 m is usually adopted due to the need to reduce pressure loss, and the quality of each of the front and rear layers is also optimally selected depending on the usage conditions such as inlet linear velocity and inlet temperature, but usually 25 to 250 m is used for each layer. Adopted.

The catalyst used in the first layer is usually a monolithic carrier coated with an active refractory metal oxide such as alumina, silica-alumina, magnesia, titania, zirconia, or silica-magnesia. Alumina or zirconia is particularly preferred, and when used after being stabilized by adding alkaline earth metal oxides such as magnesium, calcium, strontium, and barium, and rare earth metal oxides such as lanthanum, yttrium, cerium, samarium, neodymium, and praseodymium. More preferred.

Thereafter, the active principal components of palladium, platinum and nickel are impregnated and catalyzed in the form of water-soluble salts. Alternatively, it is possible to catalyze the active main component by supporting it on an active refractory metal oxide and then coating it on a monolithic carrier. It can also be catalyzed by mixing it with a reactive metal oxide and coating it on a monolithic support.

Palladium is 0.2-15.0% by weight per finished catalyst,
Preferably, platinum is supported at 0.5 to 12.0 ffl concentration, and platinum has a weight pressure of 0.002 to 1, relative to palladium.
It is preferably added in an amount of 0.05 to 0.3. In addition, the supported amount of nickel component is NiO2 per finished catalyst.
as 0.5 to 35.0% by weight, preferably 1.0 to 2
0.0% by weight is suitable.

In the same way, a case where a catalyst is used in the third stage is prepared, and in particular, the palladium/nickel ratio in the middle stage is Pd
/N i 0 weight ratio, O, OO are used in combination in a range of 1 to 20.

The catalyst used in the latter layer can also be converted into a catalyst by supporting platinum in the same way, but in this case, the catalyst is too active and the temperature in the catalyst layer rises to over 1000°C, making it an enemy of platinum. It may cause deactivation and dyeing due to flowers etc. In order to avoid this and keep the catalyst layer temperature below 1000°C, it is preferable to use coarse platinum particles such as platinum black, or to reduce the amount of platinum supported, or use a ready-made catalyst. Examples include a method of pre-calcining at a high temperature exceeding 1000℃, and a method of optimally selecting the cell size and layer length of the catalyst. It can be optimally selected depending on the temperature), linear speed, pressurizing conditions, etc.

The fuel used in the combustion system using the catalyst of the present invention is methane or a fuel containing methane as a main component. A typical example is natural gas. Natural gas contains more than 80% methane, although the composition ratio varies depending on the region of production. Zl: Fermented methane from activated sludge treatment and low-calorie methane gas from coal gasification are also fuels that can be used in the present invention. Naturally, more flammable propane, light oil, etc. can also be used.

The combustion catalyst system of the present invention can be optimally incorporated into a power generation gas turbine system as described above, but it can also be used in power generation boilers, heat recovery boilers, and after-treatment of gas from gas engines. It is used to efficiently recover heat and power such as heat recovery and city gas heating.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 25 mm diameter with 200 tons/in2 aperture.
A cordierite honeycomb carrier of 4 mm in length and 25 M in length was coated with an alumina slurry containing 7% lanthanum oxide (as La203 vs. alumina), dried, and then fired at 700° C. in air. After the Iζ coating treatment, 20,000% of lanthanum oxide-containing aluminum was supported on the carrier.

Next, this carrier is immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and then calcined in air at 900°C to obtain 2.7% palladium per finished catalyst.
A finished catalyst was obtained by supporting 0.5% by weight of platinum.

Example 2 As in Example 1, a diameter of 25.4 mtn and a length of 50 m with 200 cells/in2 apertures was prepared.
Alumina containing lanthanum oxide was coated on a cordierite honeycomb carrier of 20% by weight.

Next, this is immersed in an aqueous solution containing chloroplatinic acid,
After drying, the mixture was calcined in air at 900°C to obtain a finished catalyst in which 1.4% by weight of platinum was supported on the finished catalyst.

Example 3 A mullite honeycomb support having the same shape as the support used in Example 2 (a slurry of alumina powder containing 15% lanthanum oxide and 5% neodymium oxide on wood and having an average particle size of 5 microns) was used. By sufficiently mixing the platinum black powder containing the powder and coating it, drying it and then calcining it in the air at 900°C, the final catalyst contains 23% by weight of alumina powder containing lanthanum oxide and neodymium oxide and 2.3% by weight of platinum. A completed catalyst was obtained by supporting the .

Example 4 A cordierite honeycomb carrier having the same shape as the carrier used in Example 1 was coated with a mixed slurry of alumina powder and nickel oxide powder containing 10,000% lanthanum oxide, and
By baking at 700°C in the air after drying,
12% by weight of lanthanum oxide-containing alumina powder and 3% by weight of nickel oxide were coated and carried on the coated carrier.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate, dried, and then calcined in the air at 900°C to obtain a finished catalyst in which 8% by weight of palladium was supported on the finished catalyst.

Example 5 A cordierite honeycomb carrier having the same shape as the carrier used in Example 1 was coated with a mixed slurry of alumina powder containing 5x R% lanthanum oxide and nickel oxide powder, dried, and heated at 700°C in air. 20% of lanthanum oxide containing alumina powder per coated carrier
2.5% by weight of nickel oxide was supported on the coating.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate, dried, and then calcined in the air at 900°C to obtain a finished catalyst in which 12% by weight of palladium was supported on the finished catalyst.

Example 6 Using a sufficiently warmed cylindrical combustor, the catalyst obtained in Example 1 was placed in front of the front stage, and the catalyst obtained in Example 4 was placed in the rear (middle stage) of the front stage.
The catalyst obtained in Example 2 was packed in the latter stage, and the catalyst obtained in Example 2 was packed in the latter stage.

Next, under the conditions of a catalyst bed inlet temperature of 350°C and a combustor internal pressure of 10 atm, a methane-air mixture gas containing 3.0% methane was pumped from the upstream side of the catalyst bed at a rate of about 167N7FL per hour ( A combustion experiment was conducted by simultaneously introducing methane equivalent to 1.1% by volume into a position 30 m behind the catalyst bed outlet. In this case, the linear velocity at the entrance of the catalyst layer was about 30 m/sec.

The results obtained are shown in Table-1.

Example 7 In Example 6, the catalyst obtained in Example 1 was placed in front of the front stage, the catalyst obtained in Example 5 was placed behind the front stage (middle stage), and the catalyst obtained in Example 3 was placed in the rear stage. A combustion experiment was conducted in the same manner as in Example 6 except that the catalyst was placed.

The results obtained are shown in Table-1.

Example 8 25 mm diameter with 200 ton/in2 aperture.
4#, 1-50cm Cordie Lai 1-honeycomb carrier,
A mixed slurry of alumina powder and nickel oxide powder containing 7% by weight of lanthanum oxide is coated, dried, and then calcined in air at 700°C to produce 16 layers of lanthanum oxide-containing alumina powder per finished catalyst. feet%,
4% by weight of nickel oxide was supported on the coating.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and then immersed in air for 900 minutes.
By firing at C, a finished catalyst was obtained in which 3% by weight of palladium and 0.5% by weight of platinum were supported on the finished catalyst.

Example 9 Using a sufficiently warmed cylindrical combustor, the first stage was filled with the catalyst obtained in Example 8, and the second stage was filled with the catalyst obtained in Example 2, and at an inlet temperature of 350°C, 2.7% by volume was 16 methane-air mixture gas containing methane per hour under normal pressure
．． 7 N conditions (STP) were introduced to measure combustion efficiency and catalyst layer outlet temperature. In this case, the linear speed of the catalyst is approximately 30 m.
/second.

As a result, the combustion efficiency was 82%, and the catalyst layer outlet temperature was approximately 8.
The temperature was 80°C.

Next, when the methane concentration was set to 4.1% by volume, the combustion efficiency became 100%, and a clean combustion gas containing substantially no unburned hydrocarbons, -M carbon, and nitrogen oxides was obtained. In this case, the temperature at a point 1001 m from the end of the catalyst layer is approximately 1
The temperature at the outlet of the catalyst layer was approximately 920°C.
Met.

Subsequently, a similar combustion experiment was conducted by introducing methane equivalent to 2.7% by volume from upstream of the catalyst bed, and introducing methane equivalent to the remaining 1.4% by volume from 30 m behind the outlet of the catalyst bed.

As a result, the catalyst bed outlet temperature was about 880°C, and clean combustion gas of about 1300°C was obtained. Moreover, this performance was maintained continuously for 1000 hours.

Example 10 In the same manner as in Example 9, using the catalysts shown in Table 2, 2
．． Methane equivalent to 7% by volume is added from upstream of the catalyst layer, and the remaining 1.
Table 2 shows the results of a combustion experiment in which methane equivalent to 4% by volume was introduced from 30 m behind the outlet of the catalyst bed, and the catalyst bed temperature did not decrease in activity if the catalyst system according to the present invention was used. Although the temperature was maintained below 1000°C, clean combustion gas of about 1300°C was obtained.

Claims (1)

[Scope of Claims] (1) A catalyst layer containing palladium, platinum, and nickel oxide as active ingredients is provided on the upstream side and a catalyst layer containing platinum as the active ingredient is provided on the downstream side with respect to the flow of fuel-air mixed gas. A combustion catalyst system characterized by: (2) The catalyst system according to claim (1), wherein each active component is dispersed and supported on a monolithic carrier coated with alumina. (3) Claim (2) characterized in that the alumina coating layer is stabilized by at least one oxide selected from the group consisting of lanthanum, yttrium, cerium, samarium, neodymium, and praseodymium. Catalyst system as described. (4) The combustion catalyst system according to claim (1), (2) or (3), characterized in that a methane-based fuel is used as the fuel. (5) A combustion catalyst system comprising a catalyst layer containing palladium, platinum, and nickel oxide as active ingredients on the front stage side and a catalyst layer containing platinum as an active component on the rear stage side for the flow of fuel-air mixed gas. A combustion method characterized in that the combustion gas is heated to a temperature at which secondary combustion is induced by combusting only a part of the fuel in the system. (6) In the combustion method described in claim (5),
A combustion method characterized in that the temperature of combustion gas is raised to 600 to 900°C in the first stage catalyst layer and to 750 to 1000°C in the second stage catalyst layer. (7) The method according to claim (5) or (6), characterized in that secondary combustion is caused by further supplying secondary fuel to the gas whose temperature has been raised to a humidity that induces secondary combustion. (8) With respect to the flow of fuel-air mixed gas, a catalyst layer containing palladium and platinum as active ingredients in the former stage, a catalyst layer containing palladium and nickel oxide as active ingredients in the middle stage, and a catalyst layer containing platinum as active ingredients in the latter stage. A combustion catalyst system characterized by being provided with a catalyst layer. (9) The catalyst system according to claim (8), wherein each active component is dispersed and supported on a monolithic carrier coated with alumina. (10) Claim (9) characterized in that the alumina coating layer is stabilized with at least one oxide selected from the group consisting of lanthanum, yttrium, cerium, samarium, neodymium, and praseodymium. Catalyst system as described. (11) The combustion catalyst system according to claim (8), (9) or (10), characterized in that a methane-based fuel is used as the fuel. (12) With respect to the flow of fuel-air mixed gas, a catalyst layer containing palladium and platinum as active ingredients in the former stage, a catalyst layer containing palladium and nickel oxide as active ingredients in the middle stage, and a catalyst layer containing platinum as active ingredients in the latter stage. A combustion method characterized by using a combustion catalyst system provided with a catalyst layer that combusts only a part of the fuel in the system and raising the temperature of combustion gas to a temperature at which secondary combustion is induced. (13) In the combustion method described in claim (12), the temperature of the combustion gas is raised to 500 to 800°C in the first catalyst layer, 650 to 900°C in the middle catalyst layer, and 800 to 1000°C in the second catalyst layer. A combustion method characterized by: (14) The method according to claim (12) or (13), characterized in that secondary combustion is caused by further supplying secondary fuel to the gas heated to a temperature that induces secondary combustion.