JPS61252409A - Method of igniting methane fuel - Google Patents

Abstract

PURPOSE:To enable a complete combustion of fuel by a method wherein a flow of mixture gas containing methane and molecular oxygen is passed through three active catalyst layers composed of a front stage, an intermediate stage and a rear stage, respectively. CONSTITUTION:A catalyst having palladium as its active constituent is divided into three layers: a catalyst capable of being ignited at a low temperature and capable of increasing a fuel gas temperature up to 700-800 deg.C is arranged at the front stage at the fuel gas inlet, another catalyst capable of increasing the temperature up to 750-900 deg.C is arranged at an intermediate stage layer and a hot-temperature ignition catalyst capable of increasing the temperature up to 900-1,100 deg.C is arranged at the rear stage layer, respectively, and each of them is most preferably designed. As the catalyst to be used in the front stage layer, it has palladium and platinum as its active constituent. As the catalyst to be used in the intermediate stage layer, it contains palladium and platinum as its active constituent. As the catalyst to be used in the rear stage layer, it contains palladium and platinum as its active constituent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion method for catalytically burning fuel. Specifically, the present invention catalytically burns flame-retardant methane or a natural gas fuel mainly composed of methane with molecular oxygen on a catalyst to produce nitrogen oxides (hereinafter referred to as NOx),
- A catalyst system for obtaining combustion gas that does not substantially contain harmful components such as carbon oxides (hereinafter referred to as CO) and unburned hydrocarbons (hereinafter referred to as UHC), and using the resulting heat as a variety of energy sources. This relates to the combustion method used.

(Prior art) A catalytic combustion system is known in which a dilute gas mixture of fuel 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. be.

Furthermore, using such a catalytic combustion system, e.g.
It is well known that when obtaining combustion gases at temperatures between 0°C and 1.500°C, even if air is used as the oxygen source, little or no NOx is generated and substantially no C6 and UHC are obtained. It is being

Various systems have been proposed to utilize this clean, high-temperature combustion gas to obtain 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.

Furthermore, research is being conducted on the application to so-called heat and power supply systems (cogeneration), which use city gas as fuel to operate gas turbines at energy consumption sites to generate electricity and use the exhaust gas for hot water heating, etc. be.

(Problem to be Solved by the Invention) The gas turbine used for this cogeneration has a lower turbine inlet temperature of 900 to 1100'C compared to that used for normal power plants, and under such conditions When using a catalyst, it is impossible to induce secondary combustion downstream of the catalyst layer, especially since the fuel is 13A city gas whose main component is extremely flame-retardant methane. , it is essential to achieve complete combustion through a catalytic reaction.

Therefore, the catalyst used for the purpose of the present invention has a high activity of 90 to 11, which ignites 13A city gas containing flame-retardant methane as its main component at low temperature and leads to complete combustion.
Heat resistance that can withstand temperatures of 00'C and long-term stability are required.

As a catalyst suitably used for this purpose, a noble metal catalyst is suitable, and a catalyst containing palladium as an active main component is particularly desirable.

Catalysts containing palladium as the main active component are known to have particularly excellent low-temperature ignitability of methane and excellent heat resistance to about 1000°C.

However, when a conventional catalyst containing palladium as an active ingredient is used for the purpose of the present invention, the palladium is oxidized into methane because it is exposed to a high concentration of oxygen near the inlet of the catalyst layer, even though the temperature is below 500°C. On the other hand, in the high-temperature region near the outlet of the catalyst layer, the combustion reaction is suppressed, probably due to a change in the combustion activity of palladium, and the combustion gas temperature is reduced to 750℃.
It was discovered that there is a drawback in that it does not rise to high temperatures above ℃.

The present inventors focused on the excellent characteristics of a catalyst containing palladium as an active ingredient, and completed the present invention as a result of intensive research to overcome the drawbacks of conventional catalysts.

(Means for Solving the Problems) The present invention ignites methane, which is said to be relatively flame-retardant among hydrocarbons, or a natural gas fuel mainly composed of methane at a low temperature using a catalyst at high linear velocity. The present invention also provides a combustion method using a catalyst system that is suitably used in a combustion system that completely burns the gas in the catalyst layer and raises the gas to a target temperature, that is, a high temperature of 900 to 1100°C.

That is, a catalyst system that can be adapted to the purpose of the present invention divides a catalyst containing palladium as an active component into three layers, and can ignite the first layer on the fuel gas inlet side at a low temperature, and the temperature of the combustion gas can be lowered to 700 to 700℃. A catalyst that can raise the temperature up to 800°C, a catalyst that can raise the temperature up to 750-900'C used in the middle layer, and a catalyst that can raise the temperature up to 750-900'C used in the latter layer.
It is made up of optimally designed catalysts for high-temperature combustion that can raise temperatures up to 00°C, and the catalyst used in the front layer contains palladium and platinum as active ingredients, and the catalyst used in the middle layer contains palladium and platinum as active ingredients. The catalyst contains palladium and nickel as active components, and the catalyst used in the latter layer contains palladium and platinum as active components.

According to the present invention, the presence of a small amount of platinum in the front stage catalyst near the gas inlet of the catalyst system prevents deterioration of methane ignition performance due to palladium oxidation, and maintains low-temperature ignition performance for a long time. In addition, the combustion gas temperature can be raised to 700 to 800°C, and then in the middle layer catalyst containing palladium and nickel, the presence of nickel oxide stably supplies oxygen to palladium, so that combustion is prevented. is promoted, and the combustion gas is 75
It becomes possible to reach temperatures from 0 to 900 °C.

Furthermore, in the subsequent stage catalyst, combustion is further promoted by the synergistic effect of palladium and platinum, the fuel is completely combusted, the combustion gas is able to reach a temperature of 900 to 1100°C, and the combination with palladium is further promoted. It was discovered that the coexistence of PtO2 prevents platinum from being oxidized to PtO2 and sublimating even in this high temperature range.

As a result, the entire catalyst layer ignites methane or natural gas fuel containing methane as a main component at a low temperature.
It is now possible to raise the temperature of combustion gas to 00℃, and maintains this performance for a long time.
This made it possible to stably obtain high-temperature combustion gas.

The catalysts for the front layer, middle layer, and rear layer may be prepared separately, and each catalyst may be directly connected or installed with a space between them, or in the case of an integrated catalyst, the front layer catalyst may be placed at the inlet portion. A finished catalyst may be obtained by supporting an intermediate layer catalyst in the intermediate portion and a rear layer catalyst in the outlet portion.

The shape of the catalyst is preferably a monolith type for the purpose of reducing pressure loss. Any monolith carrier that is normally used in the field can be used,
In particular, heat-resistant ceramic materials such as cordierite, mullite, α-alumina, zirconia, titania, titanium phosphate, aluminum titanate, betalite, subodumene, aluminosilicate, magnesium silicate, zirconia spinel, zircon mullite, silicon carbide, and silicon nitride. Metal materials such as kanthal, feclaroy, etc. are used.

The cell size of the monolithic carrier is preferably large as long as combustion efficiency is not reduced; each catalyst layer may have the same cell size or may be a combination of different cell sizes; typically - 40 to 400 cells per square inch. are used.

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

The catalyst used in each catalyst layer is usually alumina, silica alumina, magnesia, titania,
Used by coating with active refractory metal oxide such as 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 components palladium and platinum or palladium and nickel are impregnated and catalyzed in the form of salts in aqueous solution.

Alternatively, the active ingredient can be supported on an active refractory metal oxide in advance and then catalyzed by coating it on a monolithic carrier. It can also be catalyzed by mixing it with and coating it on a monolithic support.

Regarding the amount of active components supported in the catalyst forming the first stage layer, palladium is supported at 2 to 300 q, preferably 10 to 150 CJ, per Ω of completed catalyst, and platinum is supported at a weight ratio of 0.2 to 50% relative to palladium. Preferably 0.5~
It is suitable to use it in an amount of 30%.

In the catalyst used in the middle layer, palladium is supported at 2 to 300 C per 1 g of the finished catalyst, preferably 10 to 150 Q, and the supported amount of the nickel component is NiO2 per 1 g of the finished catalyst.
A suitable amount is 5 to 300Q, preferably 10 to 200g.

Regarding the catalyst used in the latter layer, the amount of palladium supported is 2 to 200Q, preferably 5 to 100Q per finished catalyst IQ, and the amount of platinum supported is 1 to 200g, preferably 5 to 100g, and the combination of palladium and platinum is suitable. The ratio is 1:1~100
: 1, preferably 2:1 to 50:1.

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 over 80% methane, although the composition ratio varies depending on the region of production. Further, fermented methane from activated sludge treatment and low-calorie methane gas from coal gasification are also fuels used in the present invention. Naturally, more flammable propane, light oil, etc. can also be used.

(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 Diameter 25.4 with 200 cells/inch square aperture
7 on a cordierite honeycomb carrier with a length of 5Q+nm
A slurry of alumina powder containing lanthanum oxide in weight percent was coated and fired in air at 700°C to form carrier 1.
120g of coating was carried per Q.

Next, this was immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and calcined in air at 900°C.
20q as palladium, 4 as platinum per 1Ω of carrier
A completed catalyst was obtained by supporting q.

Example 2 Using an alumina powder containing 8% by weight of lanthanum oxide and 2% by weight of neodymium oxide, 150 g of the alumina powder was coated and supported per 1 fJ of carrier in the same manner as in Example 1.

The carrier was then immersed in an aqueous solution containing palladium nitrate and dinitrodiaminoplatinum, dried and dried in air for 90 minutes.
250 as palladium per 1Q of carrier,
A completed catalyst was obtained by supporting 5Q as platinum.

Example 3 25.4 diameter with 200 cells/inch square aperture
11111. A mixed slurry of alumina powder containing 5% lanthanum oxide and titania powder containing 2% cerium oxide was coated on an aluminum honeycomb carrier having a length of 50 am, and the slurry was fired at 900°C in air to obtain carrier 1Q. 100Q of alumina containing 51a% by weight of lanthanum oxide and 20Q of titania containing 2% by weight of cerium oxide were coated and supported.

Then, in the same manner as in Example 2, it was calcined in air at 800°C to support 3q of palladium 10Q1 platinum per 1Ω of carrier to obtain a finished catalyst.

Example 4 25.4 diameter with 100 cells/inch square aperture
A mullite honeycomb carrier with a length of 11 m and a length of 5 QI 1 m was coated with a slurry of alumina powder containing 5% by weight of lanthanum oxide and 2% by weight of barium oxide.
It was fired at 0° C. to coat and support lanthanum oxide and barium oxide-containing alumina 180Q per 1Q of carrier.

Then, in the same manner as in Example 1, by firing at 800°C in air, 15Q, palladium, and
A completed catalyst was obtained by supporting 3 g of platinum.

Example 5 A honeycomb carrier similar to that used in Example 1 was coated with a mixed slurry of alumina powder and nickel oxide powder containing 7% by weight of lanthanum oxide, and fired in air at 700°C to obtain 1 g of carrier. 120Q of lanthanum oxide-containing alumina and 30A of nickel oxide were coated and supported.

Next, this was immersed in an aqueous solution containing palladium nitrate and fired at 900°C in air to obtain a
[20C] was supported as palladium to obtain a completed catalyst.

Example 6 In the same manner as in Example 1, 8% by weight lanthanum oxide and 2
150 g of alumina containing neodymium oxide (wt%) was coated and supported (wheat) by immersing it in an aqueous solution containing palladium nitrate and nickel nitrate and calcining it in air at 700°C to obtain 25 Q of palladium per Ω of the support.
A completed catalyst was obtained by supporting 50q of nickel as nickel oxide.

Example 7 A honeycomb carrier similar to that used in Example 1 was coated with a mixed slurry of alumina containing 5% by weight of lanthanum oxide, zirconia containing 2% by weight of yttrium oxide, and nickel hydroxide powder, and heated in air at 800°C. After baking, carrier 1
120 g of lanthanum oxide-containing alumina, 30 q of yttrium oxide-containing zirconia, and 40 Cl of nickel oxide were supported per Ω.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate, dried, and calcined in air at 700°C to support 15Q as palladium per 1Ω of carrier to obtain a completed catalyst.

Comparative Example 1 A finished catalyst was obtained in the same manner as in Example 1 except that it did not contain platinum.

Comparative Example 2 A finished catalyst was obtained in the same manner as in Example 1, except that 10 g of platinum was supported per 1Q of carrier without containing palladium.

Example 8 Using a sufficiently warmed cylindrical combustor, from the fuel gas inlet side, the catalyst obtained in Example 1 was placed in the first layer, the catalyst obtained in Example 5 was placed in the middle layer, and the catalyst obtained in Example 5 was placed in the second layer. A methane-air mixture containing 3% by volume of methane was charged with the catalyst obtained in Example 2 at an inlet temperature of 350'C at 11.1% per hour. Nm3 was introduced and the combustion efficiency and catalyst layer outlet temperature were measured.

In this case, the linear velocity at the inlet of the catalyst layer was about 20 m/sec.

As a result, the catalyst bed outlet temperature was approximately 1030'C, and the combustion efficiency was 100% for Ti, NOx, and Go.

A clean combustion gas containing substantially no UHC was obtained.

Moreover, this performance was maintained continuously for 500 hours.

Example 9 A combustion experiment was conducted in the same manner as in Example 8, using the catalyst shown in Table 1, and introducing methane equivalent to 3% by volume from upstream of the catalyst layer. As a result, the results were as shown in Table 1. there were.

(Left below) (Effect of the invention) If the catalyst system according to the present invention is used, the catalyst layer temperature will be 11
The combustion efficiency continued at 100% while maintaining the temperature below 00°C, and clean combustion gas was obtained for a long period of time.

However, the catalyst system using the catalyst of Comparative Example 1 in the first layer quickly became unable to ignite, and the catalyst system using the catalyst of Comparative Example 2 in the first wheat layer had high activity, but the catalyst did not reach high temperatures. As a result, the activity rapidly decreased and sublimation of platinum was observed.

On the other hand, the method of the present invention is an excellent method as is clear from the examples.

Therefore, the catalyst of the present invention or the combustion system using the catalyst can be optimally incorporated into a gas turbine system for power generation as described above, but it is also suitable for use in power generation boilers, heat recovery boilers, and city gas heating systems. It is used to efficiently recover heat and power.

Claims (4)

[Claims] (1) With respect to the flow of a mixed gas containing methane and molecular oxygen, an active catalyst layer containing palladium and platinum on the front stage side, an active catalyst layer containing palladium and nickel on the middle stage, A method for combustion of methane-based fuel, characterized in that methane in the mixed gas is completely combusted in the catalyst system using a catalyst system having an active catalyst layer containing palladium and platinum on the rear stage side. (2) Each catalytically active component is at least one member selected from the group consisting of alumina, titania, and zirconia.
The method according to claim 1, characterized in that the method is carried out in a dispersed manner on a monolithic carrier coated with an oxide of the species. (3) The coating oxide is stabilized with an oxide of at least one element selected from the group consisting of lanthanum, yttrium, cerium, samarium, neodymium, praseodymium, magnesium, calcium, strontium, and barium. A method according to claim 2, characterized in that: (4) The temperature of the catalytically combusted combustion gas is in the range of 700 to 800°C at the outlet of the first stage catalyst layer, 750 to 900°C at the outlet of the middle stage catalyst layer, and 900°C at the exit of the second stage catalyst layer. 4. A method according to claim 1, 2 or 3, characterized in that the temperature is increased to a range of -1100<0>C.