JPS60205116A - Combustion catalyst system and combustion therewith - Google Patents

Abstract

PURPOSE:To ignite natural gas at low temperature and raise a temperature of ignited gas up to a temperature of 750-1,000 deg.C by a method wherein a first layer is provided with a catalyst layer having as active component palladium and platinum, a second layer is provided with a catalyst layer having as active component platinum and a third layer is provided with a catalyst layer having as active component palladium or both palladium and platinum in an order from the inlet side, respectively. CONSTITUTION:A first layer catalyst having a superior characteristic of ignition at low temperature and having as active component palladium and platinum, a second layer catalyst having as active component platinum and a third layer catalyst having as active component palladium or both palladium and platinum are combined to each other. At the first layer catalyst near the inlet of the catalyst system, a reduction in igniting characteristic of methane is prevented and it is possible to increase the temperature of combustion gas up to 700- 800 deg.C, then it is increased up to 750-900 deg.C through the second layer catalyst and finally the combustion gas is reached to a temperature of 800-1,000 deg.C through the third layer catalyst.

Description

DETAILED DESCRIPTION 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 natural gas fuel mainly composed of methane on a catalyst to produce nitrogen oxides (hereinafter referred to as NOx), -carbon oxides (hereinafter referred to as CO), Unburned hydrocarbons (hereinafter referred to as UHC)
The object of the present invention is to provide a catalyst system that obtains incinerated gas substantially free of harmful components such as, and uses the calorific value as various energy sources, and a combustion method using the same.

More specifically, the present invention uses a catalyst to ignite methane, which is said to be relatively flame-retardant among hydrocarbons, or natural gas fuel containing methane as its main component at a low temperature under high linear velocity, thereby inducing secondary combustion. The temperature is raised in the trench to a temperature sufficient to achieve the target temperature, and then secondary fuel is introduced as necessary to burn the remaining unburned fuel and secondary fuel to reach the target temperature or higher. The object of the present invention is to provide a catalyst system suitably used in a combustion system for increasing the temperature and a combustion method using the catalyst system.

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 produce high-temperature combustion gas.

Furthermore, using such a catalytic combustion system, e.g.
When obtaining combustion gas at a temperature of 0°C to 1500°C, little or no NOx is generated even if air is used as the oxygen source, and it is often obtained as a combustion gas that does not substantially contain UHC. It is well known.

Various systems have been proposed to generate heat or power using this clean, high-temperature combustion gas, and systems for treating general commercial exhaust gas and for recovering heat and power have already been put into practical use.

In addition, in recent years, in response to increasing NOx regulations,
More and more systems are being developed that utilize this high-temperature combustion gas as a primary power source for L-type gas turbines and the like.

When used for these purposes, the stranded mo.1-gas is 10
It is normal to reach a high temperature of 00 to 1300℃,
In order to improve the efficiency of gas turbines, there is a trend towards higher temperatures.

If a catalyst is used under such conditions, a normal catalyst will deteriorate rapidly due to high temperatures, and in the worst case scenario, the catalyst carrier may melt down and fly off, damaging turbine blades and other parts. be.

As a combustion method that avoids catalyst deterioration and damage as described above and achieves the same purpose, 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 catalyst layer is heated to a temperature that induces secondary combustion. Either perform secondary combustion of the remaining unburned fuel at the rear, or perform secondary combustion of the remaining unburned fuel and newly added secondary fuel by burning all of the secondary fuel if necessary. A combustion method has been discovered that produces clean combustion gas at or above the desired temperature.

In this case, the purpose of combustion in the catalyst layer is to raise the gas temperature to a temperature that induces secondary combustion, and it is not necessarily necessary to completely burn the gas in the catalyst layer, but to raise the gas temperature to a temperature that induces secondary combustion. If the gas temperature reaches The more unburned fuel remaining, the better.

The entire amount of fuel whose temperature can be changed to the desired temperature may be introduced into the catalyst layer, and fjμ may be combusted to form a catalytic product, and then the remaining unburned fuel may be subjected to secondary combustion, but some of the fuel may be left behind. This may then be introduced as a secondary fuel from behind the catalyst layer and combined with the remaining unburned fuel for secondary combustion. In this case, it is possible to avoid making the melting layer temperature change as high as necessary, and deterioration of the catalyst and loss of <1 can be avoided, which is preferable.

The safe temperature for inducing secondary ignition depends on the type of fuel,
It is determined by the residual fuel concentration (theoretical adiabatic combustion gas temperature), linear velocity, etc., but varies greatly depending on the J+Ii force 1 of the fuel.

In other words, in the case of easily flammable fuels such as propane and diesel oil, a temperature of about 700°C is sufficient under normal usage conditions, but when using flame-retardant methane or natural gas whose main component is methane, 7, although it varies depending on the conditions of use.
High temperatures of 50-1000°C are required.

Due to recent fuel circumstances, the fuel used for this purpose is mainly methane or natural gas containing methane as its main component, and the present invention aims at igniting the flame-retardant fuel at a high linear velocity and at as low a temperature as possible. The object of the present invention is to provide a catalyst that can raise the combustion gas temperature to a temperature of 750 to 1000°C.

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

A catalyst containing palladium as an active component is particularly excellent in low-temperature ignition of methane and has excellent heat resistance at about 1000°C.

However, when a catalyst containing palladium as an active component is used for the purpose of the present invention, 50%
Palladium is oxidized and loses its ability to ignite methane when exposed to high rotation oxygen at temperatures below 0.8C;
The temperature near the outlet of the catalyst layer becomes high, and the combustion reaction by the catalyst is suppressed, probably due to a change in the oxidation state of palladium, and the temperature of the combustion gas does not rise above 750°C. I found it.

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

That is, the catalyst system according to the present invention includes a first layer catalyst having excellent low-temperature ignitability which is made of palladium and platinum as active ingredients, a second layer catalyst which is made of platinum as an active ingredient, and then a second layer catalyst which is made of platinum as an active ingredient. Alternatively, it is formed by optimally combining a third layer catalyst made of palladium and platinum.

According to the present invention, the presence of a small amount of platinum in the first layer catalyst near the entrance of the catalyst system prevents deterioration of methane ignition performance due to palladium oxidation, and maintains low-temperature ignition performance for a long time. And the combustion gas temperature is 700~
The temperature of the combustion gas was then raised to 750-900°C by the second layer catalyst containing platinum as an active ingredient, and combustion, which is thought to be caused by a change in the oxidation state of radium, occurred. It is carried to the third layer avoiding the temperature range where it is suppressed.

It was discovered that combustion is promoted by the third-layer catalyst, which has existed for a long time and has excellent heat resistance, and the combustion gas can reach a temperature of 800 to 1000°C.

As a result, the catalyst layer as a whole was able to ignite methane or natural gas fuel containing methane as its main component at a low temperature.
It has become possible to raise the temperature of combustion gas to 1000°C, and to maintain this performance for a long time.

Each layer catalyst may be prepared separately and each catalyst may be directly connected or installed with a space provided between them, or a complete catalyst may be obtained by supporting the catalysts of each layer in an integrated catalyst.

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

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

The total catalyst layer length varies depending on the inlet 6 speed used, but
Due to the need to reduce pressure loss, 1/K50~5000
The length of each catalyst layer is optimally selected depending on the usage conditions such as inlet linear velocity and inlet temperature, but usually each layer is 25 mm long.
~250 dragons will be adopted.

The catalyst used in No. 11- is usually on the above-mentioned monolithic carrier,
Alumina, silica-alumina, magnesia, titania,
Used by coating with active refractory metal oxide such as zirconia or silica-magnesia. In particular, alumina or zirconia is preferred, and alkaline earth metal oxides such as barium and strontium, and rare earth metal oxides such as lanthanum, cerium, neodymium, and praseodymium are added.
It is preferable to use it after stabilizing it.

Thereafter, the active principal components of palladium and platinum are impregnated and catalyzed in the form of water-soluble salts.

Alternatively, the active main component can be supported on an active, refractory metal oxide in advance and then catalyzed by coating it on a monolithic carrier.

Palladium is supported in a proportion of 2 to 1,002, preferably 5 to 50, per finished catalyst 11, and platinum is added in an amount of 02 to 50%, preferably 05 to 30%, based on palladium.

The catalyst used in the second layer can be catalyzed by supporting platinum in the same way, but in this case the catalyst is too highly active,
There is a possibility that the temperature in the catalyst layer may rise to 1000° C. or higher, causing deactivation phenomena such as sublimation of platinum. Please take this lightly
Catalyst I8: In order to keep the temperature below 950℃, there is a method of reducing the amount of platinum supported, a method of firing the finished catalyst at a high temperature exceeding 1000℃ before use, a method of using platinum black, etc. Methods using coarsened platinum particles, methods of optimally selecting catalyst cell size and layer length, etc. have been discovered, but these methods depend on the conditions of use, i.e., the type of fuel,
4 degrees (theoretical adiabatic combustion gas temperature), the temperature can be optimally selected depending on the temperature, etc.

In addition, the catalyst used in the third layer can be catalyzed by supporting palladium or palladium and platinum in the same manner as the catalyst used in the first layer 1). In this case, the amount of palladium 9 supported is 11 Appropriately, the supported amount of platinum is 0 to 202 f, preferably 0 to 10 f, preferably 5 to 100 f.

Alternatively, the catalyst may be directly supported on a monolithic carrier without using the catalyst-coactive refractory metal oxide in each layer.

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. In addition, 1Δ 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 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 can also be incorporated into a power generation boiler, a heat recovery boiler, or a combustion system that uses gas from a gas engine. It is used to efficiently recover heat and power through post-processing, city gas heating, etc.

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

Example 1 25.4 diameter with 200 cells/inch square aperture
ml, length 50 rhymes cordierite/S nicum carrier,
A slurry of alumina powder containing 5% by weight of lanthanum oxide was coated and fired at 900°C in air to form carrier 1.
The coating amount was 100 grams per one coat.

This was then soaked in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried and calcined in air at 700°C.
A complete catalyst was obtained by loading 102 pieces of palladium and 22 pieces of platinum on 11 pieces of carrier.

Example 2 In the same manner as in Example 1, a 5-layer ITS lanthanum oxide-containing alumina powder of Xll Atashi 1001 was loaded with a nuclide.

Next, this was immersed in an aqueous solution containing chloroplatinic acid, dried, and calcined in air at 900° C., so that 22 platinum particles were supported per 11 supports to obtain a completed catalyst.

Example 3 In the same manner as in Example 1, alumina powder containing 7 blocks of neodymium oxide was supported on the carrier 11 and covered with 1502.

Next, in the same manner as in Example 1, 20 2 of palladium and 52 of platinum were supported on carrier 11 to obtain a completed catalyst.

Example 4 Using alumina powder containing 7% by weight of lanthanum oxide and 3% by weight of neodymium oxide, the alumina powder was used as carrier 1! in the same manner as in Example 1. 120 per? It was coated.

Next, this was immersed in an aqueous solution containing a nitric acid solution of dinitrodiaminoplatinum, dried, and calcined in air at 1150°C, thereby supporting 15F as platinum on the carrier 11 to obtain a completed catalyst.

Example 5 A mullite honeycomb carrier having a diameter of 25° and a length of 15 mm with openings of 40 cells/square inch was coated with a slurry of alumina powder containing 10% by weight of lanthanum oxide and 20% by weight of cerium oxide. Then, it was calcined in air at 1000° C., and the support 1 was covered with a sheet 802 to support it.

Next, in the same manner as in Example 4, 15f of platinum was supported on the carrier 11 to obtain a completed catalyst.

Example 6 A honeycomb carrier similar to that used in the flow side work was coated with a slurry of cerium-limited alumina powder containing 5 μm (fIi') and platinum powder having an average particle size of 5 μm, and then coated and dried. By firing at 900° C., 1002 of alumina containing 5wt i% cerium oxide and 02 of platinum were supported on carrier 11 to obtain a completed catalyst.

Example 7 A finished catalyst was obtained in exactly the same manner as in Example 1 except that platinum was not contained.

Example 8 A finished catalyst was obtained in exactly the same manner as in Example 3 except that it did not contain platinum.

Comparative Example 1 A completed catalyst was obtained in exactly the same manner as in Example 4 except that the catalyst was calcined at 800° C., and 152 platinum was supported on carrier 11.

Example 9 Using a cylindrical combustor with sufficient heat insulation, the first
The layer was filled with the catalyst obtained in Example 1, the second layer was filled with the catalyst obtained in Example 2, the third layer was filled with the catalyst obtained in Example 1,
At an inlet temperature of 350°C, a methane-air mixture containing 3 volumes of methane was heated to 16.7 NIIL per hour.
'The combustion efficiency and catalyst bed outlet temperature were measured. In this case, the linear velocity at the entrance of the catalyst layer was about 30 m/sec.

As a result, the combustion efficiency was about 81 degrees, and the catalyst layer outlet temperature was about 920°C.

Next, when the methane concentrate was increased to 41 volumes, the combustion efficiency became 100%, and a clean combustion gas containing substantially no unburned hydrocarbons, carbon oxides, or nitrogen oxides was produced. In this case, the temperature at a point 100 meters behind the catalyst layer is approximately 1
The temperature reached 300℃, but the catalyst layer outlet temperature was about 925℃.
Met.

Subsequently, a similar combustion experiment was carried out by introducing methane equivalent to 3 volumes from upstream of the catalyst nozzle and the remaining methane equivalent from 1.1 volumes from 30 nz behind the catalyst bed outlet.

As a result, the velcro reduction at the outlet of the catalyst bed was about 920°C, and clean combustion gas of about 1300''C was returned.This property hd was maintained continuously for 500 hours.

Example 10 In the same manner as in Example 7, using the catalysts shown in Table 1, 3
A combustion experiment was carried out by introducing methane equivalent to the capacity of the catalyst layer from upstream of the catalyst layer, and introducing methane equivalent to the remaining 1.1 volume from 30 m behind the catalyst layer outlet.

The results are shown in Table 1, and the use of the catalyst system according to the present invention shows that the temperature value of the catalyst layer does not decrease in activity.
Approximately 1300℃ despite K being maintained below 0℃
However, the catalyst Z stem using the catalyst of Comparative Example 1 on the upstream side rapidly became unable to ignite, and the catalyst system using the catalyst of Comparative Example 2 on the downstream side However, the activity was too high and the catalyst layer temperature was not high enough, resulting in a rapid decrease in activity and a sublimation phenomenon of platinum was observed.

Claims (6)

[Claims] (1) From the inlet side, the first layer is a catalyst layer containing palladium and platinum as active ingredients, the second layer is a catalyst layer containing platinum as an active ingredient, and the third layer is palladium. Alternatively, a combustion catalyst system comprising a catalyst layer containing palladium and platinum as active ingredients. (2) The catalyst system according to claim (1), wherein each active ingredient is dispersed and supported on a monolithic carrier coated with alumina. (3) Claim (2) 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. (4) Using the catalyst system according to claim m, (2) or (3), the combustion gas is heated to a temperature at which only a part of the fuel is combusted and secondary combustion is induced in the system. A combustion method characterized by: (5) In the combustion method described in claim (4), the combustion gas temperature is set at 700 to 800°C in the first catalyst layer.
, a combustion method characterized by raising the temperature to 750 to 900°C in the second catalyst layer and to 800 to 1000°C in the third catalyst layer. (6) The method according to claims (4) and (5), characterized in that secondary combustion is caused by further supplying secondary fuel to the gas whose temperature has been raised to a temperature that induces secondary combustion.