JPS60205115A - Combustion catalyst system and combustion therewith - Google Patents

Abstract

PURPOSE:To ignite natural gas at low temperature and increase the temperature of ignited gas up to 750-1,000 deg.C by a method wherein a catalyst layer having as active component palladium and platinum is arranged at a front stage and another catalyst layer having as an active component a platinum is arranged at a rear stage in respect to a flow of fuel-air mixture gas. CONSTITUTION:A catalyst is divided into two layers, each of the catalysts which can be ignited at a relative low temperature applied in a front stage layer and a high combustible catalyst to be applied in a rear stage layer in which a combustion gas temperature can be increased up to 750-1,000 deg.C is properly designed. As the catalyst to be used in the front stage layer, the active component is composed of palladium and platinum, the catalyst to be applied in the rear stage layer is composed of platinum as an active component and they are prevented from being over a high temperature of more than 1,000 deg.C. As a result, it becomes possible to ignite methane or natural gas fuel having as its major component methane at a low temperature and to raise the combustion gas up to a temperature of 750-1,000 deg.C and it is possible to continue its performance for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic combustion system for catalytically burning 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), and nitrogen oxides. The present invention provides a catalyst system that obtains combustion gas that does not substantially contain harmful components such as combustible hydrocarbons (hereinafter referred to as UHC), and uses its calorific value as various energy sources, and a combustion method using the same. be.

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 to a temperature K sufficient to achieve the target temperature, then secondary fuel is introduced as necessary to combust the remaining unburned fuel and the secondary fuel, and the temperature is raised to the target temperature or higher. The present invention provides a catalyst system suitably used in a combustion system and a combustion method using the same.

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 from 00°C to 150-0°C, even if air is used as the oxygen source, -C generates little or no NOx, and it is often obtained that does not substantially contain CO1UHC. It is well known.

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
It is normal to reach a high temperature of 1,300°C, and there is a tendency to raise the temperature even higher to improve the efficiency of gas turbines.

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

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 The remaining unburned fuel is secondaryly combusted behind the layer, or if necessary, secondary fuel is introduced and the remaining unburned fuel and newly added secondary fuel are combusted secondarily to achieve the desired purpose. A combustion method has been discovered that produces clean combustion gases at or above temperatures.

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. Once the gas temperature reaches More fuel is preferable.

The entire amount of fuel capable of changing the desired temperature may be introduced into the catalyst layer, a portion of the fuel may be combusted to raise the temperature, and the remaining unburnt fuel may be subjected to secondary combustion, but some of the fuel may be left behind. This may 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 setting the temperature of the catalyst layer higher than necessary, and it is possible to avoid deterioration and damage to the catalyst, which is more preferable.

The temperature required to induce secondary combustion depends on the type of fuel,
It is determined by the residual fuel concentration (theoretical adiabatic combustion gas temperature), linear velocity, etc., but 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
High temperatures of 0°C to 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.

The catalyst preferably used for this purpose is a noble metal catalyst.

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 conventional catalyst containing palladium as an active ingredient is used for the purpose of the present invention, the palladium is oxidized and impairs the methane ignition performance because it is exposed to a high concentration of oxygen trap at a temperature of 500°C or less near the inlet of the catalyst layer. On the other hand, the combustion reaction by the catalyst is suppressed and the combustion gas temperature does not rise to a high temperature of 750℃ or higher, due to the high temperature near the outlet of the catalyst layer, which is thought to be due to a change in the oxidation state of palladium. I found out that there is a drawback.

On the other hand, catalysts containing platinum as an active component have a high methane ignition temperature of over 500°C, but methane can be ignited at 1
It is possible to achieve 00% complete combustion, and as a result,
There was a drawback that the catalyst layer was heated to a high temperature exceeding 1000° C., and the platinum turned into an oxide and sublimated, resulting in deactivation.

The present inventors have focused on the excellent features of these noble metal catalysts, 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 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 raise the combustion gas temperature to 750 to 1000 degrees Celsius used in the second layer. The catalyst used in the first stage ff1K consists of palladium and platinum as active components, and the catalyst used in the second stage consists of platinum as an active component, and
It is constructed in such a way that it does not reach a high temperature of 1000°C or higher.

According to the present invention, the presence of a small amount of platinum in the front-stage catalyst near the catalyst system entrance prevents deterioration of methane ignition performance due to palladium oxidation, maintains low-temperature ignition performance for a long time, and reduces combustion gas Temperature 700-8
It was discovered that the combustion gas can be raised to a temperature of 750 to 1000 degrees Celsius, and the presence of platinum in the downstream catalyst near the outlet of the catalyst layer further promotes combustion. be.

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

The catalysts for the front layer and the rear layer may be prepared separately and both catalysts 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 and the rear layer catalyst may be placed at the outlet portion. A finished catalyst may be obtained by supporting a bed catalyst.

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, α-alumina, zirconia, titania, titanium phosphate, aluminum, tikunate, 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 Cancle 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. ~400 cells are used.

The total catalyst bed length depends, among other things, on the inlet linear velocity used;
Generally, 50 to 500μ is adopted because of the need to reduce pressure loss, and the length of each layer 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 250μ is used for each layer. Adopted.

The catalyst used in the first layer is usually the monolithic carrier coated with an active refractory metal oxide such as alumina, silica-alumina, magnesia, titania, zirconia, or silica-magnesia. In particular, zirconia is preferable for alumina, and it is even more preferable to add a total alkaline earth oxide such as barium or strontium, or a rare earth gold oxide such as lanthanum, neodymium, cerium, or praseodymium to stabilize the material.

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 support.゛Palladium is supported at 2 to 100 F, preferably 5 to 50 F, per finished catalyst 11, and platinum is supported at a weight ratio of 02 to 50% and a Ut ratio of 0.5 to 30% relative to palladium.
It is used by adding it.

The catalyst used in the latter layer can be catalyzed by supporting platinum in the same way, but in this case, the catalyst is too active and the temperature in the catalyst layer is raised to OO0℃ or higher to catalyze platinum. This may cause deactivation due to sublimation, etc.

In order to avoid this and keep the catalyst layer temperature below 1000℃, methods include reducing the amount of platinum supported, calcining the finished catalyst at a high temperature exceeding 1000℃ before use, and coarsening platinum black etc. Methods have been discovered, such as using platinum particles that have been removed, and methods that optimally select catalyst cellization and layer length. The optimum selection can be made depending on the speed, 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. Although the composition ratio of natural gas varies slightly depending on where it is produced, it contains more than 80 grams of methane. Further, fermented methane from activated sludge treatment and low-calorie methane gas from coal gasification are also fuels used in the present invention. Naturally, easily flammable propane, light oil, etc. can also be used.

The catalyst of the present invention or the combustion system using the catalyst can be suitably incorporated into a power generation gas turbine system Kffi as described above, but it can also be used in power generation boilers, heat recovery boilers, gas engines, etc. It is used to efficiently recover heat and power through post-processing of city gas, 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
A cordierite honeycomb carrier with a length of 50y+x was coated with a slurry of alumina powder enriched with 5% by weight of lanthanum oxide, and fired at 900°C in air to coat and support the carrier with an amount of 11%. Ta.

Next, this was immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and calcined at 700°C in air to support 10% of palladium and 29% of platinum per liter of support to obtain the finished catalyst. I got it.

9 Example 2 In the same manner as in Example 1, a 5-fold r of 100F per 1 carrier was applied.
Alumina powder containing &% lanthanum oxide was pickled, dried, and calcined in air at 900°C to support 22 platinum per 11 carriers to obtain a completed catalyst.

Stream side 3 Same as Example 1, 7-fold 'rj! % of neodymium oxide was coated on the carrier 11 in an amount of 1 sor.

Next, in the same manner as in Example 1, 202 tons of shibaradium and 5 tons of platinum were supported on the carrier 11 to obtain a completed catalyst.

Example 4 Alumina powder containing lanthanum thioxide and 3% by weight neodymium oxide was used in the 7-ply 9 layer, and the alumina powder was coated on each carrier 11 in the same manner as in Example 1.

This is then converted into an aqueous solution containing dinitrodiaminoplatinum in nitric acid. ! ! By soaking, drying, and calcining in air at 1150° C., 152 was supported as platinum on carrier 11h to obtain a completed catalyst.

Example 5 25.4i diameter with 40 cells/in2 aperture
it, 10% by weight on a 15 mm long mullite honeycomb carrier.
A slurry of alumina powder containing lanthanum oxide and 20% by weight of cerium oxide was coated and fired in air at 1000°C to coat and support 802 per carrier 11.

Next, in the same manner as in Example 4, platinum 152 was supported on the carrier 11 to obtain a completed catalyst.

Example 6 A slurry of alumina powder containing 5% by weight of cerium oxide and an average particle size of 5 were placed in the same honeycomb carrier as in Example 1.
Platinum powder having μ is thoroughly mixed and coated, and dried 9
By firing at 00°C, carrier 11 adari 1009
A finished catalyst was obtained by supporting alumina containing 5% by weight of cerium oxide and 107 platinum.

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

Comparative Example 2 A finished catalyst was obtained in exactly the same manner as in Example 4 except that the catalyst was calcined at 800° C., and 159 platinum was supported on carrier 11.

Example 7 Example 1 was installed on the upstream side using a cylindrical combustor with sufficient heat insulation.
The downstream side of the obtained catalyst was filled with the catalyst obtained in Example 2, and a methane-air mixture gas containing 3 volumes [% of methane] was fed at an inlet temperature of 350° C. at a rate of 16.7 ml per hour.
The combustion efficiency and catalyst layer outlet temperature were measured by introducing Nm''.

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 67%, and the catalyst layer outlet temperature was about 820°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, carbon oxides, and nitrogen oxides was obtained. In this case, the temperature at the point 100FIII behind the catalyst layer reached about 1300°C, but the catalyst bed outlet temperature was about 8
The temperature was 30°C.

Continuously, methane equivalent to 3% by volume was injected from the upstream side of the catalyst layer, and methane equivalent to the remaining 1.1% by volume was injected from the outlet of the catalyst layer.
A similar combustion experiment was conducted by introducing the fuel from the rear.

As a result, the catalyst bed outlet temperature was about 820°C, and clean combustion gas of about 1300°C was exchanged. This performance was still maintained for 500 hours.

Example 8 In the same manner as in Example 7, using the catalyst shown in Table 1, 3
Table 1 shows the results of a combustion experiment in which methane equivalent to a capacity of 1 was introduced from upstream of the catalyst layer, and the remaining methane equivalent to 1.1 volume @ 1 was introduced from 30 K'l rearward from the outlet of the catalyst bed. Using the uninvented catalyst system, clean combustion gas of about 1300°C was exchanged even though the catalyst layer temperature rtt was maintained at 100°C or less, which did not cause a decrease in activity. The catalyst system using the catalyst of Comparative Example 1 quickly became unable to ignite, and the catalyst system using the catalyst of Comparative Example 2 on the downstream side had too high activity and the catalyst layer U1 degree became high temperature, resulting in activation. decreased rapidly, and sublimation of platinum was observed.

Claims (6)

[Claims] (1) For combustion, which is characterized by providing a catalyst layer containing palladium and platinum as active ingredients on the front stage side and a catalyst layer containing platinum as the active component on the rear stage side with respect to the flow of fuel-air mixed gas. Catalyst system. (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) Using the catalyst system according to claim <11, (2) or (3), combustion gas is heated to a temperature at which secondary combustion is induced by causing only part of the fuel to continue burning in the system. A combustion method characterized by raising the temperature. (5) In the combustion method according to claim (4), the combustion gas temperature is increased by 700°C to 800°C in the first stage catalyst layer and 750°C to 1000°C in the second stage catalyst layer. Method. (6) The method according to claims (4) and (5), characterized in that secondary combustion is caused by further supplying secondary fuel to the gas that has been heated to a temperature that induces secondary combustion.