JPS62149346A - Catalyst for combustion - Google Patents

Abstract

PURPOSE:To permit the perfect combustion of a combustible gas by depositing a refractory metallic oxide and catalyst component on a carrier and making the sectional area of the catalysts successively smaller from a gas inlet side toward outlet side with respect to the flow of the fuel-contg. gas. CONSTITUTION:The refractory metallic oxide and catalytically active component are deposited on the monolith type catalyst carrier formed to have the sectional area of the catalyst successively smaller from the gas inlet side toward the outlet side with respect to the flow of the fuel-contg. gas to produce the catalyst for combustion. The catalyst carrier consisting of cordierite, mullite, alpha-alumina, etc., is adequate and the ratio between the sectional area (a) in the gas inlet of the catalyst carrier and the sectional area (b) in the outlet is adequately specified to a 1/4<b/a<1 range. Noble metals such as Pt and Pd alone or the alloys thereof are adequate for the catalytically active component and alumina, silica-alumina, magnesia, etc., are adequate for the refractory metallic oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention provides a method for contacting flammable gases such as -carbon oxide (CO), hydrogen (Hz), and methane-containing gases over a catalyst. By combustion, we obtain combustion gas that does not substantially contain harmful components such as nitrogen oxides (NOx), -carbon oxides (CO), and unburned hydrocarbons (Ul-IC), and use its calorific value as a source of various primary energy sources. This invention relates to the combustion catalyst 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 produce high-temperature combustion gas. .

Furthermore, using such a catalytic combustion system, e.g.
It is well known that when obtaining combustion gas between 00°C and 1500°C, little or no NOx is generated even if air is used as the oxygen source, and it can be obtained without substantially containing C01U1)C. This is where you will be exposed.

Various systems have been proposed that utilize this clean, high-temperature combustion gas to generate heat or power, and systems for general industrial exhaust gas treatment and thermal power recovery systems have already utilized this high-temperature combustion gas for primary power sources such as gas turbines for power generation. Research is beginning to be conducted on its use.

These catalytic combustion systems contain refractory metal oxides such as alumina and zirconia, and catalytically active components PL and P.
Oxides of noble metals such as d, 1 to 11, base metals such as cobalt and nickel, and composite oxides such as LaCo0J are used in a monolith type 4U'! A catalyst body supported on a body is used.

Problems to be Solved by the Present Invention> In a system using the catalyst system as described above and used as a primary power source such as a gas turbine, the conditions for using the catalyst are under high pressure of 10 to 20 atmospheres due to the characteristics of the turbine. On the other hand, in order to reduce pressure loss and keep the combustor to a small capacity, the catalyst capacity is required to be as small as possible.As a result, the linear method is 10 to 1100 (7 seconds), and the space velocity is 800,000 to 6,000,000 hours (hr""'), which is extremely harsh conditions.

Under such high pressure conditions, with flammable gases, especially meth, it is essential to increase the active components such as precious metals and the catalyst capacity, and a practically completed system has not yet been obtained.

Therefore, an object of the present invention is to catalytically burn combustible gases such as methane with a smaller catalyst capacity even under the conditions applicable to high-pressure gas turbines as described above.
It is an object of the present invention to provide a vine combustion catalyst that achieves complete combustion substantially free of harmful components such as Ox and UllC.

Means for Solving Problems〉 In order to achieve the above object, the present inventors used methane, which is the most flame-retardant among combustible gases, and conducted experiments under various conditions ranging from normal pressure to high pressure. A thorough study of catalytic combustion revealed that the combustion reaction, or oxidation reaction, of methane mainly depends on a heterogeneous reaction on the catalyst surface at the gas inlet side, that is, at the low-temperature region catalyst in the front stage, while at the gas outlet In the high temperature region of the side, that is, the rear stage, it mainly depends on a homogeneous reaction in the gas phase, and as the gas density and gas flow rate increase due to pressurization at the same linear velocity, the catalyst surface in the front stage The heterogeneous reaction above shifts from rate-limiting diffusion due to mass transfer of fuel gas to rate-limiting reaction on the catalyst surface, leading to a decrease in combustion efficiency.On the other hand, in the gas phase in the latter stage, The present inventors have discovered that the uniform combustion reaction of , which leads to an improvement in combustion efficiency, has led to the completion of the present invention.

That is, the combustion catalyst of the present invention, as shown in FIGS. 1 and 2, for example, allows the fuel-air mixture to flow from the inlet side to the outlet 1F! The catalyst is characterized in that the cross-sectional area of the catalyst is gradually reduced over the +1 stage, and as a result, the space velocity is lowered in the front stage, where activity decreases under pressure, and the surface area of the active material, such as noble metal, is increased, thereby improving combustion efficiency. At the same time, in the latter stage, which improves combustion efficiency under pressure, by reducing the catalyst capacity and the amount of active material retained, a small-capacity combustion catalyst suitable for the combustor shape can be used to withstand high-pressure conditions. They discovered that it is possible to achieve complete combustion even when

Furthermore, the combustion catalyst in the present invention will be specifically explained.

The combustion catalyst of the present invention has a catalyst cross-sectional area that is gradually decreased from the inlet side to the outlet side.

Specifically, the catalyst body may be prepared separately in several stages from the first stage to the second stage, and each catalyst may be directly connected or installed with a space provided, or it may be prepared as a complete catalyst as an integrated catalyst body. Good too.

As the catalyst carrier, a monolith type carrier is preferable for the purpose of reducing pressure loss. Any monolithic support commonly used in the field can be used, especially cordierite, mullite, α-alumina,
Heat-resistant ceramic materials such as zirconia, titania, titanium phosphate, aluminum titanate, zetalite, spodumene, aluminosilicate, macanenium silicate, silconium arsenal, zircon-mullite, silicon carbide, silicon nitride, Kanthal, feclaroy, etc. metal ones are used.

The cell size of one monolithic carrier is preferably large as long as the combustion efficiency does not decrease, and each catalyst layer may have the same cell size or may use a combination of cell sizes that are quite different. Normal - 1O-l10 per flat inch
A cell with 0 cells is used.

The total catalyst bed length varies depending on the inlet linear velocity used, but
Normally 50 to 300 mm due to the need to reduce pressure loss
is adopted, and the length of each layer also depends on the pressure, fuel concentration, inlet linear velocity,
F is optimally selected depending on usage conditions such as inlet temperature, but usually 10 to 200 F is adopted for each layer.

The following are the effects of pressure drop, combustor shape and usage.
It is preferable that it is in the range of 1.

As catalyst active components, platinum (Pt), palladium (P
(,1), noble metals such as rhodium (Rh) alone or alloys have the best performance, but others such as nickel (Ni),
Cobalt (Co), rim (Cr), iron (Ii'e),
Metal oxides such as tin (Sn), L; IC0OJ, Cu
Cr0. , Mnl? , , O, etc. also have the effect as an active ingredient by using them as fils with noble metals.

These active ingredients and a refractory metal oxide such as alumina, liquor alumina, red sea bream/sea, titania, zirconia, silica-magnenoir, etc. are supported on the monolithic carrier and catalyzed.

``Refractory metal oxides include alkaline earth metal oxides such as barium and strontium, lanota, neodymium,
It is more preferable to add and stabilize rare earth metal oxides such as cerium and praseodymium.

The catalyst component may be supported by coating the refractory metal oxide and then impregnating the active component in the form of a water-soluble salt, or by supporting or mixing the active component with the refractory metal oxide in advance. Then, it may be supported on a monolithic carrier.

The present invention becomes even more effective by optimally selecting and combining these catalyst components from the inlet side to the outlet side depending on the conditions of use.

The amount of catalyst components supported is as follows for precious metals, which are essential components.
02 to 15% by weight, preferably 05 to 8% by weight based on the total catalyst body, and 2.0 to 35.0% by weight based on the total catalyst body for other world metal oxides and composite oxides, depending on the usage conditions. Optimally supported depending on the situation.

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 the region of production, it contains more than 80% of methane.

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 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 can be advantageously incorporated into the 7-Stem system, which efficiently recovers heat and power through post-processing and city gas heating.

<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 30 m diameter with 250 cells/in2 aperture
7 m on a cordierite honeycomb carrier with a length of 20 m
By coating alumina powder containing 7i'% lanthanum oxide and 3% neodymium oxide, drying and then calcining in air at 600°C, 16% lanthanum oxide and neodymium oxide alumina powder can be obtained per finished catalyst. % coverage was carried out.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and then calcined in air at 600°C, so that 35 parts by weight of palladium and 06 parts by weight of platinum were supported per finished catalyst. A finished catalyst was obtained.

Example 2 25 mm diameter with 250 cells/inch aperture
A cordierite honeycomb carrier having a length of 25 mm was coated with a mixed slurry of alumina powder containing 10% by weight of 1 cum of oxidized cells and nickel oxide powder in the same manner as in Example 1, so that each finished catalyst contained cerium oxide. As alumina powder, 166% by weight as nickel oxide.
It was supported at 1% by weight.

Next, this carrier was immersed in an aqueous solution containing palladium nitrate and dinitrodiaminoplatinum, dried, and then calcined in air at 700°C to support 3% by weight of palladium and 0.5% by weight of platinum per finished catalyst. A finished catalyst was obtained.

Example 3 20 mr diameter with 200 cells/in2 aperture
n. A mullite honeycomb carrier with a length of 30 mm is coated with a slurry of zirconia powder and a platinum black powder having an average particle size of 0.5 microns, and after drying, it is fired at 900°C in the air. A finished catalyst was obtained by loading 255% by weight of zirconia powder and 2.0% by weight of platinum per finished catalyst.

Example 4 18 mm diameter with 200 cells/in2 aperture
A mullite honeycomb carrier with a length of 20 mm was coated with a mixed slurry of zirconia powder containing 5 parts by weight of yttrium oxide and chromium oxide powder, dried, and then calcined in air at 1000°C to produce a finished catalyst. 155% by weight as zirconia containing yttrium oxide 1 as chromium oxide
A completed catalyst was obtained by carrying 0% by weight.

Comparative Example 1 23.5 mm diameter with 250 cells/in2 apertures.
Cordierite with a length of 4 mm and a length of 3'3 mm.
A finished catalyst was obtained in exactly the same manner as in Example 1, except that a nicum carrier was used.

Comparative Example 2 23.5 mm diameter with 250 cells/in2 apertures.
A finished catalyst was obtained in exactly the same manner as in Example 2, except that a cordierite honeycomb carrier having a diameter of 4 mm and a length of 28 plates was used.

Comparative Example 3 2 diameter with 200 cells/inch square aperture:
Mullite honeycomb 4 with a length of 3.4 mm and a length of 22 mm
A completed catalyst was obtained in exactly the same manner as in Example 3, except that 11 catalysts were used.

Comparative Example 1 200 cells/V with a diameter of 23
A finished catalyst was obtained in exactly the same manner as in Example 4, except that a mullite honeycomb carrier having a length of 1 mm and a length of 12+ nm was used.

Example 5 Using a sufficiently insulated combustor with pipe diameters gradually decreasing from the inlet to the outlet, the catalyst obtained in Example 1 was placed in the first stage from the inlet side, and the catalyst obtained in Example 2 was placed in the second stage. The catalyst that was
The catalyst obtained in Example 3 was used in the third stage, and the catalyst obtained in Example 3 was used in the fourth stage.
The catalysts obtained in step 1 were packed at intervals of 10 mm, and the inlet temperature was 3. (51 volume-t at 50"C).
1i% (li')) Tough The Mekno-air mixture gas containing the entire mixture was 20 per 1112 minutes under a pressure of 10 atmospheres.
0 Nm3 (ST l)) The introduction combustion efficiency and the outlet temperature of each stage catalyst layer were measured. In this case, the catalyst capacity is approximately 41i
Met.

The results are shown in Table 1.

Comparative Example 5 Using a sufficiently warmed cylindrical combustor, the catalyst obtained in Comparative Example 1 was placed in the first stage from the inlet side, the catalyst obtained in Comparative Example 2 was placed in the second stage, and the catalyst obtained in Comparative Example 2 was placed in the third stage from the inlet side. The combustion obtained in Comparative Example 3 was
The catalyst obtained in Comparative Example 4 was filled in each stage with an interval of 10 mm, and at an inlet temperature of 350°C,
A methane-air mixture containing methane by volume is 1O
200 Nm'(STI') per hour under negative pressure
) The combustion efficiency and the outlet temperature of each stage catalyst layer were measured.

In this case, the catalyst inlet linear velocity was about 30 m/sec, and the capacity of each stage catalyst and the total catalyst layer length used in Example 5 were as follows.
It was almost the same as in the case of .

The results are shown in Table 1.

Example 6 30 mm diameter with 200 cells/in2 aperture
, 30mm long cordierite/・Nicum J'I'i
The body is coated with a mixed slurry of lanthanum oxide-containing alumina powder and nickel oxide powder, dried, and then calcined in air at 700"C. Nickel was supported on a 15-weight plate.

The carrier was then immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried and then heated at 900'C in air.
By firing the catalyst, a finished catalyst was obtained in which 25 parts by weight of palladium and 0.5 parts by weight of platinum were carried per finished catalyst.

Example 7 A 22.5 mm diameter cell with 200 cells/in2 apertures.
A completed catalyst was obtained in exactly the same manner as in Example 1, except that a cordierite honeycomb carrier of 5 mm and 30 mm in length was used.

Example 8 15 m diameter with 200 cells/V inch opening
The completed catalyst was prepared in exactly the same manner as in Example 1 except that a cordierite honeycomb carrier having a length of 30 mm and a length of 30 mm was used.
It's T.

Ratio I bite case 6 Diameter is 23. A finished catalyst was obtained in exactly the same manner as in Example 1, except that a cordierite-nicum carrier having a length of 3 mm and a length of 30 mm was used.

Example 9 Using a combustor whose tube diameter was kept sufficiently warm and gradually reduced from the inlet to the outlet, the catalyst obtained in Example 6 was placed in the first stage from the inlet side, and the catalyst obtained in Example 7 was placed in the second stage. The catalyst
The catalyst selected in Example 8 was placed in the third stage at IOmr.
A methane-air mixture gas containing 3.01 volumes of methane was charged at intervals of n at an inlet temperature of 350°C, and was heated to 107Ni (STP) per hour under a pressure of 8 atmospheres.
The combustion efficiency and outlet temperature of each stage catalyst layer were measured. In this case the catalyst capacity was approximately 38.4C1)L.

The results are shown in Table 2.

Comparative Example 7 Using a sufficiently warmed cylindrical combustor, three catalysts exactly the same as those in Comparative Example 6 were filled at 10 mm intervals, and at an inlet temperature of 350°C: Contains 3.0 volume of methane. A methane-air mixture gas was introduced under a pressure of 8 atmospheres at a rate of 107 Nmj (STP) per hour, and the combustion efficiency and temperature of each stage catalyst layer were measured. In this case, the catalyst capacity was 381 d, which is almost the same as in Example 9, and the linear velocity at the entrance of the shredded catalyst layer was about 20 m/sec.

The results are shown in Table 2.

Table 1 Table 2 <Effects of the invention> As is clear from the above examples, by sequentially decreasing the catalyst cross-sectional area from the inlet to the outlet of the catalyst layer, the catalyst can be used under conditions of high pressure and high space velocity with a smaller catalyst capacity. , CO,
It becomes possible to achieve complete combustion by catalytic combustion that does not substantially contain NOx and UHC, and it becomes possible to apply catalytic combustion to combustion parts such as gas turbines.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show an example of the catalyst of the present invention.

Claims (3)

[Claims] (1) In a monolithic combustible gas combustion catalyst that supports a refractory metal oxide and a catalytically active component, the cross-sectional area of the catalyst is made gradually smaller from the gas inlet side to the outlet side with respect to the flow of fuel-containing gas. Characteristic combustion catalyst. (2) The combustion catalyst according to claim (1), wherein the catalyst is a combustion catalyst for a gas turbine. (3) The combustion catalyst according to claim (1) or (2), characterized in that a methane-containing twist material is used as the fuel.