JPH0153579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for catalytically burning methane-based 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 monoxide (hereinafter referred to as CO), and nitrogen oxides. The present invention provides a catalyst and a combustion method using the catalyst for obtaining combustion gas that does not substantially contain harmful components such as combustion hydrocarbons (hereinafter referred to as UHC) and using its calorific value as various energy sources. More specifically, the present invention involves igniting methane, which is said to be relatively flame-retardant among hydrocarbons, or a natural gas fuel containing methane as its main component at a low temperature using a catalyst at high linear velocity. The temperature is raised to a temperature sufficient to induce combustion, and then secondary fuel is introduced as necessary to combust the remaining unburned fuel and secondary fuel to reach the target temperature or higher. The present invention provides a catalyst suitable for use in the combustion methods listed above and a combustion method using the same. A catalytic combustion method is known in which a dilute gas mixture in which fuel is mixed with air at a low temperature below the combustion range is introduced into a catalyst layer and catalytically combusted on the catalyst to obtain high-temperature combustion gas. Furthermore, using such a catalytic combustion method, e.g.
It is well known that when obtaining combustion gas between 600°C and 1500°C, little or no NOx is generated even if air is used as the oxygen source, and it also contains virtually no CO or UHC. 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 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 begun to be conducted on the use of this high-temperature combustion gas as a primary power source such as gas turbines for power generation. When used for these purposes, the combustion gases are
It is normal to reach a high temperature of 1000 to 1300 degrees Celsius, 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 conventional catalyst deteriorates rapidly due to the high temperature, and in the worst case, the catalyst carrier may melt down and fly off, damaging turbine blades and the like. 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. Remaining unburned fuel is secondary combusted at the rear, or if necessary, secondary fuel is introduced and the remaining unburned fuel and newly added secondary fuel are combusted secondary to reach the desired temperature. A combustion method has been discovered that produces clean combustion gas at a temperature of , or even higher. 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 may be introduced into the catalyst layer to obtain the desired temperature, a portion of it may be combusted and rise, and the remaining unburned 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 the rear of the catalyst layer and combined with the remaining unburned fuel for secondary combustion. In this case, it is possible to avoid raising the temperature of the catalyst layer higher than necessary, thereby preventing deterioration of the catalyst and
This has the advantage of avoiding damage. The temperature required to induce secondary combustion depends on the type of fuel, the residual fuel concentration (theoretical adiabatic combustion gas temperature),
It is determined by the linear velocity, but it will vary widely depending on the type of fuel. In other words, in the case of easily flammable fuels such as propane and diesel oil, a temperature of approximately 700°C is sufficient under normal usage conditions, but when using flame-retardant methane or natural gas whose main component is methane as fuel, In this case, a high temperature of 750°C to 1000°C is required, depending on the usage conditions. 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 to ignite this flame-retardant fuel at a high linear velocity and at as low a temperature as possible. An object of the present invention is to provide a catalyst that can raise the temperature of combustion gas to 750°C or higher, particularly to a temperature of 850 to 950°C. Catalysts suitably used for the purpose of the present invention include:
Noble metal catalysts are suitable, and catalysts containing palladium as the main active component are particularly preferred. Catalysts containing palladium as an active component are particularly excellent in low-temperature ignition of methane, and also have excellent heat resistance of about 1000°C. However, when conventional catalysts containing palladium as an active ingredient are used for the purpose of the present invention, low-temperature ignition performance is not necessarily sufficient and palladium is exposed to high concentrations of oxygen at temperatures below 500°C near the entrance of the catalyst layer. The methane is oxidized and loses its ignition performance, and on the other hand, the combustion reaction by the catalyst is suppressed 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, and the combustion gas temperature is over 750℃. It was discovered that the drawback is that it does not rise to high temperatures. The present inventors have focused on the excellent characteristics of a catalyst containing palladium as the main active component, and have completed the present invention as a result of intensive research aimed at overcoming the drawbacks of conventional catalysts. That is, the catalyst according to the invention contains palladium, platinum and nickel oxide as active components, with 2 to 300 g of palladium per catalyst.
This is a monolithic catalyst for combustion of methane-based fuel, characterized in that palladium is supported with 0.2 to 50% by weight of platinum and 5 to 300 g of nickel oxide. According to the present invention, the low-temperature ignition performance of methane is improved by the addition of nickel oxide, and the presence of platinum prevents the deterioration of methane ignition performance due to palladium oxidation, maintaining low-temperature ignition performance for a long time. The following catalyst can be provided.
In addition, since nickel exists as an oxide, oxygen is stably supplied to palladium.
Combustion is further promoted and combustion gas easily reaches temperatures above 750℃.
In particular, they found that it is possible to reach temperatures of 850-950°C. Performance similar to that of the present invention can also be achieved by the combustion catalyst system disclosed in Japanese Patent Application No. 59-51186 (Japanese Unexamined Patent Publication No. 60-196511) filed by the same applicant. By adding , the low-temperature ignitability is further improved, and the same or higher performance is achieved with one type of catalyst, so there is an advantage that the catalyst layer length can be shortened and pressure loss can be reduced. The shape of the catalyst is preferably a monolith type for the purpose of reducing pressure loss. Any monolithic support commonly used in the field can be used, in particular cordierite, mullite, alpha alumina, zirconia, titania, titanium phosphate, aluminum titanate, betalite, spodiumen, aluminosilicate, silica. Heat-resistant ceramic materials such as magnesium oxide, zirconia-spinel, zircon-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 the catalyst layer may have the same cell size or a combination of different cell sizes, usually 40 to 400 cells per square inch. A cell type is used. The length of the catalyst layer varies depending on the inlet linear velocity used, but it is usually 50 to 50 mm due to the need to reduce pressure loss.
500mm is adopted. The catalyst is usually used by coating the above-mentioned monolithic support with an active refractory metal oxide such as alumina, silica-alumina, magnesia, titania, zirconia, or silica-magnesia. Alumina, titania or zirconia are particularly preferred, and oxides of alkaline earth metals such as magnesium, calcium, strontium and barium, or oxides of rare earth metals such as lanthanum, yttrium, cerium, samarium, neodymium and praseodymium are preferred.
It is more preferable to add a species or two or more species for stabilization. Thereafter, the active components palladium, platinum and nickel oxide in the form of water-soluble salts are impregnated and catalyzed. Alternatively, it is possible to catalyze the active ingredient by first supporting it on an active refractory metal oxide and then coating it on a monolithic carrier. The hydroxides can also be catalyzed by mixing them with active refractory metal oxides and coating them on a monolithic support. Palladium is 2-300g per finished catalyst,
Preferably, 10 to 150 g of platinum is used as a carrier, and platinum is added in a weight ratio of 0.2 to 50%, preferably 0.5 to 30%, based on palladium. In addition, the amount of nickel oxide supported is 5 to 300 per finished catalyst.
g, preferably 10 to 200 g. The fuel used in the combustion method 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 approximately 80% or more methane, although the composition ratio varies slightly depending on the region of production. Furthermore, fermented methane from activated sludge treatment and low-calorie 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 method using the catalyst can be optimally incorporated into a gas turbine system for power generation as described above, but it is also applicable to boilers for power generation, gas turbines and boilers for heat recovery, and gas engines. The gas from the area is also used for efficient heat and power recovery through post-processing and gas heating in districts and cities. 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 Diameter with 200 cells/in2 aperture
A cordierite honeycomb carrier measuring 25.4 mm and 50 mm in length was coated with an aqueous slurry of alumina powder containing 5% by weight of lanthanum oxide and heated at 900°C in air.
The mixture was combusted to coat and support 100 g per carrier. Then immersed in an aqueous solution containing nickel nitrate,
Dry and combust in air at 700℃, per carrier
30g of nickel oxide was supported. This was then immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried and heated in air at 700 °C.
20% palladium per carrier
g and 4 g of platinum were supported to obtain a completed catalyst. Example 2 A carrier similar to that used in Example 1 except that the length was 30 mm was coated with a slurry of alumina powder containing 5% by weight of lanthanum oxide, and the carrier was exposed to air.
The mixture was burned at 800°C to coat and support 150g of lanthanum oxide-containing alumina per carrier. Next, in the same manner as in Example 1, catalytically active substances containing 50 g of nickel oxide, 50 g of palladium, and 5 g of platinum were supported on each carrier to obtain a completed catalyst. Example 3 A honeycomb carrier made of the same material and specifications as those used in Example 1 was coated with an alumina powder slurry containing 70% by weight lanthanum oxide and 3% by weight neodymium oxide, and then burned in air at 1000°C. A coating of 120 g was carried on each carrier. Next, this was immersed in an aqueous solution containing palladium nitrate, dinitrodiaminoplatinum, and nickel nitrate, dried, and burned in air at 800°C.
A completed catalyst was obtained by supporting a catalytically active material containing 25 g of palladium, 5 g of platinum, and 40 g of nickel oxide per carrier. Example 4 A honeycomb carrier similar to that used in Example 1 was coated with 5
Coated with a slurry of alumina powder and nickel oxide powder containing lanthanum oxide in weight percent, and exposed to air.
Burned at 900℃, 5% by weight of 150g per carrier
Alumina powder containing lanthanum acid and 50 g of nickel oxide were coated and supported. Next, this was immersed in an aqueous solution containing palladium nitrate and dinitrodiaminoplatinum, dried,
By burning in air at 700°C, 20 g of palladium and 4 g of platinum were supported per carrier to obtain a completed catalyst. Example 5 Diameter with 100 cells/in2 aperture
3 on a mullite honeycomb carrier with a length of 25.4 mm and a length of 50 mm.
A slurry of zirconia powder and nickel oxide powder containing yttrium oxide in a weight percent is coated,
Calcined at 1000℃ in air, 200g of zirconia containing 3% by weight of yttrium oxide and 50g of zirconia per carrier.
It was coated with nickel oxide. This was then immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried and heated in air at 700 °C.
Calculated at °C, per 1 carrier, as palladium
A completed catalyst was obtained by supporting 20g of platinum and 2g of platinum. Example 6 Diameter with 100 cells/in2 aperture
A 25.4 mm x 50 mm long aluminum titanate honeycomb carrier was coated with a slurry of a mixture of alumina powder, titania powder, and nickel hydroxide powder containing 5% by weight of lanthanum oxide, and calcined in air at 900°C to obtain 75 g per carrier. Alumina containing 5% by weight of lanthanum oxide, 75 g of titania and 40 g of nickel oxide were coated and supported. Next, this was immersed in an aqueous solution of palladium nitrate and dinitrodiaminoplatinum in air, dried, and calcined in air at 700°C to obtain palladium per carrier.
A completed catalyst was obtained by supporting 20g of platinum and 4g of platinum. Comparative Example 1 A finished catalyst was obtained in the same manner as in Example 1 except that it did not contain nickel. Comparative Example 2 A finished catalyst was obtained in the same manner as in Example 1 except that it did not contain platinum. Example 7 Example 1 using a cylindrical combustor with sufficient heat insulation
The obtained catalyst was filled, and a methane-air mixture gas containing 3% by volume of methane was introduced at an inlet temperature of 350° C. at 16.7 Nm ³ per hour, and 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 approximately 79%, and the catalyst layer outlet temperature was approximately 900°C. Next, when the methane concentration was increased to 4.1% by volume, the combustion efficiency was 100%, and a clean combustion gas containing virtually no unburned hydrocarbons, hydrogen monoxide, or nitrogen oxides was obtained. In this case, the rear of the catalyst layer
The temperature at the 100 mm point reached approximately 1300°C, but the catalyst layer outlet temperature was approximately 91°C. Subsequently, a similar combustion experiment was conducted by introducing methane equivalent to 3% by volume from upstream of the catalyst bed and the remaining methane equivalent to 1.1% by volume from 30 mm behind the outlet of the catalyst bed. As a result, the catalyst bed outlet temperature was approximately 900℃,
Clean combustion gas of approximately 1300℃ was obtained. Moreover, this performance was maintained for 1000 hours. Example 8 Each of the catalysts of Examples 1 to 6 and Comparative Examples 1 to 2 was packed into a cylindrical combustor, and a methane-air mixture containing 3% by volume of methane was introduced at 5.57 Nm ³ per hour. Combustion efficiency was measured while gradually increasing the temperature. Next, the inlet temperature was set to 350°C, and combustion was continued for 48 hours while measuring the combustion efficiency and combustion layer outlet temperature. In this case, the average linear velocity at the entrance of the catalyst layer is 10
m/sec. As a result, the performance of each catalyst is as shown in Table 1.The catalyst of the present invention has a short catalyst layer length, ignites methane at a low preheating temperature, and heats the combustion gas to 750℃.
As described above, it has been found that the temperature can be raised to 850 to 950°C and the performance can be maintained for a long time. 【table】

Claims (1)

[Claims] 1 Contains palladium, platinum, and nickel oxide as active ingredients, with palladium in the range of 2 to 300 g per catalyst, platinum in an amount of 0.2 to 50% by weight relative to the palladium, and nickel oxide. 5
A monolithic catalyst for combustion of methane-based fuel, characterized in that it is supported in a range of ~300g. 2. A patent claim characterized in that the active ingredient is dispersed and supported on a monolithic carrier coated with at least one active refractory metal oxide selected from the group consisting of alumina, titania, and zirconia. Catalyst according to scope 1. 3. The active refractory metal oxide is stabilized by at least one oxide selected from the group consisting of lanthanum, yttrium, cerium, samarium, neodymium, praseodymium, magnesium, calcium, strontium, and barium. The catalyst according to claim 2, characterized in that: 4 Contains palladium, platinum and nickel oxide as active ingredients, with palladium in the range of 2 to 300 g per catalyst, platinum in the range of 0.2 to 50% by weight and nickel oxide in the range of 5 to 50 g per catalyst.
Using a monolithic catalyst for combustion of methane-based fuel supported in the range of ~300g, only part of the fuel is combusted in the catalyst layer, and the temperature of the combustion gas is raised to a temperature that induces secondary combustion. A method of burning methane-based fuel characterized by the following. 5. The combustion method according to claim 4, characterized in that secondary combustion is caused by further supplying secondary fuel to the gas heated to a temperature that induces secondary combustion.