JP2000282845A - Gas engine power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve waste heat recovering ratio and an efficiency by disposing a catalyst for carrying palladium on zirconium oxide in exhaust gas smoke. SOLUTION: An oxidation catalyst to be used is catalyst formed by carrying palladium on ziroconiun oxide, or it is a catalyst formed by carrying palladium and platinum on zirconium oxide. The oxidation catalyst is disposed in exhaust gas smoke. For example, when a gas engine power generator with a turbocharger, the oxidation catalyst is disposed in exhaust gas smoke formed downstream from the turboncharger. Or in the case of a gas engine power generator having waste heat recovering boiler, a waste heat recovering boiler is a disposed in exhaust gas smoke formed downstream side from the oxidation catalyst. Even if the main component of hydrocarbon in exhaust gas is lower class saturated hydrocarbon such as methane, the waste heat recovering ratio is improved, and an efficiency of an engine system is also improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a gas engine power generator.

[0002]

2. Description of the Related Art In engine power generation equipment, waste heat is recovered from combustion exhaust gas, and the waste heat is used in a boiler or the like. At that time, a method of further increasing the amount of heat recovery by burning hydrocarbon components in the exhaust gas has been used. As a method of burning hydrocarbons in exhaust gas, there is an exhaust gas reburning method in which a burner is inserted in the exhaust gas flue and new fuel is added to burn it, but it is used when combustion conditions are poor such as when the oxygen concentration is low. Can not do.

Under such low oxygen concentration conditions, a method of oxidatively decomposing hydrocarbons using an oxidation catalyst is useful. As a catalyst for oxidizing and removing hydrocarbons other than methane, a catalyst supporting a platinum group element such as platinum and palladium is known. For example, JP-A-51-106691 discloses an exhaust gas purifying catalyst in which platinum or palladium is supported on an alumina carrier. However, when the main component of the hydrocarbon is a lower saturated hydrocarbon such as methane as in the case of natural gas combustion exhaust gas, this catalyst cannot exhibit sufficient catalytic activity. Methane is difficult to oxidize and remove because it has the highest chemical stability among hydrocarbons, but if it can be oxidized and removed, the waste heat recovery rate can be improved. Also, when waste heat recovery is not performed,
From the viewpoint of future global environmental conservation, it is desirable to reduce methane emissions as much as possible.

[0004] Since the combustion exhaust gas necessarily contains sulfur oxides, which are a factor for reducing the catalytic activity, and steam, which is a reaction inhibiting substance, the catalytic activity is reduced within a short time. Petroleum fuels such as kerosene and light oil contain sulfur compounds. Further, even natural gas-derived fuels which essentially contain no sulfur compounds, for example, city gas supplied in Japan, also contain a sulfur compound as an odorant.

For example, Lampert et al. Found that when methane oxidation was carried out using a palladium catalyst, only 0.1 ppm of sulfur dioxide was present, and the catalytic activity was almost lost within a few hours. Which shows that the presence of sulfur oxides has a significant adverse effect on catalytic activity (Applied Catalysis B: Environmental,
vol.14, pp211-223 (1997)).

Japanese Patent Application Laid-Open No. 8-332392 discloses an oxidation catalyst for low-concentration hydrocarbons in an oxygen-excess exhaust gas.
7 g / l palladium on honeycomb substrate via alumina carrier
The above discloses a catalyst supporting 3 to 20 g / l of platinum.
However, also in the case of this catalyst, in the presence of a sulfur compound, the catalytic activity deteriorates with time, and sufficient durability cannot be obtained.

As described above, a catalyst which exhibits high methane oxidizing ability even with a hydrocarbon-containing exhaust gas mainly composed of a lower saturated hydrocarbon such as methane and has sufficient durability even in the coexistence of sulfur oxide and steam. There is an urgent need to establish an efficient engine system with a high waste heat recovery rate through development.

[0008]

An object of the present invention is to provide a gas engine power generation device having a high waste heat recovery rate and a high efficiency even if the main component of the hydrocarbon in the combustion exhaust gas is a lower saturated hydrocarbon such as methane. The purpose is to provide.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above objects can be achieved by using a specific catalyst, and have completed the present invention.

That is, the present invention relates to the following gas engine power generator. 1. In a gas engine power generator,
A gas engine power generator, comprising a catalyst in which palladium is supported on zirconium oxide. 2. In a gas engine power generator,
A gas engine power generator comprising a catalyst in which palladium and platinum are supported on zirconium oxide. 3. A gas engine power generator with a turbocharger, wherein a catalyst comprising palladium on zirconium oxide is installed downstream of the turbocharger. 4. A gas engine power generator with a turbocharger, wherein a catalyst comprising palladium and platinum supported on zirconium oxide is installed downstream of the turbocharger. 5. Item 5. The gas engine power generator according to any one of Items 1 to 4, wherein a waste heat recovery boiler is installed to recover heat. 6. Item 6. The gas engine power generator according to any one of Items 1 to 5, wherein the gas engine is a lean gas engine.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In a gas engine power generator according to the present invention, an oxidation catalyst for oxidizing and removing hydrocarbons such as methane is provided in an exhaust gas flue.

The oxidation catalyst used in the present invention is a catalyst comprising palladium supported on zirconium oxide (zirconia).
(Hereinafter sometimes referred to as `` Pd / ZrO ₂ ''), or a catalyst comprising palladium and platinum supported on zirconia (hereinafter, referred to as
"Pd-Pt / ZrO ₂ "). In the gas engine power generation device according to the present invention, an oxidation catalyst is provided in the exhaust gas flue, and the exhaust gas is brought into contact with the exhaust gas flue to oxidize and remove the remaining hydrocarbons and collect the heat of the oxidation reaction.

The shape of the zirconia to be used as the carrier is not limited as long as the desired effect can be obtained. For example, commercially available zirconia for a catalyst carrier or calcined commercially available zirconia can be used. . Alternatively, zirconia that has been subjected to a treatment for increasing the acidity in advance can also be used. A treatment method for increasing the acidity of zirconia is known, and examples thereof include a method of preliminarily supporting a sulfate group (SO ₄ ²⁻ ), tungsten, and the like.

The amount of palladium carried on the oxidation catalyst is
Usually about 1 to 25% by weight of zirconia, preferably 2%
About 20%. When the supported amount of palladium is too small, the catalytic activity is not sufficiently exhibited, whereas when it is too large, the particle size of palladium becomes large and is not effectively used. When using palladium and platinum together, platinum is usually about 5 to 100% based on the weight of palladium,
Preferably, about 10 to 50% is used. If the relative use amount of platinum is too small, the effect of the combined use of both metals is not sufficiently exhibited, whereas if it is too large, the function of palladium as an active metal may be inhibited rather.

The oxidation catalyst used in the present invention is obtained, for example, by immersing a zirconia support in a metal ion solution and then drying it.
It can be obtained by firing in an oxidizing atmosphere such as in air. As the metal ion solution, a solution in which a palladium compound and, if necessary, a platinum compound are dissolved in a solvent can be used. The palladium compound and the platinum compound are not particularly limited as long as they can generate palladium ions or platinum ions when dissolved in a solvent such as water. For example, metal salts such as nitrates, sulfates, and carboxylate salts of palladium or platinum; complexes such as ammine complexes and halogen complexes; halides;
Of these, nitrates and ammine complexes are preferred. The solvent is preferably water, but may be a mixed solvent containing at least one water-soluble organic solvent such as acetone or ethanol. The firing temperature is not particularly limited, but is usually 450
About 700 ° C., preferably 500-650 ° C. If the calcination temperature is too high, while the supported palladium or palladium / platinum grain growth may proceed,
When it is too low, palladium or palladium / platinum does not reach a state of exhibiting a sufficient activity, and stable catalyst activity cannot be obtained.

The oxidation catalyst used in the present invention may be added to a binder, if necessary, and formed into pellets, honeycombs, or the like, or may be wash-coated on a refractory honeycomb substrate. Can be. When wash-coating on a refractory honeycomb substrate, wash-coat the slurry containing the catalyst prepared by the above-described method, or wash-coat zirconia on the refractory honeycomb substrate in advance, and then apply the method described above. , Palladium or palladium / platinum.

The amount of the oxidation catalyst to be used may be set to an appropriate space velocity according to the type of the catalyst, the amount of methane in the exhaust gas, and the like. For example, when using a Pd / ZrO ₂ is a velocity space gas per time (GHSV), used under the conditions to be usually about 500000 h ^-1 or less, more preferably 1,000-300000 h
Use under the condition of ^-1 or less. When Pd-Pt / ZrO ₂ is used, the GHSV is used under the condition that it is usually about 500,000 h ⁻¹ or less, more preferably 1000 to 300,000 h ⁻¹ or less. As for the oxidation catalyst, the larger the amount of the catalyst, the lower the gas hourly space velocity (GHSV) and the higher the methane oxidation rate, but the economic efficiency is impaired and the pressure loss in the catalyst layer increases. May occur. On the other hand, if the amount of the catalyst is too small, an effective methane oxidation rate cannot be obtained.

The operating temperature of the catalyst is not particularly limited, and may be appropriately set according to the type of the catalyst, the amount of methane in the exhaust gas, and the like. If the operating temperature is too high, the durability of the oxidation catalyst may decrease. On the other hand, if the operating temperature is too low, the activity of the oxidation catalyst may decrease, and a desired conversion may not be obtained. For example, when using Pd / ZrO ₂ , the catalyst layer temperature is usually about 350 to 650 ° C.,
Preferably it is about 400 to 600 ° C. In the case of using a Pd-Pt / ZrO _2, the catalyst layer temperature is usually 350 to 650 ° C., preferably about 400 to 600 ° C..

The gas engine power generator to which the present invention is applied is not particularly limited, and can be applied to any conventional gas engine power generator. For example, a gas engine power generation device with a turbocharger, a gas engine power generation device having a waste heat recovery boiler, a gas engine power generation device using a lean gas engine, and the like can be given.

In these gas engine power generators,
The oxidation catalyst is installed in the exhaust gas flue. For example, in the case of a gas engine generator with a turbocharger, an oxidation catalyst can be installed in the exhaust gas flue downstream of the turbocharger. Alternatively, in the case of a gas engine power generator having a waste heat recovery boiler, the waste heat recovery boiler can be installed in the exhaust gas flue downstream of the oxidation catalyst.

The exhaust gas usually contains about 5 to 15% of water vapor that inhibits the oxidation reaction of methane. However, the oxidation catalyst used in the present invention has a high methane oxidation ability even for exhaust gas containing water vapor. Therefore, by installing a waste heat recovery boiler, a high steam recovery amount can be obtained stably. Further, even when a waste heat recovery boiler is not provided, methane in exhaust gas can be oxidized and removed.

Although the exhaust gas contains sulfur oxides which are known to significantly lower the catalytic activity, the oxidation catalyst used in the present invention is also highly resistant to activity reduction due to sulfur poisoning. Because of the resistance, effective methane oxidation capacity is maintained for a long time.

[0023]

According to the present invention, even if the main component of the hydrocarbon in the exhaust gas is a lower saturated hydrocarbon such as methane, it is possible to increase the waste heat recovery rate and improve the efficiency of the engine system. Becomes

[0024]

EXAMPLES Examples will be given below to explain the present invention in more detail. The present invention is not limited to the following examples.

Example 1 Method for Preparing 5% Pd-1% Pt / ZrO ₂ Catalyst Zirconium hydroxide was calcined at 600 ° C. for 9 hours to obtain zirconia. Pure water was added to an aqueous solution of palladium nitrate containing 1 g of palladium and an aqueous solution of tetraammineplatinum nitrate containing 0.2 g of platinum to make 15 ml, and 20 g of zirconia was impregnated at 0 ° C. for 15 hours. This was dried and further calcined at 550 ° C. for 9 hours in air to obtain a Pd—Pt / zirconia catalyst.

Embodiment 2 An engine system was constructed as shown in FIG. A turbocharger is installed downstream of the M company 380 kW engine,
A 5% Pd-1% Pt / ZrO ₂ catalyst prepared by the same method as in Example 1 was installed in the subsequent stream so that GHSV = 60000 h ^−1, and a waste heat recovery boiler was installed in the subsequent stream. Before contact with the catalyst, the exhaust gas had a sulfur oxide concentration of 0.3 ppm and a water vapor concentration of 10%.

Table 1 shows the conversion of hydrocarbons (THC conversion) and the amount of steam recovered from the boiler upon contact with the Pd-Pt / ZrO ₂ catalyst.

Comparative Example 1 Preparation of 5% Pd-1% Pt / Al ₂ O ₃ Catalyst Alumina (“NK-124”, manufactured by Sumitomo Chemical Co., Ltd.) was placed in the air.
It was baked at 800 ° C for 2 hours. Then, as an aqueous solution of palladium nitrate containing 1 g of platinum and 20 g of palladium as platinum
Pure water was added to an aqueous solution of tetraammineplatinum nitrate containing 0.2 g, and the mixture was immersed in a mixed solution of 15 ml for 15 hours, impregnated with palladium, dried, and further calcined in air at 550 ° C. for 2 hours. Thus, a Pd-Pt / Al ₂ O ₃ catalyst was obtained.

Comparative Example 2 The conversion of THC and the amount of recovered steam were measured under the same conditions as in Example 2 except that the Pd-Pt / ZrO ₂ catalyst was not installed.
Table 1 shows the results.

Comparative Example 3 As a catalyst, 5% Pd-1% Pt / Al ₂ O prepared in Comparative Example 1 was used.
_The THC conversion and the amount of recovered steam were measured under the same conditions as in Example 2 except that _three catalysts were used. Table 1 shows the results.

[0031]

[Table 1]

In Example 2, compared to Comparative Example 2, hydrocarbons such as methane were favorably oxidatively decomposed on the catalyst (methane decomposition rate: 70%), and the amount of steam recovered by the boiler was increased.
In addition, the Pd-Pt / ZrO ₂ catalyst exhibits a stable methane oxidation rate even in the presence of steam or sulfur oxide which inhibits the methane oxidation reaction, and a stable high steam recovery amount can be obtained.

On the other hand, the Pd-Pt / Al ₂ O ₃ catalyst shows a high THC conversion and a high steam recovery in the initial stage, but has no durability and can obtain a stable methane conversion and a high steam recovery. Can not.

[Brief description of the drawings]

FIG. 1 is an example of a gas engine power generation device of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ken Tabata 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Inventor Hirofumi Otsuka 4-chome, Hirano-cho, Chuo-ku, Osaka, Osaka No. 1-2 Inside Osaka Gas Co., Ltd. (72) Inventor Takenori Hirano 1385-2 No. 1 Sabuchi Fuchi, Izumi-shi, Kagoshima (72) Inventor Hiroshi Fujimoto 4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka No.F-term in Osaka Gas Co., Ltd. (reference) CA02 CA07 CA15 DA05 EA02Y EA18 EA19 ED07

Claims (6)

[Claims] 1. A gas engine power generator, wherein a catalyst comprising palladium on zirconium oxide is installed in the flue gas of the exhaust gas. 2. A gas engine power generator, wherein a catalyst comprising palladium and platinum supported on zirconium oxide is installed in the exhaust gas flue. 3. A gas engine power generator with a turbocharger, wherein a catalyst comprising palladium on zirconium oxide is installed downstream of the turbocharger. 4. A gas engine power generator with a turbocharger, wherein a catalyst comprising palladium and platinum supported on zirconium oxide is installed downstream of the turbocharger. 5. The gas engine power generator according to claim 1, wherein a heat recovery boiler is installed to recover heat. 6. The gas engine power generator according to claim 1, wherein the gas engine is a lean gas engine.