JPS6280419A - Combustion catalyst system for low class hydro-carbon fuel and combustion method of using this system - Google Patents

Abstract

PURPOSE:To provide a combustion catalyst system for a low class hydro-carbon fuel by arranging a front-stage catalyst layer, an intermediate catalyst layer and a rear-stage catalyst layer each having a specified substance. CONSTITUTION:A front-stage catalyst layer filled with catalyst containing active constituents composed of palladium and platinum is arranged at an gas inlet side, a rear-stage catalyst layer filled with catalyst containing a kind of substance selected from active constituents composed of platinum and active substance composed of platinum and palladium is arranged at an outlet side, and an intermediate-stage catalyst layer filled with catalyst containing active substances composed of palladium, platinum and nickel oxide is arranged between the front-stage catalyst layer and the rear-stage catalyst layer. When combustible mixture gas containing low class hydro-carbon having the number of the carbons 1-4 and molecular oxygen, in particular flame retardant methane or natural gas containing methane is contacted to these layers and ignited there, it is possible to get a combustion gas not containing harmful constituent. Its calorie can be applied for various sources of energy.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a combustion catalyst system for lower hydrocarbon fuel and a combustion method using the same. To be more specific, carbon atoms such as methane, ethane, propane, butane, etc.
~4 lower hydrocarbon fuels, especially flame-retardant methane or natural gas containing methane as a main component, are catalytically burned to produce nitrogen oxides (hereinafter referred to as NOX), -carbon oxides (
A catalyst system that obtains combustion gas that does not substantially contain harmful components such as unburned hydrocarbons (hereinafter referred to as CO) and unburned hydrocarbons (hereinafter referred to as UHC), and uses that heat as various energy sources, and combustion using the same. It is about the method.

<Prior art> A catalytic combustion system is known in which a dilute 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 obtain high-temperature combustion gas. .

Furthermore, using such a catalytic combustion system, e.g.
When obtaining combustion gas at a temperature of 00°C to 1500°C, for example, even if air is used as an oxygen source, little or no NOx is generated, and it is often obtained that does not substantially contain Co or tJHc. 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 begun to be conducted on the use of this high-temperature combustion gas as a secondary power source for power generation gas turbines and the like.

When used for these purposes, the combustion gas is normally brought to a high temperature of 1000 to 1300°C under 6 to 15 atmospheres, and there is a tendency for the combustion gas to reach even higher temperatures and pressures to improve the efficiency of gas turbines. It is in.

If a catalyst is used under such conditions, a normal catalyst would deteriorate rapidly due to high temperatures, and in the worst case scenario, the catalyst carrier could 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, fuel is combusted in the catalyst layer, the gas temperature is raised to a temperature that induces secondary combustion, and then the gas remains behind the catalyst layer. Either perform secondary combustion of unburned fuel, or introduce secondary fuel if necessary, and secondary combustion of remaining unburned fuel and newly added secondary heat to reach the desired temperature, or A combustion method has been discovered that produces clean combustion gas at a higher 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 secondary combustion is induced. If the gas temperature reaches the above temperature, there is no need to raise the temperature higher in the catalyst layer, in order to avoid deterioration and damage to the catalyst, and to maintain stable secondary combustion. It is preferable to have a large amount of unburned fuel.

The entire amount of fuel that can reach the desired temperature may be introduced into the catalyst layer, a portion of which may be combusted to raise the temperature, and then 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 behind the catalyst layer and combined with the remaining unburned fuel for secondary combustion. In this case, it is more preferable that the temperature of the catalyst layer be avoided to be higher than necessary, and deterioration and damage to the catalyst can be avoided.

The temperature required to induce secondary combustion here is determined by the type of fuel, residual fuel concentration (theoretical adiabatic combustion gas temperature), linear velocity, etc., and varies widely depending on the type of fuel.

−〇 − 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;
When using flame-retardant methane or natural gas whose main component is methane, 7.
High temperatures of 50-1000°C are required.

<Object of the Invention> Accordingly, an object of the present invention is to provide a novel catalyst system for combustion of lower hydrocarbon fuels.

Another object of the present invention is to catalytically burn low-grade hydrogen fuel, particularly flame-retardant methane or natural gas containing methane as a main component, to obtain a combustion gas that does not substantially contain harmful components, and to reduce the amount of heat in various ways. The object of the present invention is to provide a catalyst system for use as an energy source and a combustion method using the same.

A further object of the present invention is to ignite methane, which is said to be relatively flame-retardant among hydrocarbons, or a natural gas fuel containing methane as a main component at low temperature using a catalyst at a high linear velocity and from normal pressure to high pressure. , the temperature is raised to a temperature sufficient to induce secondary combustion, and then secondary fuel is introduced as necessary to combust the remaining unburned fuel and secondary fuel to reach the target temperature or lower. The object of the present invention is to provide a catalyst system that can be suitably used in a combustion system that reaches temperatures above -L, and a combustion method using the catalyst system.

Another object of the present invention is to ignite flame-retardant fuel, mainly methane, at a high linear velocity and under pressure at as low a temperature as possible, to raise the combustion gas temperature to a humidity of 750 to 1000°C, and The object of the present invention is to provide a catalyst system having low pressure loss and durability, and a combustion method using the same.

<Means of the Invention> In these various methods, a catalyst containing an active component consisting of palladium and platinum is filled on the gas inlet side with respect to a flow of a flammable mixed gas containing lower hydrocarbons and molecular oxygen. and a latter catalyst layer filled with a catalyst containing one selected from the group consisting of an active component made of platinum and an active component made of platinum and palladium on the outlet side. and a middle catalyst layer filled with a catalyst containing an active component of palladium, platinum, and nickel oxide between the front and rear catalyst layers, and to provide a combustion catalyst system. supplying the combustible gas mixture to a system and raising the temperature of the combustion gas to a temperature at which at least a portion of the lower hydrocarbons in the gas mixture is catalytically combusted in the catalyst system to induce secondary combustion; This is achieved by providing a method of combustion of lower hydrocarbon fuel.

The catalyst system according to the present invention essentially has three catalyst layers: a catalyst that can be ignited at a relatively low temperature used in the front layer and a middle layer, and a catalyst that can ignite at a relatively low temperature used in the rear layer, and a catalyst that can ignite at a temperature of 750 to 1000 degrees Celsius. - The catalyst used in the first layer consists of palladium and platinum as active ingredients, and the catalyst used in the middle layer consists of the following: The active ingredients are palladium, platinum, and nickel oxide, and the catalyst used in the latter layer is platinum or platinum and palladium as the active ingredients, and the combustion temperature in the catalyst layer does not exceed 1000°C. This is how it is made.

Catalysts containing palladium as the main active component are known to have particularly poor low-temperature ignition properties for methane, and are also excellent in heat resistance at high temperatures of about 1000°C.

However, when a conventional catalyst containing palladium as an active ingredient is used for the purpose of the present invention, the catalyst layer is exposed to high concentrations of oxygen at temperatures below 500°C near sunrise, so palladium is oxidized and impairs methane ignition performance. On the other hand, in the high temperature range near the catalyst layer ratio roy, the combustion reaction by the catalyst is suppressed, probably due to a change in the oxidation state of palladium, and the combustion gas temperature is actually 7.
It has the disadvantage that it cannot rise to a high temperature of 50°C or higher.

In contrast, according to the present invention, by coexisting a small amount of platinum in the front stage catalyst of the catalyst system, the deterioration of methane ignition performance due to palladium oxidation is prevented, and low-temperature ignition performance is maintained for a long period of time. It was discovered that the combustion gas temperature could be stably maintained at 600 to 7 bO℃ at high linear velocity and under pressure. Further promoted, combustion gas is 750-100
It has been found that it is possible to reach temperatures of 0°C.

As a result, methane or natural gas fuel containing methane as a main component can be ignited at high linear velocity, under pressure, and at low temperatures.
It became possible to raise the temperature of combustion gas to 1,000°C, and to maintain this performance for a long time.

In particular, in the present invention, it is preferable that nickel oxide coexists with palladium and platinum in the middle catalyst provided between the front and rear catalyst layers. In addition to improving low-humidity ignition performance, the presence of nickel as an oxide provides a stable supply of oxygen to palladium, so even at high linear speeds and under pressure, the combustion gas temperature can be reduced to 650-900%.
It is possible to raise the temperature to ℃.

It is also preferable that palladium be present as an active component in the catalyst of the latter catalyst layer. In this case, the presence of palladium further accelerates combustion, and
It has been discovered that platinum can be prevented from being oxidized to PTO2 and sublimated even at high temperatures.

In the present invention, the first half of the catalyst system has a two-stage structure, in which the first half is a layer of the above-mentioned first stage catalyst containing palladium-platinum as an active ingredient, and the second half is a layer of palladium-platinum.
By using nickel oxide as the active component in the middle catalyst layer, the combustion activity of the first half catalyst system is improved even under high linear velocity and pressurized conditions.
This made it possible to smoothly perform the combustion function of the post-catalyst containing palladium as an active ingredient.

In this case, in the first half of the first half of the catalyst system -12
= The temperature is raised to a temperature in the range of 500 to 800 °C, and the temperature in the latter half of the first half catalyst system (middle stage catalyst layer) is raised to 650 to 90 °C.
Temperatures in the range of 0°C and 750 to 750°C in the downstream catalyst layer
By respectively raising the temperature to a range of 1000° C., combustion activity is maintained at a high level.

This catalyst system is characterized by a three-stage structure that takes advantage of the characteristics of each precious metal or combines them. In other words, in this catalyst system, the temperature
It is necessary to ignite at a low temperature of , have combustion activity to achieve a combustion gas temperature of 750 to 1000°C, and have heat resistance at 1000°C or higher.

However, as described above, palladium alone does not lose its ignition performance as the combustion progresses, and due to its characteristics, the combustion gas temperature does not substantially rise to a high temperature of 750° C. or higher. Even a palladium-nickel oxide catalyst loses its ignition performance in the same way as palladium alone. In addition, when platinum alone is used for combustion with methane or LNG, the combustion rate is 300 to 400.
Although it is impossible to ignite at temperatures above 500°C and requires an ignition temperature of 500°C or above, it has excellent combustion activity, especially under high linear velocity and pressurized combustion conditions. . In addition, palladium-platinum-nickel oxide or palladium-platinum based catalyst t1. 'c has sufficient ignition performance, but
The combustion gas temperature cannot be made higher than the temperature at which secondary combustion is induced under high linear velocity and pressurized combustion conditions.

As described above, each of the one-stage configurations has drawbacks and cannot be used as a practical catalyst, especially under pressurized combustion conditions, and is not preferred.

The total catalyst bed length varies depending on the inlet linear velocity used, but
A length of 50 to 500 m is usually adopted due to the need to reduce pressure loss, and the lengths of the front layer, middle layer, and rear layer are also optimally selected depending on usage conditions such as inlet linear velocity and inlet temperature.
Normally, each layer has a length of 20 to 250 m.

The catalyst used in the first layer is usually the monolithic water supported by
Alumina, silica-alumina, magnesia, titania,
It is used by coating with an active refractory metal oxide such as zirconia or silica-magnesia, preferably alumina, titania, or zirconia. The amount of oxide coated is 5 to 50% by weight, preferably 10 to 30% by weight, based on the finished catalyst.

Alumina is particularly preferable, and an alkaline earth metal oxide such as barium or strontium, a rare earth metal oxide such as lanthanum, cerium, neodymium or praseodymium, or silicon, preferably a rare earth metal oxide, is added and used in stabilization 1. and more preferable. The amount added is 2 to 20% by weight, preferably 5 to 15% by weight, based on the oxide. Thereafter, active main components such as palladium and platinum are impregnated in the form of water-soluble or alcohol-soluble compounds and catalyzed. Alternatively, it is also possible to catalyze by previously supporting the active main component with an active, refractory metal oxide, and then converting it into a monolithic carrier.

The active ingredient, platinum, can also be supported together with an active refractory metal oxide as platinum black having an average particle size of 0.01 to 5 microns.

Examples of water-soluble salts include nitrates, sulfates, phosphates, halides, and di-1-rosyamino salts. - Examples include palladium nitrate, palladium chloride, dinitrodiaminoplatinum, chloroplatinic acid, etc., by impregnating a carrier with an aqueous solution of these and heating at a temperature of 400 to 1000°C, preferably 600 to 900°C. 24 hours, preferably 2
Obtained by baking for ~6 hours.

The supported amount of the active component of the catalyst used in the first layer is 0.5 to 15% by weight as palladium, 10% by weight as palladium, and 0.1 to 10% by weight as platinum per finished catalyst.
, preferably (0.2 to 5% by weight, and the weight ratio of platinum to palladium is 0.01 to 1, preferably 0.1 to 5% by weight)
It is in the range of 0.6.

The catalyst for the middle layer is prepared in the same manner, but nickel nitrate or nickel chloride is used as the nickel source. The palladium/nickel ratio in the catalyst layer containing palladium-platinum-nickel oxide as an active component is pd/N.
iO weight ratio 0.001 to 20, preferably 0.1 to 5
Can be used in combination within the range.

Similarly, the catalyst used in the latter layer can be catalyzed by supporting platinum or platinum and palladium.

The amount of active component supported is 0.1 to 1 platinum per finished catalyst.
5% by weight, preferably 0.2-10% by weight, and if palladium is added, 0.1% as palladium.
-15% by weight, preferably 0.2-10% by weight, and in the case of catalysts that release palladium and platinum as active components, the weight ratio of platinum to palladium is 0.
．． It ranges from 0.01 to 20, preferably from 0.2 to 10.

When only platinum is used as an active ingredient, the catalyst is too highly active, and the temperature in the catalyst layer may rise to over 1000° C., causing deactivation due to sublimation of platinum. In order to avoid this and keep the catalyst layer temperature below 1000 degrees Celsius, it is particularly preferable to use coarse platinum particles such as platinum black, or to reduce the amount of platinum supported, or to prepare the finished catalyst before use. Examples include a method in which the catalyst is fired at a high temperature exceeding 1000° C., and a method in which the cell size and body length of the catalyst are optimally selected. Further, by coexisting palladium with platinum, it is possible to prevent sublimation of platinum, and it is also possible to control the combustion activity of platinum.

These depend on the conditions of use, i.e. fuel type, temperature (
It can be optimally selected depending on the theoretical adiabatic combustion gas temperature), linear velocity, pressurization conditions, etc. Pressurization conditions can be from normal pressure to 25 atm, but preferably from 6 to 15 atm.
It is atmospheric pressure. For a combustion F3i of 111 degrees, if the lower hydrocarbon fuel is methane, the amount of 1.51 to 4.75 volume %, preferably 2.37 to 4.31 volume %, depending on the temperature of the mixed gas introduced into the catalyst system. It is a primary fuel and the -
If secondary fuel is further supplied to the combustion gas that has been heated to a temperature that induces secondary combustion by the secondary fuel, O ~
3.24 volume %, preferably 0.44 to 2.38 volume %
It is. Furthermore, the linear velocity is 7 to 40 m/sec, preferably 10 to 30 m/sec. That is, when the speed is less than 7 m/sec, a flashback phenomenon may occur, while when the speed exceeds 4.0 m/s, excessive blow-by of the fuel occurs, resulting in insufficient combustion.

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 over 80% methane, although the composition ratio varies slightly depending on the region of production.

Further, fermented methane from activated sludge treatment and low-calorie methane gas from coal gasification are also fuels used in the present invention. Ethane, propane, and butane, which are more easily flammable, can also be used, and of course light oil and the like 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 Straight 1 yen 25 with 200 cells/flat j inch opening
A slurry of alumina powder containing 5 wt. The weight percentages were matched.

This was then immersed in an aqueous solution containing palladium nitrate and di-1-[J diaminoplatinum, dried, and dried in air for 90 minutes.
Calcinate at 0°C for 5 hours to obtain 4 palladium per finished catalyst.
．． A completed catalyst was obtained by loading 0% by weight of platinum and 0.8% by weight of platinum.

Example 2 In the same manner as in Example 1, 1.2% by weight of palladium and 93% by weight of platinum carbon dioxide were supported on the finished catalyst to obtain a C finished catalyst.

20 Example 3 The same carrier as in Example 1 was coated with a slurry of alumina powder containing 7% by weight of lanthanum oxide and 3% by weight of neodymium oxide, and the finished catalyst was calcined at 800°C in air. 30% by weight of alumina containing lanthanum oxide and neodymium oxide was supported and coated. Next, this support was immersed in an aqueous solution containing palladium nitrate and chloroplatinic acid, dried, and then calcined in air for 5 hours to obtain 4.7% by weight of palladium and 1.3% by weight of platinum per finished catalyst. A completed catalyst was obtained by supporting the catalyst.

Example 4 A mixed slurry of alumina powder containing 5% by weight of lanthanum oxide and nickel oxide was prepared in the same carrier as in Example 1, and 19% by weight of alumina containing lanthanum oxide and 6% by weight of nickel oxide were added per finished catalyst as in Example 1. % by weight was coated.

Then, in the same manner as in Example 1, 460% by weight of palladium and 0.8% by weight of platinum were supported on the finished catalyst to obtain a finished catalyst.

Example 5 A finished catalyst was obtained in the same manner as in Example 4, with 6% by weight of nickel oxide, 2.0% by weight of palladium, and 0.8% by weight of platinum supported on the finished catalyst.

Example 6 Diameter 25,4 with 100 cells/square inch aperture
A slurry of alumina powder containing 8% by weight of lanthanum oxide and 2% by weight of silica and platinum black powder having an average particle size of 1 micron were filled and mixed into a mullite honeycomb carrier with a length of 50 mm and coated. After drying, the product was calcined in air at 900° C. for 2 hours to obtain a finished catalyst in which 18% by weight of alumino powder containing lanthanum oxide and silicon dioxide and 2.2% of platinum were supported on the finished catalyst.

Example 7 A finished catalyst was obtained in exactly the same manner as in Example 6 except that the amount of platinum black supported was 0.6%.

Example 8 Diameter 25,4 with openings of 200 cells/square inch
A slurry of alumina powder containing 8% by weight of lanthanum oxide and 2% by weight of praseodymium oxide was prepared in the same manner as in Example 1 on an aluminum titanate honeycomb support of 21 mm by weight. % coverage was carried out.

This was then immersed in a filtrate solution containing chloroplatinic acid as in Example 1 to yield 2.0 platinum per C finished catalyst.
A finished catalyst was obtained by loading % by weight.

Comparative Example 1 A finished catalyst containing no platinum was obtained in the same manner as in Example 4.

Comparative Example 2 A finished catalyst was obtained in the same manner as in Example 1 except that it did not contain platinum, and 3.6% by weight of palladium was supported on the -C finished catalyst.

Example 9 Using a sufficiently warmed cylindrical combustor, from the l-flow side, the catalyst obtained in Example 1 was placed in the front layer, the catalyst obtained in Example 4 was placed in the middle layer, and the catalyst obtained in Example 6 was placed in the rear layer. The resulting catalyst was charged, and a methane-air mixture containing 3% by volume of methane was heated at an inlet temperature of 1,350°C under a pressure of 10 atm.
167 N'rd per hour.

-C combustion efficiency and catalyst layer outlet temperature were measured.

In this case, the catalyst inlet linear velocity was about 30 m/sec.

As a result, the combustion efficiency was about 771%, and the catalyst layer outlet temperature was about 810°C.

Next, when the methane concentration was increased to 4.1% by volume, the combustion efficiency reached 100%, and a clean combustion gas containing substantially no u+-+c, co, or NOx was obtained. In this case, the white temperature 100 m behind the catalyst layer reached about 1300°C, but the catalyst bed outlet temperature was about 870°C.

Next, methane equivalent to 3% by volume was introduced from upstream of the catalyst layer, and methane equivalent to the remaining 1.1% by volume was introduced 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 obtained.

This performance has been maintained for over 1000 hours.
.

Example 10 In the same manner as in Example 9, using the catalysts shown in Table 1, 3
Table 1 shows the results of a combustion experiment in which methane equivalent to 1.1% by volume was introduced from upstream of the catalyst layer, and methane equivalent to 1.1% by volume was introduced from 30# behind the outlet of the catalyst layer. Using the catalyst system according to the present invention, clean combustion gas of approximately 1300°C was obtained even though the catalyst bed temperature was maintained at 1000°C or lower, which did not cause a decrease in activity. The catalyst system using the catalyst obtained in Comparative Example 1 in the middle stage and the catalyst obtained in Example 6 in the latter stage rapidly became unable to ignite.

Next, in the catalyst system using the catalyst obtained in Comparative Example 2 or Example 6 in the first stage, Example 4 in the middle stage, and Comparative Example 1 in the second stage, the catalyst bed outlet temperature was 650 to 690 °C, and both at the rear of the catalyst bed. The secondary combustion of f)X7 was not induced.

-27 Example 11 The catalyst obtained in Example 2 in the same manner as in Example 9,
The middle stage was filled with the catalyst obtained in Example 5, and the latter stage was filled with the catalyst obtained in Example 7.
Add propane equivalent to 3% from upstream of the IM layer, remaining 0.
A combustion experiment was conducted by introducing propane equivalent to 5% from 30 mm behind the outlet of the catalyst layer.

As a result, the catalyst layer ratio [1 temperature is 920°C, IJH
A clean combustion gas of approximately 1300° C. containing substantially no C, Co and NOx was replaced.

Moreover, this performance has been maintained for 15 years.

Claims (3)

[Claims] (1) For a flow of a combustible mixed gas containing a lower hydrocarbon having 1 to 4 carbon atoms and molecular oxygen, a catalyst containing an active component made of palladium and platinum is packed on the gas inlet side. and a latter catalyst layer filled with a catalyst containing one selected from the group consisting of an active component made of platinum and an active component made of platinum and palladium on the outlet side. Combustion of a lower hydrocarbon fuel, characterized in that a middle catalyst layer filled with a catalyst containing an active component of palladium, platinum and nickel oxide is provided between the front and rear catalyst layers. catalyst system. (2) Each active ingredient is dispersed and supported on a monolithic carrier coated with at least one refractory oxide selected from the group consisting of alumina, silica-alumina, magnesia, titania, zirconia, and silica-magnesia. A catalyst system according to claim (1), characterized in that: (3) For a flow of a combustible mixed gas containing lower hydrocarbons having 1 to 4 carbon atoms and molecular oxygen, a catalyst containing an active component of palladium and platinum is packed on the gas inlet side. and a latter catalyst layer filled with a catalyst containing one selected from the group consisting of an active component made of platinum and an active component made of platinum and palladium on the outlet side. The combustible mixed gas is fed into a combustion catalyst system comprising a middle catalyst layer filled with a catalyst containing an active component of palladium, platinum and nickel oxide between the front and rear catalyst layers. and catalytically combust at least a portion of the lower hydrocarbons in the mixed gas in the catalyst system to raise the temperature of the combustion gas to a temperature at which secondary combustion is induced. Combustion method.