JP5610513B2 - Dry ammonia decomposition treatment method, dry ammonia decomposition treatment apparatus and power generation equipment - Google Patents

Description

  The present invention relates to a dry ammonia decomposition treatment method, an ammonia decomposition treatment apparatus, and a power generation facility, and more particularly, to a case where the ammonia in a fuel gas containing ammonia such as coal gasification gas and rich in hydrogen and carbon monoxide is decomposed dry. It is useful.

Coal gasification combined cycle power generation (IGCC) has been proposed as an environmentally friendly technology that uses abundant coal in a clean manner while suppressing CO ₂ emission. In the combined coal gasification combined power generation, gas purification is performed to remove impurities such as sulfur and ammonia in the coal gasification gas generated in the coal gasification furnace. And while supplying this refined gas to a gas turbine as fuel gas and driving this, the steam turbine is driven with the exhaust heat, and highly efficient electric power generation is enabled.

  By the way, a wet method has been mainly employed as a gas purification system in this type of coal gasification combined power generation. However, although the wet process is technically complete, the fuel gas is cooled to a low temperature, which causes sensible heat loss, water vapor loss, and the like, resulting in reduced thermal efficiency.

  Therefore, development of a dry gas purification system is being studied in order to further improve power generation efficiency. As part of this, a dry ammonia decomposition method as exemplified in Patent Document 1 is also being studied. This was devised to selectively advance the decomposition reaction of ammonia in the fuel gas into nitrogen and water, and to suppress the reaction of compounds containing carbon atoms such as carbon monoxide to carbon on the catalyst surface. Is.

JP 2006-56935 A

  In refining gases containing combustible gas components along with ammonia, such as the coal gasification gas mentioned above, it is possible to accelerate the decomposition reaction of ammonia and at the same time to react with other combustible gas components that cause deterioration of the fuel gas. It is important to suppress it. Even in the case disclosed in the above-mentioned Patent Document 1, the decomposition reaction of the ammonia in the gas is promoted and the reaction of the combustible component of the other fuel gas is suppressed, but the fuel gas is more effectively deteriorated as the fuel. Development of a catalyst capable of favorably promoting the decomposition reaction of ammonia in the gas while suppressing the above is awaited.

  In addition, as described above, the ammonia decomposition reaction is promoted, and at the same time, the reaction of other combustible gas components is suppressed as much as possible. For example, fuel such as biomass, heavy oil, municipal waste, etc. is used in a gasifier. The same applies when purifying combustible gas obtained by thermal decomposition. Since all of these contain nitrogen compounds in the raw material, ammonia is generated and mixed into the fuel when the fuel is gasified. However, if the fuel gas mixed with ammonia is burned as it is, This is because fuel NOx is generated by the reaction of nitrogen and oxygen.

  In view of the above, the present invention provides a dry ammonia decomposition treatment method and an ammonia decomposition treatment apparatus capable of favorably promoting the decomposition reaction of ammonia in gas while suppressing deterioration as a fuel as much as possible. For the purpose.

  In addition, in view of the above-described points, the present invention provides a power generation facility including a dry ammonia decomposition treatment apparatus that can favorably promote the decomposition reaction of ammonia in fuel gas while suppressing deterioration as a fuel as much as possible. The purpose is to provide.

In order to achieve the above object, the dry ammonia decomposition treatment method of the present invention according to claim 1 comprises adding oxygen to a gas containing ammonia together with a combustible compound containing carbon atoms, and bringing the gas added with oxygen into contact with the catalyst. In the dry ammonia decomposition method for decomposing the ammonia and purifying the fuel gas, the catalyst is transitioned using ZSM-5, which is a zeolite having 10-membered ring and SiO ₂ and Al ₂ O ₃ as constituents, as the catalyst. What carries | supports nickel which is a metal is used, It is characterized by the above-mentioned.

With the present invention according to claim 1, and the ZSM-5 is a zeolite and 10-membered oxygen ring in the component SiO _2, Al ₂ O ₃ gas together with oxygen by supporting nickel is a transition metal as a supported catalyst By making it contact, the reaction which decomposes | disassembles ammonia in gas into nitrogen and water can be accelerated | stimulated favorably. On the other hand, other ammonia reactions (formation of nitrogen compounds such as nitrogen monoxide, nitrogen dioxide, nitrous oxide and hydrogen cyanide) and gas reactions (reactions such as oxidation of hydrogen and carbon monoxide, production of carbon and hydrocarbons) ) Can be suppressed as much as possible.

The dry ammonia decomposition treatment method of the present invention according to claim 2 is the dry ammonia decomposition treatment method according to claim 1 , wherein the reaction temperature when decomposing the ammonia is 200 ° C to 450 ° C. Features. Further, the dry ammonia decomposition treatment method of the present invention according to claim 3 is the dry ammonia decomposition treatment method according to claim 1 or 2 , wherein the oxygen is added in a molar ratio of 0.1 to the ammonia. It is 75 mol / mol or more and 15 mol / mol or less.

In the present invention according to claim 2 , the reaction temperature can be made appropriate, and in the present invention according to claim 3 , the amount of oxygen added can be made appropriate.

In order to achieve the above object, a dry ammonia decomposition treatment apparatus according to claim 4 of the present invention includes an oxygen addition means for adding oxygen to a gas containing ammonia together with a combustible compound containing carbon atoms, and an oxygen addition means by the oxygen addition means. And a catalyst for decomposing ammonia in the gas by contact with the gas, wherein the catalyst is ZSM-5, wherein SiO ₂ and Al ₂ O ₃ are constituents and a 10-membered oxygen zeolite It is a catalyst which supported nickel which is a transition metal by using as a carrier.

With the present invention according to claim 4, and the ZSM-5 is a zeolite and 10-membered oxygen ring in the component SiO _2, Al ₂ O ₃ gas together with oxygen by supporting nickel is a transition metal as a supported catalyst By making it contact, the reaction which decomposes | disassembles ammonia in gas into nitrogen and water can be accelerated | stimulated favorably. On the other hand, other ammonia reactions (formation of nitrogen compounds such as nitrogen monoxide, nitrogen dioxide, nitrous oxide and hydrogen cyanide) and gas reactions (reactions such as oxidation of hydrogen and carbon monoxide, production of carbon and hydrocarbons) ) Can be suppressed as much as possible.

In the present invention according to claim 4 , it is possible to promote the decomposition reaction by selective oxidation of ammonia, and at the same time, allow oxygen to enter into a state in which the reaction of carbon monoxide or the like being decomposed into carbon on the surface of the catalyst is suppressed. A pore structure can be applied to support nickel.

In order to achieve the above object, a power generation facility according to a fifth aspect of the present invention provides a gasification furnace for generating gas, and ammonia in the gas generated in the gasification furnace in a dry manner . A dry ammonia decomposition apparatus and a power generation means for generating electricity using the purified gas purified by the dry ammonia decomposition apparatus as a fuel.

In the present invention according to claim 5 , the reaction of decomposing ammonia in the gasification gas into nitrogen and water is favorably promoted, and other ammonia reactions (nitrogen monoxide, nitrogen dioxide, nitrous oxide, hydrogen cyanide, etc.) Nitrogen compound formation) and gas reaction (hydrogen, carbon monoxide oxidation, carbon, hydrocarbon production, etc.) are suppressed as much as possible, and the purified gas is used as fuel gas. Can be used for power generation, and power generation efficiency can be improved.

And the power generation equipment of the present invention according to claim 6 is the power generation equipment according to claim 5 , wherein the gasifier is a coal containing ammonia together with a combustible component containing carbon, hydrogen, etc., as the coal is thermally decomposed. It is a coal gasification furnace in which gasification gas is generated.

In the present invention according to claim 6 , power generation can be performed using coal gasification gas as fuel gas.

  According to the present invention, the reaction of decomposing ammonia in the gas into nitrogen and water can be favorably promoted by bringing the gas into contact with the catalyst together with oxygen. On the other hand, other ammonia reactions (formation of nitrogen compounds such as nitrogen monoxide, nitrogen dioxide, nitrous oxide and hydrogen cyanide) and gas reactions (reactions such as oxidation of hydrogen and carbon monoxide, production of carbon and hydrocarbons) ) Can be suppressed as much as possible.

  As a result, it is possible to perform high-quality gas purification by satisfactorily decomposing ammonia contained in the gas while suppressing deterioration of the gas as fuel as much as possible.

It is a block diagram which shows the coal gasification gas power generation equipment which concerns on embodiment of this invention. It is a flowchart which shows the adjustment procedure of a sample catalyst. It is explanatory drawing which shows the temperature and fuel supply program in a basic experiment. It is a graph which shows the ammonia decomposition characteristic of each sample catalyst. Is a graph showing the production characteristics of the N _{2 O} of each sample catalyst. It is a graph which shows the production | generation characteristic of HCN of each sample catalyst. CO of each sample catalyst is a graph showing the reaction-product properties of CO _2. Is a graph showing the reaction-product properties of _H 2, CH ₄ of each sample catalyst.

  Hereinafter, embodiments of the present invention will be described in detail.

  The dry ammonia decomposition method according to the present embodiment is intended to treat a gas containing ammonia together with a combustible component containing carbon atoms, and decomposes the ammonia contained in the gas by contacting it with a catalyst. That is, an amount of oxygen that cannot gas-phase-combust the gas upstream of the catalyst is added to the gas to be brought into contact with the catalyst, and nitrogen and water by selective oxidation of ammonia in the gas are added by oxygen supplied to the surface of the catalyst. At the same time, the decomposition reaction of carbon monoxide, which is a combustible component, is suppressed to carbon on the surface of the catalyst.

Here, as the catalyst in the present embodiment, a catalyst using an oxygen 10-membered ring (10-membered ring structure ) zeolite as a carrier is suitable. Here, the 10-membered ring means a membered ring structure having 10 oxygen atoms.

  In an 8-membered oxygen zeolite with a small pore diameter, oxygen having a large molecular size is unlikely to enter the pores, and therefore, selective oxidation reaction with ammonia does not easily occur in the pores. On the other hand, zeolite having a structure with a large pore diameter and having a 10-membered ring or more oxygen allows oxygen to easily enter the pores, so that the selective oxidation reaction with ammonia in the pores is promoted. However, the larger the pore diameter, the easier the growth of carbon and the polymerization of the carbon-containing compound in the pores, and the easier the carbon deposition occurs.

Therefore, at the same time to promote the decomposition reaction by selective oxidation of ammonia to suppress the reaction such as carbon monoxide on the surface of the catalyst is decomposed to carbon, the pore structure is 10-membered ring structure of the zeolite Is optimal. The zeolite 10-membered ring structure can be mentioned ZSM-5 zeolite and.

As the silica / alumina ratio is increased, the crystal stability of the zeolite is improved, and the structure of the zeolite is maintained even under high temperature and high steam conditions, so that the catalyst life is extended. As the active substance of the catalyst, nickel which is a transition metal is suitable.

That is, the catalyst of the present embodiment is a zeolite bets 10-membered ring structure is formed by supporting nickel as a carrier. Here, there is no particular limitation on the shape of the catalyst. Any of a powder form, a pellet form, a honeycomb form and the like may be used. Also, there is no particular limitation on the active substance loading form.

  That is, a transition metal such as nickel may be supported on at least the surface of a carrier having a predetermined shape, or a transition metal may be supported on a powder carrier and used as it is or in a granular form. Further, it may be formed into a slurry shape, poured into a mold, fired, and formed into a predetermined shape such as a honeycomb.

  As a gas containing ammonia together with a combustible component containing carbon atoms, for example, a coal gasification gas generated in a coal gasification furnace is suitable. Incidentally, the coal gasification gas generated in the coal gasification furnace is a gas containing carbon monoxide and hydrogen as main components of combustibles and other gases such as methane and ammonia.

  Further, it is desirable that the amount of oxygen added for promoting selective oxidation and at the same time suppressing the reaction in which the combustible components are decomposed is 0.75 mol / mol or more and 15 mol / mol or less in terms of a molar ratio with respect to ammonia. In order to avoid gas phase combustion, it is necessary to make the concentration below the critical oxygen concentration. Incidentally, in the case of a gas containing 1000 ppm of ammonia (coal gasification gas), the oxygen concentration with a molar ratio to ammonia of 15 mol / mol is 1.5 vol%.

  Here, the critical oxygen concentration refers to an oxygen concentration at which a combustible gas cannot be vapor-phase combusted at a predetermined temperature and pressure. Hydrogen is 1.5 vol%, carbon monoxide is 5.6 vol%, and methane is 12. 1 vol%, ammonia is more than that. Since this critical oxygen concentration changes depending on the temperature and pressure of the reaction field, it is important to adjust it according to the operating conditions. The reaction temperature during ammonia decomposition is preferably about 200 ° C. to 450 ° C.

According to the present embodiment, when the gas contacts the catalyst,
4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O
The selective oxidation reaction of ammonia is promoted, while other ammonia reactions (formation of nitrogen compounds such as nitric oxide, nitrogen dioxide, nitrous oxide, hydrogen cyanide) and gas reactions (hydrogen, carbon monoxide It is possible to purify the gas while effectively suppressing oxidation, reaction of carbon, production of hydrocarbons, and the like.

  FIG. 1 shows an ammonia decomposition treatment apparatus that realizes such an ammonia decomposition treatment method together with a coal gasification gas power generation facility to which the ammonia decomposition treatment apparatus is applied. As shown in the figure, in the coal gasification furnace 1, coal as a raw material supplied together with oxygen is pyrolyzed to generate coal gasification gas containing ammonia together with combustible components including carbon, hydrogen and the like.

  Here, oxygen is obtained by separating from the air taken into the air separation device 2 in this embodiment, and this oxygen is obtained by further compressing the air supplied from the compressor of the gas turbine by the compressor 3. It is mixed with air and supplied to the coal gasifier 1. Here, the coal gasification furnace 1 is constituted by, for example, an oxygen-enriched air blown-bed gasification furnace. Further, only the air may be directly supplied into the coal gasification furnace 1 without adding oxygen.

  The coal gasification gas generated in the coal gasification furnace 1 contains sulfur, impurities such as ammonia, and other dusts, and is therefore subjected to gas purification by the gas purification equipment 4 in the next stage. The gas purification equipment 4 in this example is connected in series from a porous filter 5 that performs dry dust collection, a desulfurization treatment device 6 that performs dry desulfurization treatment, and an ammonia decomposition treatment device 7 that performs dry ammonia decomposition treatment from the upstream side toward the downstream side. Configured.

  Therefore, the gas after dust collection and desulfurization is supplied to the ammonia decomposition treatment device 7. Thus, poisoning of the catalyst for the ammonia decomposition treatment with hydrogen sulfide can be prevented. Here, the gas introduced into the ammonia decomposition treatment apparatus 7 contains ammonia together with the combustible compound containing carbon atoms.

  The ammonia decomposition treatment apparatus 7 in this embodiment decomposes ammonia into nitrogen and water by introducing coal gasification gas together with oxygen into a reaction vessel filled with a catalyst for ammonia decomposition.

Here, as the catalyst Aru zeolites 10-membered ring structure formed by supporting the nickel is a transition metal as a carrier. The oxygen introduced together with the coal gasification gas is supplied from the air separation device 2.

  The amount of oxygen at this time is 0.75 mol / mol or more and 15 mol / mol or less in terms of a molar ratio with respect to ammonia, and the reaction temperature at the time of ammonia decomposition is about 200 ° C. to 450 ° C. As described above, the selective oxidation reaction of ammonia is promoted, and at the same time, other ammonia reactions and coal gasification gas reactions are effectively suppressed.

  In this embodiment, oxygen supplied from the air separation device 2 is used as oxygen for ammonia decomposition, but instead of oxygen, air is supplied directly to the ammonia decomposition treatment device 7 and oxygen in the air is used. You may make it do. The amount of oxygen at this time is also preferably 0.75 mol / mol or more and 15 mol / mol or less in a molar ratio with respect to ammonia, as described above.

  The purified gas (fuel gas) purified by the gas purification facility 4 is supplied to the combustor 9 of the gas turbine facility 8 and burns with the air supplied via the compressor 10 to drive the expansion turbine 11. Exhaust heat of the exhaust gas from the gas turbine facility 8 is recovered by the exhaust heat recovery boiler 12. As a result, steam is produced in the exhaust heat recovery boiler 12, and the steam turbine 13 is driven by the steam.

  As a result, the generator 14 is driven using the gas turbine facility 8 and the steam turbine 13 as a prime mover, and performs highly efficient power generation. The exhaust gas whose exhaust heat has been recovered by the exhaust heat recovery boiler 12 is exhausted from the chimney 16 to the environment through the exhaust gas denitration device 15.

The catalyst for dry ammonia decomposition process as described above, the 10-membered ring structure of the zeolite bets were used those obtained by supporting nickel as a carrier is that the basis of the findings based on the following experiment. In this experiment, the reaction characteristics of various prototype catalysts with different support components were examined for the purpose of searching for a highly active catalyst and grasping reaction conditions capable of suppressing carbon deposition.

<Experiment method>
1. Catalyst Preparation and Analysis Method Nickel (Ni) was selected as the active component of the catalyst to prepare a catalyst. Supports are alumina (Al ₂ O ₃ ), silica (SiO ₂ ) for reference, silica-alumina (SiO ₂ .Al ₂ O ₃ ), ZSM-5 zeolite (ZSM-5), beta zeolite (Beta) as examples. Y-type zeolite (Y) was used.

  The catalyst preparation procedure is shown in FIG. As shown in the figure, the dry carrier powder was added to an aqueous solution of nickel nitrate hexahydrate (special grade manufactured by Wako Pure Chemical Industries) and stirred sufficiently. Subsequently, evaporation to dryness was performed on a hot plate, and after evaporating the solvent, a powder was collected. The obtained powder was put into an electric furnace, heated in a dry air stream of silica gel at 5 ° C./min, fired at 500 ° C. for 5 hours, and allowed to cool naturally. The obtained catalyst was crushed after press molding and sized with a JIS sieve to 1 to 2 mm mesh.

  Table 1 shows a list of the prototype catalysts thus formed.

  The form of nickel could not be identified by X-ray analysis (XRD) due to the small amount of support, but it was supported in the form of metallic nickel, nickel oxide (NiO), nickel partially combined with the carrier, etc. Presumed to be.

  The amount of carbon deposited on the catalyst after the ammonia decomposition reaction was determined by a CHN analyzer. Specifically, about 2 mg of a sample was filled in a tin cell, and carbon dioxide produced by combustion at 975 ° C. with oxygen was measured by TCD, and the two measurements were averaged.

2. Ammonia decomposition experiment method Supply nitrogen (N ₂ ), hydrogen (H ₂ ), carbon monoxide (CO), carbon dioxide (CO ₂ ), oxygen (O ₂ ), and 2% NH ₃ / N ₂ from a cylinder to the mixer. Then, distilled water was sprayed from the spray nozzle to the mixer using a metering pump. The mixed gas was supplied to the reaction tube, and the reaction gas was analyzed. The pipe and the mixer are made of stainless steel. The mixer has a built-in quartz tube, the quartz tube is fixed with a sealant, and a glass bulb is filled inside. The reaction tube has a double tube structure of a heat resistant alloy outer tube and a quartz inner tube, and the inner tube is fixed with a sealant. In addition, a heat-resistant alloy sheath tube for inserting a thermocouple was attached to the central axis, and the axial temperature distribution of the catalyst layer was measured at three points with a K-type thermocouple. The quartz tube had an inner diameter of 16 mm, and the sheath tube had an outer diameter of 3.2 mm. Quartz wool was spread on a quartz plate, and the catalyst was filled at the highest temperature. The outer periphery of the sheath tube downstream from the eye plate was covered with a quartz tube. Teflon (registered trademark) was used as the sample tube. The piping, sample tube and mixer were heated to 140 ° C., and the reaction tube was heated in a muffle furnace. The gas flow rate was measured using a mass flow controller. The flow rate of distilled water was determined by measuring the weight loss per unit time of distilled water in the container.

The concentrations of ammonia (NH ₃ ), hydrogen cyanide (HCN), nitric oxide (NO), nitrogen dioxide (NO ₂ ) and dinitrogen monoxide (N ₂ O) in the gas were measured using a Fourier transform infrared spectrophotometer. The measurement was carried out with the gas cell held at 53 ° C. The concentrations of hydrogen (H ₂ ), methane (CH ₄ ) to butane (C ₄ H ₁₀ ), carbon monoxide (CO), carbon dioxide (CO ₂ ), nitrogen (N ₂ ) and oxygen (O ₂ ) After dehumidifying with calcium at room temperature, it was measured by micro gas chromatography.
Table 2 shows the standard experimental conditions.

The composition of the gas is to simulate the gas composition at the outlet of the desulfurization unit of a coal gasification combined power plant using a dry feed carbon dioxide-enriched air-blown entrained bed gasification furnace. ₂ / Fuel) was added at 0.008 mol / mol (approximately 8 mol / mol in terms of molar ratio to NH ₃ ). The experiment was performed under the conditions of a space velocity (SV) of 20000 h ⁻¹ and a pressure of 0.9 MPa.

The temperature / fuel supply program of this experiment is shown in FIG. As shown in the figure, the temperature of the catalyst layer was raised to 150 ° C. in a nitrogen (N ₂ ) stream and the temperature was stabilized, and then the fuel was supplied and held until the analytical value of the gas composition was stabilized.

Next, the temperature of the catalyst layer was raised to a predetermined temperature and kept at a constant temperature for 20 minutes, and the operation of acquiring data was repeated up to 600 ° C. every 50 ° C. After the measurement, the inlet gas concentration was measured, and the reaction tube was naturally cooled in a nitrogen (N ₂ ) stream. The conversion rate of ammonia (NH ₃ ) to nitrogen (N ₂ ) is determined from the decomposed ammonia (NH ₃ ), hydrogen cyanide (HCN), nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), and dioxide monoxide. The concentration obtained by subtracting nitrogen (N ₂ O) was calculated using the following formula (1). The production rate of hydrogen cyanide (HCN), nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), and dinitrogen monoxide (N ₂ O) accompanying the decomposition of ammonia (NH ₃ ) uses the following formula (2). Calculated.

CR (N ₂ ) = 100 × (C (NH ₃ in) −C (ΣXN)) / C (NH ₃ in)
... (1)
PR (Nx) = 100 × C (Nx) / C (NH ₃ in) (2)
CR (N ₂ ); conversion rate of NH ₃ to N ₂ [%]
PR (Nx); Nx generation rate [%]
Nx; HCN, NO, NO ₂ or N ₂ O
C (NH ₃ in); inlet NH ₃ molar concentration [mol%]
C (ΣXN); outlet total nitrogen-containing component molar concentration [mol%]
ΣXN = NH ₃ + HCN + NO + NO ₂ + N ₂ O
C (Nx); outlet Nx molarity [mol%]

Nx may be generated from N ₂ in the fuel in addition to NH ₃ , and CR (N ₂ ) becomes negative particularly under the condition that Nx is generated without decomposition of NH ₃ .

3. Experimental Results FIG. 4 shows the ammonia decomposition characteristics of each catalyst. As shown in the figure, the conversion rate of NH ₃ to N ₂ is 94% at the maximum value at 300 to 350 ° C. in the case of Ni / ZSN-5, and then Ni / Al ₂ O ₃ is 36% at 400 ° C. Ni / Y was 18% at 450 ° C., Ni / Beta was 17% at 300 ° C., and Ni / SiO ₂ · Al ₂ O ₃ was 13% at 450 ° C.

Ni / SiO ₂ had a catalyst outlet NH ₃ concentration of 35 ppm or more higher than the inlet at 500 ° C. or higher, and the calculated value of the conversion rate was −12% or lower due to the addition of N ₂ O and the like described later.

Although NO and NO ₂ was generated almost in both the catalyst, _{N 2} O and HCN were generated slightly. N ₂ O production characteristics are shown in FIG. As shown in the figure, N ₂ O was hardly produced at 450 ° C. or lower, but the production rate tended to increase at 500 ° C. or higher. The production rate was Ni / SiO ₂ .Al ₂ O ₃ <Ni / _ZSM-5 <becomes higher in the order of _{Ni / Y <Ni / Al 2} O 3 <Ni / SiO 2 <Ni / Beta.

Further, the generation characteristics of HCN are shown in FIG. As shown in the figure, the HCN production rate of each catalyst is low, and the production rate tends to increase gradually as the temperature rises. Ni / ZSM-5 <Ni / Beta <Ni / Y <Ni / SiO ₂ < _{Ni / SiO 2 · Al 2 O} 3 < was higher in the order of Ni / _Al 2 _{O 3.}

FIG. 7 shows the reaction / generation characteristics of CO and CO ₂ , and FIG. 8 shows the reaction / generation characteristics of H ₂ and CH ₄ . As shown in both figures, there is a catalyst in which the change of each concentration becomes large at a temperature exceeding 450 ° C., and the tendency thereof is Ni / SiO ₂ .Al ₂ O ₃ <Ni / ZSM-5 <Ni / Y <Ni / _{Al 2 O 3 <Ni / Beta} < was higher in the order of Ni / SiO _2. Incidentally, ethane _{(C 2 H} 6), ethylene _{(C 2 H} 4), propane _{(C 3 H} 8), propylene _{(C 3 H} 6), butane _{(i, n-C 4 H} 10) is not detected It was.

  From these results, it is estimated that the following reaction proceeded mainly in this experiment.

4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O (selective oxidation reaction) (3)
2H ₂ + O ₂ → 2H ₂ O (4)
2CO + O ₂ → 2CO ₂ (5)
2CO + 2H ₂ → CH ₄ + CO ₂ (methanation reaction) (6)
2CO → 2CO ₂ + C (Budard reaction) (7)
2NH ₃ + 2O ₂ → N ₂ O + 3H ₂ O (8)

For reference, alumina (Al ₂ O ₃ ), silica (SiO ₂ ) Ni-supported catalyst, and examples of silica-alumina (SiO ₂ .Al ₂ O ₃ ), ZSM-5 zeolite (ZSM-5), beta zeolite (Beta) Due to the performance of the Ni-supported catalyst of Y-type zeolite (Y), the reactions (4) and (5) proceed at 250 ° C. or higher and become a competitive reaction with the reaction (3). Reaction (3) (selective oxidative decomposition reaction of NH ₃ ) proceeds in the temperature range of 250 to 450 ° C., and O ₂ is consumed. At temperatures higher than that, reactions (4) and (5) are dominant, Reaction (3) stops. At temperatures exceeding 450 ° C., reactions (6) to (8) proceed in addition to reactions (4) and (5), reducing CO and H ₂ concentration, increasing CO ₂ concentration, carbon deposition on the catalyst and N ₂ O This causes an increase in concentration. In addition, since addition of O ₂ preferentially proceeds reaction (5) even at a temperature exceeding 450 ° C., reactions (6) and (7), that is, carbon precipitation and CH ₄ generation are suppressed until O ₂ disappears. It seems to be.

4). Summary As a result of the above, a zeolite-supported Ni catalyst comprising both SiO ₂ and Al ₂ O ₃ as main support components, and a silica-alumina Ni-supported catalyst (for example, SiO ₂ .Al ₂ O ₃ , ZSM- 5, Beta, Y-zeolite Ni-supported catalyst) and, as a reference, Al ₂ O ₃ Ni-supported catalyst showed selective catalytic oxidative decomposition activity of NH ₃ at 250-450 ° C. It is considered that the catalyst can suppress side reactions such as fuel consumption, carbon deposition, and CH ₄ · N ₂ O · HCN generation, and in particular, Ni / ZSM-5 has high NH ₃ decomposition activity and side reaction suppression capability. Became clear.

More specifically, when aiming at application to the selective catalytic oxidative decomposition method of NH ₃ which is being studied as a dry gas purification technology for coal gasification combined power generation, both SiO ₂ and Al ₂ O ₃ are the main constituents. The catalyst in which Ni is supported on the zeolite carrier (Ni-supported catalyst of SiO ₂ .Al ₂ O ₃ , ZSM-5, Beta, Y-type zeolite as an example) has NH ₃ selective oxidative decomposition activity, 450 ° C. Side reactions such as carbon precipitation can be greatly suppressed by reacting in the following, in particular, Ni / ZSM-5, Ni / Y and Ni / SiO ₂ .Al ₂ O ₃ have NH ₃ selective oxidative decomposition activity, and at the same time wide It became clear that side reactions such as carbon deposition can be suppressed in the temperature range. Among these, it has been clarified that Ni / ZSM-5 has a remarkable NH ₃ selective oxidative decomposition activity and can suppress side reactions such as carbon deposition in a wide temperature range.

As a result, as much as possible the degradation of the fuel gas such as a coal gasification gas when using 10-membered ring structure zeolite in a ZSM-5 carriers in transition metal catalysts where the nickel is supported is that the It was confirmed that the ammonia contained can be decomposed satisfactorily while being suppressed.

  In addition, although the case where the ammonia decomposition processing apparatus which concerns on embodiment was applied to the coal gasification gas power generation equipment was shown in the said embodiment, of course, it is not necessary to limit to this. In short, there is no particular limitation as long as it is a facility that involves a dry ammonia decomposition treatment of a gas containing ammonia together with a combustible compound containing carbon atoms. For example, it can be applied to a facility having a gasification furnace using biomass, heavy oil, municipal waste or the like as fuel instead of a coal gasification furnace, and the same effect can be obtained. Further, the purified gas (fuel gas) after purification can be supplied not only to the power generation facility but also to the fuel synthesis facility, and in this case, the same effect can be expected.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used in an industrial field where dry purification of fuel gas obtained at the time of combined gasification combined power generation is performed, for example.

DESCRIPTION OF SYMBOLS 1 Coal gasifier 4 Gas refinery equipment 7 Ammonia decomposition processing apparatus 8 Gas turbine equipment 12 Waste heat recovery boiler 13 Steam turbine 14 Generator

Claims (6)

In a dry ammonia decomposition method for purifying a fuel gas by adding oxygen to a gas containing ammonia together with a combustible compound containing carbon atoms, decomposing the ammonia by contacting the oxygen-added gas with a catalyst,
As the catalyst, a dry ammonia decomposition method using a catalyst in which ZSM-5, which is a constituent component of SiO ₂ and Al ₂ O ₃ and a 10-membered oxygen ring zeolite, is supported on a transition metal nickel. Processing method. The dry ammonia decomposition treatment method according to claim 1 ,
The dry ammonia decomposition method, wherein a reaction temperature when decomposing the ammonia is 200 ° C. to 450 ° C. In the dry ammonia decomposition treatment method according to claim 1 or 2 ,
The amount of oxygen added is 0.75 mol / mol or more and 15 mol / mol or less in molar ratio with respect to the ammonia. An oxygen addition means for adding oxygen to a gas containing ammonia together with a combustible compound containing carbon atoms;
A catalyst that decomposes ammonia in the gas by contacting the gas to which oxygen has been added by the oxygen addition means;
The catalyst is a catalyst that supports nickel , which is a transition metal , using ZSM-5, which is a zeolite having 10-membered ring oxygen and SiO ₂ and Al ₂ O ₃ as constituents, as a carrier. Processing equipment. A gasifier for generating gas;
The dry ammonia decomposition apparatus according to claim 4 , wherein ammonia in the gas generated in the gasification furnace is decomposed dry.
And a power generation means for generating power using the purified gas purified by the dry ammonia decomposition apparatus as a fuel. The power generation facility according to claim 5 ,
The gasifier is
A coal gasification furnace in which coal is pyrolyzed to produce coal gasification gas containing ammonia together with combustible components including carbon and hydrogen.

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