JP3388941B2 - Exhaust gas purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nitrogen oxides in exhaust gas.
(NOx), removes carbon monoxide (CO) with high efficiency
The present invention relates to a method for purifying exhaust gas that can be performed. [0002] 2. Description of the Related Art Removal of NOx contained in flue gas
The method is NH_ThreeCatalytic reduction method using urea as reducing agent
Has been widely put to practical use mainly in thermal power plants. As a catalyst
Activated vanadium, tungsten, and molybdenum
A titanium oxide-based catalyst is mainly used. [0003] SUMMARY OF THE INVENTION In recent years, NOx emission regulations have been
It is becoming increasingly severe, especially in metropolitan areas.
Regulations are being implemented, and power plants adjacent to urban areas
When expanding power generation equipment in response to growing power demand,
High efficiency denitration is required. In addition, emissions from power plants
Regulations on the emission of carbon monoxide are also becoming stricter. Obedience
Next denitration method is NH _ThreeIs a catalytic reduction method using
4NO + 4NH_Three+ O_Two→ 4N_Two+ 6H_TwoIn the reaction formula of O
Therefore, NOx becomes N on the catalyst._TwoIs decomposed into This reaction formula
From the viewpoint, it is theoretically possible to make NH4 equimolar to NOx._ThreeWith
If added, NOx can be removed 100%. Only
In practice, NH_ThreeAnd NOx completely uniform
It is impossible to mix, and to perform highly efficient denitration
Has NH_ThreeMust be added in excess of NOx. So
Unreacted NH_ThreeHas the disadvantage that
there were. Heretofore, the inventors have determined that unreacted NH_ThreeExhaustion
Ammonia decomposition catalyst has been developed to prevent the
-127126, Japanese Patent Application No. 6-70486, etc.)
A finishing denitration catalyst is installed at the back to perform high-efficiency denitration.
Seth was proposed (Japanese Patent Application No. 6-176494). But,
Ammonia decomposition when carbon monoxide coexists in exhaust gas
NH of catalyst_ThreeFailure to change decomposition rate and nitrogen selectivity
Occurred. [0005] In view of the state of the art, the present invention is based on the prior art.
Eliminate the disadvantages and unreacted NH_ThreeEmissions to the atmosphere as much as possible
To perform high-efficiency denitration.
To provide a method for purifying exhaust gas that can also remove sulfur
It is. [0006] SUMMARY OF THE INVENTION,Elemental oxides,
Exhaust gas containing carbon monoxide in a reactor filled with catalyst
Lead and contact with nitrogen oxides using ammonia as a reducing agent
In the upper stage of the ammonia addition device
ToPlatinum as an active metal and / or a porous heat-resistant carrier
0.001 to 10 wt% of palladium supportedCarbon monoxide
The element removal catalyst layer is located upstream of the lower side of the ammonia addition device.
The first denitration catalyst layer from the side and ammonia
Has the function of oxidatively decomposing into nitrogen oxidesDehydrated
(1.0 ± 0.6) R _Two O ・ [aM _Two O _Three ・ B
Al _Two O _Three ] ・ CMeO ・ ySiO _Two (R: alkali gold
Genus ion and / or hydrogen ion, M: group VIII of the periodic table
Element, rare earth element, titanium, vanadium, chromium, nio
1 selected from the group consisting of copper, antimony and gallium
Or more elements, Me: alkaline earth metal element, a + b =
1, a ≧ 0, b ≧ 0, c ≧ 0, y / c> 12, y> 1
It has the chemical formula of 2) and is described in the detailed description of the invention.
Crystalline silicon having an X-ray diffraction pattern shown in Table 1 of FIG.
Kate as a carrier and platinum and / or para as an active metal
Contains indiumThe ammonia decomposition catalyst layer is further
A second denitration catalyst layer is installed in the downstream,
Ammonia added from the inlet exhaust gas
Purification of exhaust gas characterized by adding more than reaction equivalent
OneBy lawis there. [0007] [Table 1]                VS: Very strong                   S: Strong                   M: Intermediate                   W: weak                 (X-ray source: Cu) [0008] Hereinafter, one embodiment of the present invention will be described with reference to FIG.
Clarify the effect. NH _ThreeOn the upper side of the addition device 2
A carbon monoxide removal catalyst layer 1 is installed, and the catalyst is burned to produce a monoacid.
Burns and removes carbonized carbon. NH_ThreeOn the lower side of the addition device 2
The first denitration catalyst layer 3 is supplied with NH 3_ThreeCracking catalyst layer 4
Further, a second denitration catalyst layer 5 is installed in the subsequent stream,
(1) A reaction equivalent or more to NOx upstream of the denitration catalyst layer 3
NH_ThreeTo NH_ThreeThe first denitration catalyst is added from the addition device 2
The denitration of 80% or more is performed in the layer 3 and the first denitration catalyst layer 3
Unreacted NH flowing out_ThreeTo NH_ThreeDecomposition by the decomposition catalyst layer 4
NOx, NH at the inlet of the second denitration catalyst layer downstream_ThreeDark
The NOx at the outlet of the second denitration catalyst layer 5 was adjusted to 0.
1 ppm or less, NH_ThreeTo a level of 5 ppm or less. Up
V and V are applied to the first and second denitration catalyst layers 3 and 5 downstream and downstream, respectively.
TiO containing W, Mo, etc. as active ingredients_TwoConventional practical use of the system
The known catalyst can be used. In the method of the present invention, carbon monoxide is combusted by a catalyst.
NH to burn off_ThreeChanges in the performance of cracking catalysts
And no harmful carbon monoxide emissions
You can do it. In the above embodiment of the present invention, NH_ThreeDisassembly
As the catalyst used for the medium layer, select nitrogen as defined below
It is preferable that the rate% is 60% or more. [0011] (Equation 1) Nitrogen selectivity (%) = [1- ｛NOx at ammonia decomposition catalyst outlet (ppm)                   -NOx (ppm) at the inlet of ammonia decomposition catalyst /                   ｛Ammonia decomposition catalyst inlet NH_Three(Ppm)                   -Ammonia decomposition catalyst outlet NH_Three(Ppm)｝] That is, the nitrogen selection of the ammonia decomposition catalyst as defined above
If the selectivity is small, NH _ThreeNH at the outlet of the cracking catalyst layer_Three> NO
The operating range of the plant that can be controlled to x is narrow
Control over a wide range of process gas volumes and temperature conditions.
Nitrogen selectivity should be at least 60% or less.
It is preferably above. NH having the above nitrogen selectivity_ThreeCracking catalyst
As (1.0 ± 0.6) R_Two
O ・ [aM_TwoO_Three・ BAl_TwoO_Three] ・ CMeO ・ ySi
O_Two(R: alkali metal ion and / or hydrogen ion,
M: Group VIII element of the periodic table, rare earth element, titanium, banana
From zium, chromium, niobium, antimony and gallium
At least one element selected from the group consisting of: Me: alkaline earth
A class metal element, a + b = 1, a ≧ 0, b ≧ 0, c ≧ 0, y
/ C> 12, y> 12) and the above Table 1
Crystalline silicate having X-ray diffraction pattern shown in
And platinum and / or palladium as active metals
Are preferred. [0013] Also, it is installed on the upper stage in the ammonia adding apparatus.
Carbon monoxide removal catalyst is a porous heat-resistant carrier such as alumina
Containing platinum or palladium as an active metal
Medium is preferred. Γ-Al as a porous heat-resistant carrier_TwoO
_Three, TiO_Two, SiO_Two, ZrO_Two, Fe_TwoO_Three, Si
O_Two・ Al_TwoO_ThreeEtc. can be used and carried
The amount of Pt and / or Pd is 0.001 to 10 wt%.
A range is preferred. Combustion of carbon monoxide by the carbon monoxide removal catalyst layer
Exhaust gas containing the removed nitrogen oxides contains excess NH_ThreeTo N
H_ThreeSupplied by the addition device and denitrated by the first denitration catalyst layer
NOx: 0 to 10 ppm, NH_Three: 10 to 30 ppm
And this exhaust gas is NH_ThreeNH in the cracking catalyst layer_ThreeIs reduced
NOx, NH_ThreeThe concentration is adjusted and the second denitration catalyst layer
NOx concentration in exhaust gas: 0.1 ppm or less, NH_ThreeDark
Degree: 5 ppm or less. [0015] The following examples further illustrate the method of the present invention.
Explain physically. (Example 1) (Preparation of denitration catalyst): Titania (TiO_Two) Pentic acid as carrier
Vanadium (V_TwoO_Five4% by weight, tungsten trioxide
Ten (WO_Three) Was supported at 8 wt%.
3 mm pitch, 0.5 mm wall thickness in a grid-like honeycomb shape
The catalyst was molded and used as a denitration catalyst 1. (NH_ThreePreparation of decomposition catalyst): Water glass No. 1
(SiO_Two: 30%): 5616 g to water: 5429 g
After dissolution, this solution was designated as solution A. On the other hand, water: 4175
g of aluminum sulfate: 718.9 g, ferric chloride: 1
10 g, calcium acetate: 47.2 g, sodium chloride
262 g and concentrated hydrochloric acid: 2020 g
This solution was designated as solution B. Solution A and Solution B
And a precipitate is formed, sufficiently stirred, and pH = 8.
A slurry of 0 was obtained. 20 liters of this slurry
Charged in a clave and added tetrapropyl ammonium
Add 500 g of bromide, and add water at 160 ° C for 72 hours.
Perform thermal synthesis, wash with water, dry after synthesis, and further 500
C. for 3 hours to obtain crystalline silicate 1. This result
Crystalline silicate 1 is in the molar ratio of oxides (water of crystallization is omitted)
0.5Na_TwoO ・ 0.5H_TwoO · [0.8Al_TwoO_Three・
0.2Fe _TwoO_Three・ 0.25CaO] ・ 25SiO_Twoof
It is represented by the composition formula, and the crystal structure is shown in Table 1 by X-ray diffraction.
It was shown. The above crystalline silicate 1 is 4N
NH_FourThe mixture was stirred for 3 hours at 40 ° C._FourIo
Exchange was carried out. Wash after ion exchange at 100 ℃, 2
After drying for 4 hours, baking for 3 hours at 400 ° C.
Crystalline silicate 1 was obtained. This H-type crystalline silicate 1 has platinum chloride
Impregnated with an aqueous acid or palladium nitrate solution and evaporated to dryness
Thereafter, the mixture was calcined at 500 ° C. for 3 hours to obtain a powder catalyst. Obtained
Powder: Aluminazo as binder for 100 g
3 g, silica sol: 55 g (SiO_Two： 20wt
%) And water: add 200 g to make a slurry,
Monolith substrate for grids (grating per 30 cell square inch)
Wash coat), 200g per substrate surface area
/ M^TwoIn the amount of coating. The resulting catalyst is converted to NH_ThreeMinute
Catalysts 1 to 4 were used. The properties are shown in Table 2 below. [0019] [Table 2] The above NH_ThreeIn the method for preparing the cracking catalyst, the salt
Cobalt chloride: 112 g instead of ferric chloride, titanium chloride
: 105 g, vanadium chloride: 10 g, chromium chloride:
107 g, niobium chloride: 135 g, antimony chloride: 1
55g, gallium chloride: 119g
H-type crystalline silicates 2, 3, 4, 5,
6, 7 and 8 were prepared, and each of these H-type crystalline silicates was prepared.
Operation similar to the above preparation method using chloroplatinic acid aqueous solution
The platinum is supported on each H-type crystalline silicate by
Operate in the same manner as in
200g / m per substrate surface area^TwoNo
The amount supported. The resulting catalyst is converted to NH_ThreeDecomposition catalyst 5-1
It was set to 1. The properties are shown in Table 3 below. [0021] [Table 3] (Preparation of catalyst for removing carbon monoxide) γ-aluminum
(Γ-Al_TwoO_Three) Platinum solution of chloroplatinic acid solution as carrier
And supported by a 3 wt% impregnation method, dried at 100 ° C.,
Powder catalyst calcined at 500 ° C. for 5 hours: For 100 g
And silica sol: 55 g (SiO 2_Two: 2
0 wt%) and water: 200 g to form a slurry.
Monolith substrate for gelite (per 30 cells square inch
Wash-coated in a lattice)
50g / m^TwoWas carried. Monoxide
This was designated as carbon removal catalyst 1. (Denitration reaction test) 40 mm x 50 mm x 5
One 0 mmL of the carbon monoxide removal catalyst 1 was 40 mm
1 x 50 mm x 400 mmL denitration catalyst, 40 m
m × 50 mm × 150 mmL of the NH_ThreeCracking catalyst 1
And the three denitration catalysts are arranged in series.
The test was performed under the following conditions. Run results of Run1-11
Is shown in Table 5 below. [0024] [Table 4] (Comparative Example 1) In the system of Run 1 of Example 1,
(= Ru) in which the catalyst for removing carbon monoxide was omitted
Table 5 also shows the evaluation results of n12). From the results shown in Table 5, the catalyst for removing carbon monoxide was used.
At the outlet of the second stage denitration catalyst in Runs 1 to 11
Are NOx <0.1 ppm, NH_Three<5 ppm
On the other hand, Run 1 omitting the carbon monoxide removal catalyst
In 2, NH_ThreeCracking catalyst outlet NH_ThreeThe concentration is reduced to NH
_ThreeSince the concentration is lower than the NOx concentration, the second stage denitration catalyst outlet
NOx> 0.1 ppm and the target can be met
I didn't come. [0027] [Table 5] As a carrier of the carbon monoxide removal catalyst,
γ-Al_TwoO_ThreeInstead of TiO_Two, SiO_Two, ZrO_Two,
Fe_TwoO_Three, SiO_Two・ Al_TwoO_ThreeUsing the same
The effect was obtained. [0029] According to the method for purifying exhaust gas of the present invention,
NH as base agent_ThreeMaintaining low levels of emissions
Nitrogen oxide and nitric oxide can be removed with high efficiency.

[Brief description of the drawings] FIG. 1 is an explanatory view of a method for purifying exhaust gas of the present invention.

────────────────────────────────────────────────── ⁷ Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B01J 29/068 ZAB B01D 53/36 E (56) References JP-A-52-54670 (JP, A) JP-A-51-63363 (JP, A) JP-A-51-13370 (JP, A) JP-A-4-118028 (JP, A) JP-A-63-87521 (JP, A) JP-A-2-293022 (JP, A) JP-A-51-84771 (JP, A) JP-A-6-327943 (JP, A) JP-A-56-108516 (JP, A) JP-A-53-132465 (JP, A) JP-A-53-108065 (JP, A) JP, A) JP-A-53-102866 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/86 B01J 21/00-38/74

Claims (1)

(57) [Claim 1] An exhaust gas containing nitrogen oxides and carbon monoxide is led to a reactor filled with a catalyst, and the nitrogen oxides are removed catalytically using ammonia as a reducing agent. In the method,
In the upper stage of the ammonia addition device ,
Platinum and / or palladium as a reactive metal
A carbon monoxide removal catalyst layer supporting 10 wt%, a first denitration catalyst layer from the upstream side on the lower side of the ammonia addition device,
The dewatered state having the function of oxidatively decomposing ammonia into nitrogen and nitrogen oxides is added to the subsequent stream (1.0 ± 0.
6) R ₂ O · _{[aM 2 O 3 · bAl 2 O} 3 ] · CMeO
• ySiO ₂ (R: alkali metal ion and / or hydrogen
Ion, M: Group VIII element of the periodic table, rare earth element, titanium
, Vanadium, chromium, niobium, antimony and gully
One or more elements selected from the group consisting of
Lucari earth metal element, a + b = 1, a ≧ 0, b ≧ 0, c
≧ 0, y / c> 12, y> 12), and
X-ray diffraction shown in Table 1 in the detailed description of the invention
Activated gold using crystalline silicate with pattern as carrier
An ammonia decomposition catalyst layer containing platinum and / or palladium as a genus, and a second denitration catalyst layer provided downstream thereof, and ammonia added from an ammonia addition device is supplied with nitrogen oxides in the inlet exhaust gas. A method for purifying exhaust gas, characterized in that it is added in an amount equal to or more than the reaction equivalent of the above.