U.S. patent application number 14/453387 was filed with the patent office on 2014-11-27 for method for regeneration of exhaust gas treatment catalyst, and exhaust gas treatment cataylst produced using the method.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Masanori Demoto, Masashi Kiyosawa, Yoshiaki Obayashi.
Application Number | 20140349838 14/453387 |
Document ID | / |
Family ID | 45066469 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140349838 |
Kind Code |
A1 |
Obayashi; Yoshiaki ; et
al. |
November 27, 2014 |
METHOD FOR REGENERATION OF EXHAUST GAS TREATMENT CATALYST, AND
EXHAUST GAS TREATMENT CATAYLST PRODUCED USING THE METHOD
Abstract
A regenerated exhaust gas treatment catalyst regenerated by: a
used catalyst coarse grinding step (S1) for coarsely grinding a
used exhaust gas treatment catalyst; a separation step (S2)
separating a coarsely ground material into coarse pieces and a fine
powder; a used catalyst fine grinding step (S3); steps (S4) to (S7)
for kneading the fine powder together with other raw materials,
molding a kneaded material, and drying and burning a molded
material to produce a base material; a fresh catalyst grinding step
(S8); a slurry formation step (S9); a slurry coating step (S10)
coating the surface of the base material with the slurry solution;
and a coating drying step (S11) and a coating burning step (S12)
for drying the base material that has been coated with the slurry
solution and burning the base material at a temperature higher than
that employed in the production of the exhaust gas treatment
catalyst.
Inventors: |
Obayashi; Yoshiaki; (Tokyo,
JP) ; Kiyosawa; Masashi; (Tokyo, JP) ; Demoto;
Masanori; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
45066469 |
Appl. No.: |
14/453387 |
Filed: |
August 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13387519 |
Apr 17, 2012 |
8835340 |
|
|
PCT/JP2011/051690 |
Jan 28, 2011 |
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14453387 |
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Current U.S.
Class: |
502/21 ;
502/312 |
Current CPC
Class: |
B01D 2251/2062 20130101;
B01D 2255/20707 20130101; B01J 23/92 20130101; B01J 37/0215
20130101; B01J 37/08 20130101; B01J 35/04 20130101; B01D 2255/9202
20130101; B01J 37/0009 20130101; B01J 37/06 20130101; B01J 23/30
20130101; B01J 21/063 20130101; B01J 35/023 20130101; B01J 37/0036
20130101; B01D 53/9418 20130101 |
Class at
Publication: |
502/21 ;
502/312 |
International
Class: |
B01J 23/92 20060101
B01J023/92 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2010 |
JP |
2010-126513 |
Claims
1. An exhaust gas treatment catalyst regenerated by a method of
regenerating an exhaust gas treatment catalyst having ash adhering
to a surface thereof, the exhaust gas treatment catalyst
regenerated by performing: a used catalyst crushing step of
crushing the exhaust gas treatment catalyst that has been used; a
separating step of separating the crushed exhaust gas treatment
catalyst into coarse pieces having a size exceeding a threshold
size S and fine particles having a size not larger than the
threshold size S; a used catalyst pulverizing step of pulverizing
the separated coarse pieces into a fine powder; a molding step of
molding the pulverized fine powder as a raw material into an
exhaust gas treatment catalyst; a precursor calcining step of
calcining a molded precursor of the exhaust gas treatment catalyst;
a newly-made catalyst crushing step of crushing the exhaust gas
treatment catalyst that has been newly made; a slurrying step of
slurrying the crushed newly-made exhaust gas treatment catalyst; a
slurry coating step of coating a surface of a base obtained by the
calcination in the precursor calcining step with the slurry liquid;
and a coating calcining step of calcining the base coated with the
slurry liquid at a higher temperature than a calcination
temperature during production of the crushed newly-made exhaust gas
treatment catalyst, wherein the threshold size S has a value not
smaller than 0.105 mm.
2. The exhaust gas treatment catalyst according to claim 1, wherein
the coating calcining step is a calcining step at a higher
temperature by 25.degree. C. or above than the calcination
temperature during the production of the crushed newly-made exhaust
gas treatment catalyst.
3. The exhaust gas treatment catalyst according to claim 2, wherein
the coating calcining step is a calcining step at a temperature of
700.degree. C. or less.
4. The exhaust gas treatment catalyst according to claim 1, wherein
the crushed and slurried newly-made exhaust gas treatment catalyst
has an average particle diameter of 3 to 8 .mu.m.
5. The exhaust gas treatment catalyst according to claim 1, wherein
a main raw material of the exhaust gas treatment catalyst is
titanium oxide.
6. The exhaust gas treatment catalyst according to claim 5, wherein
the exhaust gas treatment catalyst is used to treat exhaust gas
from a burned coal.
7. The exhaust gas treatment catalyst according to claim 6, wherein
the exhaust gas treatment catalyst is used to treat nitrogen oxide
in the exhaust gas.
8. The exhaust gas treatment catalyst according to claim 1, wherein
the used catalyst crushing step is a step in which the exhaust gas
treatment catalyst that has been used is crushed such that 70 to 95
wt % of the whole exhaust gas treatment catalyst that has been used
becomes the coarse pieces having a size exceeding the threshold
size S.
9. The exhaust gas treatment catalyst according to claim 8, wherein
the threshold size S has a value not larger than 1.0 mm.
10. The exhaust gas treatment catalyst according to claim 1,
wherein the used catalyst pulverizing step is a step in which the
coarse pieces are pulverized such that the fine powder has an
average particle diameter not larger than 0.1 mm.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 13/387,519 filed Apr. 17, 2012, which is a 371 of
PCT/JP2011/0516910 filed Jan. 28, 2011.
TECHNICAL FIELD
[0002] The present invention relates to a method of regenerating an
exhaust gas treatment catalyst having ash adhering to a surface
thereof and an exhaust gas treatment catalyst obtained by the
method. The present invention is extremely effective particularly
when employed to regenerate an exhaust gas treatment catalyst,
mainly containing titanium oxide, for removing nitrogen oxide in
exhaust gas from burned coal.
BACKGROUND ART
[0003] A discharge line for exhaust gas from equipment, such as,
for example, a coal-fired boiler or the like, in which coal is
burnt is provided with an exhaust gas treatment catalyst for
treating nitrogen oxide (NO.sub.x) in the exhaust gas. The exhaust
gas treatment catalyst is obtained by the following process:
titanium oxide (TiO.sub.2) as a main component, and further
tungsten oxide (WO.sub.3), vanadium oxide (V.sub.2O.sub.5), and the
like are kneaded together with a binder, molded into a honeycomb
shape so as to have multiple holes, and calcined. A reducing agent
such as ammonia (NH.sub.3) is flowed into the holes together with
the exhaust gas to bring the nitrogen oxide in the exhaust gas and
the reducing agent into contact with the wall surfaces of the
holes. This enables the decomposition and removal of the nitrogen
oxide.
[0004] While such an exhaust gas treatment catalyst is being used,
ash (fly ash) generated by burning coal is continuously flowed into
the holes together with exhaust gas. Thus, components such as
calcium (Ca) in the fly ash gradually adhere (to a thickness of
several tens .mu.m) on the inner wall surfaces of the holes. Such
components inhibit the contact reaction between the nitrogen oxide
and the reducing agent on the catalyst surface. Additionally, the
fly ash itself is partially deposited inside the holes, and
gradually makes it hard for exhaust gas to flow into the holes.
Eventually, the fly ash completely blocks and clogs the holes,
accordingly lowering the denitration performance.
[0005] Against this background, the exhaust gas treatment catalyst
used for a predetermined period is regenerated as described in, for
example, Patent Document 1. Specifically, an exhaust gas treatment
catalyst is crushed such that 70 to 95 wt % of the whole exhaust
gas treatment catalyst becomes coarse pieces having a size
exceeding a threshold size S (any value in a range of 0.105 mm to
1.0 mm) (crushing step). Fragments thus obtained by crushing the
exhaust gas treatment catalyst are separated into the coarse pieces
having a size exceeding the threshold size S and fine particles
having a size not larger than the threshold size S (separating
step). The separated coarse pieces are pulverized into such a fine
powder that has an average particle diameter not larger than 0.1 mm
(pulverizing step). The fine powder is kneaded together with other
raw materials and molded into an exhaust gas treatment catalyst
(kneading step and molding step). The molded precursor is dried and
calcined (around 500.degree. C.) (drying step and calcining step).
Thus, a regenerated exhaust gas treatment catalyst is obtained.
CITATION LIST
Patent Literature
[0006] [Patent Literature 1] Japanese Patent Application
Publication No. 2009-226388 [0007] [Patent Literature 2] Japanese
Patent Application Publication No. Hei 9-108573 [0008] [Patent
Literature 3] Japanese Patent Application Publication No. Sho
57-180433
SUMMARY OF INVENTION
Technical Problem
[0009] The regeneration method described in Patent Document 1 can
produce the exhaust gas treatment catalyst not bringing about a
particular problem in many cases. However, it has been found out
that, depending on the poisoned state and the like of the exhaust
gas treatment catalyst used for a predetermined period, the
denitration performance is not sufficiently recovered in some
occasion.
[0010] As the measure, it is conceivable as described in, for
example, Patent Document 2 and the like above that the exhaust gas
treatment catalyst not having a sufficiently recovered denitration
performance is coated with particulate components having a particle
size distribution with two peaks between 0.1 .mu.m and 50 .mu.m and
also having a denitration performance, such that the coating can be
gradually worn off from the surface. Thereby, a sufficient
denitration performance can be constantly demonstrated over a long
period (approximately around 15,000 hours). Nonetheless, recently,
the continuous use over a longer period (approximately 20,000 to
30,000 hours) has been strongly demanded. It has been difficult for
the measure to meet such a demand.
[0011] In view of such circumstances, an object of the present
invention is to provide a method of regenerating an exhaust gas
treatment catalyst and an exhaust gas treatment catalyst obtained
by the method, the exhaust gas treatment catalyst being
continuously usable over a long period (approximately 20,000 to
30,000 hours), even when regenerated by first crushing, then
re-molding, and calcining with a surface thereof being coated.
Solution to Problem
[0012] To solve the above-described problem, a method of
regenerating an exhaust gas treatment catalyst according to a first
invention is a method of regenerating an exhaust gas treatment
catalyst having ash adhering to a surface thereof, characterized in
that the method comprises:
[0013] a used catalyst crushing step of crushing the exhaust gas
treatment catalyst that has been used;
[0014] a separating step of separating the crushed exhaust gas
treatment catalyst into coarse pieces having a size exceeding a
threshold size S and fine particles having a size not larger than
the threshold size S;
[0015] a used catalyst pulverizing step of pulverizing the
separated coarse pieces into a fine powder;
[0016] a molding step of molding the pulverized fine powder as a
raw material into an exhaust gas treatment catalyst;
[0017] a precursor calcining step of calcining a molded precursor
of the exhaust gas treatment catalyst;
[0018] a newly-made catalyst crushing step of crushing the exhaust
gas treatment catalyst that has been newly made;
[0019] a slurrying step of slurrying the crushed newly-made exhaust
gas treatment catalyst;
[0020] a slurry coating step of coating a surface of a base
obtained by the calcination in the precursor calcining step with
the slurry liquid; and
[0021] a coating calcining step of calcining the base coated with
the slurry liquid at a higher temperature than a calcination
temperature during production of the crushed newly-made exhaust gas
treatment catalyst, and
[0022] the threshold size S has a value not smaller than 0.105
mm.
[0023] A method of regenerating an exhaust gas treatment catalyst
according to a second invention is the method of regenerating an
exhaust gas treatment catalyst according to the first invention,
characterized in that
[0024] the crushing step is a calcining step at a higher
temperature by 25.degree. C. or above than the calcination
temperature during the production of the crushed newly-made exhaust
gas treatment catalyst.
[0025] A method of regenerating an exhaust gas treatment catalyst
according to a third invention is the method of regenerating an
exhaust gas treatment catalyst according to the second invention,
characterized in that
[0026] the coating calcining step is a calcining step at a
temperature of 700.degree. C. or less.
[0027] A method of regenerating an exhaust gas treatment catalyst
according to a fourth invention is the method of regenerating an
exhaust gas treatment catalyst according to any one of the first to
the third inventions, characterized in that
[0028] the crushed and slurried newly-made exhaust gas treatment
catalyst has an average particle diameter of 3 to 8 .mu.m.
[0029] A method of regenerating an exhaust gas treatment catalyst
according to a fifth invention is the method of regenerating an
exhaust gas treatment catalyst according to the first to the fourth
inventions, characterized in that
[0030] a main raw material of the exhaust gas treatment catalyst is
titanium oxide.
[0031] A method of regenerating an exhaust gas treatment catalyst
according to a sixth invention is the method of regenerating an
exhaust gas treatment catalyst according to the fifth invention,
characterized in that
[0032] the exhaust gas treatment catalyst is used to treat exhaust
gas from a burned coal.
[0033] A method of regenerating an exhaust gas treatment catalyst
according to a seventh invention is the method of regenerating an
exhaust gas treatment catalyst according to the sixth invention,
characterized in that
[0034] the exhaust gas treatment catalyst is used to treat nitrogen
oxide in the exhaust gas.
[0035] A method of regenerating an exhaust gas treatment catalyst
according to an eighth invention is the method of regenerating an
exhaust gas treatment catalyst according to the first to the
seventh inventions, characterized in that
[0036] the used catalyst crushing step is a step in which the
exhaust gas treatment catalyst that has been used is crushed such
that 70 to 95 wt % of the whole exhaust gas treatment catalyst that
has been used becomes the coarse pieces having a size exceeding the
threshold size S.
[0037] A method of regenerating an exhaust gas treatment catalyst
according to a ninth invention is the method of regenerating an
exhaust gas treatment catalyst according to the eighth invention,
characterized in that
[0038] the threshold size S has a value not larger than 1.0 mm.
[0039] A method of regenerating an exhaust gas treatment catalyst
according to a tenth invention is the method of regenerating an
exhaust gas treatment catalyst according to the first to the ninth
inventions, characterized in that
[0040] the used catalyst pulverizing step is a step in which the
coarse pieces are pulverized such that the fine powder has an
average particle diameter not larger than 0.1 mm.
[0041] Moreover, to solve the above-described problem, an exhaust
gas treatment catalyst according to an eleventh invention is an
exhaust gas treatment catalyst characterized by being regenerated
by the method of regenerating an exhaust gas treatment catalyst
according to any one of the first to the tenth inventions.
Advantageous Effects of Invention
[0042] In the method of regenerating an exhaust gas treatment
catalyst according to the present invention, a surface of a base is
coated with a slurry liquid of a crushed newly-made exhaust gas
treatment catalyst, and calcined at a higher temperature than that
during production of the crushed newly-made exhaust gas treatment
catalyst. This can surely increase the degree of sintering a
surface of a regenerated exhaust gas treatment catalyst. Hence, an
exhaust gas treatment catalyst according to the present invention
has a high-strength surface and is capable of demonstrating a
sufficient wear resistance while keeping a sufficient denitration
performance. Thus, the exhaust gas treatment catalyst according to
the present invention is continuously usable over a long period
(approximately 20,000 to 30,000 hours).
BRIEF DESCRIPTION OF DRAWINGS
[0043] FIG. 1 is a schematic configuration diagram of an exhaust
gas treatment catalyst used in a main embodiment of a method of
regenerating an exhaust gas treatment catalyst according to the
present invention.
[0044] FIG. 2 is a flowchart showing the procedure of the main
embodiment of the method of regenerating an exhaust gas treatment
catalyst according to the present invention.
[0045] FIG. 3 is a graph for obtaining a relationship between a
calcination temperature difference and a wear rate in Test Example
2 for the method of regenerating an exhaust gas treatment catalyst
according to the present invention.
DESCRIPTION OF EMBODIMENTS
[0046] A method of regenerating an exhaust gas treatment catalyst
according to the present invention and an exhaust gas treatment
catalyst obtained by the method will be described on the basis of
the drawings. However, the present invention is not limited only to
embodiments described below.
Main Embodiment
[0047] A main embodiment of a method of regenerating an exhaust gas
treatment catalyst according to the present invention and an
exhaust gas treatment catalyst obtained by the method will be
described on the basis of FIGS. 1 and 2.
[0048] As shown in FIG. 1, an exhaust gas treatment catalyst 10
according to the present embodiment is obtained by the following
process: titanium oxide (TiO.sub.2) as a main component and further
tungsten oxide (WO.sub.3), vanadium oxide (V.sub.2O.sub.5), and the
like are kneaded together with a binder, molded into a honeycomb
shape so as to have multiple holes 10a, and calcined.
[0049] Such an exhaust gas treatment catalyst 10 is installed in a
discharge line for exhaust gas from equipment, such as a coal-fired
boiler, for burning coal. A reducing agent such as ammonia
(NH.sub.3) is flowed into the holes 10a together with the exhaust
gas to bring the nitrogen oxide (NO.sub.x) in the exhaust gas and
the reducing agent into contact with the wall surfaces of the holes
10a. This enables the decomposition and removal of the nitrogen
oxide.
[0050] While the exhaust gas treatment catalyst 10 is being used,
ash (fly ash) generated by burning coal is continuously flowed into
the holes 10a together with exhaust gas. Thus, components such as
calcium (Ca) in the fly ash gradually adhere (to a thickness of
several tens .mu.m) on the inner wall surfaces of the holes 10a.
The components inhibit the contact reaction between the nitrogen
oxide and the reducing agent on the surfaces of the holes 10a.
Additionally, the fly ash itself is partially deposited inside the
holes 10a, and gradually makes it hard for exhaust gas to flow into
the holes. Eventually, the fly ash completely blocks and clogs the
holes, accordingly lowering the denitration performance. For this
reason, after a predetermined period of use, the catalyst is taken
out from the exhaust gas line and transferred to a regeneration
treatment facility.
[0051] Then, a used exhaust gas treatment catalyst 11 transferred
to the regeneration treatment facility is introduced into a
crushing machine, e.g., a crusher, without a washing treatment step
using a washing liquid such as water. The catalyst is crushed such
that 70 to 95 wt % of the whole exhaust gas treatment catalyst 11
becomes coarse pieces 12 having a size exceeding a threshold size S
(any value in a range of 0.105 mm to 1.0 mm) (in FIG. 2, used
catalyst crushing step S1).
[0052] The fragments obtained by crushing the exhaust gas treatment
catalyst 11 are supplied onto a sieve having a mesh size of the
threshold size S. Then, the fragments are separated into the coarse
pieces 12 having a size exceeding the threshold size S and fine
particles 13 having a size not larger than the threshold size S (in
FIG. 2, separating step S2).
[0053] The fine particles 13 having passed through the meshes of
the sieve are subjected to a disposal treatment. Meanwhile, the
coarse pieces 12 left on the meshes of the sieve are introduced
into a pulverizing machine, e.g., a hammermill, and pulverized to a
fine powder having an average particle diameter not larger than 0.1
mm (preferably, 70 .mu.m) (in FIG. 2, used catalyst pulverizing
step S3).
[0054] Then, the fine powder is supplied as a raw material together
with other ingredients such as a binder and water into a kneading
machine, e.g., a kneader, and uniformly kneaded (in FIG. 2,
kneading step S4). The kneaded product is supplied into an extruder
and molded into a honeycomb shape (in FIG. 2, molding step S5).
This molded precursor is naturally dried and subsequently dried
with hot air (100.degree. C.) or the like (in FIG. 2, precursor
drying step S6). Thereafter, the dried precursor is calcined in a
calcining furnace (around 500.degree. C.) (in FIG. 2, precursor
calcining step S7). Thus, a base 14 of a regenerated exhaust gas
treatment catalyst is obtained.
[0055] On the other hand, a newly-made exhaust gas treatment
catalyst 15 similar to the exhaust gas treatment catalyst 10 is
prepared, and introduced into and crushed with a crushing machine,
e.g., a crusher (in FIG. 2, newly-made catalyst crushing step S8).
The fragments obtained by crushing the newly-made exhaust gas
treatment catalyst 15 are introduced into a ball mill together with
water, and slurried while further crushed (to an average particle
diameter of approximately around 3 to 8 .mu.m) (in FIG. 2,
slurrying step S9).
[0056] Next, the base 14 is immersed into a slurry liquid 16
obtained above, and the surface of the base 14 is coated with the
slurry liquid 16 (in FIG. 2, slurry coating step S10). Then, the
resultant is dried with hot air (100.degree. C.) or the like (in
FIG. 2, coating drying step S11), and introduced into a calcining
furnace and calcined at a higher temperature (525 to 700.degree.
C.) than a calcination temperature (around 500.degree. C.) during
production of the exhaust gas treatment catalyst 15 (in FIG. 2,
coating calcining step S12). Thus, a regenerated exhaust gas
treatment catalyst 17 is obtained.
[0057] In other words, in the present embodiment, the surface of
the base 14 is coated with the slurry liquid 16 of the crushed
newly-made exhaust gas treatment catalyst 15, and calcined at a
higher temperature than that during the production of the exhaust
gas treatment catalyst 15. Thereby, the regenerated exhaust gas
treatment catalyst 17 is obtained with a surely increased degree of
sintering the surface thereof.
[0058] Therefore, according to the present embodiment, the exhaust
gas treatment catalyst 17 has a high-strength surface, even when
regenerated by first crushing, then re-molding, and calcining with
the surface being coated. The exhaust gas treatment catalyst 17 is
capable of demonstrating a sufficient wear resistance while keeping
a sufficient denitration performance. Thus, the exhaust gas
treatment catalyst 17 is continuously usable over a long period
(approximately 20,000 to 30,000 hours).
[0059] Note that, if the calcination temperature in the coating
calcining step S12 differs from the calcination temperature during
the production of a newly-made exhaust gas treatment catalyst 15
which is to be crushed for coating the base 14 by 25.degree. C. or
above, this can more surely increase the degree of sintering the
surface, which is very preferable. Meanwhile, if the calcination
temperature in the coating calcining step S12 exceeds 700.degree.
C., the crystal structure of the main component titanium oxide
(TiO.sub.2) changes from anatase form to rutile form. This causes
the exhaust gas treatment catalyst 17 to shrink, and may lower the
denitration performance, which is not preferable.
[0060] In addition, if the crushed and slurried newly-made exhaust
gas treatment catalyst 15 has an average particle diameter of 3 to
8, this can improve the wear resistance the most, which is very
preferable.
[0061] Moreover, in the used catalyst crushing step S1, as
described above, the used exhaust gas treatment catalyst 11 is
preferably crushed such that 70 to 95 wt % of the whole exhaust gas
treatment catalyst 11 becomes the coarse pieces 12. This is
because, if the coarse pieces 12 formed by the crushing are less
than 70 wt % of the whole used exhaust gas treatment catalyst 11,
an excessive amount of the exhaust gas treatment catalyst is
disposed of together with the fly ash and so forth. This
consequently lowers the regeneration efficiency and increases the
regeneration cost. Meanwhile, if the coarse pieces 12 formed by the
crushing exceed 95 wt % of the whole used exhaust gas treatment
catalyst 11, the fly ash and so forth may be incorporated into the
base 14 by a large amount.
Other Embodiments
[0062] Note that, in the above-described embodiment, the
description has been given of the case where the exhaust gas
treatment catalyst 10 is molded into a honeycomb shape. However,
the present invention is not limited thereto. As other embodiments,
in the case of an exhaust gas treatment catalyst molded into, for
example, a pellet shape, pipe shape, or other shapes, the present
invention is also employable in a similar manner to the
above-described embodiment.
[0063] Moreover, in the above-described embodiment, the description
has been given of the case where the exhaust gas treatment catalyst
10 is installed in a discharge line for exhaust gas from equipment,
such as a coal-fired boiler, for burning coal. However, the present
invention is not limited thereto. As long as ash in exhaust gas
adheres to and is deposited on a surface of an exhaust gas
treatment catalyst, the present invention is employable in a
similar manner to the above-described embodiment.
EXAMPLES
[0064] Hereinafter, description will be given of a confirmation
test to confirm the effects of the method of regenerating an
exhaust gas treatment catalyst according to the present invention
and the exhaust gas treatment catalyst obtained by the method.
However, the present invention is not limited only to the
confirmation test described below.
Test Example 1
Preparation of Test Samples
<<Test Sample A>>
[0065] An exhaust gas treatment catalyst A (TiO.sub.2=77.3%,
WO.sub.3=9.00%, V.sub.2O.sub.5=0.55%, others=13.15%) for
denitration having a honeycomb shape (height: 150 mm, breadth: 150
mm, length: 800 mm, wall thickness: 1.15 mm, pitch (distance
between the centers of adjacent walls): 7.4 mm, number of meshes
(n): 20.times.20) was used in an exhaust gas line of a coal-fired
boiler for approximately 70,000 hours. The catalyst A was crushed
with a crusher to obtain fragments a.
[0066] Next, the fragments a obtained by the crushing were screened
with a sieve (having a mesh size of 0.5 mm (the nominal dimensions
are specified according to Japanese Industrial Standards (JIS))).
The coarse pieces left on the sieve were pulverized (to an average
particle diameter of approximately 20 .mu.m) with a hammermill. The
fine powder thus obtained (15 kg), an organic binder (0.7 kg), a
glass fiber (1.5 kg (diameter: 11 .mu.m, length: 3 mm)), and water
(appropriate amount) were kneaded with a kneader and uniformed
mixed. The obtained kneaded product was supplied into an extruder
to prepare a precursor of an exhaust gas treatment catalyst having
a honeycomb shape (height: 69 mm, breadth: 69 mm, length: 800 mm,
mesh pitch: 7.4 mm, mesh opening: 6.25 mm, number of meshes (n):
9.times.9). The precursor was sufficiently naturally dried and
subsequently dried with hot air (100.degree. C..times.5 hours).
Thereafter, the precursor was subjected to a calcining treatment
(500.degree. C..times.3 hours) in a calcining furnace. Thus, a test
sample A of the regenerated exhaust gas treatment catalyst (base)
was obtained.
<<Test Sample B>>
[0067] An exhaust gas treatment catalyst B (TiO.sub.2=77.3%,
WO.sub.3=9.00%, V.sub.2O.sub.5=0.55%, others=13.15%) for
denitration having a honeycomb shape (height: 150 mm, breadth: 150
mm, length: 800 mm, wall thickness: 1.15 mm, pitch (distance
between the centers of adjacent walls): 7.4 mm, number of meshes
(n): 20.times.20) was used in an exhaust gas line of a coal-fired
boiler for approximately 65,000 hours. The catalyst B was crushed
with a crusher to obtain fragments b.
[0068] Next, the fragments b obtained by the crushing were treated
in a similar manner to the crushed fragments a of the test sample
A. Thus, a test sample B of the regenerated exhaust gas treatment
catalyst (base) was obtained.
<<Test Sample C>>
[0069] An exhaust gas treatment catalyst C (TiO.sub.2=77.3%,
WO.sub.3=9.00%, V.sub.2O.sub.5=0.55%, others=13.15%) for
denitration having a honeycomb shape (height: 150 mm, breadth: 150
mm, length: 800 mm, wall thickness: 1.15 mm, pitch (distance
between the centers of adjacent walls): 7.4 mm, number of meshes
(n): 20.times.20) was used in an exhaust gas line of a coal-fired
boiler for approximately 60,000 hours. The catalyst C was crushed
with a crusher to obtain fragments c.
[0070] Next, the fragments c obtained by the crushing were treated
in a similar manner to the crushed fragments a of the test sample
A. Thus, a test sample C of the regenerated exhaust gas treatment
catalyst (base) was obtained.
<Test Method>
<<Denitration Rate>>
[0071] Each of the test samples A to C was cut into pieces (number
of meshes: 6.times.7, length: 800 mm). One piece was put into a
reactor. The denitration rate was obtained for each test sample
under conditions described below. Note that, for comparison, the
denitration rate of a newly-made exhaust gas treatment catalyst
(comparison sample) was also obtained.
[0072] Test Conditions
[0073] Compositions of exhaust gas-- [0074] NO.sub.x: 150 ppm
[0075] NH.sub.3: 150 ppm [0076] SO.sub.2: 800 ppm [0077] O.sub.2:
4% [0078] CO.sub.2: 12.5% [0079] H.sub.2O: approximately 11.5%
[0080] N.sub.2: balance
[0081] Temperature of exhaust gas: 380.degree. C.
[0082] Amount of exhaust gas: 19.56 Nm/hr
[0083] U.sub.gs: 2.3 Nm/sec
[0084] AV: 23.26 Nm.sup.2/m.sup.2hr
Denitration rate (%)={1-(NO.sub.x concentration at catalyst
outlet/NO.sub.x concentration at catalyst inlet)}.times.100
<Test Results>
[0085] Table 1 below shows the test results of the test samples A
to C and the comparison sample.
TABLE-US-00001 TABLE 1 Denitration rate (%) Test sample A 79.5 Test
sample B 75.8 Test sample C 78.0 Comparison sample 82.1
[0086] As seen from Table 1 above, the denitration rates of the
test samples A to C respectively obtained from the raw materials of
the exhaust gas treatment catalysts A to C used under the
above-described conditions were lower than the denitration ratio of
the comparison sample (newly-made product) by approximately around
3 to 6%. Although the reason is not exactly known, it is
conceivable that the used coal contained a relatively large amount
of poisonous components and poisoned a relatively large amount of
the catalyst components.
Test Example 2
Preparation of Test Samples
<<Slurry Liquid .alpha.>>
[0087] A newly-made exhaust gas treatment catalyst
(TiO.sub.2=77.3%, WO.sub.3=9.00%, V.sub.2O.sub.5=0.55%,
others=13.15%, calcination temperature: 500.degree. C.) for
denitration having a honeycomb shape used in a coal-fired boiler
was crushed with a crusher. The fragments a obtained by the
crushing (1.5 kg) and water (5 liters) were introduced into a ball
mill (capacity: 7.2 liters) together with alumina balls (having
diameters of 25 mm and 15 mm, each 2.1 kg), and crushed (to an
average particle diameter of 4.94 .mu.m). Then, the concentration
thereof was adjusted (21%). Thus, a slurry liquid .alpha. was
prepared.
<<Test Samples A11 to A16>>
[0088] Next, test samples A obtained in Test Example 1 above were
each immersed in the slurry liquid .alpha. to coat the surface of
the test sample A with the slurry liquid .alpha.. Then, the
resultant test samples A were dried with hot air (100.degree.
C..times.5 hours), and subjected to a calcining treatment (5 hours)
at various temperatures (500.degree. C., 550.degree. C.,
600.degree. C., 650.degree. C., 700.degree. C., 750.degree. C.) in
a calcining furnace. Thus, test samples A11 to A16 of the exhaust
gas treatment catalyst having the surface coated (the amount of
coating on the outer surface area: 100 g/m.sup.2) were
prepared.
<Test Method>
<<Denitration Rate>>
[0089] The denitration rates of the test samples A11 to A16 were
obtained in a similar manner to Test Example 1 above.
<<Wear Rate>>
[0090] One piece of each of the test samples A11 to A16 was put
into a vertical reactor. A gas containing quartz sand (average
particle diameter: 50 .mu.m) (at a concentration of 300 g/m.sup.3)
was flowed therethrough from top to bottom under conditions
described below. Thereby, the wear rates were obtained. It should
be noted that the test sample A used had the meshes (n):
20.times.20 and a length of 100 mm, and that, for comparison, the
wear rate of a newly-made exhaust gas treatment catalyst
(comparison sample) was also obtained.
[0091] Test Conditions
[0092] Temperature: 20.degree. C.
[0093] Pressure: atmospheric pressure
[0094] Flow rate [0095] (through the cross section of the
catalyst): 10 m/sec
[0096] Flowing period: 1 hour
Wear rate (%)={(W.sub.0-W)/W.sub.0}.times.100
[0097] where W.sub.0 represents the weight of the catalyst before
the test, and W represents the weight of the catalyst after the
test.
<Test Results>
[0098] Table 2 below shows the test results of the denitration rate
and the wear rate. In addition, FIG. 3 shows a graph for obtaining
a relationship between a wear rate and a calcination temperature
difference from the calcination temperature during the production
of the crushed and slurried newly-made exhaust gas treatment
catalyst.
TABLE-US-00002 TABLE 2 Coating Calcination calcination temperature
Denitration temperature difference rate Wear rate (.degree. C.)
(.degree. C.) (%) (%) Test sample 500 0 82.1 1.30 A11 Test sample
550 50 82.1 0.72 A12 Test sample 600 100 81.7 0.67 A13 Test sample
650 150 81.3 0.64 A14 Test sample 700 200 80.9 0.60 A15 Test sample
750 250 *1 *1 A16 Comparison -- -- 82.1 0.51 sample *1: since the
sample shrank and was obviously unusable as a catalyst, the
measurement was omitted.
[0099] As seen from Table 2 above, the calcination temperature for
the test sample A16 was too high (750.degree. C.), and the crystal
structure of the main component titanium oxide (TiO.sub.2) changed
from anatase form to rutile form. This increased the degree of
sintering too excessively, and accordingly the test sample A16
shrank, so that the test sample A16 was not in a state capable of
demonstrating a function as a catalyst.
[0100] Meanwhile, the test samples A11 to A15 (coating calcination
temperature: 500 to 700.degree. C.) were observed to be capable of
demonstrating a sufficient performance in the denitration rate.
[0101] Furthermore, as seen from the context in FIG. 3, the test
samples A12 to A15 (calcination temperature difference:
.gtoreq.25.degree. C.) were observed to be capable of demonstrating
a sufficient performance in the wear rate (not higher than 1%;
continuously usable over 20,000 to 30,000 hours).
Test Example 3
Preparation of Test Samples
<<Slurry Liquids .alpha.1 to .alpha.5>>
[0102] Slurry liquids .alpha.1 to .alpha.5 having average particle
diameters shown in Table 3 below were prepared in a similar manner
to the slurry liquid .alpha. in Test Example 2 above.
<<Test Samples A21 to A25>>
[0103] Next, test samples A obtained in Test Example 1 above were
respectively immersed in the slurry liquids .alpha.1 to .alpha.5 to
coat the surfaces of the test samples A with the slurry liquids
.alpha.1 to .alpha.5. Then, the resultant test samples A were dried
with hot air (100.degree. C..times.5 hours), and subjected to a
calcining treatment (550.degree. C..times.5 hours) in a calcining
furnace. Thus, test samples A21 to A25 of the exhaust gas treatment
catalyst having the surface coated (the amount of coating on the
outer surface area: 100 g/m.sup.2) were prepared.
<Test Method>
<<Denitration Rate>>
[0104] The denitration rates of the test samples A21 to A25 were
obtained in a similar manner to Test Example 1 above.
<<Wear Rate>>
[0105] The wear rates of the test samples A21 to A25 were obtained
in a similar manner to Test Example 2 above.
<Test Results>
[0106] Table 3 below shows the test results of the denitration rate
and the wear rate.
TABLE-US-00003 TABLE 3 Slurry Average particle Wear rate liquid
diameter (.mu.m) (%) Test sample A21 .alpha.1 2.50 1.97 Test sample
A22 .alpha.2 3.12 0.78 Test sample A23 .alpha.3 5.16 0.70 Test
sample A24 .alpha.4 7.41 0.80 Test sample A25 .alpha.5 9.20
1.30
[0107] As seen from Table 3 above, the test samples A22 to A24
obtained by using the slurry liquids .alpha.2 to .alpha.4 having
average particle diameters of 3 to 8 .mu.m were observed to be
capable of demonstrating a sufficient wear performance (not higher
than 1%; continuously usable over 20,000 to 30,000 hours).
INDUSTRIAL APPLICABILITY
[0108] A method of regenerating an exhaust gas treatment catalyst
according to the present invention and an exhaust gas treatment
catalyst obtained by the method are extremely useful and beneficial
in various industries.
REFERENCE SIGNS LIST
[0109] 10 EXHAUST GAS TREATMENT CATALYST [0110] 10a HOLE
* * * * *