Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Sulfur or sulfur containing component
Reexamination Certificate
1999-08-13
2001-05-08
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Sulfur or sulfur containing component
C423S244080, C423S215500, C095S019000, C095S022000, C095S285000
Reexamination Certificate
active
06228336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dust collecting apparatus for dedusting a Ca-containing gas by a ceramics filter and an operation method thereof.
2. Description of the Prior Art
A ceramics filter is appropriate for collecting dust contained in a high temperature gas. Especially in a pressurized fluidized-bed combustion power generation system as shown in
FIG. 7
, the ceramics filter provided therein is effective for reducing the wear rate of the gas turbine blade material and reducing dust in the combustion waste gas to be discharged into the air.
A prior art dust collecting apparatus will be described with reference to FIG.
7
. In
FIG. 7
, coal
101
, supplied air
102
and a desulfurizing agent
103
are supplied into a pressurized fluidized-bed combustion furnace
1
. The desulfurizing agent
103
is first supplied into a hopper
15
through a valve
14
which is open. Then the valve
14
is closed and the hopper
15
is pressurized by a gas (not shown) so that a pressure in the hopper
15
and that in a hopper
13
become equal to each other. Then a valve
12
is opened and the desulfurizing agent
103
is caused to fall into the hopper
13
. The desulfurizing agent
103
is metered by a feeder
16
and is carried with a gas flow to be mixed into air
105
so that a mixture
104
of the air and the desulfurizing agent is supplied into the pressurized fluidized-bed combustion furnace
1
.
The coal
101
is fluidized by the supplied air
102
to be combusted. SO
2
, which is generated by the combustion, reacts with and is absorbed by the desulfurizing agent
103
.
A combustion gas
201
generated at the pressurized fluidized-bed combustion furnace
1
is dedusted by a cyclone
2
. Dust
202
which is removed from combustion gas
201
is discharged out of the system. Combustion gas
301
, after being dedusted, bifurcates to enter a filter container
3
a
,
3
b
respectively. In the filter container
3
a
,
3
b
,there are provided a multiplicity of ceramics filters
31
a
,
31
b
. Each of the ceramics filters
31
a
,
31
b
is tubular and is constructed in such a gas flow structure that a cyclone outlet gas (combustion gas)
302
,
303
is led thereinto and the combustion gas passes therethrough from an inside to an outside thereof.
When the combustion gas
302
,
303
passes through the ceramics filter
31
a
,
31
b
, the dust contained in the combustion gas
302
,
303
is collected on an inner surface of the ceramics filter
31
a
,
31
b
. The dust so collected on the ceramics filter is peeled off by a back wash gas
306
,
307
, which flows periodically, and falls down in the ceramics filter
31
a
,
31
b
to a bottom portion of the filter container
3
a
,
3
b
to be recovered therefrom at
308
,
309
. In a buffer tank
33
, there is stored a pressurized air
304
, thus the back wash gas
306
,
307
is supplied into the filter container
3
a
,
3
b
by opening an closing a valve
32
a
,
32
b
periodically so as to allow the pressurized air from the buffer tank
305
to flow through valve
32
a
,
32
b.
Combustion gases
401
,
402
, having passed through the ceramics filter
31
a
,
31
b
, joins together outside of the filter containers
3
a
,
3
b
, to form a combustion gas
403
, which is introduced into a gas turbine
4
. The combustion gas
403
drives the gas turbine
4
to thereby generate an electric power by a generator
10
. A combustion gas
501
at the gas turbine outlet is supplied into a waste heat recovery boiler
5
so that a sensible heat of the combustion gas
501
is converted into steam energy
701
by a heat exchanger
9
. The steam
701
drives a steam turbine
7
to thereby generate electric power by a generator
11
. Steam
801
which has come out of the steam turbine is changed to become a condensate by a condenser
8
and water
901
thereof is pressurized again to be supplied to the heat exchanger
9
of the waste heat recovery boiler
5
. The combustion gas
601
which has passed through the waste heat recover boiler
5
is discharged into the air from a stack
6
.
In the pressurized fluidized-bed combustion power generation system, if a load is increased, the temperature of the combustion gas
301
is elevated corresponding to the load. Thus, the temperature of the ceramics filter
31
a
,
31
b
is also elevated. Generally that temperature is approximately 650° C. at a load of 50%, approximately 750° C. at a load of 75% and approximately 830° C. at the load of 100%. When a B type limestone is used for the desulfurizing agent
103
in the prior art system shown in
FIG. 7
, no change over time is caused in the differential pressure in the ceramics filter
31
a
,
31
b
at the temperature of 650° C. However, in a case where the load is increased and the temperature of the ceramics filter
31
a
,
31
b
exceeds 750° C., a phenomenon is caused in which the differential pressure in the ceramics filter
31
a
,
31
b
is elevated over time. If the temperature is set to a temperature at which the differential pressure in the ceramics filter
31
a
,
31
b
starts to become elevated, the differential pressure in the ceramics filter
31
a
,
31
b
continues to increase until the operation must be finally stopped.
Elevation of the filter back wash pressure is effective as one of the methods for reducing the filter differential pressure. However, to elevate the filter back wash pressure invites a breakage of a seal portion of the ceramics filter
31
a
,
31
b
or a breakage of a pressure structure portion of the filter container
3
a
,
3
b
. Hence, there is an upper limit value in the filter back wash pressure. Even if the back wash pressure is set to a maximum back wash pressure within a permissible range, if the B type limestone is used and the filter temperature is between 750° C. and 810° C., the filter differential pressure continues to increase over time, and there is a problem that the operation of the pressurized fluidized-bed combustion power generation system must be finally stopped.
SUMMARY OF THE INVENTION
It is therefore a basic object of the present invention to provide a dust collecting apparatus in which a specific mineral is mixed into an inlet gas of the dust collecting apparatus to thereby suppress the rate of increase of a differential pressure in a ceramics filter and eliminate the need to stop the operation of a pressurized fluidized-bed combustion power generation system. It is also an object of the present invention to provide an operation method of the dust collecting apparatus in which the supply amount of the mineral is regulated.
In order to attain these objects, the present invention is featured in providing a dust collecting apparatus and method as follows.
A first dust collecting apparatus is provided that contains a ceramics filter for dedusting a combustion gas that is channeled to the dust collecting apparatus from a combustion furnace. A means is also provided for supplying a de-sticking agent comprising at least one mineral of a group including MgO, MgCO
3
or Mg(OH)
2
into an inlet gas of the dust collecting apparatus. It is to be noted that the de-sticking agent may be supplied into the inlet gas in the form of a substance containing MgO, MgCo
3
and Mg(OH)
2
.
A dust collecting apparatus similar to the first dust collecting apparatus is provided, wherein the supplying means is a limestone supplying apparatus for the combustion furnace.
A dust collecting apparatus similar to the first dust collecting apparatus is provided, wherein the supplying apparatus is connected to an inlet or an outlet of a cyclone which is provided at an outlet of the combustion furnace.
A dust collecting apparatus similar to the first dust collecting apparatus is provided, wherein the mineral or the substance containing the mineral is supplied into the combustion furnace in a water slurry.
An operation method of any of the above dust collecting apparatus is also provided, wherein a supply amount of the mineral or the substance containing the mineral is regulated corresponding to
Fujioka Yuichi
Hashimoto Akira
Kaneko Shozo
Katsuki Yasuo
Ohnishi Takashi
Griffin Steven P.
Hokkaido Electric Power Company, Inc.
Strickland Jonas N.
Wenderoth , Lind & Ponack, L.L.P.
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