Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1998-05-26
2001-02-20
Beck, Shrive (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C095S049000, C422S178000, C422S180000
Reexamination Certificate
active
06190621
ABSTRACT:
BACKGROUND OF THE INVENTION
1 Field of the Invention
The present invention relates to a desulfurization apparatus for coal gas containing sulfur, and an electric power plant using the same.
2 Description of the Related Art
Among fossil fuels, coal is distributed widely in the world in comparison with oil and natural gas. Fossil fuel reserves are plentiful and are expected to be used in the future for generating electric power. A known method of generating electric power involves pulverizing coal in order to be burned.
In view of thermal efficiency and adaptability to the environment, there has been developed a coal gasification compound electric power plant in which coal is gasified. The gasified coal is first desulfurized, burned, and then the burned gas is then fed to a gas turbine and a steam turbine to generate electric power.
FIG. 1
is a block diagram of a conventional coal gasification combined electric power plant using a desulfurization apparatus. Electric power plant
21
has coal gasification equipment
22
, gas purification equipment
41
, and compound electric power generating equipment
24
. The coal gasification equipment
22
includes gasification furnaces
27
a
and
27
b
, that mix pulverized coal
25
and a gasification agent
26
(normally, oxygen) and perform gasification under predetermined conditions. A gas cooler
28
cools coal gas
11
which is exhausted from the gasification furnace
27
b.
The coal gas
11
exhausted from the gas cooler
28
passes through the desulfurization tower
2
within the dry desulfurization apparatus
1
. Thereafter, the gas
11
passes through a filter
29
provided within the scrubbing apparatus
23
. Then, the gas
11
is supplied to the combined electric power generating equipment
24
.
The coal gas
11
is burned in a burner
30
provided within the combined electric power generating equipment
24
. The burned gas is supplied to an exhaust heat recovery boiler
33
through a gas turbine
31
. A condenser
36
and a steam turbine
35
are provided in the exhaust heat recovery boiler
33
.
Operation of the coal gasification combined electric power plant
21
having the above structure will be described below. The pulverized coal
25
and the gasification agent
26
are mixed. The mixed gas is supplied to the gasification furnace
27
a
which has a high temperature. In the gasification furnace
27
a
, a reaction occurs in which carbon is mainly oxidized to carbon dioxide. An inner portion of the gasification furnace
27
b
is under high pressure and a reduction reaction takes place mainly between the carbon dioxide and carbon therein. Carbon monoxide is produced through the reduction reaction. Accordingly, the gasification furnaces
27
a
and
27
b
gasify the coal at a high temperature and a high pressure (which varies according to the gasification method, for example, about 1400° C. and about 2 MPa) so as to produce the coal gas
11
. The produced coal gas
11
is composed of carbon monoxide, hydrogen, carbon dioxide, and water vapor.
The coal gas
11
is cooled to a suitable temperature (about 500° C.) in the gas cooler
28
. The cooled coal gas
11
is fed to the desulfurization tower
2
within the gas purification equipment
41
.
The desulfurization tower
2
removes H
2
S contained in the coal gas
11
. The coal gas
11
exhausted from the desulfurization tower
2
passes through the filter
29
thereafter. The filter
29
removes dust contained in the coal gas
11
. Accordingly, the desulfurization tower
2
and the filter
29
remove sulfur and fine particles that cause corrosion and abrasion of the gas turbine by passing the coal gas
11
therethrough.
The clean coal gas
11
from which sulfur and fine particles are removed is supplied to the combined electric power generating equipment
24
.
The clean coal gas
11
, purified in the gas purification equipment
41
, is burned in the burner
30
. The burned combustion gas rotates the gas turbine
31
to generate electric power. Exhaust gas
32
is exhausted from the gas turbine
31
and fed to the exhaust heat recovery boiler
33
. The exhaust heat recovery boiler
33
takes the heat from the exhaust gas
32
so as to produce steam
34
. Steam
34
rotates the steam turbine
35
to generate electric power. The steam
34
, exhausted from the steam turbine
35
, is condensed in the condenser
36
. A part of the condensed steam is fed back to the exhaust heat recovery boiler
33
. The remainder of the condensed steam is fed to the gas cooler
28
.
Further, heat recovered from the coal gas
11
in the gas cooler
28
is combined with the steam
34
fed from the exhaust heat recovery boiler
33
fed to the steam turbine
35
. Thereafter, the steam
34
is discharged from the steam turbine
35
and returned to the gas cooler
28
through the condenser
36
.
When coal is gasified, most of the sulfur contained in the coal becomes hydrogen sulfide and becomes mixed with the coal gas
11
. A convention desulfurization apparatus for removing the hydrogen sulfide at a high temperature using iron oxide as the desulfurization agent, is the dry desulfurization apparatus
1
. The dry desulfurization apparatus
1
performs desulfurization while keeping the temperature of the coal gas
11
high for as long as possible. The fluid upon which the desulfurization function has been performed is supplied to the compound electric power generating equipment
24
. The dry desulfurization method exhibits excellent thermal efficiency.
The structure of the dry desulfurization apparatus
1
will be described below with reference to FIG.
2
. It comprises a desulfurization tower
2
, a regeneration tower
3
, a reduction tower
37
, a sulfur condenser
8
, a circulation gas compressor
9
and a heater
10
.
The coal gas
11
flows from an end (the lower portion in the drawing) of the desulfurization tower
2
. The flowing coal gas
11
is mixed with desulfurization agent
38
provided within the desulfurization tower
2
. A chemical reaction between the coal gas
11
and the desulfurization agent
38
occurs according to formula (1).
Fe
2
O
3
+2H
2
S+H
2
→2FeS+3H
2
O (1)
The coal gas
11
from which the sulfur is removed thereafter flows out from the other end (the upper portion in the drawing) of the desulfurization tower
2
.
The desulfurization agent
38
which absorbs the sulfur contained in the coal gas
11
, thus becoming a sulfide, and is fed to an end (the upper end in the drawing) of the regeneration tower
3
. Air
39
, including oxygen, is supplied from the other end (the lower portion in the drawing) of the regeneration tower
3
. A chemical reaction shown in formula (2) occurs between the sulfide and the air within the regeneration tower
3
, so that the sulfide is oxidized. The sulfide can be regenerated by this oxidizing reaction.
4FeS+7O
2
→2Fe
2
O
3
+4SO
2
(2)
The regenerated desulfurization agent
38
is again fed to the desulfurization tower
2
and reused. The desulfurization agent
38
is moved between the desulfurization tower
2
and the regeneration tower
3
by air current transmission.
The sulfur removed from the desulfurization agent
38
becomes a sulfurous acid gas in the regeneration tower
3
. That gas is then fed to the reduction tower
37
as a regeneration tower outlet gas
14
. The regeneration tower outlet gas
14
is supplied to an end (the lower portion in the drawing) of the reduction tower
37
and undergoes a chemical reaction (3) with a smokeless coal
40
supplied to the other end (the upper portion in the drawing) of the reduction tower
37
, as shown in the following formula:
2C+2SO
2
→2CO
2
+S
2
(3)
A sulfur steam is produced by the chemical reaction that flows into the sulfur condenser
8
(the upper portion in the drawing).
The sulfur steam is cooled within the sulfur condenser
8
. The sulfur steam is condensed by the cooling and discharged to an outer portion of the dry desulfurization apparatus
1
as the chemical element sulfur
16
.
The tail gas
17
that flo
Hori Michio
Murata Keiji
Ogawa Takashi
Yamashita Keijiro
Beck Shrive
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Varcoe, Jr. Frederick
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