Power plants – Combustion products used as motive fluid – With combustible gas generator
Utility Patent
1998-02-25
2001-01-02
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
With combustible gas generator
C060S039182, C060S039511
Utility Patent
active
06167691
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a gasification power generation system. More specifically, the invention relates to a gasification power generation system for gasifying a fossil fuel, such as coal, a gas or a heavy oil, or a fuel, such as domestic or industrial waste, with a gasifying agent, such as oxygen or air, to produce a fuel gas to generate electricity using the product fuel gas.
Among fuels generally called fossil fuels, coal is widely distributed over the world in comparison with petroleum and natural gases, and the reserve thereof is high, so that there are great expectations that coal will be used as a fuel for power generation in future. As a power generation method using coal as a fuel, a pulverized-coal thermal power generation for grinding coal into pulverized coal to burn the pulverized coal is well known. However, since the pulverized-coal thermal power generation has problems on thermal efficiency and environmental suitability, coal gasification power generation systems for gasifying coal and burning the product fuel gas have been developed.
In the coal gasification power generation system, a gasifying agent, such as air or oxygen, and coal serving as a fuel are gasified using gasifying means to produce a gasified product gas, and a gas turbine is rotated by a combustion exhaust gas to generate electricity. There has been also proposed an integrated coal gasification combined cycle power generation system for utilizing the exhaust heat of a gasified product gas, which has been used to rotate a gas turbine, to produce steam to rotate a steam turbine to generate electricity. The integrated coal gasification combined cycle power generation system can use coal, which has a relatively great reserve and which is widely distributed over the world, to generate electricity at low costs, and use the gas turbine combined with the steam turbine, so that it is possible to efficiently generate electricity without wasting the exhaust heat of the gas turbine.
As a gasifying agent, air is directly used as mentioned above, or oxygen or oxygen-enriched air is used. In order to remove ash contents, which are contained in coal, as a molten slat in a molten state from a gasifier, it is required to raise the temperature in the gasifier to a high temperature of 1600° C. to 1700° C. However, in the case of an air-blast type integrated coal gasification combined cycle power generation system, which uses air as a gasifying agent, since air serving as the gasifying agent is supplied to a gasifier at a relatively low temperature of about 300° C. to 400° C., it is not possible to sufficiently raise the temperature in the gasifier, so that there is a problem in that the gasifier is obstructed by slag, which has not been sufficiently molten.
When a great deal of air is blown to raise the temperature in the gasifier, the rate of completed burned coal is increased, and the amount of nitrogen in the gasified product gas is also increased. As a result, the hearing value of the gasified product gas is small, and it is difficult to maintain stable combustion in a combustion equipment for a gas turbine. In order to eliminate the above disadvantages in the air-blast type integrated coal gasification combined cycle power generation system, an oxygen-blast type integrated coal gasification combined cycle power generation system as shown in
FIG. 1
has been proposed as an example of a conventional coal gasification power generation system.
FIG. 1
is a block diagram of a schematic system of an integrated coal gasification combined cycle power plant. In
FIG. 1
, the integrated coal gasification combined cycle power plant comprises gasifying means
10
and power generation means
20
. The gasifying means
10
comprises a gasifier
11
, a gas cooler
12
, a char recovery facility
13
, a gas clean-up facility
14
, and an oxygen producing facility
15
. The power generating means
20
comprises a gas-turbine combustion equipment
21
, a gas turbine
22
, a steam turbine
23
, generators
24
a
,
24
b
, a condenser
25
, and an exhaust heat recovery boiler
26
. With this construction, the operation of the integrated coal gasification combined cycle power plant will be described below.
First, an oxygen-enriched air
16
produced by the oxygen producing facility
15
and a coal
17
are supplied to the gasifier
11
to be gasified therein to produce a gasified product gas
18
. The principal components of the gasified product gas
18
include carbon monoxide, hydrogen, carbon dioxide, steam and so forth. The ash contents in the coal
17
are discharged as a molten slag
19
a
from the bottom of the gasifier
11
. The gasified product gas
18
is cooled to a suitable temperature (e.g., about 500° C.) by means of the gas cooler
12
to be fed to the gas clean-up facility
14
via the char recovery facility
13
. Most of a char
19
b
(the principal components of which include unburned carbon and ash contents) contained in the gasified product gas
18
is recovered by the char recovery facility
13
to be recycled in the gasifier
11
. The gas clean-up facility
14
removes sulfur contents and fine particles, which cause the corrosion and wear of the gas turbine
22
, to supply a clean product gas to the gas-turbine combustion equipment
21
.
The gasified product gas
18
cleaned by the gas clean-up facility
14
is burned by the gas-turbine combustion equipment
21
to produce a combustion exhaust gas
27
, which rotates the gas turbine
22
to cause the generator
24
a
to generate electricity. The heat of the combustion exhaust gas
27
discharged from the gas turbine
22
is heat-recovered by the exhaust heat recovery boiler
26
, and the recovered heat produces a steam
28
to rotate the steam turbine
23
. This rotating force causes the generator
24
b
to generate electricity. The steam
28
discharged from the steam turbine
23
is condensed into a water
29
by means of the condenser
25
to be recycled in the exhaust heat recovery boiler
26
. The heat recovered by the gas cooler
12
is also utilized to produce the steam
28
. The water
29
condensed by the condenser
25
is supplied to the exhaust heat recovery boiler
26
as well as the gas cooler
12
, which forms the gasifying means
10
, to cool the gasified product gas
18
.
In the conventional oxygen-blast type integrated coal gasification combined cycle power generation system, which has the above construction and operation, it is possible to produce a high-temperature gasified product gas in the gasifier
11
while maintaining the molten state of the slag. Therefore, it is possible to prevent the gasifier from being obstructed by solidified slag, and it is possible to prevent nitrogen components from being excessive to stabilize combustion in the gas-turbine combustion equipment. In the above described conventional integrated coal gasification combined cycle power plant, in order to solve the above described problems of the air-blast type coal gasification means, pure oxygen or oxygen-enriched air is used as a gasifying agent in place of air to decrease the amount of nitrogen in the gasified product gas.
However, in the conventional coal gasification power generation system for performing oxygen blast, it is required to provide an oxygen producing facility or an oxygen-enriched air producing facility to produce oxygen or oxygen-enriched air producing facility to produce oxygen or oxygen-enriched air blown into the gasifying means as a gasifying agent, so that there is a problem in that power consumed in the power generation system in increased to considerably decrease the generating efficiency in the whole system. Also in the oxygen-blast type coal gasification power generation system, if temperature in the gasifier is not sufficiently raised, a great deal of char is discharged from the gasifier while being contained in the gasified product gas. Therefore, there is a problem in that it is required to provide a large scale char recovery facility, so that the plant is complicated and the manufacturi
Fukuda Masafumi
Hori Michio
Murata Keiji
Ogawa Takashi
Sasaki Masakuni
Casaregola Louis J.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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