Note: Descriptions are shown in the official language in which they were submitted.
CA 02353073 2001-07-27
FIELD OF THE INVENTION
A multi-stage combined electrical power generator plants with one plant
utilizing natural gas while the other plant may also use natural gas or other
fuels
typically waste bio-mass fuels, for fuelling both steam turbine driven and
gas turbine driven electrical generators. Use of conventional fuels such as
coal
and oil is eliminated or substantially reduced thereby reducing the amount of
pollutants released into the atmosphere and prolonging the remaining life of
such
to conventional fuels as are available, for other uses, and increasing the
efficiency
of the generating station, for given unit volumes of fuels.
BACKGROUND OF THE INVENTION
Existing conventional power stations, other than hydro electrical stations,
are presently fired by regulated thermal fuels typically fossil fuel sources
such as
coal and oil. Nuclear fuelled stations are also included within this class.
Such systems are considered major polluters of the environment. Burning of
fossil fuel, is considered to be the predominant producer of greenhouse gases.
Since fossil fuels are non-renewable, continued use of these sources are
taxing
on the environment. The lifetime of the available sourcEa of these fuels is
being
a o seriously eroded by use for electrical generators.
Nuclear fuel presents a different but no less significant set of hazards,
which are
well know and require no repetition. It would be desirable to use alternative
fuel
sources that would be less taxing on the environment and would burn cleaner
and therefore reduce the amount of greenhouse gases released into the
atmosphere. This would also have the effect of reducing the demand on existing
sources of conventional fuels, thereby prolonging their availability for other
uses.
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It would also reduce problems of replacing ageing nuclE;ar plant. Use of less
conventional fuels such as natural gas, and bio-mass fuel materials would be
advantageous. Throughout this document, for ease of explanation, the term
"bio-mass fuel" is used to encompass such items as wood waste materials such
as wood chips, wood shavings, and saw dust, construction material and the
like,
land fill gas, digester gas and the like. Such bio-mass rnaterials at present
have
few useful functions, and in many cases are treated as 'waste to be simply
disposed of in landfill and the like. Natural gas has many advantages over
more
conventional fuels such as coal or oil, or even nuclear, but its use has not
been
to widely employed, due in part to the capital cost of building new plant.
Using such fuels for electrical generators would both provided a real use for
such
materials, and also solve the problem of disposal of such materials as waste
bio-
mass materials.
Also there is the ever present problem of ageing equipment. This is true both
of
conventional electrical generators and also nuclear fuelled generators.
Sooner or later these existing plants must be decommissioned and then
replaced . However capital costs of entire new generation plant using
conventional fuels make it impractical to close existing old coal or oil fired
generators, and replace them with new generators operating on the same fuel
2o systems. In most cases existing plants have been written off in the past.
They
have virtually no resale value. The capital cost of new plant must be written
off
over many years. Consequently the cost to the consumer of electrical power
would rise dramatically, if old plants were simply replaced with the same
plant
over again.
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However it has been determined that where the new plant uses natural gas or
other alternate fuels, in place of conventional fuels, and where the overall
efficiency of the new plant is raised above that of the old, then the capital
cost
may be written off over a shorter time span. This will enable power companies
to erect new plant using the advanced technology described herein, and due to
the accelerated write-off, the unit power cost to the consumer can be
maintained
within reasonable limits.
BRIEF SUMMARY OF THE INVENTION
to The invention seeks to pravide the foregoing improvements by the method of
generating electrical power in two adjacent electrical generating power plants
,
and including the steps of generating electrical power in a steam turbine
electrical generator using a fuel selected from bio-mass materials, generating
further electrical power by operating at least one natural gas fuelled gas
turbine
prime mover connected to an electrical generator, and supplying the electrical
power generated by the steam turbine and by the at least one gas turbine to a
supply grid, and transferring excess heat from the natural gas plant to the
bio-
mass fuel plant to augment the steam available to said steam turbine in the
bio-
mass plant.
2o The invention further seeks to provide such a method of generating
electrical
power in an electrical generating station, and including the steps of
generating
electrical power in a steam turbine electrical generator using a fuel selected
from
bio-mass materials, generating further electrical power k>y operating at least
one
natural gas fuelled gas turbine prime mover connected to an electrical
generator,
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and supplying the electrical power generated by the steam turbine and by the
at
least one gas turbine to a supply grid.
The invention further seeks to provide a method of electrical generation,
using
multiple natural gas turbines each operable to drive an electrical generator,
in a
single power station, whereby the efficiency of the station may be maintained
over a range of power demands, by selectively starting pup or shutting down
respective ones of the natural gas turbines, whereby whichever turbine or
turbines is in use at any given time will operate at its most efficient
capacity.
The invention further seeks to provide such a method bay operating the gas
~o turbine or turbines by continuous introduction of air, compressing the air,
introducing natural gas into the compressed air, and igniting the gas and
compressed air to create a high pressure exhaust of combustion products of gas
and air, driving at least one turbine and turbine shaft, with the shaft being
connected to drive the electrical generator to generate electrical power as
aforesaid.
The invention further seeks to provide such a method which further comprises
passing the hot exhaust gases from the gas turbine to a heat recovery steam
generator, to generate steam , and passing excess heat therefrom to said steam
turbine in said bio-mass fuel plant to augment the steam generated by the bio-
a o mass fuel.
The invention further seeks to provide such a method and which further
comprises the steps of, connecting the steam outlet of the steam turbine to a
condenser and returning the condensate back to the heat recovery steam
generator, whereby to recycle calorific values of the waste steam.
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The invention seeks to achieve the foregoing improvements by providing
apparatus for
generating electrical power, from a combination of fuels, and having a first
steam boiler heated
by fuel selected from bio-mass fuels, and a steam turbine electrical generator
connected
thereto for generating a first electrical supply, at least one natural gas
fuelled gas turbine
prime mover, a gas turbine powered electrical generator connected to the gas
turbine, for
generating a second electrical supply, a heat recovery steam generator
connected to the
exhaust of the gas turbine to generate steam, and excess heat from said heat
recovery steam
generator being used to generate further steam to drive the steam turbine
electrical generator
in the bio-mass plant, whereby to augment the steam generated in the bio-mass
steam boiler,
1o thereby increasing the first electrical supply from the steam turbine
powered generator, and
simultaneously generating a second electrical supply from the gas turbine
powered generator.
The invention further seeks to achieve the foregoing improvements by providing
apparatus for
generating electrical power, from a combination of natural gas turbines, in
which the natural
gas turbines may be selectively operated or shut down, depending on the power
demand at
any given time so as to maintain the naturals gas turbines operating at
maximum efficiency.
The invention further seeks to provide such an apparatus and having a first
steam boiler
heated by fuel selected from bio-mass fuels, and a steam turbine electrical
generator
connected thereto for generating a first electrical supply, at least one
natural gas fuelled gas
turbine prime mover, a gas turbine powered electrical generator connected to
the gas turbine,
2 o for generating a second electrical supply, a heat recovery steam generator
connected to the
exhaust of the gas turbine to generate steam, the steam being used to drive
the steam
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turbine electrical generator in the bio-mass plant, whereby to augment the
steam
generated in the bio-mass steam boiler, thereby increasing the first
electrical
supply from the steam turbine powered generator, and simultaneously
generating a second electrical supply from the gas turbine powered generator.
The apparatus preferably also includes a steam condenser connected to the
steam turbine and connected back to the heat recovery steam generator.
The invention further provides such an apparatus for generating electrical
power
and including a feed water supply connected to the condenser to make up water
for the heat recovery steam generator.
to
IN THE DRAWINGS
Figure 1 illustrates in schematic form two adjacent power generating plants
where one plant uses natural gas as fuel while the other plant uses bio-mass
fuel. For the purposes of illustrating the invention, and showing in phantom
duplicate components which may be provided to providE: increased capacity.;
and ,
Figure 2 illustrates in schematic form two adjacent power generating plants
where both plants use natural gas as fuel. Typically one gas plant would be
2o several time bigger than the adjacent gas plant (for example a 500 MW and
the
other a 50 to 100 MW plant). For the purposes of illustrating the invention,
duplicate components are shown in phantom which may be provided to provide
increased capacity.
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DESCRIPTION OF A SPECIFIC EMBODIMENT
F;eferring generally to Figure 1, it will be seen that the invention is
illustrated in the form of
firvo adjacent power plants consisting of one bio-mass fuel power plant (10a)
and a gas
fuelled power plant (10b). Each plant may be duplicated so that there may in
fact be one
or two or more of each component, the duplicate components being shown in
phantom.
E~io-Mass Power Plant.
The bio-mass plant (10a) will be seen to comprises a bio-mass fuel boiler(12)
operable
with a fuel of the type selected typically from bio-mass materials,
particularly waste bio-
mass materials, such as wood waste materials such as wood chips, wood
shavings, and
saw dust land fill gas, digester gas, and the like. Usage of such waste
materials solves the
problem of disposal of these materials while extracting heating values from
them and
rE:ducing the consumption of non-renewable resources. Boiler (12) produces
steam and is
connected to a steam turbine (14).
Turbine (14) drives electrical generator (16) for producing electricity. The
electricity is
typically sold to a power distribution system of "grid" for use by consumers.
On the other
hand it can be supplied to a single consumer, where electrical power is
required in very
Dirge quantities. Hot exhaust gases from the bio-mass boiler will usually be
passed through
heat recovery systems, and scrubbers known per se, before being vented to
atmosphere
through a stack (not shown). After passing over the steam turbine shaft the
injected steam
is condensed into hot water typically called condensate (15) by a condenser
(20).
To this extent therefor the bio-mass plant is similar in many respects to a
conventional fuel
type thermal generating station. However when combined as a
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unit in a multi plant system in the manner described below its efficiency is
increased, so that in addition to providing a means of disposal of materials
that
would otherwise be waste, it is also generates electrical power.
In operation the bio-mass fuels are burned in the boiler (12) to heat up the
condensate (15) to create steam. The steam is then injected into a steam
turbine (14) causing the steam turbine shaft (not shown) to spin. The steam
turbine shaft is connected to an electrical generator (16;) to produce
electricity.
Hot exhaust gases from the bio-mass boiler will usually be passed through heat
recovery systems, and scrubbers known per se, before being vented to
to atmosphere through a stack (not shown). The electricity is then exported to
the
consumer typically using a grid.
After passing over the steam turbine shaft, the injected team is then
condensed
into hot water, typically called condensate (15), by the condenser (20). Make
up
water is added to the condensate (15) to compensate for evaporation and
leakage throughout the system. The condensate (15) is then passed through
the heat exchanger (36) and it is heated up. The condensate (15) is then
pumped (not shown) into the boiler (12) to complete the bio-mass power plant
cycle. The condensate (15) is heated up by the heat transfer from the imported
steam (34) (described below) via the heat exchanger (35). Having given up its
2o heat, the imported steam (34) is converted to a condensate (42) which is
then
returned to the natural gas plant (10b) (described below). The imported steam
enables the bio-mass plant to increase its electrical output without having
the
need to burn additional fuel.
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Natural Gas Power Plant.
The natural gas power plant (10b) comprises at least one, and in this case
two, natural gas turbines (22), the second such turbine being shown in
phantom.
Two or more turbines are preferably provided in order to allow for shutting
down
one unit for maintenance and the like, or to provide a means of regulating
power
generation so as to match the supply to the demand at any given time . This
enables each of the natural gas turbines to be operated at maximum efficiency
over a wide range of demands for power.
Each gas turbine (22) is of conventional construction, similar in many
respects to
to an aircraft jet engine. Air is inducted and compressed by intake fans.
Natural
gas is injected into the compressed air and ignited. The combustion products
then pass through sets of turbine blades mounted on a central turbine shaft
(not
shown). All of this is well known and requires no illustration.
In this embodiment the shaft not shown of each gas turbine (22 ) is
mechanically coupled by any suitable transmission to a respective electrical
generator (26).
The hot exhaust gases exiting from the gas turbine (2c!) are ducted to
respective heat recovery steam generators (28). Heat 'from the hot exhaust
gases is used to heat the combined condensate (43) to create steam. The
2o exhaust from the heat recovery steam generator is vented to the atmosphere
via
an exhaust flue (not shown). The heat recovery steam generators (28) supply
steam to a steam turbine (30), which drives electrical generator (32).
Some steam from the heat recovery steam generator (28) is ducted to a heat
exchanger (36) located, in this example for illustration only, in bio-mass
plant
(10a).
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It will of course be understood that the heat exchanger (36) could equally
well be
located in the natural gas plant (10b) , without in any way changing its
function.
The remaining portion of the steam (35) produced by the heat recovery steam
generator (28) is then injected into the steam turbine (30). The injected
steam
(35) cause the steam turbine shaft (not shown) to spin. The steam turbine
shaft
is connected to an electrical generator (32) to produce Electricity. The
electricity
is then exported to the consumer typically using a grid.
After passing over the steam turbine shaft, steam is then condensed into hot
water, typically called condensate (41 ), by the condenser (40). Condensate
(42)
to which is returned from the bio-mass plant is combined with condensate (41 )
to
result in a combined condensate (43). Make up water is added to the combined
condensate (43) to compensate for evaporation and leakage. The combined
condensate (43) is then pumped (not shown) into the hE:at recovery steam
generator (28) completing the natural gas plant cycle.
An alternate embodiment of the invention is shown in Fig 2.
In this embodiment there are two plants of two different capacities namely the
smaller plant (100) and the second larger plant (200), both of which operate
on
natural gas as the fuel. The reason there may be two different plants may be
historical, or may be due to lack of funds , or ownership.. However when
zo connected together as described below greater efficiencies are achieved
than in
either plant on its own.
Smaller Natural Gas Plant.
Plant (100) has one (or more indicated in phantom) gas turbines) (102) each of
which is connected by a suitable transmission to a respective electrical
generator
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(104) which are in turn connected to supply power to consumers represented as
the grid.
Each gas turbine is of conventional construction, similar in many respects to
an
aircraft jet engine. Air is inducted and compressed by intake fans. Natural
gas
is injected into the compressed air and ignited. The combustion products then
pass through sets of turbine blades mounted on a central turbine shaft (not
shown). All of this is well known and requires no illustration.
The hot exhaust gases exiting from the gas turbine (102) are ducted to
respective heat recovery steam generators (106). Heat from the hot exhaust
to gases is used to create steam (108). The exhaust gases from the heat
recovery steam generator (106) are vented to the atmosphere via an exhaust
flue (not shown).
The steam (108) produced by the heat recovery steam generator (106) is then
injected into the steam turbine (110). The injected steam causes the steam
turbine shaft (not shown) to spin. The steam turbine shaft is connected to an
electrical generator (112) to produce electricity. The electricity is then
exported
to the consumer typically using a grid.
Hot exhaust gases from the heat recovery steam generator will usually be
passed through scrubbers known per se, before being vented to atmosphere
2o through a stack (not shown).
After passing over the steam turbine (110) , the injected steam is then
condensed into hot water, typically called condensate (114), by the condenser
(116). Make up water is added to the condensate to compensate for
evaporation and leakage throughout the system. The condensate is then
passed through the heat exchanger (118) and it is heatE:d up. The condensate
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is then pumped (not shown) into the heat recovery steam generator (106) to
complete the smaller power plant cycle.
The condensate is heated up by the heat transfer from the imported steam
(209) (described below) via the heat exchanger (118). Having given up its
heat,
the imported steam (209) is converted to a condensate (221 )(described below)
which is then returned to the larger natural gas plant (200) (described
below).
The imported steam enables the smaller natural gas plant to increase its
electrical output without having the need to burn additional fuel.
Larger Natural Gas Plant ..
The larger natural gas power plant (200) comprises at least one, and in this
case
two, natural gas turbines (202), the second such turbine being shown in
phantom. The turbines (202) drive respective electrical generators (204). Two
or more turbines are preferably provided in order to allow for shutting down
one
unit for maintenance and the like, or to provide a means of regulating power
generation so as to match the supply to the demand at .any given time. This
enables each of the natural gas turbines to be operated at maximum efficiency
over a wide range of demands for power.
Each gas turbine is of conventional construction, similar in many respects to
an
aircraft jet engine. Air is inducted and compressed by intake fans. Natural
gas
ao is injected into the compressed air and ignited. The cornbustion products
then
pass through sets of turbine blades mounted on a central turbine shaft (not
shown). All of this is well known and requires no illustration. The turbine
The hot exhaust gases exiting from the gas turbines (202) are ducted to in
known manner to respective heat recovery steam generators (206). Heat from
the hot exhaust gases is used to heat the combined condensate (208) to create
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steam. The exhaust gases from the heat recovery steam generator is vented to
the
atmosphere via an exhaust flue (not shown).
Some fraction (209) of the total steam exiting from the heat recovery steam
generator
(206) is ducted, to a heat exchanger (118) located, in this example for
illustration only, in
the smaller natural gas plant (100).
It will of course be understood that the heat exchanger (118) could equally
well be located
in the larger natural gas plant (200), without in any way changing its
function.
The steam (212) produced by the heat recovery steam generator (206) is the
injected into
the steam turbine (214). The injected steam (212) cause the steam turbine
shaft (not
shown) to spin. The steam turbine (214) is connected to an electrical
generator (216) to
produce electricity. The electricity is then exported to the consumer
typically using a grid.
After passing over the steam turbine shaft, steam is then condensed into hot
water,
typically called condensate (218), by the condenser (220). Condensate (221 )
from the
heat exchanger (118) is returned from the smaller natural gas plant is
combined with
condensate (218) to result in a combined condensate (208).
Make up water is added to the combined condensate (208) to compensate for
evaporation
and leakage. The combine condensate (208) is then pumped (not shown) into the
heat
recovery steam generator (206) completing the large natural gas plant cycle.
Typically one gas plant would be several time bigger than the adjacent gas
plant (for
example a 500 MW and the other a 50 to 100 MW plant).
The foregoing is a description of a preferred embodiment of the invention
which is given
here by way of example only. The invention is not to be taken as limited
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CA 02353073 2001-07-27
to any of the specific features as described, but comprehends all such
variations
thereof as come within the scope of the appended claims.
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