U.S. patent application number 14/345775 was filed with the patent office on 2014-08-14 for energy storage technology for demanded supply optimisation.
This patent application is currently assigned to DOOSAN BABCOCK LIMITED. The applicant listed for this patent is DOOSAN BABCOCK LIMITED. Invention is credited to Konrad Jerzy Kuczynski, Douglas John Spalding.
Application Number | 20140223909 14/345775 |
Document ID | / |
Family ID | 44937495 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140223909 |
Kind Code |
A1 |
Kuczynski; Konrad Jerzy ; et
al. |
August 14, 2014 |
ENERGY STORAGE TECHNOLOGY FOR DEMANDED SUPPLY OPTIMISATION
Abstract
A comburant gas supply system is provided for a combustion
boiler/turbine of a thermal power plant, a combustion
boiler/turbine system and a thermal power plant. The gas supply
system has an air separation module to separate and output an
oxygen rich gas from an input air supply; a comburant gas storage
module fluidly connected to the output of the air separation module
for storage in liquid state of separated oxygen rich gas; a
comburant gas supply module to supply the oxygen rich gas to the
combustion boiler selectively from the air separation system and/or
the comburant gas storage system. The air separation module has an
oxygen rich gas output capacity determined from a demand rating for
the combustion boiler/turbine adjusted with reference to a load
factor across a predetermined operating period and/or the ASU size
is increased to provide longer term energy storage capacity.
Inventors: |
Kuczynski; Konrad Jerzy;
(Renfrew, GB) ; Spalding; Douglas John; (Renfrew,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOOSAN BABCOCK LIMITED |
Crawley, Sussex |
|
GB |
|
|
Assignee: |
DOOSAN BABCOCK LIMITED
Crawley, Sussex
GB
|
Family ID: |
44937495 |
Appl. No.: |
14/345775 |
Filed: |
September 18, 2012 |
PCT Filed: |
September 18, 2012 |
PCT NO: |
PCT/GB2012/052300 |
371 Date: |
March 19, 2014 |
Current U.S.
Class: |
60/652 ; 110/188;
110/234; 110/297; 60/659 |
Current CPC
Class: |
F23L 7/007 20130101;
F01K 13/00 20130101; Y02E 20/344 20130101; F25J 3/04951 20130101;
F22B 35/00 20130101; F25J 2240/28 20130101; Y02E 20/32 20130101;
F01K 7/16 20130101; F01K 13/02 20130101; F25J 3/04496 20130101;
Y02E 20/326 20130101; Y02E 20/34 20130101; F25J 3/04836 20130101;
F25J 3/04963 20130101; F25J 3/04533 20130101; F25J 3/04581
20130101; F25J 2260/30 20130101; F25J 2260/80 20130101; F23N 3/00
20130101 |
Class at
Publication: |
60/652 ; 110/297;
110/234; 110/188; 60/659 |
International
Class: |
F01K 13/02 20060101
F01K013/02; F23N 3/00 20060101 F23N003/00; F01K 7/16 20060101
F01K007/16; F23L 7/00 20060101 F23L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2011 |
GB |
1116157.7 |
Claims
1. A comburant gas supply system for a combustion boiler/turbine of
a thermal power plant comprising: an air separation module to
separate and output an oxygen rich gas from an input air supply; a
comburant gas storage module fluidly connected to the output of the
air separation module for storage in liquid state of separated
oxygen rich gas; a comburant gas supply module to supply the oxygen
rich gas to the combustion boiler selectively from the air
separation system and/or the comburant gas storage system; wherein
the air separation module has an oxygen rich gas output capacity
based on one or both of: a demand rating for the combustion
boiler/turbine adjusted with reference to a load factor across a
predetermined operating period; a demand for electrical energy
storage that is required.
2. A combustion boiler/turbine system of a thermal power plant
comprising a combustion boiler for combustion of a fuel in the
presence of an oxygen rich comburant gas; a turbine unit driven
thereby; and a comburant gas supply system in accordance with claim
1 fluidly linked thereto to supply comburant gas to the combustion
boiler to support combustion of the fuel.
3. A system in accordance with claim 1, wherein the air separation
module has an oxygen rich gas output capacity that is less than
100% of the nominal steady state comburant gas requirement of the
boiler/turbine unit to which it supplies comburant gas.
4. A system in accordance with claim 1,wherein the air separation
module has an oxygen rich gas output capacity that is more than
100% of the nominal steady state comburant gas requirement of the
boiler/turbine unit to which it supplies comburant gas.
5. A system in accordance with claim 1, wherein the air separation
module has an oxygen rich gas output capacity sized to a percentage
of the full nominal comburant gas requirement of the boiler/turbine
unit to which it supplies oxygen rich comburant gas, which
percentage is related to a predetermined operational load factor of
the associated combustion boiler/turbine unit over a suitable
operating period.
6. A system in accordance with claim 1, wherein the air separation
module has an oxygen rich gas output capacity sized to provide a
long term energy storage capacity and additionally a percentage of
the full nominal comburant gas requirement of the boiler/turbine
unit to which it supplies oxygen rich comburant gas, which
percentage is related to a predetermined operational load factor of
the associated combustion boiler/turbine unit over a suitable
operating period.
7. A system in accordance with claim 1, wherein the air separation
module has a minimum comburant gas supply capacity determined as
the product of a nominal steady state comburant gas demand for the
associated combustion boiler/turbine unit and a predetermined
boiler/turbine unit operational load factor over a suitable
operating period.
8. A system in accordance with claim 1, wherein the comburant gas
storage module is sized and adapted to accommodate variation in
comburant gas requirement of the boiler/turbine unit over the
operating period, and supply up to the nominal full load comburant
gas requirement of the boiler/turbine unit, in that the comburant
gas storage module is configured selectively to store excess
separated oxygen rich gas or be a source of supply of additional
separated oxygen rich gas to the comburant gas supply module.
9. A system in accordance with claim 1, wherein the comburant gas
storage module is sized at least to a sufficient level to effect at
least the following: that the air separation module is capable of
producing at least the total volume of comburant gas needed to meet
the total demand of the associated boiler/turbine unit across the
time period; that in combination with the comburant gas storage
module, supply of comburant gas is enabled which meets at least the
nominal steady state demand of the associated boiler/turbine unit
at any time during the said period when it is operating at full
steady state load.
10. A system in accordance with claim 1, wherein the air separation
module is adapted to produce and supply gas that is substantially
free of nitrogen.
11. A system in accordance with claim 1, wherein the air separation
module is adapted to store separated nitrogen/argon rich gas in
nitrogen/argon storage facility for release in response to a
demanded energy recovery.
12. A system in accordance with claim 1, wherein air separation
module is adapted to produce and supply gas that is substantially
pure oxygen.
13. A system in accordance with claim 1, wherein the air separation
module is configured to make use of electrical energy from the
renewable source or low cost source, where low cost energy is not
derived from the process that is utilising Oxygen gaseous
product.
14. A system in accordance with claim 1, wherein a load factor is
determined across a suitable period of operation to accommodate
changes in daily/seasonal/annual demand or a period of scheduled
down-time.
15. A system in accordance with claim 1, wherein a load factor is
determined across a period of at least 24 hours.
16. A system in accordance with claim 1 wherein a load factor is
determined across a period of up to one year.
17. A system in accordance with claim 1, further comprising a
combustion furnace provided with one or more burners for the
combustion of carbonaceous fuel.
18. A system in accordance with claim 13 comprising one or more
coal burners.
19. A system in accordance with claim 1, further comprising a
carbon dioxide compression and storage module for the compression
and storage of at least some of the carbon dioxide produced by
combustion of fuel in the combustion boiler.
20. A system in accordance with claim 15 further comprising a
carbon dioxide compression and storage module having a capacity
related to the carbon dioxide output of the combustion boiler such
as to enable a nominal carbon emissions rate of zero or less during
steady state operation of the boiler/turbine.
21. A thermal power plant comprises a power generation unit having
a comburant gas supply system and/or a combustion boiler/turbine
system in accordance with claim 1.
22. A combustion furnace unit acting as industrial or domestic heat
source having a comburant gas supply system and/or a combustion
boiler/turbine system in accordance with claim 1.
23. A method of operation of a thermal power plant having an air
separation module for the separation of an oxygen rich comburant
gas supply for oxyfuel firing of fossil fuel an oxygen rich
comburant gas storage facility, characterized by the steps of:
providing a combustion boiler/turbine system of a thermal power
plant having a combustion boiler for combustion of a fuel in the
presence of an oxygen rich comburant gas; determining for the said
combustion boiler a nominal steady state comburant gas demand;
determining for the combustion boiler a design load factor across a
pre-determined operating period; and/or defining required energy
storage capacity required to determine ASU unit and LOX storage
size; providing in association therewith an air separation module
to separate and output an oxygen rich comburant gas from an input
air supply, a comburant gas storage module fluidly connected to the
output of the air separation module for storage in liquid state of
separated oxygen rich gas, and a comburant gas supply module to
supply the oxygen rich gas to the combustion boiler selectively
from the air separation system and/or the comburant gas storage
system; wherein the air separation module is operated at an oxygen
rich gas separation capacity based on the said comburant gas demand
of the combustion boiler/turbine adjusted to take account of the
said determined load factor and/or said required energy storage
capacity.
24. A method in accordance with claim 23 wherein a minimum output
capacity of the air separation module is determined as the product
of the nominal steady state comburant gas demand and the design
load factor.
25. A method of determination of a design capacity of an air
separation module according to claim 23, with reference to the
demand capacity of a combustion boiler which it is to supply with
comburant gas, which method comprises the steps of: determining a
nominal comburant gas supply level for steady state operation for
the combustion boiler; determining a load factor for the combustion
boiler across a pre-determined operating period; and/or defining a
required energy storage capacity; determining a comburant gas
output capacity for the air separation module from the nominal
steady state demand rating adjusted with reference to the
determined load factor and/or required energy storage capacity.
26. A method in accordance with claim 25 wherein the step of
determining a comburant gas output capacity for the air separation
module comprises determining a design output for the air separation
module which is less than the nominal comburant gas demand of the
combustion boiler at steady state, but which is at least the
product of the nominal steady state comburant gas demand and the
design load factor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a National Stage of International Application No.
PCT/GB2012/052300 filed Sep. 18, 2012, claiming priority based on
GB Patent Application No. 1116157.7 filed Sep. 19, 2011, the
contents of all of which are incorporated herein by reference in
their entirety.
FIELD
[0002] The invention relates to a thermal power plant having either
an oxyfuel firing capability or a partial oxyfuel firing
capability, and preferably combined with biomass firing technology,
and to a gas supply system for, control system for and method of
operation of the same. The invention in particular relates to a gas
supply system for, control system for and a method of operation of
a thermal power plant suitable for flexible operation in response
to varying demand.
DESCRIPTION OF RELATED ART
[0003] Most of the energy used in the world today is derived from
the combustion of fossil fuels, such as coal, oil, and natural gas,
for example in thermal power generation plants. The combustion of
such fossil fuels produces a large volume of CO.sub.2 which is
conventionally vented to atmosphere. Atmospheric CO.sub.2 is
recognised as a significant greenhouse gas. It has been established
that one of the main causes of global warming is the rise in
greenhouse gas contamination in the atmosphere due to
anthropological effects. The limitation of further release of
greenhouse gases and into the atmosphere is generally recognised as
a pressing environmental need. The successful implementation of
strategies to reduce atmospheric CO.sub.2 emissions from the
combustion of fossil fuels is important if the continued use of
fossil fuels in many applications, including power generation, is
to be possible.
[0004] Oxyfuel firing is a means of firing the fuel with an oxygen
enriched comburant gas. In conventional fossil fuel fired
combustion equipment for example in boilers for steam generation
the oxygen required to burn the fuel is supplied by using
atmospheric air as a comburant gas. In the case of oxyfuel firing a
supply of gas with a higher oxygen content, and in particular a
mixture of substantially pure O.sub.2 and recycled CO.sub.2, is
used as a comburant gas. The oxyfuel combustion process seeks to
produce combustion products that are highly concentrated in
CO.sub.2 and in particular consist essentially of CO.sub.2 and
water to facilitate carbon capture and mitigate the CO.sub.2
emissions. To effect this, the combustion air supply must first be
is separated prior to supply to the furnace in a suitable air
separation unit (ASU). Only the separated gaseous oxygen is
intended for supply to the combustion process. The separated
nitrogen/argon mix may be expanded and vented to atmosphere or
stored in storage tanks for later expansion and venting. Within the
air separation unit processes the liquid oxygen may be
cryogenically stored in an embedded or external liquid oxygen (LOX)
storage facility. Liquid air may be stored in an embedded or
external liquid air (LA) storage facility.
[0005] In a conventional Oxyfuel plant where combustion furnace
uses as comburant gas mixture of CO.sub.2 rich recycled flue gas
and Oxygen, the operation of the air separation unit (ASU) coupled
to that of the boiler and to that of the compression and
purification unit (CPU) the ASU and CPU are designed for operation
at 100% nominal boiler demand.
[0006] An example of the current state of the art technology is
presented on FIG. 1. The figure comprises one ASU unit producing
O.sub.2 for one Boiler/Turbine Unit, and one CPU unit. The ASU and
Boiler/Turbine Unit and CPU are sized accordingly to coupled
operation at steady state with reference to the nominal steady
state Boiler/Turbine Unit O.sub.2 requirement. Thus O.sub.2
production in the example ASU is equal to the nominal steady state
Boiler/Turbine Unit O.sub.2 requirement of 100 kg/s. The
Boiler/Turbine Unit is producing at this steady state full load 170
kg/s of CO.sub.2, and this amount is compressed in CPU. The
electrical energy required to power the ASU Unit is extracted from
the Boiler/Turbine Unit.
[0007] Another example of the current state of the art is presented
on FIG. 2. On this figure the ASU unit is sized accordingly to full
Boiler/Turbine Unit oxygen requirement 100 kg/s with embedded LOX
storage to for example boost ASU response time. The electrical
energy required to power the ASU Unit is extracted from the
Boiler/Turbine Unit.
[0008] Another example of current the current state of the art is
presented on FIG. 3. On this figure the ASU is sized accordingly to
full Boiler/Turbine Unit oxygen requirement 100 kg/s and is
supported with external LOX storage to for example boost ASU
response time. The electrical energy required to power the ASU Unit
is extracted from the Boiler/Turbine Unit.
[0009] In all cases the prior art systems to provide Oxyfuel
combustion in mixture of flue gas and gaseous oxygen require the
plant to have an ASU sized at least to 100% nominal boiler
comburant demand. Indeed, in each case it is known additionally
that the ASU could be oversized to accommodate a maximum boiler
demand that is higher than nominal demand and/or that the LOX
storage could be oversized to shorten ASU response time to
accommodate rapid Boiler/Turbine Unit oxygen gas demand
changes.
[0010] Fossil fuel thermal power plants have a particular role in a
practical mixed supply grid. Typically they are not run
continuously at full load. Instead, their output will vary, partly
in response to changes in supply or demand within the grid so that
the grid supply is maintained. Operation in this way in response to
diurnal and seasonal changes in demand, and periods of downtime,
can reduce load factors over a period to 80% or less. If the ASU is
designed for operation at 100% nominal boiler demand this leads to
an excess of capacity, and increases both capex and opex costs for
the plant.
SUMMARY
[0011] In accordance with an aspect of an exemplary embodiment, a
comburant gas supply system for a combustion boiler/turbine of a
thermal power plant is provided that includes an air separation
module to separate and output an oxygen rich gas from an input air
supply; a comburant gas storage module fluidly connected to the
output of the air separation module for storage in liquid state of
separated oxygen rich gas; a comburant gas supply module to supply
the oxygen rich gas to the combustion boiler selectively from the
air separation system and/or the comburant gas storage system;
wherein the air separation module has an oxygen rich gas output
capacity based on one or both of: [0012] a demand rating for the
combustion boiler/turbine adjusted with reference to a load factor
across a predetermined operating period; a demand for electrical
energy storage that is required.
[0013] Similarly, in accordance with a further aspect of the
invention, a combustion boiler/turbine system of a thermal power
plant is provided comprising a combustion boiler for combustion of
a fuel in the presence of an oxygen rich comburant gas; a steam
turbine unit driven thereby; and a comburant gas supply system as
above described fluidly linked to supply comburant gas to the
combustion boiler to support combustion of the fuel.
[0014] Similarly, in accordance with a further aspect of the
invention, a combustion boiler/turbine system of a thermal plant is
provided comprising a combustion furnace for combustion of a fuel
in the presence of an oxygen rich comburant gas to provide heat
input to the industrial process; and a comburant gas supply system
as above described fluidly linked to supply comburant gas to the
combustion furnace to support combustion of the fuel.
[0015] Similarly, in accordance with a further aspect of the
invention, a combustion boiler/turbine system of a thermal power
plant is provided comprising a combustion boiler for combustion of
a fuel in the presence of an oxygen rich comburant gas; a gas
turbine unit driven thereby; and a comburant gas supply system as
above described fluidly linked to supply comburant gas to the
combustion boiler to support combustion of the fuel.
[0016] The key to the invention is that the air separation module
is not, as is conventional in the art, sized to the full nominal
comburant gas requirement of the combustion boiler/turbine unit
with which is it designed to be used. Instead, it is sized to a
reduced comburant gas requirement less than the full nominal
comburant gas requirement of the boiler/turbine unit running at
full capacity, but rather based on an adjusted comburant gas
requirement of the boiler/turbine unit that takes account of a
boiler/turbine unit load factor over a predetermined operating
period. The air separation module is sized to a percentage of the
full nominal comburant gas requirement of the boiler/turbine unit
to which it supplies oxygen rich comburant gas, which percentage is
related to a predetermined operational load factor of the
combustion boiler/turbine unit over a suitable operating period.
Additionally the air separation module size may be changed to offer
longer term energy storage than previous load factor based
sizing.
[0017] Operation of the air separation module is decoupled from
that of the boiler/turbine unit to which it ultimately supplies
oxygen rich comburant gas. Therefore the ASU unit is utilizing
electrical energy from grid that comes from renewable sources or
other low cost sources. It in neither rated to the full nominal
comburant gas requirement of the combustion boiler/turbine unit nor
limited to operation during periods in the operational cycle when
the boiler/turbine unit is operational.
[0018] Instead, the air separation module is supported, variation
in comburant gas requirement of the boiler/turbine unit over the
operating period is accommodated, and supply up to the nominal full
load comburant gas requirement of the boiler/turbine unit is
enabled by use of the comburant gas storage module selectively to
store excess separated oxygen rich gas or be a source of supply of
additional separated oxygen rich gas to the comburant gas supply
module.
[0019] That is to say, when the combustion boiler/turbine unit is
operating at an immediate comburant gas demand level that is less
than the volume of oxygen rich gas produced by the air separation
module, for example if the combustion boiler/turbine unit is
operating at substantially less than full load or is not in
operation, surplus oxygen rich gas is stored in the comburant gas
storage module. When the combustion boiler/turbine unit is
operating at an immediate comburant gas demand level that is
greater than the volume of oxygen rich gas produced by the air
separation module, for example if the combustion boiler/turbine
unit is operating at substantially full load, a resultant shortfall
in oxygen rich gas supplied by the air separation module to the
comburant gas supply module is supplement by oxygen rich gas stored
in the comburant gas storage module.
[0020] In this way, it is not necessary for the air separation
module to be sized, as is conventionally the case, with respect to
the full capacity nominal comburant gas demand level of the
boiler/turbine unit to which it ultimately supplies oxygen rich
comburant gas. It is merely necessary that it is sized in
conjunction with a comburant gas storage module to be able to
supply the comburant gas requirement of the boiler/turbine unit
over a load cycle based on a typical load factor for the cycle.
Both capex and opex costs can be reduced relative to air separation
modules which are conventionally sized and coupled to the nominal
operational load of the boiler/turbine unit.
[0021] Nitrogen/argon separated in the ASU unit can be stored in
compressed form in tanks for later expansion and stored energy
recovery on demand.
[0022] The air separation module produces an oxygen rich comburant
gas from an input supply of air, in particular preferably to
support oxyfuel firing of a carbonaceous fuel in the associated
boiler/turbine unit, and the comburant gas storage module stores
this gas if required. For example the air separation module may be
provided with at least one and preferably a plurality of air
separation unit compressors, for example producing an oxygen rich
comburant gas by cryogenic separation. Although the term "oxygen
rich gas" is intended to cover any gas having a proportion of
oxygen which is greater than atmospheric air it will be appreciated
that in practice for oxyfuel firing a comburant gas that is
substantially free of nitrogen and in particular a comburant gas
that is substantially pure oxygen will be preferred.
[0023] Preferably therefore the air separation module is adapted to
produce and supply gas that is substantially free of nitrogen and
in particular that is substantially pure oxygen to the comburant
gas storage module and/or comburant gas supply module. For example
the air separation module comprises one or more cryogenic air
separation units as will be familiar.
[0024] The underlying inventive concept of the invention lies in
the determination of a suitable size (that is, a suitable oxygen
rich gas production capacity) for an air separation module in
accordance with the invention, which is determined not with
reference to 100% nominal boiler comburant demand for a steady
state operation (and still less with reference to a higher maximum
boiler demand) but is rather determined with reference to an
adjusted demand that takes account of a boiler load factor over a
suitable pre-determined period of time and/or that takes account of
an energy storage demand.
[0025] Thus in accordance with the principles of the invention, a
minimum size for an air separation module, and a minimum comburant
gas supply capacity, can be determined as the product of a nominal
steady state comburant gas demand for the associated boiler/turbine
unit and a boiler/turbine unit load factor and the energy storage
requirement. In a preferred case, this may be the optimal size,
although some additional capacity may be provided for other
operational reasons. This allows the air separation unit to be
smaller than it would be if sized for full nominal boiler steady
state demand and reduces both build and operational costs. For
example, an air separation module in accordance with the invention
may be sized to no more than 90% of the nominal boiler steady state
operation comburant demand if the Boiler/Turbine Unit is operating
over the period of time with load factor 0.8 and 10% of
Boiler/Turbine Unit capacity is required as additional immediate
demanded energy storage.
[0026] The invention does not exclude the possibility that an air
separation module may still embody the principles of the invention
but be sized to be larger than this, for example to accommodate a
maximum boiler demand that is higher than the steady state demand
and/or to enable the storage of an excess of comburant gas in the
comburant gas storage module, which may for instance be used in
conjunction with the air separation unit as a source of energy
storage to provide demand. Both of these principles are known in
the prior art. However, the essence of the invention remains that
the operation parameters to be determined for the air separation
module are de-coupled from those to be determined with reference to
steady state operation of the boiler/turbine system, and instead
adjusted to take account of the applicable load factor for the
boiler/turbine system and/or required additional energy storage
capacity.
[0027] In accordance with the principles of the invention, an air
separation module is sized with reference to a nominal boiler
comburant demand at steady state adjusted for a load factor over a
period of time and/or required additional energy storage capacity.
Its associated comburant gas storage module is sized accordingly to
accommodate fluctuations in demand over that period of time and if
required to provide long term comburant storage.
[0028] In accordance with the principles of the invention, the air
separation module and associated gas storage module, should
optimally be sized at least to a sufficient level to effect at
least the following:
[0029] a) that the air separation module is capable of producing at
least the total volume of comburant gas needed to meet the total
demand of the associated boiler/turbine unit across the time
period;
[0030] b) that in combination with the comburant gas storage
module, supply of comburant gas is enabled which meets at least the
nominal steady state demand of the associated boiler/turbine unit
at any time during the said period when it is operating at full
steady state load.
[0031] A load factor is determined across a suitable period of
operation, for example over a full cycle to accommodate changes in
daily/seasonal/annual demand, period of scheduled down-time
etc.
[0032] An air separation module has a design capacity designed with
reference to the nominal demand of a boiler/turbine system with
which it is intended to be used adjusted to reflect a design load
factor of the boiler/turbine system. The design process first
involves determining such a load factor over a suitable period of
time.
[0033] A suitable period of time might be a period from 24 hours up
to a year, and might include periods in between.
[0034] Even when rated for relatively continuous operation changes
in levels of demand over the course of a day and over the course of
a year can reduce load factors over such a period to 80% or less.
An air separation module in accordance with the invention might
therefore have a gas output capacity based on no more than 80% of
the nominal steady state demand rating of the combustion
boiler/turbine. In many other systems, designed for less the
continuous operation, load factors may be considerably less than
80%, for example as low as 50%.
[0035] The principles of the invention embody all such systems
where the design output capacity of the air separation module is
made with reference to the nominal steady state demand rating of
the boiler/turbine adjusted to a realistically determined load
factor and/or required energy storage capacity.
[0036] Preferably, the combustion furnace comprises one or more
burners for the combustion of carbonaceous fuel for example
including carbonaceous fossil fuel, for example including coal, and
for example pulverised coal, but also for example including gas,
and for example including oil, and for example including biomass,
and for example including distillate, and any combination of same.
The comburant gas supply module is adapted to supply comburant gas
to the burners to support the combustion of the fuel in use.
Suitable fuel supply means supply fuel to the combustion site for
oxyfuel combustion in familiar manner.
[0037] The air separation module provides in the typical case the
sole source of comburant gas supply to the combustion
boiler/turbine system. In this context it will of course be
understood that even where references made to a module or system in
the singular the invention embodies all arrangements of apparatus,
whether comprising single air separation units and single boilers
or plural separation units and/or plural boilers working
cooperatively together, where the air separation system is sized in
accordance with the principles of the invention with reference to a
demand rating for the combustion boiler/turbine system adjusted to
a suitable load factor across a pre-determined operating
period.
[0038] Preferably, the combustion boiler/turbine system of the
invention, further comprises a carbon dioxide compression and
storage module for the compression and storage of at least some of
the carbon dioxide produced by combustion of fuel in the combustion
boiler. Suitable compression and storage units will be well known
from the art. Since it is a principle of the invention that the
operational capacity and parameters of the air separation system
have been decoupled from those of the boiler/turbine system, it
follows that the specific operational parameters and capacity of
the carbon dioxide compression and storage module are not
specifically pertinent to the invention. However, in the preferred
case, a carbon dioxide compression and storage module will be
provided which has a compression capacity determined by and coupled
to the boiler output, and for example to the output of combustion
CO.sub.2 at least at nominal steady state capacity. Thus, the
compression and storage unit is not decoupled in the same way from
the boiler capacity but is preferably rated at least with reference
to the required capture rate of nominal boiler demand.
[0039] It will be understood in the art that some carbonaceous
fuels such as fossil fuels are considered at contributing at 100%
of CO.sub.2 volume produced to a nominal emissions measurement,
whereas other carbonaceous fuels, such as bio-fuels, are considered
to contribute at a zero emissions rate.
[0040] In a preferred case, the carbon dioxide compression and
storage module is rated to a compression capacity which will enable
a nominal carbon emissions rate of zero or less during steady state
operation of the boiler/turbine.
[0041] It follows that in the case where a boiler is designed for
firing using fossil fuels with nominal 100% emissions contribution,
the compression and storage module should be rated for a
compression volume that is equal to that of the total furnace
CO.sub.2 emission volume at steady state operation. Where a boiler
is rated for a fuel mix, such as a mixed fossil fuel and bio-mass
firing, or a pure bio-mass firing, which has a reduced or zero
nominal emissions contribution, two possibilities arise. A carbon
dioxide compression and storage unit may be reduced in size
accordingly, so as to compress and store just that quantity of
carbon dioxide produced from the boiler which is sufficient to give
a zero nominal emissions for the system, with the remaining
CO.sub.2 being vented to atmosphere, for example via a stack, or
the carbon dioxide compression and storage system may have a
greater design capacity, producing a system with a negative
emissions rate.
[0042] In accordance with the invention in a further aspect, a
thermal power plant comprises a power generation unit having a
comburant gas supply system in accordance with the first aspect of
the invention and/or a combustion boiler/turbine system in
accordance with the second aspect of the invention.
[0043] In accordance with the invention in a further aspect, a
method of operation of a thermal power plant having an air
separation module for the separation of an oxygen rich comburant
gas supply for oxyfuel firing of fossil fuel an oxygen rich
comburant gas storage facility is provided. The method includes:
providing a combustion boiler/turbine system of a thermal power
plant having a combustion boiler for combustion of a fuel in the
presence of an oxygen rich comburant gas; determining for the said
combustion boiler a nominal steady state comburant gas demand;
determining for the combustion boiler a design load factor across a
pre-determined operating period; and/or defining required energy
storage capacity required to determine ASU unit and LOX storage
size; providing in association therewith an air separation module
to separate and output an oxygen rich comburant gas from an input
air supply, a comburant gas storage module fluidly connected to the
output of the air separation module for storage in liquid state of
separated oxygen rich gas, and a comburant gas supply module to
supply the oxygen rich gas to the combustion boiler selectively
from the air separation system and/or the comburant gas storage
system; wherein the air separation module is operated at an oxygen
rich gas separation capacity based on the said comburant gas demand
of the combustion boiler/turbine adjusted to take account of the
said determined load factor and/or said required energy storage
capacity.
[0044] Thus, in accordance with the method of the invention, an air
separation module is provided and operated at an output capacity
which is decoupled from the demand capacity of the boiler/turbine
at steady state, and is less or more than 100% of the said steady
state demand, but is instead adjusted to take account of the load
factor and/or required energy storage capacity. In particular, a
minimum output capacity of the air separation module is preferably
determined as the product of the nominal steady state comburant gas
demand and the load factor and the required energy storage
capacity.
[0045] Thus, the method can in an alternative be seen as a method
of determination of a design capacity of an air separation module
as above described, with reference to the demand capacity of a
combustion boiler which it is to supply with comburant gas, which
includes: determining a nominal comburant gas supply level for
steady state operation for the combustion boiler; determining a
load factor for the combustion boiler across a pre-determined
operating period; and/or defining a required energy storage
capacity; determining a comburant gas output capacity for the air
separation module from the nominal steady state demand rating
adjusted with reference to the determined load factor and/or
required energy storage capacity.
[0046] In particular, the method comprises determining a design
output for the air separation module which is less than the nominal
comburant gas demand of the combustion boiler at steady state, but
which is at least the mean comburant gas demand of the boiler over
the pre-determined operating period when due account is taken of
the load factor and required energy storage capacity.
[0047] The method is in particular a method of operation of a
thermal power plant comprises a power generation unit having a
comburant gas supply system in accordance with the first aspect of
the invention and/or a combustion boiler/turbine system in
accordance with the second aspect of the invention, and preferred
features will be understood by analogy.
[0048] In particular it follows that the step of determining a load
factor adjusted demand is preferably determined as the product of
the nominal steady state comburant gas demand and the load
factor.
[0049] In particular it follows that the oxygen rich comburant gas
is suitable for oxyfuel firing of carbonaceous fuel and is for
example preferably substantially free of nitrogen and more
preferably substantially pure oxygen.
[0050] It is a requirement of the invention that the comburant gas
production capacity of the air separation module is decoupled from
the demand requirement of the boiler and is instead reduced with
reference to a load factor adjusted demand and/or increased to
provide required energy storage capacity. In effect, the load
factor and/or storage capacity adjusted demand sets a minimum
requirement for the production capacity of the air separation
module. The air separation module may still be provided with a
higher capacity, for example to accommodate peak demand levels
above nominal or to provide an energy storage flexibility in which
the air separation module is run at a higher capacity during
periods of lower power demand.
[0051] More specifically in this later case, the method of
operation may additionally comprise: tending to reduce the works
power of the air separation module in response to an increased grid
demand and balancing the same by comburant gas from storage to make
up the required supply for oxyfuel firing; or tending to increase
the works power of the air separation module in response to a
reduced grid demand and balancing the same by supplying the
resultant excess to the storage.
[0052] Thus, the air separation system is operated at reduced power
at times of higher grid demanded output, and this reduced power
reduces the overall works power of the plant in order to supply
additional power to the grid without the need to vary the power
output of the generation plant.
[0053] In accordance with the invention the energy stored in
compressed nitrogen/argon form in tanks could be recovered when
demanded.
[0054] In accordance with the invention in a further aspect, a
thermal power plant comprises a power generation unit having an
oxyfuel firing system including an air separation system as above
described.
BRIEF DESCRIPTION OF DRAWINGS
[0055] The principles of operation of the invention will be
described in greater detail by way of exemplification with
reference to the accompanying drawings in which:
[0056] FIG. 1 is a schematic diagram of a prior art system in which
an air separation unit is sized at least to 100% nominal boiler
comburant demand;
[0057] FIG. 2 is a schematic diagram of a prior art system in which
an air separation unit is sized at least to 100% nominal boiler
comburant demand;
[0058] FIG. 3 is a schematic diagram of a prior art system in which
an air separation unit is sized at least to 100% nominal boiler
comburant demand;
[0059] FIG. 4 is a schematic diagram of an embodiment of the
invention in which an air separation unit is sized at less than
100% nominal boiler comburant demand but rather at a comburant
demand adjusted by a boiler load factor determined over a suitable
period of time;
[0060] FIG. 5 is a schematic diagram of an embodiment of the
invention in which an air separation unit is sized at less than
100% nominal boiler comburant demand but rather at a comburant
demand adjusted by a boiler load factor determined over a suitable
period of time;
[0061] FIG. 6 a schematic diagram of an embodiment of the invention
in which an air separation unit is sized at less than 100% nominal
boiler comburant demand but rather at a comburant demand adjusted
by a boiler load factor determined over a suitable period of
time;
[0062] FIG. 7 a schematic diagram of an embodiment of the invention
in which an air separation unit is sized at less than 100% nominal
boiler comburant demand but rather at a comburant demand adjusted
by a boiler load factor determined over a suitable period of time;
and
[0063] FIG. 8 a schematic diagram of an embodiment of the invention
in which an air separation unit is sized at less than 100% nominal
boiler comburant demand but rather at a comburant demand adjusted
by a boiler load factor determined over a suitable period of
time.
DETAILED DESCRIPTION OF THE INVENTION
[0064] FIGS. 1 to 3 are schematic diagrams of prior art systems and
have been discussed in that context hereinabove. In each instance
the figure shows for clarity one ASU unit producing O.sub.2 for one
Boiler/Turbine Unit, and one CPU unit. The ASU and Boiler/Turbine
Unit and CPU are sized in coupled manner for steady state
operation, whereby production in the ASU is equal to the
boiler/turbine steady state requirement of 100 kg/s. The
Boiler/Turbine Unit produces 170 kg/s of CO.sub.2, and this amount
is compressed in CPU.
[0065] FIGS. 4 to 8 are schematic diagrams of embodiments of the
invention in which a similar ASU unit producing O.sub.2 for a
similar Boiler/Turbine Unit is sized at less than 100% nominal
Boiler/Turbine Unit O.sub.2 demand but rather at demand level
adjusted by a boiler load factor determined over a suitable period
of time.
[0066] In general principle, a suitable minimum ASU size is
determined by the formula:
ASU=(100*(BLF)*O2Dem)+AESC (1)
Where:
[0067] BLF--Boiler/Turbine Load Factor over the assumed period of
time (for example, a daily cycle, a seasonal cycle, an annual
cycle, with or without account taken of downtime); [0068] O2Dem--is
the Boiler Nominal Comburant demand. [0069] AESC--Additional Energy
Storage Capacity that is required [0070] The LOX storage may be
sized accordingly.
[0071] The ASU could be oversized to accommodate a maximum boiler
demand that is higher than nominal demand. Additionally the LOX
storage could be oversized to accommodate a maximum boiler demand
that is higher than nominal demand.
[0072] A possible embodiment of the invention is presented in FIG.
4. The figure again shows for clarity one ASU unit producing
O.sub.2 for one Boiler/Turbine Unit, and one CPU unit. In the
example embodiment the ASU Unit is sized to 80% of the
Boiler/Turbine Unit nominal Oxygen requirement and is supported by
embedded in ASU LOX Oxygen storage. The Boiler/Turbine Unit
operates only with coal and with a determined load factor 0.8 over
an operating period. The CPU Unit is sized for full mass of the
Boiler/Turbine CO.sub.2 gas emission at 170 kg/s of CO.sub.2.
Compressing and storing emissions from firing the coal results in
unit having nominal zero emissions.
[0073] Another possible embodiment of the invention is presented in
FIG. 5. In this example embodiment the ASU Unit is sized to 60% of
the Boiler/Turbine Unit nominal Oxygen requirement and is supported
by LOX Oxygen storage external to the ASU. The Boiler/Turbine Unit
is designed for firing with 50% of coal and 50% of biomass and
operates with load factor 0.6 over an operating period. The CPU
Unit is sized for full CO.sub.2 gas volume from coal firing and
full CO.sub.2 gas volume from biomass firing in the Boiler/Turbine
Unit to total gas emission at 128 kg/s of CO.sub.2. Compressing and
storing emissions from firing the biomass results in unit having
negative emissions.
[0074] Another possible embodiment of the invention is presented in
FIG. 6. In this example embodiment the ASU Unit is sized to 75% of
the Boiler/Turbine Unit nominal Oxygen requirement and is supported
by LOX Oxygen storage external to the ASU. The Boiler/Turbine Unit
is designed for firing with 50% of coal and 50% of biomass and
operates with load factor 0.75 over an operating period. The CPU
Unit is sized for CO.sub.2 gas storage of 68 kg/s of CO.sub.2. Gas
emission at 68 kg/s of CO.sub.2 is released to atmosphere via the
stack. In effect, the CPU Unit is sized for CO.sub.2 gas storage of
the emissions from the Boiler/Turbine Unit attributable to coal
firing only. Compressing and storing emissions from firing the coal
results in unit having near zero nominal emissions.
[0075] Another possible embodiment of the invention is presented in
FIG. 7. In this example embodiment the ASU Unit is sized to 50% of
the Boiler/Turbine Unit nominal Oxygen requirement and is supported
by LOX Oxygen storage external to ASU. The Boiler/Turbine Unit
fires only biomass and operates with load factor 0.5 over an
operating period. The CPU Unit is sized for full CO.sub.2 gas
volume from the biomass firing in the Boiler/Turbine Unit at 170
kg/s of CO.sub.2. Compressing and storing emissions from firing the
biomass results in unit having negative emissions.
[0076] Although FIGS. 4 to 7 show for simplicity a schematic in
which a single ASU unit produces O.sub.2 for a single
Boiler/Turbine Unit, and emissions therefrom are shown compressed
by a single CPU unit it will be understood that this is by may of
illustration only, and that the invention embodies any combination
of plural ASU modules and/or plural boiler/turbine modules and/or
where applicable plural CPU modules to give the required
capacities, and in particular to meet the requirement that an air
storage system produces O.sub.2 or other oxygen rick comburant gas
for a boiler/turbine system at less than 100% nominal demand but
rather at demand level adjusted by a boiler load factor determined
over a suitable period of time.
[0077] Another possible arrangement of the invention showing
various such combinations, the principles of each of which may be
applied separately in a practical embodiment of the invention, is
presented in FIG. 8.
[0078] The illustrated embodiment has four Boiler/Turbine Units A,
B, C, and D, and one common LOX storage.
[0079] Boiler/Turbine Unit A fires 50% of coal and 50% of biomass
and operates with load factor 0.75 over an operating period. The
Boiler/Turbine Unit A has one ASU unit and the ASU unit is sized to
75% of Boiler/Turbine Unit nominal Oxygen requirement and is
supported by external to ASU LOX Oxygen storage. The CPU Unit is
sized for full CO.sub.2 gas volume from firing the coal and the
biomass in the Boiler/Turbine Unit A. Compressing and storing
emissions from firing the coal and the biomass results in the unit
having nominal negative emissions.
[0080] Boiler/Turbine Units B and C have one shared ASU unit sized
to 75% of both Boiler/Turbine Unit B and C nominal Oxygen
requirements and is supported by external to ASU LOX Oxygen
storage.
[0081] Boiler/Turbine Unit B fires 50% of coal and 50% of biomass
and operates with a load factor 0.75 over an operating period. The
CPU Unit for Boiler/Turbine Unit B is sized for full from firing
the coal only. CO.sub.2 gas volume attributable to firing the
biomass is vented via the stack. Compressing and storing emissions
from firing the coal results in the unit having nominal near zero
emissions. Boiler/Turbine Unit C fires only coal and operates with
load factor 0.75 over an operating period. The CPU Unit for
Boiler/Turbine Unit C is sized for full CO.sub.2 gas volume from
firing the coal. Compressing and storing emissions from firing the
coal results in unit having nominal near zero emissions.
[0082] Boiler/Turbine Unit D has Oxygen supplied from multiple ASU
units. The ASU units are different sizes, however the combined size
of the ASU units is sized to 75% of Boiler/Turbine Unit D nominal
Oxygen requirement and is supported by external to ASU LOX Oxygen
storage. The Boiler/Turbine Unit D fires 50% of coal and 50% of
biomass and operates with load factor 0.75 over an operating
period. The CPU Unit for Boiler/Turbine Unit D is sized for full
CO.sub.2 gas volume from firing the coal and the biomass.
Compressing and storing emissions from firing the coal and the
biomass results in unit having nominal negative emissions.
[0083] In all presented possible arrangements the electrical energy
required to power the ASU unit is preferably supplied from a
renewable energy source or a low cost energy source and is
decoupled from the Boiler/Turbine Unit operation.
* * * * *