Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
SYSTEM AND METHODS FOR INTEGRATION OF CONCENTRATED SOLAR
STEAM GENERATORS TO RANKINE CYCLE POWER PLANTS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to apparatuses and
systems that integrate a concentrated solar heating system
for steam generation to a steam cycle power plant, and
methods to operate the resulting hybrid solar-fuel fired
or heat recovery Rankine cycle power plant.
Description of Related Art
In a known concentrated solar power system, a solar
receiver comprising multiple heat panel tube arranged in
the top portion of a solar tower collector heats the molten
salt received from a cold storage tank, which is sent to a
hot storage tank. The superheated steam is obtained in a
sequence of heat exchangers, pre-heater, boiler and super-
heater, between water received from boiler feed water pumps
and the molten salt in a two-fluid heat transfer counter-
flow loop to drive a Rankine cycle power block. An example
of such a system is disclosed in US2013/0192586 Al.
In another known configuration, superheated steam is
raised directly in multiple-pass, once-through, direct
steam generation solar absorption devices. Such a
configuration is shown in US 2011/0126824 Al in which pre-
heated water flow is pressurized by a booster feed pump
into a multi pass receiver formed by an array of multiple
parallel tubes that absorbs the solar irradiation
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concentrated by linear Fresnel reflector system.
US 2013/0118419 Al discloses an embodiment describing
the technology of the heat exchanger shell-tube, U-shaped
pipe bundle type, receiving water as a shell-side fluid and
thermal oil or molten salt as a pipe-side fluid. The
entrance pre-heated water is evaporated by thermal contact
with a heated heat transfer fluid which has been heated by,
at least a solar tower, a linear Fresnel or a parabolic
trough collector system.
In the Patent Application US 2011/0247335 Al, a
combined cycle power plant including a heat recovery steam
generator is provided wherein a high pressure (HP) steam
generation section comprises a heating surface which can
be operated as a once-through evaporator heating surface,
known as the Benson principle.
Patent Application Publication US 2009/0241860 Al
discloses the application of the principles of a HP steam
generation system, once-through or supercritical furnace.
Accordingly, water-steam separating equipment such as steam
drums or vertical separators, as well as downcomers, are
not required during normal operation, however, vertical
separators are typically supplied and used during start-up
and low load operation.
All publications referred to herein are incorporated
by reference to the extent not inconsistent herewith for
purposes of meeting the written description and enablement
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requirements of Section 112 of the U.S. Patent Code.
Summary
Systems and apparatuses are provided for the
integration of Rankine cycle power plants to a concentrated
solar heating system.
The invention described herein includes methods of
designing and retrofitting steam boilers of a Rankine cycle
power plant in order to utilize an additional supply of
saturated and superheated steam generated by the
concentrated solar heating system.
According to advantageous method of operation
described herein a concentrated solar boiler system can be
integrated to a Rankine cycle power plant and can be
dispatched simultaneously during the period of the day when
the solar heat is available as Direct Normal Irradiance
(DNI). The fuel consumption in the steam boiler of the
Rankine cycle power plant or a combustion turbine in a
combined cycle power plant can be reduced by a feedback
control method based on process state variable inputs such
as: DNI, steam pressure, temperature, mass flow rate and
steam quality.
In a first aspect of the present disclosure, an
apparatus for increasing the saturated steam generation in
a steam boiler by means of solar energy collected via
concentrated solar heating system, comprises:
(i) a water passage configured to convey pressurized
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water to the pre-heater stage of the solar boiler;
(ii) a pre-heater stage in the solar boiler configured
to increase the feed water temperature up to its boiling
point;
(iii) an evaporation stage, fluidly connected to the
pre-heater stage in the solar boiler meant by design to
evaporate the preheated feed water to produce steam which
the quality is lower than 95%;
(iv) a mixed steam-water fluid passage configured to
convey the steam flow generated by evaporation stage to the
entrance of each boiler tube, meant by design to operate
with quality steam lower than 15%;
(v) a first circulation stage, wherein separated
saturated steam is directed to the super-heater stage and
the hot water re-enters the circulation process;
In a second aspect of the present disclosure, an
apparatus for increasing the temperature of the steam at
the entrance of the superheater by means of solar energy
in a steam boiler, comprises:
(i) a saturated steam passage configured to convey the
steam from a steam boiler to a solar heating system, wherein
the solar energy is transferred to the steam flow;
(ii) a superheated steam passage configured to return
the superheated steam from a solar heating system to the
entrance of a superheating stage of the boiler; wherein
attemperators/de-super-heaters valves control the
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temperature of superheated steam;
In a third aspect of the present disclosure an
apparatus for raising additional saturated steam by means
of recovering the residual heat from flue gas in a hot path
flow in the steam boiler, comprises:
(i) a flue-gas-to-Heat Transfer Fluid (HTF) heat
exchanger in the hot gas path of the steam boiler,
configured by design to transfer the heat from flue gas of
a steam boiler to the HTF circuit;
(ii) a HTF-to-water heat exchanger, fluidly connected
to a flue-gas-to-HTF heat exchanger meant by design to
evaporate the preheated feed water to produce steam which
the quality is lower than 95%;
(iii) a fluid passage circuit configured to convey the
HTF from a flue-gas-to-HTF heat exchanger to HTF-to-water
heat exchanger.
In a forth aspect of the invention, there is provided
a method of operating a Rankine power plant integrated to
a solar heating system according to the use of apparatuses
provided in the first, second and third aspects of the
present invention, comprising:
(i) Diverting a portion of the mass flow of the
pressurized feed water from the steam boiler to the
entrance of a solar heating system for raising saturated
steam in accordance with the available solar heat input,
Direct Normal Irradiance (DNI), accordingly to the first
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aspect of this invention;
(ii) Setting the fuel consumption of a steam boiler,
considering the additional saturated steam generated by
solar means, accordingly to the first aspect of this
invention;
(iii) Increasing the temperature of the steam at the
entrance of the super-heater in a steam boiler, in
accordance with the second aspect of this invention.
The present invention is related to a system for
integrating fluidly and functionally a Rankine cycle power
plant to a concentrated solar steam generator in a hybrid,
direct steam generation, fuel-fired boiler, cogeneration
plant, comprising: a solar heating section (110)
comprising: at least one solar receiver (115) configured
to capture solar radiation and thereby generate saturated
steam; at least one primary solar super-heater (111)
configured to capture solar radiation and thereby generate
superheated steam; (b) a solar steam transfer circuit
(130), configured to convey the saturated and superheated
steam generated by the solar heating section (110) to at
least, one fuel-fired boiler (120); (c) at least one fuel-
fired boiler (120), comprising an evaporation section (150)
configured to raise saturated steam and superheated steam
in a natural circulation evaporation loop; at least one
primary super-heater (127) configured to convey superheated
steam from the evaporation section (150) to a cogeneration
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section (140); (d) a cogeneration section (140) configured
to partially expand the superheated steam in a (HP) turbine
(142) and further expand re-heated steam in a (LP) turbine
(143); and wherein the fuel consumption of the fuel-fired
boiler (120) can be adjusted based on effective amounts of
saturated and superheated steam produced in the solar
heating section (110).
The system wherein the solar steam transfer circuit
(130) comprises a steam injection valve (132) configured
to control flow of the superheated steam received from the
at least, one primary solar super-heater (111); a steam
mixer valve (131) that controls flow from at least, one
solar receiver (115); and at least one steam mixer injector
(133) configured to attemperate the superheated steam
received from steam injection valve (132) with the
saturated steam received from saturated steam mixer valve
(131).
The system comprising a plurality of boiler tubes (154)
in a harp tube bundle (158) of the evaporation section
(150); a harp header (152) of the evaporation section
(150), the harp header (152) configured to inject the steam
coaxially to the water flow at the entrance of each boiler
tube (154) in the harp tube bundle (158); a steam injector
(135) configured to convey steam from the at least one
steam mixer injector (133) into the harp header (152) of
the evaporation section (150); and wherein the temperature
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of the steam exiting harp tube bundle (158) of the
evaporation section (150) can be set up to a value in a
range of 5 C to 10 C above the temperature of the saturated
steam raised in the plurality of boiler tubes (154) of the
evaporation section (150).
The system comprising a booster feed-water pump (136)
configured to raise the pressure of the water entering the
solar heating section (110); a steam drum (156) of the
evaporation section (150); and wherein the operation
pressure in the solar heating section (110) is controlled
in a range of 5 to 10 bar (absolute) above the operation
pressure of the fuel-fired boiler (120) thereby creating
and sustaining an upward velocity component of the low
quality steam-water mixture flow entering the harp header
(152) coaxially to the water flow at the entrance of each
boiler tube (154) in the harp tube bundle (158); and wherein
the saturated steam is thereby routed from the harp tube
bundle (158) into the steam drum (156).
The system comprising cyclone separators (159) located
inside the steam drum (156); and wherein the saturated
steam and hot water mixture from the plurality of boiler
tubes (154) of the harp tube bundle (158) is separated in
the steam drum (156) into saturated steam and hot water.
The system comprising at least one downcomer (151) of
the evaporation section (150); and wherein the difference
of weights between the water column in the downcomer (151)
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and water/steam mixture column in the plurality of boiler
tubes (154) results in buoyancy forces that create and
sustain the upward flow of low quality steam, routing the
saturated steam into the steam drum (156), completing the
evaporation loop of the evaporation section (150).
The system comprising a steam mixer (139) upstream of
the primary super-heater (127); and wherein additional
superheated steam generated in the solar heating section
(110) is injected in the fuel-fired boiler (120).
The present invention is further related to a system
for integrating fluidly and functionally a Rankine cycle
power plant to a concentrated solar steam generator in a
hybrid, HTF-to-water-steam generation system, fuel-fired
boiler, cogeneration plant, comprising a solar heat
transfer loop (210) comprising at least one a solar
receiver (214) configured to collect solar irradiation and
transfer thermal energy to a heat transfer fluid (HTF); (b)
a fuel-fired boiler (220) comprising at least one
evaporation section (250) configured to raise saturated
steam in a natural circulation loop; and at least one
primary super-heater (224) configured to receive
superheated steam from the at least one evaporation section
(250); (c) an energy storage system (230) comprising at
least one hot storage tank (231); and at least, a cold
storage tank (232); (d) a cogeneration section (240)
comprising a (HP) turbine (242);
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a (LP) turbine (243); and wherein superheated steam
partially expands in a (HP) turbine (242) and re-heated
steam further expands in a (LP) turbine (243); and (e) a
flue gas heat recovery circuit (260) comprising a flue gas
path (228); at least one steam re-heater (263) configured
to re-heat the HTF with recovered residual heat out of the
flue gas in the hot flue gas path (228); and wherein fuel
consumption of the fuel-fired boiler is reduced by pumping
a portion of the HTF in the cold storage tank (232) to the
hot storage tank (231) through the at least one a solar
receiver (214).
The system wherein the at least one fuel-fired boiler
(220) comprising a steam re-heater (226) configured to
reheat partially expanded steam exiting the cogeneration
section (240); an economizer (227) configured to preheat
pressurized water; and a feed water pump (221) configured
to pressurize condensate returning from the cogeneration
section (240) to the operation pressure of the fuel-fired
boiler (220).
The system wherein the at least one evaporation section
(250) comprises a steam drum (251) configured to connect
to the economizer (227) and receive the water-steam mixture
through tubing (257); a downcomer (252) located downstream
of the steam drum (251) and configured to connect to water
distribution tubing (253); a re-boiler (218) connected to
the water distribution tubing (253) and configured as a
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shell-water, HTF-in-tube heat exchanger; a harp tube bundle
(256) comprising: a plurality of boiler tubes (254)
connected to the re-boiler (218); and an upper header
(255) connected to tubing (257) and configured to connect
to the lower end of the boiler tubes (254); and wherein the
at least one re-boiler (218) raises additional saturated
steam in the steam-water circulating evaporation section
(250).
The system wherein the solar heat transfer loop (210),
comprises at least one HTF super heater (217) configured
to pre-heat the saturated steam received from steam drum
(251) by means of solar energy contained in the hot HTF
flow received from a HTF header (236).
The system comprising at least one secondary super-
heater (225) configured to pre-heat steam entering primary
super-heater (224); at least one HTF primary super-heater
(216) configured to transfer the HTF flow from HTF header
(236) to the superheated steam conveyed from secondary
super-heater (225); and wherein super-heated steam from
primary super-heater (224) enters HP turbine (242)
producing power.
The system comprising a re-heating steam circuit (270)
comprising a low pressure steam passage (271) configured
to receive steam exiting the HP turbine (242); at least one
HTF re-heater (215) configured to transfer the HTF flow
from HTF header (236) to the low pressure steam passage
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(271); and wherein the low pressure steam passage (271)
passes low pressure superheated steam through the flue gas-
to-steam re-heater (226) resulting in a high temperature
low pressure superheated steam which is directed to the LP
turbine (243).
The system comprising at least one attemperator valve
(219) located downstream from the HTF header (236) and
connected to the exit of at least one HTF re-heater (215)
and to the exit of HTF primary super-heater (216); and
wherein the temperature of the HTF at the entrance to the
at least one HTF super heater (217) is increased.
The present invention is further related to a system
for integrating fluidly and functionally a concentrated
solar, HTF-to-water-steam generation system to a heat
recovery steam generation (HRSG), combined cycle power
plant, comprising a solar heat transfer circuit (310)
comprising at least, a solar receiver (313), configured to
collect the solar irradiation and transfer the solar
thermal energy to a Heat Transfer Fluid (HTF); a Heat
Recovery Steam Generator (HRSG) (320) comprising at least,
a HP steam generation section (370); a solar heat storage
system (330) comprising an HTF IP evaporator (312); at
least one a hot storage tank (332) configured to receive
hot HTF from the solar receiver (313); and a cold storage
tank (331) configured to receive the returned cold HTF from
the HTF IP evaporator (312); a combustion turbine (CT)
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section (380) comprising at least an electric generator
(385); an air compressor (382); a gas turbine (383); and
a combustion chamber (381); a steam turbine section
(340) comprising at least one (HP) turbine (343) configured
to expand the HP superheated steam raised in a HP steam
generation section (370); and wherein the heat from exhaust
gas from the combustion turbine CT section (380) is
recovered and transferred to the water steam flow of the
HP steam generation section (370).
The system wherein the HP steam generation section
(370) of the HRSG (320) comprises a HP feed-water pump
stage (323); a HP water pre-heater (378) connected to the
HP feed-water pump stage (323); a first stage HP
evaporation section, comprising a HP primary evaporator
(374) supplied by the HP water pre-heater (378); and a
downcomer (376) configured to direct flow from the HP
primary evaporator (374) downward to a water distributor
(377); a second stage HP evaporation section, comprising a
HTF HP evaporator (314) supplied by the water distributor
(377); and a HP secondary evaporator (375) supplied by the
a HTF HP evaporator (314); a vertical water-steam separator
(371) connected to the HP secondary evaporator (375); a HTF
HP super-heater (315) configured to receive steam from the
vertical water-steam separator (371); a return line (379)
configured to receive water from the vertical water-steam
separator (371) and connected to the first stage HP
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evaporation section; and a HP super-heater (372) connected
to the HTF HP super-heater (315); and wherein the HP
saturated steam is superheated and directed to the HP steam
turbine (343).
The system wherein HRSG (320) comprising an IP steam
generation section (360), comprising an IP feed-water pump
stage (322); an IP water pre-heater (367) connected to the
IP feed-water pump stage (323); an IP steam drum (361)
supplied by the IP water pre-heater (367); a downcomer
(362) configured to have feed-water from the IP steam drum
(361) flow downward due to natural convection; a water
distributor (363) configured to supply downward flow from
the downcomer (362) to the HTF IP evaporator (312); a harp
tube bundle comprising a plurality of boiler tubes (364)
connected to the HTF IP evaporator (312); a harp collector
(366) configured to supply IP saturated steam raised by
both solar and hot exhaust gas recovery to the IP steam
drum (361); a HTF-to-IP-steam pre-heater (311) configured
to transfer the solar heat contained in a hot HTF flow to
the saturated steam received from IP steam drum (361); an
IP super-heater (369) configured to receive resulting IP
superheated steam heated by HTF-to-IP-steam pre-heater
(311); and wherein IP super-heated steam from IP super-
heater (369) is conveyed to IP steam turbine (342) and
wherein steam expansion produces mechanical work which is
converted into electrical energy.
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The system wherein HRSG (320) comprising a LP steam
generation section (350), comprising a LP feed-water pump
(321); a LP water pre-heater (357) configured to pre-heat
the feed-water flow; a LP steam-water loop connected to the
LP water pre-heater (357), the LP steam-water loop
comprising a LP steam drum (351); a downcomer (352)
configured to have feed-water from the LP steam drum (351)
flow downward due to natural convection; a feed line (353)
connected to the downcomer (352); an IF steam injection
header (317) configured to receive IF steam from the IP
steam drum (361); a harp tube bundle comprising a harp
header (355) connected to the downcomer (352) through feed
line (353) and connected to injection header (317) to
receive IP steam from the IP steam drum (361); a plurality
of boiler tubes (354) connected to the harp header (355);
and a harp collector (356) connected to the LP steam drum
(351); a LP super-heater (359) configured to receive
saturated steam from the LP steam drum (351); and wherein
LP super-heated steam from LP super-heater (359) is
conveyed to LP steam turbine (341) and wherein steam
expansion produces mechanical work which is converted into
electrical energy.
The system wherein the (HP) steam generation section
(370) comprises a high pressure supercritical steam
generating system, which can be configured by design with
water steam separating equipment such as a vertical water-
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steam separator (371) and downcomer (376) be used when
typically required during start-up or partial load
operation and be capable to operate as a once-through or
supercritical steam generator when solar heat is available.
These and other features, advantages and improvements
according to this invention will be better understood by
reference to the following detailed description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be
described by way of example only, with reference to the
accompanying drawings in which:
Figure 1 (FIG. 1) is a schematic diagram of a hybrid
concentrated solar heating system, direct steam generation,
integrated to a fuel-fired boiler in a Rankine power plant
in accordance with the present invention;
Figure 2 (FIG. 2) is a schematic diagram of a hybrid
concentrated solar heating system, heat transfer fluid,
integrated to a fuel-fired boiler in a Rankine power plant
in accordance with the present invention; and
Figure 3 (FIG. 3) is a schematic diagram of a hybrid
concentrated solar heating system, HTF-to-water-steam
generation system, integrated to a three pressure, Heat
Recovery Steam Generation (HRSG), in a combined cycle plant
in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
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The invention described herein relates to apparatuses,
systems and methods for integrating and operating a
concentrated solar heating system for steam generation to
a Rankine cycle power plant. Methods are disclosed herein
for designing and retrofitting a steam boiler in order to
efficiently utilize a complementary steam source, and then
integrating both saturated and superheated steam generated
by solar radiation collecting means into a Rankine cycle
plant.
In one embodiment, a hybrid concentrated solar -
Rankine power plant may include a fossil or biomass fuel-
fired steam generator, or any other type of fuel-fired
boiler using any available fuel. Further, a combined cycle
power plant may use exhausts of a gas turbine to generate
steam in a heat recovery steam generator (HRSG), wherein
an embodiment of the HRSG may also comprise a supplementary
duct firing device.
The solar steam generator may be a concentrated solar
heating system of any variety that uses mirrors to reflect
and concentrate solar irradiation onto heat receivers
comprising a tube or an array of tubes within a working
fluid such as water, molten salt or any heat transfer fluid
(HTF) in order to exchange solar heat with the in-tube HTF
flow. The solar concentrator architecture may be a
parabolic trough system, a linear Fresnel reflector system,
a central tower receiver system, or another method or
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system of concentrating light by which solar energy is
collected as heat in a solar radiation absorption device.
In an embodiment of the invention evaporator and super-
heater stages may comprise one or more solar radiation
absorption device in which the pre-heated feed water
transferred from the steam boiler is directly boiled by
direct contact with a heated element in the solar radiation
absorption device.
Alternatively, in another embodiment, a pre-heater, an
evaporator and a super-heater stage may comprise one or
more heat exchangers with a heated HTF such as thermal oil
or molten salt, which has been heated with solar energy
collected by the solar heating system.
In a further embodiment, it is comprised one or more
heat storage tanks wherein hot and cold HTF such as molten
salt can be stored. The cold transfer fluid is heated with
solar energy collected by the solar heating system and
stored in the hot tank. During the hours when the solar
irradiation is not available, the hot transfer fluid and
pre-heated water can be directed through heat exchangers
to raise saturated and superheated steam.
Referring now to the invention in more detail, in Fig.
1 there is shown an exemplary hybrid solar direct steam
generation fuel-fired boiler, Rankine cycle, cogeneration
plant, generally designated hybrid plant (100) comprising:
a solar heating section (110), wherein the solar energy is
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collected and transferred to the working fluid, which is
pressurized water; a fuel-fired boiler (120), wherein
superheated steam is generated by means of burning fuel
including an evaporation section (150) wherein saturated
steam is generated in a natural circulation loop; a solar
steam transfer circuit (130) which conveys the saturated
and superheated steam generated by solar means to a fuel-
fired boiler (120); a cogeneration section (140), wherein
the superheated and re-heated steam are expanded in a
turbine, generating power and industrial process steam; and
an industrial steam consumer (160), wherein the low
enthalpy steam exiting the generation section (140) is the
heated working fluid of the industrial process.
The solar heating section (110) comprises: a condensate
valve (119) which regulates the mass flow of the condensate
diverted from the entrance of the economizer (126), in the
fuel-fired boiler (120); a solar receiver (115), which
raises saturated steam by concentrating solar energy means;
a water-steam separation tank (118), wherein the saturated
steam is separated from pressurized water and is connected
to a saturated steam mixer valve (131); a condensate pump
(116), which raises the pressure of the circulating water
returned from water-steam separation process; a primary
solar super-heater (111) and a secondary solar super-heater
(114), wherein the saturated steam is superheated; a water
injector (112) and an attemperation valve (113) which
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control the temperature of the superheated steam; and a
superheated steam valve (117) which controls the mass flow
of the superheated steam generated by solar means.
The fuel-fired boiler (120) comprises: an evaporation
section 150, wherein saturated steam is raised from pre-
heated water in a natural circulation evaporation loop; a
feed-water-pump (121), wherein feed-water is pressurized
up to the operation pressure of the fuel-fired boiler
(120); a flue-gas-to-water and steam heat exchanging
circuit including an economizer (126), wherein the flue gas
heat is transferred to the high pressure feed-water, a pre-
heated water line (123) which conveys the pre-heated water
to an evaporation section 150, a steam re-heater (129)
wherein the flue gas heat is transferred to the low pressure
superheated flow and the re-heated steam returns to a
cogeneration section (140), a secondary super-heater (128)
wherein saturated steam is superheated; a primary super-
heater (127) wherein superheated steam temperature is
raised up to the design operation point; a superheated
steam line (125) which conveys the steam to a turbine
located in a cogeneration section (140); and a de-super-
heating circuit including attemperator valve (122) which
controls the pre-heated water flow for attemperation
process and an attemperation injector (124) which reduces
the temperature of the super-heated steam by means of
evaporating the hot water injected into the steam flow.
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The water-steam loop in the evaporation section (150)
comprises: a steam drum (156) which connects to the
economizer (126) through the pre-heated water line (123)
and receives the water-steam mixture through a steam-water
line (157); a harp tube bundle (158) including a harp
collector (153), boiler tubes (154) and a harp header
(152), which connects to the steam distribution header
(135) and receives steam from a solar steam injection
circuit (134).
The solar steam transfer circuit (130) comprises: a
steam mixer (139) located upstream of the primary super-
heater (127) and a super-heated steam line (138) which
connects the superheated steam valve (117) and
conveys
super-heated steam generated by solar means to the steam
flow exiting an attemperation injector (124); a pressurized
feed-water circuit including a feed-water valve (137),
which controls the water mass flow entering the solar
heating section (110) and locates downstream of a feed-
water-pump (121), a booster feed-water pump (136) which
increases the pressure of the water flow upstream of a
condensate valve (119); a solar steam injection circuit
(134), including at least one steam injector (135) which
is installed in the harp header (152) for steam injection,
coaxially to the entrance flow of each boiler tube (154);
a steam injection valve (132), which controls the mass flow
of the steam diverted from a super-heated steam line (138),
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a saturated steam mixer valve (131) and, a steam mixer
injector (133) which attemperates the steam to be injected
in the harp tube bundle (158).
The cogeneration section (140) comprises: an electric
generator (141) in a single shaft connection with both the
high pressure (HP) turbine (142) and the low pressure (LP)
turbine (143); a steam condenser (146); condenser water-
cooling circuit (148), which dissipate the heat from
condensation process into the atmosphere; and a condensate
pump (149), which circulates the condensate through a de-
aerator (144).
The industrial steam consumer (160) connects to the LP
turbine (143) through a controlled extraction de-aerator
bleed-line (145) and the condensate from industrial process
returns to the de-aerator (144) and further is directed to
the feed water pump (121) located in the fuel-fired boiler
(120).
In more detail, still referring to the invention in
Fig. 1 the hybrid plant (100), can be operated when the
solar heat is not available by burning the primary fuel in
the fuel-fired boiler (120) which provides superheated
steam to a power block (140) and saturated steam to an
industrial steam consumer (160).
The steam expanded in the HP turbine (142) and LP
turbine (143) is directed to, at least, one condenser
(146), and the condensate re-enters the de-aerator (144)
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by means of a feed water pump (149) which raises the
condensate pressure up to the de-aerator designed operating
condition.
The boiler feed water pump (121) raises the pressure
of the water leaving the de-aerator (144) up to the fuel-
fired boiler (120) operational condition. The pressurized
water enters an economizer (126), wherein is pre-heated and
directed to the water recirculation system of the
evaporation section (150) via steam drum (156), flowing
downwards due to natural convection through the downcomer
(151). The high-pressure water enters a harp tube bundle
(158) via water distribution line (155), configured as a
fluid passage to convey the preheated water into a harp
header (152) to be evaporated in the boiler tubes (154).
The difference of weights between the water column in the
downcomer (151) and water/steam mixture column in the
boiler tubes (154) is a resultant of buoyancy forces which
creates and sustains the upward flow of the low-quality
steam, routing the saturated steam into the steam drum
(156), completing the evaporation loop.
The low-quality water/steam mixture produced in the
boiler tubes (154) is separated into saturated steam and
hot water by cyclone separators (159) located inside the
drum (156). The hot water close to its saturation
temperature flows by natural convection to the entrance of
the downcomer (151) in another turn of the circulation
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process.
The saturated steam is dried prior to exiting the steam
drum (156) and then, dried saturated steam is partially
superheated in the secondary super-heater (128) and further
in the primary super-heater (127), which is fluidly
connected to the HP steam turbine (142), the superheated
steam is partially expanded in the turbine and returned to
a re-heater (129) and is supplied to the LP turbine (143)
in which the steam is first expanded and partially bled to
de-aerator (144), through a bleed-line (145), secondly
expanded and partially bled to industrial steam consumer
(160) through process bleed-line (147) and directed to the
condenser (146), wherein heat is rejected to the ambient
air and condensate is further directed to the circulation
pump (149).
In the operation of a hybrid plant (100), when the
solar heat is available the feed water mass flow is
diminished at the entrance of the economizer (126), by
operating a feed-water valve (137) in order to set the
water mass flow entering the booster feed-water pump (136)
which raises the pressure of the water entering the solar
heating section (110) up to the design operation pressure.
The difference between the operation pressure in a
solar heating section (110) and in a fuel-fired boiler
(120) is controlled, in a range of 5 to 10 bar (absolute)
in order to allow the saturated and superheated steam
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generated by solar means to be injected in fuel-fired
boiler (120).
The feed water pressurized by booster feed-water pump
(136) and regulated in pressure by the condensate valve
(119) is mixed with the water flow of the solar boiler
circulation loop pumped by a condensate pump (116) and the
resultant water mass flow is boiled in the solar receiver
(115).
The low-quality steam-water mixture enters water-steam
separation tank (118), and the saturated steam can flow
either towards the secondary solar super-heater (114) or
through the steam mixer valve (131) which regulates the
saturated steam mass flow to be injected in the solar steam
injector (135). The superheated steam mass flow leaving the
solar boiler section (110) via steam transfer line (138)
is controlled by steam injection valve (132) and
superheated steam valve (117). The temperature of the mixed
steam entering the steam injector (135) can be set up to a
value in a range of 5 C to 10 C above the temperature of
the saturated steam boiled inside the boiler tubes (154).
In an advantageous method of entering the saturated
steam generated by the solar boiler into the fuel-fired
boiler (120), the steam injection circuit (134) conveys the
steam to the steam injector (135), which injects the steam
generated by solar means into the harp header (152),
coaxially to the water flow at the entrance of each boiler
CA 3055360 2019-09-13
tube (154), in the harp tube bundle (158).
In an advantageous method of entering the superheated
steam generated by the solar boiler into the fuel fired
boiler, the superheated steam generated in the super-heater
(111) is conveyed by the superheated steam line (138) to
the steam mixer (139) installed upstream of the primary
super-heater (127).
The fuel consumption of the fuel-fired boiler (120) can
be adjusted based on the effective amounts of saturated and
superheated steam produced in the solar heating section
(110), according to the solar resource, DNI.
Referring now to the invention in more detail, in Fig.
2 there is shown an exemplary hybrid solar HTF-to-water-
steam generation system integrated to a fuel-fired boiler,
Rankine cycle, cogeneration plant, generally designated
hybrid HTF-to-steam plant (200) comprising: a solar energy
section including a solar heat transfer loop (210) and a
heat storage stage (230); a heat recovery circuit (260); a
fuel fired boiler (220) including an evaporation section
(250); a cogeneration section (240) including an electric
generator (241), which produces electric energy; a re-
heating steam circuit (270); and an industrial steam
consumer (290).
The solar heat transfer loop (210) comprises: a solar
receiver (214), which collects the solar irradiation and
transfers the thermal energy to a heat transfer fluid -
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CA 3055360 2019-09-13
HTF; a HTF re-heater (215), which connects to the HTF header
(236) and transfers the solar energy contained in the hot
HTF to superheated, low pressure steam flow in the re-
heating steam circuit (270); a HTF primary super-heater
(216), which transfers the solar energy contained in the
hot HTF received from HTF header (236) to the super-heated
steam exiting secondary super-heater (225), pre-heating the
steam entering the primary super-heater (224); a HTF-to-
saturated steam, namely the HTF super heater (217), which
pre-heats the saturated steam received from steam drum
(251) by means of solar energy contained in the hot HTF
flow received from HTH header (236), regulated by
attemperator valve (219); a HTF-to-water re-boiler (218),
which is connected to the cold storage tank (232) through
the HTF return line (239) in the energy storage system
(230) and also connects to the downcomer (252) through
water distribution tubing (253) and is located upstream of
the boiler tubes (254) in the evaporation section (250).
The receiver valve (211) is located between the cold
HTF header (235) and the solar receiver (214), which is
connected to the hot storage tank (231).
In one HTF circuit meant by design to control the HTF
temperature in the entrance of a HTF-to-steam heat
exchanger, namely the HTF re-heater (215), an attemperation
valve (213) is located downstream of the cold HTF header
(235), and also connects to the hot HTF line downstream of
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CA 3055360 2019-09-13
the hot HTF header (236).
In another independent circuit to control the HTF
temperature in the entrance of the HTF primary super-heater
(216), an attemperation valve (212) is located downstream
of the cold HTF header (235) and also connects to the hot
HTF line downstream of the hot HTF header (236).
In a further independent circuit to increase the
temperature of the HTF at the entrance of the HTF super
heater (217), an attemperator valve (219) is located
downstream of the hot HTF header (236) and also connects
to the exit of the HTF re-heater (215), which further
connects to the exit of the HTF primary super-heater (216).
The fuel-fired boiler (220) comprises: a flue gas path
(228) and a circulating evaporation section (250). The flue
gas path (228) comprises: a furnace (222) wherein the
mixture of combustion air and fuel is burned and resultant
hot combustion products pass through a sequence of heat
exchangers flue-gas-to-working fluid (water, steam or HTF)
including: the screening tubes (223), wherein pre-heated
water is boiled to saturated steam; a primary super-heater
(224) and a secondary super-heater (225), wherein saturated
steam is superheated; a HTF steam re-heater (263), wherein
HTF from cold storage tank (232) is heated by flue gas in
the boiler (220); a steam re-heater (226), wherein
partially expanded steam exiting the cogeneration section
(240) is re-heated; an
economizer (227), wherein
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CA 3055360 2019-09-13
pressurized water is pre-heated; and a feed water pump
(221), wherein condensate returning from the cogeneration
section (240) is pressurized up to operation pressure of
the fuel-fired boiler (220).
The water-steam loop in the evaporation section (250)
comprises: a steam drum (251) which connects to the
economizer (227) and receives the water-steam mixture
through tubing (257); a harp tube bundle (256) including
the boiler tubes (254) connected to one upper header (255);
a shell-water, HTF-in-tube heat exchanger, namely the re-
boiler (218), which connects to the lower end of the boiler
tubes (254); a downcomer (252) located downstream of the
steam drum (251) and connected to the re-boiler (218) by a
water distribution tubing (253).
The energy storage system (230) comprises: a hot
storage tank (231), which receives the heated HTF from
solar receiver (214); a cold storage tank (232) which
receives the returned cold HTF from re-boiler (218); a HTF
pump (233) which pressurizes the cold HTF into the cold HTF
header (235); a HTF pump (234) which pressurizes the hot
HTF into the HTF header (236).
The cogeneration section (240) comprises: an electric
generator (241) in a single shaft connection with both the
HP turbine (242) and the LP turbine (243); a steam condenser
(246); water-to-air heat sink (245), which dissipates the
heat from condensation process into the atmosphere; and a
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CA 3055360 2019-09-13
condensate pump (249), which circulates the condensate
through a de-aerator (244). The industrial steam consumer
(290) connects to the LP turbine (243) through a controlled
extraction bleed line and the condensate from industrial
process returns to the de-aerator (244) and further is
directed to the feed water pump (221) located in the fuel-
fired boiler (220).
The flue gas heat recovery circuit (260) comprises: a
HTF valve (261) which controls the flow of the cold HTF and
is located downstream of a cold HTF header (235); and a hot
flue-gas-to-HTF heat exchanger, namely the steam re-heater
(263), which connects to the HTF line exiting the HTF super
heater (217).
The re-heating steam circuit (270) comprises: a low
pressure steam passage (271) connecting the exit of the HP
turbine (242) to the entrance of a HTF-to-steam heat
exchanger, the HTF re-heater (215), which is also located
in the solar heat transfer loop (210), downstream of the
attemperation valve (213) and upstream of the HTF super
heater (217); a flue-gas-to-steam heat exchanger, the re-
heater (226), also located in the hot path gas (228)
downstream of the secondary superheater (225) and upstream
of a pre-heater (227); a low-pressure-high-temperature-
steam-passage (273), directing the re-heated steam to the
entrance of the LP turbine (243).
In more detail, still referring to one advantageous way
CA 3055360 2019-09-13
of implementing the invention depicted in Fig. 2 the hybrid
HTF-to-steam plant (200), can be operated even when the
solar heat is not available by burning the primary fuel in
the fuel-fired boiler (220) which provides superheated
steam to the power and industrial steam co-generation
section (240).
The HTF contained in the cold storage tank (232) can
be pressurized by HTF pump (233) and the resultant HTF mass
flow can be regulated by HTF valve (261) through the cold
HTF header (235). The cold HTF flows through the feed line
(262), entering the heat exchanger flue gas-to-HTF heat
recovery (263) located in flue gas path (228), downstream
of the secondary super-heater (225) in the fuel-fired steam
boiler (220). The resultant hot HTF flows through HTF feed
line (264) entering the re-boiler (218), wherein additional
saturated steam is raised in the steam-water circulating
evaporation section (250) without using solar energy. The
cold HTF flow resultant of the heat exchanging process in
re-boiler (218) returns to the cold storage tank (232)
completing a flue gas-to-HTF, close loop, heat recovery
saturated steam generation mode of operation disclosed
herein.
In a natural convective circulation boiler, the pre-
heated feed-water enters the steam-water circulating
evaporation section (250) via steam drum (251), flowing
downwards due to natural convection through the downcomer
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CA 3055360 2019-09-13
(252) in another turn of the natural circulation process.
The pre-heated water enters into the water distribution
tubing (253), configured as a fluid passage to convey the
pre-heated water into HTF-to-water heat exchanger, the re-
- boiler (218). When a steam boiler (220) is operating in a
very low capacity factor the natural circulation in the
evaporation section (250) is sustained by buoyancy forces
resultant of the difference between weight component of the
water columns in the downcomer (252) and weight component
of the water/steam mixture column in a boiler tube (254).
The additional saturated steam generated by re-boiler (218)
creates and sustains the upward flow of the low-quality
steam-water mixture, routing the saturated steam into the
steam drum (251), completing the evaporation loop.
In one advantageous method of operating a hybrid HTF-
to-steam plant (200), when the solar heat is available, a
portion of the HTF contained in a cold storage tank (232)
is pumped by HTF pump (233) through a solar receiver (214)
and the resultant hot HTF is transferred to a hot storage
tank (231). A fuel-fired boiler (220) can operate in a low
capacity factor under reduced fuel consumption mode and
additional saturated steam can be generated in the re-
boiler (218), superheated in HTF super heater (217) or in
a HTF primary super-heater (216) and further re-heated in
HTF re-heater (215) by means of solar energy transferred
from HTF to the water-steam loop within a fuel-fired boiler
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CA 3055360 2019-09-13
(220).
A HTF pump (234) pressurizes a portion of the HTF
contained in a hot storage tank (231) through the HTF header
(236) and the resultant HTF flow is further distributed
among the heat exchangers in the solar heat transfer loop
(210) which transfers the solar heat to both boiler (220)
and re-heating steam circuit (270) by means of HTF-to-
water-steam heat exchangers.
In the re-boiler (218) a portion of the hot water
conveyed from downcomer (252) by water distribution tubing
(253) is evaporated and the low quality saturated steam-
water mixture is conveyed to the entrance of each one of
the boiler tubes (254) by convection in the natural
circulation, evaporation section (250). The saturated steam
flows from the upper header (255) of the harp tube bundle
(256), through water-steam distribution tubing (257) to the
steam drum (251), wherein the saturated steam is separated
from water-steam mixture. In HTF super heater (217) the
solar energy in the HTF flow received from (216) and mixed
with the flow from HTF re-heater (215) is transferred to
the saturated steam flow leaving the steam drum (251) and
the resulting superheated steam flows to the secondary
super-heater (225). In HTF primary super-heater (216), the
solar heating in the HTF flow received from HTF header
(236) and attemperated by valve (212) is transferred to the
superheated steam conveyed from secondary super-heater
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CA 3055360 2019-09-13
(225). The resulting pre-heated steam is directed to
primary super-heater (224) and further enters HP turbine
(242) wherein expands producing power.
The low pressure superheated steam leaves (242) and
circulates through the re-heating steam circuit (270) via
low pressure steam passage (271) in a two-step re-heating
process comprising: a pre-heating pass through in a HTF re-
heater (215) wherein the solar heat contained in the HTF
received from the HTF header (236) is transferred to the
LP superheated steam; and a further pass through a flue
gas-to-steam re-heater (226) through low pressure steam
passage (272) resulting in a superheated steam which is
directed via a low-pressure-high-temperature-steam-passage
(273) to LP turbine (243).
Referring now to the invention in more detail, in Fig.
3 there is shown an exemplary hybrid concentrated solar
heating system, heat transfer fluid, integrated to a three
pressure, heat recovery steam generation, combined cycle
power plant, generally designated Hybrid HTF-to-steam
combined cycle plant (300) comprising: a solar energy
section including a solar heat transfer loop (310) and a
solar heat storage system (330); a Heat Recovery Steam
Generator (HRSG) (320) including: a Low Pressure (LP) steam
generation section (350); an Intermediate Pressure (IP)
steam generation section (360); a High Pressure (HP) steam
generation section (370); a Steam Turbine (ST) section
34
CA 3055360 2019-09-13
(340); and a Combustion Turbine (CT) section (380).
The solar heat transfer circuit (310) comprises: a
solar receiver (313), which collects the solar irradiation
and transfers the solar thermal energy to a Heat Transfer
Fluid (HTF); a HTF-to-steam heat exchanger, namely the HTF
HP super-heater (315) which is located downstream of the
hot HTF pump (334) and transfers the solar heat contained
in the hot HTF flow pumped from a hot storage tank (332)
mixed with cold HTF provided by the attemperation valve
(336) to the HP steam received from vertical water-steam
separator (371), which is super-heated in the HP steam
super-heater (372) and further directed to a Steam Turbine
(ST) section (340); a HTF-to-pressurized-hot-water heat
exchanger, namely the HTF HP evaporator (314) which is
located downstream of the solar heat storage system
(330)and transfers the solar energy contained in the hot
HTF flow to the pre-heated water passing through the HP
steam generation section (370); a HTF-to-saturated-steam
heat exchanger, namely the HTF-to-IP-steam pre-heater
(311), which is located downstream of the solar heat
storage system (330) and transfers the solar heat contained
in a hot HTF flow to the saturated steam received from IP
steam drum (361); a HTF-to-pressurized-hot-water heat
exchanger, namely the HTF IP evaporator (312) which is
located upstream of the cold HTF storage tank (331) and
transfers the solar energy contained in the hot HTF to a
CA 3055360 2019-09-13
pre-heated-pressurized-hot-water received from downcomer
(362) through LP water distributor (363).
In one HTF circuit meant by design to control the HTF
temperature in the entrance of a HTF-to-IP-steam pre-heater
(311), an attemperation valve (337) is located downstream
of the cold HTF pump (333), and also connects to the hot
HTF line downstream of the hot HTF pump (334).
In another independent circuit to control the HTF
temperature in the entrance of a HTF HP super-heater (315),
an attemperation valve (336) is located downstream of the
cold HTF pump (333), and also connects to the hot HTF line
downstream of the hot HTF pump (334).
In a further independent IP saturated steam circuit
(316), the additional steam flow generated by means of
solar energy is regulated by an IP steam valve (318) and
conveyed to an IP steam injection header (317), which is
installed coaxially to each boiler tube in the water
distributor harp header (355).
The Heat Recovery Steam Generator (HRSG) (320)
comprises: a chimney stack (324); a boiler feed-water
pumping stage including a LP feed-water pump (321), an IP
feed-water pump (322) and a HP feed-water pump (323); and
a hot gas path (328) wherein the heat still available in
exhaust gas from combustion turbine CT section (380) is
recovered and transferred to the water-steam flow; a HP
steam generation section (370), an IP steam generation
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CA 3055360 2019-09-13
section (360); and a LP steam generation section (350).
The energy storage system (330) comprises: a cold
storage tank (331), which receives the returned cold HTF
from HTF IP evaporator (312); a hot storage tank (332),
which receives the returned hot HTF from solar receiver
(313); a HTF pump (333) which pressurizes and circulates
the cold HTF through the solar receiver (313); a HTF pump
(334) which pressurizes the HTF flow through a solar heat
transfer circuit (310); an attemperation valve (336) which
controls the mass flow and temperature of the hot HTF at
the entrance of the HTF HP super-heater (315); and an
attemperation valve (337) which controls the mass flow and
the temperature of the hot HTF at the entrance of the HTF-
to-IP-steam pre-heater (311);
The low pressure LP steam generation section (350)
comprises: a LP feed-water-pump (321) which raises the
feed-water flow pressure from the exiting pressure of the
condensate pump (346) to the low pressure (LP) operational
design point; a LP water pre-heater (357) which pre-heats
the feed-water flow; an LP steam-water loop including a
steam drum (351) which receives the water-steam mixture
through a collector line (358); a downcomer (352) wherein
the pressurized-hot-water flows down-ward due to natural
convection; a harp tube bundle including a harp collector
(356), boiler tubes (354) and a harp header (355), which
is connected to the downcomer (352) through feed line (353)
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CA 3055360 2019-09-13
and connects to the IP steam injection header (317) and
receives IP steam from IP steam drum (361) and is also
connected to the IP steam valve (318); an LP super-heater
(359) wherein the LP saturated steam is superheated and
directed to the LP steam turbine (341).
The intermediate pressure IP steam generation section
(360) comprises: an IP feed-water-pump (322) which raises
the feed-water flow pressure from low pressure (LP) to the
intermediate pressure (IP) operational design point; an IP
water pre-heater (367) which pre-heats the feed-water flow;
an IP steam-water loop including an IP steam drum (361)
which receives the water-steam mixture through an IP
collector line (368); a downcomer (362) wherein the
pressurized-hot water flows down-ward due to natural
convection; a harp tube bundle including a harp collector
(366), boiler tubes (364) which are connected to the HTF
IP evaporator (312) wherein additional IP saturated steam
is generated by solar means; an IP saturated steam line
(365) which connects to the HTF-to-IP-steam pre-heater
(311) wherein IP saturated steam is superheated by means
of solar energy; an IP super-heater (369) wherein the LP
saturated steam is superheated and directed to the IP steam
turbine (342).
The high pressure HP steam generation section (370)
comprises: a HP feed-water-pump stage (323) which raises
the feed-water flow pressure from intermediate pressure
38
CA 3055360 2019-09-13
(IP) to the high pressure (HP) operational design point; a
HP water pre-heater (378) which heats up the pressurized-
hot water flow entering a first stage of HP evaporation
section; a HP primary evaporator (374), a downcomer (376)
wherein the water flow is directed down-ward to a second
stage of HP evaporation section; a water distributor (377)
which directs the flow to the entrance of a HTF HP
evaporator (314); a HP secondary evaporator (375); a HP
collector line (373) which connects the evaporation section
to the superheating HP section; a vertical water-steam
separator (371) which connects to HTF HP super-heater
(315); a recirculation water line (379) which returns the
pressurized-hot water to the first stage of HP evaporation
section; and a HP super-heater (372) wherein the HP
saturated steam is superheated and directed to the HP steam
turbine (343).
Alternatively, the (HP) steam generation section (370)
can be configured by design and operated as one once-
through or supercritical steam generator. Accordingly, a
water steam separating equipment such as a vertical water-
steam separator (371) and downcomer (376) are typically
operating during start-up and partial load operation. The
heated feedwater from a (HP) water pre-heater (378) is thus
conveyed via a feed-water line to the bottom of the (HP)
primary evaporator (374). Due to the higher operating
pressure in the supercritical range, i.e., in excess of 221
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CA 3055360 2019-09-13
bar (absolute) there is never any distinct water-steam
interface.
The steam turbine section (340) comprises: an electric
generator (345); HP turbine (343); IP turbine (342) and the
LP turbine 341; a steam condenser (347); water-to-air heat
sink (348) wherein the rejected heat from steam cycle is
transferred to the ambient air; and a condensate pump
(346), which circulates the condensate from the steam
condenser (347) to the LP feed-water-pump (321).
The combustion turbine CT section (380) comprises: an
electric generator (385); an air compressor (382); a gas
turbine (383); and a combustion chamber (381).
In more detail, still referring to one advantageous way
of implementing the invention depicted in Fig. 3, the
hybrid plant (300), can be operated even when the solar
heat is not available by burning the primary fuel in a
combustion chamber (381) of a combustion turbine CT section
(380). By means of a CT shaft (384), the mechanical work
resulting of the hot gas expansion in the gas turbine (383)
is transferred to the air compressor (382) and to a rotor
of a generator (385) which produces electric energy.
The exhaust gases generated in combustion section (380)
enter the HRSG (320) via a hot path gas (328) and transfer
the recovered heat from combustion products expanded in the
gas turbine (383) to the water-steam flow circuit by means
of a sequence of heat exchangers comprising: a HP steam
CA 3055360 2019-09-13
generation section (370), which raises HP steam from water
pressurized by HP feed water pump (323); an IP steam
generation section (360), which raises IP steam from water
pressurized by IP feed water pump (322); and a LP steam
generation section (350), wherein LP steam is raised from
water pressurized by LP feed water pump (321). After
completing a once through pass the flue gases leave the
HRSG (320) through a chimney stack (324).
The steam expanded in the steam turbine section (340)
is directed to the condenser (347) and the condensate thus
produced is returned to the LP feed-water-pump (321) by
means of a condensate pump (346). The mechanical work
produced simultaneously by the expansion of the superheated
steam in each of the HP, IP and LP steam turbines is
transferred simultaneously to the steam turbine ST shaft
(344), which conveys mechanical energy to the ST electric
generator (345), to be converted into electric energy. The
combined cycle nominal gross output is the result of
simultaneous operation of (345) and (385) in a combined
cycle mode.
In one advantageous method of operating a hybrid HTF-
to-steam combined cycle plant (300), when the solar heat
is available, a portion of the HTF contained in a cold
storage tank (331) is pumped by a cold HTF pump (333)
through a solar receiver (313) and the resultant hot HTF
is directed to a hot storage tank (332). A hot HTF pump
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CA 3055360 2019-09-13
(334) pressurizes and distributes a portion of the hot HTF
among the HP steam generation section (370) and IP steam
generation section (360). A combustion turbine (CT) section
(380) can operate in a low capacity factor under reduced
fuel consumption mode at the same time some additional IP
saturated steam can be generated by means of solar energy
transferred from HTF to the water-saturated steam loop in
the HTF IP evaporator (312) and further superheated in HTF-
to-IP-steam pre-heater (311) within an IP steam generation
section (360).
Another portion of IP saturated steam can be generated
by solar means in the HTF IP evaporator (312) and collected
in IP steam drum (361). This IP saturated steam can be
directed through IP saturated steam circuit (316) and
further injected coaxially to each boiler tube in the water
distributor harp header (355) by IP steam injection header
(317).
In the IP steam generation section, the HTF flows from
hot HTF pump (334) through HTF-to-IP-steam pre-heater (311)
and further via HTF IP evaporator (312).
In the HTF IP evaporator (312), hot water conveyed from
IP steam drum (361) via downcomer (362) is evaporated and
the low quality saturated steam raised by solar means is
conveyed to the entrance of each one of the boiler tubes
(364) by convection in the natural circulation evaporation
section within (360). The IP saturated steam raised by both
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CA 3055360 2019-09-13
solar and hot exhaust gas recovery means are conveyed via
IP collector line (368) to IP steam drum (361), wherein the
saturated steam is separated from water. In HTF-to-IP-steam
pre-heater (311), the solar energy in the HTF flow received
from HTF pump (334) and attemperated by valve (337) is
transferred to the IP saturated steam exiting IP steam drum
(361) and a resulting IP superheated steam is conveyed to
an IP super-heater (369) for completing the superheating
process and further being conveyed to IP steam turbine
(342) wherein the steam expansion produces mechanical work
which is converted into electric energy by generator (345).
Additional HP saturated steam can also be generated by
solar means in the HTF HP evaporator (314) and superheated
in HTF HP super-heater (315) within a HP steam generation
section (370).
In the HP steam generation section, the HTF flows from
HTF pump (334) through HTF HP super-heater (315) and
further via HTF HP evaporator (314). The HTF exiting the
HTF HP evaporator (314) is mixed with the HTF exiting the
HTF-to-IP-steam pre-heater (311) and resultant HTF flow
passes through HTF IP evaporator (312) and further to the
cold HTF storage tank (331).
In the HTF HP evaporator (314), hot water conveyed from
downcomer (376) via water distributor (377) is evaporated
and the low quality saturated steam raised by solar means
is conveyed through boiler tubes (374) and mixes with
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saturated steam raised by hot exhaust gas recovery means.
The mixed water and HP saturated steam is conveyed to
vertical water-steam separator (371) via HP collector line
(373), wherein the saturated steam is separated from water.
The separated water in vertical water-steam separator (371)
returns to HP primary evaporator (374) via recirculation
water line (379), whenever HP steam generation section
(370) operates in partial load mode.
In HTF HP super-heater (315), the solar energy in the
HTF flow received from hot HTF pump (334) and mixed with
cold HTF provided by an attemperation valve (336) is
transferred to the HP saturated steam exiting vertical
water-steam separator (371) and a resulting HP superheated
steam is conveyed to a HP steam super-heater (372) for
completing the superheating process and further being
conveyed to HP turbine (343) wherein it is expanded and
mechanical work is converted into electric energy by an
electric generator (345).
The foregoing written description has been depicted to
enable those of ordinary skill to understand and appreciate
the existence of modifications and that many variations of
such an invention are possible in light of the present
disclosure. It will be evident that features may be added
or subtracted as desired and various modifications and
changes may be made thereto without departing from the
broader spirit or essential characteristics thereof. The
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scope of the invention is not to be restricted except in
light of the appended claims and their equivalents.
CA 3055360 2019-09-13
