TURBINE GENERATOR CYCLE FOR PROVISION OF HEAT TO AN EXTERNAL HEAT LOAD

CYCLE DE GENERATEUR DE TURBINE POUR SATISFAIRE UNE DEMANDE DE CHALEUR EXTERNE

English Abstract

TURBINE GENERATOR CYCLE FOR
PROVISION OF HEAT TO AN EXTERNAL HEAT LOAD
ABSTRACT OF THE INVENTION
A steam turbine power plant having associated
therewith a closed loop flow arrangement for extracting
heat from the power plant and supplying the extracted heat
to an external heat load. Included within the flow arrangement
is a predetermined number of heater elements, each of which
extracts steam having a predetermined heating capacity
associated therewith from a predetermined number of separate
locations within the power plant. The heat so extracted is
transferred to a heat transfer medium flowing at a pre-
determined flow rate within the closed loop arrangement. The
extracted heat is exchanged to the heat load within a heat
exchanger element connected within the flow arrangement.
The amount of heat extracted from the power plant is functionally
related to, and automatically limited by, the flow rate of
the heat transfer medium within the closed loop arrangement.
The flow rate of the heat transfer medium is itself func-
tionally related to the flow rate of the motive fluid for
the power plant.

Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:
1. A steam turbine power plant comprising, in
series, a steam generator element, a high pressure turbine
element, a low pressure turbine element, a condenser element,
a high pressure feedwater heater extracting steam from a
predetermined location within said high pressure turbine
element, a low pressure feedwater heater extracting steam
from a predetermined location within said low pressure
turbine element, said steam extracted from said high pressure
turbine having associated therewith a heating capacity
different from the heating capacity of said steam extracted
from said low pressure turbine element,
a closed loop flow arrangement disposed only in
heat transfer relationship with said power plant to extract
heat therefrom to supply a heat load, said flow arrangement
confining and guiding a heat transfer medium therewithin,
a first and a second heater element connected
within said flow arrangement, said first heater element
extracting heat from said power plant by extracting steam
from said predetermined location within said low pressure
turbine element and disposed in parallel with said low
pressure feedwater heater, said second heater element
extracting heat from said power plant by extracting steam
from said predetermined location within said high pressure
turbine element and disposed in parallel with said high
pressure feedwater heater, said heater elements transferring
said extracted heat to said heat transfer medium,
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a heat exchange element connected within said
flow arrangement for exchanging said extracted heat in
said heat transfer medium to said heat load, and,
means for controlling the rate of flow of said
heat transfer medium within said closed loop flow arrange-
ment, the magnitude of said heat extracted from said power
plant being directly controlled by said flow rate of said
heat transfer medium.
2. The power plant of claim 1, further comprising:
a third heater element connected within said flow
arrangement, said third heater element extracting heat from
a third location within said power plant and transferring
said extracted heat to said heat transfer medium,
said third location being disposed away from said
first and said second locations and having a heating capacity
associated therewith different from said heating capacities
associated with said first and second locations,
the magnitude of said heat extracted from said
third location within said power plant being directly con-
trolled by said flow rate of said heat transfer medium within
said closed loop flow arrangement.
3. The power plant of claim 2 wherein said third
location is disposed intermediate between said steam generator
element and said high pressure turbine element.
4. The power plant of claim 3, further comprising:
flow interruption means for interrupting steam flow
disposed between said third heater element and said ex-
traction point intermediate said steam generator element
and said high pressure turbine element.
23

5. The power plant of claim 3, further comprising:
an associated apparatus connected in series within
said power plant, said associated apparatus being driven
by a drive turbine element operatively connected within said
power plant,
a fourth heater element connected within said flow
arrangement at a point upstream of said first heater element,
said fourth heater element extracting heat from said power
plant and transferring said extracted heat to said heat trans-
fer medium,
said fourth heater element extracting heat from
said power plant by extracing steam from said drive turbine
element,
the heating capacity associated with said steam
extracted from said drive turbine element being different
from the heating capacity associated with said steam extracted
by said first, second, and third heater elements,
the amount of said steam extracted from said drive
turbine element being directly controlled by said flow rate
of said heat transfer medium within said closed loop flow
arrangement.
6. The power plant of claim 5, further comprising:
a fifth heater element connected within said flow
arrangement at a point intermediate said first and said
second heater elements, said fifth heater element extracting
heat from said power plant and transferring said extracted
heat to said heat transfer medium,
said fifth heater element extracting heat from
said power plant by extracting steam from a second extrac-
tion point within said low pressure turbine element,
the heating capacity of said steam extracted from
said second extraction point within said low pressure turbine
element being greater than the heating capacity of said
steam extracted from said first extraction point within
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said low pressure turbine element,
the amount of said steam extracted from said second
extraction point within said low pressure turbine element
being directly controlled by said flow rate of said heat
transfer medium within said closed loop flow arrangement.
7. The power plant of claim 6, further comprising:
a sixth heater element connected within said flow
arrangement at a point intermediate said second and said
third heater elements, said sixth heater element extracting
heat from said power plant and transferring said extracted
heat to said heat transfer medium,
said sixth heater element extracting heat from
said power plant by extracting steam from a second extraction
point within said high pressure turbine element,
the heating capacity of said steam extracted from
said second extraction point within said high pressure tur-
bine element being greater than the heating capacity of said
steam extracted from said first extraction point within said
high pressure turbine element,
the amount of said steam extracted from said second
extraction point within said high pressure turbine element
being directly controlled by said flow rate of said heat
transfer medium within said closed loop flow arrangement.
8. The power plant of claim 2, wherein
said steam produced by said steam generator
element is condensed by said condenser element and is
returned in liquid form to said steam generator element,
the flow of said liquid from said condenser element to
said steam generator element having a predetermined flow rate
associated therewith, and,
said means for controlling the rate of flow of

said heat transfer medium being functionally related to and
variable in a range of values between zero and .8 of said
predetermined flow rate of said liquid.
26

Description

BACKGROUND OF THE INVENTION
Field of the Invention
.~ .
- This inventi.on relates to steam turblne power
' plants, and, ln particular, to a steam turblne power plant
:~ havlng associated th.erewith'an assoclated' closed loop flow
arrangement for extractlng heat from the power plant and
supplying the heat so extracted' to an external heat loadO
.; Descript'ion of~_the Prlor Art:
I Recen~ly, emphasis has been placed on the realization
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of an economically attracti.ve '"dual-purpose"' power generation '. :''
fac~lity. adapted' to. ~ulflll a two-pronged' goal of simultaneous : .'' ~'
el'ectric power:generation and brine des'alinizationO In
such dual purpose 'faciliti.es', it has bee'n anticipated that -.:
the motive ~luid for the 'e.l'ec'tr:ic power gener'ation be '.
supplied:by a nuclear power'ed steam generator, while the .` ::'
' ~ .''
des'alinizati.on of brine 'is ef'fec'tuated' by the'application ~ '.:
of the "~lash ev'aporati:on" proces'sO
Brie'fly, flash'evaporation is a multi-stage
10 disti:llation process in which'sea water is progres'sively ~ -
heated to. a predet'ermined' temperature under given pressure '
conditions and then introduced' into: a chamber maintained
at a lower'pressure '~ust bel'ow the boiling point of ~ .
the hea:ted'brine.' As the 'hea'ted'brine 'enter's the lower : :
pres'sure chamber', the' reduced' pres'sure 'therein causes the
brine solution to boil, or ~flash"', into steam. The steam '
so produced is condensed' and the`'fres'h water produced thereby
ls conducted' away. It has bee'n anticipated' that the heat j '
, nec'es'sary to.raise the :temper'ature 'lev'el' of the brine be -
'' 20 ex'tracted from th.e nuclear-fuel' steam turbine power'plant
; In the' prior art,. it .ls common practice to raise
` the 'temperature of the'brine 'soluti:on by conducting steam
from one 'pred'et'ermined' ex'tracti:on locati:on within the power " : : .
plant direc'tly to. the brine 'hea't :ex'changer. The 'heat of the :
ex'tracted steam is the'r'e 'transferred' to: the'brine. The ' '
condensate. is returned' to:the'steam cycleO
~ Although'direc't :s.team ex'traction te:c'hniques have '.. ~;
'~ been succes'sful on small scale '(50 megawatt.. or les's) power :.
sta.ti:ons, th.ey' have 'litt.l:e 'applicability: for large capacity
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water desalinization power plants:. Also, ex'traction of
-volumes of stea'm larger' than a predet'ermined' amount from
only one locati.on within the power' plant may deleteriously
affect :the power generati:on cycle and require 'extensive
modificati.ons from current des'ign and oper'ating experienceO
In sum, direc't steam ex'traction as the 'hea't source for
flash evaporati.on desalinizati:on is of limited usefulnessO
To provide 'heat nec'es'sary for larger scale water-
making capabiliti.es, it has bee'n proposed' to: utilize '
a "bob-tailed" turbine apparatus of a rel'ativeIy large
size, on th.e 'order' of 1200 MoWo In such'a scheme, the :
exhaust of the'steam cycle 'is direc'tly introduced' as the
' hea't source for the' brine heater'. The 'hea't of condensation
of the' exhausted s.team raises' the 'temperature 'of th.e brine . ''
soLution, whi'le'the condensate:ret`urns to: th.e`'steam generator
el'ement .of the power' plantO:
The main disadvantage 'of such'an arrangement arises
f'rom the 'substl.tu.ti.on of the`brine hea'ter for the standard '.
.' condenser' el'ement : Such 'a substitu:tion raises' the back
pressure '-- th.e pres'sure 'immed'iately downstr.eam of the 'last
`, array of rota.ting blades' -- so that :ther'e'is little or no -
power' generation from thi's blade arrayO It :is apparent
that such 'a condition would adver'sely affec't the output and ' ~ :
;l. ' : .:::
; reliability of th.e 'el'ec'tr:ical generating plantO.
In order' to: obviate:'thes'e difficulti:es' due to the
increased'back pres'sure,' it :has been sugges'ted' that the '~
rota.ting blades' in th.e'last array be 'shortened', or "bob- ~-'. '
tailed", to; a hei'ght':les's than the blade :hei'ght' for a normal ~'
last row blade 'of commensurate:'power capability.O This . '~
ta:iloring of blade height's: to: mee't':sys.tem requirements. and
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the resulting highe'r:power'.density:requires' specially des'igned "~
blades for ea'ch individual applicati:on This, of course,
precludes' the use :of proven and rel'iable 'standardized
components. The probability: of failure 'increa'ses commensur- ' :
ateIy, and the:'efficiency and capability: of the :electrical .
plant :is permanently impairedO
: In additi.on, such'plants may not be dGwned for
- repair without sumultaneously halting desalinization
procedures. Conver'sely, as long as the producti:on of fresh
', 10 water is required, the 's.team plant must be operatedO Still
further, by prcviding speclally tailored' blades, there may
be generate.d' sev'er'e 'contr:ol problems, especially in the
overspeed contr.ol, due :to: the 'loss of rotati:onal inertiaO -' ' .
.
It .is apparent that .there 'is required' a steam
power generation system having associated' the'rewith an ~.
efflcient heat .cyole ~or large 'capability. water desalinization
able to. del'iver: the'rnaximum heat :transfer'yet still utilizing
standardized proven cornponen'ts.. It .is also patent that a
system and he'a't cycle uti.lizing he'at :ex'tracted from a .. ~
.~ 20 multiplicity. of sources' withi'n the 'power' plant .to supply .'
the he'at load is a def'inite:'improvement :over' prior art '. ..
. systems O In additi.on, a he'a't cycle adaptable to divert .
steam to.provlde hi'ghe'r or lower' water' capability depending ~.
upon peak electr.icity: demand, and to provide water'desalini- . ..
'i zation during periods of turbine inactivity, is also advanta-
l .
:~ geous over' the pres'ent :art
~' SUMMARY O~ THE INVENTION '
. .
The 'steam turbine power' plant embodying the .:
tea'chi'ngs of this inventi:on provides he`a't to. an external
heat load and overcomes' the''disadvantages' mentioned' in the
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prior art .in a novel:, useful, and unobvious manner.
The 'ste:am turbine power plant :comprises;, in series,
' a steam generator element,: a high'pressure,~ël'ement,. a low
:j pressure 'turblne 'el'ement,: and a condenser' elementO A
~, closed loop flow arrangement,:which 'confines' and guides a
heat transfer med'ium therein, is cooperativeIy assoclated'
with the' power'plant :to. extract heat :therefrom and supply
the heat so ex'tracted' to:the 'heat -loadO The'flow arrangement
includesl at .least tw.o heater' elements: connec'ted to a heat '. .
exchange 'el'ement :and to: a flow contr:ol deviceO The heater
extracts: hea:t,.in the :form of steam, from at .least two
' differ'ent ex'tracti.on locations, ea'ch having a different heating . :
.~ ~; ..... .
I capacity.associated' therew'ith,' within the power plantO ':' . '
.1 Provision may be made for a pred'et'ermined number of different '. ~ '
.' ex'traction locations or other' he`a't sources' from the'power '~
! . .
:~ gener'atlon cyclec~ The heat :thus ex'tracted' is transported ... :
by the' heat transfer med'ium to. the hea't exchange element,. . :;:
;' where lt .is ex'changed with'the heat loadO The amount of .
.1 heat extracted' ~rom the' power plant is functi:onally reIated ~ :
.~. 20 to. the flow rate.'of th.e' heat :transfer' med'iumO The flow .' ~'~
rate 'of the heat .transfer' med'ium is contr:olled'by the 'flow
~ control device. '. . .- .
'i~ In order' to: provide capability: for hea't transfer ".
.' during off-peak hours of the power plant,. one heat source ':
location provides' a bypass from the'steam gener'ator to a
hea:ter: el'ementO In the :event :of increased' elec'tric demand,
the bypass may be 'closedO
' It .is an ob~ect :of this inventi:on to provide a
~ steam turbine'power plant having an associated he'at transfer .. '
` 30 cycle `able to. ex'tract .th.e 'grea.te:s't amount :of heat while ':
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using standardized:power: plant :el'ements: and not requiring
specialized: component des'ignO
. It :is a furthe'r ob~ec't :of this inventi:on to, efficiently
transfer heat :to: an associated heat -load from a plurality of
hea't sources'within the''power plant,: thus not :overtaxing any '
one 'single ~ex'tracti:on zoneO It :is yet' a furthe'r object ,to
provide a closed' loop heat :flow arrangement associated with'a
steam turbine power plant in which'the amount :of heat :ex'tracted' . ..
from the power~plant .is direc'tly controlled by the' flow rate, of
10 the` heat .trans~er' med'ium flowing within 'the'flow arrangementO. ;~
j It :is a sti.ll further ob~ec't :of the''invention to. provide a heat ,
', flow arrangem'ent associated' with'a steam turbine power plant `
adapted so that .th,e requirement:s: of the''elec'trical load, heat : ''. .
' load or both~' may be met',.dep'endlng upon the' relative demand
, placed on ea'oh,' in an ea'sily regulable manner It is another ,:~ '
'' obJec't of the 'lnventi:on to.provide 'a flow arrangement associated
', with'a steam power' plant ,that is operable 'ev'en during non .. ':.
; productive periods of the power' plant~: Other' ob~ec'ts of
, the invention will become 'clear in the 'following detailed
, 20 descripti:on of the :pref'erred' embodiment.: --
,, BRIEF DESCRIPTION OF THE DRAWING ~ '
The inventl.on will be more 'fully under'stood from the ' . ::'
' following det'a.iled' des'criptl:on, taken in connec'tion with. , '
the accompanying drawing, in whi'ch:'
~' The Figure 'is a sche'mati:c repres'enta:ti.on of a steam
turbine power'plant having a he'at:tr:ansfer' arrangement ,
associated therewith'which'embodies' the 'teachings of the
inventionO ;,
S DESCRIPTION 0~ THE PREFERRED EMBODIMENTS - ''
- - -- ~:
' 30Ref:er'ring to: thb Figure,' ref'erence 'number 10 ~ :
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refers to. a steam turbine power plant having associated
therewith a sep'arate:'closed'-loop hea't transfer cycle 12
adapted to. ex'tract heat :from the 'power plant .10 and
apply the' heat so ex'tracte.d' to: a sep'arate heat load 13 .
The power' plant .10 is a standard steam power generation
facility comprising, in ser'ies' connec'tion, a steam flow .-
' passing from a steam gener'ator el'ement 16, a high pressure . :
turbine 'elemen't :18, low pres'sure 'turbine 'el'ements. 20, and ''~
a condenser' 22. Each 'of the''turbine 'el'ements: are mechani- :. '- ''
10 cally linked on a common shaft :24 and connec'ted' to. an elec- .
tr.ical generator el'ement :260 The''turbines' convert high '- :''
temperature and hi'gh'pres'sure 'energy of the moti.ve steam ' ;... '
to.rota.ti;onal ener'gy of the 'shaf t 24, which'is in turn conver'ted, ~ ''
by the generator 26, to: el'ec'trical ener'gy for a related .. ':
el'ec'trical load 280 : ~ ~
' In plants.such'as th:i's, the''steam gener'ator ` .:
el'ement .16 normally conver'ts: fee'd' water to.steam by '~ .: .
applylng thereto. hea't .ta.ken from a nuclear fuel' reactor
element 290 Howev'er', it .ls to: be understood that although :' :: ''
20 the plant .10 to.be des'cribed' her'ein is a nuclear power :-~
plant,. the 'teachi'ngs of this invention apply equally well
, .
. for both'nuclear and fossil fuel' applicationsO : '
:' High 'pres:sure,' high'temperature motive 'steam is ;.
., ~;, ~ " .
' conducted from the''ste:am generator el'ement :16, through a '. :
' series: of stop valves' indicated' at :numeral 30 and an array ' .
. ~ ., .
; of flow contr.ol valves: indicated' at :32, and into. the inlet ~: '
` of the' high'pres'sure :turbine 18, thi's steam flow being ` .
illustrated' by ref'er'ence 'arrows 34 Although the high ''
pres'sure 'turbine :el:em'ent :18 is illustr:ated' as being a double '
30 flow apparatus, it .is of course,' under'sto:od, that any
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suitable high pressure turbine'element may be utilizedO
Similarly, although ther'e 'is shbwn a bank of three, double-
flow low pres'sure turbine :elements: 20, it is also to be ''~
understo:od that any suitable number of low pres'sure elements.
of any suitable type, dep'ending upon the 'electrical power
system paramet:er:s, may be used'. The point worthy of note.
is that whate.v'er th:e 'number and type 'of turbine 'elements. ~.
chosen, the elements so chosen are standard units: adapted
to: conver't steam ener'gy to:rotati:onal mec'hanical energy. .
Ther:e 'is require'd litt:l:e alterati:on to: any of the 'turbine
el'ements chosen in order' to:practi:ce 'the 'teachings of this .~.
inventi:on and supply heat :to: the separate, closed'-loop heat '.
'' cycle 12. .
The'r'e may be provided', upsteam of the'stop
valves' 30, suitable 'hi'gh pressure 'taps, as at :36, to
supply moti.ve fluid for auxiliary steam system services,
such'as steam for the''gland seals disposed about the shaft
: 24, and steam to.the' air e~'ec'tors locate~d thr'oughout .the ' .:
system but .omitt:ed' here 'for clarlty~. After expanding
through'th.e` hl'gh'pressure turbine el'ement .18, the steam
is exhausted' ther:efrom, as shown by the' flow arrow 38 ~ : -.
and is conducted into.a combined moisture separator~
rehea'ter element :(MS-R) 40 where 'the steam ex'hausted .~.': '
'i` from the'hi'gh pressure turbine 'is raised' in temperature
before 'ex'iting th.e' MS-R 40, as shown at :42 Steam for the ' ;
I reheating functi.on of the''MS-R 40 is usually taken from
;' a tap located'upstr:eam of the 'stop valve '30, but such a ~:
' connection has bee'n omitt.ed' from the Figure for clarityO
:~ From th.e :ex'it :42 of the MS-R 40 the 'steam flow
. 30 passes through parallel inlet'.conduits. 44, each having
disposed' ther'eln an array of stop valves' 46 and interceptor
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valves 48 3 into. the':inlet's: o~ the 'low pres'sure 'turbine
el'ements. 20, the :flow indicated' by reference arrows 50. :.
The ste:am expands through 'the 'low pres'sure 'turbine elements '
;;? 20 and exhausts: ther:efrom, as shown at arrows 52, into the ' .:
.i condenser 220 Her'e 'the :steam is returned' to. the 'liquid
sta.te. ln th.e Iform of condensate~' .
, ~ . : . .
.~- From th:e:'outlet':of the 'condenser 22, the '
': condensate: is conducted', as shown by arrow 54, to a cc~densate
' pump 56 The 'condensate pump 56 pumps the 'condensate from ' :.
:
, 10 the :condenser: 22 through'a series' of ~eedwater' he'aters 58, '
60, 62 and 64c The 'feedwater hea'ters have 'as their function, :.
the ta~k of raislng the :temperature 'of the 'condensate passing ' '~
l ther'ethrough'to.a hi'gher' temperature 'ln anti.cipation of the
rel'ntroducti:on of the'condensate:'to: the''steam generator 160 ' ' ":.
'. Hea't for th.l's task iæ supplied'by ex'tracting steam ~rom pre~
sel'ec:ted' ex'traction zones' withi'n the''turbines' 18 and 200 .
As seen in the 'figure,' the''heater' 58 ls supplled'wlth'extrac .
tion steam ta.ken from a first pred'et'ermined' extractlon zone
66 within the':low pres'sure 'turbines' 200 The''steam extracted .~:~
;~ 20 ~rom zone '66 is conducted' through conduits: 68 lnto the reheater 58 .~'
as lllustrate.d'by flow arrows 700 Slmllarly, steam ls ex- ;'
tracted from a second pred'et'ermined' ex'traction zone 72
wlthin th:e 'low pres'sure :turbines' 20, through'conduits. '
74 and into.the reheater' 60, the''flow being shown by reference
. arrows 760 ~ :
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In like manner, steam is extracted from a .
third predetermined extraction zone 78 within the low
pressure turbine 20 and conducted through conduits 80 into : .
' the third reheater 62, this flow being illustrated by :.
reference arrows 82. As is apparent, each of the extraction
zones66, 72 and 78 extracts steam from within the turbine
20 at a higher te-mperature and pressure condition, and
thus the steam so extracted has associated therewith an ~-
~ increasingly higher heat capacity. In order to fully
lO utilize the heat content of the extracted steam, the :
drains of the reheaters 62, 60 and 58 are cascaded into
each other, as illustrated by flow arrows 84 and 86. The ;-
drain from the reheater 58 is conducted, as shown by arrow ~ .
88, into the condenser 22. Some plants provide, intermediate .
between the condensate pump 56 and the first feedwater ~:
heater 58, a condenser which returns gland sealing steam .
. to the liquid state. The drain from the gland condenser,
.l although omitted for clarity, enters into the main
`~ condenser at a point intermediate between the drain of the .
l 20 feedwater heater 58 and the condenser 22. -
:! :
As seen from the figure, the heater 64 derives ;:
, its heat from steam extracted from a predetermined
.l extraction zone 90 within the high pressure turbine 18,
through conduits 92, the flow being illustrated by flow
arrows 94.
.~ A boiler feed pump 96 is located downstream of
l the heater 64 and`pumps the nloOw-heated condensate through :
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a final feedwater heater 98~ From the final feedwater
heater 98 ~ the condensate, now known as boiler feedwater, ~:
.- :
is conducted to the s-team generator 16 to complete the
steam power plant loop 10, the flow being illustrated by .
reference arrow 100. The final feedwater heater 98
utilizes steam extracted from a second predetermined ~ :
i, . -
extraction zone 102 located within the high pressure .:.... :
. turbine 18~ the steam being conducted through conduits .
` 104 ~ as shown by flow arrows 106 ~ As seen from the figure, ~
10 the second predetermined extraction zone 102 occurs at a ~ : :
location within the high pressure turbine 18 that has ~-
associated with it a greater heat capacity than does the ~. .
steam from extraction zone 90. In order to efficiently ~ ~ :
; extract all available energy from the higher heat capacity
steam, the drain of the final feedwater heater 98 is
cascaded, as shown by arrow 108~ into the heater 64~ The ~.
" . ~.
draln from the heater 64 is itself pumped by a drain pump `~
.j (not shown) lnto the condensate flow to a point (not shown) -
, lmmediately upstream o~ the boiler feed pump 96~ For .. ~
; 20 completeness, the drain from the moisture separator .. ;
.~ por-tion of the MS-R 40 also is collected and pumped by ~ .
the drain pump (not shown) to the point (not shown)
~ immediately upstream of the boiler feed pump 96~ Also :
;~y omitted from the figure for clarity is the connection , :
. between the drain of the reheater portion of the MS-R 40
. and the final feedwater heater 98
:~ In order to provide motive power for the boiler
. ~eed pump 96 ~ there is provided a boiler feed pump drive
;l turbine 110, which is linked mechanically by a shaft 112
3 to the boiler feed pump 96~ The motive fluid for the
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drive turbine 110 is often prcvided by a tap immediately
downstream o~ the MS-R 40, the flow being illustrated
by arrow 114. It should be understood that similar
drive turbines or other mechanical linkages are disposed
to provide motive energy for other apparatus associated
with the power plant 10, of which the feed pump 96 is
, illustrative. For example, power must be provided to the ,~ :
condensate pump 56 and air ejectors. Although such
linkages are omitted for clarity, it is to be understood
that there exist drive turbines or drive motors, such
as that shown at 110, to provide power to these associated
apparatus. The exhaust fromthe drive turbine 110 is
; conducted, in a normal power plant, through conduit 116 ~¦
to the condenser 22. However, in accordance with this
inventlon, a control valve 118, normally closed, is
provided between the conduit 116 and condenser 22. In a
manner which is more fully explalned herein, the exhaust
rom the drive turbine 110~ or other power sources for the
steam æystems associated apparatus, is conducted by conduit
120 into, and acts as a one of the heat sources for, the
separate heat cycle 12 taught by this invention.
It is also known in the art that the control of ' -;
the flow of condensate in that portion of the power plant
10 between the condensate pump 56 and the boiler ~eed
pump 96 is managed by a suitable control arrangement
~ (not shown). It is to be understood, however, that there
',3l -
is a predetermined flow rate associated with the condensate
flow within the plant 10.
Cooperatively associated with the power plant
10 is the heat transfer cycle 12. As stated earlier, the
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steam power plant 10 is a standard power generation
facility. All elements contained therein are sized and
;~ designed such that high efficiency and maximum electrical
j generating capability is maintained. The heat transfer
cycle 12 is a closed loop arrangement cooperatively
; associated with the steam plant 10 to extract heat there~
from and supply the heat so extracted to the external heat ~
load 13. Although this application will discuss the heat ~-
-` load in terms of brine heati~g for a water desalinization
plant to provide fresh water, it is to be understood that
;t any heat load, such as industrial or residential heating,
, may be supplied.
`~ The heat cycle 12 typically comprises heater
elements 122, 124, 126, 128, 130 and 132 disposed so as to
;: .: '
' extract heat from the power plant 10 and transfer that heat
'i .. ,. :.. .,.:. to a heat transfer medium~ such as, but not limited to,
' water under a predetermined pressure, flowing within the
closed loop flow arrangement 12, The extracted heat
carried by the heat transfer medium is exchanged in a heat
exchanger element 134, in this instance a brine heater,
and supplied to the heat load 13. Completing the closed -~
loop arrangement 12 is a flow control valve 136 and a -~
, variable speed pump 138, similar to the condensate pump
56, to control the flow rate of the heat transfer medium,
the flow direction being indicated by arrow 140. If
' necessary, a surge tank 142 may be added to the arrangement.
The heat transferred by the heaters to the heat '~
transfer medium is obtained by extraction of steam from ; -
.~
: predetermined locati~ns within the power plant 10. The `
~`~ 30 steam extraction locations for each particular heater will ' .
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be discussed in turn.
The heacer 122 obtains steam exhausted from
the drive turbine 110 powering the associated steam
apparatus, such as the boiler feed pump 96, through
conduits 116 and 120. The pressure of the steam so
extracted, typically, approximates that of the lowe~t
pressure feedwater heater 58. In the case of no water
demand, of course, the valve 118 is opened, to permit~
exhaust directly to the condenser 22. ;-
As seen from the figure, heaters 124 and 126
extract heat from the plant 10 through the extraction of
steam from predetermined locations within the low pressure
turbines 20. For example, heater 124 is supplied by a
i conduit 144 tapping into the conduit 68 and extracting ..
steam from steam extraction zone 66, this flow being
illustrated by arrow 146. Heater 126, ln similar manner,
is connected through a conduit 148 which taps into the
conduit 74 to extract steam from the extraction zone 72
within the low pressure turbine 20, this flow illustrated ~
by arrow 150. ~ -
Heaters 128 and 130 are, as shown, supplied with
extraction steam from extraction zones 90 and 102 respec-
tively, within the high pressure turbine 18. In the case
of the heater 128, a conduit 152 taps into the conduit 92
to extract steam from zone 90, the exhaust of the high
pressure turbine 18, that flow being illustrated by arrow
154. For theheater 130, the conduit 104 from zone 102 is
tapped by conduit 155, the flow being illustrated by arrow
156.
The steam source for the heater 132 is a tap 158
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immediately past the outlet of the steam generator 16, a
bypass conduit 160 having a normally closed control valve ;~
162 disposed therein regulating the flow, as illustrated
by flow arrow 164. As will be discussed herein, the
provision of the bypass conduit 160 enables the heat cycle
12 associated with the power plant 10 to be operable even
during periods of zero electrical power generation, during
periods of low electrical loads or during periods of peak
water demand.
, 10 Normally, however, the control valve 162 is
closed, but extraction of steam from the other sources, as
outlined, provides the sufficient heat necessary to -
produce desalinization. It is apparent from examination
of the figure that the cycle 12 extracts steam from
several distinct locations within the plant 10, each of
which has associated therewith a separate heating capacity.
By heating capacity lt is meant the heat content, or ~-
enthalpy, associated wlth the steam at the particular
temperature and pressure at which that steam is taken
from the plant 10. For example~ it is clear that steam
extracted to the heater 130 from the extraction zone 102
within the high pressure burbine 18 has a greater heating
capacity than steam extracted to the heater 124 from the t!~ ~ 'I '.
extraction zone 66 within the low pressure turbine 20.
By providing a closed loop 12 able to take heat from a
predetermined plurality of locations within the power -
plant 10, sufficient heat may be provided for a large-scale
:, .
` desalinization project without overly taxing any single ;
`~, heat source location. Provision of the closed loop 12
, . . . .
enables maximum heat transfer to occur from the steam cycle -~
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10 to the heat transfer cycle 12 while still permitting -
utilization of standard components within the steam
plant.
Of course, in order to enhance the efficiency
of the cycle 12, the drain from each higher pressure
heater is cascaded into the next lower pressure heater, as
illustrated by arrows 168, 170, 172, 174 and 176. The
drains of the lowest pressure heater 122 in the heat -~
cycle 12 is returned, as shown by the ~low arrow 180, to
the condenser 22.
The flow rate of the heat transfer medium within i -
f the closed loop heat transfer cycle 12 is controlled, as
stated, by the pump 138 in association with the valve 136.
The flow rate is related to the rate of main condensate
flow between the pumps 56 and 96 which is part of the
overall motive ~luid flow rate of the power plant 18. The
heat transfer medium flow rate is between 0 to .8 of the
maln condensate flow rate, the exact value of heat
transfer medium flow rate being determined by a suitable
control arrangement 170 associated with the overall power
plant control (not shown) and being functionally related
to the demand required by the desalinizer.
, In operation, then, for a given heat demand, the
, heat transfer medium passes within the closed-loop cycle
12 at a predetermined flow rate between 0 and .8 of the
main condensate flow rate. The heat transfer medium is
heated by passage through the heater 122 supplied ~rom
the exhaust of the drive turbine 110, through the heaters
124 and 126 supplied with heat by extraction from the low
pressure turbine 20, and through the heaters 128 and 130
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supplied by steam extracted from the high pressure
turbine 18. If necessary, the medium is further heated
by the heater 132 supplied with steam through the bypass
conduit 160 from the steam generator 16. The heat so
.
extracted is transferred from the heat transfer medium to
the brine within the heat exchanger 134. The steam
extracted from the plant 10 is returned ta the condenser
22, after cascading through the lower pressure heaters. i~-
As may be appreciated by one skilled in the art,
the volume of the steam extracted from the power plant 10, ;
and thus the magnitude of heat extracted therefrom, is -
: . . .:
directly related to the ~low rate o~ the heat transfer -
medium. For example, attention is directed to the heater ~;
126, supplied with steam extracted from the extraction
zones 72 within the low pressure turbines 20. The steam
so extracted has associated therewith a predetermined `
pressure, for example approximately 25 p~s.i,a. and an
associated temperature, here, 240F, When such steam is
conducted into the shell of the reheater 126, it condenses
on the tubes passing therethrough and having the heat
transfer medium therein. The heat transfer medium takes
` the heat of vaporization from the extracted steam at the ~`
given pressure, and temperature, here 240F, and the heat-
transfer medium is heated thereby. As the heat of vapor-
ization is taken by the heat transfer medium, the extracted
steam condenses, and more steam is drawn into the heater
from the extraction zone. However, it is apparent that
the temperature of the heat transfer medium may only rise ;
to the saturation temperature associated with the pressure
of the extracted steam, in this instance, to 240F. Once
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the heat transfer medium is heated by the extraction steam
to this temperature, that medium takes no additional heat ;~
from the extracted steam. With this occurrence, no
further extracted steam condenses in the heater 126, and
no further steam is extracted from the zone 72 to the
heater 126. Thus, the volume of steam extracted is auto-
matically limited by a thermodynamic equilibrium established
within the heater 126, This process is similar to that
occurring in all the heaters within the closed loop
heat transfer cycle 12, no matter what the location of
' the heat source supplying the heater.
To further increase the volume of steam
extracted, it is simply necessary to increase the flow
rate of the heat transfer medium. Since more of the medium
will pass through the heater 126, more medium will be
available to take the heat o~ condensation from the
extracted steam. There~ore, more of the extracted steam
condenses within the heater 126, and therefore more steam
is extracted from the turbine 20. Conversely, o~ course,
to decrease the amount o~ steam extracted from the plant
10, the simple expedient o~ lowering the ~low rate of the ~ -
heat transfer medium accomplishes this result. In the
~ extreme case, i.e., when the water demand is zero, no
; steam will be extracted if the heat transfer medium flow
.,. . ~:
is stopped. As stated, then, by varying the flow-rate
of the heat transfer medium between 0 and .8 of the
predetermined ~low rate of the main condensate flow, the
volume of steam extracted from the power plant is directly
controllable. Of course, any known expedient for
; 30 controlling the flow rate of the heat transfer medium is
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within the contemplation of this invention. The flow
rate of the heat transfer medium is controlled so as to
maintain steam extraction from the various heat source
locations within allowable design capabilities of a
power generation cycle utilizing standard turbine ~ ;
elements.
If the electrical load condition on the power
plant 10 were to be reduced by a given amount, the flow
rate of the motive fluid through the power generation
cycle, which includes the condensate flow, is commensurately
reduced. If the flow rate of the heat transfer medium
was not correspondingly adjusted, the heaters within the
.: . .
heat transfer cycle 12 would extract, from the heat source `
locations within the power plant lO, volumetric flows of -
steam greater than those optimumly permitted by standard `
system components. Therefore, it is appreciated that the
flow rate of the heat transfer medium is functionally ~;
. .
related to the flow rate of the main condensate flow, with
the heat transfer flow rate being at all times within the ~ -
limits 0 to .8 of the main condensate flow rate.
During periods of low electrical loads, then,
, . ...
the motive fluid flow requirements of the power generation
cycle 10 are lower, necessarily resulting in a lower heat ;
:;
transfer medium flow rate, If, however, at this same
time there is imposed upon the heat transfer cycle 12 an
increase in the heat load, this increase may be met by
simply opening the control valve 162 to initiate flow
from the steam generator 16 to the heater 132.
It is appreciated then that the closed loop
.,. ~ ,.
~ 30 heat transfer cycle 12 associated with the power plant
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10 admirably accomplishes all those functions unable to
be effected by prior art systems~ There is provided an
overall system for the supply of heat to a desalinization
plant, or other heat load, which utilizes proven,
standardized turbine-generator component designs. By
provision of the closed-loop cycle, heat is extracted
. from a predetermined plurality of locations within the
- power plant, thus no one location is overtaxed for
extraction steam, thus guaranteeing maximum heat transfer
capability while maintaining the capability for generation
of large amounts of electrical power with standard
components. There is also provided full capability for
power during peak electrical periods. By closing the
. valve 162 in the bypass conduit 160, and reducing the
heat transfer medium flow rate to zero, full rated
electrical power may be generated.
~ Provision is also made for the production simul-
i; taneously of both electricity and water, during periods
of moderate electrical and moderate water demand. Pertur-
bations in water demand may be accommodated, for example,
by varying the heat-transfer flow rate, by opening the
control valve 162, or by using the valve 162 to modulate
an already established bypass flow. The ratio of electrical
, output to heat output may thus be varied on command. A
switch-back capability between electricity and water demands
may also be easily accommodated.
The system embodying the teachings of this invention
also provides for water production during periods of no
electrical demand, or during periods of turbine unavailabil-
ity. By providing the closed loop cycle, the heat demand
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is no longer tied to the actual operation of the power ~-
generating ~acility. Conversely, needed turbine main-
tenance or inspection need not be dependent upon periods
of slack water demand. Implicit to this consideration
is the ability to provide water during off-peak electrical
periods while still maintaining peak electrical capability
on demand.
It being understood that although a specific - ,~
preferred embodiment of the invention has been shown and
described, modifications may be made without departing
from the spirit of the invention, as embodied in the
appended claims.
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