US3164135A - Monotube boiler feedwater and steam temperature control - Google Patents

Monotube boiler feedwater and steam temperature control Download PDF

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Publication number
US3164135A
US3164135A US85335A US8533561A US3164135A US 3164135 A US3164135 A US 3164135A US 85335 A US85335 A US 85335A US 8533561 A US8533561 A US 8533561A US 3164135 A US3164135 A US 3164135A
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United States
Prior art keywords
pressure
fluid
steam
vapor
temperature
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US85335A
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English (en)
Inventor
Beck Harold Von
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Combustion Engineering Inc
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Combustion Engineering Inc
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Publication date
Priority to NL273658D priority Critical patent/NL273658A/xx
Application filed by Combustion Engineering Inc filed Critical Combustion Engineering Inc
Priority to US85335A priority patent/US3164135A/en
Priority to CH2462A priority patent/CH390946A/de
Priority to GB2884/62A priority patent/GB929856A/en
Priority to BE613148A priority patent/BE613148A/fr
Priority to FR886099A priority patent/FR1312821A/fr
Priority to ES0274107A priority patent/ES274107A1/es
Application granted granted Critical
Publication of US3164135A publication Critical patent/US3164135A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B35/00—Control systems for steam boilers
    • F22B35/06—Control systems for steam boilers for steam boilers of forced-flow type
    • F22B35/10—Control systems for steam boilers for steam boilers of forced-flow type of once-through type
    • F22B35/102—Control systems for steam boilers for steam boilers of forced-flow type of once-through type operating with fixed point of final state of complete evaporation, e.g. in a steam-water separator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22G—SUPERHEATING OF STEAM
    • F22G5/00—Controlling superheat temperature

Definitions

  • the invention relates to a once-through vapor generator operating in the supercritical pressure range and to a method for controlling the operation thereof. More particularly the invention is concerned withan improved method and an improved arrangement of devices for controlling the feedwater flow to a once-through steam generator and for controlling the temperature of the superheated steam produced at a pressure above the critical pressure, 3,206.2 p.s.i.a. solute); p 7 p
  • a steam generator equipped with a steam and water drum a relatively large reservoir of water is generally (pounds per square inch abavailable. When operating a boiler ofthis type with hatural circulation ah increase in firing rate produces an 1n-- crease in circulation of the water through the heated tubes.
  • the feedwater flow as well as the temperature of the superheated steam is regulated in response to a steam temperature impulses.
  • anticipating control signals such as impulses of steam flow.
  • a steam flow indicator such as an orifice has been employed for anticipating fluctuations in Y heat input also in boilers operating in the supercritical pressure range.
  • control has proven to be unsatisfactory because it is 'too strongly influenced by other factors such as feedwater flow.
  • the steam generator economizer 24 receives feedwater of a relatively low temperature by way ofv a feed pump 26 and feed pipe 28. After heating the water-in the economizer 24 to a suitable temperature, the water fiows via pipe 3t) and inlet 13 into water Wall tubes 16 for further heating and generation of steam. After passing through outlet 2% and conduit 31, additional heating of this steam to a predetermined desired temperature takes place in superheater ZZfrom whence v the steam is delivered by way'of steam pipe 32 to a point of use such as steam turbine 34 driving an electric generator 36.
  • the nextcontrol step isto bringthe feedwater flow to maintain a suflicient feedwater supply and a constant pressure and temperature of the'steam regardless of load variations.
  • FIG. 1 is a diagram representing a feedwater control system for a once-through steam generator operating in the supercritical pressure range and employing the novel feedwater control system and method disclosed by the invention.
  • FIG. 2 is a conventional enthalpy diagram illustrating the relationship of the enthalpy values of water and steam and'absolute pressures thereof for various temperature parameters.
  • FIG. 3 is a diagram representing a control system similar to that shown in FIG. 1 with additional control impulses received for regulating the superheated steam ternperature.
  • combustion elements such as fuel and air are introduced into steam generating chamber it) limits (within the area V reduction to 400 p.s.i'.a.
  • a pressure reducing device- is provided, here'shown in the form of throttling valve 52, to reduce the pressure from a super.
  • r instance, would entail a lowering of the percentage of steam to 265/710 or 37.3 percent or a reduction of 436/436 minus 37.3/43.6 or 14.5 percent.
  • the reduction in firing rate should cause a drop in temperature, for instance from 720 F. to 700 F. or about 2.78 percent, a corresponding drop in steam quantity proportion in the mixture when reducing the pressure to 680 p.s.i.a. would occur from 43.6 to 37.3 or 14.5 percent. about 5.3 times as high as the percent variation obtained by temperature measurements (14.5 divided by 2.78).
  • the heat in the liquid will amount to 700 Btu. per pound, with a total of 800 B.t.u. per pound of mixture and a total heat of evaporation at 2220' p.s.i.a. of 415B.t.u. per pound.
  • a drop in heat absorption would cause a drop in temperature from 720 F. to 700 F. or about 2.78 percent, a corresponding drop in steam quantity when reducing.
  • the pressureto 2220 p.s.i.a. in this case, would occur from 100/415 .to 55/415 or 100/100 minusSS/lOO or .45 percent. stitute a percentage variation about 16.2 times as high as the percent variation obtained by temperature measurements (45 divided by 2.73).
  • a pressure sensing device 54 is employed in co-action with throttling valve 52 and control valves 56 to maintain a constant back pressure in the steam and .water mixture passing through conduits, 57, 58, 59, and 60.
  • the steam and water mixture leaving valve 52 passes into a separator 62 wherein the steam is separated from the water,'the formerflowing through conduit 59 to a region of lower pressure such as the inl'et'to condenser 4-0.
  • a flow measuring device 64 provided in conduit 59 senses variations in steam flow. These impulses are transmitted to fcedwater regulator 66 for controlling the positioning of feedwater valve 67 and constitute an anticipating-control signal.
  • variations of the water flow impulses or the steam flow impulses may be employed as they are separately and independently received'by feedwater regulator 66 for regulating the feedwater flow from flow measuring devices 68 or 64 respectively, these impulses being evaluated against predetermined proportional quantities of steam or water, when the temperature of the steam at point 50 is normal.
  • the pressure maintained at the pressure indicating device 54 is 680 p.s.i.a. as in the example earlier discussed herein, the percentage of steam measured by I accordingly constitutes the set point.
  • This constitutes a percentage variation steam flow indicating device 64- would be 43.6% and that of water 56.4%, with the boiler normally operating at 4400 p.s.i.a. and 720 F.
  • This percentage relationship A decrease of the percentage of steam or an increase of the percentage of water therefore would indicate a feedwater quantity in excess of that needed to match the prevailing heat input and would result in regulation of valve 67 such as to redu'cethe feedwater flow.
  • an increase in the percentage of steam or a decrease in the percentage of water below the set point would result in regulation of valve 67 such as to increase the feedwater flow.
  • the set point depends on the selected subcritical pressure that is maintained in line 57, which pressure determines the relative percentage of steam and water leaving separator 62 for a final steam temperature of 700 F., for example.
  • This set point pressure may be chosen to be the same, such as 680 p.s.i.a., for all loads. Or a different set point such as for example, if the unit is being operated for an extended period at reduced loads.
  • a steam quality measuring device 74 serves the purpose of determining the quality or wetness of the steam leaving throttling valve 52, such variations in steam quality being a direct indication of the heat release or firing rate.
  • a calorimeter of a design well known in the art could be employedfor this purpose.
  • Other suitable devices could be used such as a recording flame photometer determining the wetness of the steam by measuring variations of sodium content in wetness of the steam can be measured directly, the neces-' sity of first separating the steam phase from the water phase in separator 62 is dispensed with.
  • One preferred method of controlling the temperature of the superheated steam entering steam turbine 34 is by injecting a controlled quantity of feedwater into the flow path of superheated steam at one or more points such as at point 80 (FIG. 3). This is accomplished by.
  • a valve 82 controls the amount of water thus injected for reducing the steam temperature to a desired. value.
  • Valve 82 is actuated. by an injection Water controllerobtained from the supercritical pressure steam extracted 1 at point 50 as hereinabove described in connection with FIGS. 1 and 2. 'Under certain operating conditions it may be desirable to only employ characteristics of the,
  • the heat content of the supercritical pressure fluid at point-5t ⁇ furnishes a pre-adjusting control via the subcritic'al pressure mixture-of steam and water obtained in pipe 57, both for regulating the feedwater flow via feedwater regulator 66' as well as for maintaining a constant steam temperature via injection water controller 83.
  • the hereindisclosed system for controlling the operation of a steam boiler in the supercritical pressure range not only retains" all the advantageous'features of a control system fora steam boiler operating inthe subcritical pressure range" but establishes a much desired closer relationship between feedwater controliyand steam temperature .control by the use of a common anticipating control impulse via controller 66.
  • this is basically accomplished by extracting a portion of the supercritical pressure fluid the desired enthalpyof'which is known, reducing the pressure thereof to a predetermined subcritical pressure therebynproducing a mixture of water and steam, measuringand utilizing thermal characteristics of this mixture that are indica--' tive of variations of the heat content thereofxfrorn the desired or expected heat content, for the purpose of controlling the feedwater flow or steam'temperature or both.
  • a fluid heating circuit producing throughout the normal operating load range thereof a vapor in the supercritical pressure range having means for feeding relatively cool liquid fluid to said fluid heating circuit under a pressure in excess of the critical pressure and at an inlet temperature below the critical temperature, said circuit having means for heating. said liquid fluid to'an outlet temperature in excess of said critical temperature-for the production of vapor from said fluid, the combination ofmeans for controlling the flow of said fluid fed to said heating circuit, means for extracting throughout said normal'operating load range a -portion' of said.
  • a fluid heating circuit producing throughout the normal operating load range thereof a vapor in the supercritical'pressure range having means for feeding relatively cool fiuid'in the liquid phase to said fluid heating cirresponse to variations of the fluid quantity in saidone cuit under a pressure in excess of the critical pressure and at an inlet temperature below the critical temperature, said circuit having means for heating said liquid fluid to an outlet temperature in excess of said critical tem perature for the productionof vapor from said fluid,
  • the combinationof meansfor controlling the flow of said liquid fluid fed to said heating circuit, means for extracting throughout said normaloperating load range a portion of said fluid from said circuit at a location that yields fluid at a temperature in excess of said critical temperature said portion being independent of theload demand, flow restricting means for throttling the flow of said extracted portion and for reducingthe pressure thereof to a predetermined pressure below the critical; pressure to cause said extracted'fluid to form a two-- phase mixture of liquid'and vapor, means for obtaining an indication of the fluid.
  • ajvaporigenerator having aonce-through fluid passage receiving liquid at one end and delivering throughout the normal load range thereofa superheated vapor atsupercritical pressure and under normal operating conditions at the other end, and elements of combustion for -hcating said fluid, the combination ofmeans for extracting throughout said normal operating load range a portion of said fluidfrom said fluid passage at a point thereof yielding fluid at supercriticalpressure and of supercritical temperature said portion being independent of the load demand, meansfo'r reducing the pressure of said extracted fluid to a predetermined subcritical pressure to form a two-phase mixture of liquid and vapor, means for separating the vapor from, the liquid, means for obtaining indications of the: flow rates of said liquid and vapor and means for.
  • the method of conrolling the unheated fluid fed to said circuit comprising the steps of heating said fluid to an exit temperature in excess of the critical temperature and at a pressure in excess of the critical pressure, extracting throughout said normal operating load range a portion of said fluid and said portion being independent of the load demand reducing the pressure thereof from supercritical pressure to a predetermined subcritical pressure to cause said fluid portion to form a two-phase mixture of liquid and vapor, separating the vapor from the liquid, effectively determining the fluid flow rate in at least one of said phases while maintaining said predetermined subcritzical pressure, and adjusting said unheated flow rate in'responsc to variations in the fluid flow rate in said one phase.
  • the method of controlling the fluid fed to said circuit comprising the steps of heating saiid fluid to an exit temperature in excess of the critical temperature and at a pressure in excess of the critical pressure, extracting throughout said normal operating load range a portion of said fluid said portion being independent of the load demand and reducing the pressure thereof from "apressure in excess of the critical pressure to a predetermined pressure below the critical pressure to I cause said fluid portion to form a two-phase mixture of liquid and vapor, measuring the actual ratio of said liquid and vapor and regulating the quantity of fluid fed to said circuit in response to deviations of said actually measured liquid and vapor ratio from a predetermined normal ratio while maintaining said predetermined pressure.
  • a fluid heating circuit producing throughout the normal operating load range thereof a vapor in the supercritical pressurerange
  • the method of controlling the fluid fed to said circuit comprising the steps of heating said fluid to an exit temperature in excess of the critical temperature and at a pressure in excess of the critical pressure, extracting throughout said normal operating loadrange a portion of said fluid said portion being independent of the load demand and-reducing the pressure thereof from a pressure in excess, of the critical pres- 7 sure to a predetermined pressure below the critical presvalue of less than 12% Bin per pound saidquantity being independent of the load demand, means for reducing the pressure of said extracted quantity to a predetermined pressure in the subcritical range to cause the formation of atwo-phase mixture of liquid and vapor; means for measuring the value of a property of said mixture that is indicative of the heat of evaporation of said mixtnre, and means effective in maintaining said superheated vapor at 'aconstant temperature in response to said measuring means.
  • the method ofcontrolling the fluid fed to said circuit comprising the steps of heating said fluid to an exit temperaure in excess of the critical temperature and at a pressure inexcess of the critical pressure, extracting throughout said normal operating load range a portion of said fluid said portion being independent of the load demand and reducing the pressure thereof from a pressure in excess of the critical pressure to a cause said fluid portion to change into a fluid quantity in thevapor state and a fluid quantity in the liquid state,
  • the method of controlling the fluid fed to said circuit comprising the steps of heating said fluid to an exit temperature in excess of the critical temperature and at a pressure in excess of the critical pressure, extracting throughout said normal operating load range a portion of said fluid said portion being independent of the load demand and reducing the pressure thereof from a pressure in excess of the critical pressure to a predetermined pressure below the critical pressure to cause said fluid portion to change into a fluid quantity in the vapor state and a complementary fluid quantity in the liquid state, determining the quantity of vapor relative to the quantity of liquid and increasing or decreasing respectively the flow rate of fluid fed to said circuit as said quantity of vapor increases and said quantity of liquid decreases, or as said quantity of vapor decreases and said quantity of liquid increases.
  • the method of controlling throughout the normal operating load range thereof the operation of a vapor generator having a once-through fluid passage receiving liquid at one end and delivering superheated vapor at supercritical pressure at the other end and heated by elements of combustion which includes the steps of extracting throughout said normal operating load range a quantity of fluid from said fluid passage at a point thereof yielding fluid at supercritical pressure and of supercritical temperature said quantity being independent of the load demand, reducing the pressure of said extracted fluid to a predetermined subcritical pressure to form a two-phase out said normal operating load range a quantity of said working fluid having an enthalpy value of less than 1200 Btu.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
US85335A 1961-01-27 1961-01-27 Monotube boiler feedwater and steam temperature control Expired - Lifetime US3164135A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
NL273658D NL273658A (enrdf_load_stackoverflow) 1961-01-27
US85335A US3164135A (en) 1961-01-27 1961-01-27 Monotube boiler feedwater and steam temperature control
CH2462A CH390946A (de) 1961-01-27 1962-01-05 Verfahren zum Regeln eines Zwangdurchlaufdampferzeugers und Dampferzeuger zum Durchführen des Verfahrens
GB2884/62A GB929856A (en) 1961-01-27 1962-01-25 Regulation of forced-flow once-through steam generators
BE613148A BE613148A (fr) 1961-01-27 1962-01-26 Procédé pour le réglage d'un générateur de vapeur à circulation forcée à parcours unique et générateur de vapeur pour la mise en oeuvre du procédé
FR886099A FR1312821A (fr) 1961-01-27 1962-01-26 Générateur de vapeur à circulation forcée à parcours unique et son procédé de réglage
ES0274107A ES274107A1 (es) 1961-01-27 1962-01-27 Procedimiento para la regulaciën de un generador de vapor de circulaciën forzada y generador de vapor para la realizaciën del procedimiento

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US85335A US3164135A (en) 1961-01-27 1961-01-27 Monotube boiler feedwater and steam temperature control

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US3164135A true US3164135A (en) 1965-01-05

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US (1) US3164135A (enrdf_load_stackoverflow)
BE (1) BE613148A (enrdf_load_stackoverflow)
CH (1) CH390946A (enrdf_load_stackoverflow)
ES (1) ES274107A1 (enrdf_load_stackoverflow)
FR (1) FR1312821A (enrdf_load_stackoverflow)
GB (1) GB929856A (enrdf_load_stackoverflow)
NL (1) NL273658A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260246A (en) * 1964-03-13 1966-07-12 Siemens Ag Regulating arrangement for forced flow type boiler
US3612005A (en) * 1970-01-12 1971-10-12 Foster Wheeler Corp Once-through steam generator recirculating startup system
DE3336596A1 (de) * 1983-10-07 1985-04-25 Siemens AG, 1000 Berlin und 8000 München Verfahren zum regeln eines in kraft-/waermekopplung betriebenen kraftwerkblockes
EP0308596A1 (de) * 1987-09-22 1989-03-29 GebràœDer Sulzer Aktiengesellschaft Verfahren zur Regelung der Speisewassermenge einer Dampferzeugeranlage
DE10001995A1 (de) * 2000-01-19 2001-07-26 Alstom Power Schweiz Ag Baden Verfahren zur Einstellung bzw. Regelung der Dampftemperatur des Frischdampfes und/oder Zwischenüberhitzerdampfers in einem Verbundkraftwerk sowie Verbundkraftwerk zur Durchführung des Verfahrens
US20170234528A1 (en) * 2016-02-17 2017-08-17 Netzsch Trockenmahltechnik Gmbh Method And Device For Generating Superheated Steam From A Working Medium

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3243578C3 (de) * 1982-11-25 1998-10-22 Babcock Energie Umwelt Verfahren zum Betreiben eines Zwangsdurchlaufdampferzeugers

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2170346A (en) * 1935-12-18 1939-08-22 Bailey Meter Co Control system
GB816765A (en) * 1956-11-22 1959-07-15 Sulzer Ag Steam power plants
GB817121A (en) * 1956-07-27 1959-07-22 Sulzer Ag Forced throughflow steam generators
US2900792A (en) * 1955-06-04 1959-08-25 Sulzer Ag Steam power plant having a forced flow steam generator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2170346A (en) * 1935-12-18 1939-08-22 Bailey Meter Co Control system
US2900792A (en) * 1955-06-04 1959-08-25 Sulzer Ag Steam power plant having a forced flow steam generator
GB817121A (en) * 1956-07-27 1959-07-22 Sulzer Ag Forced throughflow steam generators
GB816765A (en) * 1956-11-22 1959-07-15 Sulzer Ag Steam power plants

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260246A (en) * 1964-03-13 1966-07-12 Siemens Ag Regulating arrangement for forced flow type boiler
US3612005A (en) * 1970-01-12 1971-10-12 Foster Wheeler Corp Once-through steam generator recirculating startup system
DE3336596A1 (de) * 1983-10-07 1985-04-25 Siemens AG, 1000 Berlin und 8000 München Verfahren zum regeln eines in kraft-/waermekopplung betriebenen kraftwerkblockes
EP0308596A1 (de) * 1987-09-22 1989-03-29 GebràœDer Sulzer Aktiengesellschaft Verfahren zur Regelung der Speisewassermenge einer Dampferzeugeranlage
CH673697A5 (enrdf_load_stackoverflow) * 1987-09-22 1990-03-30 Sulzer Ag
DE10001995A1 (de) * 2000-01-19 2001-07-26 Alstom Power Schweiz Ag Baden Verfahren zur Einstellung bzw. Regelung der Dampftemperatur des Frischdampfes und/oder Zwischenüberhitzerdampfers in einem Verbundkraftwerk sowie Verbundkraftwerk zur Durchführung des Verfahrens
US6497101B2 (en) 2000-01-19 2002-12-24 Alstom (Switzerland) Ltd. Method and apparatus for regulating the steam temperature of the live steam or reheater steam in a combined-cycle power plant
US6615575B2 (en) 2000-01-19 2003-09-09 Alstom (Switzerland) Ltd Method and apparatus for regulating the steam temperature of the live steam or reheater steam in a combined-cycle power plant
US20170234528A1 (en) * 2016-02-17 2017-08-17 Netzsch Trockenmahltechnik Gmbh Method And Device For Generating Superheated Steam From A Working Medium
US10451270B2 (en) * 2016-02-17 2019-10-22 Netzsch Trockenmahltechnik Gmbh Method and device for generating superheated steam from a working medium

Also Published As

Publication number Publication date
GB929856A (en) 1963-06-26
ES274107A1 (es) 1962-06-16
CH390946A (de) 1965-04-30
FR1312821A (fr) 1962-12-21
NL273658A (enrdf_load_stackoverflow)
BE613148A (fr) 1962-07-26

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