US3532079A - Method for starting steam power plants - Google Patents

Method for starting steam power plants Download PDF

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Publication number
US3532079A
US3532079A US757608A US3532079DA US3532079A US 3532079 A US3532079 A US 3532079A US 757608 A US757608 A US 757608A US 3532079D A US3532079D A US 3532079DA US 3532079 A US3532079 A US 3532079A
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Prior art keywords
steam
temperature
superheater
turbine
sections
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Expired - Lifetime
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US757608A
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English (en)
Inventor
L A Chambert
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Svenska Maskinverken AB
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Svenska Maskinverken AB
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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
    • F22B35/14—Control systems for steam boilers for steam boilers of forced-flow type during the starting-up periods, i.e. during the periods between the lighting of the furnaces and the attainment of the normal operating temperature of the steam boilers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K3/00—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein
    • F01K3/18—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein having heaters
    • F01K3/20—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein having heaters with heating by combustion gases of main boiler
    • F01K3/22—Controlling, e.g. starting, stopping

Definitions

  • the method decreases the required startup time by utilizing the heat energy stored in the thicker walled steam piping and headers as much as possible while at the same time minimizing thermal shocks to either superheaters or headers,
  • the method consists of suppressing normal steam flow through each superheater and respective header until the superheater has reached a temperature corresponding to its header.
  • the object of this invention is to obtain a rapid startup of the steam generator and the turbine while minimizing the thermal stresses of the heavy metal parts.
  • the invention also gives a possibility to minimize the startup time and still protect the unit in a proper way independent of the actual temperature levels in the unit when it is started.
  • the type of operation is question is so maintained that when the unit is taken out of operation for one shift, or periods which can be longer or shorter, it is bottled up in order to keep pressure and temperature as high as possible
  • the heavily insulated, thick metal parts, such as the superheater headers and the turbine chest, will generally be at a very high temperature for a long time.
  • FIG. 1 illustrates a typical steam generator.
  • FIG. 2 shows typical gas temperatures (dashed), material temperatures of the coils (fully drawn) and material temperatures of headers (dash-dotted), and how they vary with time in a conventional startup after a limited stop.
  • FIG. 3 shows a startup diagram according to the new system with time variation for pressure, flow and temperature.
  • FIG. 4 is a schematic drawing which il lustrates the significant features of the invention.
  • FIG. 5 illustrates how the factors of FIG. 2 vary when principles of the present invention are utilized.
  • the feed water is heated in the economiser l and supplied to the steam drum 3 through the feed water piping 2.
  • the water is fed to the water drum 6 where it is distributed to the furnace walls 7.
  • the steam-water mixture (or steam) is returned to the steam drum 3.
  • the water and steam is separated in the drum 3 and the steam is fed to the superheater sections. These consist of a low temperature section SH], 9 an intermediate section 8H2, l2 and the final superheater 8H3, 16.
  • Each section is composed of an inlet header 11 and 15, tube banks 12 and 16 and an outlet header 13 and 17.
  • the superheated steam is then led to the high pressure turbine with its throttle valve 19 and back to the boiler through the steam piping 18 and 21.
  • the steam is heated in the first reheater section RHl, 23 and second reheater section RI-I2, 24 to full temperature.
  • the outer low pressure parts consist of steam piping 26, turbine 28 and condensor 29.
  • the steam may also be bypassed over the low pressure turbine 28 directly to the condensor 29 through a bypass valve 30.
  • the invention can best be understood by first discussing a startup without use of the system.
  • startup is about to begin, the headers and piping are hot, but the superheater and reheater pendants are, if the unit has been out of operation long enough, at approximately saturation temperature.
  • the unit is fired at a rate which increases the saturation temperature 3C. per minute or another rate of this order which is not giving too high thermal stresses in the saturated system.
  • the gas temperature entering the superheater may rise to but not exceed a level around 540C.
  • the metal of the superheater and reheater pendants is heated by the gas flow. After an infinite time all the pendants would be at the 540C. temperature level as illustrated in FIG.
  • the basic concept of this invention involves firing the unit at a rate to achieve an allowed and safe saturation temperature increase of for instance 3C/min.
  • a steam flow is passed through these intermediate superheater sections and also through the reheater.
  • No steam is passed through the finishing superheater section. Since steam is being taken from the steam drum, the firing rate is increased to maintain the same saturation temperature rise.
  • Those low temperature sections which have reached the desired temperature level are protected from overheating by the steam flow.
  • the finishing superheater section is thereby heated at a higher rate than it normally would be until such a time as it reaches a satisfactory temperature level. Only at this time is steam passed through the finishing superheater section into the hot piping where the critical fatigue problem exists.
  • FIG. 3 is a startup diagram as anticipated for a big new steam generator-turbine unit and is believed to be self-explanatory when viewed in conjunction with the invention as a whole. It shows in comparison with FIG. 2 very short available times for startup and defines the risks for very rapid temperature changes in the boiler if this is started up conventionally.
  • FIG. 4 is a schematic drawing which illustrates the significant features of the invention.
  • the normal flow of steam is from the steam drum 2 to and through the low temperature superheater 3'. It then passes through the intermediate temperature superheater 4 and through the final superheater 5'.
  • the steam passes through the turbine through the final superheater outlet header 6, the steam line 7' and the turbine throttle valves 8'.
  • a reheated steam section 9' is also shown.
  • the unit With the unit bottled up and at a pressure between for instance 20 and atmospheres depending on pressure at and time since last operation, it is fired at a rate to increase the saturation temperature at a predetermined rate, for instance 3C./min.
  • the metal temperature of the intermediate superheater outlet header 11' is measured.
  • the metal temperature of for instance an outlet leg of the intermediate superheater section 4' is measured at a location in the gas stream.
  • the temperature of this metal should normally be within a few degrees of the temperature of the steam inside the tube.
  • the metal temperature is preferred to the steam temperature since the absence of any substantial steam flow at this time makes the measurement of the steam temperature of questionable value. Furthermore, evaporation of condensate in the loops could upset the temperature measurement on some occasions.
  • steam flow is started through certain portions of the unit. This is accomplished by opening the bypass valve 12 so that steam flows from the steam drum 2' through the superheater sections 3' and 4' to the cold reheat inlet header 13.
  • the steam flows through the reheat sections 9', the reheat outlet header l4 and may be passed to the condenser through valve or passed to atmo sphere as desired. At this time no steam flows through the finishing superheater 5 nor through the steam line 7' and the turbines.
  • the firing rate must be increased to maintain the same rate of temperature rise in the waterwall circuits. This, in turn, increases the gas temperature entering the superheater sections.
  • the intermediate superheater and reheater sections are protected from overheating by steam flow while at the same time the finishing superheater section 5' is heated more rapidly.
  • the temperature of the the metal of the superheater outlet header 6' is measured as well as the temperature of an outlet leg of the finishing superheater section 5'. Steam flow is not admitted through the finishing superheater section until such a time as these two temperatures are sufficiently close to avoid thermal shock in the superheater outlet header 6.
  • This steam flow is established by opening the bypass valve 16 which causes steam to flow through the entire superheater section, the main steam line and the reheat lines. Presumably a desuperheater would be required in this bypass.
  • the bypass valve 12 which was earlier opened is now closed either at once or after some short period of time which will suit the steam generator as determined by tests or other criteria.
  • Each of these bypass valves can be sized to provide the proper steam flow for the conditions which they are to satisfy. It should be noted that with a fixed opening of either one of these valves the steam flow through the valve increases as boiler pressure increases. Since the heat of vaporization decreases at high pressure, this increased evaporation is obtained with approximately the same firing rate so that the rate remains approximately constant over the range.
  • the valve 12 is controlled by a controller 31 responsive to the temperature of the intermediate superheater tubes and the respective outlet header as indicated by dashed lines in FIG. 4.
  • the valve 16 is controlled by a controller 32 responsive to temperatures of the final superheater header and tubes as indicated by the dashed lin es.
  • the method described gives the fastest possible heating up of the superheater material and will that way as soon as possible in a safe way permit steam to be taken out from the unit without thermal shock problems in the thicker parts of the headers.
  • This gives an increasing temperature not only in the saturated system but also in the superheater sections. The result is that the steam outlet temperature can be raised to a level where a safe and fast turbine loading can be obtained.
  • the superheater outlet header 6' should be insulated even though it is located in the dog house. This would permit the superheater outlet header metal temperature to remain approximately the same as that of the steam piping. By these means the thermal stresses may be avoided in all the high pressure sections at the same time. It should be noted that if no thermal stress problem exists in the intermediate superheater outlet header ll, that portion of the startup can be omitted with bypassing steam flow being based on some other criteria The significant portion of the invention being not only this basic concept which is applied to the intermediate superheater section but the use of this concept in the final section while bypassing steam around the final section and the turbine.
  • FIG. 5 represent gas and metal temperatures at various firing rates during startup. They illustrate the rate at which the superheater sections change temperature as the required heat is stored in the metal of the various sections.
  • the system may also a boiler throttle valve 20'a be included which could be used, if desired, to move the temperature drop due to throttling from the turbine throttle valves to this location upstream of the superheaters. If pressure downstream of the boiler throttle valve is to be less than about 400 p.s.i. at any time, it may be preferable to locate this valve 20b downstream of the first superheating section so as to avoid the formation of water-stream mixtures.
  • Criteria such as temperature measurements in the first sections after the furnace properly compared to header temperatures which will allow an initial startup valve to be opened as fast as possible and preferably to a preset value.
  • Criteria such as the temperature of the turbine chest combined with the information from the boiler, can allow the rolling and the subsequent loading to be made at a time and in a way which will give the fastest possible subsequent turbine loading.
  • the information can be handled as follows:
  • the actual temperatures and pressures of the boiler outlet parts including the superheaters and the turbine can give the criteria for the turbine to be rolled up and synchronized.
  • the first steam flow through the turbine is relatively small and the rolling can many times be made while the steam from the boiler still has a relatively low temperature, sometimes lower than the metal temperature in the turbine.
  • the described startup system will allow a safe startup of a unit consisting of boiler and turbine combining the startup system for the boiler as described with a method to govern the turbine operation following information taken from both the boiler and the turbine.
  • the described startup system may be extended and combined with a so-called boiler-throttle valve 'a and 2071 respectively.
  • the startup and loading of the turbine can thus always be made by steam, the conditions of which give a temperature distribution in the turbine rather close to that at high load. If closed when the unit is taken out of operation it also prevents condensation in the superheaters and the piping system.
  • the system described is also well suited for other types of boilers such as suband supercritical ones-through boilers.
  • the only difference between these systems and that described is that these systems must have a minimum throughflow of about 30 percent in the furnace or initial evaporating and fluidheating system, obtained by means of circulating and/or feed pumps.
  • the firing rate in the initial steps must therefore possibly be based on some other additional criteria than the temperature increase in this system only.
  • the basic concept of the invention as described together with the startup operation will be the same.
  • Method of starting up a steam generator with a series of superheater sections, each with its respective header, after a limited operational interruption, when thick walled elements, such as headers, are elevated in temperature compared to surfaces of said superheater sections comprising, precluding normal steam flow through said superheater sections and headers, monitoring the temperature of each of said superheaters and its respective header, allowing normal steam flow through each of said superheaters, serially, as the temperature of each superheater rises to a predetermined value in relation to the temperature of its respective header.
  • said generator also includes a plurality of reheaters, when diverted from its normal path steam flows through one of said reheaters.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
US757608A 1967-09-11 1968-09-05 Method for starting steam power plants Expired - Lifetime US3532079A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE6712496A SE376961B (enrdf_load_stackoverflow) 1967-09-11 1967-09-11

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US (1) US3532079A (enrdf_load_stackoverflow)
ES (1) ES358016A1 (enrdf_load_stackoverflow)
FR (1) FR1586474A (enrdf_load_stackoverflow)
NL (1) NL6812987A (enrdf_load_stackoverflow)
SE (1) SE376961B (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4237825A (en) * 1978-11-06 1980-12-09 Combustion Engineering, Inc. Furnace heat absorption control
US4841918A (en) * 1986-11-06 1989-06-27 Babcock-Hitachi Kabushiki Kaisha Boiler control system
US20060233637A1 (en) * 2005-03-16 2006-10-19 Kabushiki Kaisha Toshiba Turbine starting controller and turbine starting control method
EP1744020A1 (de) * 2005-07-14 2007-01-17 Siemens Aktiengesellschaft Verfahren zum Starten einer Dampfturbinenanlage
US20130008394A1 (en) * 2011-07-08 2013-01-10 Foster Wheeler North America Corp. Radiant Superheater
US20140000277A1 (en) * 2010-12-30 2014-01-02 Ezio Pasqualon Method to start up and manage a combined cycle thermal plant for energy production and relative plant

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59231604A (ja) * 1983-06-14 1984-12-26 Hitachi Ltd 火力発電プラントの運転制御方法

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4237825A (en) * 1978-11-06 1980-12-09 Combustion Engineering, Inc. Furnace heat absorption control
US4841918A (en) * 1986-11-06 1989-06-27 Babcock-Hitachi Kabushiki Kaisha Boiler control system
US20060233637A1 (en) * 2005-03-16 2006-10-19 Kabushiki Kaisha Toshiba Turbine starting controller and turbine starting control method
US7980053B2 (en) * 2005-03-16 2011-07-19 Kabushiki Kaisha Toshiba Turbine starting controller and turbine starting control method
RU2370653C1 (ru) * 2005-07-14 2009-10-20 Сименс Акциенгезелльшафт Способ запуска паротурбинной установки
US20090126365A1 (en) * 2005-07-14 2009-05-21 Edwin Gobrecht Method for starting a steam turbine installation
WO2007006617A3 (de) * 2005-07-14 2008-06-26 Siemens Ag Verfahren zum starten einer dampfturbinenanlage
US7805941B2 (en) 2005-07-14 2010-10-05 Siemens Aktiengesellschaft Method for starting a steam turbine installation
EP1744020A1 (de) * 2005-07-14 2007-01-17 Siemens Aktiengesellschaft Verfahren zum Starten einer Dampfturbinenanlage
CN101305163B (zh) * 2005-07-14 2012-11-14 西门子公司 起动蒸汽透平设备的方法
US20140000277A1 (en) * 2010-12-30 2014-01-02 Ezio Pasqualon Method to start up and manage a combined cycle thermal plant for energy production and relative plant
US10240487B2 (en) * 2010-12-30 2019-03-26 Stamicarbon B.V. Method for startup and management of a combined cycle heating system for the production of power
US20130008394A1 (en) * 2011-07-08 2013-01-10 Foster Wheeler North America Corp. Radiant Superheater

Also Published As

Publication number Publication date
ES358016A1 (es) 1970-04-01
FR1586474A (enrdf_load_stackoverflow) 1970-02-20
SE376961B (enrdf_load_stackoverflow) 1975-06-16
NL6812987A (enrdf_load_stackoverflow) 1969-03-13

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