EP0191353A1 - Control procedure for a boiler plant operating on solid fuel, and corresponding control apparatus - Google Patents

Control procedure for a boiler plant operating on solid fuel, and corresponding control apparatus Download PDF

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Publication number
EP0191353A1
EP0191353A1 EP86101087A EP86101087A EP0191353A1 EP 0191353 A1 EP0191353 A1 EP 0191353A1 EP 86101087 A EP86101087 A EP 86101087A EP 86101087 A EP86101087 A EP 86101087A EP 0191353 A1 EP0191353 A1 EP 0191353A1
Authority
EP
European Patent Office
Prior art keywords
secondary air
flue gas
control member
setting
air control
Prior art date
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.)
Withdrawn
Application number
EP86101087A
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German (de)
English (en)
French (fr)
Inventor
Seppo Miettinen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SAASTAMOINEN Oy
Original Assignee
SAASTAMOINEN Oy
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by SAASTAMOINEN Oy filed Critical SAASTAMOINEN Oy
Publication of EP0191353A1 publication Critical patent/EP0191353A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/02—Regulating fuel supply conjointly with air supply
    • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/08—Microprocessor; Microcomputer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/08—Measuring temperature
    • F23N2225/10—Measuring temperature stack temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2237/00—Controlling
    • F23N2237/16—Controlling secondary air

Definitions

  • the present' invention concerns a procedure for controlling the combustion process in a boiler plant operating on solid fuel, in said procedure the solid fuel being converted into combustible gases and the amount of secondary air supplied to the combustible gases for their combustion being regulated by controlling a secondary air control member.
  • control of the combustion process in heating boilers has been by continuously measuring the oxygen and carbon dioxide content of the flue gas and performing the control on the basis of this direct measurement, by controlling the secondary air.
  • control has also been common in which the primary and secondary air quantities are set to have constant values for each given rate of power output.
  • the settings of the primary and secondary air dampers have been found by estimating, in various ways, the goodness of combustion.
  • the excess air quantity is at its optimum. If too much secondary air is supplied, the fuel in the combustion volume does not need all the oxygen available in order to burn completely. This excess oxygen, and the corresponding proportion of the air, is however heated to the same temperature as the combustion gases, thus binding thermal energy and therefore cooling the flue gas.
  • An inadequate secondary air quantity is not enough to burn all the gases fit to be burned, whereby carbon monoxide, in particular, gains access to the boiler's convection parts without being oxidized. This chemically bound energy escpaes from the combustion process, and the flue gas will not be heated up to the theoretical maximum. The maximum value of the flue gas temperature yields the best result of combustion.
  • German application print No. 2 756 284 is known a system which is intended for burning gaseous fuel.
  • the fuel/com- bustion air ratio is determined in a separate control burner.
  • a temperature sensor has to be mounted in, or close to, the flame.
  • German application print No. 3 224 500 is known a measuring instrument which, admittedly, measures the flue gas temperature but which fails to apply its findings in any kind of control.
  • the apparatus gives notice when the flame is too dark or when the flue gas is too hot, i.e., when the boiler is being run with excessive power output in relation to the momentary condition of the boiler.
  • the object of the invention is to achieve an improvement of presently known control procedures for a boiler plant operating on solid fuel.
  • the more detailed aim of the invention is to provide a control procedure which enables optimum combustion and better efficiency to be achieved.
  • the other aims of the procedure of the invention, and the advantages gainable with its aid, will become apparent in the disclosure of the invention.
  • the aims of the invention are achieved with a control procedure for a boiler operating on solid fuel which is mainly characterized in that the combustion air quantity is optimized in that with a temperature sensor in the flue gas passage is measured the flue gas temperature at different settings of the secondary air control member, and a mathematical function is constructed which approximates the set of secondary air control member setting vs. temperature plots, the maximum flue gas temperature being solved therefrom, corresponding to this functon's maximum, and the setting of the secondary air control member is changed to be consistent with said setting of the secondary air control member, obtained as a result of optimizing.
  • control apparatus for controlling the combustion process in a boiler plant operating on solid fuel.
  • the control apparatus of the invention is mainly characterized in that the control apparatus comprises a calculator unit incorporating an optimation programme, and a secondary air control member controllable with the aid of set-point values derived from said calculator unit, and that the control apparatus comprises one single temperature sensor, installed in the flue gas passage, supplying to the calculator unit the results of temperature measurement, corresponding to different settings of the secondary air control member, required in optimizing the combustion air quantity.
  • the heating center operating according to the forebox principle comprises a fuel supply assembly, a forebox, and a boiler with chimney.
  • the burning means in the forebox converts the solid fuel into gaseous state.
  • Said forebox burning means does not participate in the combustion process proper.
  • the fuel runs from an intermediate silo onto an inclined grate, the embers glowing in this grate's lower part and on the planar grate drying the fuel and liberating the volatile gases therefrom.
  • the carbon in the fuel becomes oxidized with the oxygen of the air supplied through the primary hatch, producing carbon monoxide.
  • This gas mixture is not yet burned in the forebox; it is instead conducted by the fire tube into the boiler.
  • the hot gas mixture coming from the forebox is added air from the secondary air connector of the firebox, whereby the gases are partly ignited in the fire tube and move, burning, into the boiler.
  • the basic idea of the invention is to accomplish control of combustion using only one thermocouple in the flue passage, measuring the flue gas temperature. Optimation of the combustion process takes place at the output power of the boiler at a given moment. For each output value a maximum can be found in the flue gas temperature when the secondary air quantity is varied. Said optimizing of combustion, and therewith maximizing of the combustion temperature, is accomplished with an apparatus in which the flue gas temperature is measured with a number of given secondary hatch settings, e.g. with three settings.
  • the invention also comprises a throttling damper placed in the flue passage, and correction for the interdependence of the secondary air hatch settings.
  • To the set of plots is further added the plot (sa,ta) n+1 , which contains the throttling damper setting during optimation and the optimum secondary air hatch setting.
  • PNS fit is constructed, and the corrected Equation (1) is formed with the equation therefrom obtained.
  • the changed position of the secondary damper has no significant effect on the subatmospheric pressure in the firebox, and therefore there is no need to change the setting of the primary damper.
  • the procedure of the invention also comprises a step in which the combustion air quantity is checked at given intervals and, if required, correction is made so that through optimizing as taught by the invention is achieved a setting of the secondary air hatch consistent with maximum temperature of the flue gas.
  • the interval between optimations may be one hour. This is advantageous because the influence of sporadic disturbances is then minimized.
  • the invention also concerns an apparatus consistent with the procedure, in this apparatus being essential that only one temperature sensor is employed, this thermocouple being located in the flue gas passage, and the apparatus comprising a calculating unit, suitably a microcomputer, which carries out the optimation consistent with the procedure just described, utilizing the measurement information obtained from said sensor, whereby as a result of the measurements and of the calculations made by the calculating unit, that is of the optimizing, is achieved a secondary air damper setting consistent with the excess air optimum.
  • This excess air optimum quantity corresponds to the maximum of the temperature.
  • the heating centre operating on solid fuel has been indicated in general with the reference numeral 10.
  • the solid fuel storage bin is indicated with reference numeral 11.
  • the storage bin 11 has an openable cover structure 12, and the lower part 13 of the storage bin 11 is tapering.
  • Reference numeral 14 indicates a plunger feeder, arranged to move solid fuel from the storage bin 11 by a transport tube 15 to the intermediate silo 16.
  • a limit switch 17 has been fitted to control the supply of solid fuel to the intermediate silo 16 so that the intermediate silo 16 is substantially filled to capacity all the time.
  • the heating centre 10 comprises a forebox 18, this being a burning means which converts the solid fuel, for instance chipped wood, sawdust, lump peat, to gaseous state without participating in the ultimate combustion process.
  • the fuel runs from the intermediate silo 16 e.g. down on an inclined grate, the embers glowing in its lower part and on the planar grate drying the fuel and liberating therefrom the volatile gases.
  • the carbon in the fuel is oxidixed with the oxygen in the air supplied through the primary air hatch 19, producing carbon monoxide.
  • This gas mixture is not burned in the forebox 18; it is conducted by the fire tube 21 into the boiler 23.
  • a feeder e.g. a plunger feeder
  • This system keeps the intermediate silo 16 filled to capacity at all times, independent of the fuel consumption.
  • An action means 20 has been provided to control the primary air hatch 19, i.e., to change the setting of the primary air hatch 19.
  • the reference numeral 26 indicates the chimney and numeral 27, the base on which the forebox 18, boiler 23 and chimney 26 have been erected.
  • thermocouple 29 measuring the flue gas temperature has been placed in the flue passage 24.
  • a flue gas exhauster 25 has been mounted in the flue passage 24.
  • the part after the exhauster 25 of the flue passage 24 carries the reference numeral 24a.
  • the flow of flue gases under natural draught is indicated by the arrow A and that with forced draught, by the arrow B.
  • the procedure of the invention now comprises a step in which with a thermoelement 29, suitably a thermocouple, in the flue gas passage is measured the flue gas temperature at a plurality of points. It is shown in Fig. 5 that with optimum excess air quantity and with a given setting of the secondary air hatch 22 optimum combustion is achieved, whereat the flue gas temperature has its maximum. If through the secondary air hatch 22 too little air is admitted into the fire tube 21, not enough oxygen is obtained for the combustion, while in the event that there is too much air the excess air binds thermal energy and the energy bound in this manner is wasted.
  • a thermoelement 29 suitably a thermocouple
  • the curve passing through the plots that have been found is approximated with a parabola, of which the constants are found by setting up simultaneous equations with the plots and by solving them e.g. with the aid of Cramer's method or by another mathematical method.
  • the setting of the secondary air hatch 22 corresponding to the maximum of the curve gives optimum combustion.
  • a mathematical function representing the relationship between the flue gas temperature and the setting of the secondary air hatch 22 is constructed in which the variables are temperature and setting of the secondary air hatch 22.
  • the secondary air hatch 22 is now set in this particular position with the aid of the control equipment. There may also be more than three points of measurement, but the measurement at three points which has been described is sufficient.
  • Optimizing is achieved with a calculating apparatus, suitably a microcomputer, in which the optimation process has been programmed.
  • the sensor 29 in the flue passage 24 measuring the flue gas temperature is suitably a thermocouple, because the temperature here is already reasonably low and a thermocouple is then better resistant.
  • the fact that only one sensor 29 is needed has also a favourable effect on the price of the whole control equipment.
  • Fig. 6 illustrates an optimizing measurement. Everything takes place on one time axis. Topmost is shown the course of the flue gas temperature. The lower graphic presentation, again, represents the settings of the secondary air hatch at the different steps.
  • the abbreviations (SST,AST, YST and STA,ATA,YTA) correspond to the points of measurement, already discussed, associated with the optimizing run.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Regulation And Control Of Combustion (AREA)
EP86101087A 1985-02-01 1986-01-28 Control procedure for a boiler plant operating on solid fuel, and corresponding control apparatus Withdrawn EP0191353A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI850427A FI850427L (fi) 1985-02-01 1985-02-01 Styrningsmetod foer pannanlaeggning som fungerar med fast braensle och motsvarande styranlaeggning.
FI850427 1985-02-01

Publications (1)

Publication Number Publication Date
EP0191353A1 true EP0191353A1 (en) 1986-08-20

Family

ID=8520305

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86101087A Withdrawn EP0191353A1 (en) 1985-02-01 1986-01-28 Control procedure for a boiler plant operating on solid fuel, and corresponding control apparatus

Country Status (2)

Country Link
EP (1) EP0191353A1 (fi)
FI (1) FI850427L (fi)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0339135A1 (de) * 1988-04-25 1989-11-02 Landis & Gyr Betriebs AG Verbundsteuereinrichtung für einen Brenner
EP0563976A1 (en) * 1992-04-03 1993-10-06 Honeywell Inc. Apparatus and method for monitoring the operating condition of a burner system
AT399386B (de) * 1990-02-01 1995-04-25 Holzinger Johann Anordnung zur regelung einer mechanisch beschickten feuerungsanlage für späne, hackgut, stroh usw.
DE102015110218A1 (de) * 2015-06-25 2016-12-29 Stefan Doliwa "Kessel oder Ofen für einen Brennstoff, insbesondere Kohle, vorzugsweise Steinkohle, und Verfahren zum Gluterhaltungsbetrieb des Kessels oder Ofens"
CN106642192A (zh) * 2017-02-17 2017-05-10 长沙市驱动源电气技术有限公司 震动式给料燃烧机及其控制方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960320A (en) * 1975-04-30 1976-06-01 Forney Engineering Company Combustion optimizer
EP0050840A1 (de) * 1980-10-23 1982-05-05 Karl Dungs GmbH & Co. Verfahren zur Einstellung von Verbundreglern für Brenner in Wärmeerzeugungsanlagen
DE3221660A1 (de) * 1981-06-11 1983-01-05 Paul G. Dipl.-Ing. Dr.techn. 8010 Graz Gilli Verfahren zum zwecke der optimalen verbrennung bei feuerungen
GB2117876A (en) * 1981-07-18 1983-10-19 Stone Platt Fluidfire Ltd Boilers
EP0124330A1 (en) * 1983-04-21 1984-11-07 Autoflame Engineering Limited Improvements in or relating to fuel burner control systems
DE3315199A1 (de) * 1983-04-27 1985-01-17 Schaveg AG, Vaduz Festbrennstoffvergasungsanlage

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960320A (en) * 1975-04-30 1976-06-01 Forney Engineering Company Combustion optimizer
EP0050840A1 (de) * 1980-10-23 1982-05-05 Karl Dungs GmbH & Co. Verfahren zur Einstellung von Verbundreglern für Brenner in Wärmeerzeugungsanlagen
DE3221660A1 (de) * 1981-06-11 1983-01-05 Paul G. Dipl.-Ing. Dr.techn. 8010 Graz Gilli Verfahren zum zwecke der optimalen verbrennung bei feuerungen
GB2117876A (en) * 1981-07-18 1983-10-19 Stone Platt Fluidfire Ltd Boilers
EP0124330A1 (en) * 1983-04-21 1984-11-07 Autoflame Engineering Limited Improvements in or relating to fuel burner control systems
DE3315199A1 (de) * 1983-04-27 1985-01-17 Schaveg AG, Vaduz Festbrennstoffvergasungsanlage

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0339135A1 (de) * 1988-04-25 1989-11-02 Landis & Gyr Betriebs AG Verbundsteuereinrichtung für einen Brenner
AT399386B (de) * 1990-02-01 1995-04-25 Holzinger Johann Anordnung zur regelung einer mechanisch beschickten feuerungsanlage für späne, hackgut, stroh usw.
EP0563976A1 (en) * 1992-04-03 1993-10-06 Honeywell Inc. Apparatus and method for monitoring the operating condition of a burner system
DE102015110218A1 (de) * 2015-06-25 2016-12-29 Stefan Doliwa "Kessel oder Ofen für einen Brennstoff, insbesondere Kohle, vorzugsweise Steinkohle, und Verfahren zum Gluterhaltungsbetrieb des Kessels oder Ofens"
DE102015110218B4 (de) 2015-06-25 2019-10-02 Stefan Doliwa "Kessel oder Ofen für Steinkohle und Verfahren zum Gluterhaltungsbetrieb des Kessels oder Ofens"
CN106642192A (zh) * 2017-02-17 2017-05-10 长沙市驱动源电气技术有限公司 震动式给料燃烧机及其控制方法
CN106642192B (zh) * 2017-02-17 2019-01-15 长沙市驱动源电气技术有限公司 震动式给料燃烧机及其控制方法

Also Published As

Publication number Publication date
FI850427L (fi) 1986-08-02
FI850427A0 (fi) 1985-02-01

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