DD252660A1

DD252660A1 - METHOD AND ARRANGEMENT FOR STARTING A STEAM BOILER

Info

Publication number: DD252660A1
Application number: DD29427386A
Authority: DD
Inventors: Horst-Dieter Kaldun; Werner Reich; Uwe Krueger; Bernd Kuehnel; Klaus Koehler; Walter Mautsch
Original assignee: Orgreb Inst Kraftwerke
Priority date: 1986-09-10
Filing date: 1986-09-10
Publication date: 1987-12-23

Abstract

Verfahren und Anordnung zum Anfahren eines kohlenstaubgefeuerten Dampfkessels mit ueberlagertem Zwangsumlauf, bei dem der Druckaufbau im Verdampfer unter Beachtung der notwendigen Unterkuehlungsspanne zwischen Verdampfer und Ekonomiser erfolgt und die HD-Reduzierstation mit einer Vordruckregelung betrieben wird. In der Phase, in der die Einspritzungen im Ueberhitzertrakt in Betrieb zu nehmen sind, wird dem Vordruckregler ein Sollwert vorgegeben, der die Unterkuehlungsspanne beruecksichtigt. Zur Realisierung des Verfahrens ist die Sollwertzufuehrung des Vordruckreglers umschaltbar ausgebildet. In der genannten Anfahrphase ist sie mit einem besonderen Anfahrregler verbunden, in dem dieser Sollwert gebildet wird. FigurMethod and arrangement for starting a pulverized coal-fired boiler with superimposed forced circulation, in which the pressure build-up in the evaporator takes place under consideration of the necessary Unterkuehlungsspanne between evaporator and economizer and the HD-reducing station is operated with a form control. In the phase in which the injections in the superheater tract are to be put into operation, the pre-pressure regulator is given a setpoint which takes into account the sub-cooling span. To implement the method, the setpoint supply of the admission pressure regulator is designed switchable. In the mentioned start-up phase, it is connected to a special start-up controller in which this desired value is formed. figure

Description

Object of the invention

Ziel der Erfindung ist ein Anfahrprozeß, bei dem sowohl Verdampfungsvorgänge vor der Umwälzpumpe als auch Thermoschocks in den Überhitzerstufen vermieden werden.The aim of the invention is a start-up process in which both evaporation processes before the circulating pump and thermal shocks in the superheater stages are avoided.

Explanation of the essence of the invention

Der Erfindung liegt die Aufgabe zugrunde, zur Erfüllung der Zielstellung ein Verfahren zum Anfahren von Dampfkesseln mit überlagertem Zwangsumlauf anzugeben, bei dem unter Beachtung des notwendigen Druckaufbaus im Verdampfer zur Sicherung der Unterkühlungsspanne zwischen Verdampfer und Ekonomiser eine maximal mögliche Dampfmenge produziert wird, um Thermoschocks bei der Inbetriebnahme der Einspritzungen auszuschließen. Gleichzeitig ist zur Realisierung des Verfahrens eine Anordnung zu schaffen.The invention has for its object to provide a method for starting steam boilers with superimposed forced circulation to fulfill the objective, in which, taking into account the necessary pressure buildup in the evaporator to secure the subcooling between evaporator and economizer a maximum amount of steam is produced to thermal shocks in the To exclude commissioning of the injections. At the same time to create an arrangement for the realization of the method.

Erfindungsgemäß wird in der Phase, in der die Einspritzungen in Betrieb zu nehmen sind, der Vordruckregler der HD-Reduzierstation mit einem Sollwert betrieben, der die Unterkühlungsspanne zwischen Ekonomiser und Verdampfer berücksichtigt und nach der Beziehung Xf= [θ·₅- (θ_Ει«, + K)] gebildet wird, in der θ₅= Sättigungstemperatur 9_Ei«j = Ekonomisertemperatur K = KonstantefürdieSicherheitsspanneAccording to the invention, in the phase in which the injections are to be put into operation, the admission pressure regulator of the HP reduction station is operated at a setpoint which takes into account the subcooling span between economizer and evaporator and according to the relationship Xf = [θ * ₅ - (θ _Ε ι ", + K)], in which θ ₅ = saturation temperature 9 _E ij = economizer temperature K = constant for the safety margin

bedeuten, wobei die Sättigungstemperatur eine Funktion des Druckes im Separator ist (θ₅ = f[p_sep]) und K minimal und in Abhängigkeit von der Überschwingweite des Anfahrreglers zu wählen ist.in which the saturation temperature is a function of the pressure in the separator (θ ₅ = f [p _se p]) and K is to be selected as a minimum and as a function of the overshoot of the starting controller.

Zur Realisierung des Verfahrens ist die Sollwertführung für den Vordruckregler der HD-Reduzierstation umschaltbar ausgebildet und in der Anfahrphase, in der die Einspritzungen in Betrieb zu nehmen sind, mit dem Ausgang eines zusätzlichen Anfahrreglers verbunden, dem als Eingangsgröße die Ekonomisertemperatur und als Sollwert die in einer vorgeordneten Recheneinheit aus dem im Separator gemessenen Druck ermittelte zugehörige Sättigungstemperatur vermindert um einen festgelegten Betrag als Konstante für die Sicherheitsspanne zugeführt sind.To implement the method, the setpoint control for the admission pressure regulator of the HD reduction station is designed to be switchable and in the start-up phase, in which the injections are to be put into operation, connected to the output of an additional start-up controller, the input as the Ekonomisertemperatur and as setpoint in a upstream computing unit determined from the measured pressure in the separator associated associated saturation temperature reduced by a specified amount as a constant for the safety margin are supplied.

embodiment

Die nähere Erläuterung erfolgt an Hand der Zeichnung, die auszugsweise ein Regelschema für die Vordruckregelung der HD-Reduzierstation (im folgenden HD-Station) zur Realisierung des Verfahrens darstellt.The detailed explanation will be made with reference to the drawing, which in part is a control scheme for the form control of HD reduction station (hereinafter HD station) to implement the method.

Die strichpunktierte Linie kennzeichnet den vorhandenen bekannten Vordruck-Regelkreis der HD-Station HDS. Regelgröße ist der Druck ρ in der Frischdampfleitung FD vor der HD-Station HDS; Stellorgan ist der Stellantrieb S der HD-Station HDS. Der Sollwert x_s für den Druck ρ liegt ebenfalls am Eingang des Pl-Reglers R des Regelkreises.The dot-dashed line indicates the existing known pre-pressure control loop of the HD station HDS. Controlled variable is the pressure ρ in the main steam line FD in front of the HD station HDS; Actuator is the actuator S of the HD station HDS. The setpoint x _s for the pressure ρ is also at the input of the PI controller R of the control loop.

Gemäß der Erfindung ist in der Sollwertzuführung ein Umschalter U angeordnet. Dieser ermöglicht im Anfahrbereich das Anlegen eines Sollwertes x_F, der von einem Anfahrregler AR geführt ist.According to the invention, a changeover switch U is arranged in the setpoint supply. This allows the creation of a setpoint x _F in the starting range, which is guided by a Anfahrregler AR.

Eingangsgröße dieses Anfahrreglers AR ist die Ekonomisertemperatur ö_Eko/ während sein Sollwert x_A in der Recheneinheit RE aus dem Meßwert des Druckes p_Sep im Separator nach der BeziehungInput variable of this starting controller AR is the Ekonomisertemperatur ö _{Eko /} while its setpoint x _A in the arithmetic unit RE from the measured value of the pressure p _Sep in the separator according to the relationship

x_A = ö_s - K bei ö_s = f(p_Sep)x _A = ö _s - K at ö _s = f (p _S ep)

entsteht. arises.

Das Wirkprinzip ist folgendes:The operating principle is the following:

Der vorhandene Druckregelkreis der HD-Station bleibt bestehen, im Anfahrbereich wird der Sollwert aber jetzt vom Anfahrregler AR geführt (x_F).The existing pressure control loop of the HD station remains in place, but in the approach area the setpoint is now guided by the approach control AR (x _F ).

Der Sollwert x_Afür den Anfahrregler wird so gebildet, daß ein konstanter Differenzbetrag zwischen Sättigungstemperatur 9_Άο gehalten wird (K).The setpoint x _A for the Anfahrregler is formed so that a constant difference between saturation temperature 9 _{Άο is} held (K).

Die Ekonomisertemperatur darf zur Vermeidung von Verdampfung nie über die Sättigungstemperatur kommen.The economizer temperature must never exceed the saturation temperature to avoid evaporation.

Wird der konstante Differenzbetrag K infolge Erhöhung der Ekonomisertemperatur unterschritten, so wird durch den Anfahrregler AR der Sollwert x_Ffür den Druckregler R der HD-Station HDS erhöht. Über die HD-Station HDS wird eine Drucksteigerung im System ausgelöst. Mit der Druckerhöhung ist eine Erhöhung der Sättigungstemperatur verbunden.If the constant difference amount K is undershot as a result of an increase in the economizer temperature, then the setpoint value x _F for the pressure regulator R of the HD station HDS is increased by the approach controller AR. The HD-Station HDS raises the pressure in the system. The increase in pressure is associated with an increase in the saturation temperature.

Claims

1. A method for starting a pulverized coal-fired boiler with superimposed forced circulation, wherein the pressure build-up in the evaporator taking into account the necessary subcooling between evaporator and economizer takes place and the HD-reducing station is operated with a form control, characterized in that in the phase in which the Injections are to be put into operation, the pre-pressure regulator of the HP reduction station is operated at a setpoint that takes into account the subcooling span and according to the relationship

x _F = [O ₅ - (Oeko + K)] is formed,

in the

θ ₃ = saturation temperature

$ Eko ⁼ Economizer temperature

K = constant for subcooling span

mean, wherein the saturation temperature is derived as a function of pressure from a pressure measurement in the separator and K is to be selected minimally and in dependence on the overshoot of the starting controller.

2. Arrangement for starting a pulverized coal-fired boiler with superimposed forced circulation, in which the pressure build-up in the evaporator taking into account the necessary subcooling between evaporator and economizer takes place and the HD-Reduzierstation is equipped with a pressure control circuit, characterized in that the setpoint supply of the form control valve formed switchable and is connected in the starting phase, in which the injections are put into operation, with the output of a Anfahrreglers (AR), which as an input value the Ekonomisertemperatur (e _Ek0) and as a setpoint value (x _a) in an upstream processing unit (RE) from the associated saturation temperature (O ₃ ) determined in the separator (psep) is reduced by a fixed _t as a constant for the subcooling span.

For this 1 page drawing

Field of application of the invention

The invention relates to a method and an arrangement for starting a steam boiler with superimposed forced circulation.

Characteristic of the known state of the art

Steam boilers are started by means of pilot burners, the combustion chamber is brought to a temperature at which, if the steam boiler is equipped with mills, the pulverized coal safely ignites and burns. (In general, steam generators are started with a closed high-pressure bypass station.) The function of the pilot burners is to bring the evaporator contents to a boil and build up the pressure in the live steam system. After both the high-pressure and the low-pressure bypass stations have a certain degree of opening, with which the flow through the water-steam tract is ensured, the Definitivfeuerung is successively activated to raise the parameters in the water-steam tract according to the approach target. Due to temporarily unfavorable fuel-to-steam ratio, some superheater stages will soon reach their limit temperature if the superheater temperatures are not regulated. The temperature control is usually done with water, which is injected before the superheater stage. In order to exclude thermal shock in the superheater stages to be controlled during injection, a minimum steam flow rate must be present in the amount of injection water so that the steam is still superheated after injection. Therefore, the start-up technology should be geared so that the switching of the Definitivfeuerung is based on maximum possible steam production to create the conditions for temperature control. In evaporator systems with circulation pumps, which are connected in the main stream, but there is a requirement to ensure by appropriate pressure build-up in the evaporator, the subcooling to Ekonomiser, so that the starting process is not interrupted by failure of the circulation pump.

Therefore, in such evaporator systems the pressure build-up in the evaporator all the attention paid, so that thermal shocks are not excluded in the superheater stages when commissioning the injections. A method for starting a steam boiler with circulation pumps (DE-PS 2845021) is known, in which water is fed via a line into the superheater stage located above the combustion chamber and vaporized to save ignition fuel. In order to reduce the heat consumption for start-up and exclude pre-evaporation in the economizer, it is primarily oriented to the pressure build-up in the live steam system until reaching the triggering pressure for the turbine. Thus, the concerns of steam cooling to comply with the limit temperatures for the individual superheater stages is not taken into account.