A condition control system for e. g. a boiler is responsive to a pressure (or temperature) signal PR to generate an on/off firing signal 22 and a firing rate signal 26, by a proportional control path (via 50) and an on/off path (51). The system operates in 2 modes: proportional (modulating), and cycling, determined by a limit switch signal LS. To minimize the cycling rate when cycling, the system is forced into the lowest fire rate when first fired up; the rate of change of pressure is sensed (at 86) and the signal LS changes the mode to proportional if the pressure falls (indicating that the low fire rate is inadequate). In the proportional mode, integral action (via 57) is used to adjustthe setpoint PSET (via 44) to reach a stable operating state. In the cycling mode, the setpoint PSET is adjusted in dependence on the duty ratio of the cycles.

Pour optimiser le fonctionnement d'un four industriel, on ajuste le rapport de débit entre combustible et comburant de sorte à maintenir une quantité résiduelle fixe d'oxygène ou de CO dans les fumées de combustion. On mesure le débit de comburant et on ajuste en conséquence le débit de combustible conformément à des courbes de réponse du four préétablies.

Le dispositif comporte des moyens (22) pour choisir une température de fonctionnement du four, des moyens (14, 15) pour mesurer les débits de combustible resp. de comburant envoyés au brûleur (10), des moyens (6b, 6c, 7b, 7c) pour influencer lesdits débits, des moyens (21) pour comparer la température réelle du four à la température choisie d'avance et pour commander l'augmentation resp. la diminution du débit du comburant lorsque la température du four descend en--dessous resp. dépasse la température choisie, des moyens (24) pour calculer, en fonction du débit du comburant mesuré et de la température de fonctionnement choisie, le débit de combustible aboutissant à la quantité résiduelle désirée d'oxygène ou de CO dans les fumées de combustion et des moyens (25, 6b, 6c) pour ajuster le débit de combustible à la valeur calculée.

A stack damper controller for receiving operator input of a targetted combustion variable and for adjusting the position of the stack damper according to the target value. The controller may include a control logic module for each barrel of the heater, each module including several control loops. The apparatus for controlling at least one stack damper for maintaining stack oxygen content at an optimal level for minimising fuel consumption of a plurality of associated heater barrels in view of system conditions, comprises at least one fuel feed means for feeding fuel to at least one barrel; monitoring means (D.O.P.G.F.) for providing condition signals representative of a plurality of combustion system variables, the monitoring means measuring the excess stack oxygen level for each of the plurality of associated heater barrels and generating an excess stack oxygen signal for each of the barrels and also measuring fuel feed for each fuel feed means and generating a fuel entry signal associated with a fuel feed means; at least one damper control means responsive to a damper control signal for positioning a damper; and control means (21) including a logic module for each barrel.

A condition control system for e. g. a boiler is responsive to a pressure (or temperature) signal PR to generate an on/off firing signal 22 and a firing rate signal 26, by a proportional control path (via 50) and an on/off path (51). The system operates in 2 modes: proportional (modulating), and cycling, determined by a limit switch signal LS. To minimize the cycling rate when cycling, the system is forced into the lowest fire rate when first fired up; the rate of change of pressure is sensed (at 86) and the signal LS changes the mode to proportional if the pressure falls (indicating that the low fire rate is inadequate). In the proportional mode, integral action (via 57) is used to adjustthe setpoint PSET (via 44) to reach a stable operating state. In the cycling mode, the setpoint PSET is adjusted in dependence on the duty ratio of the cycles.

Bei einer Änderung der Brennerlast wird zunächst-ohne die erst später meßbaren Veränderungen in den Abgaswerten abzuwarten-diejenige Stellung der Einrichtung bzw. Einrichtungen (7, 22) zur Beeinflussung der Verbrennungsluftmenge angefahren, die ein in der Regelvorrichtung vorgesehener, vorzugsweise regenerierbarer Speicher (46) als den Wert gespeichert hat, den die Einrichtung bzw. Einrichtungen (7, 22) bei einer Brennerlast eingenommen hatte bzw. hatten, die der nunmehr angefahrenen Brennerlast entspricht. Daran anschließend erfolgt eine Feinnachregelung in Abhängigkeit von den Abgaswerten. Einzelheiten der Einrichtungen (7, 22) sowie zugeordnete Meßwertaufnehmer, Einstelleinrichtungen sowie deren Verknüpfung werden beschrieben.