Technical Discussion-----Issue 14 (Rewards for active participation)

Conditions for the “full furnace extinguishment” action: 1. The flame monitoring system is unreliable； 2. Malfunction of thermal protection.

Flame extinguished in three layers； With 3/4 of the corner flames extinguished as a condition, full furnace flame monitoring is a basic function of FSSS and serves as the main basis for protective actions. Full-furnace flame monitoring mainly includes layer-wise flame signal detection, full-furnace fire extinction detection, and flame surveillance. 1) “Layered” flame signal detection: In coal powder boilers with circular combustion at the four corners, the flame detector probes are generally placed in the secondary air inlets located between two layers of coal powder nozzles; the direction of these probes is aimed at the central fire ball in the furnace, so as to monitor the coal powder flames in the nozzles adjacent to each other, both above and below. The signals from the four flame detector probes installed at the four corners of the same floor are sent to the same flame detector control chassis. “Logic for detecting “flame” signals at a layer: When two probes in the same layer send a “flame present” signal, it is considered that there is a flame in that layer ； When three probes on the same layer send a “no flame” signal, it is considered that there is no flame on that layer. In a intermediate storage-type coal grinding system, where one powder feeder serves one coal powder nozzle, the situation is more complex than in a direct-fired coal grinding system where one coal grinder serves the coal powder nozzles at the four corners of the same layer; however, it remains reasonable to apply a \"four-select-two\" logic. 2) Full furnace fire extinguishment detection: The full furnace fire extinguishment detection is carried out using a “voting” mechanism. Since the determination of whether the entire furnace has been extinguished depends not only on the condition of the flame in the coal powder layer but also on that of the flame in the oil layer, the voting process takes into account both the coal powder layer and the oil layer. Only when a \"fire extinguish\" command is issued simultaneously for both the coal powder layer and the oil layer can it be confirmed that there is no fire in the entire furnace. The flame signal of each “layer” is combined with the operating condition of the coal powder nozzles in the adjacent layer to form a single “voting” signal for that coal powder layer. When there is a flame in oil layers 2/4, it is possible to support full-furnace combustion without any fire-extinguishing signal being issued; whereas when there is no flame in oil layer 3/4, those oil layers \"vote\" to extinguish the fire. “The \"signal indicating that coal powder has been supplied to a certain layer\" means that coal powder has entered the furnace through the coal powder nozzles of that layer; this is characteristic of a direct-fired coal grinding system, indicating that the coal feeder and the coal grinder have been started and have been operating for some time ； For the intermediate storage-type coal grinding system, the feeders are matched one-to-one with the coal powder nozzles, indicating that 2/4 or more of the feeders at this level have been activated. “The existing layer coal feeding confirmation signal is a condition for generating the \"whole furnace fire out\" signal; in other words, the generation of the \"whole furnace fire out\" signal requires a coal powder feeding signal, and without such a signal, the \"whole furnace fire out\" signal will not be generated. When the “Existing layer powder feeding confirmed” signal is 1 and the votes for each layer are all no fire, the “Whole furnace extinguished” signal is issued. During a normal shutdown, the “complete furnace extinguishment” signal will not appear, as the oil layer is activated before the shutdown to ensure stable combustion; the oil layer signals that there is a flame” ； Then stop feeding powder and exit by selecting “Powder fed for existing layer confirmed”; this way, the “Whole furnace extinguished” signal will not appear. 3) Flame monitoring: Flame monitoring provides operators with intuitive signals through probes installed above the furnace, allowing them to observe the combustion condition, assess the stability of combustion, and determine whether there is a complete cessation of combustion throughout the furnace.