3 sets of grate cooling-air systems shipped to Shandong
We have shipped 3 sets of grate cooling-air systems from our partner factory to Shandong.
Grate cooling-air systems are widely used in chain coal-fired boilers, biomass boilers and waste-incineration grate furnaces. They use air as the cooling medium to force-cool high-temperature parts such as grate bars, the grate frame, the stepped tiers and the pusher, preventing the metal from overheating, oxidizing, deforming or burning away. The heated cooling air is then recovered back into the furnace to support combustion, combining cooling and air supply in one.
Difference: primary air mainly supplies oxygen for combustion; cooling air focuses on protecting equipment. On some equipment the cooling air shares the primary-air supply, while incinerators mostly use a dedicated cooling-air system.
1. Main functions of the system
Protecting grate metal parts: the main combustion zone in the furnace can reach 850–1100°C, and heat-resistant cast-iron grate bars left above 600–700°C for long periods tend to oxidize, warp and crack. The cooling air carries heat away from the grate bars, keeping the base-metal temperature in a safe range and extending the service life of the grate bars, supports and step walls.
Preventing slagging and blocked air holes: the grate drop steps and pusher positions are prone to hanging slag and clinker; the cooling air lowers the wall temperature, reduces adhesion of molten ash and slag, and keeps the air holes from clogging.
Waste-heat recovery for energy saving: after the cooling air absorbs heat and warms up, the hot air is led into the primary/secondary-air ducts and sent into the furnace to support combustion, instead of being vented directly.
Preventing flashback damage at high temperature: the incinerator pusher and feed opening are prone to flashback; the dedicated cooling air isolates the hot flue gas and protects the pushing mechanism from burning out.
2. System composition (dedicated cooling-air type, typical of waste incinerators)
Cooling fan: generally a centrifugal fan that draws air from the boiler room, fitted with a silencer; the air volume and pressure are regulated by a variable-frequency drive.
Ductwork: a main air duct and branch ducts leading to each grate step tier, the pusher and the side guards.
Air chambers/cooling cavities: sealed cavities inside the grate steps and pusher, where the cooling air flows and exchanges heat.
Cooling air holes: tapered anti-clogging outlet holes through which the cooling air passes — part cools the components and part is injected into the furnace; they prevent ash and slag from flowing back into the ducts.
Control and monitoring elements: air-adjusting dampers, pressure gauges and temperature measuring points; the air-chamber pressure is monitored, and when an air hole clogs and the pressure rises, the system automatically increases the air volume and raises an alarm.
Hot-air return piping: the heated cooling air is collected and fed into the primary/secondary-air system.
Many small chain coal-fired boilers do not have a separate cooling fan: the primary air also cools the grate, passing up from the air chamber below through the gaps between the grate bars to both supply oxygen and cool the bars; the return run of the grate (the lower, non-combustion side) is naturally air-cooled in the environment beneath the furnace.
