The visible “white smoke” emitted from chimneys is usually water vapor condensed into tiny droplets, forming a white plume. During combustion, water vapor mixes with flue gas and, when discharged into the atmosphere, cools below the dew point. This causes condensation of vapor into fine liquid droplets. The density of the white plume depends on factors such as flue gas humidity, ambient temperature and humidity, and particulate concentration in the flue gas.
White plume control is often linked to the treatment of pollutants like SOx and NOx. Taiwan Heat Transfer Corporation collaborates with flue gas pollution control partners to provide integrated solutions including flue gas treatment, white plume elimination, and heat recovery.
Common Methods for White Plume Elimination:
- Direct Flue Gas Heating
Heating flue gas above the dew point to reduce relative humidity. This method has high energy consumption and may only shift condensation problems downstream, causing potential corrosion.
- Condensation and Dehumidification
Cooling flue gas to forcibly condense and remove moisture, lowering emission humidity. This can be done via direct condensation (spray cooling) or indirect condensation (heat exchanger cooling). Attention must be paid to dew point corrosion and dioxin formation during cooling.
- Air Dilution
Introducing dry air to mix with flue gas and reduce overall humidity. This method is low cost but less effective in low-temperature, high-humidity environments and increases total flue gas volume.
- MGGH Method (Media Gas Gas Heater)
The heat transfer medium water is heated in a heat exchanger on the original flue duct, then sent to a reheater on the downstream flue to warm the flue gas. The circulating water is pumped back to the heat exchanger. A pressure-stabilizing expansion tank ensures stable pressure during temperature changes. This method requires no external heat source, saving energy, and allows heat recovery from excess flue gas heat.
Advantages of MGGH:
- Virtually zero energy consumption
- Chimney inlet temperature reaches about 80–90 °C, reducing internal low-temperature corrosion
- Reduces evaporation from flue gas desulfurization (FGD) towers, saving water