Water Savings for FGD and Thermal Plant Efficiency Improvement by Waste Heat Recovery from Flue Gas
Extraction of waste heat from flue gases of a thermal power plant before FGD and utilization of the same in Condensate cycle helps in reducing water consumption in FGD as well as enhancing energy efficiency.
Rationale
Water scarcity is a critical global challenge, with many major cities in India facing acute shortages. One significant area for water conservation is reducing water consumption in thermal power plants, which use a substantial portion of the country's water. Additionally, decarbonizing these plants is crucial to meet India's carbon reduction targets under its NDC. Enhancing the energy efficiency of thermal power plants is essential for the decarbonization of the power sector. A promising approach is recovering waste heat from flue gas before it reaches the Flue Gas Desulfurization (FGD) system and utilizing it in the plant’s feed water cycle. This method not only reduces water consumption significantly in the FGD process but also improves the overall efficiency of the thermal power plant.
Brief About the Technology/Works being carried out
Typically, hot flue gas from the air preheater enters the FGD absorber tower at around 125°C where it will be reduced to around 60°Cduring the FGD process. Utilization of this lost heat from the flue gases in power cycle can help in optimizing water consumption in FGD as well as enhancing energy efficiency of the thermal power unit.
Flue gas at 125°C shall be tapped from discharge of Booster fan of FGD system and after heat recovery, flue gas temperature shall be reduced to 65°C and the same shall be connected to main flue gas duct at the inlet of absorber tower. This leads to reduced consumption of water in the FGD absorber tower. Further, heat recovered from waste flue gas shall be used to heat condensate from Gland Steam Cooler outlet which will enhance thermal power unit efficiency.
NTPC recently issued an Expression of Interest (EOI) for setting up a pilot project for recovery of waste heat from flue gases and utilizing the same in the condensate cycle of thermal power plant.
Benefits of the Technology
Some of the benefits of using the technology are as follows:
- Reduction in water consumption in thermal power plants
- Improvement in energy efficiency of thermal power plant
- Reduction in CO2 emissions