Views: 0 Author: Site Editor Publish Time: 2025-08-14 Origin: Site
1. Recovers Waste Heat from Flue Gases
Boilers generate high-temperature flue gases (typically 300–500°C) as a byproduct of fuel combustion. Without an economizer, these gases would exit the chimney, losing significant heat to the atmosphere.
The economizer intercepts these flue gases and transfers their residual heat to the feedwater (water supplied to the boiler) before it enters the boiler’s drum or evaporator.
By preheating the feedwater (e.g., raising its temperature from 100°C to 200°C), less fuel is required to convert the water into steam in the boiler. This directly reduces fuel consumption for the same steam output.
2. Increases Boiler Thermal Efficiency
Boiler efficiency is defined as the ratio of useful heat output (steam energy) to the heat input (fuel energy).
Without an economizer, a substantial portion of fuel energy is wasted in flue gases (often 15–30% of input heat).
By recovering this waste heat, the economizer reduces the “heat loss” in flue gases. For example, a well-designed economizer can lower flue gas exit temperatures by 100–200°C, cutting heat loss by 5–15%.
This directly boosts boiler efficiency, which typically rises from 70–80% (without an economizer) to 85–90% (with one).
3. Reduces Fuel Consumption and Emissions
Lower fuel use translates to multiple benefits for the power plant:
Cost Savings: Reduced fuel consumption lowers operational expenses, a critical factor for plants relying on coal, natural gas, or oil.
Lower Emissions: Less fuel burned means fewer greenhouse gases (CO₂) and pollutants (NOₓ, SO₂) released, aligning with environmental regulations and sustainability goals.
4. Mitigates Thermal Stress on Boiler Components
Cold feedwater entering the boiler creates thermal stress on the boiler’s drum and tubes, as the temperature difference between the water and the hot boiler surfaces is large.
Preheating feedwater via the economizer reduces this temperature gap, minimizing thermal expansion/contraction of boiler materials.
This extends the lifespan of critical components (e.g., tubes, drums) by reducing wear and tear, lowering maintenance costs and unplanned downtime.
5. Enhances Steam Cycle Efficiency
In power plants, steam generated by the boiler drives turbines to produce electricity. The efficiency of this “steam cycle” depends on the steam’s temperature and pressure.
By preheating feedwater, the economizer allows the boiler to produce steam at higher temperatures/pressures (since less energy is spent on heating cold water).
Higher-quality steam (hotter, drier) improves turbine efficiency, as more energy is extracted from the steam during expansion in the turbine. This cascades to higher overall plant efficiency (i.e., more electricity generated per unit of fuel).
6. Enables Synergy with Other Systems
In some plants, economizers work alongside other heat-recovery devices (e.g., air preheaters, condensing heat exchangers) to maximize waste heat utilization:
For example, after passing through the economizer, flue gases may still retain enough heat to preheat combustion air (via an air preheater), further reducing fuel needs.
In combined-cycle plants (using both gas and steam turbines), economizers can integrate with the gas turbine’s exhaust heat recovery steam generator (HRSG) to optimize overall cycle efficiency.
