How Many Types of Waste Heat Recovery Methods Are There in Municipal Solid Waste Incineration Power Plants?
In the context of rapid urbanization, waste incineration power generation has become a key approach to addressing the challenge of municipal solid waste disposal. This process not only achieves waste reduction and harmless treatment, but also creates considerable economic and environmental value through energy recovery. However, along the energy conversion chain, a large amount of waste heat contained in flue gas is still neglected by many power plants, becoming an “invisible resource” that remains to be fully exploited.
I.Waste Heat Recovery: An Indispensable Energy Efficiency Engine for Municipal Solid Waste Incineration Power Plants
The essence of waste incineration power generation lies in converting the chemical energy contained in municipal solid waste into electrical energy. However, the conversion efficiency is typically only around 20%–25%, which means that more than 70% of the energy is lost in various forms, with flue gas waste heat accounting for a significant share. If not recovered, these high-temperature flue gases are discharged directly into the atmosphere, resulting not only in energy waste but also in a series of associated problems:
Significant energy losses: For every 20 °C reduction in flue gas temperature, the overall thermal efficiency of a power plant can increase by approximately 1%. Taking a waste incineration plant with a daily treatment capacity of 1,000 tons as an example, effective waste heat recovery can generate additional thermal energy equivalent to several thousand tons of standard coal annually.
Increased environmental pressure: Excessively high flue gas temperatures increase the load on downstream gas purification systems, adversely affecting the efficiency of deacidification, denitrification, and dust removal. Waste heat recovery helps lower the exhaust gas temperature and optimize the entire flue gas treatment process, thereby further reducing pollutant emission concentrations.
Limited economic performance: Under the “dual-carbon” goals, carbon trading markets are becoming increasingly mature, and each ton of reduced carbon dioxide emissions represents potential economic value. By improving energy efficiency, waste heat recovery systems directly create carbon assets for power plants.
II.Three Major Waste Heat Recovery Technology Pathways and Their Application Scenarios
1.Air Preheating Systems: A Core Link in Combustion Optimization
This is currently the most widely applied waste heat utilization method and offers the fastest return on investment. The system transfers heat from flue gas to the combustion air entering the incinerator through gas–gas heat exchangers.
Technical advantages:
Preheating air to 200-300℃can significantly increase furnace temperature and promote more complete waste combustion.
Reduces the formation conditions of harmful substances such as dioxins.
Lowers auxiliary fuel consumption, making it particularly suitable for seasonal regulation when treating low-calorific-value waste.
Application considerations: The heat exchange system should be designed with sufficient adjustability to accommodate fluctuations in waste composition, while avoiding low-temperature corrosion and ash deposition.
2.Steam Power Generation Systems: A Paradigm of Cascaded Energy Utilization
Beyond the conventional steam power generation cycle, low-temperature waste heat boilers are added to utilize flue gas waste heat for producing medium- and low-pressure steam, which in turn drives auxiliary turbine-generator units.
Technical characteristics:
Typically increases overall power generation by 3%–8%.
Organic Rankine Cycle (ORC) technology can be adopted to recover even lower-grade thermal energy.
As the system is coupled with the main steam system, precise control and parameter matching are required.
Typical case: After installing a waste heat boiler, a coastal waste incineration power plant achieved an additional annual power generation of 12 million kWh, with a payback period of less than four years.
3.Hot Water Supply Systems: A Link for Regional Energy Synergy
Hot water is produced through flue gas–water heat exchangers, with the temperature typically controlled within the range of 90–150 °C according to demand, enabling on-site energy utilization or regional distribution.
Multiple applications:
In-plant process heating (demineralized water systems, plant space heating).
Steam or heat supply to nearby industrial parks.
Winter heating for urban and residential areas.
Drying of sludge generated from landfill leachate treatment.
Synergistic benefits: When integrated into a district heating network, such systems can replace scattered small-scale boilers, achieving energy conservation and emission reduction at the regional level.
III.Technological Innovation: Development Directions for Next-Generation Waste Heat Recovery Systems
With advances in materials science and control technologies, a wide range of innovative solutions are emerging in the field of waste heat recovery:
1.Anti-corrosion and anti-fouling designs: In response to the highly corrosive and dust-laden nature of flue gas from waste incineration, new materials such as enamel-coated heat exchange tubes and fluoroplastic heat exchangers are employed, combined with intelligent soot-blowing systems, significantly extending equipment service life.
2.Application of heat pipe technology: By leveraging the high-efficiency heat transfer characteristics of heat pipes, small temperature-difference heat transfer can be achieved, enabling recovery of lower-grade waste heat. These systems are compact in structure and easy to maintain.
3.Digital twin systems: By establishing a digital replica of the waste heat recovery system, operating parameters can be optimized in real time, maintenance demands can be predicted, and overall system reliability and economic performance can be improved.
4.Multi-energy supply modes: By integrating waste heat recovery with absorption refrigeration, drying processes, and other technologies, diversified outputs of “heat–power–cooling–end-use” can be realized, meeting energy demands across different seasons and operating periods.
IV.Looking Ahead: The Role of Waste Heat Recovery in the Green Energy System
Against the backdrop of energy transition and the circular economy, the role of waste incineration power plants is shifting from that of “waste treatment facilities” to “urban energy factories.” As a key technology for increasing energy output and reducing environmental footprints, waste heat recovery is becoming increasingly valuable.
With the maturation of carbon trading markets and the tightening of environmental standards, high-efficiency waste heat recovery systems are no longer an “optional add-on,” but an essential tool for waste incineration power plants to achieve sustainable development and enhance their market competitiveness.