Overview of Flue Gas Waste Heat Recovery Technology

Flue gas waste heat recovery technology refers to a systematic method that converts the heat energy in industrial flue gas emissions into usable energy through high - efficiency heat exchange devices. This technology can significantly improve energy utilization efficiency, reduce energy consumption and carbon emissions, and is of great value especially in high - energy - consuming industries such as metallurgy, chemical engineering, and building materials.

 

Core Advantages and Energy - Saving Potential

1. Improved Energy Efficiency: Flue gas waste heat recovery can reuse the waste heat generated in the industrial production process. For example, the high - temperature flue gas (above 800°C) from a metallurgical furnace can be converted into steam for power generation through a waste heat boiler, with a recovery efficiency of over 70%. For low - temperature flue gas (such as the exhaust gas of a 65°C gas - fired boiler), the temperature can be reduced to 15°C using compression heat pump technology, and the recovered latent heat accounts for 11.9% of the low - calorific value of natural gas.

2. Outstanding Environmental Benefits: By reducing the flue gas emission temperature, the diffusion of pollutants such as sulfides and nitrogen oxides can be reduced. For example, after a gas - fired boiler adopts condensation technology, the condensation rate of water vapor in the flue gas can reach 91.38%, achieving both pollutant control and heat energy recovery simultaneously.

3. Remarkable Economic Benefits: Taking sintering waste heat power generation as an example, each ton of sinter can generate 18 - 23 kilowatt - hours of electricity, and the pay - back period of the entire system usually does not exceed 2 years.

 

Mainstream Technical Solutions and Application Scenarios

1. Air Pre - heating Method

 - Fixed Tube System: It is directly integrated into the industrial furnace body and is suitable for small - and medium - sized waste heat recovery scenarios. The heat transfer between gases can be enhanced through fins or studs to improve the heat exchange efficiency.

 - Rotary System: It is independently installed on the ground and is suitable for the large - scale continuous production of the steel or cement industry, capable of handling flue gas with large fluctuations in flow.

2. Heat Pump Coupling Technology

 - Compression Heat Pump System: It breaks through the cost limitation of traditional absorption heat pumps, deeply cools the flue gas temperature from 65°C to 15°C, and achieves full recovery of latent heat.

 - Humidification Technology: It increases the dew - point temperature of the flue gas through spray heat exchange, but there are difficulties in treating condensed water. It is suitable for medium - temperature scenarios with lower environmental protection requirements.

3. Integrated Solutions

 - Sintering Waste Heat Power Generation System: It integrates the flue, boiler, and steam turbine, and uses the exhaust gas (300 - 400°C) from the grate cooler for power generation. The key technologies include heat source parameter prediction and dynamic optimization to ensure the stable operation of the system under fluctuating flue gas conditions.

 - Heat Pipe Heat Exchange System: It adopts a double - loop design. The evaporation section absorbs the heat of the exhaust gas (200 - 300°C) from the OVEN furnace, and the condensation section pre - heats the combustion - supporting air to achieve a closed - loop cycle, increasing the heat recovery rate by 15% - 20%.

 

Technological Innovation and Industry Practice

1. Breakthrough in Anti - Blockage Technology: The new high - efficiency integrated system uses multi - stage filtering devices (as described in patent CN202510464267.4) combined with an intelligent ash - cleaning module to solve the problem of ash accumulation in traditional heat exchange tubes, extending the equipment operation cycle by over 30%.

2. Expansion of Cross - Industry Applications

 - Coal Chemical Industry: Waste heat boilers are used to convert the flue gas (above 1200°C) from the reformer into high - pressure steam to drive the chemical production process.

 - Electronic Manufacturing Industry: The waste heat of the 150°C exhaust gas is recovered during the display baking (OVEN furnace) process for heating the clean workshop, with a comprehensive energy - saving rate of up to 25%.

 

Future Development Trends

With the increasing demand for low - carbon manufacturing, flue gas waste heat recovery technology is developing towards intelligentization and multi - energy coupling. For example, real - time monitoring of flue gas parameters through the Internet of Things to dynamically adjust the heat exchange rate; or combining fuel cell technology to achieve combined heat and power generation. According to industry forecasts, the global market size of flue gas waste heat equipment will exceed 12 billion US dollars in 2025, and China is expected to account for 35% of the market share driven by policies.

 

Enterprises can select suitable waste heat recovery solutions by matching production process parameters. For flue gas with high dust content, it is recommended to give priority to the modular heat pipe system; in the scenario of gas - fired boilers, compression heat pump technology will become the mainstream choice for in - depth energy saving.