Views: 0 Author: Site Editor Publish Time: 2026-02-27 Origin: Site
In modern thermal power plants, stringent environmental regulations require the abatement of sulfur dioxide (SO₂) emissions generated from coal and oil combustion. Wet Flue Gas Desulfurization (WFGD) is a widely adopted technology for removing SO₂ from flue gas with high efficiency. A critical component of many advanced WFGD systems is the Gas-Gas Heat Exchanger (GGH)—a device that significantly improves thermal performance, reduces energy consumption, and enhances overall system efficiency.
A Gas-Gas Heat Exchanger is a heat recovery device installed upstream of the WFGD absorber. Its primary function is to transfer heat between the hot incoming flue gas and the cooler cleaned flue gas exiting the absorber. By leveraging counter-flow or parallel-flow arrangements, the GGH enables the system to reclaim thermal energy that would otherwise be wasted.
In a conventional WFGD process:
Flue gas exits the boiler at high temperature (typically 120–180°C).
The flue gas must be cooled before entering the absorber to optimize SO₂ removal and protect internal components.
The GGH pre-cools the hot flue gas using the cooler, cleaned flue gas leaving the absorber.
The result is:
Reduced energy demand for additional cooling.
More stable absorber temperature.
Improved performance of downstream pollution control equipment.
The GGH typically consists of a bundle of heat-exchange tubes or plates configured within a casing that separates the hot and cold gas streams. The design ensures efficient thermal exchange while preventing cross-contamination.
| Stream | Direction | Purpose |
|---|---|---|
| Hot flue gas | Enters GGH from boiler | Transfers heat out |
| Cleaned cool gas | Enters GGH from absorber outlet | Absorbs heat |
Heat transfer occurs without physical contact between the two streams, preserving gas quality and preventing moisture carryover.
By recuperating heat from the cleaned flue gas, the GGH reduces the temperature differential across the absorber. This minimizes the need for external cooling media (e.g., water sprays or cooling coils), lowering parasitic loads.
A lower absorber inlet temperature can decrease the requirement for supplemental cooling water, which is a significant operational and cost advantage, especially in water-scarce regions.
Optimal absorber temperatures enhance the solubility of SO₂ into the scrubbing liquor, improving removal efficiency and reducing reagent consumption.
Stable temperatures can improve the performance of:
Electrostatic precipitators (ESPs) upstream of the GGH.
Mist eliminators downstream of the absorber.
Reclaiming heat with a GGH results in lower flue gas temperatures at stack release, which helps avoid visible plumes and meets regulatory emission standards.
GGH internals must withstand:
High temperatures
Corrosive flue gas components (SO₂, SO₃, water vapor)
Common materials include:
High-grade stainless steel
Corrosion-resistant alloys
Design must account for:
Thermal expansion and contraction
Avoidance of flow bypass
Minimizing pressure drop
GGH must be engineered to fit within:
Existing ductwork geometry
System control architectures
Maintenance access routes
Plant engineers and environmental compliance teams typically evaluate GGH performance based on:
| Metric | Description |
|---|---|
| Approach Temperature | Difference between temperatures of the two gas streams at closest approach—lower is better |
| Pressure Drop | Impacts fan power consumption—design aims to minimize it |
| Thermal Effectiveness | Ratio of actual heat transfer to maximum possible heat transfer |
Numerous coal-fired power plants across Europe, Asia, and North America have retrofitted or designed new WFGD systems with GGHs. Outcomes commonly include:
10–25% reduction in cooling water usage
3–8% improvement in SO₂ removal efficiency
Noticeable reductions in auxiliary power consumption
These improvements translate to lower operating costs and higher regulatory compliance margins.
The Gas-Gas Heat Exchanger (GGH) is a pivotal technology in modern WFGD systems for thermal power plants. By capturing and reusing heat that would otherwise be lost, GGHs:
Boost thermal performance
Reduce operational costs
Improve pollutant removal effectiveness
Contribute to sustainability goals
As environmental standards tighten and plants seek higher efficiency, the GGH continues to be an indispensable component of advanced flue gas treatment systems.
