Shell-and-tube Heat Exchangers for Flue Gas Desulfurization (FGD) Cooling

Shell-and-tube Heat Exchangers for Flue Gas Desulfurization (FGD) Cooling

Primarily used for flue gas cooling, slurry heating, process water cooling, and GGH auxiliary heat exchange, these are critical temperature control devices in desulfurization systems:

Flue gas cooling at the absorber inlet

High-temperature flue gas (120–180°C) is cooled before entering the desulfurization tower to protect the lining and reduce water consumption.

Reheating of Clean Flue Gas (GGH Auxiliary / Replacement)

Increases flue gas discharge temperature to prevent white smoke, corrosion, and tailing.

FGD Slurry / Process Water Cooling

Cools circulating slurry, discharge slurry, and process water to stabilize absorption efficiency.

Oxidation Air Cooling / Preheating

Controls oxidation air temperature to protect fans and the reaction environment.

Why Must Special-Grade Shell-and-Tube Heat Exchangers Be Used in FGD Applications?

The desulfurization environment is extremely harsh:

Contains SO₂, SO₃, HCl, HF, and dust

High humidity, prone to condensation forming dilute sulfuric acid and dilute hydrochloric acid

High chloride ion content and high dust abrasion

Temperatures fluctuate around the acid dew point, causing the most severe corrosion

Ordinary carbon steel and 304 stainless steel perforate quickly; even 316L is often insufficient.

Common Materials (by Operating Conditions)

ND Steel (09CrCuSb)

Resistant to sulfuric acid dew point corrosion; used for low-temperature, low-acid, and medium-to-low-temperature flue gas cooling.

316L

Suitable for mildly corrosive environments with low chloride ion levels.

2205 Duplex Stainless Steel

The most mainstream option with the best cost-performance ratio

Resistant to chloride ions, acids, and stress corrosion; suitable for most FGD slurry and flue gas cooling applications.

2507 / 254SMO / 654SMO

High-chloride, high-sulfur, high-temperature, highly corrosive operating conditions.

Titanium Tubes / Nickel-Based Alloys

Extreme corrosion, high chloride ion environments, and projects requiring high reliability.

How Shell-and-Tube Heat Exchangers Operate in FGD

Tube side: Cooling water / process water / hot water

Shell side: Flue gas or desulfurization slurry

Heat transfer occurs through the tube wall:

High-temperature flue gas → cooled

Cold slurry / process water → heated

Indirect heat exchange throughout the process; no direct mixing or spraying with flue gas; classified as dry or semi-dry heat exchange.

Features of Shell-and-Tube Heat Exchangers for FGD Cooling

High corrosion resistance: Resistant to acids, chlorine, and dew point corrosion

Fouling and wear resistance: Designed to withstand dust and gypsum particles

Reliable construction: Floating-head or U-tube designs accommodate thermal expansion and contraction

Easy to clean: Suitable for mechanical and chemical cleaning

Modular design, suitable for small and medium-sized boilers, sintering machines, coking plants, and waste-to-energy FGD systems

Typical Application Industries

Flue gas desulfurization (FGD) in coal-fired power plants

Flue gas desulfurization in steel plant sintering processes

Desulfurization in coking plants

FGD systems for waste-to-energy incineration

Desulfurization and denitrification in biomass boilers

Exhaust gas purification in chemical industry furnaces