Flue Gas Desulfurization Market: Key Types & Applications

FGD plays a pivotal role in mitigating the harmful effects of air pollution on public health and the environment. Industries, particularly those heavily reliant on fossil fuels like coal, have historically emitted vast amounts of sulfur dioxide into the air, contributing to higher pollution levels. FGD refines sulfur dioxide (SO2), which serves as the primary concern, and acts as an indicator for the broader group of gaseous sulfur oxides (SOx).

As per Inkwood Research, the global flue gas desulfurization market is set to grow with a 4.90% CAGR between 2023 to 2032. While other gaseous SOx, such as SO3, exist in the atmosphere, their concentrations are notably lower than SO2. Short-term exposure to SO2 can detrimentally affect human respiratory systems, making breathing difficult, particularly for individuals with asthma, including children particularly sensitive to these effects. At elevated concentrations, they can also damage trees and plants by harming foliage and impeding growth.

Flue Gas Desulfurization Market - Inkwood Research

Mapping the Evolution of Flue Gas Desulfurization Technologies: Global FGD Market

Before the widespread adoption of FGD, industries primarily relied on combustion modifications, coal washing, limestone injection, and fuel switching to reduce sulfur dioxide emissions. These methods are primarily focused on preventing SO2 formation during the combustion process itself, rather than capturing it after combustion, like FGD. 

However, these methods often proved insufficient in achieving the desired emission reductions, leading to the development and implementation of FGD technologies. FGD systems have gradually replaced or supplemented traditional emission control methods due to their effectiveness in capturing sulfur dioxide.

How Does Flue Gas Desulfurization Work?

Multiple techniques exist for extracting SO2 from flue gases, with FGD systems typically removing 95% of SO2 in a typical coal-fired power plant. FGD primarily employs two methods, dry or wet scrubbing, to ensure compliance with regulations set by the EPA’s Effluent Limitation Guidelines (ELG).

The wet process has emerged as the primary method of flue gas desulfurization in large, fossil-fueled power plants. In this method, flue gases are saturated with steam containing an absorbent in an aqueous solution. 

Absorbents such as ammonia or sodium sulfite are utilized, although the widespread use of lime or limestone slurry, known as wet limestone scrubbing, is common. Within a scrubber tower or absorber tower, the dirty flue gas comes into contact with a water and limestone mixture (scrubbing slurry), facilitating the chemical bonding of most sulfur dioxide.

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Flue Gas Desulfurization (FGD) Market: Top 3 Types 

The burning of fossil fuels by power plants and industrial facilities represents the largest source of SO2 in the atmosphere. Moreover, smaller contributors to SO2 emissions encompass industrial processes such as metal extraction from ore, natural phenomena like volcanoes, and transportation means such as locomotives, ships, and other vehicles, as well as heavy equipment burning fuel with high sulfur content. 

FGD provides a means to reduce these emissions and meet stringent environmental regulations imposed by governments worldwide. On that note, let’s define the top 3 types of FGD systems – 

  • Wet FGD Systems

Wet flue gas desulfurization (WFGD) is the leading technology for controlling sulfur dioxide (SO₂) emissions, commonly using an alkaline lime slurry. This slurry absorbs SO₂ in spray scrubbers, converting it into calcium sulfite, which can be processed into gypsum. 

WFGD systems, enhanced with sieve trays, have been widely adopted, with over 100 GW of capacity since 2014. While the primary focus has been on SO₂ removal, dust removal potential remains less explored. Companies like Babcock & Wilcox and Hamon manufacture these high-efficiency systems.

  • Spray Dry FGD Systems

Flue gas desulfurization (FGD) using spray-dry absorption combined with bag-house particulate collection is an effective alternative to wet scrubbing for boilers burning low- to medium-sulfur coal, fuel oil, or waste incinerators. In this process, hot flue gas is sprayed with an alkaline lime-water slurry in a reaction chamber for 10-15 seconds. The droplets evaporate, absorbing sulfur dioxide (SO₂) and reacting with the sorbent.

Spray-dry FGD is primarily used with coal-fired boilers and is increasingly applied for heavy oil combustion in some European countries, such as Italy. The process involves complex interactions of fluid dynamics, heat and mass transfer, and chemical reactions, which can be divided into three stages: droplet deceleration, constant rate drying with sulfur removal, and a final drying stage. This method provides a cost-effective solution for SO₂ removal from flue gases.

  • Dry FGD Systems

Dry FGD systems consume less electricity, produce no liquid waste, and have lower startup and operating costs compared to wet FGD systems. The dry waste produced can be safely disposed of in landfills alongside fly ash. However, dry FGD systems require higher expenditure and exhibit lower reagent utilization efficiency to achieve the same SO₂ removal levels as wet FGD systems.

In dry FGD systems, lime is used as a reagent to eliminate gaseous pollutants. There are two common techniques: dry injection and spray drying. Dry injection involves directly injecting dry, hydrated lime into the flue gas duct, whereas spray drying injects atomized lime slurry into a separate vessel. Both methods produce a dry product, which is collected by particulate control equipment for further processing.

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Evolution and Efficiency of FGD Systems in Combating SO2 Emissions:

Flue-gas desulfurization (FGD) systems have been employed since the late 1960s to mitigate sulfur dioxide (SO2) emissions from coal-fired power plants. These systems yield solids, the second-largest coal combustion product (CCP) stream by volume, surpassed only by fly ash.

FGD, also known as scrubbers, is a process aimed at removing SO2 emissions from industrial facility exhaust gases, notably those from coal-fired power plants. SO2 is a significant contributor to air pollution, resulting in acid rain, respiratory ailments, and environmental degradation. FGD systems work to mitigate these adverse effects by capturing and neutralizing SO2 before its release into the atmosphere.

Flue gas desulfurization systems, or flue gas scrubbers, achieve sulfur removal efficiencies ranging from 50% to 98%. Wet scrubbers generally offer the highest removal rates, while dry scrubbers tend to have lower efficiency. FGD systems find applications in various combustion units, including – 

  • utility and industrial boilers, 
  • waste incinerators, 
  • refineries, 
  • kilns, 
  • smelters, and 
  • sulfuric acid plants.

Future Growth Prospects – 

Looking forward, the future of FGD is promising as industries prioritize sustainability and regulatory compliance. Technological innovations, such as advanced materials and process optimizations, are expected to enhance FGD systems’ performance and viability. 

Moreover, emerging trends like carbon capture and utilization (CCU) offer new opportunities for synergies between emission reduction technologies. By reducing sulfur dioxide emissions and mitigating air pollution, FGD plays a crucial role in promoting environmental sustainability and public health. Moving towards a greener future, FGD will undoubtedly remain a cornerstone of emissions control and clean energy initiatives.

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By Aishwarya Mishra

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    There are several types of flue gas desulfurization systems, including wet scrubbers, dry scrubbers, and semi-dry scrubbers. Wet scrubbers use a liquid sorbent to remove sulfur dioxide, while dry scrubbers utilize a dry sorbent or absorbent material. Semi-dry scrubbers combine elements of both wet and dry scrubbing processes.

    Flue gas desulfurization gypsum, also known as FGD gypsum, is a by-product generated during the Flue Gas Desulfurization process. It is formed when calcium-based sorbents, such as limestone or lime, react with sulfur dioxide in the flue gas, resulting in the production of calcium sulfite/sulfate. FGD gypsum has various uses, including in the construction industry as a building material and in agriculture as a soil amendment.