Industrial Desulfurization Nozzles: FGD & DeSOx Spray Nozzles

Industrial desulfurization nozzles are used in wet flue gas desulfurization (FGD) systems to distribute limestone slurry inside absorber towers. The spray creates the gas-liquid contact required to remove sulfur dioxide (SO₂) from flue gas.

FGD nozzles must handle abrasive solids, corrosive slurry, high flow rates, and continuous operation. Large full cone and spiral nozzles are commonly used, with silicon carbide (SiC) and stainless steel among the main material options.

This guide covers FGD nozzle types, materials, common wear problems, and the key parameters used for nozzle selection.

What Is an Industrial Desulfurization Nozzle?

An industrial desulfurization nozzle, also called an FGD nozzle, DeSOx nozzle, or flue gas desulfurization nozzle, is installed on spray headers inside a scrubber or absorber tower.

In a wet FGD system, limestone slurry is pumped through the spray headers and discharged downward through multiple nozzles. At the same time, flue gas flows upward through the absorber.

The nozzle creates a controlled spray pattern that provides sufficient gas-liquid contact for SO₂ absorption. The absorbed sulfur compounds react with calcium-based absorbents in the slurry.

FGD nozzles operate under conditions that are more severe than many conventional industrial spray applications:

• High suspended solids
• Abrasive limestone particles
• Corrosive slurry
• High flow rates
• Continuous operation

Nozzle wear, blockage, or changes in spray distribution can affect the performance of the spray layer.

How Do FGD Spray Nozzles Work?

The droplets travel downward through the upward-moving flue gas. This creates the gas-liquid contact needed for SO₂ absorption.

The simplified chemical reactions are:

SO₂ + H₂O → H₂SO₃

CaCO₃ + H₂SO₃ → CaSO₃ + CO₂ + H₂O

In forced-oxidation systems, calcium sulfite is further oxidized to gypsum.

The nozzle therefore needs to provide the required flow rate, spray angle, distribution, and droplet characteristics while maintaining stable performance as the nozzle wears.

Full Cone vs. Spiral Nozzles

Large full cone and spiral nozzles are two common designs for wet FGD spray systems. They use different internal flow paths and produce different spray distributions.

Large Full Cone Nozzles

A large full cone nozzle produces a spray cone filled with liquid across the projected area. This design is useful when uniform liquid distribution is a primary requirement.

FGD full cone nozzles typically use large flow passages to reduce blockage risk when handling slurry. Their internal flow geometry generates the rotational motion required to form the full cone pattern.

The main consideration is passage wear and blockage. Oversized particles, foreign material, or deposits can restrict the internal flow path if slurry conditioning is inadequate.

Spiral Nozzles

A spiral nozzle uses an open helical flow path to produce multiple conical sheets. The open structure provides good resistance to blockage and allows the nozzle to handle slurry containing suspended solids.

Spiral nozzles are particularly useful where clogging is a major concern. However, their spray distribution differs from a true full cone, so nozzle spacing and spray overlap need to be considered during header design.

Feature	Large Full Cone Nozzle	Spiral Nozzle
Spray Pattern	Full cone	Wide cone
Distribution	More uniform	Depends on geometry and layout
Clogging resistance	Good	Very good
Slurry Handling	Good	Excellent
Main advantage	Spray uniformity	Open flow path
Maintenance	Low	Very low
Typical Use	Large absorber towers	High-solid slurry applications

Neither design is universally better. The selection should be based on slurry properties, required flow, operating pressure, absorber dimensions, and spray-layer layout.

Which Materials Are Used for FGD Nozzles?

FGD slurry combines abrasive solids with potentially corrosive chemicals. Material selection therefore needs to consider both erosion and corrosion.

Silicon Carbide

Silicon carbide (SiC) is widely used for demanding FGD applications because of its high hardness and resistance to erosion and corrosion.

Reaction-bonded SiC is commonly used for general heavy-duty service, while sintered SiC provides higher hardness and wear resistance for more severe applications.

Stainless Steel

316L stainless steel provides good corrosion resistance and mechanical strength but has lower erosion resistance than SiC in abrasive slurry.

Duplex stainless steel offers higher strength and good resistance to chloride-related corrosion. It can be considered when mechanical loading and corrosion resistance are important.

Material	Erosion Resistance	Corrosion Resistance	Typical Use
Sintered SiC	Excellent	Excellent	Severe abrasive slurry
Reaction-bonded SiC	Very good	Excellent	General FGD service
Duplex stainless steel	Moderate	Very good	Corrosive service
316L stainless steel	Low–moderate	Good	Less abrasive slurry

PP and PVDF may be suitable for selected auxiliary services, but their temperature and mechanical limitations generally restrict their use in main FGD slurry spray layers.

Common FGD Nozzle Problems

Erosion

Abrasive particles gradually wear the nozzle orifice and internal surfaces. As the opening becomes larger, flow rate can increase at the same pressure and the spray pattern can change.

Typical signs include increased flow, distorted spray distribution, and uneven coverage.

Clogging and Scaling

Oversized particles, foreign material, and mineral deposits can restrict nozzle passages. Gypsum scaling can also change the effective flow area and spray pattern.

Spiral nozzles have an advantage in clogging-prone applications because of their open flow path. Proper slurry screening and process control remain important for all nozzle types.

Erosion-Corrosion

In corrosive slurry, particle impact can remove the protective surface layer and expose fresh material to chemical attack. This combined mechanism can accelerate wear in metallic nozzles.

For severe abrasive service, SiC is often considered because it provides both high wear resistance and chemical stability.

How to Select an FGD Nozzle

A practical FGD nozzle selection starts with the operating data.

1. Slurry conditions - Check solids concentration, particle size, temperature, pH, and chloride level where available.

2. Flow rate - Determine the required total slurry flow and flow per nozzle for each spray layer.

3. Operating pressure - Confirm the actual pressure available at the nozzle inlet, including losses through headers, valves, and fittings.

4. Spray coverage - Match the nozzle spray angle and flow pattern to the absorber diameter, nozzle elevation, spacing, and header arrangement.

5. Material - Select SiC for severe abrasive service and consider stainless steel where erosion conditions are less demanding.

6. Maintenance - Define how flow rate, spray pattern, and nozzle wear will be checked during operation.

A basic selection workflow is:

Slurry Data → Flow Rate → Pressure → Spray Pattern → Nozzle Type → Material → Inspection

For replacement projects, the existing nozzle dimensions and header connection should also be confirmed before selecting a new model.

Where Are Desulfurization Nozzles Used?

Industrial desulfurization nozzles are used in wet scrubbers and FGD systems across several industries.

Industry	Typical Application
Power generation	Limestone slurry spraying in wet FGD absorbers
Steel	Flue gas treatment from sintering and related processes
Cement	SO₂ control in kiln exhaust treatment
Waste-to-energy	Flue gas cleaning
Chemical processing	Acidic gas scrubbing
Metal smelting	SO₂ removal from process gases

Operating conditions can vary significantly between applications, so nozzle specifications should always be matched to the actual process.

FAQ

Large full cone and spiral nozzles are commonly used. Full cone nozzles are suitable where uniform spray distribution is important, while spiral nozzles are useful where clogging resistance and open flow passages are priorities.

Silicon carbide is widely used for abrasive limestone slurry because of its high erosion and corrosion resistance. Stainless steel may be suitable for less abrasive conditions.

The open spiral flow path reduces the risk of blockage and allows suspended solids to pass through more easily than many designs with narrow internal passages.

4. How long do FGD nozzles last?

Service life depends on slurry concentration, particle size, pressure, material, and operating conditions. SiC generally provides longer wear resistance than stainless steel in highly abrasive slurry service.

Flow-rate changes at a known pressure can indicate orifice erosion. Spray-pattern testing can identify uneven discharge, partial blockage, or other changes that may not be visible from an external inspection.

The performance of an FGD spray system depends on consistent slurry distribution and nozzle stability. Full cone and spiral nozzles each have specific advantages, while material selection should reflect the actual erosion and corrosion conditions.

Need Help Selecting an FGD Nozzle?

Send us your slurry concentration, particle size, required flow rate, operating pressure, spray angle, connection size, and absorber dimensions. Our engineering team can help evaluate the appropriate nozzle type and material for your DeSOx application.