Ceramic Valve Solutions for Flue Gas Desulfurization

Wet flue gas desulfurization (WFGD) process flow

KOWOV ceramic valves are designed for demanding FGD conditions involving abrasive slurry, corrosive chlorides, erosion, corrosion and crystallization

Flue gas desulphurization (FGD) systems are widely used in power plants and other industrial facilities to remove sulfur dioxide (SO₂) from flue gas

In wet FGD processes, limestone or lime reacts with sulfur dioxide inside the absorber. The process produces gypsum slurry and other solid-containing liquids that must be reliably transported, isolated and controlled

The combination of abrasive solid particles, chloride-containing process water, corrosive chemicals, scaling and crystallization places demanding requirements on valves used throughout the FGD process

KOWOV ceramic valves are designed for these severe operating conditions, providing reliable shut-off and flow control while reducing valve replacement and maintenance requirements

Target Industries

Power Plants
Steel Plants
Mining & Mineral Processing
Chemical Plants
Municipal Solid Waste Incineration
Cement Plants

Ceramic valves can be installed at critical slurry feed, circulation, isolation and control points throughout the FGD process

Typical Ceramic Valve Installation Points

Limestone slurry tank outlet
Limestone slurry feed line
Absorber slurry inlet
Gypsum slurry recirculation line
Hydrocyclone inlet and outlet
Belt filter feed line
Filtrate water line
Process water recirculation line
FGD wastewater line

Typical Operating Conditions

Operating Conditions

FGD valves operate in solid-liquid two-phase media containing abrasive particles and corrosive ions. The operating conditions vary according to the plant, process design and valve installation point

Typical Reference Conditions

Item	Typical Description	Characteristics
Process Media	Limestone slurry, lime slurry and gypsum slurry	Abrasive and corrosive
Fluid Type	Solid-liquid two-phase flow	Contains suspended solids
Working Pressure	Typically 6-16 bar	PN16/Class 150 commonly used
Differential Pressure	Typically ≤6 bar	Depends on valve location
Temperature	Typically below 100°C	No severe thermal shock
Solids Content	Approximately 20-25% in typical applications	High solids concentration
Particle Size	Approximately 10-100 μm in reference applications	Fine particles cause erosion
Chloride Content	Up to approximately 600 ppm in reference applications	Risk of chloride corrosion
Valve Size	Typically DN25-DN200	Other sizes available on request

Typical Process Media

Limestone Slurry, Hydrated Lime Slurry, Lime Slurry, Milk of Lime, Gypsum Slurry, Fly Ash Slurry, High-Chloride Process Water, FGD Wastewater, HCl Scrubber Water, Wash Water and Solids-Containing Filtrate

Characteristics of FGD Operating Conditions

Combined Erosion and Corrosion

High-velocity slurry and suspended solid particles continuously impact the valve flow passage and sealing surfaces. At the same time, corrosive ions attack exposed metallic components

The combined action of mechanical erosion and chemical corrosion results in rapid material loss and premature valve failure

Scaling, Crystallization and Wet-Dry Cycling

Sulfates, sulfites and other dissolved salts may penetrate surface linings and deposits. During shutdown or drying, these salts can crystallize and expand

Repeated wet-dry cycles may cause deposits, valve jamming, cracking, blistering or separation of conventional lining materials

Deterioration of Non-Metallic Linings

FGD slurry and corrosive process water may affect rubber and resin linings through swelling, softening, permeation and chemical degradation

Typical failures include

Swelling
Delamination
Blistering
Cracking
Lining detachment
Loss of substrate protection

Acidic Condensate and Low-Temperature Corrosion

Acidic components in flue gas and condensate, including HCl, HF and sulfur-containing compounds, may cause severe corrosion when the temperature falls below the acid dew point

This is especially important at positions exposed to corrosive gas, condensate or wash water

Process Pain Points

Conventional Valve Materials and Designs

Common valve types used in FGD systems include:

Globe valves
Eccentric butterfly valves
Plug valves
Metal ball valves
Rubber-lined valves
Resin-lined valves

Typical metallic materials include 316L stainless steel and, for more corrosive applications, Hastelloy C-276

However, material selection alone does not fully solve the combined problems of abrasion, erosion, corrosion, scaling and crystallization

Typical Valve Failures

Conventional valves may experience

Rapid wear of the valve ball, disc and seats
Corrosion and pitting of metallic wetted parts
Damage to sealing surfaces
Leakage after repeated cycling
Scaling and material accumulation
Increased operating torque
Valve jamming
Lining swelling or delamination
Frequent maintenance and replacement

Short Replacement Cycles

In some severe FGD applications documented by KOWOV, conventional valves required replacement after only several months of operation

Typical historical replacement intervals included:

Control valves: approximately 6-10 months
On-off valves: approximately 12-30 months

Actual service life varies according to the medium, flow velocity, pressure drop, solids content, valve design and operating frequency

Maintenance and Shutdown Losses

Frequent valve failure may result in

Reduced absorber capacity
Environmental compliance risks
Increased maintenance and cleaning costs
Temporary piping and repair work
Higher consumption of water, electricity and chemicals
Frequent system flushing
Shortened equipment service life
Unplanned shutdowns and production losses

Improvement Opportunity

FGD service places much higher demands on valve wear and corrosion resistance than ordinary water or utility service

Frequent failure of conventional valves can become a major restriction on the continuous and stable operation of an FGD system. This creates a strong demand for improved valve materials, structures and application-specific solutions

Why Choose Ceramic Valves?

Superior Abrasion & Erosion Resistance

Composition of Limestone Slurry and Gypsum Slurry

The solid components include CaSO₄·2H₂O, CaCO₃, MgCO₃, inert substances, and sand/silt. The hardness of these solid particles can reach up to HRC 72

Given the installation locations and critical functions of slurry control valves, proper valve selection is extremely important for reliable on-site operation

Superior Corrosion Resistance

The corrosive ions present include SO₄²⁻ and Cl⁻

Characteristics of Desulphurization Media in Power Plants

As indicated by the composition of desulphurization slurry, the media in power plant FGD systems contain both hard solid particles and highly corrosive chloride ions (Cl⁻), making this one of the most demanding service conditions

The hardness of these solid particles can reach HRC 72, which is comparable to that of hard alloys

All-Ceramic Trim Structure

The smooth, dead-zone-free flow path provides equal-percentage or quick-opening flow characteristics

The abrasion-resistant ceramic components retain their shape during long-term operation, helping the valves keep a tight seal; tested in accordance with GB/T 26480, they show no visible leakage

A specially designed ceramic ball trim is used to meet slurry atomization requirements, delivering superior cost reduction and improved operating efficiency

Quality Promise

Minimum service life

Control valves: more than 3 years
On-off valves: more than 7 years

The lower replacement frequency reduces downtime and associated losses, cuts operating costs, and improves plant safety

Conclusion

Ceramic slurry valves solve problems caused by corrosion, abrasion, erosion, and scouring. Successfully applied in flue gas desulphurization systems, they are the optimal choice for demanding FGD applications

Application References

Proven Performance in Power Plant FGD Systems

KOWOV ceramic valves have been used in power plant FGD systems for more than two decades

Selected References

Huaneng Luohuang Power Plant, supplied since 2003
Datong No. 2 Power Plant, supplied since 2003
Junliangcheng Power Plant, Tianjin, supplied since 2004
Guohua Ninghai Power Plant, supplied since 2006

Documented Service Life in Selected Applications

On-off valves: up to 8 years
Control valves: up to 5 years

In selected FGD projects, KOWOV ceramic valves have been used to replace imported ceramic valves and conventional metal control valves, helping customers reduce maintenance frequency and extend valve service life