Ceramic Valve Solutions for Sulfur Recovery Units
Reliable flow control for acid gas, liquid sulfur, ammonia-containing condensate and sulfur-deposition service in sulfur recovery units
Sulfur recovery units convert sulfur-bearing acid gas from coal chemical, refining and petrochemical processes into recoverable sulfur products while controlling harmful sulfur emissions
Coal Chemical Industry: Sulfur Recovery
A critical process for environmental compliance, converting acid gas into elemental sulfur and handling molten-sulfur solidification. Valves transport molten sulfur and treated tail gas while resisting sulfur corrosion, sulfur solidification and acid dew-point corrosion
Operating Conditions
The sulfur recovery unit recovers elemental sulfur from the acid-gas by-products generated in coal chemical gas-purification processes. It generally combines the Claus sulfur recovery process, including thermal and catalytic reaction stages, with a downstream tail-gas treatment unit
H₂S-rich acid gas from flash separation and syngas purification processes, such as Rectisol acid-gas removal, is partially combusted with air in the main reaction furnace. The H₂S/SO₂ ratio is carefully controlled, after which Claus catalytic conversion and multistage condensation produce molten sulfur
| Parameter | Value | Phase / Classification | Key Characteristic |
|---|---|---|---|
| Process media | Acid gas, process gas and molten sulfur | Predominantly liquid, with gas/non-condensable gas and trace solids locally present | Corrosion and mild erosion |
| Operating pressure | Up to 25 bar | Pressure class | ASME Class 300 |
| Differential pressure | ≤6 bar | Nominal size | DN25-DN400 |
| Operating temperature | Below 315°C | Thermal condition | No significant thermal shock during normal operation |
Process-Media Characteristics
In the Claus reaction furnace and catalytic reactors, operating temperatures are generally 200-315°C. The process media contain H₂S, SO₂ and elemental sulfur, together with small quantities of COS, CS₂, CO₂, NH₃ and water vapor. Low-temperature sections may also contain acidic condensate, ammonium salts and chlorides
Typical valve failure mechanisms include high-temperature sulfur corrosion and problems caused by the viscosity and solidification of molten sulfur. Molten sulfur is highly viscous at approximately 130-160°C and may solidify if its temperature falls, so valves and piping normally require insulation and heat tracing
Normal operation is relatively stable without severe thermal shock. However, start-up, shutdown, heat-tracing fluctuations, cooling, sulfur solidification and subsequent remelting may create thermal stress and sealing risks
| Medium Property | Typical Condition |
|---|---|
| Chemical composition | Condensate, sulfur condensate and acidic water |
| Corrosive components | Ammonium salts, chloride ions and sulfur compounds |
| pH | 5.5-9 |
| Solids content | Below 1% |
| Particle size | Below 100 μm |
| Particle hardness | Trace soft solids |
Summary of Ceramic Valve Applications in Coal Chemical Processes
Severe Abrasion and Particle-Erosion Service
For abrasive media such as slag water, coal slurry and pulverized coal, valves use one-piece or segmented ceramic-lined flow passages, with all critical internal components protected by engineering ceramics. The exceptional hardness and mechanical strength of ceramic trim resist particle impact and erosion, preventing sealing-surface wear and internal leakage
Throttling and High-Velocity Erosion Service
For black water and gray water control applications, ceramic V-port ball valves or specially designed ceramic control seats provide stable pressure reduction and precise flow regulation. Ceramic trim extends service life under high-velocity flow and helps prevent seat failure caused by cavitation and erosion
Acidic and Corrosive Service
For acidic media, acid gases and corrosive condensate, chemically stable ceramic materials can replace conventional alloy valves. This prevents premature failure and leakage caused by pitting and general corrosion while improving overall system corrosion resistance and operational safety
Frequent-Cycling Service
For lock-hopper sequence valves and other frequently operated valves, ceramic hard-seated construction provides excellent cycling-fatigue resistance. The valves maintain reliable shut-off and sealing integrity during long-term operation, substantially reducing maintenance frequency
Overall Value of Ceramic Valve Applications
These operating conditions represent the principal weaknesses of conventional metal valves in coal chemical plants and some of the most mature applications for ceramic valve technology
With exceptional hardness, corrosion resistance and chemical stability, ceramic valves effectively address abrasion, erosion, corrosion, jamming and sealing failures. They significantly extend service life and provide a reliable solution for critical coal chemical equipment requiring continuous long-term operation
Analysis of Actual Process Pain Points
Existing Valve Materials and Designs
Conventional valves generally use stainless steel or alloy-metal construction, including metal hard-seated ball valves and eccentric rotary valves. These designs cannot withstand continuous corrosion and erosion caused by highly corrosive media containing abrasive solids
Common Problems with Existing Valves
High-velocity hard particles cause severe erosion and may penetrate internal components. Damage to sealing surfaces results in internal leakage, while aggressive corrosion may damage the trim or valve body and cause external leakage. Particle accumulation in internal clearances may also cause the valve to stick or seize completely
Replacement Frequency and Service Life
Under combined erosion and corrosion, conventional metal hard-seated valves typically last only 6-12 months. At critical operating points, service life may be reduced to just 3-6 months, requiring frequent shutdowns for valve replacement
Losses Caused by Shutdowns and Maintenance
Unplanned shutdowns disrupt production and reduce plant output. Frequent valve replacement increases maintenance costs, while process-media leakage creates environmental compliance risks and potential penalties. High-pressure fluid discharge also poses serious hazards to personnel
Requirement for Long-Term, Reliable Operation
Coal chemical processes involve highly corrosive media, abrasive solid particles and frequent pressure and temperature fluctuations. As critical pipeline control components, valves must provide reliable long-term performance to prevent leakage and equipment failures, reduce unplanned shutdowns, maintain stable process parameters, lower spare-parts and maintenance costs, prevent uncontrolled discharge and material loss, and improve plant safety, environmental compliance and economic performance
Proven Applications of Ceramic Valves in Coal Chemical Plants
Gasification Unit
- Lock hopper depressurization valve
- Lock hopper pressurization valve
- Lock hopper depressurization-line flushing valve
- Lock hopper circulation-pump inlet valve
- Lock hopper circulation-pump recirculation valve
- Other severe-service valves
Coal Feeding and Conveying Unit
- Coal slurry and pulverized-coal conveying-line shut-off valves
- Pulverized-coal vent valves
- Other abrasive-media valves
Slag and Black Water Treatment Unit
- Flash drum level control valve
- Black water flow control valve at the quench-water pump outlet
- Scrubber level control valve
- Hot water tower level control valve
- Black water flow control valve at the slag-pool outlet
- Other slurry control valves
Gas Purification and Recovery Units
General-purpose process valves used in shift conversion, ammonia recovery and sulfur recovery units, including:
- Process-line isolation and throttling valves
- Condensate control valves
- Acid gas separator control valves
- Other severe-service control valves
Core Value and Advantages of Ceramic Valve Selection
Coal chemical processes involve severe abrasion, strong corrosion and high differential pressure. With a hardness of HRA 87 or above, engineering ceramic trim provides outstanding resistance to particle erosion and corrosive media. Its inorganic, non-metallic composition also delivers excellent chemical stability and durable sealing performance
Compared with conventional metal valves, ceramic valves can provide a service life 5-10 times longer, significantly reducing maintenance frequency and spare-parts costs. They are an effective upgrade for critical valve positions requiring reliable long-term operation in coal chemical plants
Why Choose Ceramic Valves?
Exceptional Abrasion and Erosion Resistance
Engineering ceramics have a hardness of HRA 87 or above, far exceeding conventional alloy steels. Ceramic valves withstand continuous high-velocity particle impact, abrasion and erosion, significantly extending service life and reducing replacement frequency
Outstanding Corrosion Resistance
Engineering ceramics are inorganic, non-metallic materials with excellent chemical stability. They resist chemical attack from aggressive process media, preventing the pitting, rusting and leakage commonly experienced with metal valves in corrosive service
Mirror-Finished Surfaces Resist Fouling and Jamming
Precision-machined ceramic flow-path surfaces have a mirror-like finish with extremely low particle adhesion. This minimizes solids buildup, scaling and crystallization, helping prevent valve sticking and seizure while reducing maintenance costs
Reliable Operation under Severe Conditions
Ceramic valves provide stable performance under high pressure, elevated temperatures and frequent cycling. Their long-term operating performance remains consistent, ensuring precise flow control and reliable shut-off for continuous plant operation
Conclusion
Ceramic valves are specifically designed to address abrasion, corrosion, fouling and jamming in coal chemical plants. By improving valve reliability at critical operating points, they support efficient long-term plant operation while significantly reducing unplanned shutdowns and maintenance costs
Case Study
Sulfur Recovery Units: site photographs
End Users
- Zhejiang Petroleum & Chemical Co., Ltd., China, commissioned in 2020
- Shandong Hualu-Hengsheng Chemical Co., Ltd., China, in service since 2012
Application Background
In the sulfur recovery and acid-condensate sections of Shandong Hualu-Hengsheng, the original metal-lined valves were exposed to sulfur compounds, acid gas, acidic water and mildly acidic or alkaline media. Corrosion of the sealing surfaces and internal components was severe, resulting in frequent maintenance and replacement. According to site feedback, the valves typically lasted only one to two months
After replacement with KOWOV ceramic valves, the chemically stable structural ceramic trim provided excellent resistance to both abrasive wear and corrosion. Under the same operating conditions, replacement intervals increased to approximately 3-5 years, significantly reducing shutdowns, maintenance and labor costs
The ceramic valve construction performs exceptionally well in acid gas, acidic water and mildly acidic or alkaline media. It helps prevent corrosion-induced leakage, sealing failure and abnormal instrument-control conditions, generating estimated annual savings of approximately RMB 2 million for the customer
Conclusion
Minimum recorded service life for ceramic on/off and control valves: ≥5 years
Commonly Used Products
FCCV1
Standard Ceramic Ball Valve
A proven and versatile ceramic ball valve with a classic design, suitable for both on/off and flow-control service. It can be used in most applications with operating temperatures up to 180°C and pressures up to 5.0 MPa, and is particularly effective for corrosive media containing abrasive solids
- Size range: DN15-250 (½″-10″)
- Shut-off class: Class IV or higher
FCRV
Ceramic C-Ball Valve
The valve features a special C-shaped structure. Its ball consists of a C-shaped metal support mechanically connected and securely fitted to a one-piece ceramic ball segment. The ceramic segment protects the metal support from direct erosion by the process medium
The concentric design keeps the ceramic ball segment in continuous contact with the seat during operation, allowing it to scrape deposits from the sealing surfaces and maintain reliable shut-off. It is particularly suitable for media prone to crystallization, scaling, agglomeration, high solids loading and valve jamming. Its cavity-free construction minimizes material accumulation inside the valve
- Size range: DN50-400
FCCV6
Single-Seat Ceramic Ball Valve
This cavity-free ceramic ball valve is designed for reliable control of highly viscous, crystallizing, scaling and agglomerating slurries and mineral slurries. Its unrestricted internal flow path supports smooth, stable, long-term plant operation
The scraping-action valve seat cleans deposited material from the ceramic ball during every opening and closing cycle, helping prevent buildup, sticking and valve seizure
- Size range: DN25-400
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