Ceramic Valve Solutions for CO Shift and Syngas Purification
Reliable flow control for wet H₂S/CO₂ corrosion, ammonium salt scaling, high-pressure condensate and low-temperature Rectisol service
CO shift conversion and syngas purification are critical downstream sections of a coal gasification plant. Valves in these systems handle shifted syngas, process water, ammonia-containing condensate, acid gas and low-temperature methanol under corrosive, high-pressure and flashing conditions
Coal Chemical Industry: Shift Conversion and Gas Purification
Shift Conversion: The syngas conditioning unit converts CO to adjust the hydrogen-to-carbon monoxide ratio and delivers the shifted gas to the downstream purification unit. Valves must reliably handle wet H₂S, steam and medium- to high-temperature operating conditions
Gas Purification: The syngas purification unit uses low-temperature methanol washing to remove acid gases and deliver purified syngas downstream. Valves must provide reliable sealing and resistance to low temperatures and corrosive acid-gas service
Operating Conditions
In the shift conversion section, carbon monoxide in the raw syngas reacts with steam over a catalyst to produce hydrogen and carbon dioxide. This adjusts the H₂/CO ratio to meet the hydrogen-to-carbon monoxide requirements of downstream methanol, synthetic ammonia, Fischer-Tropsch and other chemical synthesis processes
| Parameter | Value | Phase / Classification | Key Characteristic |
|---|---|---|---|
| Process media | Shifted syngas, process water and condensate | Gas, liquid and solids may coexist | Corrosion, erosion and abrasive wear |
| Operating pressure | Up to 100 bar | Pressure class | ASME Class 900 |
| Differential pressure | Up to 10 bar | Nominal size | DN25-DN200 |
| Operating temperature | Below 200°C | Thermal condition | No significant thermal shock during normal operation |
Process-Media Characteristics
Media in the shift conversion unit mainly include shifted syngas containing H₂S, CO, CO₂, NH₃ and COS, together with process water and condensate. Gas-liquid two-phase flow may occur
Major challenges include corrosion caused by H₂S and CO₂, ammonium-salt crystallization and blockage, and combined corrosion mechanisms. Trace quantities of catalyst dust carried over from upstream equipment create secondary abrasive wear but are generally not the primary cause of valve failure
Normal operation is relatively stable without significant thermal shock. However, start-up, shutdown and switching between process gas and steam may expose valves to thermal cycling. Valve trim must therefore provide corrosion resistance, erosion resistance, resistance to crystallization and stable sealing performance
| Medium Property | Typical Condition |
|---|---|
| Chemical composition | Shifted syngas, process water and condensate |
| Corrosive components | Sulfur compounds, acidic species and chloride ions |
| pH | 7-9 |
| Solids content | Approximately 1% |
| Particle size | 50-100 μm |
| Particle hardness | Mohs hardness 5 |
Operating Conditions
The syngas purification section removes acid gases, including H₂S, COS and CO₂, from shifted syngas to produce clean syngas that meets the requirements of downstream processing units
Coal chemical plants commonly use the Rectisol process, in which chilled methanol selectively absorbs H₂S, COS and CO₂ at temperatures of approximately −60°C to −40°C. The methanol-rich solution is subsequently flashed and regenerated for recirculation
| Parameter | Value | Phase / Classification | Key Characteristic |
|---|---|---|---|
| Process media | Acid gas and chilled methanol | Gas-liquid two-phase flow | Corrosion and erosion |
| Operating pressure | 30-80 bar | Pressure class | ASME Class 600/900 |
| Differential pressure | 3-10 bar | Nominal size | DN25-DN200 |
| Operating temperature | Below 180°C* | Thermal condition | No significant thermal shock during normal operation |
*Critical Rectisol valve positions may operate at temperatures as low as approximately −60°C
Process-Media Characteristics
The principal valve failure mechanisms in the purification section are acid-gas corrosion, loss of sealing performance at low temperatures, insufficient low-temperature material toughness and methanol-induced swelling of non-metallic sealing materials. Particle erosion is generally limited
Thermal cycling during plant start-up and shutdown may cause conventional sealing materials to lose resilience or sealing integrity. Valve trim must therefore provide low-temperature resistance, reliable sealing and resistance to H₂S/CO₂ corrosion and methanol-induced swelling
Rectisol valves remain exposed to low-temperature, high-pressure service containing acid gases and methanol for extended operating periods. Valves on the acid-gas side must also meet the corrosion-resistance requirements of the downstream sulfur recovery section
| Medium Property | Typical Condition |
|---|---|
| Chemical composition | Acid gas, chilled methanol and chloride ions |
| Corrosive components | Cold condensable organics and chloride ions |
| pH | 7-9 |
| Solids content | Trace |
| Particle size | Below 50 μm |
| Particle hardness | Mohs hardness 1 |
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 ceramic linings or segmented ceramic-lined flow passages, with all critical internal components protected by engineering ceramics. The exceptional hardness and mechanical strength of the ceramic trim resist particle impact and erosion, preventing sealing-surface wear and internal leakage, the most common failure modes of conventional metal valves
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. The ceramic trim extends service life under high-velocity flow and helps prevent valve-seat failure caused by cavitation and erosion
Acidic and Condensate Corrosion Service
For acidic water, acid gases and condensate, chemically stable ceramic materials can replace corrosion-resistant alloy valves. This fundamentally prevents pitting corrosion, general corrosion and leakage, 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 resistance to cycling fatigue. The valves maintain reliable shut-off and sealing integrity during long-term operation, substantially reducing maintenance frequency
Overall Value of Ceramic Valve Applications
The operating conditions described above represent the principal weaknesses of conventional metal valves in coal chemical plants. They are also among the most mature and widely adopted 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 valve service life and are a dependable choice for long-term, reliable operation of critical coal chemical equipment
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 the continuous corrosion and erosion caused by highly corrosive media containing large quantities of 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. Particles can also accumulate in internal clearances, causing 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 fall to just 3-6 months, requiring frequent shutdowns for valve replacement
Losses Caused by Shutdowns and Maintenance
Unplanned shutdowns disrupt production and reduce output. Frequent valve replacement increases maintenance and spare-parts costs. Process leakage may create environmental compliance risks and substantial penalties, while high-pressure fluid discharge 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 operation to prevent leakage and unexpected equipment failures, reduce unplanned shutdowns, maintain stable process parameters, lower maintenance and material-loss costs, prevent uncontrolled discharge, and improve the plant’s economic, safety and environmental 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 pump outlet
- Other slurry control valves
Gas Purification and Recovery Units
General process valves used in the shift conversion, ammonia recovery and sulfur recovery units, including:
- Process-line isolation valves
- 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 pressures. With a hardness of HRA 87 or above, engineering ceramic trim provides exceptional 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. This enables ceramic valves to 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 performance remains consistent, ensuring precise flow control and reliable shut-off for continuous plant operation
Conclusion
Ceramic valves are specifically engineered to overcome 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
CO Shift & Syngas Purification: site photographs
End Users
- Wanhua Chemical (Ningbo) Co., Ltd., China, commissioned in 2019
- Hengli Petrochemical (Dalian) Refining & Chemical Co., Ltd., China, in service since 2019
Application Background
In coal chemical shift conversion and gas purification units, process media include shifted syngas, process water, condensate, chilled methanol and acid gas. These media may contain moisture and corrosive gases and can cause scaling, crystallization, blockage, erosion and cavitation
KOWOV ceramic valve trim provides high hardness, excellent erosion resistance and outstanding chemical stability. It also performs reliably in low-temperature service involving acid gases and methanol
After conventional metal valves were replaced with KOWOV ceramic valves, service life increased to approximately 3-5 years or longer. The upgrade effectively reduced internal leakage, valve sticking, flow instability and control deviation while maintaining stable gas flow, liquid level and discharge parameters
The ceramic valve solution generated annual cost savings of approximately RMB 7 million for the end users
Conclusion
Minimum recorded service life for ceramic control and on/off 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 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 viscous, crystallizing, scaling and agglomerating slurries and mineral slurries. Its unrestricted internal flow path helps maintain smooth, stable, long-term plant operation
The scraping-action valve seat cleans material deposits 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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