Ceramic Valve Solutions for Cold Hydrogenation
Reliable valve solutions for abrasive silicon powder, corrosive chlorosilanes and high-pressure service in polysilicon cold hydrogenation systems
Wear-resistant and corrosion-resistant ceramic valve solutions for silicon powder, silicon tetrachloride, hydrogen and chlorosilanes in polysilicon cold hydrogenation systems
Efficiently convert silicon tetrachloride (SiCl₄), a by-product of trichlorosilane synthesis, back into trichlorosilane (SiHCl₃), enabling material recycling and reuse
Key Industries
- Organic Silicon
- Polysilicon
Operating Conditions
Operating temperature below 250°C. Media include silicon powder, hydrogen, trichlorosilane, silicon tetrachloride, chlorosilanes, and other process materials
| Parameter | Value | Parameter | Value |
|---|---|---|---|
| Medium | Silicon powder, hydrogen, chlorosilanes, hydrogen chloride, etc. | Phase | Gas-solid two-phase |
| Operating pressure | 6-30 bar | Pressure class | Class 150-300 |
| Differential pressure (ΔP) | ≤5 MPa | Nominal size | DN25-DN200 |
| Operating temperature | <250°C | Thermal shock | None |
Media details: Silicon tetrachloride, silicon powder, and metal chlorides
| Property | Specification |
|---|---|
| Chemical composition | Hydrogen chloride |
| Corrosive component | Hydrogen chloride |
| Corrosiveness (pH) | Not specified |
| Solids content | Relatively high |
| Particle size | 150-600 μm |
| Particle hardness | Mohs 6-7 (Highly Abrasive) |
Special Operating Conditions
Abrasion and Corrosion
- The medium contains a large amount of fine silicon powder, resulting primarily in severe abrasive wear
- When chlorosilanes contact water or moisture, they undergo a strongly exothermic hydrolysis reaction, producing hydrogen chloride (HCl) and polysiloxanes, which cause severe corrosion of carbon steel
- High-boiling metal chlorides such as AlCl₃, FeCl₃, and TiCl₄ may precipitate and solidify at lower temperatures, causing crystallization, deposits, and increased erosion
- Hydrogen is an extremely small gas molecule that can readily permeate seals, making reliable sealing particularly challenging
Keywords: High Hardness · Powder Media
Process Pain Points and Key Opportunities
Existing Valve Materials and Types
Metal-seated valves are commonly used, mainly disc valves and ball valves
Problems with Existing Valves
- High-hardness particles cause severe abrasion. Valve sticking can scratch the sealing surfaces, resulting in internal leakage; erosion may also perforate the valve body, causing external leakage
- Corrosion is primarily caused by chlorosilanes
Replacement Interval and Service Life
The replacement interval varies from 3 to 6 months
Losses Caused by Shutdowns and Maintenance
- Production interruptions reduce overall production efficiency
- Leakage of flammable and explosive gases may cause serious production accidents
Other Relevant Information
Hydrogen is highly diffusive. Leakage may cause atmospheric pollution and adversely affect the quality of downstream reactions
Keywords: High Cost · Short Service Life · Frequent Maintenance · Production Accidents · Product Quality Instability
Why Choose Ceramic Valves?
Superior Wear Resistance
- Structural ceramics have a hardness of up to HRA 90, far higher than that of the conveyed medium, silicon powder, approximately HRA 70, and therefore resist abrasive wear
- Their inorganic, non-metallic properties and covalently bonded grain structure prevent the sealing surfaces from bonding to metal through micro-welding, avoiding adhesive and surface-fatigue wear
Superior Corrosion Resistance
- Structural ceramics provide outstanding inherent corrosion resistance, effectively withstanding the complex corrosive effects of chlorosilanes, hydrogen chloride, and the resulting corrosion-erosion damage
- In acidic media containing chloride ions, metals are highly susceptible to electrochemical corrosion. Even premium corrosion-resistant alloys can only slow the corrosion process, whereas structural ceramics do not undergo electrochemical corrosion
Fully Ceramic-Lined Ball Valve Construction
- The fully ceramic-lined ball valve ensures that the process medium contacts only the ceramic flow passage and never the metal pressure-containing body. Its near equal-percentage flow characteristic, inherent throttling performance, and scraping action prevent wear and material buildup
- The solid ceramic valve trim maintains stable performance over extended service, while the ceramic pressure-containing components retain their strength
Quality Commitment
Minimum service life: Control valves ≥3 years; on/off valves ≥5 years
Lower replacement frequency means fewer plant shutdowns and reduced production losses, resulting in lower total production costs and safer, more reliable operation
Conclusion
Specialized ceramic materials successfully solve the problems of abrasive wear and high-velocity particle erosion. These valves have been successfully applied at critical points in synthesis and cold-hydrogenation systems operated by many of the world’s top-ten polysilicon producers
Case Study
Cold Hydrogenation: site photographs
End Users
- Xinjiang Daqo New Energy Co., Ltd., China, since 2016
- Xinte Energy Co., Ltd., China, since 2014
- Sichuan Yongxiang Polysilicon Co., Ltd., China, since 2018
- Jiangsu Zhongneng Polysilicon Technology Development Co., Ltd., China, since 2012
- Inner Mongolia Tongwei High-Purity Crystalline Silicon Co., Ltd., China, since 2018
In polysilicon cold-hydrogenation applications, the feedstock is primarily silicon powder, which is highly abrasive. When domestic companies first introduced polysilicon production, valve designs were mainly based on imported brands, resulting in extremely high overall costs. During localization trials, conventional domestic metal hard-seated valves were compared with our ceramic valves. The ceramic valves demonstrated a significantly longer service life than the metal hard-seated valves while costing approximately 50% less than imported alternatives. Over their service life, each ceramic valve reduces costs by more than 25% compared with a domestic metal hard-seated valve over the same operating period. Additional savings from reduced shutdown maintenance and labor have not yet been included
Conclusion
Actual Service Life: Control valves: 3 years; on/off valves: ≥5 years
Commonly Used Products
FCCV1
Standard Ceramic Ball Valve
The FCCV1 series is the standard model in the ceramic ball-valve range. It is designed for highly corrosive and severely abrasive service at temperatures up to 180°C and differential pressures up to 2.0 MPa
- Wide sealing surfaces and scraper-type valve seats provide reliable shutoff and extended service life
- The ball and valve-seat sealing surfaces are match-lapped to ensure tight sealing
- The stuffing box incorporates live loading that maintains a constant packing load even after substantial wear, extending packing service life
- The symmetrical valve design provides bidirectional sealing with no flow-direction restrictions
- Wide ceramic flange-sealing surfaces protect the metal flanges from erosion and corrosion by the process medium
ELCV
Economical Ceramic Ball Valve
The ELCV uses essentially the same basic structural design as the FCCV1 but does not include a top mounting platform. Materials can be selected flexibly according to the operating conditions, providing a more economical ceramic-valve solution, although overall reliability is slightly lower than that of the FCCV1
| Parameter | Specification |
|---|---|
| Valve design | Floating-ball construction |
| Flange standards | ASME B16.5 / HG / DIN / JIS |
| Pressure rating | PN10-PN50 / ASME Class 150-300 |
| Operating temperature | −40°C to 180°C |
FCRV
Ceramic C-Ball Valve
The valve features a special C-shaped design. Its ball consists of a C-shaped metal support and a one-piece ceramic ball segment mechanically connected and securely embedded together. 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 away deposits adhering to the sealing surfaces and maintain reliable shut-off performance. It is particularly suitable for media prone to crystallization, scaling, agglomeration, high solids loading and valve jamming. Its cavity-free design minimizes material accumulation inside the valve
Size range: DN50-400
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