Stainless Steel Coil Tube for Ammonia Synthesis Converter Furnace Convection Section Heat Exchanger
Product Overview
The Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered stainless steel coil tube product specifically designed for the convection section heat exchange of first-stage ammonia synthesis converter furnaces (NH₃ synthesis first-stage reforming furnace convection section). This product serves as a critical heat transfer component within the syngas (synthesis gas) production process, where it facilitates efficient thermal energy recovery between the high-temperature process gas and the feed water/steam circuit.
Based on extensive research into over-temperature phenomena (超温研究) observed in convection section coil tubes during ammonia synthesis operations, this product has been engineered with enhanced thermal stability, superior oxidation resistance, and optimized geometric parameters to mitigate the risk of thermal degradation, tube wall thinning, and catastrophic failure under extreme operating conditions.
The coil tube is classified under the Document Study (文献学习) category, indicating its design and performance specifications are informed by rigorous academic and industrial research literature pertaining to high-temperature heat exchange applications in petrochemical and ammonia synthesis industries.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional performance at elevated temperatures typical of ammonia synthesis converter furnace convection sections.
Primary Material Grades
- 310S Stainless Steel (UNS S31008) — Chromium-Nickel austenitic grade with high chromium (24-26%) and nickel (19-22%) content, offering outstanding oxidation resistance up to 1150°C (2094°F). Preferred for zones experiencing the most severe thermal loads in the convection section.
- 309S Stainless Steel (UNS S30908) — Lower carbon variant of 309, providing excellent weldability and resistance to thermal cycling stresses, suitable for transition zones within the heat exchange coil assembly.
- 321 Stainless Steel (UNS S32100) — Titanium-stabilized austenitic grade offering superior resistance to intergranular corrosion (IGC) and thermal fatigue, applicable in moderate-temperature sections of the coil bundle.
Mechanical and Thermal Properties (Typical Values for 310S Grade)
| Property | Specification | Unit |
|---|---|---|
| Tensile Strength (at 20°C / 68°F) | ≥ 515 | MPa (psi) |
| Yield Strength (0.2% Offset, at 20°C / 68°F) | ≥ 205 | MPa |
| Yield Strength (at 800°C / 1472°F) | ≥ 110 | MPa |
| Elongation (at 20°C / 68°F) | ≥ 35 | % |
| Thermal Conductivity (at 100°C / 212°F) | ~ 14.6 | W/(m·K) |
| Coefficient of Thermal Expansion (20–800°C) | ~ 17.0 | × 10⁻⁶ / K |
| Maximum Continuous Service Temperature | 1150 | °C (2094°F) |
| Specific Heat (at 100°C / 212°F) | ~ 0.50 | J/(g·K) |
| Density | ~ 8.0 | g/cm³ |
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Category | Coil Tube (盘管) — Convection Section Heat Exchange Type | — |
| Tube Outer Diameter (OD) | 19.05 mm – 57.15 mm (¾" – 2¼") | ASTM A213 / ASME SA-213 |
| Tube Wall Thickness | 1.5 mm – 5.0 mm | — |
| Coil Mean Diameter (CMD) | 150 mm – 1200 mm (configurable per furnace design) | — |
| Coil Length (Developed) | 5 m – 60 m per coil bundle | — |
| Manufacturing Process | Hot-rolled (HR) or Cold-rolled (CR) seamless tube, cold-bent to coil geometry | ASTM A213, EN 10216-5 |
| Surface Finish | Mill finish (No. 1) or pickled and passivated (2B equivalent) | — |
| Heat Treatment | Solution annealing at 1050–1150°C followed by water quench | ASTM A213 |
| Design Operating Temperature | Up to 1050°C (1922°F) — convection section gas-side | — |
| Design Operating Pressure (Tube-side) | Up to 4.0 MPa (580 psig) — water/steam circuit | ASME BPV Code Section I |
| Design Operating Pressure (Gas-side) | Up to 0.5 MPa (72.5 psig) — syngas flow | — |
| Welding Method | Gas Tungsten Arc Welding (GTAW / TIG) with matching filler wire | ASME BPV Code Section IX |
| Dimensional Tolerance (OD) | ± 0.10 mm (for OD ≤ 25 mm); ± 0.15 mm (for OD > 25 mm) | ASTM A213 |
| Dimensional Tolerance (Wall) | ± 10% of nominal thickness | ASTM A213 |
| Bend Radius (Minimum) | 3 × OD (cold bending) | — |
| Product Serial No. | 251 | — |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. | — |
Manufacturing Process
The production of the coil tube for ammonia synthesis converter furnace convection sections follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Raw Material Procurement and Incoming Inspection: Stainless steel billets or slabs conforming to ASTM A213 / ASME SA-213 specifications are sourced from certified mills. Incoming materials undergo spectroscopic analysis (OES) to verify chemical composition, along with mechanical testing (tensile, hardness) and ultrasonic flaw detection (UT) to confirm material soundness.
- Seamless Tube Production: Tubes are manufactured via either the Hot Rolling (HR) process (for larger ODs and wall thicknesses) or the Cold Drawing (CD) process (for precision dimensions and superior surface finish). The seamless manufacturing method ensures no weld seam is present, eliminating potential failure points under high-temperature cyclic loading.
- Solution Annealing and Pickling: Tubes undergo solution annealing at temperatures between 1050°C and 1150°C, followed by rapid water quenching to achieve a fully austenitic microstructure. Subsequent pickling removes the oxide scale formed during annealing, and passivation establishes a protective chromium oxide passive film on the tube surface.
- Cold Bending and Coiling: Straight seamless tubes are cold-bent to the specified coil geometry using CNC-controlled rotary draw bending (RDB) machinery. The bending process is carefully controlled to prevent excessive wall thinning, ovalization, and residual stress accumulation. The minimum bend radius is maintained at 3 × OD to ensure structural integrity.
- Welding and Fabrication: Coil tube assemblies are joined using Gas Tungsten Arc Welding (GTAW/TIG) with matching composition filler wire (e.g., ER310 for 310S tubes). Welding procedures are qualified in accordance with ASME BPV Code Section IX. Post-weld inspection includes visual examination (VT), dye penetrant testing (PT), and radiographic testing (RT) where required.
- Post-Fabrication Heat Treatment: Where welding introduces localized microstructural changes, post-weld heat treatment (PWHT) or localized annealing may be applied to restore metallurgical homogeneity and relieve residual stresses.
- Final Inspection and Quality Assurance: Completed coil tube assemblies undergo comprehensive dimensional verification, hydrostatic pressure testing (at 1.5 × design pressure), non-destructive testing (NDT), and surface quality assessment before shipment.
Applications
The coil tube is specifically engineered for the following industrial applications:
- Ammonia Synthesis First-Stage Converter Furnace Convection Section (合成氨一段转化炉对流段): The primary application involves heat exchange within the convection section of the ammonia synthesis gas reforming furnace. The coil tube transfers thermal energy from the high-temperature syngas (containing H₂, N₂, CO, CO₂, H₂O) flowing through the furnace to the tube-side water/steam circuit, generating high-pressure steam (typically 3.5–4.0 MPa, 480–520°C) for power generation and process use.
- Over-Temperature Mitigation: Informed by research on over-temperature (超温) phenomena in convection section coil tubes, the product is optimized to handle localized hot spots and thermal runaway conditions that can occur due to uneven gas distribution, fouling, or operational transients. The enhanced material selection and geometric design provide a safety margin against tube wall temperature excursions.
- Steam Reforming Furnace Heat Recovery: The coil tube is also applicable in steam methane reforming (SMR) furnace waste heat recovery systems, where it captures thermal energy from flue gases to preheat process water.
- Petrochemical and Chemical Process Heat Exchangers: Beyond ammonia synthesis, the coil tube design is adaptable for other high-temperature process heat exchange applications in the petrochemical, methanol synthesis, and hydrogen production industries.
- Power Plant Auxiliary Systems: The coil tube can be deployed in boiler auxiliary heating systems, air preheaters, and economizers in combined cycle power plants.
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that all coil tube products meet international standards and industry requirements:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control throughout manufacturing.
- ISO 14001 — Environmental Management System certification for environmentally responsible production practices.
- ASTM A213 / ASME SA-213 — Standard specification for austenitic stainless steel seamless tubes for high-temperature service.
- EN 10216-5 — European standard for welded and seamless steel tubes for heat exchangers and similar purposes — Part 5: Non-ferrous tubes.
- ASME BPV Code Section I — Compliance with American Society of Mechanical Engineers Boiler and Pressure Vessel Code for pressure-containing components.
- ASME BPV Code Section IX — Welding procedure and welder qualification compliance.
- GB/T 14976 — Chinese national standard for cold-rolled seamless stainless steel tubes.
- GB/T 14975 — Chinese national standard for hot-rolled seamless stainless steel tubes.
- Pressure Vessel Inspection (PVI) / NDT Certification — Non-destructive testing performed by certified Level II/III inspectors per ASTM E1417 (dye penetrant), ASTM E94 (radiographic), and ASTM E747 (ultrasonic) standards.
- Material Test Reports (MTR) / EN 10204 3.1 Certificate — Each batch of coil tubes is accompanied by a full material test report certifying chemical composition, mechanical properties, and heat treatment records.
Unique Selling Points
Research-Informed Design: Unlike standard coil tube products, this offering is specifically engineered based on documented research into over-temperature failure modes (超温研究) in ammonia synthesis converter furnace convection sections. This empirical foundation translates into a product with demonstrably enhanced thermal margins and reliability under extreme operating conditions.
- Enhanced Thermal Stability: The selection of 310S/309S grade stainless steel provides exceptional resistance to high-temperature oxidation and scaling,