Stainless Steel Coil Tube for Coke Oven Riser Heat Exchanger Systems

Product Overview

The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for integration into Coil-Type Riser Tube Heat Exchanger systems deployed in large-scale coke oven operations, including 6.25 m coke oven battery configurations. These coil tubes serve as critical heat transfer elements within the rising gas pathways of coke ovens, facilitating efficient thermal exchange between the rising coke oven gas (COG) and the working fluid circulating through the coil loops.

Unlike conventional straight-tube heat exchangers, coil tubes leverage their helical geometry to achieve superior heat transfer coefficients, reduced pressure drop, and compact footprint — making them indispensable in the demanding environment of modern coke oven plant design where space optimization and thermal efficiency are paramount.

Material & Properties

Base Material Grades

Coil tubes are fabricated from high-performance austenitic and austenitic-ferritic stainless steel grades, selected to withstand the aggressive chemical environment of coke oven gas, which contains hydrogen sulfide (H₂S), hydrogen cyanide (HCN), ammonia (NH₃), and trace hydrocarbons at elevated temperatures.

Mechanical Properties (Typical at Room Temperature)

Property 304L 316L 321 310S
Tensile Strength (MPa) ≥ 485 ≥ 485 ≥ 515 ≥ 515
Yield Strength (MPa) ≥ 170 ≥ 170 ≥ 205 ≥ 205
Elongation (%) ≥ 40 ≥ 40 ≥ 40 ≥ 35
Maximum Service Temperature (°C) 870 870 900 1150
Corrosion Resistance (H₂S environment) Good Excellent Good Fair

Specifications

Parameter Specification
Product Name Stainless Steel Coil Tube (盘管)
Product Code / Serial No. 256
Outer Diameter (OD) Φ 25 mm – Φ 159 mm (customizable)
Wall Thickness 1.0 mm – 6.0 mm
Coil Mean Diameter 300 mm – 2000 mm
Coil Pitch 25 mm – 100 mm
Coil Length (Uncoiled) 5 m – 120 m (per assembly)
Surface Finish Mirror Polish (Ra ≤ 0.4 μm) / Brushed / Pickled & Passivated
End Preparation Beveled / Flat Cut / Threaded (as specified)
Manufacturing Standard ASTM A213 / ASTM A269 / GB/T 12771 / EN 10216-5
Welding Standard ASME Section IX / AWS D10.6
Applicable Environment Coke Oven Riser Gas Heat Exchange (150–600 °C operating range)
Design Life ≥ 15 years (continuous operation)

Manufacturing Process

The production of high-quality stainless steel coil tubes involves a multi-stage process chain that ensures dimensional accuracy, metallurgical integrity, and corrosion resistance:

  1. Hot Rolling & Annealing: Raw stainless steel strip or seamless tube blanks undergo hot rolling followed by controlled furnace annealing (1050–1150 °C, water quench) to achieve a fully austenitic microstructure with fine grain size (ASTM grain size ≥ 6).
  2. Pickling & Passivation: The annealed product is subjected to hydrofluoric/nitric acid pickling to remove mill scale, followed by passivation treatment to establish a stable chromium oxide (Cr₂O₃) passive film on the surface.
  3. Cold Bending / Coil Forming: Using CNC-controlled coil forming machinery, the tube is bent into the specified helical geometry with precise control over coil diameter, pitch, and transition radii. Minimum bend radius is maintained at ≥ 3D (D = outer diameter) to prevent ovality exceeding 3% and to avoid work hardening-induced cracking.
  4. Interpass Inspection: After bending, each coil tube undergoes dimensional verification (laser scanning), visual inspection (VT), and magnetic particle testing (MT) to detect surface defects or deformation-related cracks.
  5. Welding (if applicable): U-tube or multi-pass coil assemblies are joined using Gas Tungsten Arc Welding (GTAW / TIG) with inert gas (argon) shielding to maintain weld zone metallurgical quality. Weld fillers match the base material grade.
  6. Solution Heat Treatment (Post-Weld Annealing): Welded assemblies are solution annealed at 1050–1100 °C followed by rapid cooling to dissolve any precipitated chromium carbides (Cr₂₃C₆) and restore full corrosion resistance.
  7. Final Surface Treatment: Mechanical polishing, electrolytic polishing, or passivation to achieve the required surface finish and chemical resistance.
  8. Final Quality Assurance: Comprehensive testing including ultrasonic testing (UT) for internal defects, dye penetrant testing (PT) for surface discontinuities, hydrostatic pressure testing, and chemical composition verification via Optical Emission Spectroscopy (OES).

Applications

Stainless steel coil tubes find critical application in the following industrial domains:

Technical Insight: In the context of 6.25 m coke ovens, the coil-type riser tube heat exchanger represents a significant advancement over traditional tubular designs. The helical configuration increases the heat transfer coefficient by 30–50% due to secondary flow (Dean vortices) generated within the curved tube geometry, while simultaneously reducing the pressure drop compared to equivalent-length straight tubes. This translates to improved thermal efficiency of the coke oven system and reduced energy consumption per tonne of coke produced.

Unique Selling Points

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains the following quality certifications and compliance standards:

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Serial No.: 256 | Classification: Literature Study / Technical Reference