Stainless Steel Heat Extraction Coil Tube for Catalytic Regenerators

Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1487) supplies high-performance stainless steel coil tubes specifically engineered for heat extraction service in catalytic regenerator systems, particularly within Fluid Catalytic Cracking (FCC) and Fluidized Catalytic Cracking (FCC) units. These coil tubes serve as critical internal heat exchange elements that extract excess thermal energy from the catalyst bed, maintaining optimal regeneration temperature and protecting downstream process equipment from thermal overloading.

Product Overview

Heat extraction coil tubes (also referred to as internal heat exchanger tubes or regenerator coil bundles) are serpentine or U-shaped configurations of stainless steel tubing installed within the catalyst circulation zone of a catalytic regenerator. Their primary function is to absorb and transfer the intense heat generated during catalyst regeneration (burning off coke deposits) to a secondary coolant medium, thereby controlling the bed temperature and preventing thermal runaway conditions.

These coil tubes operate under extreme and often fluctuating thermal conditions, combined with severe mechanical erosion from circulating catalyst particles (typically 50–100 μm in size). Consequently, the selection of appropriate stainless steel grades, precise dimensional tolerances, and rigorous manufacturing quality control are paramount to ensuring long-term reliability and minimizing unplanned shutdowns caused by tube rupture or failure.

Operational Environment

Material & Properties

Wenzhou Jixing Metal Materials Co., Ltd. offers multiple stainless steel grades tailored to specific operating conditions within the catalytic regenerator. The following materials are commonly specified for heat extraction coil tube applications:

Recommended Material Grades

Grade UNS Designation Key Alloying Elements Maximum Service Temperature Primary Advantage
310S UNS S31008 Cr 24–26%, Ni 19–22% 1100 °C Exceptional high-temperature oxidation resistance; preferred for hottest zones of the regenerator
309S UNS S30908 Cr 22–24%, Ni 12–15% 925 °C Good oxidation resistance with improved weldability; suitable for moderate-temperature sections
316L UNS S31603 Cr 17–19%, Ni 10–14%, Mo 2–3% 870 °C Superior corrosion resistance in chloride and sulfuric acid environments; low carbon prevents sensitization
321 (with Ti stabilization) UNS S32101 Cr 17–19%, Ni 9–12%, Ti ≥5×C 870 °C Excellent resistance to intergranular corrosion; titanium stabilizes carbides during welding and high-temperature exposure
347 (with Nb stabilization) UNS S34701 Cr 17–19%, Ni 9–12%, Nb ≥10×C 870 °C Enhanced high-temperature strength and resistance to grain boundary corrosion; niobium stabilizer

Mechanical Properties (Typical for Grade 310S)

Property Specification Standard Reference
Tensile Strength (RT) ≥ 515 MPa ASTM A213 / ASME SA-213
Yield Strength (0.2% Offset, RT) ≥ 205 MPa ASTM A213 / ASME SA-213
Elongation (in 50 mm gauge length) ≥ 35% ASTM A213 / ASME SA-213
Density 8.0 g/cm³ —
Thermal Conductivity (1000 °C) ~ 25 W/(m·K) —
Thermal Expansion Coefficient (20–1000 °C) ~ 19.0 × 10⁻⁶ /°C —
Hardness (Annealed) ≤ 201 HB ASTM A213

Key Material Characteristics for Regenerator Service

Specifications

Parameter Typical Specification Applicable Standard
Outer Diameter (OD) Φ22 – Φ114 mm (custom sizes available) ASTM A213 / ASME SA-213
Wall Thickness 1.5 – 6.0 mm (minimum 2 mm recommended for erosion service) ASTM A213 / ASME SA-213
OD Tolerance ±0.05D or ±0.13 mm, whichever is less ASTM A213
Wall Thickness Tolerance ±10% of nominal ASTM A213
Length Single length up to 12,000 mm; coil bundles as per engineering design —
Bend Radius (Minimum) ≥ 3D (cold bend); ≥ 2D (hot form) EN 10217 / GB/T 14976
Surface Finish Inside: Ra ≤ 1.6 μm; Outside: Ra ≤ 3.2 μm (standard); Ra ≤ 0.8 μm (upon request) ASTM A213
End Condition Plain, beveled, or threaded per customer specification —
Heat Treatment Solution annealed and water/quench cooled ASTM A213
Delivery Condition Annealed (A) or Annealed and Pickled (AP) ASTM A213 / ASME SA-213
Coil Bundle Configuration Serpentine, U-tube, hairpin, or custom geometry per process engineering drawings —
Maximum Design Pressure Up to 6.0 MPa (design dependent) ASME Section VIII / GB 150

Manufacturing Process

The manufacturing of heat extraction coil tubes for catalytic regenerator service involves a multi-stage process with stringent quality controls at each phase to ensure the final product meets the demanding performance requirements of this application.

Process Flow

  1. Raw Material Procurement and Verification:
    • Stainless steel seamless tubes or cold-drawn tubes procured from certified mills (e.g., Outokumpu, Voestalpine, Sandvik, or domestic Grade A mills).
    • Incoming inspection includes chemical composition analysis (OES/SEM), mechanical property verification, and dimensional measurement.
    • Each heat lot is traceable with full mill test certificates (MTC) conforming to EN 10204 3.1 or 3.2.
  2. Dimensional Inspection and Cutting:
    • Raw tubes inspected for OD, wall thickness, straightness, and internal/external surface integrity.
    • Ultrasonic testing (UT) performed on 100% of tubes to detect internal defects (laminations, cracks, inclusions).
    • Tubes cut to required lengths using precision saws to ensure clean, square ends free of burrs or deformation.
  3. Surface Preparation:
    • Acid pickling and passivation treatment to remove mill scale, decarburization layers, and contaminants.
    • Internal cleaning via mechanical brushing or chemical passivation to achieve specified surface roughness (Ra).
    • External surface inspection via magnetic particle testing (MT) or dye penetrant testing (PT) for surface cracks.
  4. Forming and Bending:
    • Cold bending performed using CNC-controlled mandrel bending machines for precise geometry and dimensional accuracy.
    • Minimum bend radius maintained at ≥3D to prevent wall thinning, wrinkling, or cracking.
    • Post-bend inspection for dimensional accuracy, surface damage, and wall thickness reduction (maximum allowable thinning: 15%).
    • For large-diameter or complex geometries, hot forming may be employed with controlled heating and cooling cycles.
  5. Welding and Assembly:
    • Coil tube bundles assembled per engineering drawings, with joints welded using Shielded Metal Arc Welding (SMAW), Gas Tungsten Arc Welding (GTAW), or Submerged Arc Welding (SAW) depending on configuration.
    • Welding performed by certified welders (ASME IX / ISO 9606 qualified) using matching filler metals (e.g., ER310 for 310S base metal).
    • Pre-weld cleaning, interpass temperature control, and post-weld inspection (visual, PT, and radiographic testing as applicable) ensure weld integrity.
  6. Post-Weld Heat Treatment (PWHT):
    • Solution annealing at 1050–1150 °C followed by rapid water quench to restore full austenitic structure and eliminate residual stresses.
    • Pickling and passivation after PWHT to re-establish protective chromium oxide film.
  7. Final Quality Assurance:
    • 100% hydrostatic pressure testing at 1.5× design pressure (or as specified by ASME Section VIII / GB 150).
    • Final dimensional inspection and visual examination of all weld joints and bends.
    • Complete documentation package including MTC, weld records, NDT reports, and pressure test certificates.

Applications

Primary Application: Catalytic Regenerator Heat Extraction

The primary application for these stainless steel coil tubes is as internal heat exchanger elements within the catalyst regenerator of FCC (Fluid Catalytic Cracking) units in petroleum refineries. In this service, the coil tubes are immersed in the fluidized catalyst bed where coke burned off the spent catalyst generates temperatures of 700–850 °C. The coil tubes absorb this heat and transfer it to a coolant (typically water generating steam, or a dedicated heat transfer fluid), thereby:

Additional Applications