Stainless Steel Heating Coil Tube — Submerged Arc Furnace ESP Wall Panel Application
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Catalog No.: 351 | Classification: Technical Literature & Engineering Reference
1. Product Overview
The Stainless Steel Heating Coil Tube (also referred to as Coil Tube or Heating Coil) is a specialized process tube designed for installation within the wall panels of Electrostatic Precipitators (ESP) associated with Submerged Arc Furnaces (SAF) in metallurgical and mineral processing operations. The primary function of these heating coils is to maintain the wall panel temperature above the Dew Point Temperature of the flue gas stream, thereby preventing the condensation of acidic compounds — primarily Sulfuric Acid (H₂SO₄) and Hydrochloric Acid (HCl) — on the ESP casing surfaces.
Condensation of these corrosive species leads to severe Acid Corrosion, Pitting, and Crevice Corrosion of the ESP structural steel, resulting in premature failure, environmental compliance violations, and unplanned production downtime. The heating coil tube system serves as a critical Anti-Corrosion Thermal Management solution, ensuring long-term structural integrity and reliable dust collection performance.
This product specification is derived from the engineering study titled "Calculation and Analysis of Heating Coil Tubes for ESP Wall Panels in Submerged Arc Furnaces", which provides a rigorous thermodynamic and mechanical analysis framework for the design, sizing, and optimization of heating coil systems in this demanding industrial environment.
2. Material & Properties
2.1 Recommended Material Grades
| Property | Specification / Requirement |
|---|---|
| Material Grade | 310S (UNS S31008) / 309 (UNS S30908) / Inconel 600 (UNS N06600) — selected based on maximum operating temperature |
| Chromium (Cr) Content | 24–26 wt% (310S) / 22–24 wt% (309) |
| Nickel (Ni) Content | 19–22 wt% (310S) / 12–15 wt% (309) |
| Maximum Service Temperature | 1150 °C (310S) / 900 °C (309) / 1100 °C (Inconel 600) |
| Continuous Use Temperature | 900–1000 °C (310S) |
| Thermal Conductivity | 16.3 W/(m·K) at 100 °C (310S) |
| Thermal Expansion Coefficient | 18.0 × 10⁻⁶ /°C (310S) |
| Yield Strength (0.2% offset) | ≥ 205 MPa at 20 °C (310S) |
| Tensile Strength | ≥ 515 MPa at 20 °C (310S) |
| Oxidation Resistance | Excellent up to 1100 °C; forms stable Cr₂O₃ protective scale |
| Acid Resistance | High resistance to H₂SO₄, HCl, and mixed acid condensates at elevated temperatures |
| Weldability | Good; suitable for TIG (GTAW) and MIG (GMAW) welding with matching filler |
2.2 Material Selection Rationale
In Submerged Arc Furnace ESP environments, the heating coil tubes are exposed to:
- High-temperature flue gas with temperatures ranging from 200 °C to 400 °C
- Aggressive chemical atmosphere containing SO₂, SO₃, HCl, HF, and particulate matter
- Thermal cycling due to furnace start-up, shutdown, and load fluctuations
- Mechanical vibration from gas flow dynamics and ESP rapping mechanisms
Grade 310S is the preferred material for most SAF-ESP heating coil applications due to its exceptional High-Temperature Strength, Resistance to Oxidation, and Resistance to Thermal Fatigue. The addition of Columbium (Nb) and Titanium (Ti) stabilizers in 310S prevents Chromium Carbide Precipitation (sensitization) at weld heat-affected zones, maintaining uniform corrosion resistance throughout the component.
3. Specifications
3.1 Geometric & Dimensional Specifications
| Parameter | Typical Specification | Notes |
|---|---|---|
| Outer Diameter (OD) | Φ25 mm – Φ51 mm | Selected based on heat load requirement |
| Wall Thickness (WT) | 1.5 mm – 3.0 mm | Thicker walls for higher pressure applications |
| Coil Pitch (Spacing) | 100 mm – 250 mm | Determined by heat flux distribution analysis |
| Coil Diameter | 50 mm – 200 mm (U-bend radius) | Must accommodate thermal expansion |
| Tube Length (per coil) | 3.0 m – 12.0 m | Adapted to ESP wall panel geometry |
| Surface Finish | Mill finish / Sandblasted / Polished | Precision polished for enhanced heat transfer |
| End Preparation | Beveled / Plain / Threaded (as specified) | For flanged or welded connections |
3.2 Thermal & Hydraulic Performance
| Parameter | Specification | Test / Design Basis |
|---|---|---|
| Heat Medium | Steam (Saturated / Superheated) or Thermal Oil | Per furnace operating conditions |
| Steam Pressure (Max) | 0.5 – 1.6 MPa (gauge) | ASME / GB pressure vessel codes |
| Thermal Oil Temperature (Max) | 250 °C – 350 °C | Based on oil grade and system design |
| Wall Temperature Control | ≥ 10 °C above flue gas dew point | Prevents acid condensation |
| Heat Flux Density | 15 – 60 kW/m² | Calculated via thermal resistance model |
| Flow Velocity (inside tube) | 1.0 – 3.0 m/s (steam) / 0.5 – 2.0 m/s (oil) | Ensures uniform heat distribution |
3.3 Design & Code Compliance
| Standard / Code | Scope of Application |
|---|---|
| ASTM A312 / A318 | Wrought austenitic stainless steel seamless and welded tubes |
| ASME B31.3 | Process piping design and fabrication |
| GB/T 12771 | Chinese national standard for stainless steel tubes |
| EN 10216-5 | European standard for austenitic stainless steel tubes |
| ISO 15530 | Stainless steel tubes — dimensions and tolerances |
| ASME BPV Code Section I | Pressure boundary components (if applicable) |
4. Manufacturing Process
4.1 Process Flow
- Material Procurement & Inspection: Raw stainless steel tube stock (310S or specified grade) is procured from certified mills. Incoming material undergoes Spectroscopic Analysis (OES) for chemical composition verification, Hydrostatic Testing for wall integrity, and Visual Inspection for surface defects.
- Cutting & Dimensioning: Tubes are cut to specified lengths using Plasma Cutting or Waterjet Cutting to minimize Heat-Affected Zone (HAZ) damage. Cut ends are deburred and cleaned.
- Coil Forming / Bending: Tubes are formed into the required coil geometry using Cold Bending or Hot Bending processes. The bending radius is carefully controlled to avoid Wall Thinning and Wrinkling on the inner and outer surfaces of the bend, respectively. Minimum bend radius is typically 3–5 times the tube OD.
- Welding: U-bends, headers, and connection points are fabricated using Tungsten Inert Gas (TIG / GTAW) Welding with matching filler wire (e.g., ER310 for 310S tubes). Back Purging with Argon (Ar) gas is employed to prevent Internal Oxidation and Intergranular Corrosion susceptibility at the weld root.
- Heat Treatment (if required): Solution annealing at 1050–1100 °C followed by Water Quenching may be performed to restore full Austenitic Microstructure and maximize corrosion resistance, particularly for heavily cold-worked components.
- Surface Treatment: Pickling and PASSIVATION are applied to remove mill scale, welding discoloration, and surface contaminants. A stable Chromium Oxide (Cr₂O₃) Passive Film is established to provide maximum corrosion protection.
- Non-Destructive Testing (NDT): Weld joints are inspected using Penetrant Testing (PT) for surface defects and Radiographic Testing (RT) or Ultrasonic Testing (UT) for volumetric integrity. 100% inspection is standard for pressure-containing components.
- Pressure Testing: Completed coil assemblies undergo Hydrostatic Pressure Testing at 1.5× the maximum design pressure to verify leak-tightness and structural integrity.
- Dimensional Verification & Final Inspection: All geometric dimensions, coil spacing, and alignment are verified against engineering drawings. Material Test Reports (MTR) and Certificates of Compliance are compiled.
4.2 Key Process Controls
- Intergranular Corrosion Testing: Welded coupons are subjected to ASTM A262 Practice E (acid solution test) to confirm resistance to intergranular corrosion.
- Creep Testing: Long-term Creep Strength is verified per ASTM E139 for applications involving sustained high-temperature loading.
- Thermal Cycle Simulation: Prototype assemblies undergo thermal cycling tests (20 °C ↔ 400 °C, ≥100 cycles) to validate Fatigue Life under operational conditions.
5. Applications
5.1 Primary Application — Submerged Arc Furnace ESP Wall Panel Heating
The primary and most demanding application for this heating coil tube is the Wall Panel Temperature Control System of ESPs in Submerged Arc Furnaces used for:
- Electrothermal Smelting of ferromanganese (FeMn), silicomanganese (SiMn), and ferroalloys
- Mineral Processing — calcination of nickel laterite ores, cobalt ore processing
- Carbon Black Production — thermal cracking furnaces with associated dust collection
- Phosphorus Production — electric arc furnace off-gas treatment
5.2 Engineering Analysis Context
As detailed in the referenced study "Calculation and Analysis of Heating Coil Tubes for ESP Wall Panels in Submerged Arc Furnaces", the design of the heating coil system requires rigorous analysis of the following parameters:
- Flue Gas Dew Point Calculation: Determination of the Sulfuric Acid Dew Point using the Leppalupi Method or Al-Mukhtar & Saka Method, considering SO₃ concentration, water vapor partial pressure, and total gas pressure.
- Heat Load Calculation: Total heat duty (Q) required to maintain wall panel temperature above the dew point, calculated as:
Q = U × A × ΔTlm
where U = overall heat transfer coefficient, A = effective heat transfer area, and ΔTlm = log-mean temperature difference. - Coil Layout Optimization: Determination of optimal coil pitch, number of coils, and steam/oil flow rate distribution to achieve uniform wall panel temperature with minimum energy consumption.
- Thermal Stress Analysis: Finite Element Analysis (FEA) of the coil-to-wall-panel assembly to evaluate Thermal Stress Concentrations at weld joints and expansion joints.
- Pressure Drop Analysis