2205 duplex stainless steel is the go-to material for desulfurization tower spray pipes in power plants, chemical factories, and waste incineration plants. It combines excellent corrosion resistance (against sulfuric acid, chloride ions) and high strength—critical for harsh desulfurization environments. Spray pipes are core components: they distribute desulfurizing agents evenly, and their performance depends on two key factors: pipe support design and spray hole (Φ2-5mm) machining accuracy. Poor support leads to pipe deformation; inaccurate holes cause uneven spraying, reducing desulfurization efficiency. This article breaks down these two key points with simple language, real industrial cases, and actionable tips—no fancy technical jargon.
Why 2205 Duplex Steel for Spray Pipes?
Before diving into design and accuracy, let’s explain why 2205 is the top choice:
Corrosion resistance: It handles the acidic mist (pH 2-4) in desulfurization towers—regular stainless steel (304) rusts quickly here.
Strength: It’s 2x stronger than 304, so thinner pipes can be used (saves cost) without sacrificing durability.
Wear resistance: Resists erosion from high-velocity desulfurizing agent sprays, extending pipe service life to 5-8 years.
Pipe Support Design: Key to Stability
Spray pipes hang inside desulfurization towers, carrying high-pressure liquid (1.2-2.0MPa). Poor support causes sagging, bending, or even cracking. Here’s what works in real plants:
1. Support Type Selection
Two common support types—choose based on pipe length:
Hanger supports: For long pipes (6-10m). Use adjustable stainless steel hangers (matching 2205 material) spaced 2-3m apart. They prevent sagging and allow slight expansion (from temperature changes).
Bracket supports: For short pipes (2-5m). Weld stainless steel brackets to the tower wall—ensure welds are smooth (no sharp edges) to avoid stress concentration.
2. Key Design Tips
Allow thermal expansion: 2205 expands slightly (11.2×10⁻⁶/℃) when heated. Add sliding supports (1 per 5m pipe) to let pipes move freely—no fixed supports at both ends (causes cracking).
Avoid stress points: Don’t weld supports directly on spray holes or pipe bends. Weld 100mm away from holes to prevent hole deformation.
Corrosion protection: Coat support welds with anti-corrosion paint (matching 2205) to prevent rust—welds are vulnerable to acidic mist.
Spray Hole (Φ2-5mm) Machining Accuracy: Critical for Uniform Spraying
Spray holes (Φ2-5mm) are tiny but vital. They control the size and distribution of desulfurizing agent droplets. Even 0.1mm deviation ruins performance. Here’s how to get accuracy right:
1. Recommended Machining Methods
Two methods work for Φ2-5mm holes—avoid low-precision options (like drilling with hand tools):
CNC drilling: Most accurate (±0.05mm). Ideal for mass production. A CNC machine drills holes evenly, with consistent size and spacing.
Laser drilling: For complex hole patterns. Perfect for pipes with curved surfaces—laser drills clean, burr-free holes (no need for post-processing).
2. Accuracy Control Requirements
Size accuracy: Φ2-5mm holes must have a tolerance of ±0.05mm. A 0.1mm oversized hole (e.g., Φ3.1mm instead of Φ3mm) increases flow rate by 7%—causing uneven spraying.
Spacing accuracy: Holes should be spaced 50-100mm apart (based on tower size), with ±1mm spacing tolerance. Uneven spacing leads to “dead zones” (no spray coverage) in the tower.
Surface finish: Hole inner walls must be smooth (Ra ≤ 1.6μm). Rough walls cause droplet breakup, reducing desulfurization efficiency.
Real Industrial Cases
Case 1: Power plant spray pipe failure. A plant used 2205 spray pipes with hanger spacing 4m (too wide). After 6 months, pipes sagged 15mm, bending spray holes—desulfurization efficiency dropped from 95% to 88%. Fix: Add hangers (spacing 2.5m) and straighten pipes—efficiency recovered to 94%.
Case 2: Chemical plant hole accuracy issue. Holes were drilled with hand tools (tolerance ±0.2mm). Some holes were Φ2.2mm (oversized), some Φ1.8mm (undersized). Spraying was uneven, leading to acidic mist leakage. Fix: Re-drill holes with CNC machines—accuracy improved to ±0.05mm, no more leakage.
Case 3: Successful design. A waste incineration plant used hanger supports (2.3m spacing) and laser-drilled holes (Φ3mm, ±0.03mm). Pipes have run for 4 years without deformation; desulfurization efficiency stays at 96%.
Common Mistakes to Avoid
Mistake 1: Using wrong support material. Don’t use carbon steel supports—they rust and contaminate the desulfurizing agent. Always use 2205 or matching stainless steel.
Mistake 2: Drilling holes too close to pipe ends. Holes within 50mm of ends cause stress concentration—pipes crack easily here.
Mistake 3: Ignoring post-machining inspection. Skip checking hole size/spacing, and you’ll end up with uneven spraying. Inspect every 10 holes with a digital caliper (accuracy ±0.01mm).
Inspection Tips for On-Site Use
Check support stability monthly: Look for hanger looseness or bracket weld cracks—tighten or re-weld immediately.
Check hole accuracy quarterly: Use a digital caliper to measure 5-10 holes per pipe. If deviations exceed ±0.05mm, replace the pipe section.
Clean holes regularly: Desulfurizing agent residues clog holes (especially Φ2mm ones). Use high-pressure water (3MPa) to unclog—avoid sharp tools (they scratch hole walls).
Conclusion: For 2205 duplex stainless steel desulfurization tower spray pipes, success depends on two things: smart support design (adjustable hangers, thermal expansion allowance) and precise Φ2-5mm hole machining (CNC/laser, ±0.05mm tolerance). By following the tips and avoiding common mistakes, you’ll get even spraying, high desulfurization efficiency, and long pipe service life. This isn’t just theory—it’s what works in real power plants, chemical factories, and waste incineration plants every day.
