How 95+™ Heater Technology Eliminates Sulfur Dew Point Corrosion

Introduction

Sulfur dew point corrosion is a major challenge that limits the efficiency and lifespan of traditional fired heaters and furnaces. This form of corrosion occurs when sulfur compounds condense on heat exchanger surfaces, causing material degradation and operational issues.

Sulzer’s patented 95+™ Heater Technology offers a patented solution that effectively eliminates sulfur dew point corrosion by a proprietary “deep purification step” to remove all types of sulfurs in the fuel gas, enabling fired heaters to operate at unprecedented thermal efficiencies of 95% or higher while extending equipment life.

Understanding Sulfur Dew Point Corrosion

In fired heaters, sulfur compounds in the flue gas can condense when the metal surface temperature falls below the sulfur dew point. This condensation leads to:

• Corrosion of heat exchanger surfaces, as well as flue gas duct and chimney

• Reduced heat transfer efficiency due to fouling and damage

• Increased maintenance costs and downtime

• Limitations on achievable thermal efficiency, typically capping at maximum 89–92%

  
  

Traditional approaches to mitigate this issue include using expensive corrosion-resistant materials or limiting heat recovery, both of which increase costs or reduce efficiency while the acid corrosion risk remains. The special material air preheater (APH) solution even posts additional problem of large quantity of acidic water that requires caustic neuralization followed by wastewater treatment.

The 95+™ Proprietary Solution

Sulzer’s 95+™ Heater Technology addresses sulfur dew point corrosion through an innovative, system-wide process solution that:

• Remove all sulfurs from the source: Proprietary “deep purification step” to remove all types of sulfurs in the fuel gas. Because fuel gas is only a fraction of the volume comparing to flue gas, treating fuel gas allows the system to be much smaller, lower cost, and more effective.

• Prevents sulfur condensation: Sulfur dew point in the flue gas is practically eliminated. There is no risk of acidic corrosion regardless of how much heat is recovered and how low the temperature flue gas achieves.

• Reduces fouling: The design minimizes deposits that contribute to heat transfer loss and operating issue.

• Enables higher heat recovery: Without the risk of corrosion, more heat can be extracted from flue gases, boosting thermal efficiency to ≥95%.

• Uses cost-effective materials: Eliminates the need for expensive alloys or polymer, or complex coatings, reducing CAPEX.

  
  

Benefits for Heater Longevity and Maintenance

By eliminating sulfur dew point corrosion, 95+™ Heater Technology delivers:

• Extended equipment lifespan: Reduced corrosion means less frequent repairs and replacements.

• Lower maintenance costs: Less fouling and damage translate into fewer shutdowns and cleaning cycles.

• Improved operational reliability: Stable heater performance with no unexpected failures.

• Enhanced safety: Reduced risk of corrosion-related leaks or failures.

  
  

Comparison with Special-material APH

While air preheaters (APH) with corrosion-resistant materials claims to push efficiency up to about 92%, they still face challenges with fouling and cost. The downside of the special-material APH is too great to be ignored:

• Special coating or polymer reduces the heater transfer efficiency, which is critical for heat exchanger

• Extended heat exchange area due to smaller heat transfer efficiency, in combination with high-cost material, makes a single equipment very expansive.

• Sulfur dew point still exist, which means when the flue gas temperature is reduced to below sulfur dew point (typically ~120℃), there is sulfuric acid condensation. It creates large quantity of acidic water that requires special storage, neutralization, and wastewater treatment, as well as additional environmental risk.

• It relies on perfect coating or special material surface. Any weak point of the surface will become a starting point of corrosion that can quickly spread out in the equipment.

• High corrosion risk for the downstream flue gas duct and chimney/stack in case any acidic droplet is carried over, or further acid condensation along the way.

• It still has limitation on how low the flue gas can achieve, at typically around 100℃, which still limits the thermal efficiency.

95+™ Technology surpasses these limits by fully eliminate the sulfur dew point, achieving:

• Higher thermal efficiency (≥95%)

• Lower capital and operational costs

  
  

Conclusion

Sulzer’s 95+™ Heater Technology offers a groundbreaking solution to sulfur dew point corrosion—a key barrier to fired heater efficiency and longevity.

By preventing corrosion and enabling higher heat recovery, it empowers operators to achieve superior performance, reduced costs, and longer equipment life.

Interested in protecting your fired heaters from sulfur dew point corrosion? Contact Sulzer Chemtech to learn how 95+™ Heater Technology can safeguard your assets and boost efficiency.