Low Temperature Industrial Air Preheater Corrosion Resistant Alloy Boiler Preheater

Low-Temperature Corrosion-Resistant Air Preheater with ND Steel and Alloy Tube Construction

The Low-Temperature Corrosion-Resistant Air Preheater is a specialized flue gas heat recovery component fabricated by Boyu Heavy Industry using our specialty material fabrication capabilities, designed for the cold end section of air preheaters where acid dew point corrosion is the primary failure mechanism. Unlike enamel-coated designs that rely on a protective coating, this air preheater uses corrosion-resistant alloy steel tubes (ND steel, Corten steel or equivalent) that inherently resist sulfuric acid condensation through chemical composition. This assembly serves the primary function of recovering heat from flue gas at temperatures below the acid dew point (typically 90-130C), enabling deeper heat recovery and higher boiler efficiency without premature tube failure. As environmental regulations push for lower stack temperatures and higher efficiency, the corrosion-resistant air preheater has become an essential solution.

The Low-Temperature Corrosion-Resistant Air Preheater is specifically constructed with tubes fabricated from corrosion-resistant alloy steels developed for sulfuric acid dew point service. ND steel (09CrCuSb) is a Chinese-developed alloy with copper, chromium and antimony additions that provide excellent resistance to sulfuric acid corrosion at temperatures 60-150C. Corten steel (ASTM A242) provides atmospheric and mild acid corrosion resistance through its patina-forming alloy composition. Boyu fabricates these specialty alloy tubes using certified material with full heat number traceability, with tube diameters typically 32-51mm and wall thickness 2.5-4mm. The tube sheets and housing are fabricated from carbon steel with appropriate corrosion allowance, or from matching alloy steel for maximum corrosion protection.

Manufactured using certified specialty alloy tubes with precision tube sheet drilling, tube expanding, seal welding and comprehensive leak testing, every Corrosion-Resistant Air Preheater undergoes material verification (PMI - positive material identification), dimensional inspection and 100% leak testing. Boyu's experience in specialty material fabrication ensures proper welding procedures for alloy steels, with WPS/PQR qualification and post-weld treatment where required. Typical delivery is 35-50 days for complete assemblies. Complete material certificates (including chemical composition and corrosion test reports), weld records and leak test reports accompany every shipment. The cross-flow tubular design follows the same configuration as standard APH, with flue gas inside alloy tubes and air flowing externally.

One significant advantage of the alloy steel Corrosion-Resistant Air Preheater compared with enamel-coated designs is the inherent corrosion resistance that does not depend on coating integrity. Enamel coatings can chip, crack or pinhole during fabrication, transport or installation, exposing the underlying carbon steel to rapid corrosion. Alloy steel tubes provide uniform corrosion resistance throughout the tube wall, with no risk of coating failure. Additionally, alloy tubes can withstand higher mechanical stress and thermal cycling without the coating degradation that affects enamel designs, making them preferable for high-dust, high-vibration or frequent load-cycling applications. The corrosion rate of ND steel in sulfuric acid environments is typically 1/3 to 1/5 of ordinary carbon steel.

The Low-Temperature Corrosion-Resistant Air Preheater is adaptable to various boiler types, fuel types and low-temperature operating conditions, making it suitable for power generation, coking, petrochemical, steelmaking, waste-to-energy and marine boiler industries. Its versatility enables application as the cold-end section of a multi-stage air preheater system, or as a standalone deep heat recovery unit for high-sulfur fuel boilers. Furthermore, the assembly can be customized for specific flue gas compositions, including different sulfur content levels, dust loads and temperature profiles, with alloy material selection optimized for each corrosion environment.

In addition to functional benefits, the Corrosion-Resistant Air Preheater is designed with long-term durability and maintenance convenience in mind. The alloy steel tubes provide consistent corrosion resistance over the full service life, with predictable thinning rates that enable accurate remaining life assessment. The modular tube bundle design allows for individual section replacement during scheduled maintenance. Boyu provides technical support for acid dew point calculation, alloy material selection, corrosion rate estimation and thermal design, helping clients optimize heat recovery depth while managing corrosion risk through proper material specification.

To summarize, the Boyu Low-Temperature Corrosion-Resistant Air Preheater represents a specialized solution for deep flue gas heat recovery in corrosive environments using inherently corrosion-resistant alloy steel tubes. By delivering ND steel or Corten steel tube bundles with verified material composition and leak-tested construction, it enables flue gas cooling below acid dew point, extends service life and maintains heat transfer efficiency without coating dependency. Our specialty material fabrication capability, systematic alloy selection and expert technical support make this product an ideal choice for boiler operators facing severe low-temperature corrosion. Investing in alloy steel corrosion-resistant air preheaters is a strategic decision that supports maximum energy recovery, long-term reliability and environmental compliance.

Features

·        Inherent corrosion resistance via ND steel (09CrCuSb) / Corten steel, no coating dependency

·        ND steel corrosion rate: 1/3 to 1/5 of ordinary carbon steel in sulfuric acid environments

·        Unlike enamel coating: no chipping, cracking or pinhole risk

·        Withstands high-dust, high-vibration and frequent load cycling better than coated designs

·        PMI (positive material identification) verification for every alloy tube batch

·        Certified specialty alloy with full heat number traceability

·        Tube OD 32-51mm, WT 2.5-4mm, cross-flow tubular design

·        Enables flue gas cooling below acid dew point (90-130C) for maximum heat recovery

·        Modular tube bundle for individual section replacement

·        Expert support for acid dew point calculation and alloy material selection

Technical Parameters

Applications

The Boyu Low-Temperature Corrosion-Resistant Air Preheater is a specialized heat recovery component fabricated using our specialty material capabilities. Manufactured in Shandong, China, this assembly uses inherently corrosion-resistant alloy steel tubes for the cold-end section of air preheaters. Certified with ISO9001, ASME, Grade A and SGS, the product guarantees high quality and reliable corrosion protection.

This Corrosion-Resistant Air Preheater is widely used in high-sulfur coal-fired boilers, heavy oil boilers, waste-to-energy boilers, coking waste heat boilers, marine boilers and metallurgical exhaust gas boilers where acid dew point corrosion limits heat recovery depth. Its alloy steel construction enables deeper flue gas cooling without coating dependency, extending service life in the most corrosive low-temperature environments.