Enamel Tubular Air Preheater - Cost-Effective Anti-Corrosion Solution for Coal & Biomass Boilers

Enamel tubular air preheater is an upgraded tubular heat recovery device specially developed for coal-fired, biomass-fired and waste incineration boilers with high-sulfur, high-dust flue gas. Its core heat exchange component is low-carbon steel tubes coated with dense acid-resistant enamel via high-temperature sintering craft. It recovers waste heat from boiler tail flue gas to preheat combustion air, balancing low upfront investment and outstanding anti-dew-point corrosion performance, making it the most cost-competitive air preheater for medium & small industrial coal/biomass boiler projects.

Main Structure

- Core heat transfer bundle: Inside/outside double-sided enamel coated steel tubes

- Tube sheets, air hoods, shell frame, expansion joints and soot blowing ports

- Two mainstream layouts: Vertical tube bundle (flue gas inside tubes, air cross outside) / Horizontal tube bundle (easy maintenance for large boilers)

Heat Exchange Flow

1. Hot flue gas (150–380℃) flows through inner enamel tube channels, transferring heat outward

2. Cold ambient air sweeps across the outer enamel tube surface in cross flow and gets preheated

3. Preheated air feeds boiler burners to boost combustion efficiency; cooled flue gas flows to dust removal system

4. Smooth enamel surface avoids ash adhesion, sustaining stable heat transfer efficiency long-term

Core Competitive Advantages (Cost-Efficiency Focus)

① Superior Anti-Acid Dew Point Corrosion (Biggest Pain Point Solved)

Coal and biomass combustion generate SO₂/SO₃; when flue gas temperature drops below acid dew point, sulfuric acid condensate corrodes ordinary carbon steel tubes severely. The compact vitreous enamel coating fully isolates acid liquid, resisting sulfuric acid, nitric acid and ash erosion. Service life is 3–5 times longer than bare carbon steel tubular APH, cutting frequent tube replacement and boiler shutdown losses.

② Low Long-Term Operation & Maintenance Cost

- Ultra-smooth enamel finish has nearly no ash adhesion, less soot blowing frequency, reduces blower power consumption

- Hard enamel coating resists fly ash abrasion, no frequent tube patching

- Modular tube bundle design; damaged single tubes can be replaced separately without whole unit disassembly, low maintenance labor cost

③ Lower Total Cost vs Heat Pipe / Stainless Plate APH

- Initial procurement cost far lower than heat pipe air preheater and all-stainless welded plate APH

- No complex alloy material or vacuum sealing process; mature mass production shortens delivery cycle

- Investment payback period only 8–16 months via fuel savings and maintenance reduction

④ Stable Energy Saving Performance

Preheat combustion air by 100–260℃, improve boiler thermal efficiency by 7–14%, cut coal/biomass fuel consumption by 9–17%. Enamel coating barely weakens heat transfer coefficient (less than 5% drop vs bare steel tubes).

⑤ High Structural Reliability

High-temperature fusion enamel layer tightly bonds steel substrate, resistant to thermal cycling shock (0–400℃ frequent temperature fluctuation); each tube passes 100% spark leakage test to eliminate coating pinhole defects.

Application Scenarios

Perfect match for boilers with corrosive, dusty flue gas:

1. All types of coal-fired industrial boilers (1–35t/h steam/hot water boiler)

2. Biomass pellet, straw, wood chip fired boilers (high alkali & sulfur flue gas)

3. Waste incineration boilers, CFB circulating fluidized bed boilers

4. Small thermal power plants, heating station coal boilers