Flue gas heat recovery is one of the most effective ways to improve energy efficiency in high-temperature industrial processes. In sectors such as biomass boilers, feed dryers, cement kilns, steel furnaces, and waste incineration plants, large amounts of thermal energy are discharged into the atmosphere in the form of hot exhaust gases.
Recovering this energy not only reduces fuel consumption and CO₂ emissions, but also significantly improves overall plant efficiency and operating economics.
However, flue gas heat recovery in real industrial environments is far from a simple heat exchanger application. High temperatures, dust, corrosion, and fouling make these projects technically challenging and highly demanding in terms of materials and design.
In high-temperature biomass or furnace applications, flue gas systems usually present the following difficulties:
Extremely high temperatures
Continuous operation at 700–850°C, with short-term peaks up to 900°C.
Severe dust loading
Particulate concentrations often exceed 5,000–6,000 mg/Nm³, causing intense erosion of heat transfer surfaces.
Chemical corrosion and slagging
Flue gas from biomass contains chlorides (KCl, CaCl₂) that cause aggressive high-temperature corrosion and sticky deposits.
Thermal cycling and fatigue
Frequent start-stop operations generate large thermal stresses.
These conditions mean that conventional stainless steel or standard shell-and-tube designs often fail within a few years.
A reliable flue gas heat recovery system must be designed based on the following principles:
Typical material selection includes:
Sanicro 25
Incoloy 800HT
253MA
310S stainless
These alloys offer excellent resistance to:
High-temperature oxidation
Chloride-induced corrosion
Long-term creep and fatigue
For heavy dust applications:
Inline tube arrangements are preferred
Staggered tube layouts should be avoided
Online mechanical or air-based cleaning systems are essential
The system must be capable of operating continuously without frequent manual cleaning.
Design must consider:
Differential thermal expansion between shell and tube bundle
Flexible supports and expansion compensation
Refractory lining for the casing in extreme temperature zones
In modern industrial projects, performance guarantees typically include:
Thermal duty (MW)
Maximum flue gas outlet temperature
Process medium outlet temperature
Pressure drop limitations
Long-term mechanical warranty (often 24–36 months)
For critical production systems, flue gas heat recovery equipment is no longer treated as a “utility accessory”, but as a core production asset.
In a recent industrial project, a flue gas heat exchanger was designed to recover heat from:
700°C biomass flue gas
Dust load exceeding 5,500 mg/Nm³
Continuous operation of 7,200 hours per year
The system increased overall energy efficiency by more than 30% while ensuring long-term reliability under extreme conditions.
The selection of heat exchanger type is a critical factor for the success of flue gas heat recovery projects. Different industrial environments require different exchanger concepts based on temperature, dust loading, corrosion risk and maintenance philosophy.
For high-temperature industrial flue gas applications, the following heat exchanger types are commonly recommended:
These are the most widely used solution for severe flue gas conditions.
Typical features:
Suitable for temperatures up to 900°C
Large tube diameters to resist fouling and erosion
Inline tube arrangement with online cleaning systems
Materials such as Sanicro 25, Incoloy 800HT, 253MA, SS310
Typical industries:
Biomass boilers, cement kilns, metallurgical furnaces, waste incineration plants.
In real industrial flue gas applications, shell & tube heat exchangers remain the most reliable long-term solutions. Compact or plate-based technologies are generally unsuitable for heavy dust, corrosive or high-temperature flue gas.
Successful flue gas heat recovery projects depend not only on thermal performance, but on material selection, fouling control and long-term mechanical reliability.
Successful projects require:
Advanced materials
Robust mechanical design
Real industrial experience
Long-term reliability focus
In high-temperature applications, flue gas heat recovery is not about selling heat exchangers — it is about delivering energy efficiency with guaranteed operational security.
