GAS-GAS HEAT EXCHANGER
At BOIXAC, we design and engineer custom gas-gas heat exchange solutions focused on improving energy efficiency in industrial processes. Our heat exchangers are optimized for energy recovery between two independent gas streams, such as air, flue gases, nitrogen or other process gases, transforming waste heat into economic savings and reduced environmental impact.
As specialists in technical design and conceptual engineering, we advise you on selecting the most suitable technology among our air-to-air and air-to-flue gas solutions. Our methodology is based on an in-depth analysis of process parameters (temperatures, flow rates, gas composition and operational constraints) to conceptualize the equipment that maximizes return on investment (ROI).
What is a gas-gas heat exchanger and how does it improve the energy efficiency of your process?
A gas-gas heat exchanger is equipment designed to transfer thermal energy between two gas streams without direct mixing.
Heat exchange occurs through a solid separation surface, typically metallic, allowing heat transfer by conduction and convection while keeping both fluids completely isolated.
Basic operating principle
The hot gas stream transfers thermal energy to the exchanger wall.
The separating wall conducts this energy through the material.
The cold gas stream absorbs the heat on the opposite side.
Direct impact on energy efficiency
Reduced energy consumption: recovered heat from the hot gas is reused to heat or cool the cold gas, lowering the demand on primary systems such as boilers, burners or electric heaters.
Improved process performance: incoming gases are preheated (pre-heating) or precooled (pre-cooling), reaching optimal inlet conditions for reactors, furnaces or process chambers.
Reduced environmental impact: lower fossil fuel or electricity consumption results in a proportional reduction in CO₂ emissions and other greenhouse gases.
Lower operating costs: investment in a gas-gas heat exchanger is recovered through continuous energy savings, with typical payback periods between 3 and 12 months, depending on the application.
Optimal design depends on multiple critical factors, which we analyze specifically for each project.
Key industrial applications of gas-gas heat exchangers
Our experience in gas-gas solution design spans multiple industrial sectors, with the goal of converting waste heat—traditionally a cost—into a valuable energy resource.
Combustion air preheating
A key application for air-to-flue gas heat exchangers. Exhaust gases from furnaces, boilers or turbines, typically at 200 °C to 600 °C, transfer energy to the incoming combustion air, improving combustion efficiency and reducing fuel consumption by 10% to 30%.
Industrial ventilation and HVAC systems
In industrial buildings, warm exhaust air can transfer energy to incoming outdoor air via air-to-air heat exchangers, significantly reducing heating or cooling loads.
Chemical and pharmaceutical processes
Gas-gas heat exchangers allow precise control and stabilization of process gas temperatures, recovering energy from other points in the installation while ensuring thermal homogeneity and reaction stability.
Treatment of gaseous effluents prior to cleaning
Before filtration or scrubbing, gases often need to be cooled to protect filters and scrubbers. A gas-gas heat exchanger enables this cooling while recovering useful energy for other process stages.
Drying and thermal treatment processes
In hot-air drying systems, exhaust air still contains significant recoverable energy that can be used to preheat fresh air, reducing overall energy consumption.
Specific gas-gas heat exchanger technologies and designs
The selected technology depends on gas characteristics, temperature ranges, particulate content and space constraints. At BOIXAC, we conceptualize the most robust and efficient solution within two main technological families.
Discover our gas heat exchanger solutions
Air-to-air heat exchangers: applications and advantages
Air-to-air heat exchangers are designed for clean or lightly loaded gas streams, typically using smooth tube bundles or plate configurations, maximizing heat transfer surface within a compact footprint.
Key conceptual design features
Flexible geometry: cross-flow, parallel flow or counterflow depending on efficiency targets and available space
Material selection: carbon steel, stainless steel or aluminum based on corrosion resistance and thermal conductivity requirements
Pressure drop optimization: balance between thermal efficiency and fan energy consumption
Main advantages
Ideal for industrial ventilation and heat recovery from clean gas streams
Simplified maintenance with access designed for manual or assisted cleaning
Long service life due to geometries that minimize fouling
Air-to-flue gas heat exchangers: energy recovery in combustion processes
Air-to-flue gas heat exchangers are designed for harsh conditions: high temperatures (up to 850 °C in specific cases) and the presence of particulates or corrosive compounds.
BOIXAC design pillars
High-resistance materials: carbon steel, AISI 304, AISI 316, or high-temperature alloys such as AISI 309 and AISI 310, selected through theoretical corrosion and oxidation analysis
Fouling-resistant geometries: smooth tubes that facilitate cleaning and reduce performance degradation
Key advantages
Significant fuel savings with fast ROI
Protection of downstream equipment such as bag filters or scrubbers
Direct reduction of the installation’s carbon footprint
Critical design and selection factors
At BOIXAC, we deliver efficient gas-gas heat exchangers through a detailed analysis of process parameters:
Temperature difference (ΔT) and thermal profile
Mass and volumetric gas flow rates
Allowable pressure drop
Chemical composition and corrosion or fouling risks
Available space and installation constraints
Cleaning and maintenance requirements
Heat recovery units
Air-tight sealing
Air preheaters
Pre-coolers
FAQs
What is the most suitable material for an air-to-flue gas heat exchanger?
There is no single optimal material; selection depends on temperature, flue gas composition and corrosion risk.
Material choice depends on maximum operating temperature, moisture presence, corrosive compounds (SOₓ, NOₓ, HCl) and the acid dew point.
For gas or diesel combustion flue gases up to 400–500 °C, AISI 316L stainless steel is commonly suitable.
For higher temperatures or environments with chlorides, sulfur or severe oxidation (e.g., waste incineration), high-temperature alloys such as AISI 309 or AISI 310 should be considered.
At BOIXAC, we perform theoretical corrosion and condensation analyses to define the optimal material for each application.
Are gas-gas heat exchangers easy to clean?
Yes. They can be designed to facilitate cleaning based on the fouling level of the gas streams.
Cleaning is a key criterion during the conceptual design phase. For air-to-air applications with clean gases, lateral or frontal access is provided for periodic manual cleaning. For fouling or particle-laden streams, we design smooth tube geometries, larger flow passages and, when necessary, integrate automatic cleaning systems such as compressed-air soot blowers or high-pressure water cleaning. In critical cases, modular designs allow individual modules to be serviced without a complete process shutdown.
What energy savings can I expect from a gas-gas heat exchanger?
In typical industrial applications, energy savings range from 10% to 30%, with fast payback periods.
Energy savings are directly related to temperature difference (ΔT), gas flow rates and annual operating hours. In combustion air preheating, fuel savings typically range from 10% to 30%. In ventilation systems with heat recovery, heating or cooling demand reductions can reach 40–70%. A process-specific energy assessment is essential to accurately calculate the actual ROI.
What is the typical service life of a gas-gas heat exchanger?
With proper design and material selection, gas-gas heat exchangers offer a long and stable service life.
Service life depends on corrosion, erosion, fouling and operating conditions. A correct initial evaluation of gas properties and material selection enables very long operating lifetimes. At BOIXAC, our conceptual designs include preventive maintenance recommendations to preserve thermal performance over time.
Which type of heat exchanger is more efficient: air-to-air or air-to-flue gas?
Both can achieve very high thermal recovery efficiencies; the best choice depends on process conditions.
Both air-to-air and air-to-flue gas heat exchangers can exceed 70–80% thermal recovery efficiency when properly designed. The correct selection depends on fouling levels, insulation between streams, thermal expansion and contraction, corrosion risk, allowable pressure drop, available space and maintenance requirements.