Take advantage of waste heat from your industrial process to reduce costs and improve energy efficiency.
In industries where energy efficiency and cost control are priorities, air preheaters can recover waste heat from flue gases and use it to raise the temperature of an air stream.
Preheated air can be fed to equipment such as furnace burners, boilers or dryers, significantly increasing their performance.
The APH is an air-fume heat exchanger. Hot flue gases generated in furnaces, turbines, combustion engines or other industrial processes transfer their heat to an air stream.
The preheated air is fed to burners in industrial equipment such as furnaces and boilers. When burners operate with cold air, part of the heat released is invested in heating the introduced air. Therefore, using preheated air can significantly increase the performance of equipment such as process furnaces.
Preheated air can also be used in other equipment and processes such as dryers.
Traditional air preheaters were limited in the flue gas outlet temperature, which had to be kept above approximately 150ºC to avoid acid corrosion in the equipment due to condensation of the sulfur content in the flue gas.
The use of cleaner fuels in burners and the new generation of air-fume heat exchangers, with polymeric or stainless steel modules, have made it possible to install preheaters in industries that work below the acid dew point of the flue gases.
Preheater module with cast steel tubes
Air preheaters can be classified according to their geometry and material.
Tubes with external fins, internal fins or both, made of cast iron, are used. In this type of tubes, it is necessary to maintain the tube wall temperature at least 15ºC above the acid spray temperature of the fumes to avoid corrosion.
Where high corrosion resistance is required, such as in areas where the temperature is below the acid dew point, borosilicate glass tubes supported on PTFE-coated plates can be used.
However, they are more fragile.
Metal tubes enameled with borosilicate glass are used for greater resistance to acid corrosion. They withstand high operating temperatures (up to 400ºC), have good mechanical and thermal shock resistance.
Polymer matrix tubes are used for high resistance to chemical attack. They are lightweight, highly resistant to thermal shocks and have high thermal conductivity. They withstand operating temperatures up to 200ºC.
They are constructed from flat plates. They have high thermal efficiency and a flexible, compact and versatile design. A wide variety of metallurgical options are available depending on the temperature and corrosion resistance required. Very good thermal shock response.
Energy savings and emissions reduction
The efficiency of process furnaces without heat recovery is typically around 80-85%. The introduction of an air preheating system increases the efficiency up to 90%, with consequent fuel savings and reduction in CO2 emissions.
Preheaters below ADP
In preheaters working below the acid dew point of the flue gas, flue gas outlet temperatures below 100ºC are achieved, maximizing heat recovery and increasing furnace efficiency by up to 95%.
Adaptability and customization
Assembly of a module at a San Roque refinery
They are applicable in any industry with a need for hot air and with a usable high-temperature waste gas. This includes any installation with equipment such as furnaces, boilers, turbines, combustion engines, etc.
Some examples are:
At AITESA we are experts in APH / air preheaters design.
The choice between tube and plate preheaters is influenced by the following factors:
For very dirty gases, tube preheaters are more recommendable, since they have a larger cross-section and therefore less tendency to become clogged.
Both technologies can achieve very low pressure drops on both air and flue gas sides. For cases where the allowable pressure drop is extremely limited, the larger cross-section of tube preheaters makes them preferable.
At low flue gas outlet temperatures, the equipment operates below the acid spray temperature. Materials with resistance to acid corrosion should be used, such as stainless metals in the case of plate or glass tube preheaters and polymeric matrix for tubular preheaters.
Plate preheaters are more compact and lighter. For the same dimensions, they have a larger heat exchange surface.
Preheater in full operation at San Roque refinery
AITESA performs engineering services (conceptual, FEED, FEL and detail engineering), supplies and EPC projects adapted to each client’s requirements.
More than 5000 projects in strategic sectors
Maximum efficiency and minimum emissions
Comprehensive technical support and maintenance
AITESA not only installs preheaters, it creates energy solutions that optimize production, reduce costs and ensure regulatory compliance.
Annual washing with water through washing ramps installed on the equipment.
Thanks to its extensive experience in heat recovery, AITESA can execute within 12-15 months an EPC project of a complete heat recovery in process furnaces.
The need to manage the acid condensate produced in preheaters working below the acid dew point is its main disadvantage. It has a limited utilization due to its low flow rate and variable concentration. To solve this challenge, AITESA has developed an efficient, safe and easy to maintain neutralization system that transforms the acid condensate into a harmless stream that can be led to drainage.
The preheaters are designed for a service life of 20-30 years, adaptable according to the customer’s needs.
For preheaters working with acid condensation, there is the possibility to replace only the blocks or tubes affected by condensation by means of removable designs.
Talk to an expert
Aitesa has more than 40 years of experience designing and supplying heat recovery boilers.
