Frying applications include high temperature oil frying of products such as French fries, Crisps/Chips, Noodles, Chicken, Fish, Meat and Pastries.

Potato Frying

Potato frying applications, typically include Crisps, Chips or French fries. The Centriair system removes oil, odour and gaseous compounds from the fryer gas. The clean gas will meet the strictest regulations on particles, VOCs and odours. Ductwork and rooftops are kept clean which reduces maintenance and fire risks to a minimum, and heat can more easily be recovered.

French fries are typically fried in palm oil which solidifies at ambient temperature. This makes heat tracing of drains for separated oil necessary. The installation footprint is typically larger in Chips/Crisp applications compared to French fries, as more water is evaporated in the frying process.

In many potato frying installations we recover heat from the stack. In particular when frying Crisps/Chips, significant heat can be recovered and reused for blanching, heating of the building and tap water. In French fries applications, the heat is usually recovered in the dryer to reduce the energy input to the fryer.

Meat Frying

Meat frying represents significant emission reduction challenges as the frying process typically emits fine liquid and solid particles as well as gaseous components and odours.

The off gas often contains gaseous components with strong odours at low concentrations. The particles also carry a significant proportion of the odours. Effective particle separation is therefore necessary. The particles are typically sticky and have a tendency to clog the treatment system posing a maintenance challenge and potential fire hazard.

Snack Frying

Common Snack frying applications include Tortilla, Extruded Products and Nuts. In Snack frying, oil droplets deposits in the stack and on rooftops, creating maintenance issues and may cause fire hazard. The gas typically contains more oxygen than water vapor which means that a fire can easily propagate in the stack.

Snack Frying typically generate lower gas flow rates compared to Potato frying. The particles are usually easy to separate and our small to midsize units are often enough to reach required results.


The first treatment step in all Frying applications is the removal of particles using a Centrifugal Separator. If further odour removal is needed (the particles carry part of the odour) and/or if VOC removal is required, a CentrOx system is used in which the centrifugal separator is integrated with our ColdOx technology. The efficient removal of particles allows for heat recovery using highly efficient Heat Exchangers, frequently installed in Frying applications in combination with the cleaning system.

The combination of centrifugal particle separation and oxidation of VOC and odours using the ColdOx™ technology, solves air treatment problems in the most difficult Frying processes, while reducing operation and maintenance cost compared to traditional solutions such as filters, scrubbers and incinerators.

The Centrifugal Separator operates continuously and rapidly evacuates the separated oil particles. The oil can in many cases be returned to the fryer and reused.

In the next step, the energy is recovered from the gas. This is achieved in an efficient heat exchanger that condenses the water vapour in the gas to water, while the heat is transferred to heat users in the factory (pre-heating of oil, blanching, tap water, heating of building etc.) and the water is recovered.

Finally, the gas is treated in the ColdOx™ unit in which gaseous compounds are removed along with the remaining odours.

In Meat Frying, the ColdOx™ treatment step is usually required due the high prevalence of gaseous highly active odour compounds. In Potato and Snack Frying, emission problems are typically more restricted to particle emissions but in certain processes and when restrictions on odour emissions are stringent, a ColdOx™ unit may be required.

In Meat Frying, the proper dimensioning of the Centrifugal Separator system is critical given the small particles in the exhaust gas. In addition, due to the sticky nature of the particles, a CIP™ should be installed to guarantee that the separators are kept clean


  • High particle separation performance (100% removal of particles > 1µm)
  • Efficient removal of gaseous compounds and odours
  • Low maintenance and maximum process uptime
  • Cleaner piping and reduced fire hazard
  • Low energy consumption
  • Efficient heat recovery
  • Compact installation

For more information, please visit our technology section or download our product leaflets and case studies.

Application: OLW

The customer is a leading potato crisp producer in Scandinavia with an energy intense production running 24/7. Due to high production costs, the client had a purpose to not only eliminate odour, but also find a solution to potentially recover energy from the process and use it to cover up other energy consuming areas of the plant. Centriair designed a system connecting the gas flows from the different fryers on site. The system uses centrifugal separators removing oil droplets down to 1 micron, followed by a heat exchanger for energy recovery. The heat is used to heat process water and the site building. The project has resulted in an average energy recovery of 1,7 MW over the yearly production hours with a peak capacity of 3.3 MW. It has also eliminated oil drops from the chimney and thus decreasing the costs for cleaning. Investment payback for the complete installation was below 2 years.

System data OLW

Air flow 24 000 m3/h
Incoming gas temperature 115o C, dew point 92C
Return water temperature 85o C
Delta T Water 20o C
Control and monitoring Siemens
Material All stainless steal