Effectively decontaminating exhaust air in the food production industry and enabling heat recovery
Summary and objective of the project
The Exairdec project was concerned with the development of an innovative contaminated air purification solution for food preparation applications. It will effectively decontaminate the waste air emitted during the different food preparing processes that contain a variety of organic gaseous and aerosol contaminants, volatile organic compounds (VOCs) and particulate matter. This will result in the elimination of a number of problems currently present in food preparation environments. The research and development undertaken within this project will provide SMEs as well as wider European community with a method of overcoming existing technical barriers to decontamination of air by using the latest scientific developments in an affordable and practical manner.
The European food preparation industry (FPI) currently faces a high percentage of work related illnesses, increasing the amount of complaints about odour and contaminant emissions. Existing systems have low contaminant removal efficiency, creating a fire risk and high capital and operational costs due to lost energy. Now, the Exairdec process increases the contaminant removal efficiency by up to 98% and allows the use of heat recovery.
This process uses a high-voltage, atmospheric pressure, ultra-short pulsed Corona discharge (PCD). “The Exairdec project has developed an innovative process, which will significantly reduce fire and air contamination risk in the food processing industry. I’m excited to see the commercial success of this project in the future” Prof Brian McKenna, EFFoST.
Major health problems are caused by low filtration efficiencies with current technology. Despite the progress made in contaminant removal in recent years, the food industry still faces a high percentage of work related illnesses (1.6 times the average). An estimated 8 per cent of all employees working in food preparation operations have had health complaints related to contamination and airborne diseases. Odour emissions are one of the most significant environmental issues, with complaints about odour becoming common as communities become more aware of air quality issues. Also, contaminated extraction ducts pose a significant fire hazard. Even low concentrations, fat residue clog or form dense layers of fatty substances in the ductwork. This constitutes a dangerous combination with occasional sparks, flames and high air flow. A cost analysis of existing filter systems reveals that on average food processing companies have annual filter disposal and system maintenance costs of three to five per cent of its total added value. Efficient removal of cooking fumes, vapours and airborne particles would do much to reduce these high statistics.
Decontaminating the exhaust air
The Exairdec project, secured with EU FP7 programme funding, has provided an innovative and highly effective removal of VOCs and soot particles from exhaust air and can be combined with heat recovery. The Exairdec system is innovative and technologically challenging and consists of an ultra-short (nanosecond) pulsed high voltage generator that drives the highly reliable PCD electrodes. Unlike other systems, the Exairdec system is capable of operating in high moisture environments. The Exairdec Consortium developed and manufactured a pre-production prototype of a commercial kitchen exhaust air decontamination device that was capable of efficiently destroying most organic gaseous contaminants in an atmospheric pressure gas stream at flow rates of up to 700 m3/hr at temperatures of 10-80°C. Final tests were conducted in a real kitchen environment at Nõmme Coffee shop in Tallinn, where the air flow rate was slightly lower (505 m3/hr) and ethanol was the major volatile organic produced during the cooking process. The Exairdec process resulted in an ethanol destruction efficiency of 98%. An Exairdec 2-stage prototype was coupled to a cyclonic particle separator (located in the kitchen hood), and when the cyclonic separator and both PCD generators and electrodes were in operation, the particle number concentration was very low, around the range that would be expected in ambient air at a rural site in the UK. The consortium calculated that purchase of an Exairdec prototype would result in a capital cost of no more than €5,000 and operating cost that result in an annual user cost of less than €3,000 for a 5-year depreciation time. The device uses no consumables and therefore the only operating cost is electricity. The consortium achieved the required decontamination performance with a space requirement for the supplementary system of less than 2m3 with appropriate sound emissions. The sound from the HV-generator and from the electrodes was barely noticeable in the kitchen. Maximum power consumption of the prototype is approx. 2000W (the power rate is adjustable from approx. 500 – 2000 W and depends on the generator output frequency).
Widespread use of the Exairdec device will have several positive impacts on environment. An Exairdec prototype coupled with high efficiency cyclonic filters will enable the use of heat exchangers in the exhaust duct and thus the implementation of heat recovery which will provide increased energy efficiency. An Exairdec device with high VOCs decontamination efficiency will provide odour-free air exiting from exhaust ducts and provide therefore less contamination-based complaints with better living and working conditions due to improved ambient air quality. Since an Exairdec device uses no consumables, no waste is produced (e.g. filter cartridges).