Key points
Odour Issues in frying environments
Aligned to rising concerns about air pollution, the food & beverage industry is increasingly looking for solutions to poor odour management control. Manufacturers are under pressure from stakeholders to ensure a safe odour control environment within factories and plants to protect employees and the wider community, avoiding unwelcome notices from the Environment Agency or claims from employees or the wider community.
Environmental permitting regulations (EP Regulations) incorporate the control of pollution, which includes odour. These issues are becoming all the more common due to housing being built closer to the factories.
High temperature frying environments pose specific odour issues, typically producing oil mists filled with sticky particulates during the thermal breakdown of the oil under high temperatures. Odour in the food industry is often further complicated by the combination of sticky particulates, oil mist and high humidity/steam.
The heightened frying temperatures are commonplace in the sector as production efficiency can be increased through reduced cooking time but this, in turn, can increase the chance of odour emissions. The odour comes from either the food coating, the oil in which the food is fried or the food itself and is notoriously hard to “scrub” due to the sticky nature of the particulates included within the contaminated air.
Odour is not the only unwanted by-product of this process. High temperature frying can also cause acridity, which can be harmful in high quantities. Sticky oil particulates can also coat the factory environment, causing slip hazards, damage to machinery and posing a credible fire risk.
Inappropriate extraction methods, where these particulates become trapped in the ducts themselves, can render any fire damper installation ineffective, thus any duct fire can then propagate along the duct and breach fire zones.
How to implement good odour control
Traditional BAT odour removal technologies do not cope well with the combination of oil mist, sticky particulate and steam – with most particulate scrubbers doing little to remove the odour. Therefore a multi-stage approach, specifically engineered to the specific application is required. As each situation is different, understanding the odour problem first is key to designing an effective solution:
- Understand the nature of the odour. What process is causing the odour? What is the type and quantity of particulates within the odour? What are the issues and risks that the odour is causing? Gas and water consumption analysis may often be required.
- Identify the constraints in which the odour solution must operate. What are the production extremes? What makes up the internal and external environment? Are there any budgetary restraints? Are there any trade effluent permitting requirements or restrictions on the type of system (i.e. once-through or recirculatory)
- Identify and define the desired outcomes from the odour abatement solution. What are the KPIs that define success for the solution?
All of this information should be included within the final User Requirement Specification (URS) for the design process, using the support of relevant experts in air contamination where required in its formulation. If your operating facility is subject to Environmental Permitting Regulations, then the creation of an OMP (Odour Management Plan) should be part of this process.
Typical Solutions to Odour Control
Odour reduction technology is typically made up of one or more of the following solutions:
Activated Carbon Filtration
This technology adsorbs the odour compounds onto the carbon. However, steam or high humidity will vastly shorten the life of the carbon. Sticky particulate or mists will block the carbon very quickly. Carbon systems can be large and changing beds of carbon can be difficult or costly.
Chemical Scrubbers
Chemical scrubbers recirculate a liquor across a packing media surface and pass the gas stream through, thus causing the gas and liquor to interact, with an appropriate reaction time for the chemical reaction to remove the odour. These devices though can struggle with high temperatures and cannot handle sticky particulate and droplets, blocking the packing media and fouling the recirculation system
Incineration
This methodology burns the VOCs and associated particulates. Incineration can be effective but has a high capital cost and it is hard to control the production processes in line with the correct operational thresholds of the incineration system.
UV/Plasma/Ozone
These are techniques that have varying effectiveness but are badly affected by the presence of sticky particulate and oil mists.
Wet Scrubbers
While wet scrubbers may reduce odour to some extent they should not be thought of as complete odour solutions as they do not address the gas phase. However, they are effective at removing the particulates found within the contaminated air.
They work by literally “scrubbing” exhaust streams of unwanted particulates, forcing them together with water droplets in what is known as “the impingement process”. The droplets capture the particulate matter and are then collected and removed. They can include:
- Centrifugal type scrubbers, which are efficient and economical but struggle with sub-micron particulates.
- Static bath type scrubbers, which deal with heavy particulates and are low maintenance but are not suitable for environments dealing with fats as the particulate will float and not be removed as sludge.
- Venturi scrubbers, which are a robust scrubber for many industries but are not suitable to remove particulates in many food applications (including frying) due to their complexity and the floating of oils fats.
- Impingement plate scrubbers, which have similar filtration efficiency to centrifugal types and can be an effective option for mists and particulates. They are not effective on sub-micron particulates however and, again, have no gas scrubbing for odour control.
A New Solution to the Market: The Liquid Gas Contact Scrubber
A patent-pending Liquid Gas Contact Scrubber (LGC) has recently been launched onto the market by air pollution control engineering specialists FEG Global. Already installed and working for food manufacturing clients operating in high temperature environments with odour/acridity issues, the system has been specifically built to cope with both the sticky particulates and odorous gases by use of a flexible, modular multi-stage scrubbing.
Suitable for use internally or externally, and with insurance-accepted fire barrier and CIP technology included, it looks a promising solution for odour issues in high temperature frying environments, combining the particulate-removal power of a wet scrubber with the odour control capability of traditional odour abatement technologies.
After a successful career in engineering project management and air pollution control, Chris founded FEG Global in 2004 to build a company that could solve problems others couldn’t. He now leads a team of on-site engineers, project managers and office support across a range of sectors and clients in industries such as food, chemical and manufacturing.
