In the bustling heart of any culinary haven lies the kitchen, where delicious meals are crafted and magic happens. But behind the scenes, there’s a crucial component that ensures the kitchen’s smooth operation – the exhaust system. An efficient kitchen exhaust system not only ensures a comfortable environment for chefs and staff but also guarantees safety by eliminating hazardous fumes and greasy residues.
Among the myriad of components that constitute an kitchen exhaust system, filters stand out as the silent heroes. They play a pivotal role in capturing grease, smoke, and particulate matter, ensuring clean airflow and reducing fire hazards. But not all filters are created equal. Let’s delve into the world of advanced filter technologies that are revolutionizing the kitchen ventilation landscape.
Before reviewing current kitchen exhaust filtration devices, it is essential to understand what is in the cooking effluent or byproducts of cooking. Typically, there are grease particulates in various sizes, measured in microns. Different cooking processes produce different particulates across a range of sizes. Water vapor and smoke are also present. Mechanical filtration, which this article is addressing, has limitations regarding its efficiency, which would be expressed in a range—for example, 78% to 93% on particles 5 to 10 microns. With more sophisticated testing methods and analyzers, the days of an absolute number for efficiency are over. One would question if the efficiency were stated as one number, such as 98% efficient! When you get below 5 microns in size, the particles tend not to have sufficient mass to be “spun” out of the air stream like a wet towel. A cooking process such as a deep fryer has a higher vapor content and smaller particulate than a charbroiler.
Baffle filters use a series of overlapping “U” or “V” configuration vertical baffles to capture grease and other particles. Their primary role is to reduce the spread of flames They are the least expensive filters, but also the least efficient. Some baffle filters’ efficiency range is as low as 20-30% on particles 5-10 microns. Any grease not captured at the source will travel in the duct, some depositing there, then ultimately in the exhaust fan and onto the roof.
Compact and efficient, cartridge filters offer a high surface area for filtration. These types of extractors tend to have higher pressure loss (static pressure) due to the labyrinth path the air flows through. The efficiency of cartridge type extractors tends to be higher than that of a baffle filter but at a static pressure cost. The implication is that you will need more energy to move the same amount of air.
In kitchen exhaust filters, the advent of multicyclone extractors has emerged as a the best combination of low static pressure and high extraction rate. With a greater understanding of grease generation from cooking processes and the technology to measure grease particles, a new generation of grease extractors were created. . The design abandoned previous designs.
What is understood is that surface area, turn of direction, and length of travel would create an optimized mechanical filters. The clever design has air enter the face of the extractor and instead of traveling directly through the filters, the air enters individual vertical chambers across the filter face and air exits from the top and bottom. At first glance it appears that there would be significant pressure loss, but the new style extractors has twice the free area than traditional baffle or cartridge filters. The efficiency range for a multi cyclone extractor is between 78%-99% on particles 5-15 microns in sized. The design also facilitates easy cleaning, and its non clogging design reduces maintenance. Moreover, it’s an effective fire- barrier.
The previous extractors are used in the exhaust hood. If a more complete removal of grease and smoke are required, Pollution Control Units are used in lieu of exhaust fans. They have multi stage filteration and can achieve efficiency as high as 99% with the use of a HEPA filter. The following provides a brief overview of the primary filtration and odor removal devices in pollution control units.
The ESP (Electrostatic Precipitators) consists of two main parts: the collection electrodes and the discharge electrodes. The air containing particles flows between these electrodes. The collection electrodes , which may be flat vertical plates These plates are charged with a high voltage, usually in the range of 30,000 to 70,000 volts. Suspended between the collection plates are discharge electrodes, which are also charged, but with a much higher voltage (typically 60,000 to 100,000 volts. These electrons attach to the particles in the air stream, giving them a negative charge
As the air passes between the collection and discharge electrodes, the negatively charged particles in the air are attracted to the positively charged collection plates. The negatively charged particles repel each other, reducing the chance of re-entrainment into the gas stream. The grease particles drain off the plates into a reservoir.
Activated Carbon Filters
Used for odor control, these filters employ activated carbon to absorb and neutralize unpleasant odors. The most absorbent carbon is coconut shell. Similar in structure to pumice, the charcoal absorbs gases. The carbon will need to be replaced when it fills. Some systems have odor monitors that can detect when the carbon is spent.
In conclusion, the world of kitchen exhaust filters is vast and varied. From traditional baffle filters to the multicyclone extractor technology, the choices are aplenty. As the culinary world continues to evolve, so does the need for efficient, safe, and state-of-the-art ventilation solutions. By staying informed and choosing the right filter, restaurants and commercial kitchens can ensure not just delightful meals but also a safe and pleasant environment for all.
If you are interested in further information on commercial kitchen exhaust filters, the experts who manufacture your commercial kitchen ventilation system should be able guide you on the proper selection of filtration you will need for your facility.
Our recommended next article would be: Specifying Commercial Kitchen Exhaust Hoods. What you need to know to get started.
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