February 6th, 2023 | Posted in Air Cleaners
Many people enjoy the smell of a grilled steak or hamburger, or Chinese food sizzling in the wok. For those living next door to a restaurant, however, these cooking aromas can quickly become cooking “odors” and are often considered to be tiresome and may result in odor complaints. These complaints may lead to the landlord of a leased restaurant space requiring the restaurant to install a kitchen exhaust Pollution Control Unit (PCU) to address these objections. It should be noted that there are some jurisdictions that require restaurants to install PCUs per local code. These include New York City, Miami, and Los Angeles, among others.
These odors can be mitigated with PCUs designed to remove the source of the odors from the restaurant kitchen exhaust. Since most of the odor is carried on the oily greasy smoke particles from the grill or wok, these PCUs are designed to address removal of smoke particles from the kitchen exhaust airstream.
Two of the most common types of PCUs are media air cleaners and electrostatic precipitators (ESPs). While media air cleaners can work for kitchen exhaust applications, they clog up quickly with the oily smoke and require excessively frequent and expensive filter replacement. When the filters of a media PCU are full, no air can pass through, and smoke will back up into the kitchen shutting down operation until the filters can be changed. ESPs do not clog up and their filters are washable and reusable. Consequently, for restaurant kitchen exhaust applications, ESPs are the clear technology of choice.
ESPs used for restaurant kitchen exhaust filtration are generally of the “Penny” type. These units consist of two stages. In the first stage the kitchen exhaust passes through a strong electrical field. This electrical field ionizes the smoke, grease, and other particulate. This is followed by the second stage, or “collector” section which is charged oppositely to collect the now charged contaminant. This contaminant sticks to the collector section plates and the remaining clean air, now free of contaminant, passes through.
How clean does the air get when passing through a properly designed ESP? Air Quality Engineering Inc’s (AQE) standard 2’x2’ ESP module is 95% efficient at a 2,000 cfm flow rate. Higher efficiencies are achievable via two methods:
There are three standard sizes of ESPs manufactured by AQE designed for airflow rates of 2,000, 4,000 and 8,000 cfm, also these individual units can be combined either side-by-side, stacked or both for airflow up to 40,000 cfm!
ESPs work well until the collector plates become thickly coated with contaminant. This buildup acts to insulate the collector plates from the kitchen exhaust and the ESP stops working unless it is cleaned. Cleaning a restaurant kitchen exhaust ESP can be a nasty job. Therefore, manufacturers offer self-washing ESPs to ease the burden of maintenance. This self-washing is accomplished via a spray bar that hoses down the collector section with hot soapy water. A number of manufacturers offer self-washing ESPs. Not all self-wash systems, however, are equally effective. Most older designs use a fixed spray bar with nozzles that provide a cone-shaped spray pattern, this cone-shaped low velocity pattern is necessary to cover the plates from a fixed spray bar.
Air Quality Engineering, Inc offers a restaurant kitchen exhaust PCU that is equipped with a more effective spray bar installation. This spray bar is equipped with “jet” type spray nozzles which “blast” the collector section clean. In order for the jet type nozzles to wash the entire collector section, the spray bar moves in both a back-and-forth motion as well as rotating side-to-side as it moves back-and-forth. This covers the entire collector section with high pressure jets, resulting in much greater cleaning efficiency. Since clean collector sections work better than dirty collector sections, the moving spray bar is a superior engineering solution for a self-washing ESP.
Some installations may require “polishing” or post-filtering with additional odor control modules employing sorbent medias such as activated charcoal. These are available as part of the PCU package. It is also important to look for a restaurant kitchen exhaust PCU that can be easily programmed for wash cycles that match the output of the kitchen and the usage of the PCU. For example, some applications require cleaning weekly while others may require cleaning every other day. This can be easily accomplished with a remotely mounted control module in the kitchen (rather than having to go up in the ceiling or onto the roof to reset the timer).
To summarize, when specifying a restaurant kitchen exhaust PCU, look for the following:
Contact your Air Quality Engineering applications specialist for guidance on selecting a PCU for your restaurant kitchen exhaust filtration needs.