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Industrial Thermal Oxidizers

By September 17, 2012December 26th, 2021Briefs

Destroying More than Contaminants

Thermal Oxidizers, or vapor incinerators, are used widely in industrial applications for the destruction of volatile organic compounds (VOCs) for air pollution control. Sure, there are emissions requirements that must be met, but did you know that in addition to destroying contaminants, you could be burning up money as well?

In order to ensure destruction of the VOCs, the temperature of the waste air stream must be raised to a relatively high temperature, typically in the range of 1,200 to 1,800 degrees F or even higher.

Generally, some sort of fuel is needed (at least in part) to bring the temperature of the waste stream up to the temperature that provides acceptable oxidation (burning) of the contaminants. This fuel is usually natural gas. At $0.60 to $0.80 per therm, minimizing the amount of natural gas used can save lots of money. So how do we minimize the fuel usage?

Thermal Oxidizer Types

A thermal oxidizer with no heat recovery is called an afterburner. Within this category, there are also thermal oxidizers that recover heat in some form. These are recuperative thermal oxidizers and regenerative thermal oxidizers (RTO). These provide obvious benefits over a straight afterburner, as heat is recovered from the relatively hot exhaust gases.

If you need to install a new oxidizer, consider using a regenerative thermal oxidizer. This oxidizer has two flow paths each with ceramic media in a bed. Flow is alternated through each bed so that one is transferring heat to the cool incoming untreated air while the other “cool” bed is being used to recover heat from the hot treated exhaust. The flow is then switched back and forth between the two beds.

Another option is to install a recuperative thermal oxidizer. This is generally not quite as efficient as the RTO described above. A recuperative thermal oxidizer uses the hot exhaust to pre-treat the cool incoming air in a heat exchanger. The recovered heat could also be used elsewhere in the facility wherever it is needed. An example of this would be a waste heat boiler to produce steam.

Another type of oxidizer is called a catalytic oxidizer. This also involves using heat to oxidize contaminants, but it also incorporates a catalyst material to lower the temperature at which proper oxidation of the contaminant occurs – generally in the 500 to 650 degrees F range. The benefits of a lower temperature include much less supplemental fuel use. Heat recovery can also be applied to this technology. Of course, the catalyst material adds expense and maintenance.

Regardless of the option you choose, if your waste stream consists of a large volume with a relatively low concentration of VOC, consider adding a concentrator to your oxidizer system. This is exactly what it sounds like. The concentrator has media that adsorbs the contaminants from the waste stream prior to the oxidizer. The media is then “regenerated” with a lower-volume higher-temperature air stream that is then oxidized more economically.

Select the Proper System for Your Application

In addition to selecting an oxidizer that is compatible with your contaminant stream, make sure that you select a system that provides the most heat recovery possible. Consider this; if you have 20,000 cfm of exhaust air at 1,500 degrees F, and you can recover heat so that the exhaust temperature is dropped to 300 degrees F, the amount of heat recovered is over 8 million BTU per hour. That is equivalent to over 100 residential furnaces!

Michaels Energy

Author Michaels Energy

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