Fume mitigation: Essential for environmental protection

Apr 05, 2023

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Many industrial processes generate a fume that is harmful to the environment or gives off an unpleasant smell to the surrounding area.

There are many ways to break down and/or remove components from fumes, vapors and gases that are generated during these industrial processes. Among these processes, various types of industrial equipment are used to burn, combust or break down the components, including incinerators, thermal oxidizers and catalytic oxidizers.

Incinerators use high temperatures and controlled combustion to break down and neutralize fumes and gases, resulting in cleaner emissions and a safer work environment. In this process, the effluent is combustible enough to be burned with the base fuel. The base fuel can be a wide variety of fuels such as natural gas, propane, hydrogen blended fuel or diesel.

Thermal oxidizers are a common type of thermal fume mitigators, using high temperatures and combustion to break down fumes and gases into water vapor and carbon dioxide. Thermal oxidizers work by introducing the fumes and gases into a combustion chamber where they are heated to high temperatures, often over 1,400°F. The high temperatures cause the fumes and gases to break down and combust, resulting in clean emissions.

A catalytic oxidizer is another type of fume incinerator that uses a catalyst to promote combustion. Catalytic oxidizers work by introducing fumes and gases into a chamber containing a catalyst, which promotes the breakdown and combustion of the fumes and gases at lower temperatures than thermal oxidizers. The catalytic reaction has a minimum required temperature determined by the anticipated content of the stream. This technology is used when the fumes or gases being generated are not constant. The initial chamber temperature is lower than the thermal unit reducing the amount of heating fuel required on a constant basis.

There are also specialized fume incinerators designed for specific types of fumes and gases. For example, some incinerators/oxidizers are designed to handle hazardous waste, while others are designed to handle high concentrations of VOCs.

The end results of these processes usually contain large amounts of hot flue gas. There are several ways to recover some of the heat that would otherwise be lost to the atmosphere. Two such ways are recuperating energy with the inlet effluent or recovering the energy with an alternate process stream. A recuperative oxidizer utilizes an air-to-air exchanger to preheat the incoming effluent. This method does not typically require any further control points since the effluent can only recuperate so much energy with its low mass flow. A waste heat recovery unit can be used to repurpose the waste heat for another process. This method often requires some kind of secondary modulation. The oxidizer/incinerator is firing the burner based on the chamber temperature. Either a bypass damper system or side stream blower would be utilized to control and protect the secondary process fluid.

The colder the effluent or process stream is and the more mass flow it has, the cooler the flue gas can become. A cooler flue gas makes for a more efficient system — but a process can become "too efficient." Once the gas starts to reach its dew point, produced condensation can start to form. Condensation has process concerns with materials of construction and what to do with it.

Another fume mitigator provided by Astec is the Heatec fume condenser, which is used in vents of asphalt tanks to condense gas vapors present in liquid asphalt. These small amounts of fumes can escape a tank when air is being pushed out due to the filling of the tank. Condensing the vapors produces a liquid that drains back into the tank. This process minimizes the release of pollutants into the atmosphere.

Fume mitigation systems help manufacturers meet EPA requirements, providing much of the motivation behind businesses utilizing these types of systems. EPA compliance helps keep cost of operation in check, reduces emissions, improves air quality and public health, achieves climate co-benefits, and provides a forum for community and stakeholder collaboration on clean air and related issues.

Fume mitigators are an important technology for reducing the harmful effects of fumes and gases generated during industrial processes. These technologies not only help reduce emissions and protect the environment, but also improve worker safety and reduce the risk of fires and explosions. With the right technology, industrial processes can be made cleaner, safer and more efficient, benefiting both the environment and the bottom line.

For more information, visit astecindustries.com or call (423) 821-5200.