Process Technology Solutions
Experts in integration of process technologies
SOLUTIONS
Thermal oxidation is the rapid reaction of organic chemicals, usually hydrocarbon-based, with air at an elevated temperature, resulting in the formation primarily of carbon dioxide and water vapor. The degree of destruction or reduction efficiency (DRE) in the oxidizer is largely controlled by three design parameters: time, temperature, and turbulence.
REGENERATIVE THERMAL OXIDIZERS
A regenerative thermal oxidizer (RTO) converts volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) into carbon dioxide and water vapor through thermal oxidation.
RTOs use regenerative heat transfer to achieve very high thermal efficiencies of 85 to 96 percent, resulting in very low operating fuel costs, in some cases zero.
That makes them particularly economical for treating low VOC concentration process exhaust streams.
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The RTOs we work with are robust, have few moving parts, and are made from materials that are resistant to chemicals and heat.
CATALYTIC THERMAL OXIDIZERS
This type of equipment uses precious and base metal catalysts, depending on the application. For systems using a base metal catalyst coated on a ceramic bead substrate, our design uses a tray arrangement with a gas hourly space velocity of around 14,000 h-1.
The catalyst bed is designed in a recuperative oxidizer located between the inlet passage outlet of the heat exchanger and the combustion chamber. For systems requiring a precious metal catalyst, a ceramic lined monolith is used.
This system can be cleaned periodically by removing the beads and cleaning them before returning them to the system. A small amount of makeup catalyst is normally required after cleaning.
RECOVERY THERMAL OXIDIZERS
This system converts VOCs and HAPs to carbon dioxide and water vapor through high temperature oxidation. A recuperative heat exchanger (either a plate type or shell and tube type) is employed to recover thermal energy from the oxidation process and thus reduce fuel costs. Operating temperatures are around 1,500°F (815°C).
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Recuperative thermal oxidizers are less expensive than RTOs from a capital cost standpoint because they use lower cost materials and, because they are smaller, they use less material.
Its design is simpler than an RTO, with fewer moving parts. However, thermal efficiencies can only go as high as 65 percent. Therefore, fuel costs can be up to six or seven times more than an RTO.
INTERNAL COMBUSTION THERMAL OXIDIZERS (DIRECT-FIRED)
The simplest thermal oxidation technology is a direct combustion thermal oxidizer. The VOC and HAP process exhaust stream is introduced into a cooking chamber through a burner and is provided with sufficient residence time to achieve the desired destruction removal efficiency (DRE) of the VOCs.
Most direct fired thermal oxidizers operate at temperature levels between 1,800°F and 2,200°F, with airflow rates from 500 SCFM to 50,000 SCFM.
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These oxidizers are best applied where there is a very high concentration of VOCs to act as a fuel source (rather than natural gas or oil burner fuel) for complete combustion at the desired operating temperature.
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Typical applications include treating flare gas or other streams that have a BTU/SCF value of 500 or greater, such as landfill methane extraction off-gas