Thermal oxidizers are used to destroy hazardous air pollutants (HAPs), volatile organic compounds (VOC), and carbon monoxide (CO) from industrial exhaust air streams. These pollutants are hydrocarbon based and chemically oxidized to form CO2 and H2O. The three main factors in designing effective thermal oxidizers are: Temperature, Time, and Turbulence (often referred to as the three Ts).
Retention TIME increases destruction removal efficiency (DRE) on a linear basis, TURBULENCE increases the DRE to the second power, and TEMPERATURE offers the greatest method for improving DRE, typically increasing it to the fourth power.
Thermal oxidizers are the most time-tested and reliable approach for control of air emission hydrocarbons, including CO exhaust streams. Most modern manufacturing processes (if not all of them) include heat exchange in some way or another to minimize overall operating costs. The regenerative thermal oxidizers (RTO) first developed in the 1970’s offered a substantial reduction in oxidizer operating costs by increasing the integral thermal energy recovery (TER) to 95% over conventional recuperative at 75%. A 75% reduction in energy consumption was a savings that afforded a less than a year pay back time in many applications.
NESTEC’s staff, many from the original 1970’s RTO development company, has continued to develop and optimize energy saving features to reduce the overall operating cost of the MCC RTO unit.
NESTEC’s burner selection and arrangement used with the MCC RTO can have a huge effect on the fuel consumption and associated energy savings based on application design and associated conditions:
- The stoichiometry of the reaction based on the conditions (liquids, gases, fuels, LPG, etc.) and air / fuel ratio through the entire firing range
- The type and number of burners (direct-fired, regenerative, radiant tube, high thermal release, self-recuperative, low temperature regeneration, etc.)
- The energy provided from the process (BTU/hr)
- Operating temperatures
- Firing (high fire, low fire, pilot, or no pilot)
- Draft (forced or induced)
- Nitrogen oxide emissions (conventional, low, extra low)
The safe operation of all the burners is primarily supervised by a burner-management system, or BMS. These systems also are also known as burner safety systems, burner control systems, combustion safeguards, flame-safeguard systems, safety shutdown systems.
In some processes, other considerations specific to the application may come into play. In the case of CO control, the RTO purification temperature has a major effect.
- NESTEC’s MCC RTO media selection analysis establishes the specific arrangement, type, and size of the MCC RTO heat exchange media to maximize the energy savings for the application.
- The application process exhaust conditions
- Hydrocarbons (HC) and CO
- Auto-ignition Temperature
- Oxygen Content
- Total Particulate Matter (TPM)
- Potential Corrosion
- Selection of multiple various layers of heat exchange media for the application
- Maximize uniform flow distribution
- Maximize the bed temperature profile
- The NESTEC control program automatically adjusts the MCC RTO settings to the present conditions to maximize the TER and reduce the exhaust by as much as 10 degrees, with associated fuel savings.
NESTEC’s MCC RTO THERMAL ALIGNMENT program expertly and efficiently balances preheat with the recovery cycles to increase the TER and minimize fuel consumption.
- NESTEC’s MCC RTO design maximizes mass flow balance between the preheat and recovery media chambers. Typical RTOs are sold as 95% TER designs, however, very few units actually operate at 95% TER. Many RTOs operate in the 92 to 93% TER range which is a 40 to 60% higher fuel consumption then original 95% design efficiency. The savings between 93% and 95%, as shown below, is $7.98 per hour, $69,900 per year!
NESTEC’s improvements and unique features have made it possible for industry to remain in regulatory compliance while continuing to turn a profit.
If you have an application that requires air pollution control and energy conservation, or an existing RTO that needs fine tuning to provide additional energy savings, contact NESTEC for a free process analysis and proposal.
For assistance call or e-mail NESTEC Inc. (Office: 610-323-7670) for a free evaluation of your VOC control equipment needs. (http://www.nestecinc.com)
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