10 Tips for Upgrading Thermal and Catalytic Oxidizers

Upgrading and maintaining oxidizers can increase equipment capacity and reduce operating costs.

An emphasis on air management within converting-process dryers and ovens is critical to the operation and efficiency of the process, as well as the pollution control systems treating exhausts containing volatile organic compounds (VOCs). Equally important is the oxidizer’s operating efficiency -- a significant factor when considering the total cost of ownership.

By upgrading older catalytic oxidizers, thermal recuperative or regenerative thermal oxidizers, or direct-fired oxidizers, you can both potentially increase your equipment capacity and reduce operating costs. Here are 10 suggestions for oxidizer efficiency improvements that can help you achieve those goals.

Tip 1: Replace the Heat Exchanger If Needed

By swapping a worn or damaged heat exchanger for a properly designed replacement, you can reduce operating and maintenance costs, extend the life of your equipment and ensure that you continue to meet emission regulations. Cost-effective, direct-replacement heat exchangers are available as well as higher efficiency customized units that address specific needs such as corrosive environments, thermal expansion or cleanability.

Heat exchanger rebuild configurations include plate-type, shell-and-tube or custom-designed units.

Tip 2: Consider Secondary Heat Recovery

Secondary heat recovery systems are used to capture excess energy in the clean exhaust stream of processes or oxidizers.

Two keys to effective energy recovery are first to identify the optimum sources of and uses for the energy and, second, select the most cost-effective, efficient system to collect, transport and deliver the energy. Benefits for recovering heat energy may include improved equipment performance, enhanced capacity, efficiency or greenhouse gas reduction. Heat recovery should be addressed only after the process, oven or oxidizer systems have been maintained and optimized.

Uses for recovered energy include:

Combustion air preheating or heating.
Process makeup air systems.
Building makeup air heating systems.
Hot water systems (plant boiler loop).
Low temperature steam applications.

Types of heat recovery systems include thermal oil systems, air-to-air heat exchangers, air-to-glycol systems, air-to-steam boiler systems, air-to-water systems and adsorption chiller units.

Tip 3: Consider Media or Catalyst Replacements

The pressure drop associated with the random-packed heat exchange media used in certain regenerative thermal oxidizers is high when compared to modern structured media. By replacing random-packed media with structured media, the pressure drop across the unit is reduced, helping air pass through the oxidizer more efficiently. This affects energy usage and thus cuts operating costs.

Benefits include thermal efficiency, reduced electrical costs and capacity improvements. Structured media can improve thermal efficiency, resulting in lower fuel usage and carbon emissions. Lowering the pressure drop across the oxidizer allows the exhaust fan to operate at a lower brake horsepower (BHP), resulting in reduced electrical costs. And, improved throughput can be realized by replacing random-packed ceramic media with structured media while maintaining VOC destruction.

Tip 4: Perform Preventive Maintenance

As part of a preventive maintenance (PM) program, you can replace worn or obsolete parts with replacement parts and upgrades that can keep your equipment operating at peak efficiency. Preventive maintenance also minimizes downtime, ensures peak performance, helps meet regulatory requirements and frees in-house maintenance staff for other tasks.

Tip 5: Consider Controls Upgrades

Numerous controls upgrades are available to replace outdated hardware, temperature controllers or PLCs to minimize downtime and aid in diagnostics. Logic changes such as air-to-gas ratio control also can improve equipment efficiency. Proper interface with the process to reduce system demand when the process is down or in make-ready condition can reduce system demand.

Tip 6: Work on Flow Reduction and Optimization

Many times, process flow or temperatures are increased to compensate for deficiencies within the system. The result typically is excess fuel usage. The process can be balanced to provide quality product at desired production speeds and documented for a parameter baseline.

Tip 7: Repair Damaged Insulation

Loose or damaged insulation can result in severe damage to equipment, unplanned downtime and safety issues. Underinsulated equipment or ductwork leads to excess radiant heat losses.

Tip 8: Properly Adjust Valves and Timing

Proper valve adjustment and timing are critical to energy optimization and destruction efficiency on your regenerative thermal oxidizer.

Tip 9: Repair Leaking Gaskets and Loose Dampers

Leaking gaskets and seals can lead to heat loss or serious damage to your equipment. Loose, damaged or worn dampers can leak excess air into the system, which then will be heated and treated by the oxidizer system unnecessarily.

Tip 10: Take Care during Burner Setup

Proper burner setup is important to ensure it is operating at its optimum fuel/air ratio throughout the firing range. Improper setup can lead to additional fuel usage and products of combustion.

This article originally was published with the title " 10 Tips: Improving Oxidizer Efficiency" in the September 2009 issue of Process Heating.