Three ways to control VOC emissions.
In recent years, few environmental issues have been looked at more closely than the emission of volatile organic compounds (VOCs). Since the Clean Air Act Amendments of 1990, increasingly strict regulations have been presenting the woodworking Industry with numerous challenges regarding VOC control. Recent technological advancements have opened up a new range of VOC-control units to help woodworking plants meet or exceed compliance standards. Among the VOC-control units being developed are those which are regenerative; they add to the manufacturing process by allowing for energy recovery.
Here is a closer look at three major types of air pollution control technologies: regenerative thermal oxidizers (RTOs); catalytic oxidizers; and regenerative catalytic oxidizers (RCOs). All three have advantages and disadvantages and should be tailored toward specific plant requirements.
Regenerative Thermal Oxidizers
RTO systems destroy VOCs and other hazardous pollutants by raising the process exhaust to its oxidation temperature, approximately 1,500F, and maintaining it at that temperature with sufficient oxygen for a minimum of at least half a second. The VOCs are thereby oxidized to carbon dioxide and water, which can be harmlessly discharged into the atmosphere.
An important advantage of RTOs is that they provide an extremely high heat-recovery efficiency, which means low energy bills for the user. RTO units have a low operating cost and a long-system life.
One disadvantage of RTOs, however, is that their large size and weight can restrict where they are used.
One alternative to thermal oxidation is catalytic oxidation. A catalytic oxidizer is an insulated metal-constructed combustion chamber that has a temperature-controlling burner and a catalyst section.
In this system, the solvent-laden air is preheated as its passes through the heat exchanger into the combustion chamber where its temperature is brought to oxidizing levels before passing through the catalyst. The cleaned gases then release up to 65 percent of their energy back into the heat exchanger before venting into the atmosphere.
The decision to select this system is made in part by the contents of the airstream. Knowing what is in the airstream could determine what catalyst technology is chosen or whether a catalyst technology will need periodic cleaning or will be potentially damaged by the contents of the airstream.
Regenerative Catalytic Oxidizers
The RCO is a new VOC-abatement technology that combines the energy efficiency of RTO units with the lower temperature requirements of catalytic oxidation. The unit's platinum group metal catalyst allows oxidation to take place at approximately 800F, nearly half the temperature requirement in a typical RTO system. The result of this lower temperature is a significant reduction in the natural gas needed to fuel the VOC-abatement system.
CONTROLLING VOC EMMISSIONS
The initial capital cost of the RCO may be higher than an RTO, but the energy savings resulting from the system's lower operating temperature may help to offset costs.
In some cases, the RCO system is not the most effective solution for a particular facility's needs. Much like the catalytic oxidizer, the choice of catalyst will depend on what is in the gas stream and what the potential is for poisoning and masking of the catalyst. The potential for catalyst poisons exist if the VOC stream contains silicon, phosphorous, arsenic or other heavy metals that may be used in the manufacture of wood products. Although the catalyst can be repaired by being rewashed and reheated, it is important to discuss individual airstreams with process emission suppliers before deciding on a VOC-abatement system.
Depending on conditions, all three technologies can be efficient means of eliminating VOCs before they can be released into the atmosphere. For companies which are looking to comply with strict VOC-control regulations, it is important to determine their own plant requirements. For facilities with low flow rates and high VOC loading (5,000 scfm or less), catalytic oxidizers may be the right choice. For facilities with medium- to high-flow rates (over 5,000 scfm), both the RCO and the RTO may be viable options.
Considering today's increasingly stringent emission control regulations and an onslaught of standards still to come, planning and preparation are vital for wood producers who wish to survive the rough waters of today's stormy regulatory climate.
Richard Gay is director of marketing for Iselin, NJ-based Engelhard Process Emission Systems, a supplier of technology, systems and equipment for the removal and destruction of volatile organic compounds, nitrogen oxides, carbon monoxide and other hazardous compounds from stationary source process streams. He can be reached at (908) 205-6829.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||volatile organic compounds|
|Publication:||Wood & Wood Products|
|Date:||Sep 1, 1997|
|Previous Article:||Improve edge bonds using less glue.|
|Next Article:||The hoopla over laminate flooring.|
|VOC rules challenge FRP processors.|
|Foundrymen discuss EHS issues.|
|Clearing the air on emission estimates: over-estimating emissions can cost your foundry money.|