Many may feel that modifying or renewing an air permit can be a time consuming task, a new permit provides an opportunity to incorporate new monitoring technology that has other benefits. For instance, some may ask whether they should continue using opacity monitoring for their CAM requirements or if can they eliminate much of their manual monitoring by taking the opportunity to review their current practices.
First Emissions Monitoring Methods
Many older air permits simply required manual monitoring or visual inspections to satisfy state or local regulations. If you were considered a major source, you were probably subject to an EPA regulation and required to use optical devices or COMs (Continuous Opacity Monitor) on your major emission points
These manual methods were used to indirectly measure particulate emissions levels. These included EPA method 9 and 22, which require a person to conduct a visual inspection of the stack from a distance and estimate opacity levels over a 30-60 second time frame. Other air permits called for monitoring differential pressure on the dust collector. DP was used due to its relative correspondence with collection efficiency (baghouse peak collection efficiency occurs when operating between approximately 3” to 6” of pressure drop). However, both of these methods have limitations and can require a lot of labor time and effort depending on the size of the plant and the number of collection systems.
Benefits and Drawbacks of Opacity Monitoring
Opacity monitors or COMs were widely used for stack monitoring, and in many cases required by EPA regulations and, therefore, often in state regulations as well. Opacity meters directly measure particulate emissions from the stack. These meters bounce a beam of light between two mirrors and measures the loss of strength as it passes through the air between. In this way it can accurately measure opacity of 10% or higher. For many years this became the standard for compliance dust collector monitoring. In more recent years, optical technology has improved to increase the detection range so that levels below 10% opacity can be reached.
Some of the drawbacks of using optical devices include cost, maintenance and detection levels. Optical devices generally cost more than other styles of monitoring. When you factor in ongoing maintenance and calibration of the device, the costs can outweigh the benefits. Further, continuous opacity monitoring's value as an early warning alarm is limited since if it can only detect roughly 10% opacity - often when an alarm sounds an exceedance has already occurred.
As an example, one MACT standard for secondary lead smelting, required emissions levels below what Opacity monitors could provide and requires a triboelectric Bag Leak Detection System (BLDS) instead. As with visual and DP monitoring, opacity meters can still be found on many air permits but newer or improved monitoring methods may be a better choice for your facility going forward.
Why Consider Changing Monitoring Methods?
Depending on your particular situation you may not have much of a choice. Your compliance regulations may require the use of a particular monitoring method (such as falling under a MACT standard that still requires a COM or CPMS). Still, there are compelling reasons to switch to triboelectric monitoring as the basis of your CAM plans (Compliance Assurance Monitoring) for your pollution control devices.
Triboelectric detection systems allow operators to monitor emissions much more accurately and with much greater sensitivity than opacity meters. Triboelectric units can detect much lower particulate concentrations, detecting increases in emission levels before they become visible. This greater sensitivity means triboelectric systems can detect an increase in emissions long before they reach reportable levels. For this reason, triboelectric systems are widely used to detect leaking filters in dust collectors. In real world installations, tribo systems can trigger an alarm at the onset of a bag beginning to leak - reducing downtime by allowing for quicker maintenance remediation and improving environmental performance. Opacity meters and manual monitoring methods are simply not capable of performing at this level.
Operational data from triboelectric systems allow for better operations and maintenance. By tracking any changes in emissions over time, operators can adapt production to stay within required emissions levels without fear of going over the permissible limits. Further, maintenance planners can see bag performance over time and predict when filters will eventually fail. This means no more guessing how long you can use your filters and no need to change them early to avoid problems. It also provides them extra time to prepare for filter change outs - including ordering materials, scheduling downtime and hiring outside contractors. In addition to filter performance, operators can also see that the collector is properly operating and cleaning, and when it is not, indicating possible issues with solenoids or diaphragms. A BLDS is a valuable tool for properly maintaining dust collection systems, and a well maintained dust collection system is your tool for staying in compliance.
Triboelectric detection systems are far easier to install, maintain and operate than opacity based systems. Triboelectric systems are simple to install and require less maintenance then optical systems which need periodic calibration, polishing of mirrors or modification when process conditions change. In addition, triboelectric systems generally cost less than COMs or optical devices and because they monitor 24/7, replacing manual monitoring methods can cut labor costs and eliminate human error as well.
Benefits to Changing Monitoring Methods Far Outweigh the Costs
While installing a new technology may require some time and resources, the benefits outlined above make triboelectric monitoring worth the effort. Triboelectric systems require minimal upkeep and have a long history of reliability. (Some Auburn’s units have remained in continual use for over 2 decades!) Even if you are not required to update at this time, the advantages provided by tribo technology will provide a significant return on investment.
The biggest thing to keep in mind is this. Don't simply copy and paste your last air permit application. Maybe nothing has changed and you should resubmit precisely the same thing. On the other hand, maybe a lot has changed - with your operation and with technology. It is worth exploring your options as you plan your air permit renewal to avoid inadvertently locking yourself into a restrictive permit.
Plan your next permit renewal
Maybe you're saying to yourself "Sounds interesting, but my air permit renewal isn't on my radar for another year."
We understand. Here's what we'll do. If you tell us when it renews, we'll reach out six months in advance to remind you and offer the opportunity to discuss your monitoring options with you.