Controlling Flow Rates on a Carbon Injection System for Mercury Capture

Posted by Justin Dechene on Mar 29, 2016 9:30:00 AM

The Mercury Emissions Challenge

The EPA’s Mercury emissions standards have proved one the biggest environmental regulatory developments in the US in the last 30+ years. Industry was vocal in their hesitation about the formulation of these standards for decades. After the rules were codified in 2005, the MATS or Mercury and Air Toxics Standards faced vigorous opposition, with over 20 states suing to have them vacated with the case even reaching the United States Supreme Court in early 2015 and 2016. 

Tribo_flow_probe_installation.jpgRegardless or whether the standards will be kept, modified or abolished, many facilities have already taken steps to control mercury emissions from their emissions sources. For many, this involves the use of activated carbon injection systems.

That raises questions:

  • What is activated carbon injection?
  • How can triboelectric devices play a key role in this technology?

Controlling Mercury Emissions

Various applications create mercury emissions. The largest source of mercury emissions is coal-fired power plants. In addition, waste incinerators, and ferrous and non-ferrous metal refining applications generate substantial mercury emissions.  The mercury contained in the flue gas is often able to pass right through any pollution control device, including fabric filters. 

Carbon injection is one method developed to control mercury emissions from these sources. Powdered activated carbon is injected into the flue gas where it absorbs the mercury. Then, the added carbon dust is easily collected by the dust collection device at the end of the treatment process where it is disposed of safely. 

Carefully Controlling The Injection Process Using a Triboelectric Flow Monitoruse triboelectric detection for flow no flow instrumentation to optimize carbon injection

Using carbon to capture mercury is no simple task. Careful proportional mixing and dispersion of the carbon is essential for efficient collection of the mercury. Additionally, monitoring the critical flow of the carbon is made more difficult by the abrasive nature of the material as well as the large amounts of carbon being injected. 

By using triboelectric monitors from Auburn Systems, many facilities have been able to achieve better results knowing if the have More Flow/Less Flow. Auburn Systems TRIBO product line uses a small solid tungsten carbide probe to monitor flow in the injection pathway. Using the TRIBO system, plants can accurately monitor the injection flow rates in real time, assuring the continuous delivery of activated carbon into the flue.  Depending on the size of the injection line, a non-intrusive approach is also available by using a ring sensor to monitor the flow of activated carbon as it passes through the sensor ring.  Compared to other mechanical devices that quickly wear out with abrasive materials, and sometimes even contribute to the formation of blockages, TRIBO flow monitors are hassle free and provide operators with the data they need in real time.

Conclusion

Mercury capture can be difficult, so why not improve the process with triboelectric flow monitoring for your carbon injection system? Let Auburn use its more than 40+ years of experience in process industries to assist your facility in improving its carbon injection system! Click here to contact us to learn more or request a free consultation from one of Auburn’s experienced engineers now! 

 

Topics: Process Control, Flow Control