“NO_x Catalyst Performance on Mercury and SO₃” is very Complex - Hot Topic Hour Conclusion on February 27, 2014

The speakers yesterday demonstrated lots of expertise and experience. The clear message is that the decisions about selecting and replacing NO_x catalyst have a major impact on SO₃ and mercury emissions. You can pay more for catalyst and obtain better performance on the combination of pollutants. You can vary the replacement cycle to address the combination of pollutants and not just NO_x.

Other system decisions are intertwined with those involving catalyst.  Do you add halogens with the fuel?  How are you going to prevent mercury re-emissions?  What about fuel changes and even changes in goals such as the amount of pollutants to remove?

The speakers demonstrated that a lot of time and effort has gone into understanding the relationships among all these different variables.  Techniques for laboratory testing and micro and bench scale simulation are also improving. So the state of the art is progressing.

McIlvaine suggested that all these complex variables be segmented into three categories:

• Long shut down - Variables which can be changed only with considerable time and expense.  An example would be adding an additional catalyst level.
• Short shut down - Variables such as substituting catalyst which can be changed quickly.
• No shut down. - Variables such as the amount of halogen added with the fuel can be continuously varied. The amount of chemicals added to the scrubber can be varied to control mercury re-emissions. The quantity of ACI is another variable.

McIlvaine further questioned whether more attention should be paid to the “no shut down” variables. For example, one can compensate for the deteriorating performance of the catalyst by steadily increasing the halogen level in the fuel. Conversely, with fresh catalyst the halogen level in the fuel could be minimal.

This is exactly the opposite philosophy of “refined coal.” It provides a fixed halogen level in the fuel regardless of the system performance. One of the consequences of this operational mode may be accelerated corrosion of the air heater and other components. In other words, you have halogen overkill much of the time. But enough speculation, let’s move on to summarize the excellent presentations

Noel Rosha, P.E., Senior Applications Engineer at IBIDEN CERAM presented "SCR Catalyst Management Targeting Mercury Oxidation."

The company has developed a NO_x catalyst management plan, CATLIFE^® which calculates the number of catalyst events and the cost of those events depending on changing goals for pollutant reduction and variables such as fuel changes. Noel provided this summary.

Catalyst management planning becomes increasingly complex. Accurate catalyst management planning considers ALL aspects of SCR and boiler unit operations. MATS will change the approach to catalyst management. Catalyst management strategies can be optimized to support high mercury oxidation rates. Opportunities to optimize will be site specific and fuel dependent.

Chris Reeves, Ph.D., Development Project Manager at Cormetech, Inc, discussed advanced catalysts , COMET™ which  significantly improve Hg oxidation performance while  maintaining  high DeNO_x activity and equivalent SO₂ oxidation performance. Chris acknowledged the influence of layer position, halogen in the fuel, temperature, CO, O₂, H₂O and SO₂.  Reactor condition is another variable. Lab studies with the new catalyst show considerable improvement in mercury oxidation. One graph shows the new catalyst with over 80 percent oxidation compared to less than 70 percent with the standard offering. 

Brydger Van Otten, Chemical Engineer in the Engineering Research and Development Department at Reaction Engineering International, focused on the problems caused by  SO₃ using the MerSim^™ Model.” The model has been validated from data sets at 28 plants and takes into account varying amounts of SO₃ and the resultant change in mercury capture based on a standard set of conditions including ACI, particulate equipment, fuel etc. Some of the findings are

The entire February 27 recording can be heard at:  NOx Catalyst Performance on Mercury and SO3    86 minutes
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Bios, Abstracts and Photos are as follows:  BIOS, ABSTRACTS, PHOTOS - February 27, 2014.htm

The individual presentations are as follows:

• NOx Catalyst Performance on Mercury and SO3 Webinar - Hot Topic Hour February 27, 2014  (Webinar Recording dated: 2/27/2014)

 

• Evaluation of Mercury Control Strategies in the Presence of SO3 Using the MerSim Model by Brydger Van Otten, Reaction Engineering International - Hot Topic Hour February 27, 2014  (Presentation dated: 2/27/2014)

• SCR Catalyst Selection and Management for Improved Hg Oxidation Performance by Christopher Reeves, Cormetech. Hot Topic Hour February 27, 2014  (Presentation dated: 2/27/2014)

• Catalyst Management - Considering SCR Mercury Oxidation Co-Benefit by Noel Rosha, IBIDEN Ceram - Hot Topic Hour February 27, 2014  (Presentation dated: 2/27/2014)