by Amanda Gogates, Cascade Global Product Manager, Emerson

Nitrogen oxides are powerful pollutants that can cause smog and acid rain and contribute to the development of tropospheric ozone. It’s critical to control nitrogen oxide (NOx) emissions to protect the environment and meet environmental regulatory requirements. NOx occurs as a result of combustion occurring in the presence of nitrogen and results from combustion processes in turbines, crackers, combustion engines, boilers, and other locations within a plant.

Ammonia can be used to react with NOx at high temperatures in order to turn it into molecular nitrogen and water vapor. Both selective catalytic and selective non-catalytic reduction (SCR and SNCR) are techniques used worldwide to remove NOx in DeNOx reactors.

However, this process can result in a byproduct of unreacted ammonia, or ammonia slip. Operators must use the precise amount of ammonia since either too much or too little can be problematic. Not enough ammonia will result in emissions, while too much ammonia can lead to waste.

As a result, continuous measurement and monitoring of ammonia slip is needed. However, such measurement can be challenging, especially in high-dust, high-temperature environments.

The video describes the Emerson DeNOx Optimization Solution, a unique system using the Quantum Cascade Laser. I think you’ll find this solution interesting and maybe a bit surprising.

For questions on how this system can both optimize DeNOx and maintain precise measurement of ammonia slip, please contact me at Or get more information on the Quantum Cascade Laser analyzer technology here.


Hi. I’m Ruth Lindley and I’m happy to get the chance to tell you how to solve a significant problem in refining in a relatively simple and straightforward manner. The problem is ammonia slip.

TypicalNOxNitrogen oxides result from the combustion process in turbines, crackers, combustion engines, boilers, and other locations within a plant. NOX is a powerful pollutant, so it is important to control and contain NOX emissions. Both selective catalytic and selective non-catalytic reduction (SCR and SNCR) are techniques used worldwide to remove NOX. However, this process can result in a byproduct of unreacted ammonia, or ammonia slip. Continuous measurement and monitoring of ammonia slip can be a challenge to ensure sample integrity is maintained, especially in high-dust, high-temperature applications. But regardless of the complexity, to adhere to environmental guidelines, operators must balance using the precise amount of ammonia – not enough ammonia results in waste, too much can lead to emissions.

So how to solve the ammonia slip problem? The answer is QCL/TDL laser technology. (You may not have been expecting that!) In fact, capable, fast Rosemount QCL/TDL technology delivers the needed measurement precision (0–100 ppm) to ensure production is at its optimum and avoid overdosing issues that result in both economic and environmental problems and cost.

Quantum Cascade Lasers monitor ammonia slip to avoid the formation of damaging ammonia salts downstream or emission of 5100captionammonium chloride or gaseous ammonia, and the regulator fines and penalties that result. Here are some of the benefits of Quantum Cascade Lasers in this challenging application –

  • Interference-free monitoring of the presence of ammonia slip in the toughest environments
  • Thousands of measurements per second are recorded using patented laser chirp techniques to ensure identification of even trace levels of ammonia
  • Ammonia slip detection and insight into the efficiency of the plant’s NOX reduction system resulting from real-time measurement and analysis
  • Rugged, modular design delivers outstanding reliability and measurement stability in extreme operations
  • Monitoring of up to twelve critical component gases for all industrial applications, toxic gas detection, and plant-wide emissions monitoring
  • No consumables, no calibration, and no in-field enclosure or shelters reduce cost and simplify maintenance and upgrades

For additional information on the specific QCL/TDL laser products that might work for you, click HERE.

The QCL/TDL laser solution to ammonia slip may seem almost too good to be true – but it’s real and operating in plants worldwide. It’s time for all of us to adjust our thinking on the ammonia slip issue, accepting that there is a better way to overcome it efficiently, reliably, and cost-effectively.

Have thoughts or questions about QCL/TDL laser technology? Post them HERE!

By Doug Simmers, Combustion Analyzer Worldwide Product Manager, Emerson Process Management, Rosemount Analytical

Hi! Doug Simmers here. Today, I’d like to talk about flue gas analysis. In the real world, budgets are always tight — personnel and resources are always constrained. It’s critical that plants implement technologies that make plant operation easier, faster, less costly, more compliant, and more efficient. One area where this is crucial is in improving boiler efficiency. Plants with large boilers or industrial furnaces must maintain optimum oxygen levels in flue gases to maximize their boiler efficiency.

AutoCalProbeTo ensure that flue gas oxygen levels are always accurate, the new Rosemount Analytical 6888 oxygen probe from Emerson now offers an online “calibration recommended” diagnostic which tells plant personnel that a given oxygen probe needs to be calibrated.

Calibration solenoids mounted inside the probe head make calibrations easier than ever, without requiring a technician to visit the analyzer. It also eliminates the cost of installing and wiring a separate solenoid box. The calibration recommended diagnostic also removes the need to conduct calibrations on a schedule. eliminating many scheduled calibrations that are actually unnecessary.

6888_see_thruThere are several new diagnostics available in today’s advanced oxygen probe technology, including a “plugged diffuser/filter” alarm for applications that have fly ash or other particulate entrained in the flue gases. Also, a “stoichiometer” feature indicates the level of reducing conditions if the oxygen readings go to zero percent. In addition, an elevated temperature capability for furnaces that operate at very high temperatures is also a feature that’s available and should be considered. These new diagnostics permit operators to run boilers and furnaces with confidence that the best efficiency is being maintained without compromising safety.

Advanced diagnostics and automatic calibration improve accuracy in flue gas analysis which is crucial not only because it provides better combustion efficiency, but also because it minimizes the production of greenhouse gases such as CO2 and 530thermal NOx, improving plant compliance with environmental regulations.

Get more information on advances in flue gas oxygen analyzers or watch our video on efficiency and cost-savings in flue gas analysis.

What kinds of flue gas oxygen analysis challenges are facing your plant? Can new technologies improve your boiler efficiency and keep you off the stack?

This is Doug Simmers, and I’m the worldwide product manager for combustion flue gas analyzers at Emerson Process Management, Rosemount Analytical. Combustion flue gas analysis is used by power plants to optimize fuel/air ratio. By measuring the amount of excess oxygen and/or CO in the flue gases resulting from combustion, plants can operate at the best heat-rate efficiency and lowest NOX, and generate the least amount of greenhouse gas. The theoretical ideal, or the stoichiometric point, is where all fuel reacts with available oxygen in the combustion air, and no fuel or O2 is left over.

NOx as a function of flue gas excess O2 Relationship of NOX production

In actual practice a perfect mix of fuel and air may not be achievable, operation with 1-3% excess O2 and  low parts per million of CO may result in the max achievable heat rate.

In addition to achieving the best combustion efficiency, many plants also have other important goals that effective combustion analysis helps to accomplish: minimizing NOX emissions and reducing slag.

Minimizing NOX
Effective combustion flue gas analysis enables power plants to lower costs and minimize emissions by preventing slag and controlling the process to ensure operation with the lowest levels of NOX emissions.

One operating strategy to produce less NOX uses staged combustion, whereby a cooler fuel-rich combustion is established at the burner. Overfire air is then added higher in the furnace to complete the combustion. This results in less heat and oxygen passing through the burner, and less NOX produced. Advanced control strategies are often implemented to find the optimum air settings to minimize thermal NOX production.  Emerson’s Ovation and Delta V DCS systems both offer “Smart Process” control strategies for controlling NOX.

Another NOX reduction strategy is flue gas recirculation, where a certain amount of flue gas is mixed with the normal air used for combustion. An O2 probe mounted after this mixing valve can be used to control final O2 going to the burner, resulting in a cooler flame that produces less NOX.

Slag Prevention
Slag is molten ash that can attach to the boiler tubes, and acts as an insulator that decreases the heat transfer from the hot combustion gases to the water tubes. Flux sensors provide good information about soot and slag buildup, but close attention to combustion analyzers can provide another indication of slag formation.

Slag formation on boiler tubes

Fly ash fusion temperatures are usually affected by the amount of excess O2 in the flue gases, so many operators establish an O2 setpoint high enough to minimize slag formation. Slag can also be a potential safety hazard if a large piece breaks off falls to a lower section of the furnace.

Effective combustion flue gas analysis enables power plants to lower costs and minimize emissions by preventing slag and controlling the process to ensure operation with the lowest levels of NOX emissions.