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NOx Control Technologies

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IFGR VS. Low NOx Burners

NOx Control Solution Comparison

In evaluating the differences in NOx control technologies, it is often overlooked to look at overall cost and performance side by side. The following chart demonstrates the differences between Induced Flue Gas Recirculation versus Low NOx Burners based on typical installations.

 

IFGR

LOW NOX BURNERS

COST

LOW

HIGH

PERFORMANCE

HIGH

LOW

INSTALLATION COST

INEXPENSIVE

EXPENSIVE

NOX REDUCTION CAP

HIGH

LOW

LOAD RATE

HIGH

LOWER

BURNER REQUIRED

SAME

LARGER

OVERALL NOX REDUCTION

UP TO 90%*

UP TO 50%

* IFGR Hybrids can emissions up to and above 90%


Problems with Low Nox Burners

There are many disadvantages to installing Low NOx Burners without additional or other technologies to enhance the performance of a beneficial NOx control project. The following points are important in understanding the disadvantages to LNB installtion.

1. LNBs control NOx emissions by providing air staging to create an initial, fuel-rich zone (partial combustion zone) followed by an air-rich zone to complete the combustion process. Some burner designs incorporate fuel staging that results in lower levels of NOx. Since NOx formation is a square root function of oxygen concentration, the reduction capability of stoichiometry-based technologies is limited.

2. Newer LNB designs such as ULNBs attempt to capture the concept of dilution by incorporating internal recirculation to obtain lower levels of NOx. Unfortunately, to obtain the desired levels of internal recirculation, higher fuel gas pressure and a larger burner throat are required. In retrofit applications, larger burners result in a need to rebuild furnace floor. Rebuilding furnace floor is both expensive and time consuming; and, increases the LNB installation cost exponentially!

3. Performance of ULNBs is also very sensitive to several factors including hydrogen in fuel gas, air preheat, particulates, liquid droplets and air leakage. Fuel gas containing hydrogen, air leakage into the furnace and air pre-heat result in increasing NOx emissions from ULNB. Changing the fuel gas system to remove hydrogen, particulates and droplets from fuel gas and sealing the furnace to ensure no air leakage also increases the cost of installing ULNB significantly. Eliminating air pre-heat for ULNB application not only increases installation costs, but also increases operating costs in terms of additional fuel cost.

4. Furthermore, at reduced loads, the internal recirculation rate is reduced due to lower fuel flow. This results in limiting the turndown ratio of the newer burner designs.

5. To avoid limitations of the newer burner design but to capture the concept of lower NOx reduction, some burner vendors offer external FGR along with LNB, but for a cost equivalent to that of SCR! Since the total installed cost of burner systems is an order of magnitude higher than FGR; and, since most of the NOx reduction in the newer burners is due to FGR, the most cost-effective alternative is the proven standalone FGR technology.


NOx control systems comparison


To find out more about the NOx Control benefits of IFGR systems and if our solution can meet your needs, please contact us. We will be glad to assess your requirements and present a NOx control evaluation for your application.