Innovative burner and combustion systems optimize combustion, improving safety, effectiveness and efficiency while lowering emissions
In burner and combustion operations, chemical processors must balance emissions and safety requirements with achieving optimal system performance in a cost-effective way. Further, many chemical facilities still rely on legacy infrastructure and aging equipment, which often lack the flexibility and instrumentation needed to run efficiently under today’s operating conditions. To overcome these issues, innovative burner and combustion technologies, as well as instrumentation and control solutions, are being developed to provide more efficient and effective combustion, while enabling lower emissions.
“The tightening of emissions regulations, particularly around both nitrogen oxides (NOx) and carbon monoxide (CO), continues to drive focused innovation in combustion system design,” says Gilles Theis, design manager EMEA, with Zeeco (Tulsa, Okla.; zeeco.com). “Where past efforts primarily addressed NOx, today’s compliance landscape increasingly requires low CO emissions under all operating conditions, including deep turndown scenarios.
“To meet these expectations, burner technologies have evolved to incorporate tighter excess air control, enhanced mixing and improved flame stability across the firing curve,” Theis continues. “Solutions that previously addressed emissions separately are now expected to balance both NOx and CO simultaneously.”
Modern combustion solutions
Burner and combustion system providers are working to develop modern solutions that safely address emissions, while also promoting combustion optimization.
“The main concerns are safety and reliability of the equipment, followed by operational flexibility, such as heater turndown capability and the ability to operate on a wide range of fuels,” says Erwin Platvoet, CTO with XRG Technologies (Tulsa, Okla.; xrgtechnologies.com). “Any attempt to optimize combustion systems for energy efficiency or emissions may jeopardize these primary goals.
“For example, the most reliable (and therefore safe) burners mix fuel and air intensely to form a hot and compact flame. These types of burners also generate the most NOx emissions,” Platvoet explains. “Any ‘optimization’ to lower NOx by fuel or air staging, flue gas recirculation and the like makes the flame more prone to flame interactions and impingement on coils, lowers the turndown capability of the burner and causes unburned fuel emissions at low firebox temperatures, lowers the flame stability and reduces the burner’s fuel flexibility.”
XRG’s novel approach to this challenge is its Xceed technology (Figure 1). “Xceed relies much less on the ability of the burner to meet all these goals, since a large fraction of the fuel is oxidized in a highly diluted manner in other areas of the combustion chamber without needing a stable flame,” says Platvoet. “The system distributes heat more uniformly at a lower firebox temperature while ensuring the entire chamber remains above the flammability limit. This makes the system independent of the fuel composition and eliminates basically all downsides of ultra-low-NOx burners, like flame impingement, while reducing NOx emissions to almost zero.”
FIGURE 1. Xceed technology from XRG Technologies can reduce NOx emissions by 50 to 80%, while also reducing firebox and tube temperatures
Xceed technology can reduce NOx emissions by 50 to 80%, while also reducing firebox and tube temperatures. The lower radiant temperatures allow higher firing rates (up to 40%) or higher air preheat temperatures, resulting in significant throughput or efficiency gains. When combined with flue gas recirculation (FGR), NOx emissions below 5 ppm are feasible, regardless of fuel type or composition.
Other combustion solution providers are also developing innovative solutions that help balance combustion efficiency with lower emission levels.
Mark Hannum, manager of innovation and laboratory with Fives North American Combustion (Cleveland, Ohio; fivesgroup.com) explains: “Most of the technologies for NOx reduction are understood, so it’s a matter of trying to find new ways to apply existing technologies or to combine multiple technologies to meet tighter emission standards and balance that with optimal combustion performance,” he says. “For example, mild combustion or flameless combustion allow you to get a dilute flame that is hot enough for process heating, but not hot enough to generate NOx. Lean premix and fuel-and-air staging are other technologies that can be combined to create a solution that provides the heat release and temperature profile necessary for optimal operations, but also allows low emissions of targeted pollutants.”
One such solution is Fives’ EcoFornax LE burner (Figure 2), which incorporates fuel staging, lean premix and dilute combustion mixing technologies to help reduce emissions and safely combust heat releases up to 250 MM Btu/h HHV. The burner reduces NOx to below 20 ppm without the use of FGR or below 8 ppm with FGR. The burner design and high-intensity, compact flame result in high reliability, enhanced process control and combustion efficiency, says Hannum.
FIGURE 2. Shown here is Fives’ EcoFornax LE burner firing an 80,000 bbl/day crude heater
“We’ve successfully installed the EcoFornax LE on process heaters that have very demanding NOx requirements,” says Hannum. “And it offers a lot of advantages in retrofit applications where the existing firebox can’t be changed.”
Fives also has plans to launch a new self-recuperative burner with integrated heat recovery, called the Tornado. Because the recuperator is built into the burner, it preheats combustion air, eliminating the need for a central recuperator and reducing fuel consumption, resulting in a lower carbon footprint. “In traditional technologies, using preheated air can negatively impact the combustion process and emissions, but the Tornado can handle preheated air to deliver better efficiency from the process and serve as a low NOx burner,” says Hannum. “It’s an interesting step toward decarbonization.”
Zeeco has also developed targeted burner platforms to meet combustion challenges. “Zeeco’s Zenith burner leverages lean-premix combustion principles, offering ultra-low NOx emissions while maintaining safe, stable operation, even at reduced loads. Designed specifically for process heating applications, Zenith allows users to push emission boundaries without compromising efficiency,” says Theis.
Focus on decarbonization
Because industrial operattions account for a large share of global CO 2 emissions, there is a need for industrial systems that aid reduction efforts. In response, innovative abatement solutions, and combustion solutions that support alternative fuels, are being devised.
“Decarbonization is playing an increasingly important role in the development of modern combustion technologies,” says Gerald Norz, senior business development manager with Dürr Systems, Inc. USA (Southfield, Mich.; durr.com). “We are seeing more customers transition to electric heating for their abatement equipment and many are replacing gas-fired burners with our electrically heated regenerative thermal oxidizers (RTOs).”
Dürr’s electric RTO, the Oxi.X RV (Figure 3), is a flameless air pollution control system that combines electrification with the use of renewable energy. “The Oxi.X RV is ideal for processes with multiple emission sources and low to moderate solvent concentrations. It offers a purification efficiency of 99.8%,” Norz explains.
FIGURE 3. Dürr’s electric RTO, the Oxi.X RV, is a flameless air pollution control system that combines electrification and the use of renewable energy
In the Oxi.X RV, the entire oxidation reaction used to clean the exhaust air occurs within the ceramic material, eliminating the open flame typically found in conventional combustion processes and preventing the formation of unwanted byproducts. Additionally, the ceramic heat bed stores the substantial energy generated during oxidation, allowing the process to become autothermal once the operating temperature is reached.
With a heat efficiency of 95 to 98%, no additional external heat is required, enabling energy-independent operation. The small amount of electricity needed to bring the system up to operating can be supplied by renewable resources. “This is a sustainable energy concept that helps companies reduce dependence on fossil fuels,” says Norz.
Recently, startup company, Revcoo (Venissieux, France; revcoo.com), developed a new post-combustion carbon capture technology, the CarbonCloud (Figure 4). The technology captures fumes produced by industrial facilities, separates the CO2 from the other gases by freezing it, then processes it into a liquid or gas form. The CO2 is then containerized and ready for storage or use, says Hugo Lucas, founder and president of Revcoo. “Users of CarbonCloud don’t have to change their process to meet decarbonization goals,” notes Lucas.
FIGURE 4. Revcoo’s CarbonCloud technology captures fumes produced by industrial facilities, separates the CO2 from the other gases by freezing it, then processes it into a liquid or gas form
The solution differs from traditional CO2 capture devices, which are based on chemical solvents. Instead, CarbonCloud captures CO2 through cryogenics, making it well suited to incompressible emissions that can’t be eliminated even when using clean fuels, as well as biogenic CO2 emissions from incinerators and biomass boilers. Currently, the equipment captures 95% of carbon emissions. “We are capable of 98% recovery, but this requires intensive liquid cryogenic consumption,” says Lucas. “Ninety-five percent is a good balance between cost and recovery.”
In operation, equipment is placed on the chimney of the facility and the machine uses a compressor to draw the flue gas into a chamber to remove the water, then it goes through the CarbonCloud, where the CO2 is separated from other gases by spraying liquid cryogenic gas through a nozzle, which transforms it from CO2 gas into a solid state, explains Lucas. “The solid CO2 is separated from the remaining gases with a cyclone. The solid CO2 can be transformed into a liquid state and sold to companies that need CO2 in their process or it can be sequestrated in a former oil well or injected into a saline aquifer.”
And, as alternative fuels are becoming an avenue for decarbonization, burner manufacturers are also developing solutions that offer fuel flexibility. For example, Zeeco’s FREE JET Gen 3 burner was developed to support the transition toward hydrogen and low-carbon fuels, says Theis. “Unlike traditional burners, this unit features a square tile design that facilitates tailored fuel distribution, improving flame anchoring and enabling smooth operation across a range of fuels, including 100% hydrogen. The burner incorporates internal flue gas recirculation to reduce flame temperatures and suppress NOx formation, meeting ultra-low NOx requirements without an external FGR system or complex control architectures.
“The design enables compliance with tightening emissions regulations, supports fuel flexibility and long maintenance intervals,” says Zeeco’s Theis. “It is especially attractive to sites looking to modernize combustion systems without introducing unnecessary complications and those planning long-term decarbonization strategies that rely on the next generation of fuels.”
And, as the chemical processing industry prepares for the use of hydrogen as a fuel, Nationwide Boiler (Fremont, Calif.; nationwideboiler.com) offers its CataStak selective catalytic reduction (SCR) technology (Figure 5) as it plays a crucial role in reducing greenhouse gas emissions by controlling the increased NOx levels associated with the use of hydrogen and hydrogen-blend fuels. While hydrogen combustion eliminates CO emissions — the primary contributor to greenhouse gases — it does produce more NOx when compared to firing on natural gas. The CataStak combats this increase in NOx, reducing output to acceptable levels.
FIGURE 5. Nationwide Boiler’s CataStak SCR system is suitable for a range of equipment applications, including boilers, gas turbines and fired heaters. The system’s single-reactor housing accommodates NOx reducing catalyst and/or CO oxidizing catalyst
Nationwide’s CataStak SCR system is suitable for a range of equipment applications, including boilers, gas turbines and fired heaters. The system’s single-reactor housing accommodates NOx reducing catalyst and/or CO oxidizing catalyst, providing a comprehensive solution for emission control. Multiple catalyst options are available, including honeycomb, plate type or pelletized and catalysts are tailored to specific chemical processing applications and equipment types to ensure high NOx or CO removal activity, low pressure drop, low sulfur dioxide (SO2) oxidation rate and durability.
Instrumentation and controls
New developments in controls and instrumentation, which were previously lacking in many combustion operations, are also helping to optimize combustion and include support for safety, reliability, emissions control and efficiency.
“We now use PLC-based combustion control systems with local touch screen HMIs for our rental fleet because it allows flexibility in both optimizing combustion control schemes and allowing operators to better understand and troubleshoot any operational issues,” says Jack Valentine, general manager of the controls division with Nationwide Boiler.
Nationwide Boiler’s Eagle BCS combustion control system offers both burner management and combustion control in an integrated Allen-Bradley CompactLogix PLC-based system with a PanelView touchscreen HMI. “This system is applicable for both boilers and process heater applications with a single burner FD fan-based equipment,” he says.
The control system was designed to provide an easier method of operation, so all air/fuel ratio curves are entered through a single HMI screen that displays the data required for burner tuning. This includes steam pressure (or outlet temperature), drum level and percent oxygen. “The most efficient system is a fully metered system that meters the fuel-to-air ratio to optimize flue gases by oxygen or a combination of oxygen and combustibles,” says Valentine. “With the advent of better controls, this has become a routine way to optimize combustion and help control fuel consumption and costs.”
Nationwide Boiler also offers its Eagle Eye remote monitoring system for 24/7 equipment monitoring, trending and fault notification. The ability to remotely monitor combustion systems provides real-time insight into critical data, allowing users to make informed decisions and optimize operations from any location; fine tune equipment performance to ensure maximum efficiency and energy savings; and ensure that safety protocols are upheld. Data and trending can also be used for predictive maintenance planning, promoting reliability.
And, while previous instrumentation for combustion systems was difficult to install, commission and maintain, making optimization a challenge, Emerson (Shakopee, Minn.; emerson.com) has recently addressed many of these issues with the release of the Rosemount CX2100 In Situ Oxygen Analyzer (Figure 6), according to Peyton Munoz, senior product management engineer with Emerson.
FIGURE 6. Emerson’s Rosemount CX2100 In Situ Oxygen Analyzer streamlines maintenance and lowers total cost of ownership
“Combustion and flue gas analysis has been used by operators for decades as a method of optimizing air/fuel ratio. By measuring the amount of excess oxygen in the flue gases from combustion, plants can operate at the best heat rate efficiency, lowest NOx emissions and generate the lowest amount of greenhouse gas,” explains Munoz. “Accurate oxygen readings can be used to optimize the combustion process for boilers and fired process heat furnaces throughout the plant.
“Optimizing processes in this way leads to cost savings from decreased energy and fuel use, plus it helps maximize product output,” she says. “And importantly, it enhances safety via autocalibration and autocalibration check features that regularly measure analyzer accuracy to ensure the analyzer stays within calibration limits. Safety is further improved by a flame safety interlock, which automatically turns off the probe’s heater when a flameout is detected.”
“In addition to adding smarter technologies, implementing solutions that enhance reliability, simplify operation and deliver measurable performance gains with minimal impact on operator workload are key to optimization,” says Theis from Zeeco. “In many cases, optimization involves retrofitting or replacing aging burners with modern designs that support fuel flexibility, tighter control and more responsive diagnostics — all while ensuring environmental compliance.”
Joy LePree