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Catalytic combustion offers improved combustion stability extending the lean flame temperature limit to allow ultra-low NO x emissions. Instead of replacing the entire lean-premixed (LP) injector with a catalytic injector, advanced Rich Catalytic/Lean-burn (RCL ® ) technology is developed and integrated to replace only the pilot portion of the injector. The pre-reaction within the pilot provides enhanced reactivity reducing the need to use higher temperature flames to stabilize the combustor primary zone. This concept synergistically combines the best features of catalytic combustion and conventional aerodynamically stabilized combustion technology. The present paper discusses the development and engine testing of a set of Taurus 70 injectors equipped with RCL ® pilots for natural gas applications. Testing showed engine NO x emissions of ∼2.5 ppmv corrected to 15% O 2 were achieved at baseload conditions. Engine CO emissions were less than 2 ppm. Combustor acoustics were low (at or below 0.1 psi RMS) during testing. The RCL ® catalytic pilot supported the engine startup and shutdown process without major modification of existing engine controls. These initial results are promising. Further development work is needed to establish long term catalyst durability, engine transient behavior, and advancing the pilot technology to production status.

A Rich-Catalytic Lean-burn (RCL ® ) combustion system was developed for operation on natural gas, but also provides significant advantages for fuel-flexible operation on non-methane fuels. Most notably, fuel-rich operation limits the extent of catalyst-stage reaction based on available oxygen, regardless of the fuel's intrinsic reactivity on the catalyst. Thus, similar catalyst and reactor performance can be obtained for widely varying fuel types. In addition, catalytic pre-reaction extends the combustor's lean flammability limit for all fuels, allowing low-temperature combustion of both conventional and low-heating-value fuels, with concomitant low NO x emissions. This paper presents test results for RCL ® combustion with various fuel types, including gaseous, pre-vaporized liquid, and simulated low-Btu fuels. Although these fuels have widely varying properties, a single type of catalytic reactor was successfully tested for all of these fuels by modifying only the fuel delivery system upstream of the reactor. Test results show similar reactor performance for all fuels tested.

Many analyses have been completed on the operating characteristics of fuel processors as a function of fuel usage, power density and specific power as related to efficiency. In addition, it is widely recognized that depending on the fuel type, fuel processors will either be net producers or consumers of water. This has led to theoretical simulations to determine the maximum efficiency that can be achieved given a processor's overall water balance. Moreover, the effect of water for steam and autothermal reformers (ATR) has been investigated to gain an understanding of how it will be influenced given the net results of the system water balance. However, little attention has been given to the effect of water on the reactors downstream of the reformer. Furthermore, a simulation that incorporates the actual, not only theoretical, operation of the reactors coupled with the water balance issues has not been investigated until now. This paper will report on the effect of water on the operation of the CO clean-up train, including water–gas-shift (WGS) and preferential oxidation (PROX) reactors, and its influence on the overall efficiency of the processor system as compared to theoretical thermodynamic calculations. The comparison illustrates that a purely thermodynamic simulation can lead to a less efficient system design than could otherwise be possible once actual reactor performance is included.

This paper describes the design and testing of a catalytically-stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially-premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.Copyright © 2002 by ASME

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications. Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO 2 and H 2 O for all three catalysts. The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H 2 ) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior. High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.

The development of improved substrate properties for catalytic combustion has been an area of much interest in recent years. Towards this end, Precision Combustion Inc. has developed novel short channel length, high cell density substrates (trademarked Microlith ® ) and high surface area ceramic coatings for them. These substrates avoid substantial boundary layer buildup and greatly enhance heat and mass transfer rates in reactors. The high cell density of these substrates results in high amount of the catalyst per unit of reactor volume. In this paper we examine the performance of these substrates coated with precious metal catalysts for the catalytic combustion and reforming of methane. Under fuel-lean operating conditions the surface temperature of Pd-based catalyst supported on Microlith ® substrate and the temperature of the gas exiting the reactor remain stable at ∼800 ◦ C over a wide range of inlet conditions. This is attributed to combination of enhanced transport properties and characteristics of Pd–PdO transformation. Preheating of the gas mixture in the Microlith ® reactor was sufficient to stabilize a downstream premixed flame with NO x, CO, and UHC emissions in the single digit ppm range. Microlith ® substrates were also examined for partial oxidation of methane under fuel-rich conditions. The enhanced transport properties of the Microlith ® substrate allowed complete conversion of methane with surface temperature not exceeding material limits at 93% selectivity to partial oxidation products. High flow rate of reactants result in extremely high power densities and syngas output. The catalyst performance was observed to be stable over 500 h of operation. © 2003 Elsevier B.V. All rights reserved.

We report results from a lean burn ultra-low emission catalytic combustor. In a sub-scale rig, atmospheric testing with methane demonstrated NOx

PCI has developed and demonstrated its Rich Catalytic Lean-burn (RCL®) technology for industrial and utility gas turbines to meet DOE’s goals of low single digit emissions. The technology offers stable combustion with extended turndown allowing ultra-low emissions without the cost of exhaust after-treatment and further increasing overall efficiency (avoidance of after-treatment losses). The objective of the work was to develop and demonstrate emission benefits of the catalytic technology to meet strict emissions regulations. Two different applications of the RCL® concept were demonstrated: RCL® catalytic pilot and Full RCL®. The RCL® catalytic pilot was designed to replace the existing pilot (a typical source of high NOx production) in the existing Dry Low NOx (DLN) injector, providing benefit of catalytic combustion while minimizing engine modification. This report discusses the development and single injector and engine testing of a set of T70 injectors equipped with RCL® pilots for natural gas applications. The overall (catalytic pilot plus main injector) program NOx target of less than 5 ppm (corrected to 15% oxygen) was achieved in the T70 engine for the complete set of conditions with engine CO emissions less than 10 ppm. Combustor acoustics were low (at or below 0.1 psi RMS) during testing. Themore » RCL® catalytic pilot supported engine startup and shutdown process without major modification of existing engine controls. During high pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over a wide range of flame temperatures. In applications where lower NOx production is required (i.e. less than 3 ppm), in parallel, a Full RCL® combustor was developed that replaces the existing DLN injector providing potential for maximum emissions reduction. This concept was tested at industrial gas turbine conditions in a Solar Turbines, Incorporated high-pressure (17 atm.) combustion rig and in a modified Solar Turbines, Incorporated Saturn engine rig. High pressure single-injector rig and modified engine rig tests demonstrated NOx less than 2 ppm and CO less than 10 ppm over a wide flame temperature operating regime with low combustion noise ( 5000 hours) at simulated engine conditions (P=15 atm, Tin=400C/750F.). Cyclic tests simulating engine trips was also demonstrated for catalyst reliability. In addition to catalyst tests, substrate oxidation testing was also performed for downselected substrate candidates for over 25,000 hours. At the end of the program, an RCL® catalytic pilot system has been developed and demonstrated to produce NOx emissions of less than 3 ppm (corrected to 15% O2) for 100% and 50% load operation in a production engine operating on natural gas. In addition, a Full RCL® combustor has been designed and demonstrated less than 2 ppm NOx (with potential to achieve 1 ppm) in single injector and modified engine testing. The catalyst/substrate combination has been shown to be stable up to 5500 hrs in simulated engine conditions.« less

Lean premixed (LP) combustion is limited to a minimum NOx of 5–9 ppm due to flame stability. To improve flame stability and lower NOx, an advanced Rich Catalytic Lean-burn technology was developed and integrated to replace only the injector pilot with catalyst modules. This system focuses on replacing the highest temperature zone of the LP combustion system with a catalytic pilot (which can stabilize the main flame at reduced equivalence ratio) to reduce overall NOx emissions. This concept synergistically combines the best features of catalytic and aerodynamically stabilized combustion technologies. During Taurus 70 (T70) engine testing of a set of injectors equipped with catalyst modules for natural gas applications, emissions at baseload conditions were NOx of ∼ 2.5 ppmv and CO less than 2 ppm, both corrected to 15% O2 . Low single digit emissions were achieved from 50% to 100% load. Combustor acoustics were low (below 0.1 psi/690 Pa) during testing. Reactor catalyst temperature was within the design limit and no-preburner was required. The initial emissions results are promising providing an alternative to conventional LP technology for less than 5 ppm NOx systems. Further development work is needed to establish engine integration and long term catalyst durability before advancing to production.Copyright © 2009 by ASME

In order to meet DOE's goals of developing low-emissions coal-based power systems, PCI has further developed and adapted it's Rich-Catalytic Lean-burn (RCL{reg_sign}) catalytic reactor to a combustion system operating on syngas as a fuel. The technology offers ultra-low emissions without the cost of exhaust after-treatment, with high efficiency (avoidance of after-treatment losses and reduced diluent requirements), and with catalytically stabilized combustion which extends the lower Btu limit for syngas operation. Tests were performed in PCI's sub-scale high-pressure (10 atm) test rig, using a two-stage (catalytic then gas-phase) combustion process for syngas fuel. In this process, the first stage consists of a fuel-rich mixture reacting on a catalyst with final and excess combustion air used to cool the catalyst. The second stage is a gas-phase combustor, where the air used for cooling the catalyst mixes with the catalytic reactor effluent to provide for final gas-phase burnout and dilution to fuel-lean combustion products. During testing, operating with a simulated Tampa Electric's Polk Power Station syngas, the NOx emissions program goal of less than 0.03 lbs/MMBtu (6 ppm at 15% O{sub 2}) was met. NOx emissions were generally near 0.01 lbs/MMBtu (2 ppm at 15% O{sub 2}) (PCI's target) over a range on engine firing temperatures. In addition, low emissions were shown for alternative fuels including high hydrogen content refinery fuel gas and low BTU content Blast Furnace Gas (BFG). For the refinery fuel gas increased resistance to combustor flashback was achieved through preferential consumption of hydrogen in the catalytic bed. In the case of BFG, stable combustion for fuels as low as 88 BTU/ft{sup 3} was established and maintained without the need for using co-firing. This was achieved based on the upstream catalytic reaction delivering a hotter (and thus more reactive) product to the flame zone. The PCI catalytic reactor was also shown to be active in ammonia reduction in fuel allowing potential reductions in the burner NOx production. These reductions of NOx emissions and expanded alternative fuel capability make the rich catalytic combustor uniquely situated to provide reductions in capital costs through elimination of requirements for SCR, operating costs through reduction in need for NOx abating dilution, SCR operating costs, and need for co-firing fuels allowing use of lower value but more available fuels, and efficiency of an engine through reduction in dilution flows.

Use of catalytically coated short contact time (SCT) design approaches for application in mass transfer controlled reactors such as Auto Thermal Reformers (ATR’s) is an area of much recent interest. Precision Combustion, Inc. (PCI) has developed an efficient and compact ATR using ultra-short channel length, high cell density SCT substrates (Microlith ® ). PCI has also extended this Microlith technology to other fuel processor reactors that operate at lower temperatures and are not mass transfer limited. Namely, reactors for the Water Gas Shift (WGS) and Preferential Oxidation (PROX) of CO have been developed. Due to the higher surface area per unit volume of the Microlith substrate compared to conventional monoliths, size advantages have been observed for these reactions, which are more kinetically controlled. This results not only in shortened startup times and quick load following capability but also allows much smaller and lighter reactors – required attributes for automotive fuel cell applications. In this paper, experimental data on the performance of Microlith based ATR, WGSR and PROX reactors for reforming isooctane is presented. Transient and durability characteristics have also been included and compared to Department of Energy (DOE) targets.

A new Rich-Catalytic Lean-burn combustion concept (trademarked by PCI as RCL) was tested at industrial gas turbine conditions, in Solar Turbines’ high-pressure (17 atm) combustion rig and in a modified Solar Turbines engine, demonstrating ultra-low emissions of NOx < 2 ppm and CO < 10 ppm for natural gas fuel. For the single-injector rig tests, an RCL catalytic reactor replaced a single swirler/injector. NOx < 3 ppm and CO < 10 ppm were achieved over a 110 C operating range in flame temperature, including NOx < 1 ppm at about 1350 C flame temperature. Combustion noise was less than 0.15% peak-to-peak. Four RCL catalytic reactors were then installed in a modified (single can combustor) engine. NOx emissions averaged 2.1 ppm over the allowable operating range for this modified engine, with CO < 10 ppm and without combustion noise (less than 0.15% peak-to-peak).

Catalytic combustion is one means of meeting increasingly strict emissions requirements for ground-based gas turbine engines for power generation. In conventional homogeneous combustion, high flame temperatures and incomplete combustion lead to emissions of oxides of nitrogen (NOx) and carbon monoxide (CO), and in lean premixed systems unburned hydrocarbons (UHC). However, catalyst-assisted reaction upstream of a lean premixed homogeneous combustion zone can increase the fuel/air mixture reactivity sufficiently to provide low CO/UHC emissions. Additionally, catalytic combustion extends the lean limit of combustion, thereby minimizing NOx formation by lowering the adiabatic flame temperature. An overview of this technology is presented including discussion of the many materials science and catalyst challenges that catalytic combustion poses ranging from the need for high temperature materials to catalyst performance and endurance. Results of ongoing development efforts at Precision Combustion, Inc. (PCI) are presented including modeling studies and experimental results from both bench-scale and combustor-scale studies.

The provision of an ignition source in the central region of a liquid-fired combustor reduces the requirement for wide spray angles, rich primary zones, and their associated performance drawbacks such as high levels of soot and NOx formation and high liner wall temperatures. Various ignition devices have been considered for providing centrally located ignition sources. The current paper presents a study of one alternative concept — the integral catalytic torch ignitor/injector — as a means for providing both combustor light-off and enhanced flame stability in the combustor primary zone. An integral catalytic torch in a fuel injector offers the potential to significantly improve ignition arid flame stability and thus the opportunity to operate combustor primary zones at leaner conditions, which may improve emissions, pattern factor, and combustor liner durability. This paper presents computational and experimental results for a conventional liquid-fired combustor with the addition of a catalytic torch (replacing the pilot pressure atomizer) down the centerline of an air-blast fuel injector. The benefits of a lean primary zone with an integral catalytic torch/injector were investigated both computationally and experimentally by comparing combustor performance with standard and successively leaner primary zones. Pattern factor and emissions are compared with different primary zone jet configurations to observe if the central torch can enhance the operability of leaner primary zones in conventional combustor geometries. The experimental and computational results suggest that the integral catalytic torch can provide more than adequate ignition capabilities with improved combustor emissions when it is combined with a relatively lean operating primary zone.

To meet the increasingly strict automobile emissions requirements for conventional vehicles, considerable improvements in catalyst technology are required. It is now recognized that a primary challenge in meeting the ultra-low emissions vehicle standards (ULEV) for automobiles is in reducing cold-start emissions, and this generally requires a catalytic converter that has a rapid temperature response. Conventional converters (typically made from ceramic or metal monoliths) have a relatively slow temperature response due to their high thermal mass and limited heat transfer characteristics. We present details of a novel catalyst technology (Microlith™) that offers considerable advantages for this application because of greatly enhanced heat and mass transfer characteristics. Results of performance tests are also presented that demonstrate this catalyst's effectiveness. The effects of thermal aging on microstructure and catalyst performance are also discussed.

This paper has reviewed the background leading up to the development of the catalytic combustor, selected results of experimental studies, developments in modelling techniques, and some aspects of applications to gas turbines and furnaces. The future prospects of the technology are exciting. The design of catalytic combustors for gas turbines is underway. In fact, at least one U.S. manufacturer is believed to have a catalytic gas turbine ready for introduction in the near future. Retrofit designs for stationary gas turbines and for furnaces could be implemented readily. Significant economic benefits could stem from such applications. In addition, the demonstration that the catalytic combustor makes possible the burning of heavy oils for downhole generation of steam to increase oil production, is of importance beyond the merely economic potential. Thus, the catalytic combustor and other igneslytic burners are important developments not only because they permit complete combustion of fuels without significant NOx formation and because they make possible designs yielding reduced fuel consumption, but also because such combustors are serviceable in applications in which conventional combustors cannot be readily employed.

Catalysis and combustion have long been linked. In fact, the science of catalysis stems from Davy's discovery [1] that platinum wires could promote the flameless combustion of flammable fuel-air mixtures. Today, catalysis is a mainstay of our modern chemical industry. Oxidation catalysts are used not only for the complete oxidation of fuels to carbon dioxide and water, as in radiant catalytic tent heaters and fume abatement devices, but also for the selective partial oxidation of hydrocarbons or other “fuels” to produce basic chemicals such as ethylene oxide (from ethylene), terephthalic acid (from p-xylene), and nitric acid (from ammonia). However, despite the long-known capability of catalysts to oxidize hydrocarbons without significant production of carbon monoxide, soot, or thermal NOx, there seemed little possibility that catalytic oxidation reactors could ever displace conventional flame combustors as primary fuel combustors. This is because the volumetric heat release rates of conventional...

The theory of the Burnett method of measuring the compressibility of gases is discussed, and an analytical method of treating the data is presented. Determinations of the compressibility factor at 30°C for helium, nitrogen, and carbon dioxide show the convenience of the analysis and the precision that may be obtained by the method. Extension of the Burnett measurement to gas mixtures is also reported for some binary combinations of the three gases.

Catalysis and combustion have long been linked. In fact, the science of catalysis stems from Davy's discovery [1] that platinum wires could promote the flameless combustion of flammable fuel-air mixtures. Today, catalysis is a mainstay of our modern chemical industry. Oxidation catalysts are used not only for the complete oxidation of fuels to carbon dioxide and water, as in radiant catalytic tent heaters and fume abatement devices, but also for the selective partial oxidation of hydrocarbons or other “fuels” to produce basic chemicals such as ethylene oxide (from ethylene), terephthalic acid (from p-xylene), and nitric acid (from ammonia). However, despite the long-known capability of catalysts to oxidize hydrocarbons without significant production of carbon monoxide, soot, or thermal NOx, there seemed little possibility that catalytic oxidation reactors could ever displace conventional flame combustors as primary fuel combustors. This is because the volumetric heat release rates of conventional...