Hasan Karim

Complete and partial catalytic oxidation of methane over substrates with enhanced transport properties

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.

Status of Catalytic Combustion R&D for the Department of Energy Advanced Turbine Systems Program

This paper discusses some of the advanced concepts and research and development associated with implementing catalytic combustion to achieve ultra-low-NO x emissions in the next generation of land-based gas turbine engines. In particular, the paper presents current development status and design challenges being addressed by Siemens Westinghouse Power Corp. for large industrial engines (>200 MW) and by Solar Turbines for smaller engines (<20 MW) as part of the U.S. Department of Energys (DOE) Advanced Turbine Systems (ATS) program. Operational issues in implementing catalytic combustion and the current needs for research in catalyst durability and operability are also discussed. This paper indicates how recent advances in reactor design and catalytic coatings have made catalytic combustion a viable technology for advanced turbine engines and how further research and development may improve catalytic combustion systems to better meet the durability and operability challenges presented by the high-efficiency, ultra-low emissions ATS program goals.

Advanced technology catalytic combustor for high temperature ground power gas turbine applications

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

Rapid Thermal Response Catalyst for Treatment of Automotive Exhaust

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. The authors present details of a novel catalyst technology (Microlith{trademark}) 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.

Catalytic Combustion Technology Development for Gas Turbine Engine Applications

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.

Computational and Experimental Evaluation of Integral Catalytic Ignitor/Injector for Gas Turbine Applications

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.Copyright