Ralph A. Dalla Betta

Catalytic combustion gas turbine systems: the preferred technology for low emissions electric power production and co-generation

The operating requirements for practical catalytic combustion systems are presented. Catalytic materials for methane combustion are then reviewed in light of these operating requirements. Measured catalytic rates for methane oxidization for a number of active metal and oxide catalyst systems are reported and compared. The precious metals, particularly Pd, are most active. The oxides can exhibit high surface areas but in all cases have a much lower areal activity resulting in a substantially lower weight specific activity. Data on the thermal stability and volatility of both support and active components are presented and discussed in terms of the required operating temperatures. It is concluded that at the required operating temperature for modern gas turbines, most catalyst systems would not have sufficient stability and life. An alternative approach is to limit the catalyst temperature and to react a portion of the fuel after the catalyst. This process has substantial advantages. This latter system will be described and the important catalyst performance characteristics discussed. Test results demonstrate NOx levels below 2 ppm even at combustor outlet temperatures as high as 1500°C.

Application of catalytic combustion to a 1.5 MW industrial gas turbine

Abstract A catalytic combustor is described for a 1.5xa0MW gas turbine engine. The catalyst temperature is limited and the high combustor outlet temperatures required by the turbine are generated downstream of the catalyst. The combustor design places a low NO x preburner upstream of the catalyst and uses this preburner to achieve optimum catalyst operation by providing the desired catalyst inlet temperature. The combustor system employs the catalyst during engine acceleration and loading. The catalyst design has been tested on a sub-scale rig under full pressure and flow conditions simulating turbine operation over the entire operating range including acceleration and loading. The design should achieve emissions at full load operation of x and

Catalytic combustion technology to achieve ultra low NOx, emissions: Catalyst design and performance characteristics

Abstract A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. Catalysts have been demonstrated that operate at inlet temperatures as low as 320°C at 11 atm total pressure and conditions typical of high performance industrial gas turbines. The ignition temperature is shown to correlate with the specific catalytic activity of the washcoat layer over a rather broad range of activities. A reaction model has been developed that can predict ignition behavior from the measured catalytic activity.

Achieving ultra low emissions in a commercial 1.4 MW gas turbine utilizing catalytic combustion

Abstract The drive to achieve low emissions from gas turbines has been an ongoing challenge for over 30 years with the reduction of NO x levels representing the most difficult issue. Catalytic combustion represents the technological approach that can achieve the lowest level of NO x , in the range of 3xa0ppm and lower depending on the combustion system design. The program to develop a catalytic combustion technology that can achieve ultra low levels of NO x , CO and unburned hydrocarbons (UHCs), applicable to a wide range of gas turbine systems and with long term durability is described. The technological approach is to combust only a portion of the fuel within the catalyst with the remaining fuel combusted downstream of the catalyst allowing the catalyst to operate at a low temperature and thus obtaining good long term catalyst durability. This catalytic combustion approach is then applied to a 1.4xa0MW gas turbine to demonstrate feasibility and to obtain real field experience and to identify issues and areas needing further work. The success of this demonstration lead to a commercial combustor design. This combustor and the final commercial package is described and the performance specifications discussed.

Application of Catalytic Combustion Technology to Industrial Gas Turbines for Ultra-Low NOx Emissions

An operating cycle had been developed for a catalytic combustion system applied to the Allison 501-KB7 engine. This cycle used overboard bleed of diffuser air to maintain a high fuel/air ratio at the catalyst and thus achieve a high combustor outlet temperature with attendant low CO and UHC emissions. For the design point of this engine, the emissions measured at full pressure and temperature in a subscale catalyst test rig were <1 ppm NOx and <2 ppm CO and UHC. Tests over the full operating cycle showed that the catalytic combustor system would achieve low emissions from 20 to 100% load.The use of catalytic combustion on a high efficiency gas turbine engine design was also evaluated. Pressures up to 20 atm and combustor outlet temperatures up to 1500°C (2730°F) were demonstrated with NOx emissions <2.2 ppm and CO and UHC <2 ppm. These results show that catalytic combustion is a viable technology for application to a high pressure, high temperature industrial gas turbine engine design.© 1995 ASME

Development of a catalytic combustor for a heavy-duty utility gas turbine

Abstract Catalytic combustion is an attractive technology for gas turbine applications where ultra-low emission levels are required. Recent tests of a catalytic reactor in a full scale combustor have demonstrated emissions of 3.3xa0ppm NO x , 2.0xa0ppm CO, and 0.0xa0ppm UHC. The catalyst system is designed to only convert about half of the natural gas fuel within the catalyst itself, thus limiting the catalyst temperature to a level that is viable for long-term use. The remainder of the combustion occurs downstream from the catalyst to generate the required inlet temperature to the turbine. Catalyst development is typically done using subscale prototypes in a reactor system designed to simulate the conditions of the full scale application. The validity of such an approach is best determined experimentally by comparing catalyst performance at the two size scales under equivalent reaction conditions. Such a comparison has recently been achieved for catalysts differing in volume by two orders of magnitude. The performance of the full scale catalyst was similar to that of the subscale unit in both emission levels and internal temperatures. This comparison lends credibility to the use of subscale reactors in developing catalytic combustors for gas turbines.