Bettina Paikert

Micro-engineered catalyst systems: ABB's advancement in structured catalytic packings

Abstract ABB has advanced catalysis with micro-engineered catalyst (MEC) systems by providing a uniquely small particle size on a formable catalyst support through the integration of catalysis and reaction engineering. A mechanically strong catalytic web of micro-fibers has been engineered and shaped utilizing both computational fluid dynamics (CFD) and cold flow experiments to optimize flow characteristics. This article discusses techniques used for the development of novel catalytic structured packings for catalytic distillation applications. CFD models (verified through experiments performed on small-sized structures) were shown to be of great utility in screening new structure ideas. Results will illustrate achievement of both high gas–liquid contacting and bulk mixing at low pressure drop with the potential to provide enhanced catalyst utilization by taking advantage of the intrinsic MEC properties, particularly its high porosity and exposed geometric fiber and catalyst surface area. This was shown by the successful testing of one of these catalyzed structures in the selective hydrogenation of C4 acetylenes.

Auto-Ignition in a Gas Turbine Burner at Elevated Temperature

Many facilities, e.g. reheat gas turbines or internal combustion engines, are operated with hydrocarbon fuels at elevated preheat temperatures such that conditions may be encountered where the flame is not stabilized by flame propagation, but by self-ignition. A model for turbulent reacting flow in this combustion regime has been developed, based on an ignition indicator representing the evolution of a pool of chemical intermediates. Interactions between turbulence and chemistry are taken into account using a new Monte-Carlo joint PDF approach. The joint PDF is not approximated by an analytical function, but by representative ensembles of particles, which are generated with a biased random number generator. Mean reaction rates are computed from the first and second moments — including co-variances — of those variables which describe the thermochemical state of the mixture. It is possible to calculate mean reaction rates in a pre-processing step and store them in a lookup-table table for use in a subsequent CFD simulation, making the approach very efficient. The model has been implemented in a CFD code and validated against an industrial gas turbine burner configuration. It has been found that the model describes the combustion process for a range of operating conditions with good accuracy.© 2003 ASME

Auto-Ignition and Heat Release in a Gas Turbine Burner at Elevated Temperature

This paper reports on the validation of an advanced model for ignition and heat release of natural gas at elevated pressures and temperatures. The model comprises two sub-models: one for the auto-ignition process and the other to consider heat release. To describe the ignition process efficiently the model uses an intermediate species to represent the evolution of the radical pool. Once the radical pool has reached a critical concentration, the subsequent heat release process starts. Rates for both processes are determined by use of detailed chemistry; hence the model can also take into account effects of higher hydro-carbons without use of a tuning parameter. Turbulence-chemistry interactions are considered with a new Monte-Carlo formulation for the joint probability distribution. This approach is based on the description of the mixture statistics via particle ensembles and not via a function as traditional presumed PDF (P robability D ensity F unction) methods do. The particle ensembles are generated for given means and (co-) variances of mixture fractions in a pre-processing step. To get information about the statistics in the CFD (C omputed F luid D ynamics) simulation, transport equations for means and variances are solved. Since the computation of turbulent mean reaction and heat release rates is performed in a pre-processing step, this approach is very efficient. Experimental results from a full-size burner of an industrial reheat gas turbine at atmospheric pressure was used as data for the model validation. It was found that this approach made possible the calculation of important physical characteristics, e.g. flame position and thickness for a wide range of operating conditions and burner geometries, with satisfying accuracy. Finally, it will be demonstrated how this numerical model is complementary to experimental development procedures and can be used as a burner design tool.Copyright

Development and Implementation of the Advanced Environmental Burner for the Alstom GT13E2

Increasing public awareness and more stringent legislation on pollutants drive gas turbine manufacturers to develop combustion systems with low NOx emissions. In combination with this demand, the gas turbines have to provide a broad range of operational flexibility to cover variations in gas composition and ambient conditions along with varying daily and seasonal energy demands and load profiles. This paper describes the development and implementation of the Alstom AEV (advanced environmental) burner, an evolution of the envorinmental (EV) burner. A continuous fuel supply to two fuel stages at any engine load simplifies the operation and provides a fast and reliable response of the combustion system during transient operation of the gas turbine. Increased turndown with low emissions is an additional advantage of the combustion system upgrade.

Development and Implementation of the AEV Burner for the Alstom GT13E2

Increasing public awareness and more stringent legislation on pollutants drive gas turbine manufacturers to develop combustion systems with low NOx emissions. In combination to this demand the gas turbines have to provide a broad range of operational flexibility to cover variations in gas composition and ambient conditions as well as varying daily and seasonal energy demands and load profiles.This paper describes the development and implementation of the Alstom AEV (Advanced EnVironmental) burner, an evolution of the EV. Continuous fuel supply to two fuel stages at any engine load simplifies the operation and provides a fast and reliable response of the combustion system during transient operation of the gas turbine. Increased turndown with low emissions is an additional advantage of the combustion system upgrade.© 2012 ASME