Joel Meier Haynes

Evaluation of Emissions Performance of Existing Combustion Technologies for Syngas Combustion

Syngas is composed of mixtures of H2 and CO and inerts such as N2 , steam and CO2 . The composition of syngas derived from oxygen and air-blown gasifiers is discussed. The low exhaust gaseous emissions potential of diffusion, lean premixed and rich catalytic combustors with representative oxygen and air-blown syngas fuels are evaluated. The evaluation is performed using network of well-stirred reactor models. The parameters of the reactor models are carefully chosen so as to represent the flow-physics in the combustors. Predictions of NO and CO emissions for the different combustion modes are presented for the representative syngas fuels. The calculations are performed with combustor pressures and inlet temperatures typical of heavy-duty gas turbine power generation plants. The effect of combustor exit temperature, added diluents and the composition of the fuel on NO and CO emissions are evaluated for the different combustion technologies. The sensitivity of the emissions to reactor parameters is also explored.Copyright

Fuel-Flexible Combustion System for Co-production Plant Applications

Future high-efficiency, low-emission generation plants that produce electric power, transportation fuels, and/or chemicals from fossil fuel feed stocks require a new class of fuel-flexible combustors. In this program, a validated combustor approach was developed which enables single-digit NO{sub x} operation for a future generation plants with low-Btu off gas and allows the flexibility of process-independent backup with natural gas. This combustion technology overcomes the limitations of current syngas gas turbine combustion systems, which are designed on a site-by-site basis, and enable improved future co-generation plant designs. In this capacity, the fuel-flexible combustor enhances the efficiency and productivity of future co-production plants. In task 2, a summary of market requested fuel gas compositions was created and the syngas fuel space was characterized. Additionally, a technology matrix and chemical kinetic models were used to evaluate various combustion technologies and to select two combustor concepts. In task 4 systems analysis of a co-production plant in conjunction with chemical kinetic analysis was performed to determine the desired combustor operating conditions for the burner concepts. Task 5 discusses the experimental evaluation of three syngas capable combustor designs. The hybrid combustor, Prototype-1 utilized a diffusion flame approach for syngas fuels with a lean premixed swirl concept for natural gas fuels for both syngas and natural gas fuels at FA+e gas turbine conditions. The hybrid nozzle was sized to accommodate syngas fuels ranging from {approx}100 to 280 btu/scf and with a diffusion tip geometry optimized for Early Entry Co-generation Plant (EECP) fuel compositions. The swozzle concept utilized existing GE DLN design methodologies to eliminate flow separation and enhance fuel-air mixing. With changing business priorities, a fully premixed natural gas & syngas nozzle, Protoytpe-1N, was also developed later in the program. It did not have the diluent requirements of Prototype-1 and was demonstrated at targeted gas turbine conditions. The TVC combustor, Prototype-2, premixes the syngas with air for low emission performance. The combustor was designed for operation with syngas and no additional diluents. The combustor was successfully operated at targeted gas turbine conditions. Another goal of the program was to advance the status of development tools for syngas systems. In Task 3 a syngas flame evaluation facility was developed. Fundamental data on syngas flame speeds and flame strain were obtained at pressure for a wide range of syngas fuels with preheated air. Several promising reduced order kinetic mechanisms were compared with the results from the evaluation facility. The mechanism with the best agreement was selected for application to syngas combustor modeling studies in Task 6. Prototype-1 was modeled using an advanced LES combustion code. The tools and combustor technology development culminate in a full-scale demonstration of the most promising technology in Task 8. The combustor was operated at engine conditions and evaluated against the various engine performance requirements.

Dynamics Suppression in Liquid-Fueled Combustors Using Fuel Modulation

In the present work, an atmospheric pressure combustor using a modern aviation gas turbine fuel nozzle was used to demonstrate active combustion control. The combustor exhibited a low-frequency dynamics mode under fuel-rich conditions. A fast-response fuel valve was adapted as an in-line valve upstream of the nozzle for fuel modulation. Large fuel modulation amplitudes were achieved with the combination of the valve and the engine nozzle at frequencies exceeding 200 Hz. Open-loop flame response to fuel modulation was first examined when the instability mode was absent; for a range of inlet air temperatures, fuel flow rates, and combustor pressure drops. Simple open-loop control at discrete off-resonance frequencies was found ineffective in suppressing the instability mode. An advanced, fast algorithm was developed to enable closed-loop control. In this scheme, the entire fuel supply to the combustor was modulated with the control valve and injected through the fuel nozzle. The control algorithm commanded the fuel injector to produce a steady fuel flow, when the combustion was stable, or to modulate the fuel when the level of pressure oscillations in the combustion chamber became unacceptable. With an optimized control algorithm, an 88% reduction in the amplitude of the low-frequency dynamics mode was achieved.Copyright

Trapped Vortex Combustor Performance for Heavy-Duty Gas Turbines

The application of the trapped vortex combustor (TVC) concept to heavy-duty gas turbine conditions has been explored. Combustor stability, lean blow out, and emission performance requirements limit design options for conventional lean premixed combustors. The TVC concept has demonstrated reduced emissions and high turndown with liquid fuels and could overcome existing lean premixed performance constraints as well. The present study examines premixed injection of natural gas into the TVC at heavy-duty gas turbine conditions. The emission performance is measured over a range of operating conditions. The combustor turndown and dynamics performance are also presented. To forecast the performance potential of the TVC combustor a chemical reactor network model was developed. The model was anchored with experimental data and implemented in the prediction of TVC combustor emissions and turndown performance. The reactor model confirms that NOx reduction greater than 60% is possible using a trapped vortex combustor (TVC).Copyright