Ongoing Development of a Low Emission Industrial Gas Turbine Combustion Chamber

Abstract

Experiments were performed in laboratory-and full-scale combustors to test the feasibility of meeting proposed EPA emission standards. It was found that by uniformly mixing gaseous fuel and primary zone air prior to combustion and burning fuel leanly (equivalence ratio <1.0), it was possible to meet the proposed emission standards in an industrial gas turbine. The characteristic narrow range of flame stability obtained with lean premix combustion necessitated the use of fuel staging or variable geometry to handle the operational range of the engine. Fuel staging was selected for its relative simplicity. Consequently, EPA proposed emission standards were met only over a narrow range covering the engine operation at and near the design point. Experiments on small scale models of various sizes operated with gaseous and liquid fuels showed that, contrary to expectation, NOx production from a lean premix combustion system is independent of the system pressure in the pressure range investigated (1 atm to 16 atm). The desirability of high combustor inlet temperature and pressure for premixing was indicated. Despite the complexities of premixing fuel and air, such a combustion system, in addition to meeting the proposed emission standards, offers advantages such as easing of combustor wall cooling problems, improved combustor exit temperature distribution, and freedom from exhaust and primary zone smoke.

Design and Testing of an Ultra-Low NOx Gas Turbine Combustor

“…The effectiveness of lean premixed combustion in reducing NOx emissions is well documented [3][4][5]. Typical lean premixed burner emissions are shown in Figure 1.…”

Ongoing Development of a Low Emission Axisymmetric Annular Vortex Combustor for an Industrial Gas Turbine

“…Test results, described in Ref. (1), clearly showed the dominance of mixing control on a small premix vortex combustor. NO x emissions, combustion efficiency, and flame stability were all found to be little influenced by significant differences in air pressure.…”

“…A fixed geometry lean premix combustor has insufficient lean flame stability limit to provide a satisfactory range of operation in an industrial gas turbine (1). Therefore, in addition to a premix set of fuel injectors for design point conditions, a second set of fuel injectors, producing a diffusion flame, is required for starting and part load operation.…”

“…Solar has conducted research and development on various means of reducing turbine exhaust emissions, including premix lean combustion. Previous work on lean combustion, on the recuperated Centaur 2600 kW gas turbine, using a can combustor with a vortex stabilized flame without jet assisted recirculation has been reported (1). This paper describes similar techniques applied to the Mars 7500 kW engine (2).…”

Low Btu Coal Gas Combustion in High Temperature Turbines

“…The conversion of atmospheric nitrogen to oxides of nitrogen in the combustor is not an emissions problem when burning very low Btu coal gases even in high temperature turbines because the adiabatic flame temperature is below 1800°C (4,7,8,9,10,11). The Zeldovich mechanism (12) accounts for the important temperature dependence of this reaction.…”