Integrating Gas Turbines with Cracking Heaters - Impact on Emissions and Energy Efficiency

Abstract

Turbine Exhaust Gas (TEG) contains high levels of oxygen, typically 15 vol. percent, due to gas turbine blade material temperature limits. As such it can be used as an oxidant for combustion in cracking furnaces and reformers. Its high temperature and flow rate results in a significant reduction of fuel consumption of the furnaces while increasing the high pressure steam production. The resulting high combined energy efficiency makes this an attractive option when energy costs are high. This paper will discuss some of the theoretical considerations of NOx formation, and correlate differences between air and TEG firing with adiabatic flame temperature and oxygen concentration. In order to validate emissions predictions an industrial-scale test was conducted at the John Zink Test Facility with two floor burners operating with TEG. The results were compared with ambient air tests and show good agreement with the predictions. They also give some insight if and when reburn of NO is significant.