Development of Supplementary Firing Burner for Gas Turbine Repowering System

The so-called industrial repowering system, which is to introduce gas turbine into the existing boiler - steam turbine system, is excellent in saving energy as well as cost effective due to minimum renovation of existing system. The main objective of this development is to get maximum firing capacity per turbine exhaust, to reduce NOx, to fire stably by exhaust of low oxygen concentration or fresh air interchangeably, and to fabricate the system at low cost. Our developed burner has stable firing range with exhaust whose 02 concentration is 14 - 21% and temperature is 350 - 600°C, and enables remaining O2 concentration to reduce to less than 3% (dry) without providing additional air. We divided the exhaust entering part of the burner into two stages and this burner can be also operated with fresh air at the regular inspection of the gas turbine. NOx of this burner is less than 50 ppm (O2 0%) a t 500°C of exhaust temperature and 15% of 02 concentration. It was proved that, NOx emission under the maximum load is in the linear correlation with the theoretical flame temperature. To reduce further NOx emission, steam injection and two-stage combustion are effective.