Low-NOx Burners

Case Stories

The La Spezia low NOx retrofit

In 2000 BWE was rewarded an order to retrofit a 600 MWe unit at the La Spezia power plant in Italy. The main objective in the project has been to implement primary Low NOx measures on the plant to make it complaint with future EU emission limits. Additionally the plant was optimised in respect of efficiency in a parallel program, aiming at improving the boiler parameter performance.

The plant has been equipped with the advanced Wide Range (WR) combustion system from BWE that enables firing of a wide range of coal fuels as well as natural gas. The system is composed of WR burners, an OFA system, dynamic classifiers and an optimised fuel distribution system. Burner number and horizontal- and vertical arrangement pitch has been changed in order to optimise furnace heat parameters.

Coal fuels are ranging from very low reactive South African coals up to subituminus normal coals. The advantages achieved by the retrofit has been:

• NOx below 550 mg/Nm3
• UBC levels of about 3%
• Improved fuel flexibility
• Improved unit efficiency

The boiler heat balances has been modelled and optimised whereby the attemporator operation has been minimised, and hence the efficiency improved, alterations on the reheater surfaces being the major part of this modification were introduced during the combustion retrofit outage.