(419f) Flexible Burner Concept for Oxyfuel Combustion

Recently, CO₂ emission reduction or removal from coal fired power plants has become the highest priority in measures to combat global warming. Among researched technologies aiming at CO₂ capture in the power plant industry, the oxy-fuel process is nowadays of particular interest. In the oxy-fuel technology the combustion of fuel is performed with pure oxygen and recycled flue gas instead of air; the firing system and in particular the burner is highly affected by the modified combustion process and needs special attention. For testing purposes related to the oxy-fuel combustion process, a highly flexible firing system and burner concept is needed to cover the broad range of test conditions.

For the burner concept and the firing system one need to consider the following aspects:

·         Ignition;

·         Flame stability;

·         Air operation mode;

·         Oxyfuel operation modes

o   Direct oxygen injection mode

o   Pre-mixed oxygen mode

o   Individual oxygen enrichment mode ;

·         Switch from air to oxy-fuel mode and vice versa; and

·         Several burner compartments and swirl implementation for burner tuning. 

All these above mentioned aspects were considered by Alstom Power Systems GmbH in the design of the 30 MWth oxy-fuel burner of the Vattenfall's Schwarze Pumpe pilot steam generator.

The downscale of the 30 MWth oxy-fuel burner to a size of 500kWth and the adaptation to boundary conditions of the IFK's 500kWth test rig as well as the testing of the burner

have been performed within the framework of the European Commission funded project ?OXYBURNER?.

A new oxy-fuel infrastructure for testing oxy-fuel burners was designed and installed at the Institute of Combustion Power Plant Technology (IFK), University of Stuttgart. The downscaling task of the oxy-fuel burner and the adaptation to the 500kWth test rig's boundary conditions was supported by Alstom Power Systems GmbH. IFK has built, installed, and extensively tested the burner.  Also, IFK produced experimental data for mathematic modeling studies.

     Fig.1: IFK 500kWth test facility                                                   Fig.2: Implemented new burner

The experiments were conducted with pre-dried lignite. Different set-ups were tested. The burner design offers the possibility to inject the necessary oxygen directly through the burner into the combustion zone. This allows varying the combustion conditions in a very wide range, up to the case where 100 % O₂ is directly injected.

During the experiments detailed in-flame measurements along the combustion chamber were done in order to characterize the flames resulting from different set-ups. The continuous monitoring of the gas emissions is a standard procedure. The experimental investigation supported by mathematical modelling studies does not only provide further back-up on what has already been achieved for optimisation of oxy-fuel combustion processes but it also provides valuable information on operational experience with different burner configurations that will finally end up in the concept and design of an advanced low NOx oxy-fuel burner.

The results from testing as well as from mathematical CFD modeling will be presented during the 2010 AIChE Annual Meeting.