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Show 3. THE TEA BURNERS The ~dea to develop ,a ',Low-NOx" burner originated in 1989 essentially to meet new directions r~gardmg pollutant ~mlsslons, since at that time there was no burner with Low-NOx production for 011 and gas of consoltdated and recognized technology on the international market. ~he researchers of the Thermal Research Centre of Pisa and the designers of Ansaldo, the Italian boller manufacturer, set up a new burner which employs the stage-combustion technique. The burner has been named T.E.A., acronym ofTriflusso Enel-Ansaldo (Enel- Ansaldo Threeflow). The burner geometry is able to form volumes with different stoichiometries: a fuel rich volume inside the flame, and external zones where the nitric oxides react with the radicals formed in the fuel rich zone and are reduced to molecular nitrogen. The air is subdivided into three streams: the primary air, swirled by a row of guide vanes, stabilizes the flame close by the burner. The secondary and tertiary flows are controlled through registers in order to ensure a variable ratio between the two momenta, guaranteeing control of the mixture between secondary air and fuel, as well as speeding up the tertiary flow in order to create a wide area of internal recirculation. The TEA performances were compared with those of an axial burner of consolidated technology: the NOx emissions were about 500/0 of the emissions of the referred to burner. At the moment the burner is also available in the version 'Mark 2", characterized by a simpler geometry, by lower pressure drop and by even more limited NOx emissions (65% reduction). To complete the range of products to be offered on the national and foreign market, the version TEA-C has recently been developed for coal. The burner structure is derived from version Mark 2 for oil and gas. This will shortly be installed on the 240 MW e Unit #3 of ENEL Sulcis power plant, and later on the 320 MWe Unit #4 at the Vado Ligure power plant. 4. DESIGN APPROACH AND PROCEDURE The necessity to develop this new family of burners has led to the definition of suitable instruments for designing, realizing and testing of these products, within the Thermal Research Centre. At the beginning, test rigs for aerodynamic characterization in cold conditions and furnaces for studying and testing the innovative burners under development were constructed. At the same time, advanced measurement techniques, especially optical techniques, which allowed a considerable improvement in the experimentation, were developed. Together with these methodologies, the use of powerful calculation codes for the numerical simulation of the burner behaviour, both in isothermal and reactive conditions, has recently become more extensive. For the development of a burner, a work scheme in which experimental activities, diagnostics and mathematical construction of models take part in an integrated way, has been consolidated. To this extent the fundamental conditions are: the ability to correctly scale the combustion systems, the availability to carry out meaningful measures in very different scale equipment and the capacity to model the processes in a suitable way. The followino activities are carried out at the Thermal Research Centre: o • Mathematical modelling. • Aerodynamics in reduced scale. • Atomization tests (oil). • Small scale combustion tests. • Full scale combustion tests. 2 |
