Italy (site survey)
Edipower recently commissioned RJM to carry out an Air Distribution Analysis (ADA) programme at its power station at Brindisi in southern Italy to optimise performance and efficiency at minimum loads.
The relationship with Edipower was established in 2006 when RJM carried out an investigative survey of the combustion performance of Units 1 - 4 at its 160MWe oil-fired station at San Filippo power station on Sicily. The objective of the survey was to identify a range of possible technical solutions to reduce NOx levels in the flue gases at the boiler outlet and its successful conclusion led to RJM being hired to carry out this additional survey at Brindisi.
Edipower's power station at Brindisi currently has two of the original four units in operation, each one being capable of generating 320MWe at full load. It is of strategic importance to Edipower to be able to run these units efficiently at low load on coal.
Earlier in 2010, RJM performed a Minimum Load Reduction Study to evaluate reducing the minimum load (on coal only) from 155MWe (net) to 135MWe (net). Several recommendations were made as an outcome of this study. A new set of operating parameters were recommended to Edipower and, in addition, it was proposed that an airflow balancing programme be carried out. These recommendations will enable the plant to operate safely and efficiently on coal at the reduced minimum load of 135MWe - without impinging on burner or furnace stability.
Using a hot wire anemometer, measurements were taken at 24 points around the circumference of each burner throat.
This data was collected using RJM's in-house developed software, which allows for several different 2D & 3D graphical charts to be created, allowing for a clear, visual understanding of air flow distribution within the furnace. Some examples of which are shown below.
The position of each burner is entered into RJM's software along with the radius of the measurent point. The chart above shows the velocity profiles produced from each burner within the windbox, this allows us to see if there are any areas that have low or high flows.
The above chart is basically the same as above but in blanket format.
The above topographical chart shows the position of the burners relative to the windbox. The contour lines are deduced from RJM's results to create a velocity map of the windbox. This allows us to see how the high or low airflows track through the windbox and enter into each burner. This chart also allows us to see where vorticies are located (see red arrow), these will need to be destroyed to allow improved airflow to this region.
Using this data, RJM then adjusted the register door positions to balance the airflow to the burner. Caution was used in making these adjustments as changes to the amount by which the register doors were opened or closed, also changed the amount of swirl, i.e. the ratio of axial to tangential momentum.
Care was taken to ensure the doors were not closed too much (creating a high swirl number and pulling the fire back into the throat), or too open (producing a low swirl number and a loose unstable flame).
Getting the register door positions just right had the effect of dramatically improving airflow distribution across the boiler, yielding improvements of greater than 50%.
In addition to improving burner and furnace stability at minimum load, a 29% reduction in Carbon in Ash has also been achieved, meaning that the units are burning their fuel more efficiently. An additional benefit yielded by low CiA is that if it can be reduced to below 7%, it can be sold as a valuable raw material for use in cement manufacturing (and thus become an additional revenue stream for the power plant), rather than having to be disposed of in landfill, at a cost of around 60 Euros per tonne.
Read more about RJM's Air flow balancing capability here.