Coal water mixtures atomisation
The importance of atomisation in the Coal Water Mixtures (CWM) Combustion process is well known. Twin fluid atomisers can generate stable flames without auxiliary fuel, but complex correlations between spray quality, nozzle design and Coal Water Mixture properties are still a matter of discussion. The first objective of the present investigation was to consider how atomiser geometry (either fully internal or external-internal) influences the atomisation quality, during cold spray tests with one type of Coal Water Mixture. One of the tested nozzles was then selected to study the quality of Coal Water Sprays. For the first phase, four nozzles are tested : two of them are commercially available, and two are prototypes. They have been characterised in a cold atomisation test rig in terms of droplet size distribution as a function of the atomisation air flowrates and the CWM flowrates. It is confirmed that the quality of the spray is much more dependent on the air/CWM flow ratio than on the design of the atomiser. The investigation of the influence of the CWM properties leads to the conclusion that the most important parameters are the solid content of the mixture and the associated viscosity, the droplet size diminishing when the coal content is lower . Combustion tests with an upscaled version of one of the atomisers give results in agreement with the cold tests. Air consumption however was higher. Finally, this study has confirmed that the laser beam diffraction method can be used to determine droplet size, provided that the concentration in the jet is not too high.
Bibliographic Reference: EUR 12814 EN (1990) 67 pp., MF, ECU 4
Record Number: 199010761 / Last updated on: 1994-12-01
Original language: en
Available languages: en