THE OBJECT OF THIS WORK IS TO IMPROVE ATOMISATION TECHNIQUES FOR SLURRIES AND, BY A BETTER UNDERSTANDING OF PARTICLE BEHAVIOUR AND HEAT TRANSFER IN THE NEAR FIELD MIXING REGION LOCAL TO THE ATOMISER TIP, TO LEAD TO THE DEVELOPMENT OF A RANGE OF BURNERS THAT REQUIRE LESS SUPPORT FUEL AND THUS EXTEND THE POSSIBILITY FOR SUCCESSFUL OIL FIRED BOILER CONVERSIONS.
Coal water slurry burners have achieved only a limited success in small applications because of problems caused by lower flame temperatures, especially at turndown, where a supplementary fuel may be required to ensure continuous combustion. Small industrial and shell boilers are the most appropriate size for conversion from oil to coal water slurry firing. It was considered that, by using modern atomiser development and measurement techniques together with advances in the field of computational fluid dynamics, improvements could be made if a better understanding of the atomization of, and heat transfer to, the fuel particles in the region close to the burner tip was achieved. A programme of work has been completed which used both analytical and experimental techniques to examine atomiser performance, the interaction of fuel particles which takes into account turbulence and mixing in the combustion air stream and the heat transfer in the fuel dry out region. A twin register burner design was successfully fired, using a coal water mixture fuel, in a test facility which represented the typical combustion chamber size found in small industrial and shell boilers.
An atomiser has been developed to fire coal water mixtures in the form of a slurry. This can be used as a replacement for fuel oil.
Development of the atomiser and aerodynamic design using a combination of modern physical modelling and mathematical modelling techniques has led to the the design of a coal water slurry burner which has fired successfully on a commercial fuel without the need for gas support. The combustion performance was satisfactory with emissions lower than required by current European Economic Community (EEC) legislation. It was hoped to evaluate this burner on a wider range of fuels but these have not been made commercially available as a result of the relatively low oil prices.
A prototype was made available on 06/22/92
THE PROJECT IS DESIGNED TO IMPROVE THE UTILIZATION OF HEAT FOR PARTICLE DRYOUT IN THE NEAR FIELD REGION LOCAL TO THE BURNER NOZZLE. THIS IS NECESSARY BECAUSE PRESENT SYSTEMS CAN REQUIRE UNECONOMIC QUANTITIES OF SUPPLEMENTARY FUEL OR ATOMISING STEAM TO MAINTAIN FLAME STABILITY ESPECIALLY DURING START-UP OR PART LOAD OPERATION. THE PROJECT WILL EXTEND NEI EXPERIENCE IN SLURRY COMBUSTION TECHNOLOGY AND IMPROVE TECHNIQUES OF HEAT UTILIZATION AT THE FLAME ROOT AND ATOMIZATION SO THAT CARBON BURNOUT AND COMBUSTION EFFICIENCY ARE IMPROVED. LIAISON WITH SHEFFIELD UNIVERSITY IN THE COMPUTATIONAL MODELLING OF PARTICLE DYNAMICS AND HEAT TRANSFER WILL ENSURE TECHNOLOGY TRANSFER AND THE EFFECTIVE USE OF MODERN PREDICTIVE TECHNIQUES TO GUIDE THE EXPERIMENTAL WORK. THE RESULTS OF THE EXPERIMENTAL PROGRAMME WILL BE EXTENDED INTO THE DESIGN OF A RANGE OF SLURRY FIRING EQUIPMENT LEADING TO A PROTOTYPE TEST USING THE COMBUSTION RIG AT DERBY.