Achievements

Optimisation of the Kwinana's Alumina calciner, development of the Wagerup's calciner (AU)

The CFD work of the gas suspension calciner furnace was aimed at ensuring a consistent solids retention time and solids distribution among others. The work hightlighted that due to the swirling flow in the furnace there would always be a higher solids concentration towards the walls and with the right solids injection point a relatively uniform solids retention time could be achieved. In practice the calciners displayed a more consistent product quality with less material being subjected to extreme temperature.

Low NOx un-stagged Burner: Code adjustment, quantification of emissions, Validation with in-furnace measurements (NL)

Dr. Bertrand was detached to the CFD Group of the International Flame Research Founda-tion's team at Ijmuiden (N.L.) as a EUROFLAM researcher for a period of six months. Her project was dedicated to the modelling of the NOx emissions of a low-NOx 30 kW BERL Flame. The numerical simulations were carried out using the IFRF combustion subroutines implemented into a commercial CFD code. The study established the limitations of the com-puter-code for predicting NOx emissions. The ultimate outcome of the project was the modi-fications of the computer-code that led to better predictions of industrial combustion systems. The iesults of Dr Bertrand's work were presented at a European meeting held in Florence (I) in July 1997.

Increase of alternative fuels' feeding rate in Dunbar's cement preecalciner (UK)

Dr. Bertrand modelled the pre-calciner of Dunbar (3000 TPD clinker production plant) with the aim of providing insight into the phenomena occurring in the unit when burning alternative fuels: the substitution rate of tyres was then 6% of total fuel to the unit. Following her study, carried out in close collaboration with our technical team, the system now uses 6% more tyre chip fuels, which resulted in a fair decrease of the overall fuel cost to the unit. In the same time period the use of solvent fuels was increased by over 20%.

Fuel 1 Gas conversion of a 200 MW corner fired boiler (AU)

The Nabalco boiler work was/to redesign the boiler burner system to fire natural gas in place of heavy fuel oil. This was primarily driven by the incentive of a cheaper fuel, but it was essential that there was no derating (Loss of electricity production) owing to the lower flame emissivity, as the boilers also supplied all the electricity for the area as well as for the alumina refinery. Thus all the modelling was directed to finding a method of increasing convective heat transfer to make up for the radiative loss in the radiant section of the boiler. The burners were shifted downwards into the boiler to enhance the turbulence in the lower sections. An important side result from the work showed that there were aerodynamic features of the flow though the first row of superheater tubes which corresponded with a pattern of tube failures observed by the plant. They had always thought that it was caused by a water side problem (flow distribution or feedwater conditionning). The modelling also helped them to solve this, and thus increase availability even before the burner installation.

Trouble-shooting on the Pluzunet's municipal wates incinerator (FR)

A partir de l'observation du procede, d'un audit de l'exploitant et des resultats d'une modelisation CFD du four, Dr Bertrand a diagnostique des dysfonctionnements existants dans l'incinerateur et a defini an plan d'action pour en amaliorer le fonctionnement. Cette etude a eta presentee et valid& par le comite des elus du Syndicat.