Is an alternative to natural gas possible when it comes to powering kilns? It’s a question asked by many researchers and, of course, one of keen interest to ceramic businesses, especially in emerging economies facing serious energy supply problems. So, in order to respond to market demand, kiln makers are doing their best to find alternative energy solutions that can be competitive without compromising the quality or efficiency of the production process. Among them is Sacmi Forni, which, together with the Civil and Mechanical Engineering Faculty of the University of Modena and Reggio Emilia, has conducted and published a study on the use of “burners fed with lean gases in the ceramic firing process”.
‘Lean’ gases are gases with a low calorific value on account of their high inert diluent content (e.g. biomass or coal gasification gases). So how can they be made competitive with ‘noble’ natural gases? “The widely varying chemical composition of these gases”, states the study, “requires that the burners be studied and adapted on a case by case basis”. Above all, utilisation of these gases requires attentive preliminary investigation of firing curves and optimal heat distribution inside the kiln so that, even where a fuel of lower calorific value is used, the successful outcome of ceramic firing processes is ensured.
The answer, explain the researchers, lies in mathematics, that is in CFD (Computational Fluid Dynamics) analysis as a plausible, economically viable alternative to the costly, time-consuming field tests traditionally used to develop suitable burner models. The result of the study (which takes into account several variables, such as different fuel types, burner configurations and nominal power ratings) has been the development of “3-D” forecasting models, the starting point for the development of the first prototypes and, therefore, industrial application on a vast scale.
One of the most important conclusions reached by the study was the discovery that the geometry of most commercially available burners fails to allow combustion of all the gas in the burner; the unburnt amount, in fact, varies between 6 and 32%. In short, then, by making just a few simple inexpensive changes (which are, however, the result of a preliminary fluid dynamics analysis that is anything but simple, hence the importance of this study) it is possible to act on the geometric configuration of the burner, especially the combustion chamber, to minimise the amount of unburnt gas, which, according to tests carried out so far, can be reduced by up to 63%.
And the next step in the study? Experimentation on a real kiln to validate the data obtained from CFD simulation – with Sacmi once again aspiring to be a ‘pioneer’ of product and process innovation by getting a head start in a fast-changing world where the energy question is of ever-greater importance for the competitiveness of the ceramic industry.