SCIENTIFIC PROCEEDINGS 2009, Faculty of Mechanical Engineering, STU in Bratislava DIFFERENCE BETWEEN COMPACTING OF SOFTWOOD AND HARDWOOD Peter KRIŽAN¹, Ľubomír ŠOOŠ¹, Miloš MATÚŠ¹, Iveta ONDEROVÁ¹, Djordje VUKELIĆ² ¹Institute of manufacturing systems, environmental technology and quality management, Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava, peter.krizan@stuba.sk; lubomir.soos@stuba.sk; milos.matus@stuba.sk ²Faculty of Technical Sciences, University of Novi Sad, vukelic@uns.ac.rs ABSTRACT The aim of this contribution is to present the results of experimental research into the compacting process which was carried out in our department. We would like to present the differences between compacting of softwood and hardwood. The type of material which we will compact is very important and is the determining factor which influences the final briquette quality. Briquette quality is evaluated mainly by the briquette density. Briquette density is very important from the point of view of manipulation, burning speed, briquette stability, etc. In this contribution we want to present the importance of the change of the input pressed material on the compacting process from the point of view of the density of the final briquette. Keywords: type of compacted material, compacting pressure, pressing temperature, briquette density, mathematical model of compacting INTRODUCTION Nowadays, the use of solid biofuels is interesting and popular. Solid biofuels are produced by compacting machines most usually from wood wastes, (chips, piece of wood waste, sawdust, topwood, coarse wood after mining, waste from forest management, tree stumps, roots, etc…). If we use solid biofuels with accumulated energy values the combustion process is as effective as burning a piece wood waste. At the present time we know many producers of compacting machines with a wide range of machines. But not every machine can produce biofuels (briquettes or pellets) to the required quality Standards. This fact demonstrates the many problems which have to be solved. The properties of the compacted material as well as technological demands are both very important to the briquette production process. The input material needs to be reduced to the optimal particle size, to dry to optimal moisture content level and we have to provide optimal technological parameters throughout the process of compacting. These optimal values are optimal according to the briquette’s quality which is set by EU Standards. Every type of material requires an independent approach. Each small change in the properties of the input materials (as you can see in article) can influence the final quality of the briquette. Different material properties cause different conditions during the compacting process. In this contribution factors influencing briquettes quality were specified and assigned. PROPERTIES OF PRESSED MATERIAL We are sure that everybody can imagine different material characteristic for example between wood and textile. In the following Figure 1 you can see the differences in density between briquettes of various different materials. Can you imagine the differences between softwoods and hardwoods from the compacting process quality point of view? And what about the differences between pine and spruce wood from the compacting process quality point of view? Therefore we decided to describe the properties of typical wood materials. This will have an influence on the