An Experimental Study On Densification Of Biomass Fuel Under The Assisted Vibration Field

Assisted vibratory force field was introduced into the process of densification of biomass fuel in order to explore a new way in reducing the energy requirement and increasing the production efficiency in this paper.First, An experimental set-up for densifying the biomass fuel was designed and manufactured, on which the assisted vibration could introduced into piston or die in the axial direction.. A data acquisition system was developed by the technique of virtual instrument, used to measure and record the signals of extruding pressure and piston displacement during the compaction. After that, the experimental investigations on factors of affecting the densification of biomass fuel based on orthogonal test method and the contrast tests on densification of biomass fuel under the assisted vibratory force field were performed, the following conclusions were achieved:1. The milled caragana microphylla was used as the experimental material for the compaction tests in the orthogonal-test method with four factors of moisture content, particle size, charge quantity as well as the way of assisted vibration introduced. The tested results show that the main factor affecting the densification of biomass fuel is moisture content, and assisted vibration has a less effect on the density of the upgraded biomass fuel.2. The curve of pressure vs. time during the densification with assisted vibration force field is similar to one without assisted vibration force field, and all of them can be divided into five phases: pre-compaction phase, densifying phase, upgrade-keeping phase, extruding-out phase as well as ceasing and direction-changing phase. In both cases, the pressure curves have the same pattern and nearly same values in the phases of pre-compaction and densifying phase, the pressure gets to the maximum in the upgrade-keeping phase but descends in the extruding-out phase. The extruding pressure with axial vibration on the piston or on the die descends rapidly and seems as a linear relationship compared with the one without assisted vibratory force field.3. In the case of same density of products, the times needed for the densification with assisted vibratory force field in both upgrade-keeping phase and extruding-out phase are shorter obviously compared to the one needed in the normal compaction process, especially, in the upgrade-keeping phase, it becomes much shorter, showing that the process from densifying phase goes through the maximum pressure and then comes to the extruding-out phase directly.4. With the help of assisted vibration, the cycle of biomass fuel compaction is shortened, the production efficiency is increased and thus the energy requirement is lowered, also the quality of the product is improved due to that some internal stresses are counteracted by the vibration.