Stress-Density Relationship and Energy Requirement of Compressed Olive Cake
2001
Al-Widyan, M.I. | Al-Jalil, H.F.
Large amounts of olive cake (OC) are produced in Jordan annually and impose disposal and environmental problems. Therefore, this study was an attempt to utilize OC by realizing the benefits of biomass densification for energy. The study addressed the compaction of OC in terms of gains in density, stress-density relationship, and compaction energy requirement. A fixed amount of material (13.5 g) was compressed in a 2.5-cm diameter closed-end cylindrical die using a hydraulic press. A data acquisition system was employed for the collection of instantaneous readings of load and material deformation from a load cell and LVDT, respectively. The compaction parameters included in the study were four levels of maximum axial pressure (15, 25, 35, and 45 MPa), four levels of material moisture (20, 25, 30 and 35% w.b.), and four levels of hold time (5, 10, 15, and 20 s). It was found that material density was independent of hold time and may be at least doubled achieving unit densities ranging from 1100 to 1300 kg/m 3 . Furthermore, the stress-density relationship was best represented by a simple exponential form demonstrating a response typical of biomass materials. The compaction energy required was a strong function of maximum stress and covered a range from about 3 to 7 MJ/ton. This amount of energy was a small fraction (<0.05%) of OC energy content. These findings stress the importance of optimizing OC compaction if efficient compaction equipment and processes are to be secured. At material moisture (MC) of 30 to 35% w.b., the durability of briquettes was acceptable at all P max and t levels. At lower MC, briquettes possessed poor durability regardless of P max and t. For the ranges of this study, a 15 MPa and 30 to 35% MC (w.b.) with a hold time of 5 s were considered optimum.
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