CISTUS LADANIFER SOLAR DRYING, MILLLING AND PELLETIZING

Cistus ladanifer, also known as rockrose or labdanum, local species, used in some industries, such as cosmetic and perfumery, was used to produce pellets. Samples of raw material were collected and dried in a solar kiln reaching moisture content (wet basis) of 16% for trunks and 33% for leafs. The moisture content was monitored during the solar drying. The solar kiln used was instrumented with indicated sensores, datalogger and PC softwares to monitorize solar radiation, air relative humidity and temperatures, with the final objective of recording data. A calculated amount 23256 kJ/kg was needed to dry the raw material. The dryed samples were then wheight and feeded at constant mass feed rate into a Retsch SM 100 grinding mill, passing through internal sieves with holes of 5, 7 and 10 mm diameter. The energy needed for milling the raw material was monitored and the influence of using different sieves on the energy needed for the process, was evaluated. Sawdust obtained was then characterized in therms of moisture content and average mean diameter was calculated. The sawdust obtained, that passed through the three sieves presented similar moisture content values, arround 12% (wet basis). Particle mean diameter calculated was of 579, 721 and 1068 µm for the sawdust that pass trought the sieves containing holes with 5, 7 and 10 mm diameter, repectively. The milling process revealed energy consumption values of 277, 174 and 98 kJ/kg for milling Cistus ladanifer passing through sieves of 5, 7 and 10 mm diameter hole, repectively. This feedstock was then peletized at constant mass feed rate with an energy consumption of 76, 108 and 94 kJ/kg, respectivly. Durability and water resistance tests were performed to the pellets produced, revealing indexes ranged between 78- 85% and 58-76%, respectively.