DESIGN AND MANUFACTURING OF SCREW-EXTRUDER BASED BRIQUETTING MACHINE FOR AGRICULTURAL RESIDUES

A Screw-extruder based briquetting machine was developed, manufactured and tested for the utilization of two common different agricultural residues i.e. rice straw and cotton stalks. The manufactured briquetting machine consisted of two major parts. First part is a cutting and crushing unit which receives raw materials from a hopper located above the unit and working based on rotating disc carrying six sets of rectangular blades. Each set has four blades joined together from one side as one unit and rotating with free motion or relatively adjustable with each other. Second part is a pressing and extrusion system which was fixed down the cutting and crushing unit on a metal base has rectangular frame of 1600 x 950 mm. Cut and crushed material is being transferred by delivering cone to pressing and extruder system through a conical opening with net having specific diameter of mesh to pass only desired particles sizes. An electrical motor with reduction unit used to provide the machine with required power. The experiments carried out during 2013-2014. The machine has been tested with constant compression ratio, die dimensions and ratio of the screw volume utilization at the feeder area. Study variables were; two residues (rice straw and cotton stalks), four material moisture levels of mixed materials (25, 30, 45 and 40 %), and three bending material percentages 2, 4, 6 % of residue raw material. Moisture content was measured and adjusted to be at the required level before starting the process of briquetting. Produced briquettes with different moisture content tested against their stability and durability and their densities and producing time have been recorded. Results showed that briquettes produced by screw-press based briquetting machine are hard enough to be transported when get treated at moisture content of 30 and 35 %. More shattered pieces were observed at lower moisture content of 25%. In addition, in both residue types, adding more bender led to higher impact resistance (IRI). Sufficient production rate of briquettes have been obtained at 30% moisture content, where,  production rates were 120.33, 128.67, 132.67 kg/h for rice straw mixed with 2, 4 and 6 percent of bending material respectively and for cotton stalks, the production rates were 119.00, 123.33, and 131.33 kg/h with 2, 4 and 6 percent of bending material respectively. However, higher moisture contents of 35 and 40 % lead to lower production rate. Adding more bending material to the mixture resulted to more density for both rice straw and cotton stalks material and released briquettes with higher moisture content gave higher density.