Effects Of Straw Characteristics And Research Of Compression Die On Briquetting

In order to investigate the briquetting characteristics of agriculture straws, barley, oat, canola and wheat straw samples were compressed at different moisture content level, particle size (hammer mill screen size), and pressure.aplunger-die system, a semi-openedtype compression system and a commercial testing briquetter were built to obtain the process of compression and relaxation of straws and the influence of variable combination on the briquettes. The finite element models were also built to investigate the influence of structure parameters of die on the compression process.The results of plunger-die testing showed high density could be obtained at high moisture content level (15%), small screen size (19.05 mm) and high applied pressure (14.06 MPa).The compression of straw grinds could be compressed easily with low energy consumption at high moisture content level. The increasing of particle size could result in high energy consumption. Walker and Cooper-Eaton models were used to fix the experiment data of straws, the results showed that Cooper-Eaton model is better to describe the compression of the selected straws.The stress relaxation was occurred immediately at the end of compression. The higher the applied pressure was, the larger the residual stress was. The residual stress sharply decayed in a few minutes, with more than 85% of the decaying stress occurring within 1 min. High applied stress, large screen size and low moisture content level could result in a high relaxation speed in a short time.An improved mechanical model was built to explain the actual stress state of straw grinds in the zone of angled die.The experiment results showed the taper angle of die had a significant influence on the briquette densities and energy consumption. The density of briquette was increased with the increasing of angle with the decreasing of energy consumption. The maximum applied pressure and the residual stress were also increased with the increasing of angle.The simulation model of angled compression die (2°,4° and 6°) was built for the selected straws using the ABAQUS software. The results showed that the radial and axial force increased with the increasing of the angle. The strains at the central part were bigger than the contact part between grinds and die due to the affection of wall effect. The bigger the angle was, the wall effect is more significant. The effect could promote the shaping of materials, but it could also result in a high shear deformation especially at the surface part of the briquettes, which produced a low quality of briquettes.The commercial-scale testing experiment showed high compression pressure could be caused by high biomass moisture content. The increase in moisture content could decrease the total energy consumption and increase the throughput for barley, oat and wheat straws, while the increasing of moisture content decreased the throughput for canola straw. High moisture content had a negative affection on the density of briquettes. The density values of briquettes could be consistently high when straws were compressed at low moisture content after two weeks storage.