Williams Orla, Taylor Simon, Lester Edward, Kingman Sam, Giddings Donald, Eastwick Carol
Faculty of Engineering, The University of Nottingham, University Park, Nottingham NG7 2RD, UK.
Materials (Basel). 2018 Jul 31;11(8):1329. doi: 10.3390/ma11081329.
In this paper, the applicability of mechanical tests for biomass pellet characterisation was investigated. Pellet durability, quasi-static (low strain rate), and dynamic (high strain rate) mechanical tests were applied to mixed wood, eucalyptus, sunflower, miscanthus, and steam exploded and microwaved pellets, and compared to their Hardgrove Grindability Index (HGI), and milling energies for knife and ring-roller mills. The dynamic mechanical response of biomass pellets was obtained using a novel application of the Split Hopkinson pressure bar. Similar mechanical properties were obtained for all pellets, apart from steam-exploded pellets, which were significantly higher. The quasi-static rigidity (Young's modulus) was highest in the axial orientation and lowest in flexure. The dynamic mechanical strength and rigidity were highest in the diametral orientation. Pellet strength was found to be greater at high strain rates. The diametral Young's Modulus was virtually identical at low and high strain rates for eucalyptus, mixed wood, sunflower, and microwave pellets, while the axial Young's Modulus was lower at high strain rates. Correlations were derived between the milling energy in knife and ring roller mills for pellet durability, and quasi-static and dynamic pellet strength. Pellet durability and diametral quasi-static strain was correlated with HGI. In summary, pellet durability and mechanical tests at low and high strain rates can provide an indication of how a pellet will break down in a mill.
本文研究了机械测试在生物质颗粒特性表征方面的适用性。对混合木材、桉树、向日葵、芒草以及经蒸汽爆破和微波处理的颗粒进行了颗粒耐久性、准静态（低应变率）和动态（高应变率）机械测试，并将其与哈氏可磨性指数（HGI）以及刀磨机和环辊磨机的研磨能量进行了比较。利用分离式霍普金森压杆的一种新应用获得了生物质颗粒的动态力学响应。除蒸汽爆破颗粒的力学性能明显较高外，所有颗粒的力学性能相似。准静态刚度（杨氏模量）在轴向方向最高，在弯曲方向最低。动态力学强度和刚度在径向方向最高。发现颗粒强度在高应变率下更大。对于桉树、混合木材、向日葵和微波颗粒，径向杨氏模量在低应变率和高应变率下几乎相同，而轴向杨氏模量在高应变率下较低。得出了刀磨机和环辊磨机中颗粒耐久性的研磨能量与颗粒准静态和动态强度之间的相关性。颗粒耐久性和径向准静态应变与HGI相关。总之，颗粒耐久性以及低应变率和高应变率下的机械测试可以提供颗粒在磨机中如何破碎的指示。
