Analysis of the Compression Consolidation Characteristics of Powders Under Gas Pressurization
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摘要: 采用气体加压方式和机械加压方式对粉体的压缩固结特性进行了比较研究,并借助力学探针表征了不同固结状态下的粉体床层密度分布规律,分析了气体加压方式对粉体固结特性的影响机制。结果表明,在气体加压方式下,较小的压应力变化就能使得压实密度显著增加,但气体会透入床层,减弱加压气体对床层产生的机械推力,因而气体加压方式下的床层压缩固结特性与机械加压方式下明显不同。气体加压方式下的床层压应力随充压速率的增加近似呈线性增加,且压实密度特征值仅为机械加压方式下该特征值的85%;机械加压相对更易导致粉体床层压实,但气体加压的最终压力对床层压实密度影响不大。力学探针测试结果表明,气体加压方式下床层密度分布比机械加压方式下均匀;量纲为一入侵阻力Fb/Fb,0可有效表征粉体床层的压缩固结程度,该入侵阻力随压应力线性增大、随压实密度的增加呈指数增加。Abstract: In the process of pressurized feeding, powders are compacted under gas pressurization, resulting in cohesive arching and flow blockage. The main reason for these problems is that the mechanism underlying consolidation of powders under gas pressurization remains largely unexplored. In this work, the consolidation characteristics of powders under gas and mechanical pressurization were investigated. The density distribution of powder bed at different consolidation states was characterized by measuring the force on an intruder immersed in the powder bed, and the mechanisms by which gas pressurization determines the consolidation characteristics of powders was analyzed. The results showed that a smaller increase in the compressive stress under gas pressurization increased the compaction density significantly; However, gas was determined to penetrate into the bed, weakening the mechanical force generated by the pressurized gas on the bed. As a consequence, the consolidation characteristics under gas pressurization and mechanical pressurization were markedly different. The compressive stress on the powder bed under gas pressurization increased linearly with the pressurization rate, and the critical value of compaction density under gas pressurization was only 85% of that of mechanical pressurization, making it relatively easier to compact the powder bed under mechanical pressurization. In addition, the final pressure of gas pressurization hardly affected the compaction density of the powder bed. Our study on the mechanical properties of the powder bed suggested that the density distribution under gas pressurization was more uniform than that under mechanical pressurization. The dimensionless resistance force Fb/Fb,0 which determined to characterize the consolidation characteristics of the powder bed was found to increase linearly and exponentially with applied normal stress and compaction density, respectively.
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Key words:
- powder /
- gas pressure /
- compression /
- consolidation /
- compaction density
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表 1 实验物料基本物性
Table 1. Properties of experimental materials
Sample ρb/(g·cm−3) ρt/(g·cm−3) w(Moisture)/% HR θ/(°) D[3,2]/μm D[4,3]/μm d10/μm d50/μm d90/μm Span Al2O3 0.5182 0.9504 0.12 1.83 48.70 4.60 9.07 2.05 7.38 17.69 2.12 表 2 粉体压缩方程拟合参数及相关性系数
Table 2. Fitting parameters and correlation coefficient of powder compression equation
Material ρb,0/(kg·m−3) σz,0/kPa N R2 Al2O3 518.2 8.79 0.076 0.983 -
[1] 蔡基利, 吴和保, 刘富初, 等. 微滴喷射快速成形Al2O3陶瓷微球的性能[J]. 材料工程, 2018, 46(11): 84-89. doi: 10.11868/j.issn.1001-4381.2017.000649 [2] 王丽萍, 郭昭华, 池君洲, 等. 氧化铝多用途开发研究进展[J]. 无机盐工业, 2015, 47(6): 11-15,62. [3] 刘臻, 管清亮, 张建胜, 等. 干煤粉气化炉煤粉输送问题分析及解决方案探讨[J]. 煤炭工程, 2017, 49(10): 109-112. [4] LU H F, CAO J K, JIN Y, et al. Study on the feeding characteristics of pulverized coal for entrained-flow gasification[J]. Powder Technology, 2019, 357: 164-170. doi: 10.1016/j.powtec.2019.08.064 [5] 刘宝华, 李振亮, 李亚, 等. 面粉多点供料气力输送系统能耗分析[J]. 粮食与油脂, 2014, 27(5): 61-63. doi: 10.3969/j.issn.1008-9578.2014.05.019 [6] LU H F, GUO X L, GONG X, et al. Effects of gas type and hopper pressure on the discharge of pulverized coal[J]. Industrial & Engineering Chemistry Research, 2012, 51(9): 3709-3714. [7] 陆海峰. 煤粉在通气料仓中的下料及其影响因素研究[D]. 上海: 华东理工大学, 2012. [8] 杜焰, 赵立杰, 李晓海, 等. 山药粉的直压特性初步研究[J]. 中国实验方剂学杂志, 2012, 18(12): 44-47. doi: 10.3969/j.issn.1005-9903.2012.12.013 [9] JENIKE A W. Analysis of solids densification during the pressurization of lock hoppers[J]. Powder Technology, 1984, 37(01): 131-143. doi: 10.1016/0032-5910(84)80012-1 [10] 丁家海, 陆海峰. 粉煤气化工业装置煤粉黏附力表征及其流动性评价[J]. 华东理工大学学报(自然科学版), 2017, 43(2): 171-177. [11] 刘一. 粉体体系堆积、流动特性及其与颗粒间作用力关系研究[D]. 上海: 华东理工大学, 2017. [12] YOHANNES B, LIU X, YACOBIAN G, et al. Particle size induced heterogeneity in compacted powders: Effect of large particles[J]. Advanced Powder Technology, 2018, 29(12): 2978-2986. doi: 10.1016/j.apt.2018.09.020 [13] TOMAS J. Fundamentals of cohesive powder consolidation and flow[J]. Granular Matter, 2004, 6: 75-86. doi: 10.1007/s10035-004-0167-9 [14] STASIAK M, TOMAS J, MOLENDA M, et al. Uniaxial compaction behaviour and elasticity of cohesive powders[J]. Powder Technology, 2010, 203(3): 482-488. doi: 10.1016/j.powtec.2010.06.010 [15] 吴福玉. 粉体流动特性及其表征方法研究[D]. 上海: 华东理工大学, 2014. [16] LIU C P, BAI S, WANG L. Resistance forces on an intruder penetrating partially fluidized granular media[J]. Physical Review E, 2019, 99(1): 012903. doi: 10.1103/PhysRevE.99.012903 [17] 刘新春. 物料的流态化对气力输送的影响[C]//2007国际气力输送技术(北京)研讨会, [s.l]: [s.n.], 2007. [18] 孙其诚, 王光谦. 颗粒物质力学导论[M]. 北京: 科学出版社, 2009. [19] CANDELIER R, DAUCHOT O. Creep motion of an intruder within a granular glass close to jamming[J]. Physical Review Letters, 2009, 103(12): 128001. doi: 10.1103/PhysRevLett.103.128001 [20] COSTANTINO D J, BARTELL J, SCHEIDLER K, et al. Low velocity granular drag in reduced gravity[J]. Physical Review E, 2011, 83(1): 011305. doi: 10.1103/PhysRevE.83.011305 [21] STONE M B, BERNSTEIN D P, BARRY R, et al. Getting to the bottom of granular medium[J]. Nature, 2004, 427: 503-504. doi: 10.1038/427503a [22] STONE M B, BARRY R, BERNSTEIN D P, et al. Local jamming via penetration of a granular medium[J]. Physical Review E, 2004, 70(4): 041301. [23] 陈阳阳, 郭秀琦, 梁财, 等. 料仓内粉体静态应力分布特性[J]. 化工进展, 2019, 38(4): 1681-1687. [24] 张炜, 周剑, 于世伟, 等. 基于颗粒物质力学的粉末高速压制过程中应力传递分布分析[J]. 应用力学学报, 2018, 35(1): 154-160,234. -