超高压给料粉体力学行为及流动特性研究

Both powder stress behavior and flow characteristics in super high-pressure feeding hopper are frontier topics in the dry pulverized coal gasification technology. Stress distribution, flow regime and discharge characteristics of the powder in the super high-pressure feeding hopper are significant to the dense-phase pneumatic conveying. Experiments of the powder stress at the super high-pressure shear system will be carried out.The influnences of the operating parameters and powder properties on the powder stress parameters will be established. The stress distribudion of the powder at undischarge，discharge starting and normal discharge stages of the feeding hopper will be examined to reveal the effects of the pressure, pressure rise rate and powder properties on the stress distribution in the powder and hopper wall. Combined with the powder stress behavors and stress distribution in the super high-pressure feeding hopper, unconfined yield strenght, major consolidation stress and main stress of the arch will be indicated to reveal the internal mechanism of the formation of the non-steady flow state such as the arch and central flow. Relationship of the discharge characterisitics with the powder expansion, pressure and stress changes in the discharge outlet will be charactered to indiciate the discharge stability. The results is expected to provide theoretical support and data support for the design, operation and control of the super high-pressure feeding hopper.

超高压给料罐内粉体力学行为及流动特性是超高压干煤粉气化技术的前沿课题，超高压给料罐内粉体应力分布、流动形态及出料特性是浓相气力输送技术的关键问题。在超高压剪切仪上进行粉体力学试验研究，构建粉体力参数与粉体物性及操作参数之间的关联。进行超高压给料罐内粉体在非出料、出料启动及正常出料阶段的应力分布研究，探究粉体内部及料仓壁面应力随压力、升压速率及粉体物性等参数的变化规律，揭示操作参数和粉体物性与粉体应力分布及变化特性之间的关联。结合粉体力学特性及给料罐内粉体应力分布规律，获得给料罐内开放屈服强度、密实主应力与作用在料拱的主应力分布规律，揭示料拱及中心流等不稳定流动状态形成的内在机制。剖析出料口粉体膨胀、压力及应力变化规律与出料特性之间的关联，获得粉体物性、物料种类及操作参数对出料特性及稳定性的影响规律。本项目研究结果有望为超高压给料罐的设计、运行及控制提供理论支持和数据支撑。

干煤粉高压气化技术因能源转化率高、清洁环保而受到广泛的关注和重视。目前，高压给料罐出料稳定性成为制约干煤粉气化炉大型化发展的主要因素之一。粉体受力后易出现固结，形成漏斗流、料拱及鼠洞等非稳定流型。高压给料罐内的流动特性可借鉴资的资料和经验很少，对给料罐内粉体力学行为及流动特性的研究十分必要。本项目进行了含碳粉体的基础力学实验研究，构建了粉体力学参数与粉体物性及操作参数之间的关联，阐明了粉体颗粒的表面特性、粒径及外水含量等物性参数对粉体流动性的影响机制。揭示了给料罐内粉体在非出料阶段、出料启动及正常出料阶段粉体内部及料罐壁面的应力分布特性及变化规律，获得了给料罐结构、操作参数及粉体物性与粉体静态应力、动态应力及出料特性之间的关联，掌握了粉体内部静态水平应力和垂直应力的影响因素与给料罐位置及料位高度之间的动态变迁机制。对于流动性较好的粉体，出料启动瞬间排料口处出现局部壁面应力峰值并向上移动，最终停驻于筒锥结合处，形成较大的局部超压，并呈现出周期性波动；对于流动性较差的粉体，出料阶段则容易在筒锥结合处形成死区，建立了应力波动特征参数判别给料罐流动死区的理论模型，形成了出口处的应力波动特性与给料罐出料稳定性之间的详细机制。开展了给料罐内粉体的静电力及对出料稳定性影响的研究，获得了粉体荷电特性与粉体颗粒物性及操作参数之间的关联，得到了给料罐中粉体静电力分布规律及颗粒受力机制，掌握了给料罐出料过程中粉体静电力对颗粒群流动特性及出料稳定性影响机制。在高压给料罐上进行不同操作参数、物料种类及粉体物性下的粉体流动特性试验研究，结合粉体力学特性及给料罐内粉体应力分布规律，对给料罐在不同阶段的应力分布特性进行分析，揭示料拱及中心流等不稳定流动形态形成的内在机制。剖析了出料口粉体膨胀、压力及应力变化规律与出料特性之间的关联，获得了粉体物性、物料种类及操作参数对出料特性及稳定性的影响规律。