基于光滑粒子动力学顶煤放落与输送过程仿真研究

目前针对综放开采中顶煤放出规律的数值模拟研究中,对于顶煤运动的连续-非连续性问题需复杂的耦合算法,必须解决煤岩界面信息精确交互问题,且忽略了刮板输送机输送过程。针对该问题,基于光滑粒子动力学构建了无网格数值计算模型,通过建立连续介质力学控制方程的光滑粒子动力学离散方程,并引入弹塑性土体本构模型和Drucker-Prager屈服准则,实现了顶煤坍塌、运移、放出过程的动态模拟。考虑采场实际放煤和输煤过程,构建了刮板输送机模型,模拟沿工作面水平方向顶煤放出和底煤输送过程,得到不同刮板输送机运行速度(0~1.5 m/s)下的煤岩界面和煤流速度变化规律。仿真结果表明:弹塑性土体本构模型可有效模拟颗粒的流动行为,通过设定摩擦角、弹性模量等材料参数,避免了传统离散元法模型的参数不定问题;煤流速度稳定后,放煤口附近的顶煤应力分布呈“双峰”形态;刮板输送机运行速度对放煤时间影响较大,但对终止的煤岩界面和放出体形状影响较小;多支架同时放煤需考虑刮板输送机的输送能力,不同支架之间的底煤输送干涉可能导致放煤口的堵塞效应;“见矸关门”准则导致不同放煤口放煤量存在差异,40个放煤口顶煤放出量的标准差(7.52 m^(2))高于自动放煤的标准差(1.93 m^(2))。

Model for Reduction of Iron Oxide Pellet with a C-O-H-N Gas Mixture Considering Water Gas Shift Equilibrium in the Gas While It Diffuses through the Product Layer

In metallurgical processes, more and more usage of hydrocarbons is encouraged to bring down the carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This may be owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1,000 K, generally so for many reduction processes, the homogeneous gas reaction rates are expected to be high enough that local equilibrium in the gas phase can be assumed. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.