石油焦高压密相气力输送过程的数值模拟研究

发布时间：2018-01-05 12:03

本文关键词：石油焦高压密相气力输送过程的数值模拟研究　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：石油焦气化制氢是高效、清洁利用石油焦的一种新型技术,而石油焦高压密相气力输送是该技术中的关键一环。石油焦高压密相气力输送过程中固相颗粒浓度高,运动状态复杂,对其流动规律了解并不是十分清楚。同时由于缺乏可靠的理论依据作指导,在实际应用过程中,气输管道内的堵塞现象经常出现。为了有效预防与解决实际石油焦颗粒输送过程中管道内的堵塞问题,有必要对其输送过程中管内流体的流动特性展开研究。本文运用理论分析与数值仿真相结合的研究方法,对不同工况下水平管、竖直管和弯管中气固两相流的速度分布、浓度分布、最佳经济速度以及压力降的变化规律展开研究。根据计算结果提出相应的预防措施以及解决堵管的方案,为石油焦气力输送系统的设计提供参考依据。本文研究的内容有:首先对管道中石油焦颗粒的受力进行分析,并在欧拉模型的基础上,运用颗粒动力学理论,建立了适用于石油焦密相气输过程的数学模型。该模型考虑了石油焦颗粒间的碰撞与摩擦,同时也考虑了颗粒与管壁之间的摩擦。其次,对水平管石油焦高压密相气输过程进行了数值仿真,掌握了水平管中气固两相的速度分布、颗粒浓度分布以及压降规律。分析了表观气速、石油焦颗粒直径、输送介质以及颗粒质量流量对水平管内气固两相速度、浓度分布以及压力降的影响;探讨了颗粒质量流量及颗粒直径对水平管压降规律的影响。结果表明:由于重力作用,水平管中石油焦颗粒的流动形态为典型的非均相悬浮流动,颗粒在管底形成沉积层导致管内气固两相浓度分布的不均匀性非常显著;管内压力损失随着表观气速先增大后减小,且针对特定的质量流量,存在一个使管内压降达到最小的最佳经济输送气速。再次,通过建立垂直向上一体化管道,分别分析了垂直管段以及弯管中气固两相的流动特性以及压降规律,以及输送介质、颗粒直径、弯管曲率半径等对输送过程的影响。结果显示:垂直管中气固两相的速度与浓度均呈对称分布,且石油焦颗粒体积分数的最高值并非出现在管道中心而是出现在y/R=0.8附近;同时垂直管中针对特定的颗粒质量流量也存在一个最佳经济速度,且通过比较可知,相同条件下水平管中压降与最佳经济速度均小于竖直管;在弯管中,由于离心力作用,石油焦颗粒向弯管外侧发生堆积,且该堆积现象在超过弯管45°面后发生的尤为明显,并且颗粒在经过弯管45°面后速度急剧下降,管内能量损失加剧,通过分析可知当弯管曲率半径越小时这种现象越明显。最后,通过对前面计算结果的分析,提出了一种弯管结构的优化设计,并通过数值模拟验证了该结构的有效性。
[Abstract]:Gasification of petroleum coke to produce hydrogen is a new technology for efficient and clean utilization of petroleum coke. The high pressure dense phase pneumatic transportation of petroleum coke is a key link in this technology. The solid phase particle concentration is high and the movement state is complex in the process of high pressure dense phase pneumatic transportation of petroleum coke. It is not very clear to understand its flow law. At the same time, because of the lack of reliable theoretical basis to guide, in the practical application process. In order to effectively prevent and solve the blockage problem in the pipeline during the transportation of petroleum coke particles, the blockage phenomenon often occurs in the gas pipeline. It is necessary to study the flow characteristics of the fluid in the pipe during the transportation process. In this paper, the theoretical analysis and numerical simulation are used to study the horizontal pipe under different working conditions. The velocity distribution, concentration distribution, optimum economic velocity and pressure drop of gas-solid two-phase flow in vertical pipe and curved pipe are studied. According to the calculation results, the corresponding preventive measures and the scheme to solve the blockage are put forward. This paper provides a reference for the design of petroleum coke pneumatic conveying system. The main contents of this paper are as follows: firstly, the stress of petroleum coke particles in pipeline is analyzed, and on the basis of Euler model, particle dynamics theory is used. A mathematical model suitable for petroleum coke dense phase gas transmission process is established. The model takes into account the collision and friction between petroleum coke particles and the friction between particles and pipe wall. Secondly. The numerical simulation of high pressure dense phase gas transmission process of horizontal petroleum coke is carried out, and the velocity distribution, particle concentration distribution and pressure drop of gas-solid two-phase in horizontal pipe are mastered, and the apparent gas velocity and particle diameter of petroleum coke are analyzed. The influence of transport medium and particle mass flow rate on gas-solid two-phase velocity, concentration distribution and pressure drop in horizontal pipe; The effect of particle mass flow rate and particle diameter on the pressure drop of horizontal pipe is discussed. The results show that the flow pattern of petroleum coke particles in horizontal pipe is a typical heterogeneous suspended flow due to the effect of gravity. The formation of sediment layer at the bottom of the pipe leads to the inhomogeneity of gas-solid two-phase concentration distribution in the tube. The pressure loss in the pipe increases first and then decreases with the apparent gas velocity, and for a specific mass flow rate, there exists an optimal economic gas velocity to minimize the pressure drop in the pipe. Thirdly, through the establishment of vertical upward integration pipeline. The characteristics of gas-solid two-phase flow, pressure drop, transport medium and particle diameter in vertical pipe and curved pipe are analyzed respectively. The results show that the velocity and concentration of gas-solid phase in vertical pipe are symmetrically distributed. Moreover, the highest volume fraction of petroleum coke particles does not appear in the center of the pipeline, but in the vicinity of yr / R ~ (0.8). At the same time, there is an optimal economic velocity for the specific particle mass flow in vertical pipe, and the comparison shows that the pressure drop and the optimal economic velocity in horizontal tube are both smaller than vertical tube under the same conditions. Because of centrifugal force, petroleum coke particles pile up to the outer side of the bend pipe, and the accumulation phenomenon is especially obvious after the 45 掳plane of the bend pipe. After passing through 45 掳plane, the velocity of particles decreases sharply and the energy loss in the pipe increases. The phenomenon is more obvious when the curvature radius is smaller. Finally, through the analysis of the results of the previous calculation. An optimal design of the curved pipe structure is presented, and the effectiveness of the structure is verified by numerical simulation.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE626.87

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