Numerical Simulation Study On High-pressure Dense Phase Pneumatic Conveying Process Of Petroleum Coke

Making hydrogen by gasifying petroleum coke is a new technology of high efficiency and clean utilization of petroleum coke.High pressure dense phase pneumatic conveying of petroleum coke is a key link in this technology.In the process of high pressure dense phase pneumatic conveying of petroleum coke,the concentration of solid particles is high and the flow pattern is complex.Besides,The understanding of its flow law is not clear enough,and lack of reliable theoretical basis for guidance.These reasons lead to the the pipeline often blocked in the actual delivery process.In order to effectively prevent and solve the phenomenon of pipeline blockage,it is necessary to study the flow characteristics of the fluid in the pipeline.Through the combination of theoretical analysis and numerical simulation,this paper studied the pipeline gas-solid two-phase flow velocity distribution,concentration distribution,the best economic speed and pressure drop variation under different conditions.According to the calculation results,the paper put forward the corresponding preventive measures and solutions.It provided reference for the design of pneumatic conveying system of petroleum coke.The main contents of the research are as follows:First of all,the stress situation of petroleum coke particles in the pipeline was analyzed.On the basis of Euler model,combining the theory of particle dynamics,a mathematical model was established for the gas phase transportation of petroleum coke.The model considered not only the collision and friction between particles,but also the friction between the particles and the wall.Secondly,the numerical simulation of the high pressure dense phase gas transportation process of the horizontal tube petroleum coke was carried out.The velocity distribution,particle concentration distribution and pressure drop rule of the gas-solid two-phase in the horizontal pipe were mastered.In this paper,the effects of superficial gas velocity,particle diameter of petroleum coke,gases and mass flow rate on gas-solid two-phase velocity distribution,concentration distribution and pressure drop in horizontal tubes were analyzed.The influence of particle mass flow rate and particle diameter on the pressure drop of horizontal pipe was discussed.Results show:As a result of gravity,the petroleum coke particles in the horizontal pipe form a deposition layer at the bottom of the pipe and the flow pattern of particles in the pipe is a typical heterogeneous suspension flow;the heterogeneity of gas-solid two-phase’s distribution is very obvious;the pressure loss in the pipe increases first and then decreases with the increase of superficial gas velocity,and it exists a best economic conveying velocity which minimizes the pressure loss in the pipe.Third,through the establishment of vertical integration pipeline,this paper respectively analyzed the flow characteristics and pressure drop of the gas-solid two-phase in vertical pipe and elbow.The effects of gases,particle diameter and curvature radius of the elbow on the transport process were also analyzed.Results show:the speed and concentration of the gas-solid two-phase in vertical pipe showed symmetrical distribution,and the highest value of the volume fraction of petroleum coke is not at the center of the pipeline but near the y/R=0.8;for a specific particle mass flow,there is also a best economic conveying velocity in the vertical pipe;by comparison,it is found that the pressure drop and the best economic conveying velocity in the horizontal pipe are lower than that of the vertical tube under the same conditions;because of the centrifugal force,the petroleum coke particles heap at the outer side of the bend in elbow pipe,and the accumulation phenomenon is more obvious after exceeding 45 degrees of bend;the concentration distribution of particles in the pipe is very uneven;after passing the 45 degrees,the velocity of the particles decreases sharply,and the energy loss in the tube is serious,especially when the curvature radius of the pipe is small.Finally,based on the analysis of the calculation results,an optimal design of the structure of the elbow was presented.At the same time,the feasibility of it was verified by numerical simulation.