Explosion Suppression Characteristics Of Aluminum Silicate Wool In Pipeline

There are many inflammable and explosive medium in petrochemical industry. When the premixed explosive flame and pressure wave propagate in the pipeline, the explosion overpressure and flame velocity will gradually increase and arouse more disasters. So research on suppression of premixed flammable gas explosion has important significance on prevention and control of fire and explosion in industry. In this paper, we established the experiment device to suppress the explosive flame propagation by placing porous materials in the pipeline. Study the synergy effect of aluminum silicate wool on the explosive flame of premixed gas C3H8/Air and pressure wave. Use the CFD software Fluent to simulate the process for explosion suppression, obtain the flow field information and analyse the suppression mechanism.The main work and the conclusions are as follows:(1)Installed the straight pipe and the elbow bend experiment equipment to study the suppression effect of aluminum silicate wool on the propagation of premixed flammable gas. By setting obstacles and polytef in the accelerating section of the pipeline to change the initial pressure of the premixed explosive flame.(2)Established the models of gas explosion, porous medium and gas turbulent combustion. All of these models were united to establish the numerical model to simulate the suppression of porous material on the propagation of the premixed explosive flame. The premixed explosive flame of C3H8/Air in the straight pipelines and elbow bends at different initial pressure were simulated by this model.Five kinds of grid,5mm×5mm,4mm×4mm,2mm×2mm,1.3mm×1.3mm, lmmxlmm, were divided to make the grid independence analysis. It was confirmed that the precision of the model was high and the calculation efficiency was better when the grid density was2mm×2mm. By comparing the numerical simulation results and the experiment results, the reliability and accuracy of the model meet the requirements.(3)The experiment result showed that it would significantly speed up the flame velocity and explosion overpressure by adding obstacles in the accelerating section. The influence on the explosion overpressure was more apparent compared to flame velocity. But when the initial pressure in the accelerating section was high, the impact on the flame velocity was greater. The aluminum silicate wool in the inner pipe had remarkable suppression effect on the explosive flame. Specific performance of the effect was that it could reduce the flame velocity and explosion overpressure. Along with the increase of the explosive overpressure, the effect of the aluminum silicate wool on the overpressure absorption and attenuation was more obvious.(4)The scanning electron microscope result indicated that the micro structure of aluminum silicate wool was3D breakthrough structure. The diameter of aluminum silicate wool fiber was5-10μm. The porous fiber skeleton structure would make the pressure wave produce attenuation besides reflection and refraction. Moreover, micro skeleton enhanced the wall effect. By comparing the aluminum silicate fiber structure before and after the explosion, it showed that massive collapse and pore compaction turned up because of the energy absorption of aluminum silicate wool.(5)The experiment showed that the position of aluminum silicate wool had significant effect on the elbow bend explosive overpressure and the export flame length. When its position was nearby the center point between ignition end and bend inlet, the explosion suppression effect is best and the explosion overpressure decreased about90%campared to empty pipe. When the poison of aluminum silicate wool was near the ignition part or the bend inlet, it played a role as obstacle to increase the pressure. According to the discharging function, more unburned gas was discharged and the flame was longer. The variation of the flame length at the pipe outlet was opposite to the explosion overpressure variation and the position variation of the aluminum silicate wool.(6)The explosive flame of the premixed gas C3H8/Air in the elbow bend was studied through the numerical simulation. The flame surface shape and the pressure waveform got in the simulation had a good agreement with the experimental results. According to the simulation, without the porous material, the flame surface would bend to the inside arc surface after bending pipe. The flame was mainly on the inside arc surface. It was burning more slowly on the outside arc surface. The explosion overpressure was higher on the outside arc surface and the flame velocity was greater on the inside arc surface. However, comparing to the empty pipe, the explosion overpressure at the inside and outside arc surface of the elbow bend dropped significantly.