An Investigation Of Sulfur Deposition And Melting Characteristics In High Sulfur Content Gas Gathering And Transportation System

The behavior of sulfur particle depositing on the gas pipeline in gas reservoir with high sulfur content and its influencing factors are studied to describe the track of sulfur particle after separating out from gas flow because of the temperature and pressure decreasing while the gas transporting from gas reservoir to pipeline.The sediments in Puguang gas field gathering pipeline are acquired for laboratory analysis.Element content is measured as about 65% of S and 20% of C.In the scanning electron microscope magnification observation,sediments look like some viscous mixture and some solids with irregular shape distributed in it.As conclusion,the solids are impurities in reservoir and pipeline,viscous mixture is precipitated by elemental sulfur and pipeline corrosion inhibitor.The sediments is dissolved by toluene and separated into therein organic compounds and the insoluble material.The insoluble material is studied by XRD analysis and the S8 crystal form is founded.The viscosity-temperature characteristic of sediments is measured.The viscosity decreases with temperature increasing.However,the effect of elevated temperature on the lower viscosity slows down after 75?.Furthermore,the viscosity decreases with rotor speed increasing,which indicates it is a non-Newtonian fluid,with shear thixotropy.Sediment was subjected to thermal analysis.It is found that sediment gravity losses is greater after 220?.In the differential thermal curve,there are two endothermic peaks,which content the melting point of elemental sulfur(113?),and thermogravimetric loss temperature(220?).The melting temperature of the sediment is measured.And it is found that the toluene-insoluble solids content melting temperature is 113?,while the sediments appear fluidity below this temperature.The turbulence model in pipeline and the force of sulfur particles in gas-solid flow are studied.The equations of motion of particles are obtained,and the critical velocity that gas could carry particle exactly is worked out considering from energy loss rate perspective.The discrete phase model in FLUENT is used to describe the behavior of particles deposition on the pipe wall.Deposition at the wall of straight pipe and elbow were simulated and analyzed.The factors on the deposition rate are analyzed with sulfur particle size in the range of 0.003mm-0.03 mm,mass flow 0.01kg/s-0.1kg/s,gas flow rate 0.5m/s-25m/s.Simulation results show that in straight pipe,deposited flux on the walls decreases as gas velocity increasing or the particle diameter decreasing,because the gas carrying effect is more strong.Deposition flux increases with particle flow increasing due to particles distribution concentration increasing.Because of the vortex,deposition at pipe wall after elbow is easier to happen than that before elbow.Due to the influence of gravity,the pipeline wall deposition is greater in ground than the wall,which becomes more obvious as the size bigger.The deposition rate increases with the turbulent kinetic energy and particle flow increases.FLUENT software is used for research of sediments melting and decomposing process.k-? two-equation turbulence model and VOF multiphase flow model is adopted to simulate temperature field,phase field distribution in different gas flux,gas temperature and heating temperature.The sediments flow down along the wall eventually to the bottom of the pipe as temperature increasing.It is found that the convection heat transfer rate with gas will decrease the plugging efficiency,while temperature can speed the melting behavior.A sediment heating simulating system is developed independently which is consist of the glass oil bath system,heating system,mixing system,temperature measuring and controlling system.The behavior of sediment loop melting is studied experimentally.The results show that the temperature making sediments soft and flowing do not have to reach the melting point of sulfur because of the other complex composition of the sediments.Moreover,the gas heat transfer will affect the melting efficiency.The dissolution characteristics of impulse tube heating experiment is carried out and it is found the sediments dropped hard if diameter is small because of large environmental loss.The experiment of gas striking blockage with heating condition is carried out,and phenomenon shows that when the pressure reaches a critical value,the sediment is broken from center,rather than sliding along the wall as a whole part.Sediment broken prediction model and peak pressure reducing evaluation system are established according to shear yield stress,which can provide a scientific basis for blockage solution in gathering system.