Study On The Law Of Naphthalene Deposition And Migration In Gas Transmission And Distribution Pipelines Before And After Gas Source Replacemen

Manufactured gas(MG)has been always used as the main gas source in most urban gas transmission and distribution systems.The naphthalene content of MG is relatively high in the pipeline.With the increase of pipeline operating years,the amount of naphthalene deposition has also increased,resulting in a decrease in the effective flow area of the pipeline and block the pipeline.With the rapid development of the natural gas industry,most cities have replaced manufactured gas with natural gas(NG).In the process,the naphthalene originally deposited on the inner wall of the manufactured gas pipeline will be gradually stripped,and flow with the natural gas in the pipeline,which may lead to pipeline blockage or equipment damage after replacement.In the process of converting MG pipeline network into NG pipeline network,a large number of pipelines are faced with renewal and replacement due to serious clogging in the pipeline.Therefore,the problem of naphthalene deposition in urban gas transmission and distribution network system before and after gas source replacement is studied.Combined with the basic characteristics of naphthalene,the prediction model of naphthalene precipitation in manufactured gas pipeline network is established.And taking Kunming gas transmission and distribution pipeline network as an example,its operation condition is simulated with Pipephase software.The amount and location of naphthalene precipitation in the different seasons of Kunming gas pipeline network are simulated by using the prediction model.For the deposition of naphthalene particles in the MG pipeline before gas source replacement,the numerical model of naphthalene particle deposition in manufactured gas pipeline is established to carry out the numerical simulation of the horizontal straight pipe,horizontal bend pipe and tee pipe.In different pipe diameter,curvature ratio,caliber ratio conditions,the effects of naphthalene particle diameter,inlet velocity,temperature and pressure on the deposition of naphthalene particles are analyzed respectively.The simulation results show that the deposition rates of naphthalene particles is positively correlated with the particle diameter of naphthalene,and negatively correlated with the inlet velocity and pressure.The naphthalene particle diameter is the main factor affecting the deposition of naphthalene particles in MG pipeline.The deposition rate of naphthalene particles increased with the increase of pipe diameter of the horizontal straight pipe,and increased with the increase of curvature ratio of the horizontal bend pipe,while increased first and then decreased with the increase of pipe diameter ratio of the tee pipe.For the migration of deposited naphthalene particles in the NG pipeline before gas source replacement,the numerical model of deposited naphthalene migration in NG pipeline is established to carry out the numerical simulation of the horizontal straight pipe,horizontal bend pipe and tee pipe.In different pipe diameter,curvature ratio,caliber ratio conditions,the effects of naphthalene particle diameter,inlet velocity,temperature and pressure on the deposition of naphthalene particles were analyzed respectively.The simulation results show that the migration rate of deposited naphthalene is negatively correlated with particle diameter,and positively correlated with pressure and inlet velocity.In horizontal straight pipe and tee pipe,the migration rate first decreases and then increases with the increase of temperature.And the particle diameter and inlet velocity are the main factors affecting the migration of deposited naphthalene.In horizontal bend pipe,the migration rate decreases with the increase of temperature.And the particle diameter is the main influencing factor of the migration of deposited naphthalene.The migration rate is positively correlated with the diameter of the horizontal straight pipe,and positively correlated with the pipe diameter ratio of the tee pipe,but negatively correlated with the bending ratio of the horizontal pipe.The average migration time of deposited naphthalene in the NG pipeline is inversely related to the change trend of migration rate.Based on the above research results,a prediction model of naphthalene deposition and migration in gas pipeline network is established.Taking the gas pipeline network in Kunming as an example,the deposition location and amount after naphthalene precipitation are predicted.The total deposition amount of naphthalene vapor in gas pipeline network before replacement is 4.89 t/a,which is 5.35 t/a compared with the actual detection data in the field.The difference is 8.60%,and the predicted naphthalene deposition location is in good agreement with the actual situation on site.