Study On Pre - Filming Technology And Simulation Of Corrosion Inhibitor For Gas Pipeline

Internal corrosion in pipeline will not only cause significant economic losses, but also seriously threaten the safety of personnel. Conventional filling methods of corrosion inhibitors have certain limitations in the practical application of gas pipeline internal anticorrosion, which leads to the development of pre-film technologies. Pre-film of corrosion inhibitors needs to form a steady corrosion inhibitor’s slug in the pipeline, as the slug runs forward, the corrosion inhibitor molecules have a good contact with the pipe wall to form a uniform, dense film of anticorrosion on the inner surface of the pipeline.The present pre-film technologies are commonly performed by pigging. This method is simple and cheap for pipelines with sending and receiving units, but now there is no theoretical researches on this technology therefore, most operating is depending on experience,the corrosion inhibitors efficiency is low.So it is necessary to explore the determining factors of the corrosion inhibitor pre-film and operating parameters.Based on the basic idea of pre-film of corrosion inhibitor in the gas pipeline, the pig pre-filming process is proposed. The correspongding experimental device is designed, and the process of pig pre-filming is discussed. Furthermore, the main factors affecting pipeline pre-filming thickness and persistence are evaluated. The improved dip and drip evaluation method is proposed based on shortage of traditiongal method. The main factors affecting pipeline pre-filming thickness and persistence are evaluated through experiments. The pig pre-film model is established to analyze the formula of pig velocity.pressure difference and stress.Research results show that pre-filming on the pipe wall can be realized by the inhibitor pre-filming device. Improved dip and drip pre-film device is more realistic The main factors which affect the pipeline pre-filming thickness and persistence include the filling quantity of corrosion inhibitor, corrosion inhibitor’s viscosity, pigging velocity, inhibitor concentration, inhibitor temperature. However, other factors such as pipe diameter, pipe wall roughness and pipeline inclination have little effect on the pre-film quality. The pre-filming thickness and persistence of pipeline increase with the increase of the filling quantity of corrosion inhibitor and then stay stable. With the increase of the corrosion inhibitor’s viscosity, the pre-filming thickness and persistence increase. The film thickness and persistence increase when the pig velocity is under1.5m/s. Pre-filming thickness and persistence will increase with the pipeline inclination angle increases. Pre-film thickness and film persistence increase with the inhibitor’s concentration increases in a certain range,when inhibitor’s concentration continues to increase, film thickness will stay stable while film persistence shows a little decrease. Pre-film thickness and persistence will increase with inhibitor’s temperature increase in the range of10～30℃, but there is little effect on the film quality when inhibitor’s temperature continues to increase.The larger the pipeline diameter and the pipe wall roughness,the smaller pipeline inclination angle, the better pre-film quality.But the influernce is not obvious. The shear force of pig is mainly caused by corrosion inhibitor’s viscosity.The pressure difference and friction of the pig are mainly influenced by pig velocity and other factors.