Prevention measures for hydrate ice blockage in Yu-Ji Gas Pipeline

In order to ensure the safe and stable operation of Yu-Ji Gas Pipeline in winter and avoid serious ice blockage that would affect gas transmission and pipeline safety, it is necessary to sort out gas source quality of Yu-Ji Gas Pipeline and the actual condition of alpine region, and work out safe, economic and effective measures to prevent hydrate ice blockage. Base on the thermodynamic phase equilibrium theory, the conditions of hydrate formation are predicted by Chen-Guo model, and the water content of gas source is analyzed by calculation method of water content and water dew point of pipeline gas. According to operation conditions of Yu-Ji gas trunk line, the sections likely to precipitate free water are identified. Pigging and sewage disposal in summer at these sections are suggested and the minimum methanol injection for prevention and treatment of hydrate formation is given. In view of the limitation of electric heat tracing power in gas offtake stations of Yu-Ji Gas Pipeline, the water dew point of natural gas at the state of critical water saturation is calculated according to the supply pressure and water cut of natural gas, thereby the lower-limit temperature of injecting methanol in each gas offtake station is determined. Strictly control the water dew point of gas source is the key to cut off the source of free water in gas pipeline, also the most direct and effective measure to prevent hydrate blockage in Yu-Ji Gas Pipeline and gas offtake stations.