天然气输送管线中水合物形成的边界条件

Prediction Equilibrium Boundaries of Gas Hydrates in pipeline Pipeline

运用水合物形成的热力学相平衡模拟计算方法及根据输气管线中的天然气组成 ,确定了青海和甘肃输气管线中水合物形成的边界条件 ,提出预防水合物堵塞的热力学方法。在青海和甘肃输气管线工作压力约为 2 .5～4 .11MPa的范围内 ,水合物形成最低温度约为 1～ 5℃。在 7～ 5℃时 ,在体系中加入甲醇或增加盐度可有效地控制管线中水合物的形成。在低于 7℃的条件下 ,盐度和甲醇的联合应用 ,才能有效抑制输气管线中水合物的形成。在温度低于 0℃和压力为 2 .5～ 4 .11MPa的水合物热力学稳定范围内 ,降低输气管线中的水含量可有效地控制水合物形成而产生的堵塞。

The temperature and pressure boundari es of gas hydrate formations in the Qinghai and Gansu pipelines were predicted by using calculation method of hydrate thermodynamic equilibrium coupled with the gas compositions in the pipelines,and a method to prevent hydrate plugging in th e pipelines was established based on thermodynamic methods.The lowest temperatu res of gas hydrate formations within pipeline working pressures from 2.5 to 4.11 MPa were predicted to be from 1 to 5℃ in the Qinghai and Gansu pipelines, sugg esting that within the pipeline working pressures the gas hydrates could be form ed when the temperatures are lower than 5℃ and could not be formed when the tem peratures are higher than 5℃. Whichever increasing salinity or adding methanol can effectively restrict gas hydrate formations in the pipelines in the temperat ures from -7 to 5℃. But solely increasing salinity or adding methanol up to 20 % in the pipelines could not prevent hydrate formation in the temperatures lower than -7 ℃. It needs to increase salinity and to add methanol together to e ffectively restrict hydrate formation in the pipelines. Decreasing water content s in the pipelines also can effectively restrict hydrate formation to prevent ga s hydrate plugging even if the temperatures lower than 0℃ and the pressures fro m 2.5 to 4.11 MPa are in the gas hydrate stability region.