天然气管道干空气法干燥规律

Drying law of natural gas pipeline with dry air method

管道干空气干燥速率的研究是建立求解干燥吹扫模型、确定最优干空气技术指标的基础,但现有的干燥速率模型不满足实际工况需求。利用干空气法干燥速率实验装置,测定干空气在不同露点、流速、压力下干燥水的速率,理论推导建立了干燥速率计算模型,并应用于水平管道均匀水膜状态下干空气连续吹扫干燥计算模型中,求解制定了最优干空气技术指标。结果表明:干燥速率随着干空气露点的降低而升高,-50℃后趋于稳定;随着干空气流速的增大而增大,随着干空气压力的增大而减小。干燥速率计算模型与实验结果拟合较好;管道沿线压降较小时管道呈现从前向后干燥的规律,此时最佳干空气露点为-40℃;最佳干空气吹扫流速为6 m/s;管道沿线压降较为明显时管道呈现从两端往中间干燥的规律,干空气流速的增大必然带来管道压降的增大,此时最佳干空气技术指标与干燥作业方式、干燥时间有关。所建立模型可用于预测管道干燥时间,根据现场干燥机、压缩机的工作能力调整干空气指标,指导新建天然气管道的干燥施工。

The study on drying rate of pipeline with dry air is the basis for establishing and solving the drying and purging model, as well as determining the optimal indexes of air drying. The existing drying rate model does not meet the actual working conditions. Herein, the drying rate by dry air under different dew point, flow rate and pressure was measured with the drying rate experimental device, and on this basis, the drying rate calculation model was established through theoretical deduction. Besides, the model was applied to the calculation model of continuous purging and drying with dry air under the condition of uniform water film in horizontal pipeline, so that the optimal dry air technical indexes were solved and determined. According to the results, the drying rate increases with the decrease of dry air dew point and tends to be stable after-50 ℃, and it increases with the increasing flow rate of dry air but decreases with the increasing pressure of dry air. The calculation model of drying rate fits well with the experimental results. In case of small pressure drop along the pipeline, the pipeline is dried from front to back in turn, for which the best dew point is-40 ℃, and the best flow rate for purging is 6 m/s. However, if the pressure along the pipeline is dropped obviously, the pipeline is dried from both ends to the middle, and the increase of flow rate will inevitably lead to the increasing pressure drop. In this case, the optimal indexes are related to the drying operation mode and drying time. Generally, the drying time of the pipeline can be predicted according to the results obtained, and the dry air indexes can be adjusted according to the working capacity of the dryer and compressor on site, thus guiding the drying construction of the new natural gas pipeline.