Drying law of natural gas pipeline with dry air method

Abstract

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.

Keywords

• natural gas pipeline
• dry air method
• dry air parameters
• drying rate
• calculation model
• optimal indexes