Experimental Study on the Characteristics of Weak Corrosive Surfactant Drag Reducer

Experimental study on drag-reducing characteristics of a zwitterionic surfactant additive (C₂₀H₄₃NO) in a circulation system has been carried out. It was based on the optimum concentration, temperature effect and the characteristics of resisting shear in DN27.5 pipeline. The results showed that C₂₀H₄₃NO additive has a significant drag-reducing effect depending on concentration and temperature. The most effective concentration in the tested flow loop was 900ppm at 60°C. The temperature range of the drag-reducing effect was in the range of 40 ∼ 70°C. The maximum drag reduction (DR) of 900ppm C₂₀H₄₃NO aqueous solution was 77% at the beginning of circulation with system running between 41°C and 43°C. The drag-reducing effect does not decrease remarkably after the circulation system ran for a period of seven hours, but reduces to only 5% of DR after a period of twenty-three hours. In order to study the drag-reducing characteristics of C₂₀H₄₃NO aqueous solution in the practical district heating system, the experiments with C₂₀H₄₃NO aqueous solution flow in different inner-diameter pipelines including DN50 and DN100 with rough wall were performed. The results indicated that the optimum drag-reducing concentrations are 1500ppm and 2500ppm at 45∼50°C in the DN50 and DN100 circular pipes, respectively. Finally, the technique of drag-reducing additive applying into the district heating system is discussed. And some problems in the practical application were brought forward, such as, the poor life-span of surfactant, the instabilities of drag-reducing effect and the inherent corrosion of additive itself. According to these problems, the corrosion research of C₂₀H₄₃NO aqueous solution was also conducted based on immersion method. The results show that: C₂₀H₄₃NO aqueous solution is weakly corrosive for iron-based metallic pipe comparing with CTAC aqueous solution and water.