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HYDROGEN EFFECTS ON X80 PIPELINE STEEL UNDER HIGH-PRESSURE NATURAL GAS/HYDROGEN MIXTURES

HYDROGEN EFFECTS ON X80 PIPELINE STEEL UNDER HIGH-PRESSURE NATURAL GAS/HYDROGEN MIXTURES. Article ID: 252. Meng , B. , Gu C.H. , Zhang L. , Zhou , C.S. , Zhao , Y.Z. , Zheng , J.Y. , Chen , X.Y. , Han , Y Presenter: J.Y. Zheng.

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HYDROGEN EFFECTS ON X80 PIPELINE STEEL UNDER HIGH-PRESSURE NATURAL GAS/HYDROGEN MIXTURES

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  1. HYDROGEN EFFECTS ON X80 PIPELINE STEEL UNDER HIGH-PRESSURE NATURAL GAS/HYDROGEN MIXTURES Article ID: 252 Meng, B., Gu C.H., Zhang L., Zhou, C.S., Zhao, Y.Z., Zheng, J.Y., Chen, X.Y., Han, Y Presenter: J.Y. Zheng . Institute of Process Equipment, Zhejiang University, China

  2. Background 1 Experiment 2 Experimental results 3 Discussion 4 Fatigue life assessment 5 Conclusion 6

  3. Cleaner fossil fuel utilization Renewable energy In China, the government requires that the coal consumption would be reduced to 65% of the total primary energy consumption and the renewable energy would be increased to 13% by 2017. SNG Oil upgrade Energy crisis … … Haze

  4. In recent years, coal-to-gas projects develop rapidly in China. Three projects put into operation by 2014, and the capacity was 3.105 billion cubic metres per years. However, there is 3-5 vol% hydrogen in SNG. Therefore, it is necessary to consider the hydrogen affect for safety assessment of the gas transmission pipeline. Sinkiang project Hexigten Banner project Inner Mongolia Huineng project

  5. How to deal with this huge amounts of electrolytic hydrogen Wind speed variability and intermittence causes the mass waste of wind power, the deprecated wind power exceeded 10% of the total installed capacity in 2013. mitigate Wind power to hydrogen demonstrative project in Zhangjiakou, China. Several National High Technology Research and Development Programs of China Hydrogen — a competitive energy storage medium for large scale integration of renewable electricity Wind power to hydrogen projects: Norway, Spain, German, Scotland……

  6. SNG New or Available Gas Grid Coal-to-Gas Coal Power Grid FCEVs H2 Storage Electrolyser H2 fuel Exiting Natural Gas Grid Low-carbon Heating Dispatchable Power Mobility HCNG Wind Energy Admixture H2 Feedback

  7. SNG Material Selection New or Available Gas Grid H2 effects on pipeline steels Structural Design H2 Exiting Natural Gas Grid Safety Assessment X80is the most widely used pipeline steel in China.

  8. Material Received from an X80 ingot after a regulated two-stage hot-rolling process. The initial rolling temperature was 1050℃ and followed by the rolling temperature of 850℃. Table 1. Chemical composition (wt. %)

  9. Test equipment & Specimens C(T) Specimen Notch Tensile Specimen Smooth Tensile Specimen autoclave autoclave

  10. Environment The fracture toughness in N2 is nearly the same as the fracture toughness in CH4 (Figure 1). The crack growth rate in pure natural gas is nearly the same as the crack growth rate in air (Figure 2). To simplify the experiment process, nitrogen gas was used to replace natural gas here. Figure 1. Effect of gas composition on fracture toughness for carbon steels Figure 2. Effect of gas composition on fatigue crack rate for 1020 steel (C-Mn steel) 11

  11. Smooth tensile properties Table 2. Tensile data Note: (HE index) Figure 1. Stress-strain curves

  12. Smooth tensile properties 20vol% hydrogen blend Fracture surfaces in nitrogen gas A

  13. Notch tensile properties Table 3. Tensile data Note: (HE index) Figure 2. Stress-displacement curves is the notch tensile strength of the specimen in nitrogen gas.

  14. SL Notch tensile properties 20vol% hydrogen blend Fracture surfaces in nitrogen gas Y X A

  15. Fatigue crack growth properties Table 4. Crack growth rate factors Figure 3. da/dN-△K curves

  16. SL （a） N2 20 vol%H2 （b） Notch specimen Smooth specimen （a） • The effect of hydrogen on the fracture behavior of high strength steels may depend on the specimen types. For the notch tensile specimens under axial loading in hydrogen containing environment, it is evident that hydrogen is easy to accumulate in front of the notch root where stress concentration occurs and causes a cohesive stress decreasing zone in the vicinity of the notch root, which leads to the reduction of fracture strength and promote brittle fracture [1-2]. （b） 20 vol%H2 20 vol%H2 Y X • Choo, W.Y. and Lee, J.Y., Thermal analysis of trapped hydrogen in pure iron. Metallurgical transactions, 13, No. 1, 1982, pp. 135-140. • Nie, Y., Kimura, Y., Inoue, T., Yin, F., Akiyama, E. and Tsuzaki, K., Hydrogen embrittlement of a 1500-MPa tensile strength level steel with an ultrafine elongated grain structure. Metallurgical and Materials Transactions A, 43, No. 5, 2012, pp. 1670-1687. • As shown in Figure a, the length along X of the center region A was longer than the length along Y, which implies the crack growth rate of Y orientation is faster, it is likely that the textured microstructure plays an important role in the crack propagation behavior of the notch specimen. However, this phenomenon is weak on the fracture surface of the smooth specimen in the same environment (Figure b). Thus, we can guess that the influence of the texture is more severe for the notch specimens. • Compared with the notch specimens tested in nitrogen gas (Figure a), there is no shear lip on the fracture surface in 20vol% hydrogen blend (Figure b), which means that hydrogen induced crack is closer to the notch root.

  17. It seems clear that the amounts of added hydrogen plays an important role, that is, added hydrogen decreases elongation, reduction of area of X80 pipeline steel, and increases its fatigue crack growth rate, which is consistent with the test results from KRISS (Figure 4, 5, 6). Mixing higher percentages of hydrogen into the natural gas bulk causes higher hydrogen partial pressure, eventually increases the concentration of dissolved hydrogen in X80 steel, which promotes HE. Figure 4. Smooth tensile test results of X70 steel at room temperature Figure 6. Fatigue crack growth behavior in air and 10MPa of gaseous hydrogen Figure 5. Notch tensile test results of X70 steel at room temperature

  18. In fact, there are many flaws which come from fabrication and assemble processes on the pipeline. To ensure the safety of the existing natural gas pipeline for transporting natural gas/hydrogen mixtures, it is essential to take into account the effect of hydrogen on the properties during safety assessment of pipeline.

  19. Designed life calculation of high-pressure pipeline can be realized by means of a fracture mechanics based approach as long as the fatigue and fracture toughness data is known. The calculation procedure is shown as follows. KIH= 102 KIC= 219 References [1-2] KIC C, m (Thin-walled vessels) t=15mm GB 50251 P=12MPa Do=1m KI=KIC Np , , , KHKS 0220 a0=0.5mm ΔN=5 a/2l=1/3 • Luo, J. and Qin, H., Research on the determination method of fracture toughness for high strength pipeline steel. Welded Pipe Tube, 32, No. 7, 2009, pp. 33-37. [Chinese] • SanMarchi, C., Somerday B.P., Nibur, K.A., Stalheim, D.G., Boggess, T. and Jansto, S., Fracture and Fatigue of Commercial Grade API Pipeline Steels in Gaseous Hydrogen, Proceedings of the ASME 2010 Pressure Vessels & Piping Division, 18-22 July 2010, Washington.

  20. Table 3. The calculated number of design cycles The added hydrogen decreases Np of high-pressure pipeline dramatically compared with the designed life under nitrogen gas, and Np decreases continuously with increasing hydrogen.

  21. The amounts of added hydrogen plays an important role in HE of X80 steel. Hydrogen embrittlement becomes more serious increase and the fatigue crack growth is significantly accelerated with increasing hydrogen concentration. • The fractographs of the tensile specimens show the brittle fracture characteristic of quasi-cleavage in hydrogen blends compared to the ductile characteristic of dimples in nitrogen gas. Nevertheless, the brittle sign is weak on the fracture surface of the smooth specimen in the same environment. • The textured microstructure caused by hot rolling has effects on HE, and the notch specimens seem to be more affected by the texture. • The calculated number of design cycles of the X80 steel pipeline is degraded by the added hydrogen dramatically, and it decreases continuously with increasing hydrogen. • Test with actual SNG should be conducted in order to consider the effect of composition on properties of X80.

  22. National Key Basic Research Program of China (973 Program, Grant No. 2015CB057601)； Fundamental Research Funds for the Central Universities ； DirectorFund Program of State Key Lab of Fluid Power Transmission and Control.

  23. Thank You for Your Attention! Welcome to Zhejiang University jyzh@zju.edu.cn No.38 on Zheda Road, Hangzhou, China

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