To drive greener economic growth and reduce air pollution in industrial areas, China is replacing coal-fired power generation with renewable energy and natural gas. This strategy has led to a significant demand in natural gas which is forecast to grow from around 320 billion cubic meters in 2020 to 500 billion cubic meters in 2025 (Forbes, 2020). This growth will only be feasible through building additional long-distance gas pipelines and growing LNG imports, including associated investments in storage and transmission infrastructure.
In developing this increased transmission capacity, operators are faced with the challenge of balancing costs and efficiency whilst meeting high safety standards.
The use of API X80 high strength steels, with high resistance and toughness have already increased the annual capacity of long-distance gas transmission pipelines in China, whilst maintaining economic viability.
These pipelines have a high gas transmission capacity, using 1,420 mm diameter pipes. Even with the increased volume, the gas can be transported at the Maximum Allowable Operating Pressure (MOAP), ensuring both efficiency and safety. This has been demonstrated in successive new gas transmission pipelines in China, and detailed in the examples below.
Using API X80 grade steel increased the capacity of the 2nd west east gas pipeline (WEGP)
Figure 1 below presents significant long-distance pipeline projects recently developed in China and Table 1 illustrates the respective specifications and operating parameters.
Figure 1: Gas transmission long-distance pipeline recent projects in China.
Table 1: Specifications and operation parameters of recent gas transmission pipelines in China.
Shang, C., Guo, F. - The State of the Art of Long Distance Gas Pipeline in China.
Comparing the 1st West East Gas Pipeline (WEGP), constructed using API X70 grade steel with the 2nd WEGP which used API X80 steel, the annual transmission capacity increased from 15bm3/annum to 30bm3/annum. When the amount of steel used, construction costs and other economic factors are taken into account, the investment required by the 2nd WEGP was almost the same as the first, to transport a much greater volume of natural gas.
The use of API X80 high strength steel not only enables a higher transmission capacity due to a larger pipe diameter, but also decreased the amount of material required and decreased construction costs (less consumables, lower transportation costs).
Table 2 shows the typical compositions of API X80 used for plates and coils for the projects in China, using low carbon content and up to 0.10%Nb.
Table 2: Typical steel chemical composition used on the long distance gas transmission pipelines in China.
Chenjia Shang and Fujian Guo, The State of the Art of Long-Distance Gas Pipeline in China, Issue 1/2018 Gas for Energy)
The China-Russia pipeline (C-REGP) is another successful project using 0.08% Nb for high capacity gas transmission pipeline in China
More recently the China to Russia Eastern Gas Pipeline, demonstrated how using API X80 steel with 0.08% Nb increased the capacity potential of the pipeline, using 1,420 mm diameters and 21,4 mm spiral pipes.
The API X80 grade material used demonstrated excellent properties including the high toughness of the base metal and of the heat affected zone (HAZ), required for this high gas transmission capacity pipeline, as shown in Table 3 and Figure 2.
Table 3: Chemical composition and tensile test results of API X80 pipe used at China-Russia Eastern Pipeline.
Figure 2: Evaluation of toughness by Charpy V tests of base metal (Pipe), HAZ and Weld of China-Russia Eastern Pipeline.
Adapted from Huo Chunyong, H. et al. Latest Development and Application of High Strength and Heavy Gague Pipeline Steel in China, The 26th International Ocean and Polar Engineering Conference Rhodes (Rodos), Greece, 2016.
China has recently initiated a long term plan to be carbon neutral by 2060. Increased investment is required to guarantee that this task will be successful. Natural gas will be the transition energy, playing an important role until China can use renewable and CO2 free energy alone. LNG will also be important to help fulfill the need for cleaner energy in China. The main new investments will be in pipelines for imports and domestic production of natural gas and for the distribution of LNG from the ports to end users. Again, using API X80 up to 0.10%Nb can provide an opportunity for these major projects to meet economic, capacity and safety demands.
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