Analysis of parameter adaptability for multi-product pipelines with high heads transformed into liquid ammonia transmission system

Objective The imbalance of renewable energy distribution in China bring out significant mismatches between ammonia supply and demand. Since the routes of multi-product pipelines largely align with the supply directions of ammonia energy, converting these pipelines for ammonia transportation enables the large-scale and cost-effective redistribution of ammonia energy.

Methods The MULTIFLASH module, based on OLGA software, was used to calculate the variations in saturated vapor pressure of ammonia with temperature, providing a basis for assessing the state of ammonia. A simulation model for liquid ammonia pipeline transportation was developed, referencing the design parameters of a hilly multi-product pipeline, including pipeline specifications, inter-station distances, topographic relief, transmission capacities, ambient temperatures, and pressure limits at pipeline outlets. The control variable method was employed to compare hydrothermal parameters among typical undulating pipeline segments. The results were utilized to comprehensively evaluate the flow stability and parameter adaptability of this multi-product pipeline system for its transformation to transport liquid ammonia.

Results In addition to meeting the inlet and outlet pressure limits at stations, ammonia transportation was successfully conducted in the liquid phase through this hilly pipeline. The variation patterns of hydrothermal parameters under different boundary conditions corresponded with those predicted by the Leapienzon formula and Sukhov formula that accounts for friction heat. The influence of topographical conditions on pressure and temperature was found to be greater than that of boundary conditions. Under varying boundary conditions, the trend in temperature drop amplitude closely mirrored that of pressure drop amplitude, both influenced by topographical factors. This reveals the impact of pressure variations on temperature variations, reflected in increasing temperature drop amplitudes in ascending pipeline segments and decreasing temperature drop amplitudes in descending segments.

Conclusion The research results verify the feasibility of transforming high-head multi-product pipelines for the transportation of liquid ammonia from a pressure control perspective, providing a theoretical basis for the production and operation of transformed pipelines.