Analysis of the Process for Generating Electricityfrom Residual Pressure in A Long-distance Crude Oil Pipeline

【Objective】In the daily operation of long-distance crude oil pipelines, if there is residual pressure (surplus pressure) at the terminal station, it is usually necessary to reduce the pressure through a pressure reducing valve. During the pressure reduction process, a large amount of energy is wasted on the pressure reducing valve, and if the surplus pressure is large, it may also cause significant noise. The utilization of residual pressure in liquid pipelines is mostly applied in water transmission or chemical equipment pipelines at home and abroad, but there are few studies on the utilization of residual pressure in the field of long-distance crude oil pipelines. To achieve energy conservation and efficiency improvement in long-distance crude oil pipelines and enhance resource utilization, generating electricity from the residual pressure at the terminal station to supply the station's domestic electricity is a feasible approach. However, the technical feasibility of this process still needs to be thoroughly explored. 【Methods】This study first evaluated the potential for residual pressure power generation at an operational long-distance crude oil pipeline terminal station. Based on this assessment, installation of a hydraulic turbine in parallel with the existing pressure-reducing valve is proposed. Using the SPS simulator (SYNERGI PIPELINE SIMULATOR 10.4), the impact of operating the hydraulic turbine power generation unit at different flow rates on the hydraulic characteristics of the entire pipeline was analyzed. Emphasis was placed on changes in pressure throughout the pipeline and flow rate at the terminal station. A PID composite control system based on high-select/low-select (HS/LS) logic was compared to identify a control strategy that ensures hydraulic safety across the pipeline. This prevents hazardous conditions such as crude oil vaporization at upstream high points due to insufficient operating pressure after the hydraulic turbine unit is activated. Finally, the payback period and CO₂ emission reduction were used as indicators to evaluate the economic and environmental benefits of residual pressure power generation under different flow conditions. 【Results】The results show that at a high operating flow rate of 2 200 m³/h, the hydraulic turbine power generation device can meet the daily electricity demand for living at the terminal station without causing vaporization at the high points of the upstream pipeline. Meanwhile, the dynamic investment payback period is the shortest and the carbon dioxide reduction is the largest under high flow conditions. This indicates that a high operating flow rate is conducive to achieving better economic efficiency, stronger stability, and higher environmental benefits for the pressure difference power generation. Under medium and low operating flow rates, there is a risk of not meeting some peak electricity demands, and without reasonable control at the station, medium and low flow rates may cause vaporization at the high points of the upstream pipeline. Through simulation analysis and comparison, it is determined that the control logic of the regulating valve before the hydraulic turbine power generation device should be set to low selection (LS) to ensure the hydraulic safety of the entire pipeline within the full flow range. 【Conclusion】The analysis conclusion indicates that the pressure recovery power generation process at the terminal station of the long-distance crude oil pipeline is feasible. It can not only recover the energy from pressure reduction but also ensure the hydraulic safety of the entire pipeline. Moreover, it has certain economic and environmental benefits. This can provide an important engineering reference for the application of hydraulic turbine power generation devices in long-distance crude oil pipelines to achieve pressure recovery power generation and improve energy utilization efficiency.