Adaptability Study of Pressure Regulators in Hydrogen-Blended Natural Gas Pipelines

The advancement of hydrogen-blended natural gas (HBNG) technologies has positioned the use of existing natural gas pipelines as an effective and economical method for transportation. Yet, this process encounters significant technical challenges, particularly in the adaptability of pressure regulators within these pipeline systems, which necessitates immediate attention. This study utilizes Aspen HYSYS software to develop a high-fidelity model of a pressure-reducing and regulating system for HBNG. Evaluating the system using assessment criteria such as steady-state pressure accuracy, response time, and functional applicability allows for analyzing the impact of five variables on system performance: proportional parameters, integral parameters, hydrogen blending ratio, working pressure, and valve opening. Simulation results reveal that increasing the hydrogen blending ratio from 0 to 30% necessitates adjustments in the proportional parameter from 0.4 to 0.6, and the integral parameter from 0.25 to 0.3-0.6. These adjustments compensate for the reduced system inertia attributable to hydrogen's lower density and are essential for maintaining pressure regulation accuracy. When the pipeline pressure is maintained at 1.6 MPa, the mass flow rate declines from 800 kg/h with pure methane to 300 kg/h with pure hydrogen. Although high pressure mitigates this reduction, it is accompanied by a temperature rise of approximately 8 °C and a 30% decrease in viscosity. Additionally, as the valve opening varies from 0 to 100%, there are pronounced fluctuations in pressure differences and flow rates, with a decrease in density as the valve opens further. This study aims to ensure the stability and safety of transporting hydrogen-natural gas mixtures. In engineering practice, the control parameters of pressure regulators must be precisely adjusted according to the actual hydrogen mixture ratio. Additionally, the flow capacity of existing pressure-regulating equipment should be evaluated to determine its adaptability limits.