This paper will discuss the thermodynamic and mass flow changes that can occur with blending hydrogen into natural gas compression facilities, and how that affects pulsation frequencies, amplitudes, and pulsation control systems. Pulsations can negatively affect many areas of pipeline operation including compressors stations, metering areas, and piping hubs, and it is important to ensure that sufficient pulsation control or avoidance occurs when creating operational modifications. The theory behind pulsation control systems and vortex-shedding will be discussed in this paper and case study examples will be used for illustrative purposes.

Introduction and Background

The introduction of significant amounts of hydrogen to natural gas in the range of 0-100% is currently being evaluated for decarbonization and energy storage. To pragmatically achieve these goals, repurposing existing natural gas infrastructure is one of the best options. Pipeline compressors, both reciprocating compressors and centrifugal compressors, could be used when operating pipelines with hydrogen blended natural gas depending on the flow capacity and pressure ratio required. Both types of compressors have operational pulsations concerns in their associated piping systems as do metering areas; blending in hydrogen will change the thermophysical properties that affect the frequency and amplitudes of these pulsations.

Reciprocating compressors generate pulsations in the flow and API standards require a pulsation control system be installed. However, installed systems may not be effective when the speed of sound changes with the addition of a lighter gas. Centrifugal compressor piping systems and metering stations operate with gas flow velocities high enough to generate vortices at piping geometry changes, discontinuities and insertions into the flow. The frequencies and flow velocities associated with vortex generation will change once hydrogen is blended into the system.

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