Objective Online gas chromatographs are core equipment for energy metering and trade settlement of natural gas. Traditional systems commonly use expensive helium as both the separation carrier gas and the valve driving gas; valve actuation can consume as much as 70–75％ of the helium, resulting in substantial resource waste. To reduce helium consumption and improve overall equipment utilization, this study develops a solution based on carrier gas splitting and multi-flow-path collaborative optimization.

Methods By modularizing the gas path system of mainstream online gas chromatographs, the carrier and driving gases are physically decoupled. Low-cost, high-purity nitrogen or natural gas is used to replace helium as the independent driving-gas source, with a mass-flow controller added for precise regulation. Additionally, a multi-path automatic sampling system is integrated. Based on the solenoid valve structure that facilitates high-frequency actuation and low dead volumes, a three-stage sequential control logic (purge → isolate → sample) and a dynamic flow compensation strategy are implemented. This configuration enables a single chromatograph to perform continuous automatic monitoring of samples from multiple gas sources.

Results Experiments and field verification showed that when nitrogen was used for valve actuation, gas consumption was controlled at approximately 100 mL per cycle, the resolution of n-butane and isobutane reaches 2.2, and temperature stability was better than ±0.3 °C. All core performance indicators met the requirements of GB/T 13610-2020 (Analysis of Natural Gas Composition — Gas Chromatography) and JJG 1055-2009 (Verification Regulation of On-Line Gas Chromatograph). Multi-flow-path switching tests demonstrated that cross-contamination could be reduced to below 0.1％ with 30-second purging. Field application data showed that average annual helium consumption per station decreased by 78.3％ and average annual total operating cost declined by 73.8％; a single unit of the developed equipment functioned as a multi-flow-path system replacing multiple traditional devices, with the retrofit cost recoverable within four months.

Conclusion The proposed carrier gas splitting and multi-flow path collaborative optimization provide a successful chromatograph solution to the engineering problems of high energy consumption and low utilization rate while ensuring the required analytical accuracy and system stability. This solution offers a low-cost, high-return standardized retrofit approach for in-service online natural-gas chromatographs and has strong potential for wider industrial deployment. The study results supply an important technical reference for implementing the concept of “multiple-purpose machines” and low-carbon operation for online analytical instruments in the petrochemical and environmental protection fields.