Analysis of Ethylene or Propylene Stream Cracking Gas Products

Significance of the Topic

Real-time monitoring of cracking gas composition is vital for optimizing yield and ensuring efficient downstream processing in petrochemical plants. Fast and accurate analysis of light gases such as H2, N2, C2H4, C2H6, C3H6, C3H8, and C4H8 provides critical process control data.

Objectives and Study Overview

This study evaluates the performance of the Agilent 990 Micro GC system to analyze ethylene and propylene cracking gas streams. The aims include assessing chromatographic separation, repeatability, detection limits, and throughput for seven key components.

Instrumental Setup

The system employs two backflush channels:

• Channel 1: 10 m Agilent J&W CP-Molsieve 5Å column (RTS option) with argon carrier gas for H2 and N2 detection.
• Channel 2: 10 m Agilent J&W CP-Silica PLOT column with helium carrier gas for C2–C4 hydrocarbons.

Key parameters include injector temperatures of 80 °C and 60 °C, column temperatures of 80 °C and 70 °C, and short injection/backflush times to achieve cycle times under 3 minutes.

Methodology

Standard Gas A and B mixtures were injected in ten replicates to assess retention time and area repeatability. Detection limits were calculated as three times the noise level. Chromatographic performance was visualized through retention time windows of <1 min for H2/N2 and <2.5 min for hydrocarbons.

Main Results and Discussion

The system achieved baseline separation:

• H2 and N2 separated within 1 min, with RT %RSD <0.1% and area %RSD <1.0%.
• C2H4, C2H6, C3H6, C3H8, and 1-C4H8 resolved within 2.5 min with similar repeatability.

Detection limits ranged from 0.27 ppm (ethane) to 11.8 ppm (propylene) depending on component and concentration level.

Benefits and Practical Applications

The rapid analysis cycle and high precision support real-time process control in cracker operations. The compact footprint and low carrier gas consumption suit on-line refinery applications and periodic quality checks.

Future Trends and Applications

Advances may include integration of advanced detectors, automated sample conditioning, and remote connectivity for Industry 4.0 frameworks. Miniaturization and multi-channel expansion could broaden in-field utility.

Conclusion

The Agilent 990 Micro GC demonstrates robust performance for ethylene/propylene stream analysis, combining fast cycle times, excellent repeatability, and low detection limits. This makes it a reliable tool for process optimization in petrochemical cracking.

References

1. Zhang, J. Refinery Gas Analysis Using the Agilent 990 Micro GC; Agilent Technologies Application Note 5994-1043EN, 2019.