【Haichuan’s Best Practices】Upgrading and renewing the sensors of the trace oxygen analyzer for flue gas to ensure stable operation of the reforming unit

Thread Content

This post was last edited by HaiChuan LaoYu on 2025-10-27 at 21:11. “Based on the data from these 20 days of operation, the oxygen level in the reforming unit has remained stable between 0.63% and 0.65%, which is in line with the required operational parameters; this indicates that the upgrade of the online oxygen meter was successful!” said Ning Xiaowei, deputy manager of Process Engineering at Guangdong Petrochemical’s Refining Department 4, happily in the central control room on October 9th. 　　The catalyst regeneration efficiency of the reforming unit is directly related to product quality and yield, and the trace oxygen analyzer for regenerated flue gas is a key instrument for ensuring effective catalyst regeneration. Since August, the readings of the trace oxygen analyzers for regenerated flue gas at Guangdong Petrochemical have shown significant fluctuations, which affects the efficiency of catalyst regeneration and results in product yields that do not meet the required standards. 　　In response, the Fourth Refining Department promptly contacted the engineer from the patent holder to conduct an on-site analysis and diagnosis; it was ultimately determined that the fluctuations in the instrument readings were caused by sensor aging, and replacement of the sensor was necessary. “Based on past experience, replacing sensors inside the pipes requires shutting down the system to reduce temperature and pressure, which directly affects the annual production targets. And if removal and replacement are done online, the workers are at risk. ”said an engineer from patent holder UOP. 　　Faced with the challenge of “maintenance without shutting down the system”, technicians conducted extensive research and ultimately found an innovative solution by looking at other “extractable” online instruments: moving the sensor from inside the pipeline to the outside. To this end, the technicians specifically designed a flue gas flow measurement cell compatible with the sensor; they used the \"calibration tube\" from the old instrument as the \"sampling tube\" for the new instrument, directing the flue gas samples into the flow cell to achieve \"external\" measurement. 　　To prevent the sensors and sampling pipelines from corroding, the technicians used materials available on site; they utilized the high-temperature flue gas pipelines at 250°C as a \"natural\" heating system to heat the instruments. The sensor flow cells and measurement pipelines were all installed in close contact with these high-temperature pipelines, with additional insulation measures added on the outside. 　　Additionally, during the instrument commissioning process, the instrumentation engineers repeatedly optimized the opening degree of the sampling valve, adjusted the flow rate of the sampled gas, and properly arranged the length and shape of the exhaust piping, thereby resolving the issues of fluctuations in both the sample pressure and the pressure at the analytical exhaust outlet.