ASSURING ETHYLENE PURITY: RELIABLE PPM AND PPB MEASUREMENT OF ACETYLENE WITH ONLINE TDL ANALYZERS

摘要

Real-time measurement of certain trace gas species during ethylene production is criticallyimportant for optimized production and quality control. Trace gas species such as ammonia(NH_3), moisture (H_2O) and acetylene (C_2H_2) need to be maintained at appropriateconcentration levels to achieve optimum catalytic efficiency, catalyst life time and reactorthroughput without compromising product purity for polymerization processes. This requiresaccurate monitoring of these trace gases at various stages of the ethylene production process.Last year, we presented TDL analyzers SpectraSensors developed for trace NH_3 and trace H_2Omeasurements. Conventional detection of acetylene primarily relies upon gas chromatograph(GC), which comes with a high cost of ownership, high requirements for operator expertise,intensive maintenance and slow (several minutes) measurement response times. This paperwill introduce TDL analyzers SpectraSensors developed for C_2H_2 measurements in variousstages of the ethylene production process. This paper will describe system design and presentboth lab experiment and field operation data for C_2H_2 measurements in the range of 0-10ppmv and 0-5000 ppmv. Employing 2nd-harmonic (2f) spectroscopy, multipass Herriott cells,advanced spectroscopy analysis algorithms, and compact modular sample handling systems,these analyzers have demonstrated fast response time (in seconds), superior detectionsensitivity and reading repeatability. The analyzers achieved 2σ repeatability of much betterthan ±20ppb_v for 0-10 ppm_v measurement range, better than ±0.2% of full scale for 0-5000ppm_v range.