SS2100 - Acetylene (Back End) Converter - Inlet Analyzer Solution

Application Note

Acetylene Converter Unit
The Acetylene Converter Unit consists of a series of reactors ( Fig. 1) or a single vessel with multiple beds of catalyst (Fig. 2) that reacts the Acetylene with Hydrogen to form Ethylene. The reactor or bed will reduce the amount of Acetylene from several thousand ppm down to several hundred ppm. The second reactor or bed reduces the Acetylene further to the low ppm and even ppb levels. Back End Acetylene Converters are typically located downstream of the De-Ethanizer on a mixture of Ethane and Ethylene to which Hydrogen and sometimes CO are added to reduce the Acetylene.

Critical Control of Acetylene
It is critical that the Acetylene be brought down to the proper levels as it exits the final reactor; otherwise, any Acetylene present will follow the Ethylene all the way to the final product stream. But if the unit operates too aggressively, it could hydrogenate some of the Ethylene into Ethane. Measurements are made at the inlet of the Acetylene Converter for feed-forward control strategies.

Traditional Measurement Solutions
On-line gas chromatographs have been the traditional method for monitoring the levels of Acetylene in the process streams. Unfortunately, even with the latest in chromatography techniques, the analysis can take 3-6 minutes between measurement updates. Due to the very short residence times in the reactors, this delay in measurements can easily lead to excursions in concentrations before it is detected. Also, gas chromatographs consume carrier and flame fuel cylinder gases, as well as requiring hydrocarbon-free air for flame ionization detectors, so the consumable costs of GC’s are high.

SpectraSensors’ Solution
The SpectraSensors SS2100 is the ideal solution for this challenging application. The use of Tunable Diode Laser technology means that analysis results can be updated every second if desired. Furthermore, the high resolution that is inherent to TDL technology eliminates errors due to interferences that have hampered other spectrometric approaches. There are no consumables required for Acetylene analysis, so cost of ownership is low.

Component	Unit	Typical Concentration	Min. for Application	Max. for Application
Acetylene (C2H2)	ppmv	1500 - 5000	0	5000
Ethylene (C2H4)	Mole%	65	60	90
Ethane (C2H6)	Mole%	33	0	40
Hydrogen (H2)	ppmv	0	0	1000
Carbon Monoxide (CO)	ppmv	0.5	0	1000
Carbon Dioxide (CO2)	ppmv	< 1.0	0	1000
Methane (CH4)	ppmv	50 - 100	0	1000
Propylene (C2H6)	ppmv	3000	0	5000
Total	Mole%	100

 

The background stream composition must be specified for proper calibration and measurement performance. Specify the Normal composition, along with the minimum and maximum expected values for each component, especially water, the measured component. Other stream compositions may be allowable with approval from SpectraSensors. 

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Data Sheet

Performance
Target Components	Acetylene in Back End Acetylene Converter Inlet
Typical Measurement Ranges	0 – 5000 ppm (or greater)*
Typical Precision	±2% of Full Scale*
Measurement Response Time	1 to ~60 sec
Principle of Measurement	Tunable Diode Laser Absorption Spectroscopy Non-differential
Environmental Temperature Range	-20º to 50ºC (-4º to 122ºF) -10º to 60ºC (14º to 140ºF) optional
Sample Inlet Pressure	70 kPag (10 psig) typical 210 kPag (30 psig) maximum
Cell Temperature	Maintain at 50ºC +/- 0.2ºC
Maximum Cell Pressure	70 kPag (10 PSIg)
Sample Flow Rate	1 - 2 L/min (2.1 to 4.2 scfh)*
Validation	Certified blend of C2H2 in Nitrogen balance
Electrical
Power	100-240 VAC, 50-60 Hz standard
Max Current	Controller: 1 A @ 120 VAC
Controller to Cell Cable Length	1m standard (3m, 5m & 10m available optionally)
Communication	Current Loop Output 4-20 mA Isolated, 1200 ohms @ 24 VDC max load Serial: ASCII Text RS232C standard Modbus RS232C
Digital Outputs	4 ea. 12 VDC for valve operations Scrubber (if required), Process/Val, Val 1, Val 2 5 SPDT (Form C) Dry Contact Alarms Common Fault, Val 1 Active, Val 2 Active, Val Fail, one user-assignable to any alarm
LCD Display	Concentration, Cell Pressure and Temperature, Diagnostic Data
Physical
Controller Enclosure	NEMA 4X - 304 Stainless Steel standard
Controller Dimensions	343mm H x 305mm W x 165mm H (13.5" H x 12" W x 6-7/16" D)*
Weight Approximately	13.1 Kg (28.6 lbs)*
Sample Cell Dimensions	0.8m cell 438 mm H × 108 mm W (17-1/4” H × 4-1/4” W)*
Sample Cell Construction	316L Series Polished Stainless Steel standard
Number of Sample Cells	1 (single channel SS2100) or 2 (dual channel SS2100)
Area Classification	CSA Certified for Class I, Division 2, Groups ABCD Temp Code T3C  ll 2G Ex d llB+H2 T5; Tamb : -20 ÷ +60 °C
Dimensions with Sample System	1678 mm H x 613 mm W x 427 mm D (66” H x 24-1/8” W x 16-13/16” D)
Weight with Sample System (approx.)	68 kg (150 lbs.)
* Application specific; consult factory

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