SS2100 - Fuel Gas (Light Gases) Analyzer Solution

Application Note

H2S in Refinery Fuel Gas
Refinery fuel gas is a collection of light gases generated in various refinery processes that have been processed to remove the valuable heavier components as well as most of the corrosive sulfur compounds such as H2S. See Table 1 for a typical composition of refinery fuel gas. These fuels are used extensively in process burners and heaters.

Specifically, 40 CFR Part 60, Subpart J, paragraph 60.105 (a) (4) states:

“Instead of the SO2 monitor in paragraph (a)(3) of this section for fuel gas combustion devices subject to §60.104(a)(1), an instrument for continuously monitoring and recording the concentration (dry basis) of H2S in fuel gases before being burned in any fuel gas combustion device.”

(i) The span value for this instrument is 425 mg/dscm H2S.

The span value of 425 mg/dscm is approximately equal to 300 ppmv H2S.

Online H2S Analyzers
Many refinery sites have installed on-line gas chromatography (GC) systems for this measurement. However, GC’s have a very high initial investment cost and consume carrier gases. Additionally, they require frequent maintenance, especially those utilizing a flame photometric detector (FPD). Lead-Acetate tape systems can be used, which are expensive, use consumables, and require constant maintenance. Additionally, the spent tape is considered hazardous waste and is expensive to dispose.

SpectraSensors’ Solution
Only SpectraSensors employs Differential TDL spectroscopy to get accurate measurements in the changing background gas composition of fuel gases. The sample is scrubbed using a proprietary Copper nanoparticle absorbent that removes only H2S, and the background spectrum is acquired. Then the spectrum of the raw, un-scrubbed sample is acquired and the background spectrum is subtracted, leaving only the laser light absorbance due to H2S. The same background spectrum can be used until the background gas changes which is detected automatically by the smart controller logic by looking at the background spectrum. Since the scrubber is only used intermittently, its lifetime is typically a minimum of 18 months. Software calculates the loading of H2S on the scrubber and gives a warning when it is time to replace the scrubber, and an indicating scrubber downstream warns if the scrubber fails prematurely. The scrubber is easily replaced in a few minutes; the spent scrubber contains no hazardous materials and can be exchanged at a reduced price for a new scrubber.

The laser and detector are isolated from the sample and protected against corrosive gases. The analyzer is extremely fast (typically 16 sec/measurement) and the results are highly reliable. Requiring no consumable gases or lead acetate tapes, the cost of ownership is extremely low.

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Data Sheet

Performance
Target Components	H2S in Refinery Fuel Gas
Typical Measurement Ranges	0 – 10 through 0 – 300 ppm*
Typical Precision	±0.5 ppm or 2% of Full Scale
Measurement Response Time	1 to ~60 sec
Principle of Measurement	Differential Tunable Diode Laser Absorption Spectroscopy (H2O Scrubber Included)
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	3-4 L/min (6.4 to 8.5 scfh)*
Validation	Certified blend of H2S 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 - 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	28m Herriot Cell 559 mm H × 127 mm W (22” H × 5” 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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