Measurement of Sulfur in Refinery Flare Gas Streams for Compliance with EPA SubpartJ(a) Regulations


Courtesy of Ametek Process Instruments - THERMOX

The Challenge
Measurement of high range and low range H,S in refinery flare gas streams for compliance with EPA regulation NSPS Subpart J(a). The rule has placed an extra investment and operational burden on petroleum refineries to meet the regulatory requirement. AMETEK offers an economical solution to meet the challenge with an emphasis on lower capital and operating cost along with improved reliability.

The Solution and Proven Results
The AMETEK solution utilizes Tunable Diode Laser Absorption Spectroscopy (TDLAS) to measure H?S in the process flare line to comply with the EPA J(a) regulation. Unlike other technologies like Gas Chromatography TDLAS is a non-contact technology resistant to process upsets and virtually maintenance free. Operational savings over a Gas Chromatograph are significant. Based on customer input Operation savings related to usage of Instrument Air, Carrier Gas, Calibration Gases, Electricity, Consumable Parts, Labor can be $10,000 to $20,000 per year! As with any compliance analyzer reliability and availability is paramount. TDLAS non-contact technology is resilient to common issues that plague other analytical analyzers like contamination of liquids, exposure to process upsets, etc.

The EPA Regulation

  • In summary, routinely combusted flare gases cannot exceed 162 ppm H9S on a 3 hour rolling average.  Refineries shall continuously measure flare gas lines and record H^S on a low range scale of 0-300 ppm.
  • In addition total reduced sulfur (TRS) which is defined as H2S + COS + CS2 shall be continuously measured at a high range with a minimum scale of 0-5,000 ppm or 1.3 times the maximum expected concentration of H9S (site specific). In practice the high range scale tends to be in 0-40% H2S and higher.
  • In addition to the H2S (low range) and TRS (high range) analysis both flow and BTU must be measured, this application bulletin does not address these measurements.

The Methods of Measuring the High Range TRS
The low range (0-300 ppm) is defined as H,S and H2S only. For the high range the requirement is to measure TRS (defined as H2S + COS + CS2). The EPA document describes various choices in terms of the high range measurement to comply with the sub part J(a) requirement the most practical being...
1. Measure just the H2S at the High range (not the COS, CS2) and establish a correlation of the ratio of CS2, COS to the H2S value by grab sample and lab analysis.
2. Measure total reduced sulfur as H2S +COS + CS7 (using EPA method 15 as a basis).
3. Measure total reduced sulfur by oxidizing the sample to SO^ and measure as SO, (using EPA ref method 15a as a basis).

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