Measuring H2S/H2 in a Tail Gas Treatment Units (TGTU)

Application Summary

Analysis Point Analyte Typ. Range Suitable Analyzer
Tail Gas from Claus Process H2S (hydrogen sulfide) 0-4,000 PPMV OMA-300 Process Analyzer
H2(hydrogen) 0-10%

Introduction

The purpose of a tail gas treatment unit (TGTU) is to maximize the conversion of sulfur compounds to H2S. With an efficiently run TGTU, sulfur recovery efficiency can be increased up to 99.99%.

A Sulfur Recovery Unit (SRU) is responsible for converting most of the sulfur-containing compounds into elemental sulfur, but after the SRU up to 5% of sulfur-containing compounds may remain. The stream that leaves the SRU is known as “tail gas”, and is the feed stream for the TGTU. The sulfur compounds that are still contained within the tail gas are converted by the TGTU into H2S using a catalytic hydrogenation reduction stage and an amine absorber. The treated gas is then directed to an incinerator, and the rich amine may be directed back to the SRU.

The purpose of making the H2S & H2 measurement is to validate the reduction reaction. In addition, the H2S measurement is also used to identify the sulfur load heading to the amine absorber. The OMA-300 Process Analyzer continuously outputs both H2S and H2 readings, providing new measurements approximately every 5 seconds.

System Benefits

  • Continuously measures H2S and H2 level in TGTU using UV-Vis spectrophotometer
  • Totally solid-state build with no moving parts — modern design for low maintenance
  • Ultra-safe fiber optic design eliminates the need to bring sample fluid inside analyzer unit
  • One-time calibration at factory or site. No need for re-calibration

Diagram of a Typical Tail Gas Treatment Process

In the diagram below, the tail gas treatment units analysis point is identified by AT6.

Sulfur Recovery Unit Feed Forward Analysis--Flow-Diagram-SRU

H2S and H2 are measured at AT6 in the stream leaving the TGTU, before being sent to the amine absorber.

Further Reading