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Method and system of detection and quantification of the sulpur compounds in a gaseous mixture, by UV fluorescence after separtion by gas chromatography

IP.com Disclosure Number: IPCOM000022442D
Publication Date: 2004-Mar-15
Document File: 3 page(s) / 31K

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Method and system of detection and quantification of the sulphur compounds in a gaseous mixture, by UV fluorescence after separation by Gas Chromatography.

In order to meet new market requirements, industrials must be able to characterize contents of increasingly low sulphur compounds in gases. These needs come for example from environmental regulations, which aim at decreasing the emissions of sulphur products, responsible for acid rains, and require continuous emission monitoring as well as systematic control the sulphur content in the energy source (Natural gas and/or fuels). New constraints also arise from the production needs, sulphur being a poison of petrochemical catalyst. The object of our invention is to allow the quantification of each sulphur compounds in gas mixtures, with contents lower or equal to 0.50 ppm, by associating Gas Chromatography, to separate the various components of the gas mixture, and UV fluorescence, as a specific detector to quantify the sulphur compounds.

The invention will have to answer the following criteria:

-         Specific detector for the gaseous sulphur compounds, in order to avoid interferences and/or quenching effects with hydrocarbon compounds, which can be in large amount in the mixture

-         Compatible detector for all types of gaseous sulphur compounds, such as H2S, COS, SO2, CS2 and mercaptants (MeSH, EtSH, Thiophene, DMDS ...)

-         Limits of quantification < 30 ppb (V/V) for each gaseous sulphur compound (10 ppb standard already requested in the USA)

-         Linear Range equal to or higher than two orders of magnitude

-         Stability and reproducibility of the detector

-         Costs will be compared to the other systems available on the market.

A)                EXISTING SOLUTIONS & THEIR DRAWBACKS

To answer the above criteria, the literature presents several systems consisting in gas chromatography (GC) and sulfur-specific detector. The main ones are listed in Table 1.

According to this table, it appears that :

-         the GC/SCD shows a lack of stability

-         the GC/PFPD would not allow to work on 50 ppb gaseous sulfur mixtures

-         the GC/MS would require significant modifications to work on S-compounds, and time consuming adjustment to switch from the analysis of S-compounds to other families of products

-         the performances of ELDC compares to the ones of PFPD, however with a stronger requirement for maintenance (liquid reactants) and frequent adjustment.

-         The GC/AES does not compete in price

Therefore, the best available technology today is the chemiluminescence, but there is a need for the qualification and/or development of other techniques.

Sulfur- Specific Detector Detection Limit Analytical Range Quenching Stability of the Detector (%RSD)* Polyvalence, Price & Availability

SCD (Sulfur Chemiluminescence Detector) 0.5 pg/sec around 1 ppb 104 linear No Not satisfying : 4% RDS / 240 min 13% RDS / 30 days Dedicated System Relative Cost : €€€

PFPD (Pulsed Flamme Photometric Detector) 1 pg/sec around 25 ppb 103 linear : 102   Little Good : 4%...