Accurate, real-time H2S measurement achieved with in-line analyser (ERTC)

Arkema, in keeping with its policy of innovation, introduces an additional service to its current Carelflex service that helps refiners to perform the sulphiding of their hydroprocessing catalysts with dimethyldisulphide (DMDS) Evolution E2 during the start-up phase of their units.


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Article Summary

During this critical period, the temperature ramp-up and DMDS Evolution E2 flow rate are adjusted depending on the H2S concentration in the recycle hydrogen.

Today, refiners manually obtain every hour the H2S concentration information with H2S reactive tubes. Due to the high toxicity of H2S and flammability of hydrogen, this measurement is a risky operation, and the refinery has to dedicate workforce to this task during the busy unit start-up period. Moreover, the accuracy of the result depends on the experience of the operators, and a faster response analysis than every hour would also be welcome to anticipate decisions for a quicker and more efficient catalyst activation.

Arkema has developed multi-step chemistry and processes based on H2S. Thanks to its know-how in handling this dangerous gas and extensive experience in the hydroprocessing catalyst sulphiding procedure with DMDS Evolution E2, Arkema has designed (patent filed) an in-line H2S analytical tool that addresses all refinery concerns:
• Accurate and continuous measurement of H2S concentration, from 0.03 to 5%.
• Tightly closed system, without any risk of exposure to H2S to workers.

The core of this equipment is a spectrometer that has benefited from the latest advances in electronics and signal treatment to drastically improve the sensitivity and selectivity of the H2S determination in a complex gas.

Equipment deployed
A full set of analytical equipment is delivered with the current equipment required to inject DMDS. All the electric equipment of the H2S analyser complies with the European ATEX certification (EC II 2 G EExd IIC T4) and can be implemented safely near the hydrogen sampling point of the hydroprocessing unit.

A small flow of the recycle hydrogen is sampled at high pressure. For an accurate and stable measurement, the gas pressure is reduced to almost atmospheric pressure before entering the analyser. The outlet gas that exits the analyser is injected into the flare network of the refinery to avoid any atmospheric release. All gas connections are achieved with high-pressure hoses and quick couplings for a fast and safe implementation.

Service description
The H2S analyser equipment is delivered with the standard Carelflex equipment needed for DMDS injection. The Carelflex team implements and tests both sets of equipment the day before the sulphiding operation. During catalyst activation, a Carelflex operator puts the H2S analyser on stream and monitors all the equipment, checking that a continuous gas flow is fed in and the H2S analyser is running normally. H2S concentration information is refreshed every two seconds and available throughout the activation process. On request, this analytical tool can 
even stay on stream after the completion of the DMDS injection and during the 
start of the production mode. The H2S concentration is automatically recorded each minute on a memory stick, and the resulting data are included in the final Carelflex report.

Benefits and Market feedback
Thanks to a versatile pressure reducer, this equipment has successfully been used to monitor H2S in the recycle hydrogen of hydrocrackers units, gasoil hydrodesulphurisation units and naphtha hydrotreaters.

Commercially launched in Europe by Arkema at the start of 2017, this new service has proved to be a great success because it offers:
• Very safe equipment: since the start, workers have never been exposed to any H2S leak.
• High reliability and excellent accuracy: continuous H2S monitoring has been achieved at all the refineries that asked 
for such a service, and H2S concentration has always been in line with other 
analytical methods (reactive tubes, online GC).
• A useful tool to better manage the catalyst sulphiding operation according to catalyst manufacturer procedures and guidelines.
• Continuous H2S indication that helps to anticipate DMDS flow rate changes.DMDS consumption and sulphiding time can be reduced significantly.

Did you know: ARKEMA now provides an 
in-line H2S analyser service during Hydroprocessing catalyst activation?

This short article originally appeared in the 2017 ERTC Newspaper, produced by PTQ / DigitalRefining.

For more information contact: francis.humblot@arkema.com

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