HYDROGEN-FREE SULPHUR SPECIFIC ANALYSER CERTIFIED FOR HAZARDOUS AREA ZONE I AND II USING “D” TYPE ENCLOSURE
Most of natural gas production and exploitation sites are considered as hazardous area. This is as well the case for Liquefi ed Petroleum Gases (LPG) sites. It means that any fl ammable atmosphere must be avoided. It is very important to keep in mind this constraint for the providers of solution to valorise these resources.
Natural gas is a natural resource present on the earth which can vary in composition depending on the place it is extracted.
In order to use and valorise natural gas, it is necessary to control its composition. Even if it is composed mainly of methane, natural gas contains some traces of sulphur compounds which can affect its quality and can have dramatic effects for its transportation (e.g. corrosion of the pipes). Therefore, companies that work with natural gas control the level of sulphur compound impurities as well as adding specifi c Mercaptans to make it odorant and easily detectable in case of a leak.
For more than 30 years, Chromatotec® chromatography principles, to measure H2
has manufactured the MEDOR® instruments, based on the gas Total Sulphur in natural gas or gaseous fuels. Thanks to the advantages of the “MEDOR”®
S, all Mercaptans, Sulphides, Tetrahydrothiophene (THT) and technology
and its large deployment in the USA, American customers have defi ned a new guideline based on the solution: ASTM D7493-08 “Standard Test Method for Online Measurement of Sulphur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatograph and Electrochemical Detection”.
As the MEDOR® development of an ATEX solution was an evidence to expand Chromatotec®
analyser only needs from 5 to 60 mL/min of nitrogen or zero air to operate, the position on hazardous
areas market. It started in 2009 with the development of a Purge solution. These solutions are ATEX and CSA certifi ed to operate in hazardous areas zone I and II. Nevertheless, the main limitation is the use of an important fl ow of purge gas (from 30 to 60 L/min of nitrogen or air) which is not always available on site. Then, the second step which started on January 2017 was to develop and produce an ATEX solution using a “d” type enclosure which does not need any purging gas. This solution can be implemented in area zone I and II depending on customers need.
This solution was developed keeping in mind the possibility to get the certifi cation necessary for other areas in the world – such as CSA for America. Now Chromatotec®
sulphur analyser with speciation requiring only 5 to 60 ml/min of zero air or nitrogen for operation including internal automatic calibration. In addition MEDOR®
Other technologies require at least two gases to operate and/or a convertor to convert sulphur compounds into H2
S or SO2 technology is one of the most sensitive
instrument capable to detect without pre-concentration and without any convertor down to 1 ppb of individual sulphur compounds.
depending on the detector. It can be a problem for some customers to
use hydrogen cylinders in hazardous areas, the risk of leaks remaining a mental barrier to their use. Convertors are not effi cient at 100% for all compounds and the effi ciency decreased over the time which create important error in the measurements.
A specifi c product in the MEDOR® range named energyMEDOR® allows the speciation and
measurement of sulphur compounds in different matrix (natural gas, LPG…). The equipment specifi cations are given here:
is the only manufacturer to provide The energyMEDOR® is able to analyse individual Sulphur compounds and Total Sulphur with direct
measurement as described below. In addition the internal calibration stream (permeation tube installed into the instrument) is analysed at the end of every analysis, at very low concentration level (ppb or ppm). Results are thus automatically validated. No external calibration cylinders are required for operation. The energyMEDOR® Detector (SSD).
can detect Total Sulphur compounds thanks to its Sulphur Specifi c
A list of possible sulphur compounds to measure is given below: 1. Hydrogen sulphide (H2
S)
2. Methyl Mercaptan 3. Ethyl Mercaptan 4. N Propyl Mercaptan 5. Iso Propyl Mercaptan 6. Tertiary Butyl Mercaptan 7. TetraHydroThiophene (THT) 8. Total Mercaptans (as sum of 2+3+4+5+6)
Every component and the sum of them can be transferred to a data logger trough a specifi c communication protocol (e.g. Modbus, 4-20mA outputs…). To operate, the instrument specifi cations are: o Gas supply: N2 o energyMedor®
or zero air can be installed either in 19’’ rack or in an ATEX Cabinet type “p” or “d”.
An industrial computer is located inside the enclosure and has internal mouse and keyboard available in case local maintenance is required. The computer transmit data to a local central room via RS-485 or via an Ethernet connection. In case of long distance between the instruments and the local central room, network connection can be done via RS-485. Data can be send by the computer either via 4-20 mA output or Modbus RTU protocol.
Thanks to this internal PC, it is possible to collect data with the software Vistachrom. The software allows transferring concentrations, Total Organic Sulphur (TOS) calculations and status (calibrations, streams, default analyser) by the Modbus protocol to the control room.
A calculation module is available and has the capacity to perform concentration daily averages (on 24 hours) on selected components.
The Odorisation of natural gas is an important application where the energyMEDOR®
is a key product.
For safety reason, natural gas is required to be readily detected by a person with a normal sense of smell. Therefore, the MEDOR® solution needs to be as sensitive as the human nose.
ANNUAL BUYERS GUIDE 2018 •
WWW.PETRO-ONLINE.COM
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