Michell moisture analyzer: proven efficacy for gas storage quality

Michell’s OptiPEAK TDL600 moisture analyser has demonstrated its suitability for monitoring moisture levels in stored natural gas after an installation with STOGIT, a division of SNAM, the Italian natural gas transmission and distribution company. The TDL600 demonstrated the necessary fast response and immunity to methane, resulting in an order for seven units.

The six-month evaluation took place at an underground natural gas storage facility near Milan. The facility has been converted from a depleted natural gas reservoir so careful control of moisture levels is important. Excess gas is taken from the regional network during the summer when demand is low, and stored in the facility to quickly respond to periods of exceptionally high demand. During storage, the gas absorbs moisture and needs to be dried to acceptable levels before being pumped into the transmission network.

It is a challenging application, where a reliable, fast responding analyzer is essential. Angelo Marconi, of the measurement methods and processes division at SNAM STOGIT, explained how the OptiPEAK TDL600 performed during the trial: ‘The Michell TDL600 performed well throughout our 6 month evaluation. The optical TDLAS principle of the analyser proved beneficial in our gas storage application. Very fast measurement response which is critical for plant operations when commencing gas export from storage. Also immunity to interference from methanol, which is a deficiency of our existing analyzers.’

The near-infrared spectroscopy measurement is not only immune to cross-interference from methanol, an additive injected to avoid hydrate formation, but also glycol, a liquid desiccant that is commonly carried-through in the export gas when operating dehydration contactor towers. Overall, the tuneable diode laser spectroscopy (TDLAS) principle of the OptiPEAK TDL600 offers the advantage of high-precision measurements combined with a fast response to changes in process gas moisture content. This makes it an ideal instrument for applications where swift action is needed to activate dehydration processes if moisture levels rise above contractual specification.

Date: 31 July 2018
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Written & issued by Michell Instruments Ltd.