The UAE’s ultra-sour gas field posed a number of logistical and technological challenges for Al Hosn, confirmed the company’s vice president for technical and engineering support, David Keat.
The UAE’s Shah gas field will begin production of gas up to three months earlier than predicted, according to Al Hosn’s vice president for technical and engineering support, David Keat. Speaking during the opening session of Sogat 2014, Keat revealed that the plant will be fully operational by the 4th quarter of 2014, three months ahead of Adnoc’s most recent estimate of the 1st quarter of next year (2015).
“Based on the evidence of actual construction progress, we are very confident that we will be able to begin by the 4th quarter of 2014,” he said.
Once complete, the Shah Gas field will provide 14.1 million cubic metres of gas per day to help meet spiralling regional demand. The plant reached 93.8% completion by the end of January 2014 and utilities for the plant were commissioned in November 2013 and are already in service for pre-commissioning the main plant.
Keat revealed that the plant will break a number of long standing records. Due to the extremely sour nature of the gas at the Shah field, the facility will include the world’s largest sulphur recovery units, which will be comprised of four identical 2,500 metric tonnes per day (mtd) units. The units will initially produce 9,090 mtd of sulphur, which will be carried away from the plant by train.
Producing and manufacturing such a large scale sulphur recovery unit inevitably presented manufacturers with a number of problems.
“One of the main fabrication challenges with the sulphur recovery unit is the size of the tubes you would need on the waste heat boiler at the end of combustion chamber. What we have done is split that stage in two and have two combustion thermal stages running in parallel,” he said.
With H2S levels as high as 23% and CO2 levels as high as 10% at the field, corrosion of pipework and valves is set to be a key challenge for operators.
This risk has been mitigated by the plants designers by coating all of the gas gathering lines in the high pressure areas of the H2S removal phase with a Corrosion Resistant Alloy (CRA).
CRAs provide far superior resistance to the corrosion associated with high temperature sour gas than standard pipework. Its use at the Shah gas plant represents the first use of extended CRAs in a large bore, cross country, gas gathering network.