The need to safely handle the sulphur is becoming stronger
As more sour gas processing plants and facilities come online at Qatar’s major industrial city at Ras Laffan, the need to safely handle the large amounts of by-product sulphur is becoming stronger, Oil & Gas Middle East takes a closer look at Qatargas’ Common Sulfur Project.
As Qatar continues to grow its LNG, GTL, Natural Gas and NGL production at its main processing hub at Ras Laffan Industrial City (RLIC) industrial complex will not only need to increase capacity to process the expected 10 billion standard cubic feet per day (SCFD) of sour gas from offshore wells, but will also need to handle the potential 12,000 tonnes per day of by-product molten sulphur from such operations.
The task of producing, granulating and ship-loading of an ever-increasing amount of sulphur from the various gas processing plants at RLIC posed a particular problem.
The plants of each producing company at the vast industrial complex had at most around 1,600 tonnes-per-day of on-site production and granulation capacity of sulphur. This was then trucked to RLIC’s Berth Area for loading on to ships using nearly 100 trucks a day.
As these plants reach their sulphur-processing capacity and newer plants come online, transportation of the sulphur becomes impractical, costly and environmentally hazardous.
The decision was taken by Qatargas to establish a common facility connected via an electrically-heated pipeline to process the sulphur from all producing plants in RLIC with conceptual and FEED studies initiated in 2002 into what is now known as the Common Sulfur Project, or CSP.
The requirements were clear: RLIC’s existing producers require proper collection, processing and ship-loading of sulphur to ensure their uninterrupted operation, while meeting strict environmental regulations.
The Engineering, Procurement and Design (EPC) for the CSP was awarded to WGI Middle East and its construction partner Al Jaber Energy Services in the third quarter of 2005.
This major work necessitated US-based WGI opening up an office in Doha in 2006 to support the CSP project when it began along with other engineering and construction projects in the area.
A committee of sulphur producers coordinated by Qatargas worked together to determine the best location for the proposed CSP. The committee included representatives from Qatar Petroleum (QP), Qatargas, RasGas, Qatargas II Project, Ras Laffan Industrial City, ExxonMobil and
As the CSP was to be situated in a logistically convenient area for receiving the molten sulphur and easily loading the granulated end-product onto ships, it needed to be placed in RLICs Berth Area where space was very limited.
“This facility was designed and then constructed on a postage stamp; a very, very small plot of space on the Berth Area in Ras Laffan - the only space available - it was about 60,000 square metres and the boundaries of the facility were hard-fixed,” said Johnny Johnson of WGI Middle East, during a presentation at SOGAT 2011 in Abu Dhabi.
Redundancy and reliability
Redundancy, or the sparing of key equipment has been included in the design of the CSP facilities which are to run for 365 days a year, as the inability to process and export sulphur would quickly lead to the scaling back in production of gas, LNG and other products resulting in a substantial loss of revenue for the producers.
To insure against such a scenario, some of the measures that were outlined by Johnson were that all individual producers were recommended to have two independent molten sulphur storage tanks, that would provide a total of five days of emergency storage capacity.
The Sulfur Storage Building (SSB) at the CSP would need up to 21 days of capacity along with two 100% capacity ship-loaders.
According to Johnson, “The overall availability of the CSP facilities was evaluated at 99.99% over a 20-year period.”
“A final fallback position during an extended outage,” he said “is the ability to initiate sulphur blocking in the Emergency Sulfur Storage Area [at the CSP site]. This can allow continued production of gas, LNG and other products for up to one year following some unexpected or catastrophic failure of Berth Area equipment.”
Up and running
The CSP and its full 30 kilometre pipeline network were validated for operation in stages from August 2009 when the pipeline received its first molten sulphur, to January this year, when the CSP exported more than one million tonnes of sulphur, Johnson said.
Although the CSP is able to process 12,000 tonnes per day of molten sulphur into granules for export using 11 granulators, its two extra granulators allow it to extend this capacity to an average of 14,300 tonnes.
Storage capacity at the SSB, a massive holding area for sulphur granules prior to ship-loading and capable of comfortably accommodating four Boeing 747s, is said to be functioning and filling up as planned, according to Johnson.
He mentioned that at present the CSP is using an existing shiploader to load the sulphur granules transported from the SSB via conveyor belts.
Ultimately the berth-side facility will have two quadrant-type shiploaders which are capable of handling up to 4,000 tonnes an hour.
Working in tandem, the shiploaders can potentially load the largest ship that docks in 24 hours, before sending it on its way to international markets.