|Construction at the massive Pearl GTL project, Qatar, 2010. Click to enlarge.|
Qatar Petroleum and Shell announced the first flow of dedicated offshore gas into the Pearl gas-to-liquids (GTL) plant located in Ras Laffan Industrial City in the State of Qatar. (Earlier post.) Pearl GTL is the largest energy project ever launched in the State of Qatar, in terms of total investments. It consists of two offshore platforms 60 kilometers (37 miles) off the Qatar coast, connected by pipeline to the largest GTL plant ever built, located in Ras Laffan Industrial City.
Pearl GTL will add almost 8% to Shell’s production worldwide, making it the company’s main engine for growth for 2012. It is expected to ship its first product in 2011 and reach full production in 2012.
Once fully operational, Pearl will produce 1.6 billion cubic feet of gas per day from the North Field, which will be processed to generate 120,000 barrels per day of condensate and natural gas liquids and 140,000 barrels per day of gas to liquids (GTL) products such as cleaner-burning diesel-type fuel (gasoil, about 50,000 barrels per day); GTL kerosene for aviation fuel; base oils (about 30,000 barrels per day) for advanced lubricants; naphtha used to make plastics; and paraffin for detergents.
Shell, which is the operator of the Pearl GTL plant developed under a Production and Sharing Agreement with QP, has opened natural gas wells offshore allowing the first sour gas to flow through a subsea pipeline into the giant GTL plant onshore. Sections of the Pearl GTL plant will be started up progressively over the coming months. The Pearl GTL project was launched in July 2006 and the first stone was laid by His Highness Sheikh Tamim bin Hamad Al-Thani, the Heir Apparent in February 2007.
Two underwater 76–centimeter (30-inch) diameter pipelines are carrying the natural gas to a gas separation plant onshore that extracts natural gas liquids: ethane for industrial processes; liquefied petroleum gas (LPG) for domestic heating and cooking; and condensates as a feedstock for refineries. The separation process also removes contaminants like metals and sulphur. The sulfur is turned into pellets and shipped to the nearest market to make hydrosulfuric acid, fertilizer or other valuable products.
The pure methane that remains will then flow to the GTL section of the plant, where it will be converted in a three-stage process into a range of gas-to-liquids products using Shell proprietary technology:
Making syngas. In the gasifier at around 2,200-2,650°F (1,400-1,600°C) methane and oxygen from an air separation plant are converted into a mixture of hydrogen and carbon monoxide known as synthesis gas, or syngas. The reaction produces heat, which is recovered to produce steam for power.
Making liquid waxy hydrocarbons. The synthesis gas enters one of 24 reactors. Each reactor holds a large number of tubes containing a Shell proprietary cobalt synthesis catalyst. The catalyst serves to speed up the chemical reaction in which the synthesis gas is converted into long-chained waxy hydrocarbons and water.
The total surface area of the microscopic holes in the catalyst granules is more than eighteen times the surface area of Qatar. Placed end-to-end the tubes would stretch from Qatar to Japan. The synthesis process generates heat, which is also used to produce steam that in turn powers the GTL plant via steam turbines. All water in the GTL process is purified and reused in the utilities system of the plant to generate steam.
Shell’s catalyst company, CRI/Criterion, spent around four years using dedicated facilities in Europe in full-time production to provide the thousands of tonnes of catalysts needed for the start of production at Pearl GTL.
Making GTL (gas to liquids) products. Using another Shell proprietary catalyst, the long hydrocarbon molecules from the GTL reactor are contacted with hydrogen and cut (cracked) into a range of smaller molecules of different length and shape. Distillation separates out the products with different boiling points.