In the fast-evolving energy scenario we are experiencing, where governments’ policies and industries commitment are focused on leading the transition from a carbon-based energy system to a new era of energy diversification, natural gas has played, and will continue to play in the coming years, a crucial role to drive economic development while limiting environmental impact. LNG is the answer to meet the rising demand for natural gas and the global LNG market has demonstrated the most dynamic and fastest growing segment of the gas industry in the last decades.
The advantageous features of liquefied natural gas such as its high energy density, high endurance fuel tank and lower pollutant effects than other fossil fuel are making LNG more and more a choice for propulsion (as for vessel bunkering and transport fuel for trucks) and power generation. Distribution hub for LNG is under development worldwide with many regasification plants on project or construction.
Along the LNG production process, at the level of the regasification terminals an advanced technology exists to make the natural gas regasification practice more efficient, more profitable thus more competitive and even more environmentally friendly. In fact, the regasification process produces an amount of cold energy which is usually discharged. Recovering this cold thermal energy to generate additional electricity to feed the regasification process is an efficient practice to improve efficiency and reduce the costs of LNG plants. Among the different technologies nowadays available for this purpose, Organic Rankine Cycle (ORC) is the most advantageous.
Exergy, an Italian company leader in the ORC market, developed a patented cutting-edge technology known as Radial Outflow Turbine that increased the efficiency and flexibility of Waste Heat Recovery ORC installation for the Oil & Gas market. An application of this WHR system is under execution for PTT LNG Company in their Map Ta Phut regasification terminal in Rayong, Thailand. Exergy is developing the project in partnership with Baker Hughes (a GE company) for Samsung Engineering Co, the EPC contractor for the final customer and user, PPT LNG.
Map Ta Phut terminal, in operation since 2011, has been regasifying 5 million tonnes a year of gas since November 2011. The third phase of this project now under development will add 1.5 million tonnes in capacity starting operation in 2019. For PTT LNG regasification plant Exergy designed a solution to recover the heat downstream 2x Solar Turbines Mars 100 to produce 5 MWe of electricity serving the parasitic loads of the regasification process. Power requested by the client for this project was limited to 5 MWe over 7.5 MWe power potentially producible.
The ORC energy recovery system mainly consists of heat exchangers that transfer the thermal power contained in the exhaust gases of the two Solar Turbines to the ORC by means of an intermediate fluid. In the second stage, the intermediate fluid transfers the thermal power to the organic working fluid in the ORC evaporator, where the organic fluid vaporises. The vaporised fluid then expands, causing the Radial Outflow turbine to spin, producing electricity into the generator. The cooling system of this ORC system utilizes the cold water coming from the LNG regasification cycle as heat sinks in a temperature range between 5-38 °C.
This gives the double advantage of avoiding water consumption and exploiting the "cold energy" stored in LNG, which would otherwise be wasted and lost through the traditional heat discharge into seawater. The WHR installation will reduce the environmental impact of the regasification plant feeding its energy demand thus avoiding the use of conventional fossil fuel generated electricity. The environmental benefit of the WHR system is estimated in 7497 tonnes saved per year and 23,460 tonnes of CO2 emissions saved per year. The ORC will start commercial operation in the first half of 2019, setting a new standard for higher efficiency and profitability in the LNG regasification terminals market.
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Image courtesy of EXERGY
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