Extraction of value added products from Liquified Natural Gas (LNG) has never been attempted before. The C2-C3 Extraction Plant at Dahej, Gujarat is the first LNG processing plant in the world. The value added products viz Ethane (C2), Propane (C3) and Butane (C4), is feedstock for the ensuing grass root petrochemical complex (OPaL). The extraction plant consists of one train of design capacity 5.0 MMTPA (625.0 ton/h) of rich LNG with a provision of one additional train. The rich LNG is sourced from Petronet LNG Ltd (PLL), a Joint Venture of ONGC and other oil companies is located adjacent to the C2-C3 Plant.
Toyo Engineering Corporation, Japan (TEC) has developed a cryogenic process for extracting Natural-gas liquids (NGLs; C2, C3, C4 and other hydrocarbons) from Liquefied Natural Gas (LNG), known as COREFLUX®-LNG Process. COREFLUX®-LNG process refluxes with a methane-rich (> 99%) stream, which is obtained from an overhead condenser that is cooled by the LNG feed. The remaining overhead vapors are compressed and liquefied in a second condenser, resulting in LNG. Ethane, Propane and Butane are recovered from the bottom of the Demethanizer. The design allows the column to operate at lower operating pressures which result in a reduced reboiler duty.
This plant also has some more unique features. Schoepentoeter™, a proprietary Shell vane type inlet device has been used for introducing the feed into the Demethanizer column. The purpose of a Schoepentoeter™ is to decrease the momentum of the feed and achieve an even gas distribution across the vessel cross section. For accurate flow measurements during custody transfer in transportation of LNG in pipeline, an eight path high performance a Caldon make ultrasonic meter has been installed. Custody transfer of LNG in pipeline mode is a novel concept.
Due to acute shortage of quality water in the vicinity, an air assisted flare (Zeeco UFO series) has been installed to dispose off waste gases. The advantages of this type of a flare are its capability of burning heavier hydrocarbons in a smokeless manner due to superior mixing as well as an extended service life with lower operating costs at a lower noise level.
This paper will endeavour to discuss process outline of C2-C3 plant along with some of the unique features highlighted.
