Development of Natural-Gas Supply Chain by Means of Natural-Gas Hydrates

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper IPTC 12880, "Development of Natural Gas Supply Chain by Means of Natural-Gas Hydrate (NGH)," by Tomonori Nogami and Shigeru Watanabe, Mitsui Engineering & Shipbuilding, originally prepared for the 2008 International Petroleum Technology Conference, Kuala Lumpur, 3-5 December. The paper has not been peer reviewed. Because natural-gas hydrates (NGHs) can be stabilized at 253 K and are easy to handle, NGHs are expected to be an alternative natural-gas transportation medium to the currently available systems including liquefied natural gas (LNG). A joint industry and government project has been initiated to demonstrate the feasibility of natural-gas land transport and ocean transport in the form of NGH. Introduction Since the idea of ocean transportation of natural gas in the form of NGH was advocated by J. S. Gudmundsson of the Norwegian University of Science and Technology in 1996, various research on NGH ocean transportation has been performed. A test plant for NGH production has been built in the US. One company has been conducting research and development on the NGH-production process, a carrier ship, and the regasification process since 2001. A new conceptual design has been developed for a process development unit (PDU). NGH Process Developments Mitsui Engineering & Shipbuilding succeeded in producing NGH continuously at a high speed in March 2001, and in September of that year they started research and development of NGH in full scale to commercialize the NGH process. In January 2002, a continuous-production plant was completed that produced NGH pellets, and in 2003 a regasification facility was added. These facilities began operation as the first-stage PDU (Fig. 1) with a 600-kg/d NGH-pellet production capacity. This plant can produce high-purity NGH pellets at a high speed continuously. Feed gas is contacted with water, causing a reaction that generates NGH, followed by dewatering and cooling. The PDU made it possible to operate a circuit process. NGH pellets are made of the powder produced in the process and then are regasified to natural gas to recycle in the plant. In 2005, a second-stage NGH-production plant called a bench-scale unit (BSU) (Fig. 2) was completed. Although NGH production from mixed gas had seemed difficult to realize, artificial production of NGH succeeded at the BSU. Fig. 3 shows NGH pellets produced by the BSU in the pellet-storage drum. As an experiment of NGH land transportation, NGH pellets were transported 350 km to a 2005 World Exposition.