World's First Demonstration Project of Natural Gas Hydrate (NGH) Land
Authors: Nogami Tomonori , Watanabe Shigeru , Nakai Satoo 
Published: March 2015

Natural Gas Hydrate (NGH) is a clathrate compound in icy state and stabilized around minus 20 degrees Celsius under atmospheric pressure. This unique characteristic allows for natural gas transportation in bulk solid form, and this method leads to reducing the total investment cost for a transportation chain. For this reason, NGH is expected to become a solution for monetizing small to medium gas fields which are considered difficult to be economically developed by liquefied natural gas (LNG).

Mitsui Engineering & Shipbuilding Co., Ltd. (MES) has been proceeding with research and development on NGH technology for a decade, and this year, completed a project to demonstrate NGH land transportation jointly implemented with The Chugoku Electric Power CO., Inc. (CEP) under financial assistance of a Japanese national institution, New Energy and Industrial Technology Development Organization (NEDO).

In this project, NGH production plant with 5 ton-per-day capacity (as NGH) was built in Yanai LNG-based Power Station of CEP, and vaporized LNG was used as feed gas for NGH production. Produced NGH was transported by purpose-built tank trucks to two users' sites located approximately 100km away from Yanai. One is a gas engine power generator as simulated industrial user, and the other is a testing facility equipped with home appliances as simulated household user for city gas use.

Through this project, MES has succeeded in demonstrating the world's first operation of the entire land transportation chain including users' consumption, and acquired actual process data necessary for developing process design of a pilot plant with 100 ton-per-day capacity, which is an indispensable step for realizing commercial project based on a production plant with 6,000 ton-per-day capacity per train.

This paper will provide an outline of this world's first demonstration project for the entire land transportation chain and also MES's development status toward commercialization of NGH marine transportation supply chain.

What is NGH?

Natural Gas Hydrate (NGH), often referred to as "Fiery Ice," is a chemical compound where natural gas molecule (guest molecule) is being trapped within a cage composed of water molecule (host molecule). This configuration is known as clathrate (Figure 1). Methane, Butane, Propane, Carbon Dioxide, Nitrogen, Hydrogen Sulfide, etc., can make such clathrate as the guest molecule although the conditions of clathrate formation vary depending on its guest molecule inside. When the guest molecule is mixed gas, it is referred to as NGH.

When NGH is discussed, it can be often confused with or referred to as Methane hydrates, existing naturally and discovered under ocean beds and in permafrost regions around the world. Although chemical structure of Methane hydrates is the same as that of NGH, however, NGH is different from Methane hydrates in the sense of being produced artificially.

NGH can contain about 160–170 times of natural gas in volume whereas LNG can contain about 600 times of natural gas (Table 1). When the hydrate dissociates, the trapped natural gas inside is released, and dissociated water remains. NGH has a unique feature, so called, "Self Preservation Effect," which enables it to be stabilized around minus 20 degrees Celsius under atmospheric pressure, not requiring cryogenic conditions like LNG. This enhances its easy-handling as a transportation medium.