TOKYO - NKK today announced that it has developed an innovative technology for efficient, continuous production of natural gas hydrate (NGH), paving the way for low-cost massive transport and storage of natural gas.

NGH is a substance containing natural gas molecules within a cage-like structure composed of water molecules. This structure enables some 170Nm³ of natural gas to be stored in 1m³ of space. Naturally occurring NGH, also known as methane hydrate, is seen as a new natural gas resource. In addition to its excellent gas storage capabilities, NGH can be transported and stored at only -10 to -20 °C under atmospheric pressure. Various attempts have, therefore, been made in recent years to produce artificial hydrate for use in natural gas transport and storage.

Liquefied natural gas (LNG) is the most common form of natural gas for long-distance transport and storage, but it must be handled at temperatures of -162 °C, requiring cryogenic facilities. This investment makes it economically unfeasible to develop the many smaller gas fields that dot the Southeast Asia and Oceania regions.

By contrast, NGH can be transported and stored at temperatures far closer to room temperature than LNG, enabling use of much simpler facilities and reducing cooling power requirements. These strengths have propelled new studies into the feasibility of hydrate for transporting natural gas from smaller gas fields. NKK's newly developed NGH production technology represents a significant economic improvement over conventional methods.

NGH is ordinarily produced under low-temperature, high-pressure conditions. For example, natural gas and water are often brought into contact at a temperature of 5 °C and a pressure of 50 atmospheres in order to form hydrate. The key to industrial mass-production, therefore, is how efficiently natural gas and water can be brought into contact and reaction heat removed.

1. Significant increase in gas-liquid contact surface by dispersing minute natural gas bubbles in water flowing through a pipe, thereby increasing the contact between natural gas and water.
2. Use of a cooling system similar to ordinary pipe-type heat exchangers to remove the heat from the natural gas/water combination, thereby improving cooling efficiency.

Basic experiments conducted using propane confirmed that the NKK system achieved significant efficiency gains (higher production rate) over conventional systems and was capable of continuous hydrate production. Experiments also confirmed an extremely high hydrate conversion rate for gas passing through the system.

1. Substantially larger production volumes with facilities of the same size.
2. Elimination of high-pressure vessels required in conventional systems because hydrate production in the new system takes place inside piping.
3. Simpler and more compact facilities, potentially reducing equipment costs.

Recognizing the excellent properties of this system, the Japan National Oil Corporation recently selected the NKK NGH production technology for one of its funded research projects. The next step for NKK will be to construct benchmark-scale experimental facilities and perform full-fledged tests using methane, the main component in natural gas. The ultimate goal will be commercialization of the technology.

Demand for natural gas, considered a clean energy with minimal environmental load, is expected to increase in the future. NKK considers its new NGH production system to be a key technology in the economical development of smaller, untapped gas fields and an important complement to today's LNG-based transport and storage systems. The company will continue to develop the technology with a goal of early commercialization.