NKK Corp., Taiheiyo Coal Mining Co., and Sumitomo Metal Industries Ltd. say they synthesized dimethyl ether (DME) from coal-bed methane in October 1999.
The companies ran a 300-hr trial run in their 5 tonne/day Kushiro, Japan, test plant (Fig. 1). After 1 week, the test produced 80% of the designed capacity of DME at a purity of 97%. Also, no deterioration was detected in catalyst activity during the trial run.
After optimization of distillation conditions, the three companies expect at least 99% DME purity.
May reduce emissions
Today, DME is made from methanol dehydrogenation and mainly used as aerosol propellants in spray cans. Use as a diesel-engine fuel in the future, however, will help prevent global warming by reducing methane emissions into the atmosphere.
DME makes a good diesel substitute because it is has no sulfur, which reduces NOx emissions, and is high in cetane number (55-60). Comparatively, diesel has a cetane number of 40-55.
The fuel efficiency of DME-fueled diesel engines, says NKK, is the same as that of gas oil without any black smoke. Use of DME requires modifications to the fuel-injection pump and fuel tanks of conventional diesel vehicles, however. NKK says it expects these mechanical alterations to be of minimal cost.
Plant units consist of a synthesis gas production and purification system, a 20 m high DME synthesis reactor, and DME purification columns. Besides coal-bed methane, the process can use low-grade coal or natural gas for feed. Mass production of DME through the new method is expected to push down the DME price to around 40 yen/kg from the current 200 yen.
The partners plan further tests in June and July 2000 and a 2-month continuous operation trial in September and October 2000. Lessons learned from these tests will contribute to design of a future 500 tonne/day commercial plant.
The companies will start exporting their DME production facilities to China as early as 2005, officials at the three companies say. DME synthesis could use coal-bed methane that China and other countries would otherwise release to the atmosphere.
