Outline of technology
1.Background and process outline
Dimethylether (DME) is a clean energy source of low environmental load, generating no sulfur oxide or soot during combustion. Owing to the non-toxicity and easy liquefaction properties, DME is easy in handling, thus it can be used as domestic-sector fuel (substitute for LPG), transportation fuel (diesel vehicle, fuel cell automobile), power plant fuel(thermal plant, cogeneration plant, fuel cell), and raw material for chemical products.
Currently DME is produced by dehydration of methanol at amount of about 10 thousand tons a year in Japan, and 150 thousand tons a year in the world. The main use of DME is spray propellant. If the supply of DME is available in large amount at low price, DME is expected to be used as fuel in wide fields owing to the above-described superior properties.
2.Development object and technology to be developed
The object of the study is the development of direct synthesis process of DME from syngas (mixed gas of H2 and CO), (reaction (1)).
The DME production through the dehydration of methanol, (reaction (3)), is the existing technology. The plant scale under actual operation, however, is rather small, and the scale up is an issue to produce DME commercially for fuel service. In addition, the equilibrium conversion of the methanol synthesis reaction (2) is relatively small as show in Fig.1.
On the other hand, in the direct DME synthesis reaction (1) because the limitation of equilibrium of methanol synthesis is avoidable the conversion is higher than that of methanol synthesis.
The reaction formulae relating to the direct DME synthesis are given below. The equilibrium conversion of methanol synthesis and of direct DME synthesis is given in Fig. 1.
Since the direct synthesis gives maximum conversion at H2/CO=1 of the syngas composition, the process is suitable for the syngas produced from coal gasification (H2/CO=0.5-1). The targets of the development study include the following.
<1.DME production rate: 100 ton/d or more, Syngas total conversion: 95% or more, DME selectivity: 90% or more, DME purity: 99% or more
2. Establishing scale up technology 3. Optimization of total system 4. Establishing stable plant operation >
(1) 3CO+3H2 CH3OCH3+CO2
(2) CO+2H2 CH3OH (3) 2CH3OH CH3OCH3+H2O
Fig. 1 Equilibrium conversion (280OC, 5Mpa) 40 20 60 80 100 0.0 0.5 H2/CO ratio [-] H 2 +CO conversion [%] (2) CO + 2H2 CH3OH (1) 3CO + 3H2 CH3OCH3 + CO2
1.0 1.5 2.0 2.5 3.0
In charge of research and development:DME Development Co., Ltd. (The company was established in 2001 in collaboration of following-listed
ten companies aiming to establish the technology of direct synthesis of DME.), JFE Holdings Co., Ltd.; Nippon Sanso Corp.;
Toyota Tsusho Corp.; Hitachi Ltd.; Marubeni Corp.; Idemitsu Kosan Co., Ltd.; INPEX Corporation; TOTAL S.A.(France); LNG Japan Co., Ltd.; and Japan Petroleum Exploration Co., Ltd.(JAPEX)
Project type: National Grant project of "Development of Technology for Environmental Load Reducing Fuel Conversion" of the
Agency of Natural Resources and Energy of the Ministry of Economy, Trade and Industry
4.Issue and feasibility of practical application
DME is already utilized as a fuel at inland area of China in small scale. In Japan, activities toward the practical application of DME as fuel are in progress at: DME International Co., Ltd. which was established by the same ten companies of DME Development Co., Ltd. aiming at the study for Commercialization of DME; Japan DME Co., Ltd. which was established by four companies, namely, Mitsubishi Gas Chemical Co., Inc., Mitsubishi Heavy Industries, Ltd., JGC, and Itochu Corp.; Mitsui & Co., Ltd. and Toyo Engineering Corp.; (the last two adopted the methanol dehydration process). These activities aim to supply DME product in 2006. All of them plan to use natural gas as the raw material, because natural gas requires small initial investment. In
the future, however, they are supposed to switch the raw material to coal which is larger in reserves quantity than natural gas. In natural gas case, the CO2 obtained from CO2 separation column is returned to syngas generation furnace, but the same is released to atmosphere in coal case. When the CO2 storage technology in long term is established in future, the coal based process can provide purified CO2 without any additional facilities. Also in western world, DME draws attention in wide fields as a new fuel. They however, expect mainly to use in diesel vehicles to fully utilize the advantageous characteristic of no-generation of soot.
1) Tsunao Kamijo et al.: Lecture papers of The 8th Coal Utilization Technology Congress, Tokyo 1998, pp.194-205
2) Yotaro Ono et al.: Preprint for the lectures of the 30th Petroleum and Petrochemical Discussion Meeting, Tokyo 2000, pp.26-29 3) Yotaro Ono: Japan DME Forum Workshop 2002, Tokyo, pp.113-122
References
3.Progress and result of the development
The development of direct synthesis process has been led by JFE (ex-NKK). The first step is the search of direct synthesis catalyst. The second step is the small bench plant (5 kg/d). The third step is the pilot plant (5 ton/d) 1)2) constructed with the aid of the Ministry of Economy, Trade and Industry. The fourth step is the demonstration plant (as large as 100 ton/d) constructed also
with the aid of the Ministry of Economy, Trade and Industry. The construction of demonstration plant finished in November 2003, and the operation is scheduled to start at the end of 2003 to conduct five runs of long period continuous operations (2 to 3 months) until 20063).
Photo 1 5 ton/d pilot plant Photo 2 100 ton/d demonstration plant
Fig. 2 Typical process flow diagram of DME direct synthesis plant from coal or natural gas
Steam Oxygen Coal Coal mine methane
Natural gas
CO2 CO2
Synthesis gas generation furnace Gas purification column DME synthesis reactor CO2 separation column
Liquid/gas separator
Reaction condition 250~280OC
3~7Mpa
DME purification column
Non-reacted gas
Methanol Purge gas
CO,CO2,H2