173
Dimethyl Ether
6.3 DME Production
6.3.1 Syngas Production
DME is not found naturally, and must be produced by a chemical process
from a feedstock containing carbon and hydrogen. For fuel use, two basic
options exist, but they are both based on the use of syngas. Syngas is a mixture of primarily H 2 , CO, and some other gasses resulting from the high
temperature gasification of organic compounds. The generation of syngas
is a key element in the production of DME, and a range of other chemicals
such as ammonia, methanol, propylene, and synthetic diesel fuel from carbon containing compounds. For current DME production proposals, natural
gas and coal are the most commonly named feedstocks. Biomass from the
paper industry is also being investigated for DME production in a more CO 2
neutral fashion (Landälv 2006).
For syngas production from natural gas, there are two types of syngas
generators: the steam reformer and the autothermal reactor (Hansen et al.
1995). In the former, steam is mixed with the natural gas and the mixture is
passed over a catalyst in a reactor to form the syngas. The catalyst typically
is enclosed in tubes, and these are externally heated. The overall reaction
occurring with steam reforming is
CH + H O → CO + 3H ∆H = 131 2 kJ/kMol − CH
.
.
(6.1)
4
2
2
R
4
Steam reforming produces a syngas that is high in hydrogen. This is beneficial in the case of formation of methanol. It is also possible to reform with
carbon dioxide:
CH + CO → 2CO + 2H ∆H = 246 8 kJ/kMol − CH
.
.
(6.2)
4
2
2
R
4
The syngas produced with this method has equal amounts of hydrogen and
carbon monoxide. As shown later, this is the stoichiometric mixture for the
overall formation of DME from syngas. The syntheses of methanol and DME
are dependent on the relative amounts of hydrogen and carbon monoxide
in the syngas, and there are syngas production processes using both of the
above reactions.
In the autothermal reactor, which is used for natural gas, there is a partial combustion of the feedstock, with about 35–40% of the stoichiometric
amount of an oxidizer. For DME production, oxygen is the most common
oxidizer used. The use of air would involve the introduction of a large
amount of nitrogen to the gasifier system, which would greatly increase gas
flow rates through the systems without giving any production benefit. In the
autothermal reactor, the rich combustion occurs in the presence of a suitable
Dimethyl Ether
6.3 DME Production
6.3.1 Syngas Production
DME is not found naturally, and must be produced by a chemical process
from a feedstock containing carbon and hydrogen. For fuel use, two basic
options exist, but they are both based on the use of syngas. Syngas is a mixture of primarily H 2 , CO, and some other gasses resulting from the high
temperature gasification of organic compounds. The generation of syngas
is a key element in the production of DME, and a range of other chemicals
such as ammonia, methanol, propylene, and synthetic diesel fuel from carbon containing compounds. For current DME production proposals, natural
gas and coal are the most commonly named feedstocks. Biomass from the
paper industry is also being investigated for DME production in a more CO 2
neutral fashion (Landälv 2006).
For syngas production from natural gas, there are two types of syngas
generators: the steam reformer and the autothermal reactor (Hansen et al.
1995). In the former, steam is mixed with the natural gas and the mixture is
passed over a catalyst in a reactor to form the syngas. The catalyst typically
is enclosed in tubes, and these are externally heated. The overall reaction
occurring with steam reforming is
CH + H O → CO + 3H ∆H = 131 2 kJ/kMol − CH
.
.
(6.1)
4
2
2
R
4
Steam reforming produces a syngas that is high in hydrogen. This is beneficial in the case of formation of methanol. It is also possible to reform with
carbon dioxide:
CH + CO → 2CO + 2H ∆H = 246 8 kJ/kMol − CH
.
.
(6.2)
4
2
2
R
4
The syngas produced with this method has equal amounts of hydrogen and
carbon monoxide. As shown later, this is the stoichiometric mixture for the
overall formation of DME from syngas. The syntheses of methanol and DME
are dependent on the relative amounts of hydrogen and carbon monoxide
in the syngas, and there are syngas production processes using both of the
above reactions.
In the autothermal reactor, which is used for natural gas, there is a partial combustion of the feedstock, with about 35–40% of the stoichiometric
amount of an oxidizer. For DME production, oxygen is the most common
oxidizer used. The use of air would involve the introduction of a large
amount of nitrogen to the gasifier system, which would greatly increase gas
flow rates through the systems without giving any production benefit. In the
autothermal reactor, the rich combustion occurs in the presence of a suitable