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Alternative Fuels for Transportation
savings for the engine and emissions control system. NO x emissions can be
made quite low without exhaust gas after treatment, and it may be possible to
satisfy emissions standards with only EGR. In that case, the only exhaust gas
treatment necessary would be a passive oxidation catalyst for CO and possibly unburned organic compounds. If needed, the exhaust could be treated
with a Selective Catalyst Reduction (SCR), as used on modern diesel engines.
Due to the attractive emissions characteristics, the requirements of the SCR
system for a DME engine would be less demanding than for a diesel engine.
The engine fuel tank for DME would have to be larger than for diesel, and
more expensive due to the pressurization. There are factors acting to both
increase and decrease the cost of the engine system relative to diesel. All
factors considered, it does not appear that a DME engine system would not be
much more expensive than a diesel, and depending on emissions standards,
possibly cheaper. Ideally, an existing engine could be converted to run on DME
by changing the fuel system, but the sensitivity of the performance to the incylinder air flow interaction with the fuel spray makes a retrofit application
less attractive than an engine designed to run on DME from the start.
6.5.2 industrial/gas Turbine
The areas where special consideration for DME needs to be taken are in the
fuel handling system and in particular the fuel injection nozzle. In terms of
fuel handling, the question of seals and elastomer compatibility is again relevant. A new fuel injection nozzle would be needed for DME. Studies have
shown that this is a reasonably straight forward task (JDF 2007), and it is
possible to design a compatible fuel injection nozzle with existing air flow
motion in the burner. Thus, retrofitting is a good possibility for changing to
DME in these applications. In a new application, DME equipment and that
for LNG, LPG, or fuel oil should be of approximately the same cost.
6.5.3 Domestic use
The economic impact of DME in domestic use depends on whether it is used
as an LPG extender or as a neat fuel. In the former case, current results indicate that existing systems can be used without change, so there is no economic effect of using DME in LPG up to about 20% other than fuel cost,
which appears to be competitive, possibly cheaper, depending on crude oil
prices. For pure DME systems, the nozzles in burners need to be changed to
accommodate the different fuel air ratio requirements, and plastics and seals
probably need to be changed. Cost is very design dependent, but converting
an existing system to DME would require some investment at the user level,
though retrofitting is a real possibility here. It appears to be attractive to use
neat DME in newly constructed systems, where the replacement/rebuilding
question is not relevant. New equipment for neat DME is not expected to cost
more than the corresponding equipment for LPG.
Alternative Fuels for Transportation
savings for the engine and emissions control system. NO x emissions can be
made quite low without exhaust gas after treatment, and it may be possible to
satisfy emissions standards with only EGR. In that case, the only exhaust gas
treatment necessary would be a passive oxidation catalyst for CO and possibly unburned organic compounds. If needed, the exhaust could be treated
with a Selective Catalyst Reduction (SCR), as used on modern diesel engines.
Due to the attractive emissions characteristics, the requirements of the SCR
system for a DME engine would be less demanding than for a diesel engine.
The engine fuel tank for DME would have to be larger than for diesel, and
more expensive due to the pressurization. There are factors acting to both
increase and decrease the cost of the engine system relative to diesel. All
factors considered, it does not appear that a DME engine system would not be
much more expensive than a diesel, and depending on emissions standards,
possibly cheaper. Ideally, an existing engine could be converted to run on DME
by changing the fuel system, but the sensitivity of the performance to the incylinder air flow interaction with the fuel spray makes a retrofit application
less attractive than an engine designed to run on DME from the start.
6.5.2 industrial/gas Turbine
The areas where special consideration for DME needs to be taken are in the
fuel handling system and in particular the fuel injection nozzle. In terms of
fuel handling, the question of seals and elastomer compatibility is again relevant. A new fuel injection nozzle would be needed for DME. Studies have
shown that this is a reasonably straight forward task (JDF 2007), and it is
possible to design a compatible fuel injection nozzle with existing air flow
motion in the burner. Thus, retrofitting is a good possibility for changing to
DME in these applications. In a new application, DME equipment and that
for LNG, LPG, or fuel oil should be of approximately the same cost.
6.5.3 Domestic use
The economic impact of DME in domestic use depends on whether it is used
as an LPG extender or as a neat fuel. In the former case, current results indicate that existing systems can be used without change, so there is no economic effect of using DME in LPG up to about 20% other than fuel cost,
which appears to be competitive, possibly cheaper, depending on crude oil
prices. For pure DME systems, the nozzles in burners need to be changed to
accommodate the different fuel air ratio requirements, and plastics and seals
probably need to be changed. Cost is very design dependent, but converting
an existing system to DME would require some investment at the user level,
though retrofitting is a real possibility here. It appears to be attractive to use
neat DME in newly constructed systems, where the replacement/rebuilding
question is not relevant. New equipment for neat DME is not expected to cost
more than the corresponding equipment for LPG.