EMS
The Energy Institute
Dimethyl Ether - A Path to Use Natural Gas as a
Transportation Fuel
André Boehman
EMS Energy Institute
Department of Energy & Mineral Engineering
The Pennsylvania State University
Partners:
Oberon Fuels
Alternative Fuel Technology, LLC
EMS
The Energy Institute
Why Consider DME?

Natural gas vehicles are of great public and commercial interest 
direct displacement of petroleum from a domestic resource

Efficient utilization of natural gas should be our goal

But in what form? HCNG, CNG, LNG, or conversion to other fuel
chemistry for more efficient usage?

Dimethyl ether represents an emerging engine technology for NG
utilization.

Infrastructure build-out can piggyback on current LPG
infrastructure

Handles like propane

Burns smokeless  eliminates diesel particulate matter concerns

Won’t boil off if your vehicle sits for two weeks
EMS
The Energy Institute
J. Eberhardt, DEER 2002
DME 61% the energy content
of propane
Similar energy content
to ethanol on volume basis
EMS
The Energy Institute
Comparison of Emissions of Low Emissions Vehicle-Certified RTD Buses
Vehicle
Cycle
THC (g/mi) NMHC
(g/mi)
NOx
(g/mi)
CO (g/mi)
CO2
(g/mi)
PM
(g/mi)
Btu/mi
RTD Bus 1014-CNG
CBD
20.04
2.19
9.06
0.34
1690
0.02
27018
RTD Bus 1011Diesel
CBD
0.18
-----
16.12
11.18
1785
1.02
22908
McCormick, Graboski, Alleman, Herring and Nelson, SAE 1999-01-1507
~ 3090
1890 g/mi at 70*GWP
2090
10*GWP of CH4
20*GWP

CNG Vehicles Suffer From:
 Reduced compression ratio  lower thermal efficiency
 High unburned CH4 emissions
 Combination of high CH4 emissions and reduced efficiency eliminates the
H/C ratio benefit of CNG over diesel fuel with respect to CO2eq emissions
EMS
The Energy Institute
CNG Vehicle Efficiency

1990’s:
 Thomas and Staunton (SAE 1999-01-1511) state DOE target is 10% > fuel
economy than equivalent gasoline vehicle, but > 15% improvements are
possible with turbocharged lean-burn operation. Alternative is CI NG
engines, using diesel pilot, and recommended port gas injectors or DI NG
injectors, and maybe a prechamber to enhance ignition. Diesel efficiency
requires DI or IDI for the NG and provide >28 to 37% efficiency gain over
gasoline. Their analysis was restricted to conventional combustion – dual
fuel with micropilot or CI of the NG.
 Weaver and Turner (SAE 940548) show that knock can occur in high BMEP
engines, leading to derating of the engine to avoid knock or reduction of
the fraction of energy from NG. At light load the very lean mixture may
prevent effective burning of the homogeneous NG charge unless the
engine is throttled.
Can we “burn” natural gas and have diesel or better efficiency?  consider DME
“Synthetic LPG”
DME Background
What
is DME?
What is DME?
Methanol
Methane
Patron
member
Patron
member
Propane
LPG
Butane
Dimethyl-ether
(DME)
Water
1.4 tons MeOH to 1 ton DME
Hydrogen
Carbon
Oxygen
DME Properties –
Comparison with Other Fuels
Property
DME
Diesel
Propane
Chemical Formula
C2H6O
C10.8 H18.7
C3H8
Molecular Weight
46.07
148.6
44.11
Critical Temperature- C
127
-
95.6
Boiling Point- C
-24.9
71-193
-42.1
Vapor Pressure at 20 C-kg/m2
5.1
<0.01
8.4
Critical Pressure-bar
53.7
-
43
Liquid Viscosity- cP
.15
2-4
.10
Liquid Density at 20 C-kg/m3
668
800-840
501
Bulk Modulus (N/m2)
6.37E+08
1.49E+09
Specific Density,gas
1.59
-
1.52
Solubility in H2O at 20 C g/l
70
Negligible
.12
Lower Heating Value- kJ/kg
28430
42500
46360
Heat of vaporization- kJ/kg 20C
410
233
426
Explosion limit in air- vol%
3.4-17
1.0-6.0
2.1-9.4
Ignition temperature at 1 atm- C
235
250
470
Cetane Number
55-60
40-55
7
Factors Driving DME Fuels Growth –
Diesel Substitution
Opportunities






Can be used in conventional
diesel engines with a modified fuel
injection system
Large potential market
High cetane
Quiet combustion
Clean burning (sootless – no
smoke or particulates)
100% SOx reduction
Challenges
 Technical and regulatory hurdles
remain
 LPG-like distribution infrastructure
 Lower lubricity requires lubricating
agent
 Lower viscosity can cause
leakage
 Government regulations
Volvo DME Truck
8
Factors Driving DME Fuels Growth –
Diesel Substitution
Much Work Underway






Japan DME Vehicle Promotion
Committee
Volvo & BioDME Consortium
Shanghai Automotive Corp.
Alternative Engine Technology
Isuzu Advanced Engineering
Center
Nissan
SAIC DME Diesel
Engine
Isuzu DME Diesel Truck
Volvo DME Diesel Engine
Nissan NTSL DME Diesel
Truck
SAIC DME Diesel Bus
9
EMS
The Energy Institute
Technology Description
Developer of Fleet Scale DME Production System

DME at 3000-5000 gallons per day

Natural Gas and CO2 as feedstocks

Leaps over the “Valley of Death” due to small
scale production
R&D Support and Technology
Demonstration
Developer of Novel Fuel Injection Systems for DME

AFT fuel system technology is being adapted
for commercial heavy duty applications by
Volvo Group and Delphi

AFT fuel system can be scaled from lightduty to heavy-duty applications

Transportation Institute / Test
Track / Chassis Dyno

Combustion, Emissions and Fuel
Formulation
Oberon Fuels Process
Natural Gas + CO2
NG-DME
Syngas Methanol
DME
Biogas
Gas-to-Liquids Unit
Bio-DME
Technology
• Utilize proven components
and catalysts
• Benefit from the development of
small-scale hydrogen
production units
• 30% CO2 in feedstock and scale are well suited for
distributed waste biogas sources
• Innovations from Oberon focus on:
– Integration of modular components
– Process efficiency
– Centralized volume construction
World leader in DME fuel system innovation –
developed four generations of common rail fuel systems specifically designed for DME
Novel fuel pumps and fuel injectors
Novel fuel feed pump to send fuel
from the supply tank to the engine
EMS
The Energy Institute
Why Consider DME?

Because it makes sense on many levels:

Higher energy density than compressed natural gas

Will not vent due to evaporation over time

Does not need cryogenic storage

Ease of refueling (no venting, no compressors)

Diesel engine efficiency

Ultra low emissions with simple emissions controls

Monetizes “dry gas” in the Marcellus Shale
 Natural gas is selling at less than $2.50 per equivalent diesel gallon
(Jan. 2012, DOE Clean Cities Alternative Fuel Price Report
 January 2012
 DME is anticipated to sell at $3 per equivalent diesel gallon
 Represents an increase in the value of the natural gas
This team has the capability to bring DME and DME engines to market cost-effectively