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Jülich evaluation of power-to-fuels recommends DME, OME3-5 and n-alkanes as diesel substitutes

An evaluation of the implementation possibilities of power-to-fuel (PTF) technologies by a team from Forschungszentrum Jülich GmbH in Germany recommends the PTF products DME, OME3-5 and n-alkanes as suitable diesel alternatives for the transportation sector. PTF processes essentially use renewable energy, CO2 and water to produce fuel, as in Audi’s targeted e-fuels projects. (Earlier post.) A paper on the Jülich study is published in the journal Fuel.

The simplest implementation strategy for such electrofuels would be a gradual market penetration by means of blending with conventional diesel, the authors suggested. Potential blending combinations highlighted in the paper include: fossil diesel + n-alkane cut; fossil diesel + OME3–5; Fossil diesel + n-alkane cut + 3-5; and n-alkane cut + OME3–5. The last blend—a suitable n-alkane cut mixed with OME3-5—has the greatest potential for increasing engine efficiency and reducing pollutant emissions. In addition, fossil diesel would no longer be required.

Schemme
Power-to-fuel, interlinking the energy and transport sectors. Schemme et al. Click to enlarge.

The investigations reveal that the lower heating value of fuels containing O has no negative impacts on engine efficiency, not even in existing engines. The electrofuels examined have a significantly higher cetane number than fossil diesel, which usually promises potential for improved engine performance. Exhaust gas values were also greatly improved by the use of electrofuels. Since the tests of engine efficiency and exhaust gas values of all sources reviewed were conducted in test engines that had not been optimized for the used fuel, further potentials regarding emission reduction and the optimization of engine efficiency are expected. With regard to a conceivable implementation strategy, the critical aspects are, above all, viscosity as well as boiling, flash and melting temperatures. Suitable additives can mitigate any connected problems. The n-alkanes and OMEn used are usually not pure substances, but instead mixtures of molecules with different chain lengths. Their composition depends on the production process. Analyzing the potential of various OMEn as diesel fuels identifies OME3–5 as the most promising mixture.

—Schemme et al.

The researchers reviewed liquid fuel alternatives that could be used in existing vehicles in the transportation sector. Blend capability was a requirement—pushing methane aside for the purposed of their evaluation. The researchers subdivided their candidate fuels into three main groups:

  1. Hydrocarbons (olefins, paraffins, aromatics)
  2. Alcohols (methanol, ethanol,…)
  3. Ethers (DME, OMEn)

In addition to the properties in DIN EIN 590 (fossil diesel), the team considered:

  • Mixture formation with fossil diesel
  • Molecular structure
  • Heating value and air demand
  • Vaporization characteristics
  • Combustion characteristics, emissions
  • Social acceptance

Resources

  • Steffen Schemme, Remzi Can Samsun, Ralf Peters, Detlef Stolten (2017) “Power-to-fuel as a key to sustainable transport systems – An analysis of diesel fuels produced from CO and renewable electricity,” Fuel, Volume 205, 2017, Pages 198-221 doi: 10.1016/j.fuel.2017.05.061

Comments

Engineer-Poet

The failure to define or link to a definition of OME is a serious weakness of this article.

Darius

I totaly agree with Engineer-Poet. Would be interesting to know what this is about.
On other hand diagram is stupud since there is rationality behind regulating power consumtio by not producing fuel during day hours. Fuel production equipment standby cost could outweight power cost many many times both in money and enviromental terms.

Arnold

Had to translate from German, the translation worked a treat,but still above my pay grade.

https:
//de.wikipedia.org/wiki/Polyoxymethylendimethylether

OME (with n between 3 and 5) can be used as diesel fuel components or complete alternative [1] to diesel fuel. [2] [3] [4] [5] [6] This results in a reduction in soot emissions during the combustion process. [7] OMEs can also be used as physical solvents for CO 2 absorption from natural gases . [8] The production costs for the production of OME are comparable to the production of diesel fuel [9] .

OMEs can be produced from synthesis gas on various synthesizer outings. In a first process step, synthesis gas must be converted to methanol . This also usually produces dimethyl ether as a by-product. In a second step, methanol is oxidized to form formaldehyde .
The prior art is OME synthesis from the anhydrous intermediates methylal and trioxane . [10] [11] [12] [13] [14] Methylal is synthesized from methanol and formaldehyde. [15] Trioxan is synthesized from formaldehyde in aqueous solution and then purified to form an anhydrous product. [16] It is also possible to use methylal, dimethyl ether as the starting material. The reaction mixture is worked up by distillation."
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Always worry when Formaldehyde pops up. While domestic exposure to carcinogens is a fact of life and relative harms need to be weighed, that should not lead to avoiding the recognition of known hazards especially when complacency (potetially) leads to large increases in the exposure.
Workers are people too and workplace exposure risks matter.
As for example this
---------
"Study finds modern diesel cars emit fewer carbonaceous particulates than gasoline cars
14 July 2017"

http://www.greencarcongress.com/2017/07/20170714-psi.html

"They explained the absence of observed SOA from the DPF-diesels by the chemical composition of the THC emissions; while emissions from non-DPF-diesels chemically resemble diesel vapors, DPF-equipped-diesel exhaust comprises a large fraction (>70%) of short-chain oxygenated compounds, mainly *******formaldehyde and acetaldehyde, which are much less efficient SOA precursors than the aromatic species found in gasoline emissions."

https://en.wikipedia.org/wiki/Formaldehyde

"In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health.[12] In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen".[13][14][15]"
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