Dimethyl ether as Zero Emission Fuel. Synergies with Biogas and Biomass Plants

Rapport Technique , 2018 , 7 Pages

Sciences de l'énergie

In Iceland a methanol plant named in honor of the noble prize laureate George Olah operating since 2011. As substrate they use carbon dioxide and hydrogen producing methanol. Methanol is the simplest alcohol and well know since the developments of Paul Sabatier and the catalysis processes, in liquid phase at environment pressure and temperature, and is a synthetic alcohol. In the Georg Olah Plant carbon dioxide and hydrogen are mixed 1mol:3 mol together to form a syngas, being compressed and transformed under the help of catalysts to methanol (methanol synthesis). In most processes the methanol synthesis is running at a pressure range 30 bar up to 100bar and a temperature range 200°C up to 400°C. The conversion rate is given in the range of 25% up to 35% and therefor recycling of the unconverted gas in the methanol reactor back, to increase the conversion rate of synthetic gas and production rate.

Dimethyl ether as Zero Emission Fuel – Synergies with Biogas and Biomass Plants

Johann Gruber-Schmidt

Introduction

In Iceland a methanol plant named in honor of the noble prize laureate George Olah [4] operating since 2011. As substrate they use carbon dioxide and hydrogen producing methanol. Methanol is the simplest alcohol and well know since the developments of Paul Sabatier and the catalysis processes [3], in liquid phase at environment pressure and temperature, and is a synthetic alcohol. In the Georg Olah Plant [7] carbon dioxide and hydrogen are mixed 1mol:3 mol together to form a syngas, being compressed and transformed under the help of catalysts to methanol (methanol synthesis). Abbildung in dieser Leseprobe nicht enthalten. In most processes the methanol synthesis is running at a pressure range 30 bar up to 100bar and a temperature range 200°C up to 400°C. The conversion rate is given in the range of 25% up to 35% and therefor recycling of the unconverted gas in the methanol reactor back, to increase the conversion rate of synthetic gas and production rate. Leaving

Abbildung in dieser Leseprobe nicht enthalten

Figure 1: Methanol and Dimethyl ether from Carbon dioxide and water (Source: Johann Gruber-Schmidt 2017)

the methanol reactor the product gas will be cooled down and the condensate mixture of water and methanol is distilled and separated into water and product methanol. The methanol synthesis with carbon dioxide hydrogen is needed, generated by wet electrolysis Abbildung in dieser Leseprobe nicht enthalten from water and the electric power needed for the electrolysis is generated by geothermal heat conversion to electricity. This is a special property of Iceland. Now the question arises, where does the carbon dioxide come from? In the most common case carbon dioxide is separated from exhaust gas from fossil fueled power plants and industrial processes. Using fossil carbon dioxide in plant process the George Olah plant [7] is now accelerating the consumption of fossil fuels if we use methanol as a fuel. Therefor methanol should be used in chemical industry fixing carbon dioxide [4]. But if we use methanol as fuel in transportation, the combustion of methanol leads to carbon dioxide and water being transferred to the environment back. Abbildung in dieser Leseprobe nicht enthalten Normally carbon dioxide transferred to the environment is a dilution of carbon dioxide in the air. We watch that methanol burned in a classical Otto motor cycle additional produces compared to fossil diesel fuel in a diesel engine higher pollution, dust, soot and a higher amount of carbon dioxide in the exhaust gas. Therefor methanol is converted to dimethyl ether by extraction of water under acid conditions. [5,6]Abbildung in dieser Leseprobe nicht enthalten. Dimethyl ether is often mentioned as the ideal Diesel fuel [8], tested over long years from VOLVO [2] and by MACK TRUCK [1] in heavy trucks on the road. Dimethyl ether is the simplest ether a synthetic fuel, certificated by the ISO 16 681:2013 by the IDA, produced from methanol or by direct synthesis Abbildung in dieser Leseprobe nicht enthalten.

Abbildung in dieser Leseprobe nicht enthalten

Figure 2: MACK TRUCK testing Dimethyl Ether (Source: 24.01.2017 – Press Release from volvogroup.com)

In most cases there is no application of methanol in transport, civil, agriculture and forestry, because they are running on fossil diesel.

Heavy strong robust power machines are needed and the diesel engine is the ideal power machine. Methanol cannot substitute fossil diesel directly. But dimethyl ether has this needed property. As shown from MACK TRUCK (New York) [1] testing Dimethyl ether in heavy trucks [1]. Since VOLVO (Sweden) [2] started in using Dimethyl ether in heavy trucks in 2008, running over five years the trucks on the road, and moved then to the USA at MACK TRUCK [1], it is well known that dimethyl ether is a story of success and dimethyl ether is the ideal Diesel fuel [1,2].

Abbildung in dieser Leseprobe nicht enthalten

Figure 3: VOLVO HEAVY TRUCK – running with Dimethyl Ether (Source: 01.06.2012 – Press Release from volvogroup.com)

Ethanol, Biodiesel

Using corn from agriculture bioethanol is produced with fermentation. Corn is a food product not agricultural waste. Bioethanol has the same combustion and emission problem as methanol: it can only be used in a gasoline engine and leads to higher pollution, lower efficiency, soot dust, and high carbon dioxide than dimethyl ether. In Europe biodiesel is mixed with fossil diesel. Biodiesel is produced from oil and fatties over catalytic esterification, but again biodiesel has the same combustion problem as methanol: although biodiesel can be used in diesel engines, biodiesel leads to higher pollution, lower efficiency, soot dust, and high carbon dioxide than dimethyl ether [2].

Biogas

The anaerobic fermentation process enables to produce biogas, consisting of methane and carbon dioxide (CH4, CO2). Biogas can be produced from wet biogenic waste. The anaerobic process can be realized in wet phases or in dry phases but always lead to biogas and digestate, which can be recycled again. In most application biogas is used to generate electricity and heat. The electric efficiency of biogas engines is 30% up to 36%, and we have an exhaust gas, therefore no zero emission.

Forestry Biomass

In Forestry wood is used for pulp and paper and for wood in civil and industry. Generating heat from wood chips with a warm water boiler is well known. In the most application biomass is used to generate heat. The thermal efficiency is low 75% up to 85%, and we have an exhaust gas and again no zero emission.

Reforming and Gasification for Dimethyl ether

Dimethyl ether can be produced from biogas and biomass. Biomass as waste biogenic mass can be used for gasification to generate synthetic gas and char coal. The char coal is carbon, the synthetic gas consists of CO:23%, H2:20%, CH:1%, O2< 0.1%, CxHy: 3%, Rest CO2. The heat caloric value is about 1.5 kWh/m³. Charcoal can be reused again and converted to syngas over the known water gas reaction: Abbildung in dieser Leseprobe nicht enthalten. Biogas can be used to generate synthetic gas with dry reforming: Abbildung in dieser Leseprobe nicht enthalten .The synthetic gas consists of CO:40%, H2:40%, CH:3%, O2< 0.1%, CxHy: 1%, Rest CO2. The heat caloric value is about 2.5 kWh/m³. In both cases syngas can be transformed to dimethyl ether over direct synthesis: Abbildung in dieser Leseprobe nicht enthalten. [8].

Hydrogen

Cheap hydrogen is the basic requirement for the production of cheap and competitive dimethyl ether from methanol. Hydrogen from electrolysis costs electric power ~5.0 kWh/m³ H2. Hydrogen generated from waste heat, enables to split water into hydrogen and oxygen with metals at temperatures from 400°C up to 800°C: Abbildung in dieser Leseprobe nicht enthalten .

Abbildung in dieser Leseprobe nicht enthalten

Figure 4: Dimethyl Ether Application with SOFC Cells (Solid Oxide Fuel Cell) (Source: Johann Gruber-Schmidt 2017)

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• Cours: Erneuerbare Treibstoffe
• Auteur: Dr. techn. Johann Gruber-Schmidt (Auteur)
• Année de publication: 2018
• Pages: 7
• N° de catalogue: V434507
• ISBN (ebook): 9783668761773
• ISBN (Livre): 9783668761780
• Langue: allemand
• mots-clé: dimethyl, zero, emission, fuel, synergies, biogas, biomass, plants