A well-to-wheel LCA shows that OME1could serve as an almost carbon-neutral blending component in diesel while even also strongly reducing the NOx and soot emissions.

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Three-step procedure for early-stage evaluation of CO2 utilization technologies based on TRLs.

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Oxymethylene dimethyl ethers (OMEn) are potential compression ignition fuels or blend components that enable drastic reductions in pollutant formation. By combining multiple conversion steps, OMEn can be produced from carbon dioxide (CO2) and hydrogen (H2) and hence from renewable electricity. However, established processes for OMEn production are challenging to model and detailed analyses of OMEn production from H2 and CO2 are not yet available in the open literature. In the first part of our two-part article, state-of-the-art models for the formaldehyde-containing mixtures involved in OMEn production are implemented in AspenPlus and used to analyze a process chain for production of OME1 from H2 and CO2 via methanol and aqueous formaldehyde solution. The exergy efficiency of the process chain is 73%. Tailored processes aiming at improved heat and mass integration as well as novel synthesis routes leading to reduced process complexity or avoiding oxidative intermediate steps hold significant promise for future efficiency improvements.

Oxy-fuel combustion of sour gas, a mixture of natural gas (essentially methane (CH 4 )), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S), could enable the utilization of large natural gas resources, especially when combined with enhanced oil recovery. In this work, a detailed chemical reaction mechanism for oxy-fuel combustion of sour gas is presented. To construct the mechanism, a CH 4 sub-mechanism was chosen based on a comparative validation study for oxy-fuel combustion. This mechanism was combined with a mechanism for H 2 S oxidation, and the sulfur sub-mechanism was then optimized to give better agreement with relevant experiments. The optimization targets included predictions for the laminar burning velocity, ignition delay time, and pyrolysis of H 2 S, and H 2 S oxidation in a flow reactor. The rate parameters of 15 sulfur reactions were varied in the optimization within their respective uncertainties. The optimized combined mechanism was validated against a larger set of experimental data over a wide range of conditions for oxidation of H 2 S and interactions between carbon and sulfur species. Improved overall agreement was achieved through the optimization and all important trends were captured in the modeling results. The optimized mechanism can be used to make qualitative and some quantitative predictions on the combustion behavior of sour gas. The remaining discrepancies highlight the current uncertainties in sulfur chemistry and underline the need for more accurate direct determination of several important rate constants as well as more validation data.

Oxymethylene dimethyl ethers (OME n ) have high potential as diesel fuels or blending components due to their promising combustion properties and can be produced from hydrogen (H2) and carbon dioxide (CO2) by combining existing process concepts. However, such a process chain has not been analyzed in detail yet, so its performance and bottlenecks are unknown. In this second part of our two-part article, we analyze a process chain for production of the longer chain variant OME3–5 from renewable H2 and green CO2 via trioxane and OME1. We simulate in Aspen Plus using detailed thermodynamic models with coupled oligomerization reactions and rigorous unit operation models. The overall exergy efficiency of OME3–5 production from H2 and CO2 using established process concepts is 53%. Therein, the trioxane process step has the highest losses due to its high heat demand. Considering a pinch-based heat integration throughout the entire process chain its total heat demand can be reduced by 16%. Thus, the exergy efficiency increases to 54%. This is still significantly lower compared to the production of other alternative fuels like OME1, methane, and dimethyl ether. Thus, more efficient processes, e.g., by avoiding trioxane production, are required.

Sour gas is an unconventional fuel consisting mainly of methane (CH 4 ), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S) that constitutes a considerable, currently untapped energy source. However, little is known about its combustion characteristics. In this work, we used our recently assembled and validated detailed chemical reaction mechanism to examine some of the combustion properties of sour gas with different compositions in both conventional air combustion and oxy-fuel combustion, the latter being motivated by application in carbon capture and storage. The calculations suggest that raising the H 2 S content in the fuel leads to relatively small changes in the flame temperature and laminar burning velocity, but a considerable reduction in the ignition delay time. At elevated pressures, H 2 O diluted oxyfuel combustion leads to higher burning velocities than CO 2 diluted oxy-fuel combustion or air combustion. Mixed CH 4 /H 2 S flames exhibit a two-zone structure in which H 2 S is oxidized completely to sulfur dioxide (SO 2 ) while CH 4 is converted to carbon monoxide (CO). Formation of corrosive sulfur trioxide (SO 3 ) mainly occurs during CO burnout.