| 1. |
- Gandiglio, Marta, et al.
(författare)
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Solutions for improving the energy efficiency in wastewater treatment plants based on solid oxide fuel cell technology
- 2020
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Ingår i: Journal of Cleaner Production. - : ELSEVIER SCI LTD. - 0959-6526 .- 1879-1786. ; 247
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Tidskriftsartikel (refereegranskat)abstract
- Polygeneration configurations for small power generation systems offer significant potential for energy saving and reducing carbon emissions in wastewater treatment facilities. In this work, a biogas-fed solid oxide fuel cell system operating in a wastewater treatment plant (located in Turin, Italy) is analyzed in terms of its potential improvements through novel polygeneration systems. In its present combined heat and power configuration, along with electrical power, thermal energy from the exhaust gas is recovered to provide required heat to the plant's anaerobic digester. The analysis is focusing on different energy efficiency solutions for this type of plant by using solar thermal collectors, microturbines, a trilateral Rankine cycle, and an absorption chiller. Results reveal that, despite of higher efficiency for the trigeneration case using both trilateral Rankine cycle and absorption chiller (up to 88.4%), the solar integrated system results in the lowest natural gas consumption, which is 38.5% lower than the baseline scenario. This same scenario is also the worst in economic terms due to the high capital costs of solar collectors. In a short-term cost trajectory of the solid oxide fuel cell technology, the most economically favorable scenario is the microturbine integrated case in which the calculated levelized cost of electricity is 0.11 (sic)/kWh, lower than grid electricity price, and with payback time of 6.5 years. Long-term cost trajectory is indeed generating effective investments for all of the four scenarios with payback time between 3 and 5 years in all cases. The analysis has been developed to the entire European Union area: the most suitable market conditions are found in Germany, Denmark, Slovakia, and Italy.
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| 2. |
- Lorenzi, Guido, et al.
(författare)
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Digester Gas Upgrading to Synthetic Natural Gas in Solid OxideElectrolysis Cells
- 2015
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 29:3, s. 1641-1652
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the process design and performance of an innovative plant for digester gas upgrading tosynthetic natural gas (SNG). The differences and advantages over traditional upgrading processes are discussed. The mainstrength of digester gas upgrading via high-temperature electrolysis concerns its higher synthetic natural gas productivity for agiven raw digester gas feed. Electrolysis is performed through a solid oxide electrolysis cell (SOEC) system, which is fed withdemineralized water and purified digester gas (made up of methane and carbon dioxide). Surplus electricity from intermittentrenewable energy sources is used to supply the energy required for the SOEC stacks. The resulting methane-rich syngas isreacted in a series of methanators to yield a high CH4 content output stream. The steam reforming reaction is promoted bymeans of a nickel catalyst in the cathode (fuel) electrode, which reduces the methane fraction: hence, sulfur, which is present inseveral types of digester gas (e.g., from sewage or landfills) in the form of hydrogen sulfide, has been identified as a possibleinhibitor for this reaction. However, it is also well-known that sulfur is responsible for the deterioration of the electrochemicalperformance of a stack. Therefore, its effect on the system has been modeled for different thermodynamic conditions. This studyanalyses the electrochemical and energy performance of the integrated process through which all the carbon contained in digestergas is converted/upgraded to methane-rich gas. The electrochemical dissociation of the CO2 contained in the digester gas to CH4(with the addition of external demineralized water) is one way of cleverly exploiting the carbon content in digester gas when poorquality or limited biological substrates are available for anaerobic digestion. Finally, a comparison with other commercial digestergas upgrading techniques has been made.
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| 3. |
- Lorenzi, Guido, et al.
(författare)
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Exergo-economic analysis of a direct biogas upgrading process to synthetic natural gas via integrated high-temperature electrolysis and methanation
- 2017
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 141, s. 1524-1537
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Tidskriftsartikel (refereegranskat)abstract
- Biogas upgrading to synthetic natural gas (SNG) is a viable and appealing route for power-to-gas because it combines waste management with the use of the surplus electricity that might arise in energy systems having a considerable share of renewable energy sources in their production mix. In this work, the exergo-economic performance of a biogas upgrading process through integrated electrolysis and methanation is assessed in connection with the current market status to test which conditions could make the proposed option economically viable. Two different configurations, which differ mainly for the operating pressure of the electrolyser, are compared. The exergy efficiencies are high (>80%) and exergo-economic costs of the produced bio-SNG in the two analyzed configurations are 5.62 and 4.87 c(sic)/kWh(exergy), for low- and high-pressure respectively. Lower values would be required for the bio-SNG to compete with fossil natural gas. We show how both the input electricity price and the capacity factor have a substantial impact on the economic sustainability of the process. Eventually, the monetary exploitation of the oxygen produced by electrolysis and the participation to the emission trading scheme could contribute further to improve the economic attractiveness of the process.
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| 4. |
- Marchese, Marco, et al.
(författare)
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Techno-economic feasibility of a biomass-to-X plant : Fischer-Tropsch wax synthesis from digestate gasification
- 2021
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- A techno-economic analysis is performed, assessing the production costs of Fischer-Tropsch syncrude and waxes of carbon number C20+. The products are obtained from the gasification of digestate from anaerobic digestion inside a dual fluidized bed gasifier (3.11 MWth). The results are compared against the same system fed with lignocellulosic biomass. The syngas is cleaned from impurities and conditioned to reach the desired H-2/CO molar ratio of 1.8 at the inlet of the Fischer-Tropsch reactor. The Fischer-Tropsch products distribution is based on experimental data of a cobalt-based catalyst. Two process configurations are studied: (1) the Fischer-Tropsch off-gas are employed to produce electricity; (2) the off-gas are recirculated to the gasifier for enhanced wax production. Co-production of steam is also investigated. The results show an advantageous production of Fischer-Tropsch compounds utilizing digestate over wood biomass. The highest plant efficiency (i.e., biomass-to-liquid fuel) of 56.3% is reached with digestate feedstock and off-gas recirculation, outputting 61.5 kg(wax)/t(dig). The minimum wax production cost is of 3.04 (sic)/kg(wax), assuming 7.5% discount rate and 25-years plant operation.
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