The effect of heavy tars (toluene and naphthalene) on the electrochemical performance of an anode-supported SOFC running on bio-syngas

The effect of heavy tar compounds on the performance of a Ni-YSZ anode supported solid oxide fuel cell was investigated. Both toluene and naphthalene were chosen as model compounds and tested separately with a simulated bio-syngas. Notably, the effect of naphthalene is almost negligible with pure H2 feed to the SOFC, whereas a severe degradation is observed when using a bio-syngas with an H2:CO = 1. The tar compound showed to have a remarkable effect on the inhibition of the WGS shift-reaction, possibly also on the CO direct electro-oxidation at the three-phase-boundary. An interaction through adsorption of naphthalene on nickel catalytic and electrocatalytic active sites is a plausible explanation for observed degradation and strong performance loss. Different sites seem to be involved for H2 and CO electro-oxidation and also with regard to catalytic water gas shift reaction. Finally, heavy tars (C>=10) must be regarded as a poison more than a fuel for SOFC applications, contrarily to lighter compounds such benzene or toluene that can directly reformed within the anode electrode. The presence of naphthalene strongly increases the risk of anode re-oxidation in a syngas stream as CO conversion to H2 is inhibited and also CH4 conversion is blocked

Creación en el diseño

Nos encontramos inmersos en un mundo en el cual fluye continuamente la Creación 'América se expresa diseñando', es ese pequeño mundo donde se reúnen los grandes del diseño y nosotros, los estudiantes, que somos diseñadores potenciales de ese ámbito que nos fascina, y nos hace descubrir días a día la riqueza interna que habita en la mente de cada uno y que necesita de tal o cual manera ser exteriorizada

Modeling of a stand-alone H2-based Energy Storage System for electricity production and H2 mobility

The application of renewable energy sources (RES) during the last decades is increasing, with the aim to reduce carbon dioxide emissions and develop more sustainable energy systems. Referring to isolated microgrids and off-grid remote applications, because of the non-continuous RES production, energy storage systems (ESSs) are necessary to make the energy supply reliable and reach the energy selfsufficiency. Among the possible EESs, hydrogen-based storage solutions integrating electrolysers to produce hydrogen from surplus renewable energy and fuel cells to generate power from the stored hydrogen (called Power-to-Power systems) can represent a promising solution. The present study has the aim to analyse, from a technical and an economical point of view, a hybrid Power-to-Power and Power-toHydrogen system for a mountain off-grid village. The hydrogen is utilized in fuel cells for power generation to provide the electrical load of the site and also for mobility for fuelling a FCEV minibus line. The aim of this work is to find the optimal system configuration, with the minimum Net Present Value (NPV) at the end of system lifetime. The Levelized Cost Of Energy (LCOE) and the Levelized Cost Of Hydrogen (LCOH) are also computed, to understand the economic viability for electricity and mobility loads, respectively. These values were derived using cost inputs from literature, and a comparative analysis is performed for different system configurations. Results from the energy simulations revealed that the need for an external source is significantly reduced thanks to RES together with the hydrogen-based storage system, with zero emission respect to diesel solution and a cost of electricity slightly higher. Moreover, considering also a biomass-based CHP system as energy source, the cost is reduced more than three times. The cost of hydrogen for mobility instead, is still highly influenced by the lower development status of hydrogen technologies in the mobility sector

A Review on CO2 Capture Technologies with Focus on CO2-Enhanced Methane Recovery from Hydrates

Natural gas is considered a helpful transition fuel in order to reduce the greenhouse gas emissions of other conventional power plants burning coal or liquid fossil fuels. Natural Gas Hydrates (NGHs) constitute the largest reservoir of natural gas in the world. Methane contained within the crystalline structure can be replaced by carbon dioxide to enhance gas recovery from hydrates. This technical review presents a techno-economic analysis of the full pathway, which begins with the capture of CO2 from power and process industries and ends with its transportation to a geological sequestration site consisting of clathrate hydrates. Since extracted methane is still rich in CO2, on-site separation is required. Focus is thus placed on membrane-based gas separation technologies widely used for gas purification and CO2 removal from raw natural gas and exhaust gas. Nevertheless, the other carbon capture processes (i.e., oxy-fuel combustion, pre-combustion and post-combustion) are briefly discussed and their carbon capture costs are compared with membrane separation technology. Since a large-scale Carbon Capture and Storage (CCS) facility requires CO2 transportation and storage infrastructure, a technical, cost and safety assessment of CO2 transportation over long distances is carried out. Finally, this paper provides an overview of the storage solutions developed around the world, principally studying the geological NGH formation for CO2 sinks

Fuel cell cogeneration for building sector: European status

The advantages of fuel cell based micro-cogeneration systems are the high electrical and total efficiency coupled with zero pollutants emission, which makes them good candidates for distributed generation in the building sector. The status of installations, worldwide and European initiatives and the available supporting schemes in Europe are presented

CO2 from direct air capture as carbon feedstock for Fischer-Tropsch chemicals and fuels: Energy and economic analysis

The investigated plant concept integrates the direct air capture technology with the Fischer-Tropsch synthesis. 250 kt/h of air, with a CO2 concentration of 400 ppm, are used as feedstock to produce the synthetic hydrocarbons. The direct air capture is modelled as a high-temperature calcium recovery loop process. An alkaline electrolyser and a reverse water-gas shift reactor produce the required syngas. The Fischer-Tropsch products distribution is described by a carbide model developed for a Co-Pt/ɣAl2O3 catalyst for alkanes and alkenes of carbon number C1-C70. Five integration scenarios are analysed. In the base case, the energy demand of the direct air capture process is supplied with natural gas from the distribution grid. In improved configurations, the effect of Fischer-Tropsch off-gas recirculation to the reverse water-gas shift and/or the direct air capture units is explored, excluding the need of fossil fuel. An electrified direct air capture solution is also included. In the analysed scenarios, the highest system efficiency corresponds to 36.3 %, while the maximum carbon dioxide conversion is of 68.3 %. The maximum waxes production corresponds to 8.7 t/h. Lastly, capital and operating plant costs are allocated in an economic investigation, considering different market electricity costs and financial risk values. In a medium financial risk scenario (interest rate: 7.5 %), the minimum Fischer-Tropsch waxes production cost corresponds to 6.3 €/kgwax, reaching 5.05 €/kgwax at an interest rate of 0%. Lastly, the effect of learning curves over the production cost at the year 2030 and 2050 is included

Energy performance of Power-to-Liquid applications integrating biogas upgrading, reverse water gas shift, solid oxide electrolysis and Fischer-Tropsch technologies

Power-to-liquid (P2L) pathways represent a possible solution for the conversion of carbon dioxide into synthetic value-added products. The present work analyses different power-to-liquid options for the synthesis of Fischer-Tropsch (FT) fuels and chemicals. The FT section is integrated into a complete carbon capture and utilization route. The involved processes are a biogas upgrading unit for CO2 recovery, a reverse water gas shift, a solid oxide electrolyser and a Fischer-Tropsch reactor.The upgrading plant produces about 1 ton/h of carbon dioxide. The recovered CO2 is fed to either a reverse water gas shift reactor or a solid oxide electrolysis unit operating in co-electrolysis mode for the generation of syngas. The produced syngas is fed to a Fischer-Tropsch reactor at 501 K and 25 bar for the synthesis of the Fischer-Tropsch products, which are further separated into different classes based on their boiling point to yield light gas, naphtha, middle distillates, light waxes and heavy waxes. The developed process model uses a detailed carbide kinetic model to describe the formation of paraffins and olefins based on real experimental data. The effect of Fischer-Tropsch off-gas recirculation has been studied against a one-through option. Finally, energy integration of each configuration plant is provided. Results from process simulations show that the best model configurations reach a plant efficiency of 81.1% in the case of solid oxide electrolyser as syngas generator, and 71.8% in the case of reverse water gas shift option, with a global carbon reduction potential of 79.4% and 81.7%, respectively

Reversible Solid Oxide Cell (ReSOC) as flexible polygeneration plant integrated with CO2 capture and reuse

This work presents the concept of a Reversible Solid Oxide Cell (ReSOC) system localized in an urban residential district. The system is operated as a polygeneration plant that acts as interface between the electricity grid and the local micro-grid of the district. The ReSOC plant produces hydrogen via electrolysis during periods of low electricity demand (i.e., low-priced electricity). Hydrogen is used for multiple city needs: public mobility (H2 bus fleet), electricity production delivered to the micro-grid during peak-demand hours, and heat (accumulated in a storage) provided to the local district heating (DH) network. An additional option analyzed is the use of part of the H2 to produce DME using CO2 captured from biogas obtained from municipal solid wastes. The DME is used for fueling a fleet of trucks for the garbage collection in the residential district. A traditional CO2 removal process based on liquid MEA thermally integrated with the ReSOC system is studied. A time-resolved model interfaces the steady-state operating points with the thermal storage and the loads (electrical, H2 buses, DME trucks, heat), implementing constraints of thermal and H2 self-sufficiency on the system. Neglecting the DME option, the average daily roundtrip electric efficiency is about 38%, while the annual efficiency, which includes H2 mobility and thermal energy to DH, reaches 68%. When the DME option is considered, the thermal demand for CO2 removal and conversion process reduces the heat availability for DH, while the need for additional H2 for DME synthesis increases the electricity consumption for water electrolysis: both these phenomena imply a reduction of system efficiency (-9%) proportional to DME demand