Renewables are steadily growing becoming a significant part of the global energy mix, in particular in the power sector. An attractive solution could be represented by Power to Gas (PtG), an energy ...storage strategy. In the PtG process renewable or excess electric energy is used for water electrolysis to produce hydrogen that is then combined with CO2 and converted into methane (synthetic or substitute natural gas, SNG) through the Sabatier reaction. SNG is particularly interesting because leads to an easily transportable (in the existing infrastructures) fuel with a wide proven market for power, thermal and mobility final use applications. The key issue consist on putting together green hydrogen produced by electrolysis fed by renewables with high content CO2 gases supplied from different sources (e.g. syngas from gasification, biogas, geothermic fields, soil gas and gas wells). In this work the CO2 hydrogenation process, coupled with renewables, has been study in a modular, moveable, skidable plant, in the scale of 0.2–1 Nm3/h of produced SNG. The pilot plant is equipped with a methanation unit constituted by a multi-tubular fixed bed reactor able to work in cooled or adiabatic conditions; water produced is separated by a plate&shell condenser. Several sensors, an online gas analysis system and a data acquisition system allow monitoring continuous experimental tests. The methanation facility is able to work in the range of 1–5 bars. The paper reports the results of first experimental activities related to SNG production with Ru based supported catalyst. The experimental activity was carried out in order to check the operability of all components and to improve the knowledge on methanation process in different conditions relevant to Power-to-Gas applications. Different weighted hourly space velocity (WHSV), gas inlet composition, reagent mixture, H2/CO2 ratio, temperature and pressure conditions have been investigated. Increasing pressure drives CH4 production as CO2 conversion is kinetically boosted by raising pressure. Results show that a decreasing trend of XCO2 is observed by increasing WHSV. Results indicate high CO2 per pass conversion with CO2/H2 concentrate feed using Ru based catalyst. Finally the effect of CH4 in the feed was studied emulating two reactors in series. Biogas representative CO2/H2/CH4 mixtures were tested in order to study direct methanation as a biogas upgrading technology.
This paper presents the experimental development at demonstration scale of an integrated gasification system fed with wood chips. The unit is based on a fixed-bed, updraft and air-blown gasifier—with ...a nominal capacity of 5 MWth—equipped with a wet scrubber for syngas clean-up and an integrated chemical and physical wastewater management system. Gasification performance, syngas composition and temperature profile are presented for the optimal operating conditions and with reference to two kinds of biomass used as primary fuels, i.e., stone pine and eucalyptus from local forests (combined heat and power generation from this kind of fuel represents a good opportunity to exploit distributed generation systems that can be part of a new energy paradigm in the framework of the circular economy). The gasification unit is characterised by a high efficiency (about 79–80%) and an operation stability during each test. Particular attention has been paid to the optimisation of an integrated double stage wastewater management system—which includes an oil skimmer and an activated carbon adsorption filter—designed to minimise both liquid residues and water make-up. The possibility to recycle part of the separated oil and used activated carbon to the gasifier has been also evaluated.
•Three biogas upgrading processes have been successfully simulated by Aspen Plus.•Water scrubbing showed the largest exergy efficiency (94.5%).•A new model for membrane separation was successfully ...developed and integrated.•The exergy analysis allowed to individuate all the waste streams in the processes.•Membrane separation showed the highest specific energy consumption 0.94 kWh/m3 STP.
The aim of this work was to provide a complete exergy and energy analysis of three biogas upgrading technologies: amine scrubbing, water scrubbing and membrane separation processes. Biogas production and treatment represents a key-process for the application of Circular Economy principles, since allows to reuse/reconvert industrial by-products or agro-industrial waste in a product that can be used in different energy demanding sectors, after proper cleaning and upgrading processes. The three technologies here reported have been implemented in Aspen Plus flowsheets, and were used to upgrade a biogas to biomethane, meeting the UNIT/TS 11537:2019 standards for Biogas to be injected in the gas grid. Each units of all the simulated processes have been analysed calculating total exergy feed, total exergy produced and exergy loss, distinguishing that lost for irreversibility and as waste. Water scrubbing was characterized by the highest values of exergy efficiency (94.5%) and methane recovery (99%), whereas the lowest exergy efficiency belonged to membrane separation (90.8%) that returned also the largest specific energy consumption (0.94 kWh/m3 STP). Conversely, amine scrubbing was characterized by the lowest specific energy consumption value (0.204 kWh/m3 STP) but by an exergy efficiency of 91.1%.
•CO2 capture and power to gas technologies were successfully integrated in SNG plant.•Synthetic Natural Gas plant reached near zero lifecycle emissions.•The CO2 capture caused a slight process ...efficiency reduction (<1%)•The SNG specific cost was 5.48c$/kWhSNG when CO2 capture was considered.•Power to Gas plant economic sensitivity analysis was performed.
The production of synthetic natural gas from coal and biomass gasification made it possible to obtain a product that can be used to replace easily the standard natural gas in the existing infrastructures. This paper follows and presents a study that was conducted on a synthetic natural gas plant integrated with carbon capture and storage technologies. The recent growth in the use of energy coming from renewable sources requires that balancing measures be taken for electricity grids, which, as can be easily imagined, is best accomplished by using multiple energy storage technologies. In particular, the power-to-gas technology allows renewable electrical energy to be transformed into methane via electrolysis and subsequent methanation. Moreover, the production of synthetic natural gas can be enhanced by using concentrated CO2 emitted by synthetic natural gas plants, coupling the coal gasification and methanation processes within the same plant. This paper compares and evaluates two distinct process configurations and their implementation with power-to-gas technology in Aspen Plus v.8. During the study, it was analyzed how the introduction of carbon capture and storage technologies affect the overall energy balance, as well as the individual performances of each configuration. The two cases proved to have similar efficiency; it was also observed that the integration of and carbon capture and storage technologies resulted in a negligible reduction in the efficiency of the system (approximately 1%). The integration of power-to-gas technologies led to a decrease in the efficiency of the system up to 30%. Based on the current emission allowances specified in the rules of the regulated market of CO2, it was also assessed how such technologies would be sustainable in terms of costs derived from the production of gas.. An analysis was in fact performed to estimate the costs associated with this type of plant and the results showed that the introduction of carbon capture and storage technologies in synthetic natural gas plants had a lower impact on the costs related to both the plant and the synthetic natural gas. In this respect, a sensitivity analysis of the most influent factors was performed as well. The results showed that, when it comes to the production of gas in in the power-to-gas process, the specific cost strongly depends on the price of electricity and the operating hours.
•The PSA dynamics was successfully modelled in Aspen Adsorption environment.•The PSA process showed an exergy efficiency of 88% and a methane recovery of 93.4%.•The specific energy consumption of the ...process was 0.363 kWh/m3 STP.•The specific exergy of the upgraded gas raised from 18.57 MJ/kg up to 48.27 MJ/kg.
The aim of this work was to provide a complete exergy and energy analysis of a biogas upgrading technology: pressure swing adsorption. This technology has going to be widely used in Europe, because allowed to reach very high methane recovery (93.4%) and Wobbe Index (50.81 MJ/m3 STP) values. In this study, the upgrading process has been implemented in Aspen Plus and Aspen Adsorption dynamics simulation environment and the biogas was upgraded to biomethane, meeting the UNIT/TS 11537:2019 standards for Biogas to be injected in the gas grid. The upgrading technology has been analysed in terms of process efficiency, also considering CH4 total loss, energy and utilities requirements in dynamic conditions. Each units of the simulated process have been analysed calculating total exergy feed, total exergy produced and exergy loss, distinguishing that lost for irreversibility and as waste. The obtained CH4 recovery at steady cycle state was 93.4%, the CH4 purity in the obtained biomethane was 97.13% whereas the productivity reached a value of 0.143 kg/h·kgads reaching an overall exergy efficiency of 88%.
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•Syncrude rich in kerosene fraction is synthetized by carbon dioxide and hydrogen.•Single and double stage processes are analyzed through a simulation environment.•Optimizations led ...to a reduction of energy and raw material consumption.•Sensibility analysis allow to compare technical and economical scenarios.
In the context of European and national energy policies to pursue the energy transition process, the issue of alternative-renewable liquid fuels is clearly addressed, whose purpose is to support the growth of sustainable mobility towards the goal of net zero emissions. On the base of the goals to be achieved in the medium and long term in relation to the theme of decarbonization and the development of new sustainable technologies, the present work deals with the e-fuels, which are produced by hydrogen from water electrolysis driven by renewable energy and CO2 captured from air or industrial sources. In particular, the attention is focused on the production of synthetic kerosene with the purpose to decarbonize the aviation sector, which is one of the most difficult electrifiable sectors due to logistical problems. The main objective of this work is the techno-economic analysis of the production of synthetic kerosene starting from green H2 and CO2 from direct air capture. The study of two main process schemes is carried out for the production of a synthetic crude oil, also called syncrude, rich in the kerosene fraction of interest. In the first scheme, called two-stage or indirect process, the incoming carbon dioxide and hydrogen are transformed through the Reverse-Water-Gas-Shift (RWGS) reaction in a syngas which allows to produce, by means of the Fischer-Tropsch (FT) reaction, the product of interest. The second scheme, referred to as single-stage or direct process, involves the direct formation of syncrude (direct FT-CO2) starting from carbon dioxide and hydrogen. In both cases, kinetic models representative of the considered reactions are selected in order to carry out an accurate process analysis. Through sensitivity analysis and process evaluations, some process optimizations like material recycle and heat integration are performed in order to increasing the efficiency and carry out a cost comparison to evaluate economic feasibility. Regarding the indirect and direct processes, 66.18 bbl/d and 38.46 bbl/d are produced respectively. Considering all the results and scenarios with and without optimizations, the range of the product cost is from 460 to 1435 €/bbl for the indirect process and from 752 to 2364 €/bbl for the direct process. These values strongly depend on the considered prices of power energy and hydrogen used for the present work.
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•PtG: adiabatic and cooled configurations are analyzed with dynamic simulations.•H2 load is changed to examine the methane injection (-5%, −30 % and + 5 %)•Synthetic methane ...composition and CO2 conversion are analyzed during time.•Regulatory limits are considered for the injection into the existing gas network.
The methanation process, or Sabatier process, allows carbon dioxide and carbon monoxide to be hydrogenated into methane, which can be subsequently injected (once the gas grid specifications have been respected) into the gas network infrastructures already present in Europe. This process can be effectively adopted to convert captured CO2 streams from power plants or hard to abate plants by using green hydrogen from renewable-driven water electrolysis. The technical aspects of concern in the methanation process are certainly the strong exothermicity of the process, with consequent possible generation of hotspots along the entire catalyst bed and the management of reaction heat through thermal recovery. These peculiar aspects influence the choice of construction materials and geometry of the methanation reactor, operating parameters, cooling system, type of catalyst/support and the initial conditions of the feed. In particular, the generation of hotspots influences the local kinetic reaction in the methanation reactor, the diffusional limits of hydrogen and carbon dioxide inside the catalyst and the chemical-physical characteristics of the catalyst bed.
The present work reports a first scale-up of the Sabatier process, developed in Aspen Plus simulation environment, with the following characteristics: reactor size to process 925 Nm3/h, (750 hydrogen and 175 carbon dioxide), at 15 bar and 250 °C. After the implementation in the steady state, a dynamic simulation is performed to carry out a transient study of the entire plant. In particular, the attention is focused on the variation in the hydrogen load, produced by electrolysis from the energy surplus from renewable sources. Considering the variable nature of the power flow supplied to the electrolyser and therefore any shutdown and cold start-up phases of this equipment, the following load variation scenarios for the Power to Gas (PtG) system are simulated: −5%, +5% and −30 % molar flow rate of incoming hydrogen, compared to steady conditions used in the preliminary design of the equipment. The study highlights how the cooled reactor configuration is more performing and characterized by a lower number of reactors in series (2 reactors) when compared to the adiabatic configuration (5 reactors). Furthermore, in the cooled reactor configuration the control system is able to respond more quickly to load variations compared to that designed for the adiabatic case, although the latter is mostly adopted from the industrial viewpoint due to temperature control issues. Moreover, the control system manages to respond to load variations by bringing the values of interest (gas grid residual concentration of hydrogen and carbon dioxide, Wobbe index) into the target intervals.
The objective of the paper is to simulate the whole steelmaking process cycle based on Direct Reduced Iron and Electric Arc Furnace technologies, by modeling for the first time the reduction furnace ...based on kinetic approach, to be used as a basis for the environmental and techno-economic plant analysis by adopting different reducing gases. In addition, the impact of carbon capture section is discussed. A complete profitability analysis has been conducted for the first time, adopting a Monte Carlo simulation approach.
In detail, the use of syngas from methane reforming, syngas and hydrogen from gasification of municipal solid waste, and green hydrogen from water electrolysis are analyzed. The results show that the Direct Reduced Iron process with methane can reduce CO2 emissions by more than half compared to the blast furnace based-cycle, and with the adoption of carbon capture, greenhouse gas emissions can be reduced by an additional 40%. The use of carbon capture by amine scrubbing has a limited economic disadvantage compared to the scenario without it, becoming profitable once carbon tax is included in the analysis. However, it is with the use of green hydrogen from electrolyzer that greenhouse gas emissions can be cut down almost completely. To have an environmental benefit compared with the methane-based Direct Reduced Iron process, the green hydrogen plant must operate for at least 5136 h per year (64.2% of the plant's annual operating hours) on renewable energy.
In addition, the use of syngas and separated hydrogen from municipal solid waste gasification is evaluated, demonstrating its possible use with no negative effects on the quality of produced steel. The results show that hydrogen use from waste gasification is more economic with respect to green hydrogen from electrolysis, but from the environmental viewpoint the latter results the best alternative. Comparing the use of hydrogen and syngas from waste gasification, it can be stated that the use of the former reducing gas results preferable, from both the economic and environmental viewpoint.
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•CCS plant has higher profitability in the presence of carbon tax than the base plant.•Green H2 plant needs 5136 annual hours of renewable energy for enviro benefit.•H2 over syngas, from waste gasification, improves economic and enviro outcomes.
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