1,720,993 research outputs found
Linking heat and electricity supply for domestic users: an example of power-to-gas integration in a building
No full textA novel power-to-X system, coupling electricity and gas grid in a building, is presented. This system operates a retrofit of the existing photovoltaic system, consuming the electricity overproduction in the local synthesis of methane instead of injecting it into the electricity grid. Methane can be stored in the gas grid and used in winter in the existing gas burners, providing the required heat to keep the building at a comfortable temperature. Additionally, the methanation system provides waste heat that is used to warm up the sanitary water, eliminating the need for an electric boiler. The system, fed by 800 m^2 of solar panels, was optimized according to the weather conditions and the dimensions of the main pieces of equipment were determined. This allows the production of ca. 17 MW h of methane for seasonal storage. By retrofitting the building with the power-to-X unit, the energetic independence of the house is maximized, thanks to the synchronous production of electricity, gas, and heat, including energy storage. Therefore, the profitability of the photovoltaic system is ensured independently from the electricity feed-in tariffs. The system performance was evaluated in a case study in the north of Switzerland. When considering the purchase of renewable natural gas (i.e., from biogas), it was calculated that the system would be profitable for an electricity price below 0.05 € per kW h
Process intensification and energy transition: A necessary coupling?
No full textThe energy transition requires an extensive employment of gas-solid catalytic chemical reactors to support the long-term energy storage. Many renewable resources are decentralised, so that the feedstock for the energy conversion facilities is limited. New reactor technologies will be needed to ensure the efficient conversion of renewable resources in smaller scale than the state-of-the-art processes. Process intensification is a key in this direction, fulfilling the desired conversion efficiency, miniaturization of the process units and integration with the existent facilities. This paper analyses the key aspects of process intensification to be considered and implemented in the development of chemical reactors for the energy transition. The intensification strategies should follow three main directions: miniaturization of the process units, enhanced process efficiency and high reactor flexibility. An effective tackling of these directions is challenging for the standard packed-bed reaction technology, but many alternative and promising options are available. An efficient utilization of reaction engineering principles in the design of the new processes can successfully open the way to the optimal equipment selection for each specific application. Hence, a rationally based, but creative selection of the available technologies will be an essential step in the successful implementation of chemical technology in the energy transition
Trendbericht Technische Chemie 2023
No full textDie Energiewende stellt neue Forderungen an die Verfügbarkeit von Rohstoffen – das verändert das Aufgabengebiet der technischen Chemie. Gefragt sind neue Methoden, um lastflexible Reaktoren zu optimieren, und Prozesse, die sich an die Verfügbarkeit von Ressourcen anpassen
Enhancement of Power-to-Gas via Multi-catalyst Reactors Tailoring Reaction Rate and Heat Exchange
Full text linkThe Sabatier reaction is a key element of power-to-gas development. For this reason, even though the process is known since more than one century, the Sabatier reaction is currently the object of important research efforts towards the development of new catalysts for performance improvement. However, the industrial exploitation of the Sabatier reaction depends on the development of reactors that match the best catalyst with an appropriate heat management. For this reason, this paper develops a methodology for the contemporary optimization of the reactor concept and the catalysts. It is observed that the reactor can be divided into three sections with contrasting requirements. In the first section, the main requirement concerns the reach of the reaction activation conditions. Hence, an adequate match between catalyst and reactor is needed, for example with an appropriate pre-heater. Once the reaction is activated, a reaction hotspot is formed, so that the cooling becomes determining and the main requirement for the catalyst is the resistance to poisoning and sintering. In the last section of the reactor, the low temperature activity of the catalyst is determining, so that a high-performing catalyst is needed. This paper indicates a strategy for the rational design of this catalyst, based on mechanistic evidences
A model-based comparison of Ru and Ni catalysts for the Sabatier reaction
Full text linkThe differences between Ru- and Ni-based catalysts for the Sabatier reactor are assessed on the basis of appropriate kinetic models and reactor designs. The origin of the higher performance of the Ru-based catalyst is analysed in detail. Ru activates the reactor and initiates the thermal runaway at about 100 °C lower than commercial Ni/Mg/Al2O3 catalysts and 10-20 °C lower than Ni/Al2O3 catalysts. In addition, the higher catalytic activity at low temperature of Ru-based catalysts allows the thermodynamic curve to be followed-up to the region of high CO2 conversion. Over steam reforming Ni catalysts, the highest attainable conversion is instead limited to 90%, while tailored Ni catalysts for CO2 methanation can reach 96% conversion in a single pass reactor. In the intermediate conversion areas, the two catalysts show comparable activity, due to the reaction limitations related to the required cooling and to the diffusional limitations that are more pronounced in the highly active Ru. We developed a reactor design routine to define the amount of catalyst required to reach grid-compatible CO2 conversion, and found that 99.5% conversion is attainable in a single step with a 0.5% Ru/Al2O3 catalyst or with a high load of Ni/Al2O3 by introducing an intermediate water condensation step. As a consequence, we calculated that the cost of the catalyst is approximately two to three times higher for the Ru-based reactor than the Ni-based. However, this difference in catalyst cost cannot compensate for the cost of a more complex system, including several different units, when developing energy storage solutions at a small-scale. For this reason, the Ru-based system is, at the current price and technological state, the most economical solution for small-scale applications, while efficient Ni-based catalysts can be the ideal choice for large scale applications
A System for the Combined Carbon Capture and Utilization to Produce Renewable Methanol from Biogas
No full textCoupling of biogas upgrading and power-to-X is challenging due to the intermittent cheap energy availability. A system was designed that overcomes the technical challenges in this coupling. This is possible by alternating biogas upgrading and methanol synthesis in a reactor operating both as sorption-enhanced synthesis reactor and as upgrading unit by pressure swing adsorption. It was observed that this concept is feasible in both fixed- and fluidized-bed reactors, and the potential for economic performance improvement was quantified in approximately 20 % increase of the internal rate of return
Renewable energy storage via CO2 and H2 conversion to methane and methanol: Assessment for small scale applications
No full textThis study analyses the power to methane - and to methanol processes in the view of their efficiency in energy storage. A systematic investigation of the differences on the two production systems is performed. The energy storage potential of CO2 to methanol and methane is assessed in a progressive way, from the ideal case to the actual simulated process. In ideal conditions, where no additional energy is required for the reaction and CO2 is fully converted into products, energy storage is 8% more efficient in methanol than methane. However, the Sabatier reaction can be performed with a lower degree of complexity compared to the CO2 to methanol reaction. For this reason, the methanol production process is analysed in detail. The influence of the process configuration and the energy requirements for the various necessary unit operations is investigated, and an efficiency ranking among the various alternatives is obtained. Single stage, recycle and cascade reactors are compared and assessed in terms of energy requirements for the operation and energy storage in the product. For small scale applications, the cascade reactor is the most suitable process technology, because it does not require additional energy and allows high yield to methanol. With the current technology, we demonstrate that a hybrid process, including both the CO2 hydrogenation to methanol and methane, is the most effective method to achieve a high conversion of renewable energy to carbon-based fuels with a significant fraction of liquid product
Model based determination of the optimal reactor concept for Sabatier reaction in small-scale applications over Ru/Al2O3
No full textThe CO2 methanation is an exothermic reaction controlled by thermodynamic equilibrium. For this reason, the high CO2 conversion, required by the natural gas grid regulations, can be achieved only with a proper thermal management of the reactor. The model-based optimization of the Sabatier reaction by controlling the heat transfer is developed in this paper. The focus of the study is on small-scale applications, which gives rise to various specific technical limitations for the optimization study. We found that the reactor can be divided into three zones: an initial zone, for reaction activation; a central zone, to remove excess heat; and a final zone, to achieve high conversion reaching the thermodynamic equilibrium curve. The effect of the variation of the heat transfer coefficient along the axial coordinate of the reactor is assessed and the optimal profile is defined. Based on these results, a technical approximation of the optimal reactor is proposed, allowing high CO2 conversion with a simple manufacturing
Feasibility assessment of small-scale methanol production via power-to-X
No full textDecentralized methanol production in the context of energy storage (also called power-to-methanol or PtMeOH) requires the development of new process configurations. This is due to the need to avoid energy-intensive compression stages and to adapt to intermittent H2 availability. This study aimed at the determination of the techno-economic feasibility of new small-scale PtMeOH process configurations. It was proposed that, in small scale, the pressure should be limited to 30 bar, the standard H2 delivery pressure of an electrolyzer. This is due to the cost and complexity of a H2 compressor, unsuitable for small-scale systems. As CO2 conversion is limited under these conditions, several configurations differing in the valorization strategy of the unreacted stream were assessed. Additionally, the possible coupling with other processes (e.g., biogas upgrading) was considered. It was found that it was not possible to obtain a profit in the production of methanol from renewable H2 in any configuration at high electricity prices due to the important impact of H2 cost. The highest electricity price allowing profitable operation was 0.07 USD/kWh for the recycling process. If PtMeOH is coupled with biogas upgrading, the process can also be operated in the cascade configuration with a similar economic performance. Hence, the small-scale PtMeOH process is feasible only under very specific conditions: constant low electricity price or coupled with waste-handling facilities. This study determined the set of parameters with which the PtMeOH process can be economically profitable, highlighting under which conditions cleaner methanol production can be envisaged in the near future
Modelling the CO2 hydrogenation reaction over Co, Ni and Ru/Al2O3
No full textThe CO2 hydrogenation reaction was experimentally investigated over pristine Co, Ni and an Al2O3-supported Ru catalyst with 0.5 wt% Ru loading. We developed a reaction model which takes the kinetical, diffusional -and thermodynamic reaction regimes into account and enables the description of the reaction over a broad temperature range. The model is based on a fractional rate law with experimentally determined reaction orders. We found that the overall reaction orders on the different catalysts are in proximity to zero order (0.13 for Co, 0.14 for Ni and 0.38 for Ru/Al2O3), which leads to the interpretation that the reaction is limited by the available surface sites in the underlying reaction conditions. We demonstrate on the example of Ru/Al2O3 that the reaction rate strongly depends on the partial pressure of CO2 in the gas phase. Upon reducing the partial pressure of CO2 in the reaction gas stream via He dilution, the reaction approaches a higher reaction order. Furthermore, the supported Ru catalyst is less limited by pore-diffusion compared to pristine Co. With the derived model we can accurately calculate the CO2 conversion over a broad temperature range; the temperature of maximum conversion is predicted within 15 K and the deviation between simulation and experiment is mostly less than 20%. This enables the simple and rapid prediction of the influence of different reaction parameters such as the activation energy or the diffusional limitations on the CO2 conversion
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