1,720,988 research outputs found
The Role of Ammonia in Decarbonization: A Techno-economic Assessment of NH3 as H2 Carrier and NH3 as Energy Vector
No full textNH3 is increasingly recognized as a versatile and promising energy vector in the transition towards a sustainable energy future. By utilizing renewable electricity to power the Haber-Bosch process for ammonia synthesis, green ammonia production eliminates or significantly reduces greenhouse gas emissions compared to conventional fossil-based NH3 production pathways. As a clean and sustainable alternative to conventional ammonia, green NH3 offers multiple benefits, including serving as a carbon-free fuel for transportation, providing a means of storing and transporting renewable energy, and enabling the production of carbon-neutral fertilizers and chemicals. In this framework, this work discusses the potential of NH3 as both H2 carrier and energy vector through a detailed techno-economic assessment. For each stage of the value chain, both fixed and operating costs are highlighted, to understand where to focus research efforts for future process intensification
Absorption-enhanced Haber-Bosch for small-scale green NH3 production. A feasibility study
Full text linkIn the context of energy transition, ammonia (NH3), traditionally used as a fertilizer, represents a promising carbon-free energy vector due to its high hydrogen density (around 17.8 wt%). Nevertheless, the huge carbon intensity of NH3 synthesis calls for an intensification of the conventional, fossil fuel-based Haber-Bosch process. Flexibility, small-scale plants, modularity and mild operating pressures become fundamental requirements for sustainable NH3 production, obtained by green H2 from water electrolysers. To achieve these objectives, this work presents a feasibility study for intensifying the Haber-Bosch process, performed by Aspen Plus® V14 simulation software. Lowering the operating pressure, the NH3 condensation downstream the reactor is replaced by NH3 absorption in water. Performances of the novel layout are assessed by means of an energy analysis, based on pinch technology and NH3 equivalent method. Due to the lower power requirement than the traditional scheme and the absence of thermal energy requirement, the proposed configuration is proved to be a promising pathway towards sustainable and decentralized ammonia, supporting global efforts for transition to a low-carbon future
A Technical Analysis of the H2 Purification Trains Downstream of Alkaline Electrolyzers
Full text linkIn view of achieving decarbonization targets, green hydrogen has emerged as a promising low-emission alternative. Typically, green hydrogen is produced by splitting water using various electrolysis technologies powered by renewable energy. Among these, alkaline electrolyzers have been proven as suitable for large-scale applications, operating effectively in alkaline environments under near-atmospheric pressure levels and temperatures. Once produced, H-2 must undergo purification for use in industrial and mobility sectors, with particularly stringent purification requirements for fuel applications. Despite the relevance of H-2 purification due to its usage as an energy carrier, no comprehensive analyses of H-2 purification trains downstream of H-2 production are available in the literature. To fill this gap, the aim of this work is to perform a detailed technical assessment of purification trains downstream of alkaline water electrolyzers, considering KOH removal, oxygen removal, compression and dehydration. Different case studies are discussed, focusing on the alkaline electrolyzer operating pressure (i.e., atmospheric or higher) and considering the application of H-2 in both the industrial and mobility sectors. The design and methodology of the process were developed within the Aspen Plus (R) simulation environment, to support the electrolyzers' integration in industrial settings
Solid-Liquid-Vapor Equilibrium Prediction for Typical Helium-Bearing Natural Gas Mixtures
Full text linkIndustrial, large-scale helium recovery from natural gas is typically performed though cryogenic distillation. These technologies need a deep knowledge of the thermodynamics of the treated mixture: in the case of natural gas to a pipeline, CO2 present in the feed stream might freeze at the process operating temperatures. The aim of this work is to analyze the thermodynamic behavior of the four-component mixture CH4-N2-He-CO2 to predict its triphasic solid-liquid-vapor equilibrium (SLVE). Through a developed computational method based on the classical approach, the nitrogen and helium effect on CO2 solidification has been assessed. The investigated conditions are consistent with typical cryogenic procesthesing temperatures (i.e., 100-200 K) and natural gas compositions. Pressure-temperature and temperature-composition equilibrium loci are provided for each analyzed case, varying the N2 and He content in mixture. Helium behavior as a quantum gas has been considered by introducing temperature-dependent critical parameters, as suggested by Prausnitz and co-workers, valid for an acentric factor equal to zero. Referring to the proposed thermodynamic modeling, the risk of CO2 freezing within a cryogenic helium recovery plant can be avoided by carefully managing the process operating conditions
Hydrogen Liquefaction: a Systematic Approach to its Thermodynamic Modeling
Full text linkIn the present work, a thermodynamic approach capable of describing the hydrogen behavior during its cooling and liquefaction is proposed both for the case of catalytic ortho to para conversion occurring inside dedicated reactors and for the case of continuous conversion inside heat exchangers where the catalyst is packed on the hydrogen side. The state-of-the-art Equation of State to describe the properties of normal-, para- and ortho-hydrogen is the Helmholtz free energy explicit equation. However, it can only describe pure components and not mixtures. The novelty of the proposed approach is that it is based on the widespread Peng Robinson Equation of State and that it allows to accurately describe the calorimetric and volumetric properties of the different forms of hydrogen and their mixtures. Furthermore, it can be easily implemented in the Aspen Plus® process simulator, resulting to be useful in view of design and optimization of the hydrogen liquefaction process
Haber-Bosch process intensification: A first step towards small-scale distributed ammonia production
No full textHigh operating pressures are needed in the Haber-Bosch process to push up the NH3 conversion, which is limited by the thermodynamic equilibrium. This evidence hinders the application of distributed renewable ammonia production on small-scale. One possible solution to overcome this problem is the NH3 removal downstream the reaction stage. Ammonia separation from unconverted gases can be performed either with solidstate species (i.e., metal halides or borohydrides), that react reversibly with gas phase NH3, or liquid solvents. Among liquid solvents, traditional NH3 absorption technologies (water, aqueous acids or NH4H2PO4) or novel absorption technologies (ionic liquids or deep eutectic solvents) can be applied. In this respect, the aim of this work is to analyse the NH3 production process intensification, introducing the NH3 removal section through absorption with a phosphate solution downstream the reaction stage. The use of absorption for ammonia separation may open the door to moderate pressure synthesis loop and may pave the way for a down-scalable process based on renewable energy sources.& COPY; 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved
Helium Shortage 4.0: How to Face the Problem Through its Energy-efficient Recovery from Natural Gas
Full text linkHelium is an extraordinary commodity. Its many remarkable properties, i.e., lightness, inertness, small atomic size, low liquefaction temperature, make this element play a crucial role in advanced technological sectors. Despite it is the second-most-abundant element in the universe, the only viable helium sources are certain natural gas fields, where helium accumulates because of α-decay of Uranium-238 and Thorium-232. Helium production from natural gas has long been discouraged by the marginal economic revenue compared with the required operating costs. However, the helium shortage we are experiencing today has revived the interest in its recovery. In this panorama, the development of efficient processes for helium separation from natural gas and its upgrading is of paramount importance. The aim of this work is to analyse the cryogenic helium recovery from natural gas. Single-column and double-column process configurations are discussed, to identify their applicability range depending on the feed compositions. To benefit from the high flexibility of the single column configuration, its application to CO2 containing mixtures is investigated, to lighten the upstream acid gas removal section, thus enabling significant energy savings in the overall gas-treatment chain
Dehydration of IPA-H2O mixture: Review of fundamentals and proposal of novel energy-efficient separation schemes
No full textAccording to the ongoing regulations, the need to identify green and economical production roots for fuels is of paramount importance. Unfortunately, biofuels production is often accompanied with the for-mation of water, that needs to be removed energy-efficiently. To achieve this separation, extractive and conventional heterogeneous azeotropic distillation have been extensively studied, but these solutions are usually high energy-demanding when non-negligible water content is involved. In view of introducing significant energy savings for the alcohol dehydration, this work focuses on the analysis of two innovative separation schemes: one based on heterogeneous azeotropic distillation with binary azeotrope and the other based on liquid-liquid extraction combined with distillation. For the sake of example, the proposed alternatives have been applied to the isopropanol-water mixture. The performances of the new configurations are assessed in terms of energy consumption and com-pared with conventional heterogeneous azeotropic distillation, proving the energy saving of the two pro-posed layouts.(c) 2023 Elsevier Ltd. All rights reserved
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