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NH3 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.

Alternative solvents based on aqueous solutions of amino acids have been recently developed as possible substitutes for Mono Ethanol Amine (MEA) for CO2 removal from flue gas streams. The potassium taurate solvent has the advantages of degradation resistance, low toxicity and low energy requirements for its regeneration. With any type of solvent, CO2 removal applied to a power production plant decreases the revenues obtained from selling electricity because of the energy requirements. Operating the CO2 removal section in flexible mode avoids significant effects on the profits of the power plant, while accomplishing environmental regulations. This work is the first journal paper focusing on the application in flexible mode of the potassium taurate system for treating a flue gas stream from a 500 MW coal-fired power plant. Techno-economic evaluations are performed to determine the best operating conditions considering the variation in the electricity demand and its price, and different values of carbon tax. In the summer period, with high electricity prices and demands, carbon tax values between 45 EUR/tCO2 and 60 EUR/tCO2 favor CO2 absorption in the flexible mode, without periods of full CO2 emissions during the day.

Helium 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 a-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.

In 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.

In the energy transition from fossil fuels to renewables, the tendency is to benefit from ultra-sour natural gas reserves, whose monetization was previously considered unviable. The increasing H2S content together with the growing concern about emissions that are harmful to the environment, make necessary the development of efficient strategies for pollutants management. Although large-scale H2S conversion is well-established through the Claus process, novel technologies for H2S valorization could be a reliable alternative for waste-to-valuable chemicals, following the circular economy. In this perspective, technologies such as Hydrogen Sulfide Methane Reformation (H2SMR), non-thermal plasma, photocatalytic decomposition, decomposition through cycles and electrolysis are analyzed for the H2 production from H2S. They represent promising alternatives for the simultaneous H2S valorization and H2 production, without direct CO2 emissions, as opposite to the traditional methane steam reforming. The various H2S conversion routes to H2 are examined, highlighting the advantages and disadvantages of each of them. This review focuses in particular on the most promising technologies, the H2SMR and the non-thermal plasma, for which preliminary process scheme and techno-economic analysis are also reported. Finally, the major research gaps and future developments necessary to unlock the full potential of hydrogen sulfide valorization as a sustainable pathway for hydrogen production are discussed.

Acid gas removal from gaseous streams such as flue gas, natural gas and biogas is mainly performed by chemical absorption with amines, but the process is highly energy intensive and can generate emissions of harmful compounds to the atmosphere. Considering the emerging interest in carbon capture, mainly associated with increasing environmental concerns, there is much current effort to develop innovative solvents able to lower the energy and environmental impact of the acid gas removal processes. To be competitive, the new blends must show a CO2 uptake capacity comparable to the one of the traditional MEA benchmark solution. In this work, a review of the state of the art of attractive solvents alternative to the traditional MEA amine blend for acid gas removal is presented. These novel solvents are classified into three main classes: biphasic blends—involving the formation of two liquid phases, water-lean solvents and green solvents. For each solvent, the peculiar features, the level of technological development and the main expected pros and cons are discussed. At the end, a summary on the most promising perspectives and on the major limitations is provided.

Advanced processes, which are alternatives to ordinary distillation, are essential to dehydrate azeotropic alcoholic mixtures for biofuel production. In that regard, this work focuses on the analysis of heterogeneous azeotropic distillation for the separation of a 2-propanol + water mixture in order to recover the alcohol with a sufficiently low water content. By comparing the performances of various entrainers on the basis of ternary maps, isooctane was selected for further process analysis. An advantage it poses is related to the fact that traces of it within the recovered dehydrated alcohol are highly welcome with a view to its subsequent use as a fuel. Aspen Plus® V11 software was employed for the simulation of the process, thus filling the gap existing in the literature due to the lack of studies on the process analysis of the heterogeneous azeotropic distillation of the 2-propanol + water system using isooctane as an entrainer.