Elvira Spatolisano

The global transition toward a low-carbon economy has intensified the interest in green hydrogen as a key enabler of industrial decarbonization. In particular, the steel sector, one of the most carbon-intensive industries, offers significant opportunities for emissions reduction through H₂-based technologies. This study presents a techno-economic assessment of alternative green hydrogen supply pathways, namely alkaline electrolysis and ammonia cracking, and evaluates their integration into hydrogen-based direct reduction (HyDR) routes. Process simulations are performed using Aspen Plus^® V14 to quantify the energy consumption, hydrogen demand, and associated CO₂ emissions across multiple configurations and case studies. A comprehensive 3E (energy, economics, and environmental) evaluation framework is applied to compare system performance and assess the suitability of each pathway for large-scale deployment. The results indicate that ammonia cracking represents a technically viable and potentially competitive hydrogen supply option for steel decarbonization under the assumed operating conditions, highlighting its relevance as a transitional pathway toward low-carbon steel production.

Liquid Organic Hydrogen Carriers (LOHCs) represent a promising solution for the efficient transport and storage of hydrogen, addressing critical challenges associated with its low volumetric density and safety concerns in gaseous and liquefied forms. LOHCs are oil-like substance, capable of reversibly binding and releasing hydrogen through catalytic hydrogenation and dehydrogenation. Hydrogenation is performed where renewable energy is extensively available: at the loading terminal, green H2 is produced and is chemically bonded to the LOHC molecule. In this way, the hydrogenated molecule is transported safely under ambient conditions using existing liquid fuels infrastructures. At the delivery site, the dehydrogenation process releases high-purity hydrogen for industrial or mobility applications, with the regenerated LOHC carrier being recycled back to the H2 production site for reuse. In view of highlighting critical issues associated to LOHCs implementation at large scale, this paper explores green H2 transport through toluene and dibenzyltoluene. Considering the overall H2 transport value chain, the performances of these two alternatives are assessed by means of equivalent H2 methodology. As a result, insights are provided on their role in enabling a sustainable and efficient hydrogen economy.

As anthropogenic CO₂ emissions continue to drive global warming, innovative approaches to repurpose CO₂ into valuable products emerge as pivotal solutions to mitigate its environmental impact. CO₂ utilization encompasses a range of technologies, including its conversion into fuels, chemicals, and materials, leveraging CO₂ as a resource rather than treating it solely as a waste. This shift not only reduces greenhouse gas emissions but also supports the circular economy by integrating industrial processes with carbon capture and storage technologies. Specifically, in the Waste-to-Energy (WtE) context, sodium bicarbonate production can be an attractive solution, considering that it is required in the plant for SOx and acidic gases abatement. In this work, the carbon dioxide utilization to give sodium bicarbonate in a WtE context is analyzed. With reference to an existing waste-to-energy plant in Italy, the potential of this CO2 utilization method is highlighted by means of process simulation. A preliminary feasibility study is presented, based on heat and material balances retrieved from Aspen Plus ® V14, properly set for the accurate modeling of the system's behaviour. Process performances are discussed, in view of the pilot plant engineering and construction.

In 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, H₂ must undergo purification for use in industrial and mobility sectors, with particularly stringent purification requirements for fuel applications. Despite the relevance of H₂ purification due to its usage as an energy carrier, no comprehensive analyses of H₂ purification trains downstream of H₂ 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 H₂ in both the industrial and mobility sectors. The design and methodology of the process were developed within the Aspen Plus^® simulation environment, to support the electrolyzers’ integration in industrial settings.