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The number of applications that demand zero-emission energy carriers, such as liquified hydrogen (LH2), is increasing worldwide. LH2 is typically transported or stored under cryogenic conditions. Storage in such conditions requires super thermal insulations which maintain very low boil-off for a prolonged time. Multi-Layer insulation (MLI) finds widespread use in cryogenic applications, designed to effectively restrict heat inleak towards cryogenic fluids. However, recent studies evidenced that exposure to high heat fluxes, such as in the event of a fire accident, can cause the thermal degradation of the insulation material, resulting in the severe collapse of its heat resistance performance. Therefore, the risk of rapid tank pressurization and its connection to the risk of BLEVE may be possible. This study proposes a numerical model to assess the performances of aluminum-based MLI materials under fire conditions. The model offers insights into the total heat transfer rate through the insulation, serving as an indicator of the deterioration's impact on overall heat transfer. The proposed numerical model is validated against experimental data obtained by a High-Temperature Thermal Vacuum Chamber test facility that reproduces fire exposure conditions. The experiments conducted in this study underscore the emergence of pressure build-up within the insulation system, which contributes to increased gas conduction. Furthermore, it demonstrates that the spacer material is not entirely damaged under simulated fire conditions. The numerical calculation also underscores the significance of the modifications in material surface emissivity due to the deterioration process. The innovative approach proposed in this study thus paves the way for the development of improved tools aiming at the stationary and mobile cryogenic tanks behavior (e.g., LNG, LOX, LN2, and LH2) in fire accident scenarios. The model developed may, in perspective, be integrated into both CFD and lumped models for the calculation of the time to failure of cryogenic equipment under external fires. Therefore, this study offers valuable insights to improve the safety of processes and equipment for the storage of cryogenic fluids, thereby supporting emergency response planning in case of fire accidents.

In recent years, the adoption of liquid hydrogen (LH2) has increased significantly in industrial and transport applications, driven by its low carbon footprint, thereby aiding the fight against global warming. Additionally, its high volumetric energy density, compared to gaseous or compressed hydrogen, enhances hydrogen storage capabilities. However, safety remains a major concern due to its physical-chemical properties and inherent hazardous characteristics, especially in the event of spillage scenarios. Therefore, to better understand the consequences of LH2releases onto or into water, large-scale experimental tests were conducted by Bundesanstalt für Materialforschung und -prüfung (BAM) within the Safe Hydrogen Fuel Handling and Use for Efficient Implementation (SH2IFT) project at the Test Site Technical Safety of BAM, comprising 75 single spill events at varied release rates and orientations. While the rapid phase transition (RPT) phenomenon was not observed, self-ignition of the hydrogen-air cloud occurred, accompanied by blast wave overpressure and heat radiation, without a discernible ignition source. These findings emphasize the need for further investigation into LH2safety. Leveraging experimental data for real-world applications provides insights into safe LH2infrastructure implementation, laying foundational knowledge for addressing safety challenges and advancing LH2technology.

Carbon Capture and Storage (CCS) emerges as a pivotal strategy in the global pursuit of achieving a net-zero society by 2050. CCS technologies may play a strategic role in the mitigation of greenhouse gas emissions in hard-to-abate industrial processes. However, assuring an excellent and enduring safety performance of the CCS value chain is of utmost importance to enhance its social acceptability. The early integration of inherent safety principles and of appropriate safety barriers and safety systems in design is thus paramount. Quantitative Risk Assessment (QRA) is a key tool to investigate and assess the safety performance of technologies. Actually, the unique thermodynamic characteristics of CO2cause specific safety issues throughout the value chain. This comprehensive review explores the state of the art of specific data, models, and tools for the application of QRA to CCS technologies, addressing each of the specific steps of the CCS value chain: CO2capture, conditioning, transport, injection, and storage into geological formations. Available models and data, as well as areas requiring further research to address knowledge gaps are highlighted. Offering a holistic perspective on CCS safety assessment, this review contributes to support informed decision-making based on QRA and advances in understanding the safety of CCS technologies.

The number of vehicles using or transporting cryogenic fuels such as Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) increases fast in the land transportation sector. Does this also entail new risks? The storage of cryogenic fuels requires tanks with Thermal Super Insulations (TSI) to keep the fluid cold and limit the formation of boil-off gas. TSI has proven itself in some applications since the middle of the 20th century, but in the land transport sector they are still quite new, where accidents involving fires, collisions, and their combination are to be expected. This work focuses on investigating the behavior of different types of TSI while exposed to a heat source representing a fire. To this aim, a High-Temperature Thermal Vacuum Chamber (HTTVC) was applied, which allows the thermal loading of a thermal insulation material in a vacuum and measuring the heat flow transported through the TSI in parallel. In this study, the results of 6 samples are presented regarding 3 types of MLI, rock wool, perlites, and microspheres. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as to a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for reducing the risks to people and infrastructures in the progressive establishment of tanks for cryogenic fluids in our industry and society. The data presented in the study can be used to improve the design of tanks and TSIs, the assessment of accident scenarios, and the development of measures for first responders.

Multilayer Insulation (MLI) is frequently used in vacuum conditions for the thermal insulation of cryogenic storage tanks. The severe consequences of the degradation of such materials in engulfing fire scenarios were recently evidenced by several large-scale experimental tests. In the present study, an innovative modelling approach was developed to assess the performance of heat transfer in polyester-based MLI materials for cryogenic applications under fire conditions. A specific layer-by-layer approach was integrated with an apparent kinetic thermal degradation model based on thermogravimetric analysis results. The modeling results provided a realistic simulation of the experimental data obtained by High-Temperature Thermal Vacuum Chamber tests reproducing fire exposure conditions. The model was then applied to assess the behavior of MLI systems for liquid hydrogen tanks in realistic fire scenarios. The results show that in intense fire scenarios degradation occurs rapidly, compromising the thermal insulation performances of the system within a few minutes.

This paper presents a study of identification and validation of data-driven models for the description of the acid gas treatment process, a key step of flue gas cleaning in waste-to-energy plants. The acid gas removal line of an Italian plant, based on the injection of hydrated lime, Ca(OH)2, for the abatement of hydrogen chloride, HCl, is investigated. The final goal is to minimize the feed rate of reactant needed to achieve the required HCl removal performance, also reducing as a consequence the production of solid process residues. Process data are collected during dedicated plant tests carried out by imposing Generalized Binary Noise (GBN) sequences to the flow rate of Ca(OH)2. Various input-output and state-space models are identified with success, and related model orders are optimized. The models are then validated on different datasets of routine plant operation. The proposed modeling approach appears reliable and promising for control purposes, once implemented into advanced model-based control structures.

The use of sodium bicarbonate (NaHCO3) as a solid reactant for the removal of acid pollutants in industrial flue gas streams is a simple and effective process solution. Nonetheless, despite its technological maturity, the industrial application of NaHCO3-based flue gas treatment is still highly empirical. A better knowledge of the heterogeneous reaction process could allow process optimization, resulting in a reduction both in the consumption of reactants and in the generation of solid waste products. In the present study, the reactivity of NaHCO3toward HCl and SO2was investigated in the temperature range between 120 and 300 °C. The key role of thermal activation in determining the reactivity of the sorbent was confirmed. The choice of the optimal temperature for acid gas sorption results from a trade-off: higher temperatures increase the reaction kinetics, but induce the sintering of the activated sodium carbonate. The occurrence of sintering is particularly detrimental for high removal efficiency toward SO2, possibly due to the role of the sodium sulfite layer originated by SO2sorption. As a consequence, the optimal operating temperature resulted as 150 °C for SO2and 210 °C for HCl. The choice of operating temperature in industrial dry sorbent injection units for acid gas abatement is discussed in view of the present findings.

Municipal solid waste incineration (MSWI) is a method of waste valorization whose overall sustainability depends on the effective removal of the gaseous contaminants generated. Hydrogen chloride (HCl) is a typical pollutant formed in waste combustion. Dry processes based on its reaction with basic powders such as calcium hydroxide are among the state-of-the-art best available technologies for MSWI flue gas treatment. An experimental investigation of the heterogeneous reaction process between hydrogen chloride and calcium hydroxide in the temperature range between 120 and 180 °C was carried out. A laboratory-scale fixed bed reactor connected to a Fourier transfrom infrared (FTIR) spectrometer was used for the online continuous monitoring of HCl conversion. Solid reaction products were characterized using thermogravimetric analysis and X-ray diffractometry. The experimental data collected were used to validate a fundamental kinetic model for the description of the gas–solid reaction between Ca(OH)2and HCl. A sensitivity analysis was carried out to assess the importance of the different temperature-dependent parameters in the model. The results allow an improved understanding of the heterogeneous reaction process that is applied in acid gas dry removal processes.

The operation of dry processes for acid gas removal from flue gas in waste-to-energy plants based on the use of calcium hydroxide as a solid sorbent generates a solid waste stream containing fly ash, unreacted calcium hydroxide, and the products of its reaction with acid pollutants in the flue gas (HCl and SO2). To date, the fate of the solid waste stream is to be put into a landfill in the absence of commercially viable recycling approaches. The present study investigates the potential of these residues as CO2sorbents in the calcium looping process. Samples collected in different waste-to-energy plants were tested over multiple carbonation–calcination cycles, comparing their performance to that of limestone. Although inferior, the CO2sorption capacity of the residues resulted in values comparable to that of limestone and that steadily increased for a significant number of cycles. This peculiar behavior was attributed to the presence of a chlorinated phase, which enhances the CO2uptake in the diffusion-controlled stage of carbonation by reducing the product layer resistance to CO2diffusion. No significant release of acid gases was observed at the characteristic temperatures of calcium looping carbonation.

The practice of inherent safety in process development and design asks for reliable and systematic assessment tools. In the present study, a novel quantitative approach developed for the inherent safety assessment of process flow diagrams in early design stages is presented. The output of the approach is a metric that quantifies the inherent safety fingerprint of the process scheme by a set of key performance indicators. Physical parameters are used for the quantification of the hazard deriving from materials, process conditions and equipment characteristics. The assessment resorts to the identification and modeling of credible accident consequences on humans and equipment. The adoption of tangible parameters based on consequence modeling yields a clear and sound picture of the inherent safety performance of a design option. An example of application focused on some envisaged options of the hydrogen supply chain (production, distribution, and utilization) is presented. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009

The decomposition products of hexabromocyclododecane (HBCD), a widely used brominated flame retardant, were investigated by gas chromatography/mass spectrometry (GC/MS). HBCD thermal degradation was conducted under a moderate heating rate (10 °C/min) in a batch reactor using both inert and oxidizing atmospheres. GC/MS analysis allowed the identification of substances derived from the primary pyrolysis process at the moderate heating rates used. The presence of oxygen seems to have a negligible influence on the degradation products obtained in HBCD decomposition, at least at moderate heating rates. Based on the identified products, the main pathways of HBCD thermal degradation were assessed and a mechanism for HBCD decomposition was proposed. The results obtained indicate that hexa-, penta- and tetrabrominated polyaromatic structures seem not to be primary products of HBCD decomposition, and may only be obtained by secondary bromination reactions. Copyright © 2001 John Wiley & Sons, Ltd.

The decomposition products of hexabromocyclododecane (HBCD), a widely used brominated flame retardant, were investigated by gas chromatography/mass spectrometry (GC/MS). HBCD thermal degradation was conducted under a moderate heating rate (10 °C/min) in a batch reactor using both inert and oxidizing atmospheres. GC/MS analysis allowed the identification of substances derived from the primary pyrolysis process at the moderate heating rates used. The presence of oxygen seems to have a negligible influence on the degradation products obtained in HBCD decomposition, at least at moderate heating rates. Based on the identified products, the main pathways of HBCD thermal degradation were assessed and a mechanism for HBCD decomposition was proposed. The results obtained indicate that hexa‐, penta‐ and tetrabrominated polyaromatic structures seem not to be primary products of HBCD decomposition, and may only be obtained by secondary bromination reactions. Copyright © 2001 John Wiley & Sons, Ltd.

A method for the direct determination of the cellulose and lignin content of biomass has been developed. The method assumes that negligible interactions exist between biomass macrocomponents and it is based on the analysis of thermogravimetric (TG) pyrolysis data. The TG‐weighed sum method seems to be reliable and less time consuming than conventional methods for the determination of the cellulose and lignin content. Some limitations of the macrocomponent approach in the description of biomass pyrolysis are also discussed. In particular, hemicellulose pyrolysis data are analyzed. The use of xylans as substitute materials for hemicellulose have been critically examined. The results obtained point out that the widely practiced use of xylans as substitute compounds for the simplified description of hemicellulose pyrolysis can lead to significant errors.