Analysis of removal and decomposition pathways of Vaporized Hydrogen Peroxide (VHP) for aircraft decontamination operation

In response to possible terrorist attacks and epidemic/pandemic diseases, there is a need for efficient infection control and sanitization of airliners. Use of vaporized hydrogen peroxide (VHP) is a promising method to achieve the goal. However, the impact of disposed VHP on atmospheric environment after decontamination operation needs to be fully understood to avoid any detrimental consequence caused by airliner decontamination. This paper analyzed the removal and decomposition pathways of VHP in the atmosphere, including physical and chemical pathways. Absorption by water droplets in atmosphere and photolytic decay mechanisms have been investigated. The results show that the uptake to water droplets in the air appears to be a major pathway for the removal of VHP

Energy system requirements of fossil-free steelmaking using hydrogen direct reduction

The iron and steel industry is one of the world's largest industrial emitters of greenhouse gases. One promising option for decarbonising the industry is hydrogen direct reduction of iron (H-DR) with electric arc furnace (EAF) steelmaking, powered by zero carbon electricity. However, to date, little attention has been given to the energy system requirements of adopting such a highly energy-intensive process. This study integrates a newly developed long-term energy system planning tool, with a thermodynamic process model of H-DR/EAF steelmaking developed by Vogl et al. (2018), to assess the optimal combination of generation and storage technologies needed to provide a reliable supply of electricity and hydrogen. The modelling tools can be applied to any country or region and their use is demonstrated here by application to the UK iron and steel industry as a case study. It is found that the optimal energy system comprises 1.3 GW of electrolysers, 3 GW of wind power, 2.5 GW of solar, 60 MW of combined cycle gas with carbon capture, 600 GWh/600 MW of hydrogen storage, and 30 GWh/130 MW of compressed air energy storage. The hydrogen storage requirements of the industry can be significantly reduced by maintaining some dispatchable generation, for example from 600 GWh with no restriction on dispatchable generation to 140 GWh if 20% of electricity demand is met using dispatchable generation. The marginal abatement costs of a switch to hydrogen-based steelmaking are projected to be less than carbon price forecasts within 5–10 years

Possibilities for CO2 emission reduction using biomass in European integrated steel plants

Iron and steel plants producing steel via the blast furnace-basic oxygen furnace (BF-BOF) route constitute among the largest single point CO2 emitters within the European Union (EU). As the iron ore reduction process in the blast furnace is fully dependent on carbon mainly supplied by coal and coke, bioenergy is the only renewable that presents a possibility for their partial substitution. Using the BeWhere model, this work optimised the mobilization and use of biomass resources within the EU in order to identify the opportunities that bioenergy can bring to the 30 operating BF-BOF plants. The results demonstrate competition for the available biomass resources within existing industries and economically unappealing prices of the bio-based fuels. A carbon dioxide price of 60 € t−1 is required to substitute 20% of the CO2 emissions from the fossil fuels use, while a price of 140 € t−1 is needed to reach the maximum potential of 42%. The possibility to use organic wastes to produce hydrochar would not enhance the maximum emission reduction potential, but it would broaden the available feedstock during the low levels of substitution. The scope for bioenergy integration is different for each plant and so consideration of its deployment should be treated individually. Therefore, the EU-ETS (Emission Trading System) may not be the best policy tool for bioenergy as an emission reduction strategy for the iron and steel industry, as it does not differentiate between the opportunities across the different steel plants and creates additional costs for the already struggling European steel industry

Effective use of excess capacity for low carbon urban transport futures

A reduction in emissions from transport is essential and requires a system wide approach, inclusive of technological and behavioural changes. Defining capacity in urban transport as the space through which transport demand can be met, the research explores where there is excess capacity in the system and how this could be used to reduce emissions. Capacity may be physical capacity in the roadspace or seats within vehicles, or temporal capacity, where there are fluctuations in the use of the system, such as peak and off-peak flows. This is complementary to the International Energy Agency (IEA)’s definition of urban transport energy efficiency as maximising travel activity whilst minimising energy consumption through a range of approaches and techniques. This paper proposes that interventions designed to enable behavioural change could reduce emissions by changing the way that the urban transport system is used. Drawing on the literature, this work demonstrates how effective use of excess capacity might be facilitated through measures such as smarter choices programmes and the application of intelligent transport systems (ITS). Case studies are provided as examples of ways that urban transport infrastructure can be adapted for more efficient use, including shared space projects and the ‘complete streets’ policy in New York City. The paper concludes by presenting the potential impacts of effective use of excess capacity for reducing urban transport emissions as demonstrated through the case studies

A method for measuring relative in-plane diffusivity of thin and partially saturated porous media: an application to fuel cell gas diffusion layers

A new experimental technique, extended from similar work on dry materials, is presented for measuring the in-plane components of the relative diffusivity tensor for partially saturated porous media. The method utilizes a custom-built holder and measures the transient response to oxygen concentration changes at the boundaries of a porous sample placed between two plates surrounded by a cooling block. The apparatus is kept close to the freezing temperature of water to ensure stable saturation throughout the experiment. Fick's second law is used to fit the transient change in concentration to a numerical solution to obtain the diffusion coefficient for samples of differing saturation. As expected the effective gas diffusivity is found to decrease with increasing water saturation of the media as the porosity is reduced and the tortuosity of the diffusion pathways increased. After extensive validation, this new technique is used to determine the relative in-plane diffusivity of some common fuel cell gas diffusion layer materials. The results are found to follow a power-law function dependent on the saturation consistent with previous modelling work. Samples without hydrophobic treatment are found to have lower relative gas diffusivity, compared with treated samples for the same average saturation

Investigating the impact of an Al-Si additive on the resistivity of biomass ashes

Ash resistivity is an important factor in the collection efficiency of electrostatic precipitators (ESPs). There is good experience in the industry regarding resistivity of coal fly ash and well-established models for its prediction based on coal ash composition. The same is not true for biomass ash and this paper reports much-needed data for three different biomass types. Coal pulverised fuel ash (PFA), can be used as an aluminosilicate additive to mitigate biomass ash deposition issues. The effects of PFA additive on the resistivity of biomass ashes is also reported here. Biomass ash resistivity is an order of magnitude lower than that of typical coal ashes, and thus re-entrainment of particles in ESPs may become an operational issue, exacerbated by the presence of moisture and sulphur. PFA additive can increase the resistivity, but also leads to higher ash loading. Regression analysis indicates that potassium in biomass ash impacts significantly upon resistivity, contrary to previous studies. Various existing resistivity models were tested for predicting biomass ash resistivity; they produced significant overestimates when compared to experimental results due to omission of potassium as a component of the ash. Modifications to existing models or new models are required to predict resistivity of biomass ashes, and the data reported here will be important for developing such a model

Achieving carbon-neutral iron and steelmaking in Europe through the deployment of bioenergy with carbon capture and storage

The 30 integrated steel plants operating in the European Union (EU) are among the largest single-point CO2 emitters in the region. The deployment of bioenergy with carbon capture and storage (bio-CCS) could significantly reduce their emission intensities. In detail, the results demonstrate that CO2 emission reduction targets of up to 20% can be met entirely by biomass deployment. A slow CCS technology introduction on top of biomass deployment is expected, as the requirement for emission reduction increases further. Bio-CCS could then be a key technology, particularly in terms of meeting targets above 50%, with CO2 avoidance costs ranging between €60 and €100 tCO2−1 at full-scale deployment. The future of bio-CCS and its utilisation on a larger scale would therefore only be viable if such CO2 avoidance cost were to become economically appealing. Small and medium plants in particular, would economically benefit from sharing CO2 pipeline networks. CO2 transport, however, makes a relatively small contribution to the total CO2 avoidance cost. In the future, the role of bio-CCS in the European iron and steelmaking industry will also be influenced by non-economic conditions, such as regulations, public acceptance, realistic CO2 storage capacity, and the progress of other mitigation technologies

Dysplasia of the Upper Aerodigestive Tract Squamous Epithelium

Dysplasia of the oral, laryngeal and oropharyngeal stratified squamous epithelia is a microscopically defined change that may occur in clinically identifiable lesions including erythroplakia, leukoplakia and erythroleukoplakia, lesions that convey a heightened risk for carcinomatous progression. Dysplastic lesions have been classified microscopically according to degree of cytologic atypia and changes in architectural patterns, usually on a three part or four part gradation scale. Vocal cord epithelial lesions are graded according to either the Ljubljana or the World Health Organization (WHO) system whereas oral dysplasias are generally classified according to WHO criteria. Cytologically atypical cells are considered to represent precancerous changes predicting an increase risk for carcinomatous transformation. Inter- and intra-rater reliability studies among pathologists have disclosed low correlation coefficients for four part grading systems, whereas improved agreement is achieved (kappa correlation values) using the Ljubljana systems. Evidence forwarded by some studies supports the prognostic value of progressively severe dysplastic changes for carcinomatous transformation; however, some studies indicate that the presence of a clinically defined lesion without microscopic evidence of dysplasia also connotes increased risk for carcinomatous transformation. Loss of heterozygosity (LOH) at 3p and 9p microsatellite domains, DNA ploidy analysis and nuclear image analyses may have predictive value as molecular and histomorphological biomarkers