Browsing by Author "Wessling, Roland"
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Item Embargo Are two bodies in a trench a mass grave? an attempt to bridge the gap between single and mass graves(Equinox Publishing, 2024-03-27) Wessling, Roland; Spoletini, AllieThe definitions for mass graves proposed in the past concentrated on the minimum number of casualties and whether they were in a connected body matrix. This meant that many graves practitioners encounter could not be classified properly. They were neither a single grave nor a mass grave. This article proposes four key measures to address the grave classification issue. Firstly, it introduces three simple criteria to assist in classification. Secondly, it suggests three new grave types (cluster, trench, and serial grave) to name the most common graves. Thirdly, a final grave type, the multiple grave, is added to describe any grave that does not fit into any of the other categories. Finally, this article suggests that the threshold between multiple and many casualties, i.e. how many casualties constitutes a mass grave, should be set for each individual conflict or context rather than aiming for a universal figure. These four measures are designed to be simple, intuitive and flexible enough to allow practitioners to use grave labels that make sense in their particular context for forensic and legal professionals as well as the general public.Item Open Access Catalytic effects on the nonisothermal oxidation of solid fuels by oxygen: an experimental study(American Chemical Society, 2019-09-24) Nyombi, Antony; Williams, Mike; Wessling, RolandThe role played by catalysts in solid fuel reactivity toward oxygen as a viable method for reducing toxic combustion emissions was studied. Catalyst (1 wt % Pd–Sn/alumina) treated and untreated solid fuels were analyzed using thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) coupled with a gas detection system at heating rates of 20–40 °C/min and airflow rates of 30–100 mL/min. The relative CO emission factors, NOx, CH4, energy output, and combustion efficiency were determined as well as values of the activation energy (Ea) and pre-exponential factor (A) for the oxidation of the solid fuels. Results showed that the catalyst treatment enhanced the energy output by more than 22% and reduced CO emission factors by up to 87%. The temperature for release of nitrogen compounds was considerably reduced; however, the amounts produced were not impacted. The combustion efficiency was also improved by up to 60%. In terms of reactivity, catalyst treatment lowered the Ea for oxidation especially at 0.2 ≤ α ≤ 0.8. Catalyst treated samples had more free active sites on their surfaces, which decreased at temperatures of >500 °C possibly due to thermal deactivation of the catalyst. This is a viable method for minimizing toxic emissions from solid fuel combustion and enhancing energy output for domestic and industrial applications.Item Open Access Determination of kinetic parameters and thermodynamic properties for Ash (Fraxinus) wood sawdust slow pyrolysis by thermogravimetric analysis(Taylor and Francis, 2018-08-15) Nyombi, Antony; Williams, Mike; Wessling, RolandAsh (Fraxinus) wood sawdust pyrolysis under nitrogen was conducted using 2, 5, 10, 15, and 20°C/min heating rates. Friedman and Starink methods were used for kinetic analysis while y(α) master plots were used for pyrolysis mechanisms prediction. The mean activation energy were 198 and 202 kJ/mol for Friedman and Starink, respectively. The master plots predicted that the pyrolysis process could be a combination of diffusion, geometrical contraction, nucleation, and reaction order models. The pre-exponential factors were in the range 1012 to 1019 s−1. Gibbs free energy was 180 −185 kJ/mol. The entropy values were negative up to α = 0.75 indicating high orderliness of products relative to reactants but changed to positive at higher conversions implying likely disorderliness of the products compared to reactants. The calorific value of Ash (Fraxinus) wood sawdust was 18.3 MJ/kg.Item Open Access Mechanical impregnation of Pd-Sn/alumina and Cu-Mn/graphite on charcoal to minimise carbon monoxide emissions(Elsevier, 2018-11-23) Nyombi, Antony; Williams, Mike; Wessling, RolandThis study investigated how to minimize carbon monoxide (CO) emissions from charcoal by impregnating with Pd-Sn/alumina and Cu-Mn/graphite. Samples were heated isothermally with continuous monitoring of residual CO using electrochemical and infra-red sensors. With 0.2wt% Pd-Sn/alumina, 26.9% and 44.4% were recorded as lowest and highest residual CO. On the other hand, when 2wt% Cu-Mn/graphite was used, 15.6%, and 25.3% were observed as lowest and highest residual CO. The activity of the catalysts decreased with temperature and increased with catalyst loading. This method could be used on briquettes, wood boiler chips and other solid carbonaceous materials to minimise CO emissions.Item Open Access Reactivity and free radical chemistry of lilac (Syringa vulgaris) charcoal(American Chemical Society, 2019-01-28) Nyombi, Antony; Williams, Mike; Wessling, RolandThe reactivity, and surface chemistry of charcoal determine its combustion behaviour, and these properties depend on the source of the original wood, production conditions and treatment. Here we studied the properties of charcoal derived from lilac (Syringa vulgaris). Its reactivity was tested by isothermal and non-isothermal thermogravimetric analysis and differential scanning calorimetry in air and nitrogen. The free radical concentration was determined by measuring the electron spin resonance of fresh charcoal, after washing with HCl, and after degassing in air with or without nitrogen. We found that lilac is highly reactive, igniting at 250–300 oC with peak combustion at 320–520 oC. The quantity of oxygen consumed and heat released during oxidation increased with temperature. The free radical concentration in the untreated charcoal was 5.29 x 1018 spins/g, compared to 3.49 x 1019 spins/g after acid washing, 7.06 x 1019 spins/g after exposure to air, and 3.75 x 1017 spins/g after degassing with nitrogen before exposure to air. The line width of all the charcoal samples was 11.6–11.9 G. However, degassing the charcoal in nitrogen followed by exposure to air at low temperatures resulted in a four-fold increase in the line width to 41.8 G. The exposure of lilac charcoal to air alone at low temperatures resulted in the formation of persistent peroxyl radicals superimposed on the main peak. The g-values of charcoal samples that were untreated, acid washed, degassed in N2 + air, and degassed in air alone (main peak) were 2.00481, 2.00477, 2.00260 and 2.00483, respectively. The g-values of the peroxyl radicals superimposed on the main peak were 2.0155, 2.0138, 2.0020 and 2.0007, respectively. The reactivity, and free radical content suggest that lilac charcoal is particularly suitable for applications involving energetic materials, catalysis and co-firing.Item Open Access Real time analysis of combustion emissions: a comparison of catalyst treated and untreated solid fuels(Cranfield University, 2019-07-25) Nyombi, Antony; Williams, Michael; Wessling, RolandCarbon monoxide (CO) from combustion of solid fuels causes some deaths worldwide every year. This study has been undertaken to evaluate the amount of carbon monoxide, (and carbon dioxide, nitrogen oxide & methane) evolved from catalyst (Pd-Sn/alumina and Cu-Mn/graphite) treated charcoal briquettes, untreated charcoal briquettes, commercial charcoal and coal at non-isothermal temperatures between 50 to 800 oC attained at different heating rates of 20-40 (oC/min). Samples were heated in a thermal analysis instrument coupled with a multi-gas analyser under flowing air at different flow rates 20-100 (ml/min). Results showed a significant CO and NO reduction with catalyst treated charcoal compared to untreated charcoal briquettes and coal. There is also a strong dependence of CO emissions on heating rate and air flow. This study shows that catalyst treatment of solid fuels helps to minimise harmful combustion emissions.Item Open Access Searching for the missing soldier: identifying casualties from the First World War(University of Valencia, 2019-03-28) Marquez-Grant, Nicholas; Wessling, Roland; Öfele, Angela; Moore, VictoriaIn recent years there has been an increase in the numbers of archaeologists and physical anthropologists involved in searching, locating and assisting in the identification of war casualties. These scientists have played an invaluable role within a larger team of professionals, working together to provide a dignified burial to those who fell for their country and remembering them. This paper reviews some of the work undertaken in Europe with regard to WWI casualties and how the war missing are located and ultimately identified when possible, bringing also some closure to their living relatives.Item Open Access Thermal and catalytic processing of solid fuels to minimise carbon monoxide emissions(2019-11) Nyombi, Antony; Wessling, Roland; Edwards, Mike RThis research was conducted to evaluate the amount of carbon monoxide (CO) emissions from the incomplete combustion of solid fuels, the factors responsible for its release and methods to minimize its release and thus the human exposure to CO in different environments. Unintentional CO poisoning has resulted in many deaths, injuries and chronic ailments. Previous efforts to minimise exposure to CO include awareness campaigns, domestic CO alarms, improved designs for cooking stoves, space heating appliances, and postcombustion CO oxidation using catalysts. However, these methods have not fully solved the challenge of CO exposure. In this study, different sold fuels were processed and analysed to investigate their behaviour under different oxidative environments and to establish ways to reduce the amount of CO released during combustion. Areas of solid fuel research of particular interest include physicochemical properties, reactivity and surface chemistry, CO emission properties, and catalyst impregnation on solid fuels to minimise CO emissions. This was achieved by using raw and pyrolysed wood biomass and coal. The results reported in this thesis show that the degradation profile of wood sawdust involved a combination of mechanisms, including diffusion, geometrical contraction, nucleation, and reaction-order models. Pyrolysed charcoal was found be microporous with a low specific surface area. The charcoal contained high quantities of • C-C and • C-O free radicals, and low-temperature oxidation (< 200 °C) produced persistent peroxyl radicals. Mild-temperature (300 – 650 °C) oxidation showed that the charcoal was highly reactive, with low pre-exponential factors and activation energies. At temperatures < 550 °C, charcoal did not appear to glow to the naked eye. However, this temperature range was shown to correspond to the emission of large amounts of CO. In confined environments, the measured CO emissions increased with decrease in ventilation and increase in height above the floor. ii Catalyst impregnation on charcoal reduced CO emissions by up to 97 % and increased the free active sites on the solid fuel surfaces, which decreased at temperatures > 500 oC possibly due to thermal deactivation of the catalyst.Item Open Access Toxic emissions from smouldering combustion of woody biomass and derived char with a case study of CO build-up in an ISO container(Taylor & Francis, 2019-05-30) Nyombi, Antony; Williams, Mike; Wessling, RolandCarbon monoxide (CO) from the use of biomass products causes some deaths in the United Kingdom every year. This study was undertaken to evaluate the amount of CO from five species of wood sawdust, and charcoal with a case study of CO in a confined ISO container. Laboratory experiments were conducted at temperatures between 350°C and 600°C under flowing air. Results showed a strong dependence of CO emissions on temperature and airflow. The CO emissions in the ISO container were above the recommended exposure limits due to poor ventilation.Item Open Access Using high-resolution digital photography and micro-CT scanning to investigate Deathwatch Beetle damage to an historic timber from HMS Victory(Taylor & Francis, 2022-01-16) Brock, Fiona; Southwell, Richard; Hazell, Zoe; Wessling, Roland; Green, Matthew; Davis, DianaWood-boring insects such as the deathwatch beetle can cause significant damage to historical artefacts and timbers, but the extent of internal damage (and tunnelling activity in general) can be difficult to understand and quantify without the use of destructive sampling techniques. This study explored the potential of high-resolution photography and micro-computed tomography (micro-CT) to investigate beetle activity and inform on the extent of internal damage to a timber from HMS Victory. Micro-CT imaging has allowed the visualisation of deathwatch beetle activity within the timber, revealing differences in tunnelling behaviour preferences for adult and larval forms. Digital techniques were developed to determine the surface area of flight holes on some wooden blocks but were less successful for those blocks where the external surfaces were darkened with age. It was not possible to accurately determine the internal volumes of beetle tunnels within blocks of timber due to the presence of frass, which was found to be virtually indistinguishable digitally from the wood matrix.Item Open Access When is carbon monoxide most dangerous - Safety concerns at Festivals(2017-01-11) Nyombi, Antony; Williams, Mike; Wessling, RolandThis study investigated the effect of temperature & air flow on CO evolved from barbecue charcoal. The amounts of CO were analysed using FTIR and Electrochemical sensors and the colours of charcoal at different temperatures were analysed with reference to a black body radiator. Results show that carbon conversion increased linearly with temperature. CO evolution started at a point when the charcoal was still black. Maximum amounts of CO were recorded at 400-450 deg C but these then reduced as temperatures rose to 600 deg C. Air flow had little effect on carbon conversion and the amounts of CO evolved. Temperature played a dominant but not linear role in CO evolution. Charcoal attained a reddish colour visible to the naked eye at 550 deg C. This intensified to glowing red at higher temperatures. These results would help to inform about CO evolution even during the cooling process of charcoal.Item Open Access When is CO most dangerous: Safety issues at festivals(Cranfield University, 2018-08-08 10:50) Nyombi, Antony; Wessling, Roland; Williams, MikeThis video describes the preliminary work done to show the production of CO at various temperatures as charcoal burns.