Characterisation of a nuclear cave environment utilising an autonomous swarm of heterogeneous robots

As nuclear facilities come to the end of their operational lifetime, safe decommissioning becomes a more prevalent issue. In many such facilities there exist ‘nuclear caves’. These caves constitute areas that may have been entered infrequently, or even not at all, since the construction of the facility. Due to this, the topography and nature of the contents of these nuclear caves may be unknown in a number of critical aspects, such as the location of dangerous substances or significant physical blockages to movement around the cave. In order to aid safe decommissioning, autonomous robotic systems capable of characterising nuclear cave environments are desired. The research put forward in this thesis seeks to answer the question: is it possible to utilise a heterogeneous swarm of autonomous robots for the remote characterisation of a nuclear cave environment? This is achieved through examination of the three key components comprising a heterogeneous swarm: sensing, locomotion and control. It will be shown that a heterogeneous swarm is not only capable of performing this task, it is preferable to a homogeneous swarm. This is due to the increased sensory and locomotive capabilities, coupled with more efficient explorational prowess when compared to a homogeneous swarm

Slice-selective NMR:a non-invasive method for the analysis of separated pyrolysis fuel samples

Pyrolysis oil has been identified as a possible alternative fuel source, however widespread use is hindered by high acidity and water content. These negative characteristics can be mitigated by blending with, for example, biodiesel, marine gas oil and butanol. These blended samples can be unstable and often separate into two distinct phases. NMR spectroscopy is a well-established spectroscopic technique that is finding increasing application in the analysis of pyrolysis oil and blended fuels derived from it. Here, slice-selective NMR, where the NMR spectrum of only a thin slice of the total sample is acquired, is used to study, non-invasively, how the constituent components of blended biofuel samples are partitioned between the two layers. Understanding the outcome of the phase separation is an important step towards understanding why the blended oil samples separate, and may provide answers to mitigating and eventually solving the problem. The NMR method was successfully used to analyse a number of separated biofuel samples - typically separated into an oil layer, containing marine gas oil and biodiesel, above a bio-oil layer with a high water and butanol content

A techno-economic analysis of energy recovery from organic fraction of municipal solid waste (MSW) by an integrated intermediate pyrolysis and combined heat and power (CHP) plant

The increasing environmental concerns and the significant growth of the waste to energy market calls for innovative and flexible technology that can effectively process and convert municipal solid waste into fuels and power at high efficiencies. To ensure the technical and economic feasibility of new technology, a sound understanding of the characteristics of the integrated energy system is essential. In this work, a comprehensive techno-economic analysis of a waste to power and heat plant based on integrated intermediate pyrolysis and CHP (Pyro-CHP) system was performed. The overall plant CHP efficiency was found to be nearly 60% defined as heat and power output compared to feedstock fuel input. By using an established economic evaluation model, the capital investment of a 5 tonne per hour plant was calculated to be £27.64 million and the Levelised Cost of Electricity was £0.063/kWh. This agrees the range of cost given by the UK government. To maximise project viability, technology developers should endeavour to seek ways to reduce the energy production cost. Particular attention should be given to the factors with the greatest influence on the profitability, such as feedstock cost (or gate fee for waste), maintaining plant availability, improving energy productivity and reducing capital cost

Phases of granular segregation in a binary mixture

We present results from an extensive experimental investigation into granular segregation of a shallow binary mixture in which particles are driven by frictional interactions with the surface of a vibrating horizontal tray. Three distinct phases of the mixture are established viz; binary gas (unsegregated), segregation liquid and segregation crystal. Their ranges of existence are mapped out as a function of the system's primary control parameters using a number of measures based on Voronoi tessellation. We study the associated transitions and show that segregation can be suppressed is the total filling fraction of the granular layer, $C$, is decreased below a critical value, $C_{c}$, or if the dimensionless acceleration of the driving, $\gamma$, is increased above a value $\gamma_{c}$.Comment: 12 pages, 12 figures, submitted to Phys. Rev.

Potential of Virginia Mallow as an Energy Feedstock

This study aims to compare the potential of Virginia mallow to other high yielding perennial grasses and hardwoods by characterising and comparing fast pyrolysis product yields. Feedstocks selected for this study include miscanthus (Miscanthus x giganteus), Virginia mallow (Sida hermaphrodita), willow short rotation coppice (SRC) (Salix viminalis) and oak (Quercus robur). The experimental work was split into two sections: analytical (Py–GC–MS) and laboratory-scale processing using a 300 g h−1 continuous bubbling fluidised bed reactor. Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) has been used to quantify pyrolysis products from these feedstocks by simulating fast pyrolysis heating rates using a CDS 5200 pyrolyser closed coupled to a PerkinElmer Clarus 680 GC–MS. High bio-oil yields were achieved for Virginia mallow, willow SRC and oak (65.36, 62.55 and 66.43 wt% respectively), but miscanthus only produced a yield of 53.46 wt% due to increased feedstock ash content. The water content in the bio-oil is highest from miscanthus (17.64 wt%) and relatively low in the Virginia mallow and hardwoods willow SRC and oak (12.49, 13.88 and 14.53 wt%). Similar high yields of bio-oil and low yields of char and non-condensable gas compared to willow SRC make Virginia mallow an attractive feedstock for fast pyrolysis processing. Graphic Abstract: [Figure not available: see fulltext.]

Effect of temperature on product performance of a high ash biomass during fast pyrolysis and its bio-oil storage evaluation

Bio-oil from the fast pyrolysis of agro-residues still needs to contemplate different production scenarios to look for its feasibility. For this reason, in this work the effect of a range of fast pyrolysis temperature (450, 480, 510 and 550 °C) processing rape straw biomass (with high K content) has been studied in a continuous bubbling fluidised bed reactor. It was found that the catalytic effect of the inorganic content was different at each fast pyrolysis temperature, with the lower temperatures resulting in the highest yield of bio-oil due to minor catalytic effect (up to 41.39 wt%). It was also found that at 480 °C the bio-oil presented the best combination of physico-chemical features such as non-separation phase and the lowest water content; yield (39.65 wt%) and HHV (19.23 MJ/kg), containing a high concentration of phenolic compounds. At the fast pyrolysis temperature of 510 °C and 550 °C, the conjunction effect of temperature and the catalytic effect provoked bio-oil separation into two phases and a higher gas yield than was expected. Then, the higher temperatures are not suitable for bio-oil production. Char is also an interesting co-product for all pyrolysis temperatures

Human Grasp Assist Device With Exoskeleton

A grasp assist system includes a glove, actuator assembly, and controller. The glove includes a digit, i.e., a finger or thumb, and a force sensor. The sensor measures a grasping force applied to an object by an operator wearing the glove. Phalange rings are positioned with respect to the digit. A flexible tendon is connected at one end to one of the rings and is routed through the remaining rings. An exoskeleton positioned with respect to the digit includes hinged interconnecting members each connected to a corresponding ring, and/or a single piece of slotted material. The actuator assembly is connected to another end of the tendon. The controller calculates a tensile force in response to the measured grasping force, and commands the tensile force from the actuator assembly to thereby pull on the tendon. The exoskeleton offloads some of the tensile force from the operator's finger to the glove

Monometallic and bimetallic catalysts based on Pd, Cu and Ni for hydrogen transfer deoxygenation of a prototypical fatty acid to diesel range hydrocarbons

Bimetallic PdxNi(100-x) and PdxCu(100-x) structures of a wide compositional range supported on activated carbon were synthesised via a simple, cheap and commercially relevant method. The surface and bulk properties of both the bimetallic structures and their monometallic counterparts were determined via STEM-EDS, TEM, XPS, powder XRD, N2 porosimetry and ICP-OES. A close correlation between the XRD patterns and EDS elemental composition mapping of individual metal particles established the extent of palladium-base metal interaction in each sample. The performance of the different structures as catalysts for the selective hydrogenation and hydrodeoxygenation of oleic acid, a prototypical fatty acid, was evaluated using tetralin as a hydrogen donor. Catalysts displaying true bimetallic/alloy formation were found to improve the conversion of tetralin as compared to catalysts in which compositional segregation was observed. The PdxNi(100-x) series was found to outperform the PdxCu(100-x) catalysts in terms of hydrogen production via the dehydrogenation of tetralin, mirroring the fact that compositional segregation occurs more for the PdxCu(100-x) series than PdxNi(100-x). The hydrogen transfer deoxygenation of oleic acid over the monometallic and bimetallic catalysts was found to mirror the availability of hydrogen with those catalysts liberating more hydrogen also favouring the formation of C17 and C18 alkanes

Using apparent activation energy as a reactivity criterion for biomass pyrolysis

The reactivity of chemically isolated lignocellulosic blocks, namely, α-cellulose, holocellulose, and lignin, has been rationalized on the basis of the dependence of the effective activation energy (Eα) upon conversion (α) determined via the popular isoconversional kinetic analysis, Friedman’s method. First of all, a detailed procedure for the thermogravimetric data preparation, kinetic calculation, and uncertainty estimation was implemented. Resulting Eα dependencies obtained for the slow pyrolysis of the extractive-free Eucalyptus grandis isolated α-cellulose and holocellulose remained constant for 0.05 < α < 0.80 and equal to 173 ± 10, 208 ± 11, and 197 ± 118 kJ/mol, thus confirming the single-step nature of pyrolysis. On the other hand, large and significant variations in Eα with α from 174 ± 10 to 322 ± 11 kJ/mol in the region of 0.05 and 0.79 were obtained for the Klason lignin and reported for the first time. The non-monotonic nature of weight loss at low and high conversions had a direct consequence on the confidence levels of Eα. The new experimental and calculation guidelines applied led to more accurate estimates of Eα values than those reported earlier. The increasing Eα dependency trend confirms that lignin is converted into a thermally more stable carbonaceous material

A viscosity study of charcoal-based nanofluids towards enhanced oil recovery

Research into nanofluids for enhanced oil recovery (EOR) has been carried out for more than a decade. Metal oxide nanoparticles dispersed in water are usually applied and the nanofluids can recover 8–16 % more of the original oil in place after or comparing to water flooding, while the oil recovery capacity of carbon tube nanofluids can be even better. Higher viscosities of nanofluids than that of water are one of the key properties that contribute to their good performance in EOR. This work, for the first time, prepared nanofluids from two charcoal samples as well as an active carbon sample for their possible application for EOR. The relationship of nanofluid viscosities with pH values as well as nanoparticle concentrations of the nanofluids was studied for their viscous behaviour in different shear conditions. Their representative viscosity data measured at 100 rpm were examined for the values of the so-called Dispersion Factor (DF). The determined DF values for the charcoal-based nanofluids are close to those of metal oxide nanofluids that have much smaller nanoparticle sizes. The highly porous active carbon nanofluid showed strong viscosity enhancement that is comparable to the values reported for nanofluids of carbon nanotubes. Due to their significant viscosity enhancement and carbon sequestration feature, the charcoal-based nanofluids are promising to be used for EOR