37 research outputs found

    Challenges and opportunities in fast pyrolysis of biomass:Part I

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    Fast pyrolysis for liquids has been developed in recent decades as a fast and flexible method to provide high yields of liquid products. An overview of this promising field is given, with a comprehensive introduction as well as a practical guide to those thinking of applying fast pyrolysis liquids (bio-oil) in various applications. It updates the literature with recent developments that have occurred since the reviews cited herein. Part I contains an introduction to the background, science, feedstocks, technology and products available for fast pyrolysis. Part II will detail some of the promising applications as well as pre-treatment and bio-oil upgrading options. The applications include use of bio-oil as an energy carrier, precursor to second generation biofuels, as part of a biorefinery concept and upgrading to fuels and chemicals

    A Novel Design for a Robot Grappling Hook for use in a Nuclear Cave Environment

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    ┬ę 2016 Within the field of robotics there exist few designs for detachable grappling hooks. This paper focusses on the novel design of a detachable grappling hook for use within a nuclear cave environment. The design seeks to exploit the complex network of pipes that is present within a nuclear cave. It is hoped that the grapple may be used to aid with mapping and characterisation of the nuclear cave, as well as increasing the movement capabilities of robots within the cave. It is shown that our prototype grapple is able to support on average 2.4kg of mass, or thirty times its own weight. In addition when dropped from a height of 7.5cm, which removes ballistic instability, the grapple is able to engage itself 87% of the time. Finally the minimum speed that the grapple must be travelling, in order to secure itself to its target, is found to be 1.08m/s

    The catalytic cracking of sterically challenging plastic feedstocks over high acid density Al-SBA-15 catalysts

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    The catalytic cracking of polyolefinic waste materials over solid acid catalysts, such as zeolites, is a promising process for the production of useful fuels and chemicals. However, the inherent diffusional constraints of the microporous zeolites restrict the access of bulky polyolefin molecules to the active site, therefore limiting their effectiveness. To address this, a simple yet effective method of producing mesoporous Al-SBA-15 materials with a high density of Br├Şnsted acid sites has been employed. These catalysts are shown to be very active for the catalytic cracking of low density polyethylene (LDPE), a common waste plastic. The acidic and textural properties of the catalysts were characterised by ICP-OES, XPS, XRD, N2 physisorption, propylamine-TPD, pyridine-FTIR and STEM and have been correlated with their catalytic activity. The product distribution from the catalytic cracking of LDPE has been shown to depend strongly on both the pore architecture and the Al content of the SBA-15 and thus the density and strength of Br├Şnsted acid sites. Fine-tuning the Al content of the SBA-15 materials can direct the product distribution of the hydrocarbons. The Al-SBA-15 materials display increased cracking orientated towards aliphatic hydrocarbons compared to ZSM-5, attributed to the mesoporous nature of SBA-15, overcoming diffusional limitations

    Analysis of product distribution and characteristics of bio-oil and bio-char from fast pyrolysis of date palm tree waste

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    According to recent reports, there are more than 120 million date palm trees worldwide, with the estimated Middle East and North Africa combined share of more than 80%. Date palm trees produce huge amounts of waste amounting to 15-35 kg per tree per year. This represents a challenging environmental problem, since disposal is so far mainly based on landfill and uncontrolled combustion. Please click on the file below for full content of the abstract

    Experimental design and testing in a pilot-scale rotary kiln for the torrefaction of beech wood under system restrictions

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    The torrefaction process increases the energy density of the torrefied feedstock through the loss of volatiles and moisture. The anhydrous weight loss (AWL) measures the loss of volatiles and it is easily correlated with the net calorific value (NCV) of the torrefied product. This work has two different parts. The first part consists of the design of the experiments and the second includes the experiments with results. The system used in CENER, where the simulation and experiments were completed, is a rotary kiln with a maximum capacity of 500 kg/h and a range of operating temperatures between 220-310┬░C. The innovative design feature of this reactor is the extraction of the gases from the middle of the reactor, in such a way that the direction of the gases is co-current in half of the reactor (at the beginning) and countercurrent in the last half. Besides the reactor, there is a flare which combusts the gases from the reactor before releasing them to the atmosphere, and does not allow flows higher than 120 Nm3/h. The two variables that can be modified to overcome the restrictions and achieve the target AWL are the temperature of the reactor (controlled by the temperature of the thermal fluid used to heat the reactor), and the input capacity to the reactor. The relationship of the gases produced to the temperature is straight, the higher the temperature the more gases are produced due to a higher devolatilisation of the feedstock. On the other hand, when the input capacity was modified, it is more difficult to estimate the gas production yield; with an increased feeding rate, the AWL is lower and the amount of volatiles released reduces but there is a higher release of the total amount of moisture content due to a higher feed rate. Given a lower input of feedstock, the total amount of water evaporated is lower but the AWL and the devolatilisation degree of the feedstock is higher and, consequently, more volatiles are produced. Please click Additional Files below to see the full abstract

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

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    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 8ÔÇô16 % 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

    Combined heat and power from the intermediate pyrolysis of biomass materials: performance, economics and environmental impact

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    Combined heat and power from the intermediate pyrolysis of biomass materials offers flexible, on demand renewable energy with some significant advantages over other renewable routes. To maximize the deployment of this technology an understanding of the dynamics and sensitivities of such a system is required. In the present work the system performance, economics and life-cycle environmental impact is analysed with the aid of the process simulation software Aspen Plus. Under the base conditions for the UK, such schemes are not currently economically competitive with energy and char products produced from conventional means. However, under certain scenarios as modelled using a sensitivity analysis this technology can compete and can therefore potentially contribute to the energy and resource sustainability of the economy, particularly in on-site applications with low-value waste feedstocks. The major areas for potential performance improvement are in reactor cost reductions, the reliable use of waste feedstocks and a high value end use for the char by-product from pyrolysis

    The mechanism of hydrogen donation by bio-acids over metal supported on nitrogen-doped carbon nanotubes

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    Biomass-derived carboxylic acids (e.g. acetic acid AcOH and formic acid FA) are a green and low-cost hydrogen source to replace hazardous H2 gas in in-situ hydrogenation processes. To date, bio-acids dehydrogenation has been mainly conducted using noble metal catalysts which would negatively impact the process economy, thus development of efficient non-noble metal catalysts for this purpose is highly desirable. In this study, the performance of transition metals supported on nitrogen doped carbon nanotubes was thoroughly evaluated by computational modelling based on Density Functional Theory (DFT). Results revealed that, out of the 10 selected transition metal candidates, molybdenum (Mo) was most active for binding AcOH and a combination of Mo and nitrogen doping significantly enhanced binding to the carboxylic acid molecules compared to pristine carbon nanotubes (CNTs). The newly designed Mo/N-CNT catalysts considerably facilitated the bio-acids decomposition compared to the non-catalytic scenarios by lowering energy barriers. FA distinctly outperformed AcOH in hydrogen donation over Mo/N-CNT catalysts, through its spontaneous cleavage leading to facile hydrogen donation
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