Biocrude Production through Pyrolysis of Used Tyres

A review of the pyrolysis process of used tyre as a method of producing an alternative energy source is presented in this paper. The study reports the characteristics of used tyre materials and methods of recycling, types and principles of pyrolysis, the pyrolysis products and their composition, effects of process parameters, and kinetic models applied to pyrolysis. From publications, the proximate analysis of tyre rubber shows that it is composed of about 28.6 wt.% fixed carbon, 62 wt.% volatile material, 8.5 wt.% ash, and 0.9 wt.% moisture. Elemental analysis reveals that tyre rubber has an estimated value of 82 wt.% of C, 8 wt.% of H, 0.4 wt.% of N, 1.3 wt.% of S, 2.4 wt.% of O, and 5.9 wt.% of ash. Thermogravimetry analysis confirms that the pyrolysis of used tyre at atmospheric pressure commences at 250°C and completes at 550°C. The three primary products obtained from used tyre pyrolysis are solid residue (around 36 wt.%), liquid fraction or biocrude (around 55 wt.%), and gas fraction (around 9 wt.%). Although there is variation in the value of kinetic parameters obtained by different authors from the kinetic modeling of used tyre, the process is generally accepted as a first order reaction based on Arrhenius theory.

Sonochemical Approach to Synthesis of Co-B Catalysts and Hydrolysis of Alkaline NaBH4Solutions

Co-B catalysts are promising candidates for hydrogen evolution via hydrolysis of alkaline sodium borohydride (NaBH4) solutions. In the present paper, a sonochemical approach was investigated for synthesis of Co-B catalysts and hydrolysis of alkaline NaBH4solutions. Sonochemical application on synthesizing process improved the intrinsic and extrinsic properties of Co-B catalysts such as crystal, spectral, surface area, pore volume, pore diameter, and particle size. Co-B catalysts prepared by sonochemical approach possessed smaller particle size, higher surface area, and higher pore volume than the Co-B catalysts prepared by coprecipitation synthesis. The effects of sonochemical process on hydrolysis of alkaline NaBH4solutions were investigated by Arrhenius theory. It was clearly demonstrated that the advantages of alkaline NaBH4solution sonohydrolysis provide superficial effects on hydrogen evolution kinetic as maximum H2generation rate (HGR) and minimum activation energy (Ea).

Electrical Conductivity in Doped Zirconia Systems: Beyond Arrhenius Theory

Este artigo aborda o tema condutividade elétrica em sistemas de zircônio dopado , que é um importante problema não resolvido na física da matéria condensada. Embora os fenômenos de transporte em zircônio dopado sejam geralmente tratados pela teoria de van’t Hoff- Arrhenius, no qual se prevê que o logaritmo da taxa de transporte é uma função linear do inverso da temperatura e que a energia de ativação é constante , muitos experimentos indicam uma não dependência de Arrhenius da temperatura. Nesses materiais, o logaritmo da condutividade elétrica quando graficada em função do inverso da temperatura absoluta , apresenta um desvio negativo da linearidade. Observando, a partir desse problema, o principal objetivo deste artigo é propor uma alternativa de aproximação para descrever a dependência da temperatura com a energia de ativação de difusão, assim como a condutividade não- Arrhenius para os sistemas (ZrO2 ) 1 - x( Y2 O3 )x. Além disso, o presente estudo fornece novos insights sobre os desvios da linearidade em muitos fenomenos não- Arrhenius, tais como processos não exponenciais.

Oxidation of Hafnium and Diffusion of Hafnium Atoms in Hexagonal Close-Packed Hafnium; Microscopic Investigations by Perturbed Angular Correlations

Time-differential perturbed angular correlation (TDPAC) studies in hafnium metal (~5%Zr) have been carried out at different temperatures. It is found that hafnium metal on heating at 873 K continuously for two days in air, transforms partially and abruptly to HfO2 while no component of oxide has been observed for heating up to 773 K and during initial heating at 873 K for 1 day. This result is strikingly different to that expected from the Arrhenius theory. Also, a strong nuclear relaxation effect has been observed at 873 K due to rapid fluctuation of hafnium atoms in hexagonal closepacked (hcp) hafnium. At this temperature, ~ 5% probe nuclei experience static perturbation due to monoclinic HfO2, ~ 50% experience fluctuating interaction, and ~ 5% produce static defect configuration of hcp hafnium. With lowering of temperature, defect configurations of hafnium increase at the cost of fluctuating interaction. An almost total fluctuating interaction observed in hcp hafnium at a temperature much lower than its melting point is another interesting phenomenon.

Exploring a first-principles-based model for zooplankton respiration

Packard, T. T., and Gómez, M. 2008. Exploring a first-principles-based model for zooplankton respiration. – ICES Journal of Marine Science, 65: 371–378. Oxygen consumption (R) is caused by the respiratory electron transfer system (ETS), not biomass. ETS is ubiquitous in zooplankton, determines the level of potential respiration (Φ), and is the enzyme system that ultimately oxidizes the products of food digestion, makes ATP, and consumes O2. Current respiration hypotheses are based on allometric relationships between R and biomass. The most accepted version at constant temperature (T) is R = i0M0.75, where i0 is a constant. We argue that, for zooplankton, a Φ-based, O2-consuming algorithm is more consistent with the cause of respiration. Our point: although biomass is related to respiration, the first-principles cause of respiration is ETS, because it controls O2 consumption. Biomass itself is indirectly related to respiration, because it packages the ETS. Consequently, we propose bypassing the packaging and modelling respiration from ETS and hence Φ. This Φ is regulated by T, according to Arrhenius theory, and by specific reactants (S) that sustain the redox reactions of O2 consumption, according to Michaelis–Menten kinetics. Our model not only describes respiration over a large range of body sizes but also explains and accurately predicts respiration on short time-scales. At constant temperature, our model takes the form: where Ea is the Arrhenius activation energy, Rg, the gas constant, and Km, the Michaelis–Menten constant.