RESUMEN

The two-stage technology of porous carbonaceous material obtained via pyrolysis in inert medium with subsequent activation by steam is well known. While steam could be a suitable substance for pyrolysis as well, single-staged technology for waste tire recycling is yet to be developed. A comparative analysis of the characteristics of the carbonaceous materials obtained by the single-staged steam pyrolysis of waste tires was carried out, which could provide a theoretical background for the development of such technology. The steam pyrolysis was performed in a tubular reactor in an overheated steam medium (500°C with 5 kg/h mass flow rate). The technical characteristics of the obtained samples were evaluated in the context of their potential for further application as absorbent and raw material for rubber production according to Chemical Abstracts Service No. 1333-86-4. The composition and physico-chemical properties of the obtained samples were studied using BET and thermogravimetric analysis, atomic emission, transmission and scanning electron microscopies, Raman, X-ray diffraction, and photoelectron spectroscopies. The results revealed that the structure and properties of all obtained carbonaceous material samples were similar. The samples consisted of amorphous carbon (with a disordered graphite lattice) and contained a significant amount of metal oxides. According to experimental data, zinc was present in the form of ZnO with a binding energy of 1022.4 eV, while sulfur was observed in the form of sulfide and oxysulfide with binding energies of 161.8 and 163.2 eV, respectively. According to electron microscopy, the morphology of samples was represented by a set of spherical agglomerates comprising nanosized particles. According to the BET analysis of the samples, the specific surface area varied in the range between 52.0 and 66.0 m2/g and the pore volume values were within a range of 0.53-0.87 cm3/g, while the average pore size varied from 412 to 527 Å.Implications: Our paper presents original research in the field of characterization of solid material obtained by single-staged steam gasification of waste tires, which were produced and exploited in conditions of Russia. Modern technology allows thermal utilization of waste tires by obtaining powders of carbonaceous material, which could be used as fuel, adsorbent, etc., but this process usually consists of two stages - pyrolysis in inert medium and activation in steam or carbon dioxide. One of the most promising directions of technological development is simplifying this process into single step, ensuring that the obtained material could be used as carbon black or adsorbent for gas steam cleansing. No data on suitability of carbonaceous material obtained by single-step steam pyrolysis of all-season waste tires to be adsorbent and/or carbon black is present in the literature. In order to evaluate the suitability of the obtained material to be adsorbent, the high specific surface area should be determined, while CAS technical standards specify many chemical and physical properties of industrial carbon black.The aim of the current article is to study the properties of carbonaceous material obtained during single-staged steam gasification of four different all-season tires (due to their widespread application worldwide) and evaluate its fitness as industrial-scale carbon black or adsorbent. The additional problem addressed was the evaluation of the variation in characteristics of carbonaceous material obtained due to different origins of tires. Experiments were conducted in a tubular lab reactor in order to simplify the experimental procedure while ensuring the applicability of the obtained results to practical conditions.The obtained results could be used for the development of the technology for closed-cycle tire processing (because black carbon is used for tire production) and adsorbent production. The characteristics of the materials obtained allow us to choose optimal parameters for such treatment and develop special policies and programs, which will integrate and regulate waste tire utilization via steam gasification.

Asunto(s)

Pirólisis , Vapor , Reciclaje , Goma , Hollín

RESUMEN

The ignition and combustion of anthracite modified by the addition of pyrolysis oil obtained during thermal processing of waste car tires (WCTs) had been studied. The mass fraction of WCT pyrolysis oil was varied in the range from 5 to 30 wt %. The additive was applied by the drop impregnation method. Ignition and combustion of obtained samples were carried out in a combustion chamber at temperatures of the heating medium T g = 600-800 °C. The gas-phase combustion products were analyzed using an in-line gas analyzer. The application of WCT pyrolysis oil as a combustion modifier contributed to an increase in the reactivity of anthracite, which was expressed in a decrease in the minimum ignition temperature (by 23-104 °C) and a reduction in the ignition delay time. The high-speed video recording indicated that the combustion of both initial and modified with 5 wt % pyrolysis oil anthracite samples was realized in oxidation mode. For samples with more than 10 wt % pyrolysis oil additive, the formation of a visible flame was observed near the sample surface. With an increase in the mass fraction of the additive, the rate of combustion front propagation was increased. The application of WCT pyrolysis oil as a combustion modifier also contributed to the reduction or even the almost complete elimination of unburnt carbon content in the ash residue formed after anthracite combustion.

RESUMEN

The heat transfer enhancement and fluid flow control in engineering systems can be achieved by addition of ferric oxide nanoparticles of small concentration under magnetic impact. To increase the technical system life cycle, the entropy generation minimization technique can be employed. The present research deals with numerical simulation of magnetohydrodynamic thermal convection and entropy production in a ferrofluid chamber under the impact of an internal vertical hot sheet. The formulated governing equations have been worked out by the in-house program based on the finite volume technique. Influence of the Hartmann number, Lorentz force tilted angle, nanoadditives concentration, dimensionless temperature difference, and non-uniform heating parameter on circulation structures, temperature patterns, and entropy production has been scrutinized. It has been revealed that a transition from the isothermal plate to the non-uniformly warmed sheet illustrates a rise of the average entropy generation rate, while the average Nusselt number can be decreased weakly. A diminution of the mean entropy production strength can be achieved by an optimal selection of the Lorentz force tilted angle.