Thermal Runaway in Tubular Reactor Systems with n-th Order Kinetics

This paper addresses the problem of predicting the critical parameters that characterize thermal runaway in a tubular reactor with wall cooling, introducing a new view of the n-th order kinetics reactions. The paper describes the trajectories of the system in the temperature-(concentration)n plane, and deduces the conditions for the thermal risk

Energía nuclear: fundamentos, reactores, residuos

Recopilación de articulos de la WIKIPEDIA sobre fundamentos de la energía nuclear

Adsorption of PAHs and PCDD/Fs in Microplastics: A Review

The presence of microplastics (MPs) in the environment, and the effects that the ingestion of these materials can have on organisms, can be aggravated by the adsorption of harmful substances on the surface or inside the MPs. Of special relevance are the studies that have been carried out on the adsorption and transport of polycyclic aromatic hydrocarbons (PAHs) as well as persistent organic pollutants (POPs) such as dioxins and furans (PCDD/Fs). This review will delve into the research carried out to date regarding the adsorption by conventional and biodegradable MPs of dangerous organic compounds such as those mentioned. In general, the presence of MPs is considered a vector for the entry of these contaminants into living beings, since their capacity to adsorb contaminants is very high and they are ingested by different organisms that introduce these contaminants into the trophic chain.This research was funded by the Ministry of Science and Innovation (SPAIN), grant number PID2019-105359RB-I00

Numerical Integration of Weight Loss Curves for Kinetic Analysis

Research abounds in the literature on kinetic analyses using thermogravimetric (TG) runs. Many of these studies use approximations of integral or derivative forms of the kinetic law and all of them use programmed temperatures. In the present work, a numerical integration procedure was discussed and applied to different examples. We focused on materials presenting a single decomposition curve as well as other materials with more complex processes. Different examples were explored, and the methodology was applied to a number of wastes such as coffee husks, polystyrene and polyethylene. In all cases, the actual temperature measured by thermocouples close to the sample is used, and several runs are fitted using the same kinetic parameters, giving robustness to the results.This research was funded by the Ministerio de Ciencia e Innovación (Spain’s Ministry of Science and Innovation), grant number PID2019-105359RB-I00 and the UAUSTI20-05 grant from the University of Alicante (Spain)

Fluid-Fluid Reactions: Study of the Surface Renewal Theory in Chemical Engineering Courses

The Surface Renewal Theory (SRT) is one of the most unfamiliar models in order to characterize fluid-fluid and fluid-fluid-solid reactions, which are of considerable industrial and academicals importance. In the present work, an approach to the resolution of the SRT model by numerical methods is presented, enabling the visualization of the influence of different variables which control the heterogeneous overall process. Its use in a classroom allowed the students to reach a great understanding of the process

Gasification and pyrolysis of Posidonia oceanica in the presence of dolomite

In the present work, a very detailed study of the reforming of syngas produced in the decomposition of Posidonia oceanica is done. The effect of the presence of different amounts of dolomite is analyzed. Also pyrolysis is studied, in nitrogen atmosphere, and gasification in the presence of air, oxygen and different amounts of steam. A detailed discussion on formation and destruction of tars is done. Furthermore, the effect of the heating rate in the decomposition and the residence time of the evolved gases are discussed. Syngas with ratio H2/CO from 0.3 to ca. 3 can be obtained from this interesting material. Marine species (microalgae) are usually studied with the aim of cultivating them for gas or oil production, but in this paper we draw attention to the possibility of using a natural resource with a very small impact in the ecosystem.Support for this work was provided by the CTQ2013-41006-R project from the Ministry of Education and Science (Spain) and the PROMETEOII/2014/007 project from the Valencian Community Government (Spain)

Decomposition kinetics of materials combining biomass and electronic waste

The disposal of waste from electrical and electronic equipment is an actual problem of industrialized countries. In the present work, thermal decomposition of different materials has been studied in a thermobalance at different heating rates. Kinetic models are proposed for the pyrolysis, gasification and combustion of crushed wood pellets (CWP), halogen-free electrical wires (EWs) and printed circuit boards (PCBs). Three different heating rates were used at each atmosphere condition. One set of parameters can explain all the experiments at the different atmospheres and at the three different heating rates used. In the case of CWP, a model considering three independent first-order reactions gave very good correlations all the heating rates tested both in inert and oxidant atmosphere. The decomposition of synthetic materials (EW and PCB) is modeled by using nth order kinetics. On the other hand, mixtures of these three materials have been prepared and tested for decomposition behavior. A weighted sum of the curves simulated using kinetics of the materials separately gives a good concordance with the experimental curve in the case of PCBs, indicating that there is not chemical interaction between CWP and PCBs when heated and decomposed. This would indicate that the production of pollutants in the decomposition will not be affected by the presence of the other material. Nevertheless, a strong interaction is found with the mixtures between biomass and EW.Support for this work was provided Spanish Ministry of Culture and Sport and by the CTQ2013-41006-R project from the Ministry of Economy and Competitiveness (Spain) and the PROMETEOII/2014/007 project from the Valencian Community Government (Spain)

Production of Acoustic Insulating Materials from Viscoelastic Mattress Waste

In this work, briquettes from mattress waste are manufactured and the acoustic properties of the materials produced are checked. Briquettes are made at temperatures between 170 and 185 °C using waste from viscoelastic memory foam (VMF) and applying pressures between 25 and 75 MPa. Later, the properties of the materials such as their bulk density, porosity, and compaction factor are measured. Afterwards, the materials are subjected to a test to determine the sound reduction index at different frequencies. This is completed with a home-made system in which the acoustic signal is compared in the presence and absence of the mattress briquettes using MATLAB® software (Mathworks, Natick, MA, USA) for signal computing. The results are also compared with a reference acoustic insulation material. The runs show that the materials produced from mattress waste are able to reduce the intensity of sound in a similar way to commercial materials. In fact, reduction indices with prepared briquettes are much higher in the frequencies that most affect the human ear, compared to a reference insulating material

Analysis of the Brominated Dioxin and Furan Emission Congener Pattern from Different Sources

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) have been studied for several decades and are well-known as unintentionally generated persistent organic pollutants (POPs), which pose serious health and environmental risks on a global scale1. Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/F) have similar properties and effects to PCDD/F, as they are structural analogs with all the chlorine atoms substituted by bromine atoms. PBDD/F have been found in various matrices such as air, sediments, marine products, and human adipose samples.Support for this work was provided by the Generalitat Valenciana (Spain), research project Prometeo/2009/043/FEDER, and by the Spanish MCT, research project CTQ2008 05520

Thermogravimetric and kinetic analysis of the decomposition of solid recovered fuel from municipal solid waste

The thermal decomposition of a solid recovered fuel has been studied using thermogravimetry, in order to get information about the main steps in the decomposition of such material. The study comprises two different atmospheres: inert and oxidative. The kinetics of decomposition is determined at three different heating rates using the same kinetic constants and model for both atmospheres at all the heating rates simultaneously. A good correlation of the TG data is obtained using three nth-order parallel reactions.Authors acknowledge the financial support for this work provided by PROMETEOII/2014/007 of Generalitat Valenciana (Spain) and CTQ2013-41006-R (Spanish Ministry of Economy and Competitiveness)