Secondary Raw Materials from Residual Carbon Fiber-Reinforced Composites by An Upgraded Pyrolysis Process

This paper presents a process where carbon fibers and hydrogen can be recovered simultaneously through a two-stage thermal treatment of an epoxy-carbon fiber composite. For this purpose, some pieces of epoxy resin reinforced with carbon fiber fabrics have been fabricated and, after curing, have been pyrolyzed in an installation consisting of two reactors. In the first one, the thermal decomposition of the resin takes place, and in the second one, the gases and vapors coming from the first reactor are thermally treated. Once this process is completed, the solid generated is oxidized with air to eliminate the resin residues and carbonaceous products from the fibers surface. The recovered carbon fiber fabrics have been reused to make new cured parts and their electrical and mechanical properties have been measured. The results show that it is possible to obtain carbon fiber fabrics that can be processed as they leave the recycling process and that retain 80% of the tensile modulus, 70% of the flexural strength, and 50% of the interlaminar shear strength. At the same time, a gaseous stream with more than 66% by volume of hydrogen can be obtained, reaching a maximum of 81.7%.

What causes the fragmentation of debris streams in TDEs?

ABSTRACT A tidal disruption event (TDE) occurs when a star passes too close to a supermassive black hole and gets torn apart by its gravitational tidal field. After the disruption, the stellar debris form an expanding gaseous stream. The morphology and evolution of this stream are particularly interesting as it ultimately determines the observational properties of the event itself. In this work, we perform 3D hydrodynamical simulations of the TDE of a star modelled as a polytropic sphere of index γ = 5/3 and study the gravitational stability of the resulting gas stream. We provide an analytical solution for the evolution of the stream in the bound, unbound, and marginally bound cases, which allows us to describe the stream properties and analyse the time-scales of the physical processes involved, applying a formalism developed in star formation context. Our results are that, when fragmentation occurs, it is fuelled by the failure of pressure in supporting the gas against its self-gravity. We also show that a stability criterion that includes also the stream gas pressure proves to be far more accurate than one that only considers the black hole tidal forces, giving analytical predictions of the time evolution of the various forces associated with the stream. Our results point out that fragmentation occurs on time-scales longer compared with the observational windows of these events and is thus not expected to give rise to significant observational features.

Abatement of odour emissions by UV/Ozone oxidation process

<p>The growing expectations of the population and the increasingly stringent regulations about air pollution have resulted in the need to minimize and conveniently treat the waste gas from different emission sources. The emissions from a large variety of plants, including waste and wastewater treatment plants, result mainly from the degradation of organic matter. These emissions are composed of a complex of substances emitted at low concentrations from diffusive sources. These characteristics make complex their treatment in economically efficient conditions. The design and management of environmental protection and industrial plants, therefore, require the implementation of focused processes for the control of the target compounds. The present study shows the applicability of an UV-Ozone lab-scale system for odours and VOCs removal. An artificial gaseous stream contaminated by toluene, at different incoming concentrations, was treated evaluating the abatement efficiencies in terms of odours and total VOCs as a function of power and contact time. The residue ozone concentrations was determined in order to optimize the set-up conditions. The results were discussed with the aim of evaluating the feasibility of the investigated solution for the advanced treatment of the waste gas from environmental facilities. Removal efficiencies up tp 91% were reached for the investigated conditions. Lower inlet concentrations resulted in high residue ozone outgoing the processes and, thus, it resulted over dimensioned for inlet load lower than 1,22 mg per minute.</p>

SUPERCRITICAL WATER GASIFICATION AS A TREATMENT FOR LABORATORY ORGANIC WASTE

The thermodynamics of supercritical water gasification (SCWG) was studied in order to determine its potential for treatment of laboratory liquid organic waste. A thermodynamic model based on the minimization of Gibbs energy was developed in Aspen Plus software that simulated the SCWG of liquid lab organic wastes on an ash free basis. The feed stream contained a mixture of aliphatic (hexane), oxygenated (acetone, ethyl acetate,ethyl ether, isopropyl alcohol and methanol), aromatic (toluene and xylene) and chlorinated hydrocarbons (chloroform and dichloromethane). The showed that a pressure of 25 MPa, low organic material concentration of 5-10% in the feed and temperatures over 600oC, SCWG resulted in hydrogen rich syngas aith a trace amount of HCI in the liquid effluent. High conversion rates were obtained for oxygenated hydrocarbons having destruction and removal efficiency (DRE) greater than 99.99% with the rest of the compound having a 100% DRE. The composition of the gaseous stream was found to be such that the gas could be released safely to the atmosphere or be stored at high pressure. The study established a proof of concept that there is potential for laboratories to use this method to deal with organic lab wastes with the SCWG process effluent that is environmental friendly.

The main reasons of rebound, coagulation, and explosive disintegration of the liquid drops in gas-vapor-droplet streams

We have reviewed the known data about mechanisms, conditions, reasons, and characteristics of rebound, coagulation, and explosive disintegration of drops in gas-vapor-droplet streams. The three main factors of altering a direction of motion, a velocity, a size and a concentration of droplets in a gaseous stream have been highlighted. Among of them are the thermal factor (heating and evaporation of drops), the aerodynamic factor (acceleration, reverse motion, and deceleration of drops due to their entrainment by gaseous stream), the dynamic factor (change in size, velocity, and direction of motion of drops after their collision). We have generalized the findings obtained by various authors in experiments with two drops, little group of drops, and aerosol. In addition, we have reviewed the published results about the fields of velocities and motion trajectories of drops in a flow, about the change in size and concentration of drops due to rebound, coagulation, disintegration (i.e. the complete destruction of the parent drops and the detachment of the liquid fragments of different size and volume from the surface).

DESIGN OF A PACKED-BED ABSORPTION COLUMN CONSIDERING FOUR PACKING TYPES AND APPLYING MATLAB

In the present work, a packed bed absorption column is designed to recover certain amounts of ethanol contained in a gaseous stream. Four packing types (50-mm metal Hiflow® rings, 50-mm ceramic Pall® rings, 50-mm metal Top Pak® rings and 25-mm metal VSP® rings) are considered in order to select the most appropriate one in terms of column dimensions, pressure drop and mass-transfer results. Several design parameters were determined including column diameter (D), packing height (Z), overall mass-transfer coefficient (Km) and gas pressure drop (P/Z), as well as the overall number of gas-phase transfer units (NtOG), overall height of a gas-phase transfer unit (HtOG) and the effective surface area of packing (ah). The most adequate packing to use for this absorption system constitutes the 25-mm metal VSP® rings, since it provided the greatest values of Km (0.325 kmol/m3.s), and ah (169.57 m-1), as well as the lowest values of both Z (0.6 m) and HtOG (0.145 m), meaning that it will supply the higher mass-transfer conditions with the lowest column dimensions. The influence of both gas mixture (QG) and solvent (mL) feed flowrates on D, Z, Km, P/Z, NtOG and HtOG was also evaluated for the four packing considered. The design methodology was solved using computing software MATLAB® version 7.8.0.347 (R2009a) (Math Works, 2009), and also Microsoft Excel®.D

Predictions of Xylene Adsorption on Agglomerated Activated Carbon Pellets in a Fixed Bed Column

Volatile organic compounds (VOCs) are an important category of air pollutants and adsorption has been widely recognized as an effective means of controlling emissions to the atmosphere. The current study used theoretical model to analyze the rate of xylene adsorption from inert gaseous stream on the granular activated carbon in a fixed bed column under varying operating conditions. The model considers the inner diffusion of VOC into the activated carbon particles. Experimental results of another author study were used to validate the present model and the methodology proposed to determine the xylene concentrations at the outlet of the column and corresponding inner particles.

PrekotAC as Filter Aids for Efficient Dust Separation in a Fabric Filter

Fabric filters are extensively used as an air pollution control system for its high efficiency to collect particles from gaseous stream. The system is commonly installed in many incineration plants as the means to control dust and gaseous emissions. Unfortunately, their applications in these facilities are short lived due to wear and tear of the fabric media. This is because the fabric filter is not adequately conditioned before it is put up into service. A simple technique is to apply so called ‘pre-coat’ material to coat a layer of inert material onto the surface of the fabric as a ‘barrier’ for protection as well as to allow a uniform air flow passing through the filter media. In this regard, a newly formulated filter aids material known as PrekotAC, not merely acts as an adsorbent for flue gas cleaning but also an efficient dust separation agent in a fabric filter system. A mixture of PreKotTM:Activated Carbon of 40:60 (%weight) was found to be the most preferable combination with its particle size distribution between 75 and 600μm, which is bigger size fraction than the original materials.