Volume 16, Issue 10 - Special Issue-International Energy Conference-Mexico, Guest Editors: Castillo-Araiza, Carlos O. / González-Brambilla, Margarita

An important issue in electrochemical oxidations of pollutant compounds, like organic dyes, is identifying a suitable correlation between operational conditions and electrochemical process performance. In such sense, this work deals with the parametric modelling of direct electrochemical incineration of crystal violet (CV) dye in a FM01-LC flow electrochemical reactor with a plastic spacer configuration using boron doped diamond (BDD) and dimensionally stable (IrO 2 and IrO 2 -SnO 2 -Sb 2 O 5 ) anode plates. Mathematical model takes into account the fluid dynamics effects by the use of FM01-LC reactor considering mass transport rate of organic compound (R) from bulk solution to electrode surface, characterized by a dispersion coefficient and Pe number. The effect of strong oxidants produced in the electrode surface can be neglected since the characteristic time constant reaction of pollutants with such oxidants is lower than those describing the diffusion of organic compound to the electrode surface. Model parameters were estimated throughout a fitting method of the experimental data. The model proposed here predicted a 99.7 removal percentage of CV with boron doped diamond and IrO 2 -SnO 2 -Sb 2 O 5 anodes obtained experimentally, meanwhile a 79 % removal with the IrO 2 anode was reached at Re = 2204 during an electrolysis time of 7200 s for both cases. In the case of IrO 2 anodes, complex interactions between hydroxyl-radical and electrode surface provokes an intermediate kinetic process, with an effectiveness factor of 0.59. When BDD and IrO 2 -SnO 2 -Sb 2 O 5 anodes were used, the removal process mediated by hydroxyl-radicals absorbed in electrode surface was fully limited by mass transport.

In this paper, solar photodegradation of caffeine in aqueous solution was studied, this organic compound is the most consumed stimulant around the world. The degradation experiments were carried outdoors in a solar reactor and Evonik-Degussa P25 TiO 2 was used as catalyst. The photochemical and photocatalytic effect were tested in aqueous solutions of caffeine. Experimental results indicate that the organic compound is easily degraded over a very short period of time using 0.5 g L -1 of catalyst. The kinetic analysis indicates that the initial reaction rate of caffeine is described by the LH-HW model. However, the original compound cannot be mineralized very fast, caffeine is converted to other organic compounds with a longer lifetime before the mineralization, converting caffeine CO 2 and water.

Several studies have reported that the hydrodynamics are not affected by the biomass in multiphase partitioning bioreactors. This work aims to demonstrate the effect of biomass concentration (0, 1, 3 and 5 g L −1 ) on the oxygen mass transfer coefficients, the droplet size of the dispersed phase, power consumption and superficial tension in a multiphase partitioning bioreactor (ionic liquid-aqueous-air-biomass system). At a biomass concentration of 5 g L −1 , the oxygen mass transfer coefficient ( k L a ) increased by 55% (249 h −1 ) compared with the abiotic system (160 h −1 ). In the multiphasic system, the droplet size ( d 32 ) decreased when the biomass concentration was increased, producing an increment in the mass transfer area of the dispersed phase. In addition, the power consumption decreased by 44 % compared to a previous report without biomass. Furthermore, the increment of biomass concentration decreased the superficial tension by up to 15 %. A biomass increment in a multiphase system not also increases product yield, but also enhances the bioconversion process. The results obtained suggest that it is obligatory to consider the effect of biomass concentration on hydrodynamic characterisation, design, scale-up and optimisation for improving the performance of biotechnological processes using multiphase bioreactors.

Modeling and hydraulic characterization of a filter-press-type electrochemical reactor was studied by means of residence time distribution and hydraulic indices. For these purposes, a theoretical and approximation of residence time distribution experimental curves with axial dispersion model and Danckwerts’ boundary conditions, the Morrill dispersion index, the short-circuiting index, the Morrill volumetric efficiency index, and useful volume percent were used in order to establish deviation from plug-flow ideal, as well as dead volume, and the hydraulic efficiency. The hydraulic efficiency measure of the filter-press-type electrochemical reactor confirms uniformity of flow and a highly effective useful volume percent (91 %-98 % for all liquid flow rates tested). The axial dispersion coefficients computed (0.0005–0.0021 m 2 /s) indicates a small deviation of plug-flow ideal. Hence, the plug-flow reactor model is reliable for purpose modeling of the filter-press-type electrochemical reactor used in this research. Furthermore, hydrodynamic characterization of the tested filter-press-type electrochemical reactor by using hydraulic indices demonstrated its suitability for several electrochemical applications.

Municipal Solid Waste Incineration (MSWI) has become the most widespread Best Available Technology (BAT) to treat residual waste streams in a reliable and safe way. As such, MSWI has contributed to achieve the landfill diversion targets in many EU member states. Modern waste incinerators, also referred to as Waste-to-Energy (WtE) plants, have furthermore evolved to producers of electricity, heat and steam for energy-consuming industries, agriculture and residences. However, due to the specific composition and properties of MSW and similar waste, and due to the historical development of MSWI, the exploitation of WtE plants as combined heat and power (CHP) plants is not straightforward. The aims of this paper are to develop a better understanding of these limitations, to point out possibilities for increasing the level of energy recovery and utilization in WtE plants, and to document this approach with data and experiences from selected WtE plants currently integrated in CHP schemes. Finally, some design and operational challenges for waste-fired CHP plants are further elaborated from a WtE plant supplier’s perspective.

Propylene is one of the most important commodity chemicals. Its future demand is expected to exceed its production. Alternative routes to obtain this product need to be implemented. Dehydrogenation of propane assisted with catalyst is a promising route to meet demands. The Pt and Cr supported catalysts are amongst the most effective possibilities. However, Pt catalysts are preferred over Cr due to the toxic nature of Cr species. Despite the high performance of the Pt catalysts, they deactivate during reaction, mainly due to coke deposits blocking the active site and/or pores. This effect can be reduced with a support having high connectivity and surface area, like KIT-6. In this work the mesoporous silica KIT-6 was employed as support in a series of Pt-Sn catalysts. The influence of adding or increasing the weight % of Sn to Pt catalyst was studied. There were species of SnO 2 and metallic Pt in the fresh catalysts. After reaction, it was found that in the catalysts with the lowest wt % of Sn (0.5), there were metallic Pt and a Pt-Sn alloy. In the rest of the used catalysts (containing 1.0, 1.5 and 2.0 wt % of Sn) the only detected specie was the Pt-Sn alloy. In the two most active catalysts (having 0.5 and 1.5 wt % of Sn), it was observed a difference of three times the quantity of coke deposited on the surface. The catalysts containing the highest coke deposits maintained its activity due to the high connectivity of the support.

During several reactions, similar to dehydrogenation of propane to propylene, coke is one of the main reasons for the catalyst deactivation. The coke formation and further deactivation of the catalyst are strongly dependent to the active site in the catalyst and/or the properties of the support. KIT-6 with interconnected porous and high surface area can handle with the coke formation, and can disperse easily the deposited Pt nanoparticles. In this sense, a series of Pt-Sn/KIT-6 catalysts were synthesized with distinct Sn loadings and used in the dehydrogenation of propane. The performance of these catalysts during reaction varied with the Sn loading. The specific activities for propylene formation obtained with the catalysts were comparable to the best result reported in the literature. The nanoparticles present in the catalyst through pretreatment and reaction condition was the Pt-Sn alloy (1:1 atomic ratio), and that alloy is suggested to be the active phase. This Pt-Sn alloy was stable during the entire reaction time, that even in two catalysts containing a considerable amount of coke, deactivation was not observed. Also, the support (KIT-6) with high connectivity helped to avoid deactivation by coke.

The aim of this study was to simultaneously evaluate diesel transfer rate (DTR) and oxygen transfer rate (OTR) on the production of an oil-degrading consortium in a three-phase airlift bioreactor (ALB) working at high hydrocarbon phase concentration with the purpose of determine whether the oxygen transfer rate is increased or diminished by an increase in the oil-phase concentration. Increase in hydrocarbon concentration allows an increase in DTR and a consequently higher DTR/OTR ratio thus avoiding hydrocarbon mass transfer limitations. This study demonstrates evidence that at high diesel concentrations, the main carbon fate is the production of biosurfactants.

In the modern electricity sector, power industries are facing the challenge to meet exponentially growing electricity demand with the constraint of reducing carbon emission. Overcoming these issues, the power sector is getting motivated to use decentralized renewable energy based renewable distributed generation (RDG) technology to meet growing demand and reduce carbon emission to meet the government environmental regulations and social equality. The role of management and small size generating units are playing as the key factor in the adoption of green RDG practices. In this work, authors identified factors influencing power sector to adopt green RDG practices through a survey in Indian power industries. After analysis of survey data, the role of government regulation as the most important factor in choosing environment friendly practices has been identified. A significant relationship has been shown between government regulations and managerial concern for using green RDG practices with apparent stakeholder pressures. Findings show that effect of factors influencing green RDG environmental regulation is significant. This analysis will help in the decision-making process to increase concern over green RDG practices.

The State of Quintana Roo, in southeast of México, has important tourist attraction facilities, including underwater sinkholes popular among swimmers and divers. However, carcinogenic hydrocarbons were recently detected. The aim of this work was to demonstrate that biotechnology could represent an alternative to solve this problem; civil participation through the retrojection method could provide an alternative type of prevention.