Handling of Uncertainty in Life Cycle Inventory by Correlated Multivariate Lognormal Distributions: Application to the Design of Supply Chain Networks

In this work, we analyze the effect of incorporating life cycle inventory (LCI) uncertainty on the multi-objective optimization of chemical supply chains (SC) considering simultaneously their economic and environmental performance. To this end, we present a stochastic multi-scenario mixed-integer linear programming (MILP) coupled with a two-step transformation scenario generation algorithm with the unique feature of providing scenarios where the LCI random variables are correlated and each one of them has the desired lognormal marginal distribution. The environmental performance is quantified following life cycle assessment (LCA) principles, which are represented in the model formulation through standard algebraic equations. The capabilities of our approach are illustrated through a case study of a petrochemical supply chain. We show that the stochastic solution improves the economic performance of the SC in comparison with the deterministic one at any level of the environmental impact, and moreover the correlation among environmental burdens provides more realistic scenarios for the decision making process.

Isobutane Alkylation Process Synthesis by means of Hybrid Simulation-Multiobjective Optimization

Multiobjective Generalized Disjunctive Programming (MO-GDP) optimization has been used for the synthesis of an important industrial process, isobutane alkylation. The two objective functions to be simultaneously optimized are the environmental impact, determined by means of LCA (Life Cycle Assessment), and the economic potential of the process. The main reason for including the minimization of the environmental impact in the optimization process is the widespread environmental concern by the general public. For the resolution of the problem we employed a hybrid simulation- optimization methodology, i.e., the superstructure of the process was developed directly in a chemical process simulator connected to a state of the art optimizer. The model was formulated as a GDP and solved using a logic algorithm that avoids the reformulation as MINLP -Mixed Integer Non Linear Programming-. Our research gave us Pareto curves compounded by three different configurations where the LCA has been assessed by two different parameters: global warming potential and ecoindicator-99.

Logic-Based Outer-Approximation Algorithm for Solving Discrete-Continuous Dynamic Optimization Problems

We present an extension of the logic outer-approximation algorithm for dealing with disjunctive discrete-continuous optimal control problems whose dynamic behavior is modeled in terms of differential-algebraic equations. Although the proposed algorithm can be applied to a wide variety of discrete-continuous optimal control problems, we are mainly interested in problems where disjunctions are also present. Disjunctions are included to take into account only certain parts of the underlying model which become relevant under some processing conditions. By doing so the numerical robustness of the optimization algorithm improves since those parts of the model that are not active are discarded leading to a reduced size problem and avoiding potential model singularities. We test the proposed algorithm using three examples of different complex dynamic behavior. In all the case studies the number of iterations and the computational effort required to obtain the optimal solutions is modest and the solutions are relatively easy to find.

Guidelines for the design of efficient sono-microreactors

Possible drawbacks of microreactors are inefficient reactant mixing and the clogging of microchannels when solid-forming reactions are carried out or solid (catalysts) suspensions are used. Ultrasonic irradiation has been successfully implemented for solving these problems in microreactor configurations ranging from capillaries immersed in ultrasonic baths to devices with miniaturized piezoelectric transducers. Moving forward in process intensification and sustainable development, the acoustic energy implementation requires a strategy to optimize the microreactor from an ultrasound viewpoint during its design. In this work, we present a simple analytical model that can be used as a guide to achieving a proper acoustic design of stacked microreactors. An example of this methodology was demonstrated through finite element analysis and it was compared with an experimental study found in the literature.

Reduction of tobacco smoke components yield in commercial cigarette brands by addition of HUSY, NaY and Al-MCM-41 to the cigarette rod

The effect of two zeolites, HUSY, NaY and a mesoporous synthesized Al-MCM-41 material on the smoke composition of ten commercial cigarettes brands has been studied. Cigarettes were prepared by mixing the tobacco with the three powdered materials, and the smoke obtained under the ISO conditions was analyzed. Up to 32 compounds were identified and quantified in the gas fraction and 80 in the total particulate matter (TPM) condensed in the cigarettes filters and in the traps located after the mouth end of the cigarettes. Al-MCM-41 is by far the best additive, providing the highest reductions of the yield for most compounds and brands analyzed. A positive correlation was observed among the TPM and nicotine yields with the reduction obtained in nicotine, CO, and most compounds with the three additives. The amount of ashes in additive free basis increases due to the coke deposited on the solids, especially with Al-MCM-41. Nicotine is reduced with Al-MCM-41 by an average of 34.4% for the brands studied (49.5% for the brand where the major reduction was obtained and 18.5 for the brand behaving the worst). CO is reduced by an average of 18.6% (ranging from 10.3 to 35.2% in the different brands).

Characterisation of montmorillonites simultaneously modified with an organic dye and an ammonium salt at different dye/salt ratios. Properties of these modified montmorillonites EVA nanocomposites

In this work, a sodium montmorillonite (Na+-Mt) was modified with two molecules simultaneously, an organic dye, methylene blue (MB), and ethyl hexadecyl dimethyl ammonium (EHDDMA). The synthesised organo-montmorillonites (OMt) combining different proportions of the two molecules were thoroughly characterised and mixed with ethylene vinyl acetate copolymer (EVA) in order to check the ability of these OMt as pigments and reinforcing additives. The synthesised OMt combining both surfactants, MB and EHDDMA, present higher interlayer distances than those with only MB, which were employed in previous works as nanopigments. When these OMt were incorporated in the EVA matrix, the obtained clay polymer nanocomposites (CPN) showed a high exfoliation degree of the OMt in the polymer, in such a way that at 80% of the cationic exchange capacity (CEC) of the Mt exchanged with EHDDMA, most of the OMt was exfoliated. Moreover, all the obtained CPN showed an increase in the Young's Moduli compared to the EVA reference, and especially those containing higher amounts of MB. The thermal stability of the CPN also increases with the MB content, compared to other CPN including conventional surfactants. The hiding power and colouring power achieved in the CPN are higher even with a much lower load of MB when EHDDMA is exchanged in the Mt.

Comparison between the mainstream smoke of eleven RYO tobacco brands and the reference tobacco 3R4F

In this study 11 commercial roll-your-own (RYO) tobacco brands sold in Spain and the reference tobacco 3R4F have been smoked and several components of the mainstream tobacco smoke have been analyzed. Cigarettes were prepared using commercial tubes, and were smoked under smoking conditions based on the ISO 3308. The gaseous and condensed fractions of the smoke from RYO brands and 3R4F have been analyzed and compared. RYO tobaccos, as opposed to 3R4F, present lower amounts of condensed products in the traps than in the filters. In general, RYO tobaccos also provide lower yields of most of the compounds detected in the gas fraction. The yield of CO is between 15.4 and 20.4 mg/cigarette. In most of the cases studied, RYO tobaccos deliver higher amounts of nicotine than the 3R4F tobacco. On average, the yield of the different chemical families of compounds appearing in the particulate matter retained in the cigarette filters tends to be around three times higher than those obtained from 3R4F, whereas similar values have been obtained in the particulate matter retained in the traps located after the filters. It can be concluded that RYO tobaccos are not less hazardous than the reference tobacco, which may be contrary to popular belief.

Analysis of the Connecting Zone between Consecutive Sections in Distillation Columns Covering Multiple Feeds, Products and Heat Transfer Stages

In the present work, we provide a systematic analysis about all tine streams involved in the zone connecting two consecutive sections for the design of distillation columns with different thermal feed conditions, product extractions and heat additions or withdrawals. This analysis allows a better understanding of what happens on a feed or side draw (of mass or energy) stage, what compositions are or are not in equilibrium, and the impact on internal liquid and vapor flows.

Pyrolysis and combustion study of flexible polyurethane foam

The thermal degradation of flexible polyurethane foam has been studied under different conditions by thermogravimetric analysis (TG), thermogravimetric analysis-infrared spectrometry (TG-IR) and thermogravimetric analysis-mass spectrometry (TG-MS). For the kinetic study, dynamic and dynamic+isothermal runs were performed at different heating rates (5, 10 and 20 °C min−1) in three different atmospheres (N2, N2:O2 4:1 and N2:O2 9:1). Two reaction models were obtained, one for the pyrolysis and another for the combustion degradation (N2:O2 4:1 and N2:O2 9:1), simultaneously correlating the experimental data from the dynamic and dynamic+isothermal runs at different heating rates. The pyrolytic model considered consisted of two consecutive reactions with activation energies of 142 and 217.5 kJ mol−1 and reaction orders of 0.805 and 1.246. Nevertheless, to simulate the experimental data from the combustion runs, three consecutive reactions were employed with activation energies of 237.9, 103.5 and 120.1 kJ mol−1, and reaction orders of 2.003, 0.778 and 1.025. From the characterization of the sample employing TG-IR and TG-MS, the results obtained showed that the FPUF, under an inert atmosphere, started the decomposition breaking the urethane bond to produce long chains of ethers which were degraded immediately in the next step. However, under an oxidative atmosphere, at the first step not only the urethane bonds were broken but also some ether polyols started their degradation which finished at the second step producing a char that was degraded at the last stage.

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.

Rigorous design of distillation columns using surrogate models based on Kriging interpolation

The economic design of a distillation column or distillation sequences is a challenging problem that has been addressed by superstructure approaches. However, these methods have not been widely used because they lead to mixed-integer nonlinear programs that are hard to solve, and require complex initialization procedures. In this article, we propose to address this challenging problem by substituting the distillation columns by Kriging-based surrogate models generated via state of the art distillation models. We study different columns with increasing difficulty, and show that it is possible to get accurate Kriging-based surrogate models. The optimization strategy ensures that convergence to a local optimum is guaranteed for numerical noise-free models. For distillation columns (slightly noisy systems), Karush–Kuhn–Tucker optimality conditions cannot be tested directly on the actual model, but still we can guarantee a local minimum in a trust region of the surrogate model that contains the actual local minimum.

Study of the emissions from pyrolytic and oxidative thermal decomposition of PVC

Polyvinyl chloride (PVC) is one of the plastics most extensively used due to its versatility. The demand of PVC resin in Europe during 2012 reached 5000 ktonnes1. PVC waste management is a big problem because of the high volume generated all over the world and its chlorine content. End-of-life PVC is mainly mixed with municipal solid waste (MSW) and one common disposal option for this is waste-to-energy incineration (WtE). The presence of plastics such as PVC in the fuel mix increases the heating value of the fuel. PVC has two times higher energy content than MSW ‒around 20 MJ/kg vs 10 MJ/kg, respectively. However, the high chlorine content in PVC resin, 57 wt.%, may be a source for the formation of hazardous chlorinated organic pollutants in thermal processes. Chlorine present in the feedstock of WtE plants plays an important role in the formation of (i) chlorine (Cl2) and (ii) hydrochloric gas (HCl), both of them responsible for corrosion, and (iii) chlorinated organic pollutants2. In this work, pyrolytic and oxidative thermal degradation of PVC resin were carried out in a laboratory scale reactor at 500 ºC in order to analyze the influence of the reaction atmosphere on the emissions evolved. Special emphasis was put on the analysis of chlorinated organic pollutants such as polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and other related compounds like polychlorobenzenes (PCBzs), polychlorophenols (PCPhs) and polycyclic aromatic hydrocarbons (PAHs). Another objective of this work was to compare the results with those of a previous work3 in which emissions at different temperatures in both pyrolysis and combustion of another PVC resin had been studied; in that case, experiments for PCDD/Fs emissions had been performed only at 850 ºC.

Red de seguimiento e indicadores de calidad de la titulación máster universitario en prevención de riesgos laborales

El profesorado de la red participó durante el curso 2013/14 en un proyecto para el seguimiento e indicadores de calidad de la titulación máster universitario en prevención de riesgos laborales. Este Máster comenzó a impartirse en la Escuela Politécnica Superior de la Universidad de Alicante en el curso 2012/13. En el curso 2015/16 al Máster en prevención de riesgos laborales le corresponde la renovación de su acreditación, en base a los resultados de la docencia de los cursos 2013/14 y 2014/15, por lo que los resultados del presente proyecto son de interés para la renovación de la acreditación de la titulación.

Contribución de las actividades prácticas en la evaluación de asignaturas pertenecientes a grados de ciencias experimentales

Se presentan los resultados del proceso de evaluación de algunas asignaturas experimentales incluidas dentro de diferentes títulos, Grado en Biología, Grado en Ciencias del Mar, Grado en Químicas, Grado en Óptica y Optometría y Grado en Ingeniería Química, en las que el Departamento de Química Orgánica de la Universidad de Alicante está involucrado. Los resultados recogidos muestran como la evaluación continua y la realización de una prueba final influyen en la calificación final de la asignatura. Además, dentro de la evaluación continua se han diseñado diferentes actividades, considerando la realización de prácticas de laboratorio, la resolución de problemas y presentación de los mismos, así como la entrega de cuestionarios y ejercicios a través de plataformas virtuales. Se presenta el análisis de como cada una de estas actividades contribuye en el resultado final obtenido por los estudiantes, mostrando que las actividades de carácter práctico influyen en la calificación final de una manera más positiva.

Analysis of pollutants evolved from combustion and pyrolysis of flexible polyurethane foam in a laboratory furnace

Resumen del póster presentado en PIC2015 – the 14th International Congress on Combustion By-Products and Their Health Effects, Umeå, Sweden, 14-17 June 2015.