Analysis of Spontaneous Ignition of Grass: Chemical Oxidation and Water Vapor Sorption

Self-heating of biomass by chemical oxidation, which can cause spontaneous ignition, is a safety and management concern. This process can be accelerated by aerobic fermentation and water vapor sorption. The chemical oxidation and water vapor sorption of grass were studied in a laboratory oven, measuring the variations in weight and the internal temperature of a sphere with grass within a flexible polymeric network. Both processes were simulated to prove that the proposed mathematical model could fit the experimental data. It was observed that the water vapor sorption capacity of the grass was high, so the experimental increase in the internal temperature of a spherical body was around 47 K, from 73°C to 120°C. This fact can be very important because the chemical oxidation of grass accelerates at high temperatures. For scaling, simulation programs were used to study the sorption and oxidation processes with an increase in internal temperature in spherical bodies and infinite plane slabs. These results can be used to obtain those of other geometric symmetries by interpolation. It was deduced that at 70°C and with vapor sorption, the ignition time can be around 3 days to 5 days, while without vapor sorption, the ignition times can be around 110 days to 140 days. For 35°C the ignition times with vapor sorption can be around 12 days to 18 days, while without vapor sorption the ignition times can be around 3700 days to 4500 days. These results can be of interest for warehouses of similar biomass and for forestry research and management groups of wildfires.Funding is from the University of Alicante. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

Aportacions al coneixement dels ortòpters (Insecta: Orthoptera) de la Garrotxa i l'Alta Garrotxa (Girona, Espanya)

Es donen a conèixer noves cites d'ortòpters per la comarca de la Garrotxa i l'espai d'interès natural de l'Alta Garrotxa. Se citen 6 tàxons nous per la Garrotxa, 1 nova espècie per l'Alt Empordà i 17 espècies noves per l'Alta Garrotxa. Així mateix, es comenten aspectes sobre la seva biologia, ecologia i fenologia observada al camp. Es discuteix la importància de les deteccions sonores i l'estudi i enregistrament de les estridulacions.New records of Orthoptera in Garrotxa and Alta Garrotxa are presented. 6 taxa are added to Garrotxa county, 1 to Alt Empordà county and 17 to the Alta Garrotxa Area of Natural Interest. In addition, some aspects about their biology, ecology and field phenology are presented. The importance of detection, study and registration of stridulation is discussed

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.The authors thank the Spanish Ministry of Education Culture and Sport and the research projects CTQ2013-41006 from the Spanish Ministry of Economy and Competitiveness and PROMETEOII/2014/007 from the Valencian Community Government for the support provided

Les xarxes de ciutats : l'estructura de les megaregions a Europa

En aquest article s'estudien les megaregions des del punt de vista de la teoria de xarxes i la 'termo-economia'. Els resultats mostren que les megaregions incrementen els seus nivells de complexitat, augmentant el grau de policentricitat, i incrementant els nivells d'eficiència i estabilitat. La conclusió és que tant la seqüència teòrica com els càlculs empírics que l'avalen, suggereixen que les megaregions evolucionen cap a una estructura urbana més sostenible.En este artículo se estudian las megarregiones desde el punto de vista de la teoría de redes y la 'termo-economía'. Los resultados muestran que las megarregiones incrementan sus niveles de complejidad, aumentando el grado de policentricitat, e incrementando los niveles de eficiencia y estabilidad. La conclusión es que tanto la secuencia teórica como los cálculos empíricos que la avalan, sugieren que las megarregiones evolucionan hacia una estructura urbana más sostenible

Polymorphism of Sildenafil: A New Metastable Desolvate

A new anhydrous polymorph of the free base of sildenafil and two solvates (acetonitrile and propanenitrile) have been discovered and fully characterized. The new polymorph can be considered a desolvate of the acetonitrile solvate and is related to the most stable form I by morphotropism. The new polymorph can only be obtained by desolvation of the acetonitrile solvate. Thus, this study is a new example of the importance of this multicomponent family of solid forms in the discovery of new polymorphs of active pharmaceutical ingredients

Morphotropism and 'Quasi-Isostructurality' in the Three High Z′ Concomitant Polymorphs of Efinaconazole

The crystal structures of the three efinaconazole anhydrous forms have been solved by single-crystal X-ray diffraction showing a very rare case of nearly isostructural polymorphism. The analysis of their crystal structures revealed that forms I and III are 'quasi-isostructural' polymorphs and are morphotropically related to form II. The identical conformational and supramolecular environment can explain the concomitant polymorphism phenomenon observed for this important active pharmaceutical ingredient

Potential kinetic model for thermal decomposition of complex organic compounds: Significance of parameters and engineering application

This paper analyzes the significance of the apparent activation energies and the reaction orders in potential kinetic models, their great interrelation and their influence in the design of reactors. The interrelation between the pre-exponential factor, the apparent activation energy and the reaction order is considered for a single reaction model and for a scheme of reactions. In addition, some simulated results of schemes of reactions were correlated satisfactorily by a single reaction model with surprising results concerning the activation energy and the reaction order. The potential model is compared with other correlation models proposed in literature. Finally, an analysis is presented on the use of the kinetic parameters for the design of industrial reactors.Support for this work was provided by PROMETEO/2009/043/FEDER of Generalitat Valenciana (Spain) and CTQ2008-05520 (Spanish MCI/research)

Pollutant emissions from the pyrolysis and combustion of viscoelastic memory foam

Thermal degradation of viscoelastic memory foam (VMF) in a horizontal laboratory scale reactor has been studied. Pyrolysis and combustion experiments under sub-stoichiometric conditions were performed at four different temperatures (550 °C, 650 °C, 750 °C and 850 °C) for the determination of pollutants. Analyses of gas and semivolatile compounds, including polychlorodibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) are shown. From the results, it was deduced that pyrolytic conditions favor the formation of PAHs, methane, ethylene, NH3 and dl-PCBs, whereas the presence of oxygen involves a higher emission of PCDD/Fs and simple N-containing compounds such as NO and HCN. The toxic levels calculated for PAHs, PCDD/Fs and dl-PCBs in all cases were low confirming that the incineration of VMF mattress waste could be a good option for waste management. Nevertheless, relatively high emissions of NO, NH3 and HCN were obtained and their reduction must be considered.Support for this work was provided by the 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)