Highly efficient metal-organic framework based intumescent poly(L-lactic acid) towards fire safety, ignition delay and UV resistance

Developing multifunctional biodegradable PLA with ignition delay, high efficient fire retardancy, and UV resistance properties is a challenging task owing to its high flammability, and mutually exclusive phenomenon between the latter two properties. In this work, we report a superior efficient synergistic action combining piperazine pyrophosphate (PAPP) and a Co based metal-organic framework (ZIF-67). Results illustrated that with merely 0.06 wt% ZIF-67, intumescent PLA containing 4.96 wt% PAPP reached UL-94 V0 rating. The PLA/4.9PAPP/0.1MOF sample possessed a limiting oxygen index (LOI) value at 33 %, exhibited a 28 % reduction in peak heat release rate (pHRR) and a 67 % increase in fire propagation index (FPI). Moreover, the presence MOF delayed the ignition time of PLA by 12 s due to the highly porous structure of MOF and its chemical heat-sink performance. Insightful reaction to fire mechanism in the condensed phase via TG-FTIR and Raman revealed that a crack free protective intumescent char layer with higher graphitization degree was formed, which effectively enhanced the barrier effect and minimize the heat and fuel transfer. In addition, the UV resistance of PLA composites is enhanced, remaining at and below 5 % transmittance in the UVA and UVB areas. This work provides a green production way of multifunctional degradable materials and broadens their application fields.

Bioethanol from wheat straw hydrolysate solubility and stability in waste cooking oil biodiesel/diesel and gasoline fuel at different blends ratio

The work focuses on studying the solubility and stability of dissolved bioethanol as a fuel additive in different fuel blends of gasoline, diesel, 50% diesel/50% biodiesel. Dissolved ethanol fuel appears as particles with a unique size distribution inside the whole fuel blends, and its stability was measured in this work. Bioethanol dissolved fuel particles stability was improved after blending the bioethanol with 50% diesel/50% biodiesel than pure diesel or pure gasoline fuel alone. The obtained results reveal that the lowest bioethanol particles stability was obtained when commixed with gasoline and the suspended ethanol particles completely accumulated at different concentrations of bioethanol in the fuel blends of 2%, 4%, 6%, 8%, 10%, and 12% by volume after 1 h of mixing time. Furthermore, the measured data of the bioethanol particles size distribution reveals that the suspended stability in the diesel blend improve slightly for all bioethanol concentrations of 10%, 15%, 20%, 25%, and 30% by volume. While the bioethanol concentrations of 5% show acceptable particles stability and size distribution during the whole experiments time. Obtained results show that bioethanol suspended particles stability was enhanced for 50% diesel/50% biodiesel blend with different bioethanol concentrations of 5%, 10%, 15%, 20%, 25%, and 30% by volume basis. However, the size of the particles increased as the bioethanol concentration rose with the passage of time.

Ignition hazard of non-metallic dust clouds exposed to hotspots versus electrical sparks

Non-metallic combustible dusts contribute to more than 50% of dust explosion accidents. Almost 38% of dust explosion accidents relate to mechanical malfunction. Compared to electric sparking as an ignition source, the ignition hazard of non-metallic dust clouds exposed to simulated hotspots during mechanical malfunction has received little attention in the literature. Minimum ignition temperature of hotspots (MITH) for corn starch, wood dust, and polymethyl methacrylate (PMMA) dust fall within a narrow range from 710 to 745 °C although large differences in minimum ignition energy (MIE) were evident. A much narrower dust concentration range (around 1500 g/m³) was observed for MITH than for MIE. A longer ignition delay time when exposed to hotspots also indicated lower ignition hazard compared to ignition by electric sparking. Whether exposed to hotspots or electric sparks, average flame spread velocity (FSV) of PMMA dust was much higher than that of corn starch and wood dust. Once a dust cloud was ignited, pulsating flame propagation was similar for hotspots and electric sparking, but average FSV was higher for hotspots than for electric sparks, due to continuous radiation from the ignition source. At higher dust loadings, layer fires could occur due to sedimentation of many ignited and unburned particles exposed to hotspots.

Techno-economic assessment of coconut biodiesel as a potential alternative fuel for compression ignition engines

Over the past years, there were dramatic improvements in identifying and assessing various feedstocks for the production of biodiesel fuels. To promote a particular feedstock as a renewable source of energy, it is important to analyze their energy, economic, and engine performance characteristics. The current work attempts to evaluate the net energy and economic indices for both fossil diesel and coconut-blended diesel (B20) considering the diesel consumption by the Indian railways. Further, we present the experimental results of a multi-cylinder diesel engine operated with neat coconut biodiesel (B100) and fossil diesel at various load and speed conditions. The engine experiments reveal that the coconut biodiesel exhibits leaner combustion and shorter ignition delay than fossil diesel. Lower amount of carbon monoxide, hydrocarbon, and smoke emission is observed in the case of coconut biodiesel, with higher levels of nitric oxide (14%) and fuel consumption than diesel. The coefficient of variation in indicated mean effective pressure is within the range of better driveability zone for both the fuels at all test conditions. Overall the engine performance, emission and combustion results with neat coconut biodiesel are favorable with a penalty in NO emission at high load conditions. The techno-economical study highlights higher production cost per liter of B20 than the cost of fossil diesel. However, the net energy ratio (NER) for B20 is 1.021, favoring higher output than diesel and thus lowers the dependency on crude oil.

Effect of alumina nano additives into biodiesel-diesel blends on the combustion performance and emission characteristics of a diesel engine with exhaust gas recirculation

In the present study, the combined effect of alumina nanoparticles into the Calophyllum inophyllum biodiesel blend and exhaust gas recirculation on the combustion, performance, and emission characteristics of a diesel engine was investigated. The alumina (Al₂O₃) nanoparticles with the mass fraction of 40 ppm were dispersed into the C. inophyllum biodiesel blend (20% of C. inophyllum biodiesel + 80% of diesel (CIB20)) by the ultrasonication process. Further, the exhaust gas recirculation was adopted to control the oxides of nitrogen (NOx) emissions of a diesel engine. The experiments were conducted on a single cylinder diesel engine with the diesel, CIB20, 20% of C. inophyllum biodiesel + 80% of diesel + 40 ppm Al₂O₃ nanoparticles (CIB20ANP40), CIB20 + 20% exhaust gas recirculation (EGR), and CIB20ANP40 + 20% EGR fuel samples at different load conditions. The results reveal that brake thermal efficiency of CIB20ANP40 fuel increased by 5.04 and 7.71% compared to the CIB20 and CIB20ANP40 + 20% EGR fuels, respectively. The addition of alumina nanoparticles to the CIB20 fuel, CO, and hydrocarbon (HC) emissions were was reduced compared to the CIB20 fuel. The smoke opacity was decreased with the addition of alumina nanoparticles to the CIB20 fuel by 7.3% compared to the CIB20 fuel. The NOx emissions for the CIB20ANP40 + 20% EGR fuel was decreased by 36.84, 31.53, and 17.67% compared to the CIB20, CIB20ANP40, and CIB20 + 20% EGR fuel samples at full load condition.

Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture

The ignition delay times of methane/air mixture diluted by N₂ and CO₂ were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300–2100 K, pressure range of 0.1–1.0 MPa, equivalence ratio range of 0.5–2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N₂ or CO₂ results in increasing ignition delays and the inhibition effect of CO₂ on methane/air mixture ignition is stronger than that of N₂. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N₂ and CO₂ on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N₂ and CO₂ show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N₂ or CO₂.