Kinetic analysis of Malaysia type biomasses via thermogravimetric analyser (TGA)

The kinetic behaviour of biomass pyrolysis samples was successfully studied via thermogravimetric analysis. The biomass samples were empty fruit bunch, oil palm trunk, rice husk, coconut copra, sawdust, coconut shell, sugarcane bagasse, and wood bark. The analysis was performed in a nitrogen atmosphere from 30 to 700°C. The effect of heating rate on kinetic behaviour of biomass at two different high heating rates was evaluated at 40°C/min (HR1) and 80°C/min (HR2). The kinetic parameters of biomass samples such as pre-exponential factor (s-1), activation energy (kJ/mol), and reaction order (n) were determined using one-step global kinetic model. The wood bark sample has the lowest activation energy (38.14 kJ/mol), while coconut copra was reported for the highest activation energy (145.42 kJ/mol). High positive activation energy was achieved at a higher heating rate (HR2) than at lower heating rate (HR1) for biomass samples

Catalytic upgrading of biomass-derived pyrolysis vapour over metal-modified HZSM-5 into BTX: a comprehensive review

This paper provides an updated and comprehensive review on the catalytic upgrading of biomass-derived pyrolysis vapours over metal-modified HZSM-5 catalyst into bio-aromatic hydrocarbons. The catalytic upgrading of biomass pyrolysis vapours seems to be a promising technology in generating gasoline-type bio-aromatic hydrocarbons, i.e. benzene, toluene and xylene (BTX). Biomass-derived raw pyrolysis oil has high oxygenated compounds that deteriorate pyrolysis oil properties and limits its applications. Metal modification of hydrogen exchanged Zeolite Socony Mobil Five (HZSM-5) catalyst has gained attention in a biomass pyrolysis research area due to the beneficial effects on upgrading the oxygenated pyrolysis vapours into BTX-enriched pyrolysis oils. The influence of metals (alkali and alkaline earth metals, transition metals and rare earth metals) as bi-functional or multifunctional activity on HZSM-5 catalyst during pyrolysis has been addressed. The effect of reaction temperature, the type of metals, metal contents, the silica-to-alumina ratio of catalyst and the catalyst-tobiomass ratio are critically discussed for maximum production of monocyclic aromatic hydrocarbons during the upgrading of pyrolysis vapours. Finally, concluding remarks on metal-modified zeolite catalyst and future recommendation in upgrading biomass pyrolysis vapours are presented

Thermal characterization of Malaysian biomass via thermogravimetric analysis

In this work, thermal degradation behavior of six local biomasses such as empty fruit bunch, rice husk, coconut pulp, saw dust, coconut shell, and sugarcane bagasse in Malaysia via pyrolysis was studied. The pyrolysis process was carried out from 25 to 700 °C under nitrogen atmosphere flowing at 150 ml/min via a thermogravimetric analyzer. The effect of biomass type was investigated on pyrolysis behavior. The particle size of biomass was in the range of 0.3 ≤ dp1 < 0.5 mm, whereas the heating rate was fixed at 80 °C/min. The thermogravimetric analysis (TGA) data were divided into three phases of degradation: moisture evolution, hemicellulose-cellulose degradation, and lignin degradation. The results showed that all biomass samples degraded between 25 and 170 °C in Phase I of moisture evolution. Among the biomass samples, coconut pulp achieved the highest mass loss (81.9%) in Phase II of hemicellulose-cellulose degradation. Lignin in all biomass samples gradually degraded from 450 to 700 °C in Phase III of lignin degradation. This study provides an important basis in understanding the intrinsic thermochemistry behind degradation reactions

Interaction insight of pullulan-mediated gamma-irradiated silver nanoparticle synthesis and its antibacterial activity

The production of pure silver nanoparticles (Ag-NPs) with unique properties remains a challenge even today. In the present study, the synthesis of silver nanoparticles (Ag-NPs) from natural pullulan (PL) was carried out using a radiation-induced method. It is known that pullulan is regarded as a microbial polysaccharide, which renders it suitable to act as a reducing and stabilizing agent during the production of Ag-NPs. Pullulan-assisted synthesis under gamma irradiation was successfully developed to obtain Ag-NPs, which was characterized by UV-Vis, XRD, TEM, and Zeta potential analysis. Pullulan was used as a stabilizer and template for the growth of silver nanoparticles, while gamma radiation was modified to be selective to reduce silver ions. The formation of Ag-NPs was confirmed using UV-Vis spectra by showing a surface plasmon resonance (SPR) band in the region of 410-420 nm. As observed by TEM images, it can be said that by increasing the radiation dose, the particle size decreases, resulting in a mean diameter of Ag-NPs ranging from 40.97 to 3.98 nm. The XRD analysis confirmed that silver metal structures with a face-centered cubic (FCC) crystal were present, while TEM images showed a spherical shape with smooth edges. XRD also demonstrated that increasing the dose of gamma radiation increases the crystallinity at a high purity of Ag-NPs. As examined by zeta potential, the synthesized Ag-NP/PL was negatively charged with high stability. Ag-NP/PL was then analysed for antimicrobial activity against Staphylococcus aureus, and it was found that it had high antibacterial activity. It is found that the adoption of radiation doses results in a stable and green reduction process for silver nanoparticles

Pineapple peel based biocomposites for green packaging

In this research, pineapple peel fiber (PAPF) based low density polyethylene (LDPE) biocomposites for green packaging was studied. The PAPF was first being treated with alkali before compounded with LDPE. Then, the mixture was compounded using twin screw extruder and the test samples were prepared using hot press machine. The compatibility of the PAPF as biocomposites was observed through the characterization and biodegradation analysis. Melt flow index (MFI) analysis was conducted to determine the process ability of the biocomposites. As the fiber loading in the biocomposites increases, the MFI values were decreased. The amount of water absorption was increased with the increases of PAPF loading due to the higher cellulose content. The biocomposites was buried in the soil for a month for biodegradation analysis and the highest PAPF/LDPE loading biocomposites degraded the most

A review on the effects of flame retardant additives towards the environment and human health

Flame retardant additives (FRAs) are normally the addition of chemicals that function to prevent or slow the spread of fires. These chemicals are used in consumer products and industries and could retain in the environment even after several decades. The toxicity mechanism and risk assessment methods of FRAs are also discussed in this paper. Papers from Scopus, Elsevier, Environmental health perspectives (EHP), Research gate, Semantic scholar, Hindawi, and Pubmed from 2003 to recent years were reviewed to provide some views on the possible risks of FRAs and their pathways into our environment as well as into human body. While FRAs could enter the environment during the manufacturing process and the usage period, consumer items are treated with FRAs, through waste streams, during illegal open burning of solid wastes, from incineration plants from landfill leachate and wastewater treatment plant (WWTP) sludge. FRAs are hazardous to humans and the environment, therefore, toxicology assessment should also be consistently conducted on the latest FRAs to ensure that they would not have adverse effects on humans and the environment

Explosion characteristics assessment of premixed biogas/air mixture in a 20-L spherical vessel

The understanding of biogas explosion characteristics is needed to describe the severity of the explosion. Biogas is a flammable gas and will explode when ignited. This study reports the experimental results on biogas explosion characteristics in a standard 20-L spherical vessel under quiescent conditions using electric spark (10 J) as an ignition source. Computational Fluid Dynamic (CFD) code FLame ACcelaration Simulator (FLACs) was used to simulate the biogas explosion based on the experimental case study. The dependence of explosion characteristics such as explosion pressure (Pmax), rate of pressure rise (dP/dt), and deflagration index (KG), on biogas concentration and carbon dioxide, CO2 composition is demonstrated. The data allow for the evaluation of the potential severity of biogas explosion, which in turn helps engineers design the explosion mitigation and prevention device related to this gas. The experimental data reported from this study concluded that Pmax = 8–8.50 bar, the dP/dt = 100–400 bar/ms and the KG = 32.7–121 bar m/ms were recorded at equivalence ratio, (ER) = 1.2 with CO2 composition in the biogas = 30% vol/vol. It was found that the severity of the biogas explosion increased proportionally with the biogas concentration. On the contrary, the explosive intensity was weakened by increasing the CO2 concentration due to the physical effects of CO2 and thermal instability. This study also recorded that the biogas explosion was categorized under hazard level = St-3 indicating a catastrophic explosion. These data are important for preventing and mitigating the biogas explosion

The effect of precursor concentration on the particle size, crystal size, and optical energy gap of CexSn1â’xO2 nanofabrication

In the present work, a thermal treatment technique is applied for the synthesis of CexSn1−xO2 nanoparticles. Using this method has developed understanding of how lower and higher precursor values affect the morphology, structure, and optical properties of CexSn1−xO2 nanoparticles. CexSn1−xO2 nanoparticle synthesis involves a reaction between cerium and tin sources, namely, cerium nitrate hexahydrate and tin (II) chloride dihydrate, respectively, and the capping agent, polyvinylpyrrolidone (PVP). The findings indicate that lower x values yield smaller particle size with a higher energy band gap, while higher x values yield a larger particle size with a smaller energy band gap. Thus, products with lower x values may be suitable for antibacterial activity applications as smaller particles can diffuse through the cell wall faster, while products with higher x values may be suitable for solar cell energy applications as more electrons can be generated at larger particle sizes. The synthesized samples were profiled via a number of methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). As revealed by the XRD pattern analysis, the CexSn1−xO2 nanoparticles formed after calcination reflect the cubic fluorite structure and cassiterite-type tetragonal structure of CexSn1−xO2 nanoparticles. Meanwhile, using FT-IR analysis, Ce-O and Sn-O were confirmed as the primary bonds of ready CexSn1−xO2 nanoparticle samples, whilst TEM analysis highlighted that the average particle size was in the range 6−21 nm as the precursor concentration (Ce(NO3)3·6H2O) increased from 0.00 to 1.00. Moreover, the diffuse UV-visible reflectance spectra used to determine the optical band gap based on the Kubelka–Munk equation showed that an increase in x value has caused a decrease in the energy band gap and vice versa

Vented gas explosions

Explosion venting technology is widely accepted as the effective constructional protection measures against gas and dust explosions.The key problem in venting is the appropriate design of the vent area necessary for an effective release of the material i.e. the pressure developed during explosion did not cause any damage to the plant protected.Current gas explosion vent design standards in the USA (NFPA68, 2002) and European (2007) rely on the vent correlation first published by Bartknecht in 1993 (Siwek, 1996).N FPA 68 also recommends the correlation of Swift (Swift,1983)at low overpressures. For a vent to give no increase in overpressure other than that due to the pressure difference created by the mass flow of unburnt gases through the vent, the vent mass flow rate is assumed to be equal to the maximum mass burning rate of the flame and this consideration should be used as the design mass flow through the vent. Two different methods ( Method I and Method 2) have been proposed based on the Sμ and Sμ (E-1) to describe the maximum mass burning rate given as, mb = ASμpμ=CdeA(2pPμred)o.5 mb =ASgPm =AgSμ(E-I)P μ=Cde4,(2pu Pred)0,5 (2) The equation given in (2) is slightly different from (1) as is about 6.5 times the mass flow of the first method as it takes the effect of (E-1) where E is the expansion ratio. A critical review were carried out for the applicability, validity and limitation on the venting correlations adopted in NFPA 68 and European Standard with 470 literature experimental data, covering a wide range of values for vessel volume and geometries, bursting vent pressure, Pv L/D ratio, maximum reduced pressure, Pred and ignition location. The fuels involved are methane, propane, hydrogen, town gas, ethylene, acetone/air mixtures with the most hazardous near-stoichiornetric fuel-air concentration. Besides, Molkov's equation (Molkov, 2001) which is regarded as alternative venting design offered in NFPA 68 and Bradley and Mitcheson's equation for safe venting design were also analysed on the experimental data for their validity and limitation as well as the proposed methods. From the results, it is clear that Bartknecht's equation gave a satisfactory result with experimental data for K <-5 and Swift's equation (Swift, 1983) can be extended to wider range for Pred> 200 mbar, providing the parameter PV is added into the equation. Method 2 gave a good agreement to most of the experimental data as it followed assumptions applied for correlations given by Bradley and Mitcheson for safe venting design (Bradley and Mitcheson, 1978a,B radley and Mitcheson, 1978b). It is also proven that the vent coefficient, K is confident to be used in quantifying the vessel's geometry for cubic vessel and the use of As/Av term is more favourable for non-cubic vessels. To justify the validity and applicability of the proposed methods, series of simply vented experiments were carried out, involving two different cylindrical volumes i.e. 0.2 and 0.0065 M3. It is found that self acceleration plays important role in bigger vessel in determining the final Pmax inside the vessel. Method 2 gave closer prediction on Pmax in respect with other studied correlations. The investigation of vented gas explosion is explored further with the relief pipe been connected to the vessel at different fuel/air equivalence ratios, ignition position and Pv. The results demonstrate that the magnitude of Pmax was increased corresponding to the increase of Pv- From the experiments,it is found that peak pressure with strong acoustic behaviour is observed related to increase in Pv and in some cases,significant detonation spike was also observed particularly in high burning velocity mixtures. It is found that substantial amount of unburnt gases left inside the vessel after the vent burst is the leading factor in increase of Pmax for high burning velocity mixtures at centrally ignited. The associate gas velocities ahead of the flame create high unburnt gas flows conditions at entry to the vent and this give rise to high back pressures which lead to the severity in final Pmax inside the vessel. It was observed that end ignition leads to a higher explosion severity than central ignition in most cases, implying that central ignition is not a worst-case scenario in gas vented explosions as reported previously

The influence of vessel volume and equivalence ratio in vented gas explosion

Experiments of vented gas explosions involving two different cylinder vessel volumes (0.2 and 0.0065 m3) were reported. It was found that self-acceleration and larger bulk flame trapped inside the vessel are the main factor enhancing the overpressure attained in 0.2 m3 vessel. There was about 2 to 7 times increase in ratio of pressure and flame speeds on both vessels at the same equivalence ratio and K which can be considered as turbulent enhancement factor, ß. Hot spot or auto ignition is responsible to the deflagration to detonation