Production Of Toxic Gases Research Articles

A novel conductive nano-based flame-retardant coating: Preparation and its application for cotton fabric

A novel coating consisting of polyvinyl alcohol (PVA), folic acid (FA), and polyaniline nanoparticles (PANI) was applied to cotton fabric (CF) to enhance its flame retardancy, thermal stability, and electrical properties. The results from different flammability tests indicated a synergistic effect between FA and PANI to enhance the flame retardancy of CF at low weight gain percentages. The rate of burning data displayed that the new coating stopped the flame propagation in CF. The limiting oxygen index (LOI) of CF increased from 18 % to 26.9 % in the sample coated with PVA/FA/PANI. The new coating improved the thermal stability and char residue formation of CF at high temperatures. Moreover, it succeeded in decreasing the smoke density, and the production of toxic gases during treated CF combustion. The tensile strength and colour strength of CF were improved after the addition of PVA/FA/PANI coating. The surface resistance and the AC conductivity of the coated CF were measured. The addition of PVA/FA/PANI to CF increased the AC electrical conductivity due to the growth of conductive paths between the CF and the new coating material.

Experimental and simulation study on performance evaluation for flame retardancy of polyurethane

Rigid polyurethane (RPU) is widely used as an insulation material for construction; however, it induces the production of toxic gases in the case of a fire. Thus, the development of RPU with enhanced flame retardancy is required. In this study, a series of flame retardancy evaluation methods are presented, ranging from a property-based method to a computational fluid dynamics (CFD) numerical method combined with a pilot-scale experiment (PSE). The reliability of the CFD numerical analysis was assessed using the coefficient of determination (R2), and flame-retardant performance was evaluated by comparing the CFD results with the life safety assessment represented by the available safe escape time (ASET). Case studies based on these methods revealed that the peak heat release rate (PHRR) of the RPU1/IFR sample, which was structurally stable and incorporated an intumescent flame retardant was reduced by 243% compared to RPU0, and the limiting oxygen index (LOI) was 18%. In addition, CFD analysis showed that the ASET of RPU0 was 314 s shorter than that of RPU1/IFR. Based on the results of this study, we propose a new safety management system for fire safety using the comparative results of experiments measuring the flame retardancy of RPU and numerical analysis.

Phytic acid-Fe chelate cold-pressed self-forming high-strength polyurethane/marigold straw composite with flame retardance and smoke suppression

The applicability of wood-plastic composites has attracted great attention due to the improved sustainability. However, the fabrication of wood-plastic composites with excellent flame retardance and smoke suppression without compromising the mechanical property remains a great challenge. In this study, marigold straw (MS)-polyurethane (PU) composites (MPCs) were treated with phytic acid (PA) as a flame retardant and iron oxide (Fe2O3) as a smoke suppressor. The oxygen index of the proposed Fe/TMS (treated marigold straw)/PU/PA-10 composite was 27.8, and the total heat release was 12.02 MJ/m2. Fe2O3 and PA formed a mesh chelate in the form of a coordination bond, which provided a highly graphitized solid flame-retardant layer during the combustion process, improving the high-temperature stability of Fe/TMS/PU/PA-10. In addition, Fe2O3 can effectively catalyze the conversion of unsaturated gases, such as CO, into CO2. This is essential to suppress the smoke release and also avoid the production of toxic gases. The phosphate group of PA is cross-linked with the -NCO group of TDI (2,4-Toluene diisocyanate), thus significantly enhanced the physical properties of MPCs. This study provides an environmentally friendly approach to enhancing the flame retardancy and smoke suppression of MPCs.

Recent advances in metal-family flame retardants: a review.

The use of polymer materials is inextricably linked to our manufacturing life. However, most of them are easily combusted in the air and the combustion process generates a large amount of toxic fumes and dangerous smoke. This can result in injuries and property damage, as well as limiting their use. It is essential to enhance the flame-retardant properties and smoke suppression performance by using multiple flame retardants. Metal-based flame retardants have a unique chemical composition. They are environmentally friendly flame retardants, which can impart good smoke suppression, flame retardancy to polymers and further reduce the production of toxic gases. The differences in the compounds formed between the transition metals and the main group metals make them act differently as flame retardants for polymers. As a result, this study presents the research progress and flame-retardant mechanism of flame-retardant polymers for flame retardants from different groups of metals in the periodic table of elements in a systematic manner. In view of the differences between the main group metals and transition metals, the mechanism of their application in flame retardant polymer materials is carefully detailed, as are their distinct advantages and disadvantages. And ultimately, prospects for the development of transition metals and main group metals are outlined. It is hoped that this paper will provide valuable references and insights for scholars in the field.

Effects of waste coffee grounds on the mechanical properties, flame retardancy and toxic gas production of epoxy composites

Waste coffee grounds, a biomaterial with high carbon content, have been suggested as a non-toxic organic flame retardant due to their high char forming and radical scavenging properties. Herein, investigations are conducted on the effects of waste coffee grounds, especially their concentration and particle size, on the mechanical properties, flame retardancy, toxic gas production of epoxy composites. Results reveal that reducing average size of the waste coffee grounds from 46 µm to 16 µm, using freeze-milling or filtering, can reduce peak heat release rate and total heat release of their epoxy composites by 52.0% and 33.7% respectively, exceeding the effectiveness of other bio-based flame retardants such as chitosan, lignin and seashell. More importantly, the fine coffee grounds can achieve the same performance as aluminium trihydrates, the most widely used non-bio flame retardant. Furthermore, the burning rates and emissions of toxic gas have also been greatly reduced, almost entirely suppressing the highly toxic NO2 gas. The findings provide new insights into the effect of particle size of waste coffee grounds on both the mechanical properties and flame retardancy performnance of epoxy composites.

Eco-Friendly Approach for Graphene Oxide Synthesis by Modified Hummers Method.

The aim of this study is to produce graphene oxide using a modified Hummers method without using sodium nitrate. This modification eliminates the production of toxic gases. Two drying temperatures, 60 °C and 90 °C, were used. Material was characterized by X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and Scanning Electron Microscopy. FTIR study shows various functional groups such as hydroxyl, carboxyl and carbonyl. The XRD results show that the space between the layers of GO60 is slightly larger than that for GO90. SEM images show a homogeneous network of graphene oxide layers of ≈6 to ≈9 nm. The procedure described has an environmentally friendly approach.

An Environment-Friendly Rock Excavation Method

Blasting is used as an economical tool for rock excavation in mines. However, part of the explosive energy is converted into elastic waves, resulting in ground vibration and excessive vibration, which may cause damage to nearby buildings. Meanwhile, toxic gases are also produced during the explosion. In this paper, an environment-friendly method for rock excavation is proposed. A series of vibration tests were conducted, and the peak particle velocity was monitored. The results showed that the proposed method can replace the conventional blasting method in mines. Besides that, the vibration caused by the proposed method is much smaller than by the conventional method. By adjusting the direction of the high-pressure gas injection, buildings around the mine can be protected well from vibration. Also, the production of toxic gases during excavation will no longer be a problem. Thus, a milder environmental impact can be achieved. However, the rocks excavated by the proposed method are relatively large, which still need to be broken further. On this issue, further study is required.

Experimental study of intermittent spray cooling on suppression for lithium iron phosphate battery fires

Nowadays, fires caused by thermal runaway (TR) of lithium ion battery (LIB) remains a potential risk in its application. An effective method is urgently required to suppress LIB fires. In this work, a novel cooling method combining dodecafluoro-2-methylpentan-3-one (C 6 F 12 O) agent with intermittent spray cooling (ISC) is proposed for suppression of lithium iron phosphate (LFP) battery fires. Besides, the influence of spray frequency and duty cycle (DC) on spray cooling efficiency are discussed. The results indicate that atomized C 6 F 12 O can effectively suppress LFP fires, reduce the production of toxic gases and heat release rate (HRR). However, after C 6 F 12 O runs out, the rapidly elevated temperature and the release of combustible gases mean that the TR battery requires longer and more efficient cooling. Compared with continuous spray cooling (CSC), ISC not only extends low temperature duration but also decreases the temperature rise rate of the battery. As DC increasing, C 6 F 12 O agent first exhibits an enhancement effect and then an inhibition effect on cooling performance. It is suggested that the optimum DC is 55.4% for the suppression of 14 Ah LFP fires. For the LIBs with higher capacity and higher fraction of active materials, the optimum DC is required to be higher. • A novel cooling strategy is firstly developed for lithium ion battery fires. • Key cooling parameters of thermal runaway suppression with C6F12O are analyzed. • Continuous and intermittent spray modes are compared and investigated. • Duty cycle dominates the cooling performance of intermittent spray cooling.

Effects of Waste Coffee Grounds on the Mechanical Properties, Flame Retardancy and Toxic Gas Production of Epoxy Composites

Effects of Waste Coffee Grounds on the Mechanical Properties, Flame Retardancy and Toxic Gas Production of Epoxy Composites

Prediction of concentration of toxic gases produced by detonation of commercial explosives by thermochemical equilibrium calculations

An adverse effect resulting from explosive mine blasts is the production of toxic nitrogen oxides (NO and NO2) and carbon monoxide (CO). The empirical measurements of the concentration of toxic gases showed that it depends not only on the composition of an explosive and properties of its ingredients but also on several other parameters, such as volume of blasting chamber, explosive charge mass and design, confinement characteristics, surrounding atmosphere, etc. That explains why measured concentrations of toxic gases reported in literature significantly differ.In this paper, we discuss the possibility of theoretical prediction of the concentration of toxic gases by thermochemical equilibrium calculation applying two models: ideal detonation model and deflagration model. It can be demonstrated that thermochemical calculations can provide a good estimation of the measured concentrations and reproduce experimentally obtained effects of additives on the production of toxic gases. It was also found that the ideal detonation model applies to heavily confined explosive charges, while the deflagration model is more suitable for low detonation velocity explosives with light confinement.

Safer modified Hummers’ method for the synthesis of graphene oxide with high quality and high yield

We report on an improved method for the synthesis of graphene oxide based on the modified Hummers’ method proposed by Marcano et al Different steps of the process were optimized. First, the concentration of the reactants and the reaction conditions were optimized to improve the efficiency of the oxidation process of graphite. The Raman spectrum of the GO shows the typical D and G typical of graphite oxide materials. The contribution of the area under the band D to the total area is 98%, confirming that almost the whole graphene was oxidized (high oxidation yield). Furthermore, the quantification of the C 1s XPS spectrum of our GO nanosheets indicates that about 77 wt% of oxygen in the form of oxygenated groups is bonded to the carbon nanosheets. Second, the reaction time was minimized to 12 h, without compromising the quality (as confirmed by micrography). Third, the production of toxic gases has been reduced. Fourth, a thermal treatment was introduced instead of the vacuum drying procedure traditionally used, greatly diminishing the overall graphite oxide processing time that includes: the reactant preparation, graphite oxidation process, rinsing and dispersion procedures, and drying (the drying time went from 12 h to 2 h). Reducing the total time by a half, compared to other methods, is an important finding considering scaling for industrial production.

Sulfur and Nitrogen Gases in the Vapor Streams from Ore Cyanidation Wastes at a Sharply Continental Climate, Western Siberia, Russia

The article presents the results of the study of the vapor streams from sulfide-containing tailings after gold mining by cyanidation (Ursk waste heaps, Kemerovo region, Russia). The gas survey of sulfur dioxide, dimethyl sulfide, dimethyl sulfoxide, carbon disulfide, and N-containing substances concentrations was carried out using a portable device GANK-4 on a series of profiles covering the waste heaps and the surrounding area with simultaneous measurement of temperatures in the air and soil. The concentration maps-schemes of the studied gases in the surface layer were constructed. The high positive correlation of gases between themselves is established, which indicates similar mechanisms of their formation. The electrical resistivity tomography determined the internal structure of the waste heap. Active “breathing” zones were identified in which the maximum fluctuations in the concentrations of sulfur, selenium, and nitrogen-containing compounds in the near-surface air layer were recorded. Such zones are marked with lower resistances in comparison with other areas on the geo-electric profiles. There is an inverse correlation between the resistivity of the tailings and its temperature and a direct correlation between the concentration of gas in the air and the temperature of the soil. High concentrations of CS2, the volatile gas compound of the second hazard class, were found in the concentrations that exceed 6–8 times the daily average norm. Further investigation of the mine tailings seasonal transformation with the production of toxic gases deserves special attention due to high environmental risks and poor knowledge of this problem. The oxidation of ore cyanidation wastes in summer and methylation in winter due to seasonal temperature fluctuation lead to production of gases of great concern including toxic СS2.

Ultrathin iron phenyl phosphonate nanosheets with appropriate thermal stability for improving fire safety in epoxy

Novel ultrathin iron phenyl phosphonate (FePP) nanosheets has been devised and synthesized with appropriate thermal stability for epoxy resin (EP), which was incorporated into EP matrix for preparing uniformly dispersed EP/FePP nanocomposites with intercalated structure. The results indicate that the incorporation of FePP nanosheets greatly improve the thermal stability and residual yield at higher temperature. When the amount of FePP is only 4 wt%, EP/4 wt%FePP nanocomposites is close to V-0 rating with 15 s of t1+t2 value, and LOI value is up to 35.1. Meanwhile, FePP nanosheets availably inhibit the heat release and restrict the smoke and toxic gas production of EP/FePP nanocomposites in combustion, and the PHRR, THR, TSP and COP peak values of EP/4 wt%FePP nanocomposites reduce by 42.6%, 26.3%, 33.3% and 49.8% by comparison with those of pure EP. The outstanding flame retardancy and smoke suppression performances were ascribed to ultrathin FePP nanosheets with appropriate thermal stability, outstanding catalytic carbonization performance of iron and excellent synergistic flame-retardant capability of phosphorus compounds.

Molten chloride salts for next generation CSP plants: Electrolytical salt purification for reducing corrosive impurity level

In this work, electrolysis with a Mg anode is presented to purify the molten chloride salt (MgCl2/KCl/NaCl 60/20/20 mol.%) for reducing its corrosivity. Using a Mg anode, the production of toxic gases like Cl2 on an inert anode (e.g., tungsten) can be avoided. Moreover, compared to an inert anode, a lower over-potential is required to remove the corrosive impurity MgOH+ in the molten salt due to the high reactivity of Mg. In order to evaluate the effect of the salt purification, the cyclic voltammetry (CV) method developed in our previous work is used to in-situ measure the concentration of the corrosive MgOH+ impurity in the molten salt. The CV measurements indicate that the corrosive impurity is efficiently removed by electrolysis. For decreasing the cathode inactivation due to produced MgO on the surface, a pulsed potential applied on the tungsten cathode during electrolysis shows to be promising. This electrochemical salt purification method has shown to be promising by efficiently controlling the corrosivity of the molten chloride salt. The potentiodynamic polarization (PDP) measurements on a commercial high-temperature alloy (Incoloy 800 H) immersed in the molten salt indicate that the corrosion rate of the alloy is significantly reduced due to the salt purification. It could also lead to a reduction of the cost of the conventional salt purification step, structural container materials, and piping in next generation concentrated solar power (Gen3 CSP) plants.

Electrostatic-Interaction-Driven Assembly of Binary Hybrids towards Fire-Safe Epoxy Resin Nanocomposites.

Manganese dioxide (MnO2), as a promising green material, has recently attracted considerable attention of researchers from various fields. In this work, a facile method was introduced to prepare binary hybrids by fabricating three-dimensional (3D) zinc hydroxystannate (ZHS) cubes on two-dimensional (2D) MnO2 nanosheets towards excellent flame retardancy and toxic effluent elimination of epoxy (EP) resin. Microstructural analysis confirmed that the morphologies and structures of MnO2@ZHS binary hybrids were well characterized, implying the successful synthesis. Additionally, the morphological characterization indicated that MnO2@ZHS binary hybrids could achieve satisfactory interfacial interaction with the EP matrix and be well dispersed in nanocomposites. Cone calorimeter test suggested that MnO2@ZHS binary hybrids effectively suppressed the peak of heat release rate and total heat release of EP nanocomposites, performing better than MnO2 or ZHS alone. Condensed-phase analysis revealed that MnO2@ZHS binary hybrids could promote the char density and graphitization degree of char residues and thereby successfully retard the permeation of oxygen and flammable gases. Moreover, through the analysis of gas phase, it can be concluded that MnO2@ZHS binary hybrids could efficiently suppress the production of toxic gases during the degradation of EP nanocomposites. This work implies that the construction of 2D/3D binary hybrids with an interfacial interaction is an effective way to fabricate high-performance flame retardants for EP.

Abatement of SF6 in the presence of NH3 by dielectric barrier discharge plasma

In this paper, the degradation rate, energy yield and the degradation by-products of SF6 was studied when different concentrations of NH3 were added. When NH3 concentration increased from 0 to 2%, the degradation rate efficiency(DRE) of SF6 increased from 60% to 97.23% under the flow rate of 50ml/min and 94W input power. The energy yield(EY) reached 4.16g/kWh. In addition, we found that increasing the flow rate to 250ml/min, the DRE decreased to 58.71%, but the EY increased to 12.55g/kWh. The main gas by-products are SOF2, SO2F2, SO2, OF2, HF and NF3. When the concentration of initial NH3 increased, the SO2 concentration increased while the concentrations of SOF2, SO2F2, SOF4 decreased. In addition, we found that a pale yellow film formed on the surface of the reactor wall. XPS analysis showed that the solid products were mainly S, NH3HF and NH4HF2. The emission spectra show that NH3 addition can effectively promote the formation of active particles and increase plasma density.The addition of NH3 can convert some of the sulfur and fluorine into solid products and reduce the production of toxic gases.

Rock breaking methods to replace blasting

The method of breaking rock by blasting has a high efficiency and the cost is relatively low, but the associated vibration, flyrock, production of toxic gases since the 1970’s, the Western developed countries began to study the safety of breaking rock. This paper introduces different methods and their progress to safely break rock. Ideally, safe rock breaking would have little vibration, no fly stone, and no toxic gases, which can be widely used in municipal engineering, road excavation, high-risk mining, quarrying and complex environment.

Modeling and simulation of a solar power source at 3kW for a clean energy without pollution

The air pollution was much worse, and it became necessary to replace the fossil energy sources by the renewable energies. The causes are related to reserves that can be exhausted, to pollution and their impacts on the environment. Production of toxic gases from the combustion of coal for the effect of increasing the temperature of the earth. Solar energy is a clean and inexhaustible excellent alternative. We propose a modeling and simulation of a solar system consists of a photovoltaic generator (PVG), a boost chopper, to supply a telecommunications relay station (BTS), According to the load characteristics (I = 60A, V = 48V) DC (3 kW). A stage adaptation composed of this chopper controlled by a PWM controller (Pulse Width Modulation) is used to control the optimal operating point (MPPT) and optimize system performance using Matlab / Simulink.

Avaliação do uso da glicerina proveniente da produção de biodiesel na conservação de peças anatômicas

O uso da glicerina pura é amplamente empregada na conservação de peças anatômicas, a qual é muito eficiente e não tóxica para os manipuladores, porém é extremamente cara e inviável para muitos laboratórios de anatomia. O propósito do estudo foi demonstrar a viabilidade da glicerina semipurificada proveniente da produção do biodiesel na conservação de peças anatômicas. O trabalho utilizou 15 corações e 30 rins de suínos provenientes de frigorífico. A glicerina foi adquirida em usina de biodiesel e apresentava a seguinte composição: Glicerol 80,5%; Umidade 12,8%; NaCl 6,3% e Ácidos Graxos 0,4%. As vísceras foram resfriadas, dissecadas, fixadas, desidratadas e glicerinizadas. Os órgãos foram mensurados, analisados e fotodocumentados antes e após protocolo de preservação. A glicerina semipurificada promoveu discreta diminuição nas dimensões das estruturas anatômicas (massa, altura e largura), todavia não houve diferença estatística. Essa glicerina preservou as características de consistência flexibilidade das peças anatômicas, além de reduzir o custo e a eliminação dos gases tóxicos. O principal alcance deste estudo foi a preservação das características morfológicas e a melhoria do processo ensino-aprendizagem.

Experimental study of burning behaviors of intumescent coatings and nanoparticles applied on flaxboard

This article presents an experimental investigation of ignition and burning behaviors of intumescent coatings and nanoparticles applied on flaxboard using the cone calorimeter, single burning item (SBI) and reduced scale (one-third) ISO room. The effects of intumescent coatings and nanoparticles on time to ignition (TTI), mass loss rate (MLR), heat release rate (HRR), production of toxic gases (carbon monoxide and smoke) were investigated. The performance of intumescent coatings in under-ventilated condition was examined by performing tests in the one-third ISO room with reduced opening sizes. Results in the cone calorimeter and SBI indicated that (1) there is a substantial increase of TTI and decrease of MLR/HRR by intumescent coatings and (2) the addition of nanoparticles results in a further increase of TTI as well as a decrease of MLR/HRR owing to increased stability of the char. Tests in the one-third ISO room showed that although the intumescent coatings reduce the HRR the reduction is much less substantial than that in the cone calorimeter or SBI.