Gaseous Products Of Thermal Decomposition Research Articles

Analysis of the possibility of solid-phase ignition of coal fuel

The article presents the results of theoretical and experimental studies of the ignition process of coal fuel particles in a pelletized state during high-temperature radiation-convective heating in an oxidizing environment. A new, different from the known, “two-temperature” mathematical model of the ignition process of a cylindrical coal pellet under intense heating conditions is presented. During the modeling, a detailed kinetic scheme of the reaction of gaseous products of thermal decomposition of coal with atmospheric oxygen was considered. The mathematical model was tested through a comparative analysis of the theoretical and experimental values of the ignition delay times of coal pellet fuel with experimental data. A wide range of heating conditions that could potentially lead to solid-phase ignition were analyzed. The research results showed that even under conditions of high oxygen content in the original coal, solid-phase ignition of coal pellets does not occur during intense heating. Based on the results of numerical modeling, it was established that the ignition process occurs in the gas phase. The oxygen released during the thermal decomposition of coal is not enough for stable gas-phase or heterogeneous ignition of pyrolysis products in the intrapore space of the fuel pellet. Based on the results of the numerical modeling, it was established that the oxygen released during the thermal decomposition of coal is significantly deficient in the intrapore space. The O2 concentration is not enough for a significant (in terms of heat flow) thermochemical intrapore reaction with gaseous and solid products of thermal decomposition.

The thermal decomposition and combustion of building and finishing materials

The paper investigates specific aspects of the methods for studying the composition of thermal decomposition and combustion products of typical indoor synthetic and natural materials. The purpose of this research is to build up an experimental database with the concentrations of gaseous pyrolysis products during the thermal decomposition of typical materials in compartments. The utilized techniques are gas and liquid chromatography, effusion mass spectrometry, IR spectroscopy, gas analysis equipment (laboratory and industrial gas analyzers). The conducted research compared the promising methods of chemical analysis of gaseous products of thermal decomposition and combustion of synthetic and natural materials that carry a fire load in residential and public spaces. Data on the quantitative and qualitative composition of combustion products of wood, textile and interior design items were obtained. Toxicity indices of combustion product components were calculated. The data presented in the tables and diagrams for the smoke aerosol component yield in the thermal decomposition and combustion of materials can be used to determine gas hazards from combustion products in an area and to solve other applied problems. These findings are fundamental for predicting the toxic substance concentrations, developing fire safety measures and planning the evacuation paths. It is instructive to use these findings as the basis for developing the physical and mathematical models of heat and mass transfer, phase transformations and chemical reactions to determine the patterns of propagation of gaseous components of thermal decomposition and combustion in spaces with different geometries and dimensions.

Thermal decomposition kinetics and mechanism investigation of cumene hydroperoxide under inert gas: A novel experimental method

Organic peroxides, due to temperature manipulation failure and/or manner disturbances, had been probable to lead to the prevalence of runaway phenomena, even fire, and explosion. Cumene hydroperoxide (CHP), is a traditional liquid organic peroxide for industrial purposes and is applied as a free radical initiator for polymerization reactions in the petrochemical industry. Its utilization in the industrial processes had certain potential safety hazards. In this work, linearly ramped thermal decomposition in CHP was performed using differential scanning calorimetry under a nitrogen atmosphere. Kinetic analysis is made using data from the ramped measurements with two integral strategies (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose). The gaseous products of thermal decomposition in CHP are investigated via thermal gravimetric evaluation coupled with Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry. Combined with the experimental results, the possible decomposition path of CHP is discussed. This makes up the gap of unclear decomposition mechanism of CHP in inert atmosphere, and has important reference significance for its industrial production and application.

Nano-starch for food applications obtained by hydrolysis and ultrasonication methods

In the present work, corn (CS) and waxy corn starch (WCS) with different amylose content (determined with the UV–vis spectroscopy) were subjected to acid hydrolysis, ultrasound, and a combination of both, performed at a raised temperature and short period, to obtain nanoparticles (nano-WCS and nano-CS). Scanning transmission electron microscopy (TEM-STEM) proved the effectiveness of the proposed method for nanoparticle synthesis with a size below 5 nm. FTIR spectroscopy and X-ray diffraction (XRD) delivered information on their molecular structure (i.e., reduction in nano-CS crystallinity degree (Xc) arising from higher amylose content and more stable Xc for nano-WCS). Thermogravimetric analysis (TGA) combined with FTIR analysis of gaseous products of thermal decomposition was also performed. The thermal stability decreased in varying degrees for nano-WCS and nano-CS. Less susceptibility of waxy corn starch for modification was proven.Nanoparticles are expected to be effective for functional food, and biomedical applications.

Application of a high-resolution terahertz gas spectroscopy method to compositional analysis of thermal decomposition products of human fluids (urine)

Subject of study. In this study, the compositions of thermal decomposition products of samples of human fluids (urine) of cancer patients obtained before and after chemotherapy were investigated to identify the markers reflecting the influence of platinum-based chemotherapy, including its nephrotoxic influence, on the human body. Method. Molecular absorption spectroscopy, including nonstationary spectroscopy in the terahertz frequency range, is a prospective approach to investigation of multicomponent gas mixtures of different origins, including those of biological origin. The rotational spectrum lines and low-frequency vibrational spectra of molecules are in the terahertz frequency range (0.100–10 THz). When radiation transmitted through a gaseous sample is detected, the absorption lines, which are a unique characteristic of specific substances, are recorded in the spectrum. These absorption lines indicate the presence of the corresponding substances in the investigated multicomponent gas mixture; thus, this technique allows the identification of potential markers for pathologies and diseases as well as markers characterizing the effects of various exposure types on the human body, including the effect of drugs. Main results. A complex of metabolites resulting from the thermal decomposition of the sample was identified. The contents of gaseous thermal decomposition products of urine obtained from sick and conditionally healthy volunteers were compared. In addition, the contents of thermal decomposition products of urine obtained from the cancer patients before and after chemotherapy were compared. Practical significance. The proposed approach is advantageous for the development of a noninvasive investigation method that facilitates the assessment of chemotherapy effects on the human body.

Initiation Parameters of Granulated Synthetic Polymers

Abstract Polymeric materials, which are currently very often used in various industries, are often transported and stored in the form of granules before processing. This method has several advantages, but in most studies the test samples are modified to different shapes and dimensions. This paper is therefore focused on the initiation of selected granular plastics. Samples of five polymeric materials were exposed to an external heat flux from 20 kW.m−2 to 40 kW.m−2. A spark initiator was used to ignite the released gaseous products of thermal decomposition of the polymer sample. FTP (flow-time product) method was applied to the obtained parameter - time to ignition, from which other initiation parameters were determined. The critical heat flux was determined in the range of 5.0 kW.m−2 - 11.8 kW.m−2. Despite the relatively small thickness (4 mm), the samples behaved as thermally thick. During the measurement, thin surface layer melted, and the rest of the polymer remained in its original granulated form. Ignition temperatures were calculated according to the Stefan-Boltzmann’s law between 273 °C - 402 °C.

Adsorption, viscosity and thermal behaviour of nanosized proteins with different internal stability immobilised on the surface of mesoporous activated biocarbon obtained from the horsetail herb precursor

The thermal analysis methods were used for the description of the adsorption behaviour of selected proteins differing in internal stability (ovalbumin (OVA) and lysozyme (LSZ)). These proteins were immobilised on the surface of activated biocarbon obtained from the horsetail herb precursor. The values of the hydrodynamic radius of both biopolymer macromolecules in the solution were determined by the use of the viscosimetry method. This parameter is important for the specification of the possibility of proteins nano-molecules to penetrate the nano-pores of the adsorbent which leads to the increase of biopolymers adsorption. Such behaviour is observed at the pH value which is very close to the pI value of specific biopolymer (the greatest adsorption of proteins on the activated carbon surface occurs- at pH 5 for OVA being 323 mg/g, as well as at pH 11 for LSZ which is 464 mg/g). Under such conditions, the proteins macromolecules assume conformations characterized by the lowest values of hydrodynamic radius, i.e. 2.76 nm for OVA and 1.07 nm for LSZ. The data obtained from the analysis of gaseous products of thermal decomposition of the samples indicated the types of biocarbon surface groups as well as the enabled specification of the protein macromolecules adsorption mechanism.

Influence of wood additives on pyrolysis products composition of mixed fuels based on 3B grade lignite

Experimental analysis of the influence of wood biomass on the composition of pyrolysis products of mixtures based on crushed coal (“Lignite” (3B)) and fine wood (lumber sawing waste) has been performed. Ash residue composition of the main components of fuels and mixtures based on them has been determined experimentally using X-Supreme 8000 element analysis device. Fuel mixture samples were used with a percentage of coal / wood – 100 % / 0 %, 90 % / 10 %, 75 % / 25 %, 50 % / 50 by weight. The experiments have been performed in an inert gas (Argon) environment at temperatures of 400 °C, 600 °C, and 800 °C. It has been established that during pyrolysis of two-component fuels based on 3B grade coal and dispersed wood biomass, there is growth of calcium and aluminum sulfates in the solid products of thermal decomposition of such mixtures (ash) due to a complex of reactions between pyrolysis products of coals and wood when the concentration of the wood component in the mixture changes from 10% to 50 %. Results of experimental studies allow substantiating previously formulated hypothesis about the mechanism of sequestering of sulfur oxides formed during coal pyrolysis as a result of interaction with gaseous products of thermal decomposition of wood and solid products of coal pyrolysis.

Influence of wood biomass on physical and chemical transformations during its joint high-temperature pyrolysis with coals

The article deals with a comparative analysis of the influence of wood biomass on the pyrolysis processes of three grades of coal, namely, “lean” (T), “long-flame” (D), and “lignite” (3B). The composition of the ash residue of the main components of fuels and mixtures based on them was determined experimentally using X-Supreme 8000 element analysis device. Fuel mixture samples were used with a percentage of wood/coal equal to 0/100, 10/90, 25/75, 50/50 wt.%. The experiments were performed in an inert gas (argon) environment within the temperature range from 400 to 800 °C. It was established that during pyrolysis of two-component fuels based on three different coals (T, D, and 3B) in a mixture with dispersed wood biomass (sawmill waste), the effect of the growth of calcium and aluminum sulfates was achieved in the ash of the thermal decomposition products of such mixtures due to a complex of reactions between pyrolysis products of coals and wood where the concentration of the wood component in the mixture changed from 10 to 50%. The results of experimental studies allow substantiating the previously formulated hypothesis about the sequestering mechanism of sulfur oxides formed during the pyrolysis of coals, as a result of the interaction of water vapor with gaseous products of thermal decomposition of wood and solid products of pyrolysis of three coals of different grades.

Mathematical Model of the Motion of Gaseous Thermal Decomposition Products of Composites in a Porous Frame under Strong Heat Flows

The paper describes theoretical issues of the motion of gaseous thermal decomposition products of composite materials in a porous frame structure under the effect of intensive heat flows of different nature. The developed model was verified using benchmark filtration problems and its performance was tested for gas motion using the sample with the porosity that varied in coordinates.

Thermophysical Properties of Ionic Liquids with 1-Butyl-3-methylimidazolium Cation

Thermogravimetric analysis (TGA) is used to study the thermophysical properties of three ionic liquids with 1-butyl-3-methylimidazolium cation. The temperatures and enthalpies of melting and thermal decomposition are determined, and the IR spectra of gaseous products of thermal decomposition are studied. The relationship between the structure of compounds and their thermochemical characteristics is considered.

Determination of toxic products emissions of polymers thermal decomposition using fluidised bed reactor and FTIR analysis

Abstract The paper presents original method of quantitative and qualitative determination of gaseous products of polymers thermal decomposition. It is used to determine the toxic potential of emitted gases, based on their emission E (g/g) by determining the FED dose or toxicological index WLC50M. The method is based on the use of a fluidized bed reactor equipped with a resistive heating jacket, which allows to conduct decomposition of a tested material at a strictly assumed temperature. To identify the types of gaseous compounds and their emission, infrared spectroscopy with Fourier transformation, FTIR was used. The proposed method of measuring the thermal decomposition products concentrations allows mimic the conditions of the fire at different stages of its development. FTIR spectra are recorded every 5 s, which enables identifying toxic gases as a function of burning time, in a precisely determined temperature. Using the library of reference spectra it is possible to determine both inorganic and organic compounds concentrations present in thermal decomposition products of the tested composites. The use of a fluidized bed reactor together with the FTIR analyser operating on-line allows for a much more accurate determination of the emissions of organic and inorganic gaseous products at the assumed temperature, compared to the methods currently used. Silicone rubber composites filled with polyhedral oligomeric silsesquioxanes (POSS) were used for the tests. The effect of POSS, also in a synergistic system with melamine polyphosphate (MPP) on toxicity of gaseous thermal decomposition products of tested composites at temperatures of 500, 600, 700 and 800 °C was determined.

The detection of nitro compounds vapor using sensors based on MIS-structures manufactured by laser deposition

The conditions of the detection of nitro compounds vapors was investigated using the trinitrotoluene as an example. The detection method consists of pyrolysis and later registration by the MIS-sensor of gaseous products of thermal decomposition . It was shown that the offered method allows to achieve the detection limit of 1·10-12 g/cm3 (particles – 1 ng) with respect to the vapors of trinitrotoluene.

Catalytic reforming of gaseous products from pyrolysis of low-density polyethylene over iron-modified ZSM-5 catalysts

Converting plastic wastes into fuels through catalytic cracking is continuously gaining interest from researchers worldwide. In this study, the influence of iron on ZSM-5 (Fe-ZSM-5) catalyst on the reforming of the gaseous products of thermal decomposition of low-density polyethylene (LDPE) was investigated. The acidified ZSM-5 catalysts (0, 0.3, 0.6 and 1 wt% of Fe) were prepared and characterized by XRD, BET, FTIR and SEM techniques. In particular, the effects of temperature (400, 450 and 500 °C) and catalyst loading (0.5, 0.75, 1.0, 1.25 and 1.5 g) on a two-stage (pyrolyser and reformer) decomposition of the LDPE wastes into fuel were studied. The liquid fraction produced was characterized using FTIR and GC/MS techniques. The study showed that the increase in pyrolysis temperature (400–500 °C) increases the volume of non-condensable gas (31–58 wt%) and decreases the volume of the condensates (69–41 wt%) in both the thermal and catalytic pyrolyses. However, the trend was at higher level for the catalytic pyrolysis. The increase in temperature for the thermal pyrolysis had less significant effect on the aromatization content of the liquid condensate compared to the catalytic pyrolysis. The FTIR results show a significant increase in aromatic contents and decrease in the aliphatic of the liquid fraction for the catalytic pyrolysis reforming when compared with thermal pyrolysis. The GC/MS results confirmed the aromatic hydrocarbon compositions, predominantly p-xylene, increased relatively to about 70% in the liquid fraction for the best catalyst (1.25 g of catalyst and 1 wt% iron loading on ZSM-5 at 450 °C).

ON INDUSTRIAL SAFETY IN RECONSTRUCTION AND CONSTRUCTION OF BRIDGES

For the English full text of the article please see the attached PDF-File (English version follows Russian version).ABSTRACT The industrial safety system has evolved on railways for decades. In new economic conditions, many of its basic principles have been preserved, but those factors have emerged that require additional scientific analysis, experimental verification, and modern technological tools. In particular, using the example of construction and maintenance of bridge structures, the situation with labor safety, injuries, and fire hazards at railway transport facilities is studied and assessed. Factorial analysis of labor safety using different criteria is shown. Additionally the results confirm the effect of fire protection on flammability of wood: the effect is manifested in a more intense charring of the surface layer, which creates a barrier to heat the underlying layers, and in a decrease in concentration of combustible gaseous products of thermal decomposition. The results of the experiments allow to determine the directions of improvement of flame retardants, including through the use of additives that maximize the degree of expansion (thermal expansion) of the coatings Keywords: railway, labor safety, bridge works, nomogram of working conditions, injuries, fire protection equipment.

Construction of Bimetallic ZIF-Derived Co-Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin.

This work proposed an idea of recycling in preparing Co-Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO-Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co-Ni LDH nanocomposites with a more environmentally friendly method.

Synthesis, Spectroscopic, and Thermal Investigations of Metal Complexes with Mefenamic Acid

The novel metal complexes with empirical formulae M(mef)2·nH2O (where M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II); mef is the mefenamic ligand) were synthesized and characterized by elemental analysis, molar conductance, FTIR-spectroscopy, and thermal decomposition techniques. All IR spectra revealed absorption bands related to the asymmetric (νas) and symmetric (νs) vibrations of carboxylate group. The Nakamoto criteria clearly indicate that this group is bonded in a bidentate chelate mode. The thermal behavior of complexes was studied by TGA methods under non-isothermal condition in air. Upon heating, all compounds decompose progressively to metal oxides, which are the final products of pyrolysis. Cu(II), Zn(II), and Cd(II) complexes were also characterized by the coupled TG-FTIR technique, which finally proved the path and gaseous products of thermal decomposition. Additionally, the coupled TG-MS system was used to determine the principal volatile products of thermolysis and fragmentation processes of Mn(mef)2·3H2O and Co(mef)2·2H2O.

Thermal and structural studies of sol–gel-derived yttria-doped ZrO2 nanoparticles

This investigation focuses on the role of different atmosphere conditions (air and vacuum) during annealing at different temperatures of sol–gel-derived zirconia ZrO2 (stabilised by yttria in 5 mol%) nanocrystals (5YSZ). Prepared samples were characterised by powder X-ray diffraction (PXRD), simultaneous differential thermal and thermogravimetric analysis, evolved gas analysis coupled with mass spectrometry (EGA-MS), Fourier transform infrared spectroscopy (FT-IR) and micro-Raman spectroscopy. The results of thermal analysis and PXRD analysis show the zirconia crystallisation onset at temperature not lower than 400 °C, while EGA-MS analysis further identified gaseous thermal decomposition products. Average crystallite size of the 5YSZ annealed in air at 400, 600, 700 and 800 °C was calculated to be 10, 15, 22 and 33 nm, respectively. On the other hand, crystallite size remains significantly lower when the heat treatment was conducted in vacuum, i.e. in the range 4–13 nm. Annealing atmosphere affects crystallisation, resulting in lower thermal treatment requirements and enabling controlled crystallite growth. PXRD, FT-IR and micro-Raman spectroscopy showed nanocrystalline 5YSZ samples were successfully stabilised in the tetragonal phase and preserved phase stability over the investigated wide thermal treatment range. Due to the yield of stable particle with small size at lower temperatures, the vacuum-prepared 5YSZ coatings are considered as highly applicable for steel corrosion protection.

Effect of cenospheric fillers on the flammability and fire hazard of silicone rubber composites

This paper presents the results of testing the flammability of silicone rubber composites containing fillers, such as cenospheres, cenospheres covered with iron, attapulgite, wollastonite, aluminum hydroxide and silica. In order to increase the insulating character of boundary layer, boron trioxide was incorporated into the composites of silicone rubber as a ceramization additive. The flammability of the composites was tested with the use of a cone calorimeter. The composition of the gaseous products of thermal decomposition was determined quantitatively and qualitatively in the system with intensive stirring in the fluidal bed, under isothermal conditions at temperatures T = 550, 650 and 750 °C. All the test results show that the fillers used, especially with ceramization additives considerably reduce the fire hazard of silicone rubber composites containing these fillers.

Numerical Analysis of Heat Transfer in Fire-Protective Coatings Deformable upon Heating

Numerical studies of heat transfer in fire-protective coatings deformable (intumescent) upon heating have been conducted. The optimum combination of the computation-scheme parameters providing stability, convergence and satisfactory accuracy of solutions has been determined. An effect of basic characteristics of materials in real range of their change that made it possible to estimate the degree of influence of properties on the fire-protective efficiency of coatings and the level of warm-up (flame resistance) of structures to be protected with them has been studied. The possibility of using developed models and techniques to estimate and provide the required level of fire safety of polymer-based materials (in particular, elastomers and structures and products on their basis) is considered. The results of estimating the mass rate of evolving gaseous thermal-decomposition products that determine, in a considerable extent, the material combustibility have been presented. The numerical analysis results have demonstrated the potentiality of reducing the combustibility of such materials and increasing limits of their fire resistance at the expense of organizing the intumescence of a material upon heating by means of modification of their initial formulations as well as with the aid of an additional layer made of the intumescent coating compatible with an elastomer.