Thermal Decomposition Of Wood Research Articles

THERMAL DECOMPOSITION OF MONO- AND DIETHANOLAMINEBORATE MODIFIED WOOD IN AIR ATMOSPHERE

"For cellulosic materials used in various branches of the economy, the issue of increasing thermal stability is still relevant today. Especially acute is the problem of fire resistance for wood materials used in building structures. In our work, we investigated the effect of mono- and diethanolamine borates on the thermal decomposition of wood in an air atmosphere. It has been previously found that mono- and diethanolaminoborates, when used as surface modifiers, provide 100% biostability to plant raw materials. In this regard, the purpose of the study was to identify the flame retardant effect of the described modifiers. In the course of the study, it was found that the developed compositions, the main components of which are boron-nitrogen compounds, effectively reduce the combustibility of wood materials, suppress smoldering, and reduce the burning rate of wood. Since it is the smoldering of wood after the liquidation of the fire that is the main cause of structural collapse, which prevents evacuation during the fire, the use of the developed compositions for fire protection of wooden structures is extremely appropriate. A regression model of the dependence of activation energy on conversion has been obtained and substantiated on the basis of correlation and regression analysis. The presented semi-logarithmic model can be further applied to predict the dependence of the activation energy value of the thermal decomposition process of modified wood on the degree of conversion."

Experimental Investigations of the Thermal Decomposition of Wood at the Time of the Fire in the Premises of Domestic Buildings

Consideration was given to the issues relating to safety conditions and security arrangements during the thermal decomposition of wood at the time of the fire in the premises of domestic buildings. The data of experimental investigations obtained for the thermal decomposition of wood were given with the measurement data of the concentration of toxic gases (СО, СО2), oxygen (О2), and temperature depending on time and fire spreading conditions in the premises. The studies were carried out by comparing the changes in the temperature of the solid flammable materials with time and the emission intensity of toxic gas (СО, СО2) under the limited oxygen access at the time of the fire. The research data confirm those obtained for the gaseous atmosphere composition in the premises during the thermal decomposition of the solid flammable materials.

Influence of Thermal Decomposition of Wood and Wood-Based Materials on the State of the Atmospheric Air. Emissions of Toxic Compounds and Greenhouse Gases

This paper presents the energy characteristics of wood and wood-based materials in the form of commercially available pellets, furniture board (MDF) and OSB. Toxicometric indices were determined for gaseous destructs arising from thermal decomposition and combustion of the materials studied. The paper proves that combustion conditions are crucial in terms of toxic destructive emissions. It has been shown that the combustion of wood-based materials under controlled conditions can lead to equally low emissions of toxic wastes as the combustion of traditional wood materials. The paper also presents the index of greenhouse gas emission, the so-called CO2 equivalent, for the examined wood and wood-based materials.

Investigation of pyrolysis kinetics and gaseous compounds emitted during charcoal production from woods commonly used in the Eastern Mediterranean

AbstractAir pollution caused by the traditional charcoal production industry is an environmental problem for developing countries. Avocado (Persea americana) and Lemon (Citrus limon) trees that are commonly used in the charcoal industry in the Eastern Mediterranean were chosen as representatives of charcoal raw material in a wood pyrolysis kinetic study that was conducted using a thermogravimetric analyzer (TGA). The weight loss was measured in a nitrogen atmosphere with a heating rate of 10 °C.min−1 at a temperature range from 30 °C to 700 °C. Four main stages, denoted as dehydration, initial decomposition and both active and final decomposition, were registered in the wood thermal decomposition. The main gases produced were identified in the active decomposition stage for lemonwood and avocado wood, respectively, in the temperature range of 255 to 355 °C and 246 to 340 °C. The released gases in the biomass pyrolysis were measured on‐line using Fourier transform infrared (FTIR) spectroscopy. Main gas products of avocado and lemonwood pyrolysis were similar and included CO2, CO, H2O, CH4, and several organic compounds including methanol, formic acid, acetic acid, and furan. Charcoal production thermogravimetric analysis validated that the wood biomass thermal decomposition process has four stages: (1) water evaporation; (2) initial decomposition; (3) active decomposition, and (4) final decomposition. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Deposition of halogen-free flame retardant and water-repellent coatings on firwood surfaces using the new version of DBD

In this study, a rapid, cost-effective, and environmentally-friendly approach was developed for the production of high-performance thin films to reduce the flammability of firwood as well as controlling its wettability. In this regard, a hydrophobic and flame-resistant organic thin coating was prepared through halogen-free plasma polymerization using a novel version of dielectric barrier discharge (DBD) apparatus optimized at atmospheric pressure. The home-made device does not require expensive vacuum instruments and operates in open-air using an organosilicon precursor (hexamethyldisiloxane (HMDSO)) as a liquid monomer. The morphology, composition, and chemical structure of the deposited polydimethylsiloxane-like (PDMS-like) thin films were comprehensively evaluated through FESEM, AFM, XPS, FTIR, EDX, and DTA-TG. The samples showed remarkable cross-linking. This innovative strategy made it possible to achieve the desired characteristics within a concise treatment time. The modifications include the increase in the static contact angle of super-hydrophilic firwood surfaces to 137.73°, enhancement of the surface roughness from 573 pm to 22.5 nm, and a significant reduction in the maximum rate of wood thermal decomposition from 0.94 to 0.65 mg min−1. Applying a creative and simple approach combining the image processing method with the heater test indicated that plasma modification of the wood surfaces improved their thermal stability without altering their aspect ratio or color surface. Therefore, the plasma-synthesized PHMDSO layers prepared by this device could be a promising candidate for fire retardancy and water repellency applications.

ОПРЕДЕЛЕНИЕ КИНЕТИЧЕСКИХ ПАРАМЕТРОВ ТЕРМОДЕСТРУКЦИИ И ГРУППЫ ОГНЕЗАЩИТНОЙ ЭФФЕКТИВНОСТИ ДРЕВЕСИНЫ СОСНЫ, МОДИФИЦИРОВАННОЙ БОРАЗОТНЫМ АНТИПИРЕНОМ

Wood is a combustible material. To reduce combustibility, wood is modified with functional compounds of phosphorus, boron and nitrogen, inoculation of which changes the chemical composition of the surface layer of wood and its structure. The mechanism of action of flame retardants is related to their influence on the energy and entropy characteristics of the thermodestruction process. Considering that boron nitrogen compounds are effective flame retardants and react with wood components under “mild” conditions, the effect of grafting of a borax modifier on the kinetic parameters of wood thermal decomposition is studied. The kinetic parameters (activation energy and preexponent value) are determined by thermal analysis using TGA curves (integral method). A 50 % aqueous solution of monoethanolamine (N→B) trihydroxyborate is used as a modifier; samples of unmodified pine wood are used as controls. The experimental data obtained indicate that the surface modification of pine wood with boron nitrogen fire retardant provides the material with group II fire protection efficiency (modifier consumption-150g/m2). The flame retardant effect of the boron nitrogen modifier is associated with a lower value of the activation energy of its thermal destruction process. The contribution of the entropy factor in reducing the combustibility of modified wood is less expressed. The use of monoethanolamine (N→B) trihydroxyborate as a wood flame retardant is advisable in an oxidizing atmosphere.

Effect of the Kinetic Model of Pyrolysis on Prognostic Estimates of Ignition Characteristics of Wood Particles

The effect of the kinetic model of the thermal decomposition of wood on the results of prognostic modeling of the ignition of wood particles was analyzed. The results of mathematical modeling were verified by experimental studies of the ignition of wood particles in a high-temperature environment. Comparative analysis of theoretical and experimental ignition delays shows that they are in good agreement. The prognostic potential of three substantially different kinetic models of wood pyrolysis was analyzed. The model of one-step pyrolysis involving the formation of gaseous reaction products adequately describes thermal decomposition during thermal preparation in the whole range of heating conditions (the deviation from the times obtained using the three-step pyrolysis model does not exceed 5%). Numerical simulation results show that accounting for the thermal decomposition reactions of the second and third levels with the formation of intermediate (liquid and solid) pyrolysis products does not have a significant influence on the characteristics and conditions of ignition of wood particles in a high-temperature gas environment.

Kinetic color analysis for assessing the effects of borate and glycerol on thermal modification of wood

The effects of borate and glycerol impregnation of Douglas-fir heartwood prior to open-air oven thermal modification at 160–200 °C for 2–4 h on wood color were measured. These materials were used to analyze the effects of modifying agents on thermal decomposition of wood by color nondestructive assessments. Kinetic analysis using time–temperature superposition and the horizontal shift factor were employed to quantify color changes. Lightness values were significantly affected by heating time and temperature, while red/green and yellow/blue values were significantly affected by pretreatments and thermal modification temperatures. Total color differences tended to increase with heating temperature and time. The calculated values of the apparent activation energy on non-impregnated, borate-impregnated and glycerol-impregnated wood ranged from 94.9 to 126.4 kJ/mol, 46.5 to 74.3 kJ/mol and 54.3 to 79.7 kJ/mol, respectively. The results suggest that borate and glycerol decreased the apparent activation energy of thermal degradation reactions and could function as a catalyst to accelerate thermal modification. Time–temperature superposition color kinetic analysis could be used to assess the effects of modifying agents on thermal decomposition.

Термічний аналіз деревини та кори робінії несправжньоакації в деревостанах Північного степу України

За допомогою методів термогравіметрії – термогравіметричної кривої (ТГ), диференціальної термогравіметричної кривої (ДТГ), або кривої інтенсивності зміни маси досліджуваного зразка, досліджено термічну деструкцію деревини і кори головної лісотвірної породи штучних лісових насаджень Північного Степу України – робінії несправжньоакації (Robinia pseudoacacia L.). Термічний аналіз зразків деревини і кори здійснено в окиснювальній (повітря) атмосфері. Встановлено стадії термічного розкладання деревинної речовини і кори в умовах програмованого нагріву до 600 оС зі швидкістю 10 оС/хв (ТГ/ДТГ/ДТА), їх температурні інтервали, втрату маси, інтенсивність втрати маси та теплові ефекти. На основі аналізу величин енергії активації на окремих стадіях термічного розкладання, залежності енергії активації від ступеня конверсії деревини і кори, а також із порівняння втрати маси на відповідних стадіях термодеструкції, теплових ефектів, залишкової маси і інших параметрів ТГ/ДТГ, охарактеризовано деревину і кору робінії. Деревина робінії характеризується значнішою термостабільністю, ніж кора. Запропоновано математичні моделі для оцінювання залежності втрати маси від температури деструкції складників надземної фітомаси (кори, деревини) досліджуваного деревного виду.

Influence of modifiers on coked foam structure and properties formed with thermal decomposition of wood

Wood is a material that forms a surface layer of coke when burning. Properties of the coke layer significantly impact the fire resistance of structures due to the change of the structure working section reduction rate. This paper discusses the research of how the wood surface layer modifiers influence the structure and properties of the coke layer formed with thermal decomposition of wood. As modifiers have been used phosphorus flame-retardants. To evaluate how the modifiers influence the coke layer formation process, the source and modified samples of pine have been analyzed before and after thermal decomposition using the element analysis, electron microscopy, and adsorption. Thermal analysis has been accomplished using the thermogravimetry (TG), differential thermogravimetry (DTG), and differential scanning calorimetry. To evaluate the fire protection efficiency of the modified wood, fire tests have been accomplished. Such tests were tests to determine the magnitude of weight loss during combustion, flame spread index and the coefficient of smoke-ability. Based on the acquired data, it was identified that when the modifiers are used, and these modifiers enter into efficient superficial chemical reaction with wood under mild conditions, the thermal decomposition occurred under mild conditions - the first stage of thermal decomposition transits to the lower temperatures zone. This reduces the thermal effect of thermal decomposition reaction. There is a decrease in weight loss during thermal decomposition. This results in formation of the strong and structured, thermally stable surface, which is less adsorption ability, specific surface area and porosity reduction. This explains high rate of fire protection and low smoke-generating capacities.

Effect of autogenous pressure on volatile pyrolysis products

The thermal decomposition of wood, conducted in the absence of oxygen, includes so-called primary and secondary reactions, where secondary reactions are regarded as those involving previously formed decomposition products. This study uses a pyrolysis–gas chromatograph-mass spectrometer, Py-GC/MS, to investigate the degree to which secondary reactions affect the composition of the volatile pyrolysis gases. Samples were Monterey Pine (Pinus radiata) and were held in either open crucibles or sealed capsules. For specified heating profiles ranging from 240 to 700 °C, volatiles escaped soon after they evolved in the open crucibles but in the sealed capsules they were retained at high pressures for long residence times. Differences were observed over the entire range of treatment temperatures, which suggests that secondary reactions occur concurrently to primary reactions and implies that they are more dependent on vapour-phase concentration than on temperature. In comparison to the open crucible experiments, the sealed capsule experiments produced more low molecular weight pyrolysis products and more long chain alkanes, alkenes and methyl ketones, but at the expense of extractives, carbohydrate and lignin derivatives. The sealed capsules also had less oxygen in the condensable fraction, characterised by the presence of alkyl substituted compounds. Instead the open crucible experiments contained methoxyl substituted compounds. These differences are all characteristic of secondary reactions. This study shows that controlling the extent of secondary reactions is an invaluable tool for optimising pyrolysis.

DEVELOPMENT OF THE DESIGN SCHEME OF THE COMBUSTION CHAMBER FOR BURNING OF WOOD CHIPS THE OLD SLEEPERS

А calculation scheme for the utilization of chips of old wooden sleepers in a vortex furnace is proposed. The vortex furnace provides two zones of reaction of a combustible substance with air: the primary zone is the gasification of old sleepers and the afterburning of the solid residue with a lack of air oxygen, the secondary zone is the burning of the gas phase. The initial data for the thermodynamic calculation is given. The results of the equilibrium calculation of the thermal decomposition of wood on the grate and the combustion of gasification products are presented for different values of the excess air factor, as well as some experimental data. A comparison of the calculation results with the experimental data is carried out.

ВЛИЯНИЕ МОДИФИКАТОРОВ НА ХАРАКТЕРИСТИКИ ПЕНОКОКСА, ОБРАЗУЮЩЕГОСЯ ПРИ ТЕРМИЧЕСКОМ РАЗЛОЖЕНИИ ДРЕВЕСИНЫ

Introduction. Currently, wood-based construction materials are in high demand in the field of construction around the globe. The study of the original wood composite in order to improve its characteristics through various methods is scientific pre-requisity for such development. When wood burns, it forms a surface coke layer, which can differ in mechanical and thermal stability. These parameters produce a significant effect on the fire resistance rating of building structures due to a change in the reduction rate of the structure useful cross section. Materials and methods. The studies carried out during the work are related to the evaluation of the characteristics of coke layer formed during thermal decomposition of wood. Thermal analysis methods, the scanning electron microscopy method and the water adsorption method were used. The original sapwood of pine, as well as the wood modified with effective fire-retardant agents were used in the course of work. Results. Based on conducted experiments process graphic dependences of thermal decomposition have been obtained, as well as images, obtained by an electronic microscope. In addition, the dependence of adsorptive capacity of wood after thermal decomposition has been obtained. Discussions. As a result of the study, it was found that with the use of modifiers based on organophosphorous compounds, entering into effective reaction with wood, structuring of the surface layer occurs after thermal decomposition while reducing the size of specific surface area of wood. Conclusions. Based on the analysis of experimental data, we can conclude that because of the use of efficient wood surface layer modifiers, thermal decomposition takes place under “mild” conditions that is the shift of the first stage of thermal decomposition to the area of lower temperatures with non-severe exothermic effects. The loss of weight of samples during combustion is significantly reduced. This causes high fire-retardant efficiency and low smoke-generating capacity.

Теплота сгорания облагороженного древесного топлива

Torrefication is a process of low-temperature pyrolysis of wood, used to improve the properties of wood fuel. Torrefied fuel has several advantages compared to the original. Thermal degradation causes changes in mass and composition of wood with increase in carbon percentage, which leads to an increase of combustion value Q. Thermal destruction can be viewed as a multistage process. The degree of decomposition of the material depends on temperature, time of exposure to heat and kinetic parameters of each stage of the process. The article presents the results of experimental studies of combustion value of torrefied woody biomass and its dependence on the degree of thermal decomposition. For experimental studies experimental setup was designed and manufactured. Experimental checking of the installation was carried out. The test showed that accuracy of determining combustion value is not more than 2 %. For experimental studies of the dependence of combustion value on the degree of thermal degradation, samples of wood were prepared in its unsaturated decomposition. Heat treatment of samples was carried out in inert gas environment of helium. Values of heat combustion of wood fuel with varying degrees of thermal destruction are obtained. Model of the dependence of calorific value from relative mass of wood fuel ω is proposed. The mathematical model allowing to determine the relative mass of wood as a function of temperature and time is represented. Dependence of combustion value on degree of thermal decomposition of wood is obtained in explicit form.

THE STUDY OF THERMAL IMPACT ON THE TRANSFORMATION OF ASPEN WOOD AND BARK

Thermal gravimetry analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM), FT-IR spectroscopy, and thermal adsorption of nitrogen (BET) methods were used to study the thermal destruction of woody biomass of aspen (bark and wood) in argon and air in the temperature range from 25 to 800 °C. The composition and properties of the products obtained as a result of thermal decomposition of the initial wood biopolymers are characterized. It is established that the main range of thermal decomposition of wood in an inert medium included an interval from 227 to 500 °C, and aspen bark covered a temperature range from 180 to 600 °C. In the air atmosphere, the temperature zone of thermal decomposition narrows, the loss of mass of matter is observed in two temperature intervals of preferential decomposition of the substance with a shift toward a decrease in the maximum rate of decomposition for the bark (~40 °C), and for wood – 34,6 °C.

Применение огнезащитных пропиточных композиций для снижения пожарной опасности деревянных конструкций с различными сроками эксплуатации

The article presents the results of a study on the development of fire-retardant impregnating compositions for reducing fire hazard of protecting wooden structures (WS) of different lifespan. Basic scientific notion in the present work, connected with the possibility of influence of fire retardants (fire retardants) on the formation of coal residue, its structure and properties within the first minutes of fire exposure with the aim of reducing fire hazard properties of WS is not only at the initial stage, but maintaining the thermal stability and the cohesiveness of WS in conditions of prolonged fire. The results of the study using thermal analysis showed that during the development and application of fire retardants for wood long life the defining characteristics are speed and the heat of oxidation of the coal residue. This is due to the specific behavior of the long-term operation wood under fire conditions. Designed compounds effectively reduce these characteristics. So the heat of coal oxidation residue for long - term operation wood (81 years) with the composition containing dimetilfosfit and modifying additives, is reduced to 1.27 times in comparison with coal modern wood. It is shown that with increasing period of operation of WS up to 200 years, the effectiveness of this flame retardant in the reduction of the characteristics of thermal analysis is preserved. It is determined that the flame retardants can have an impact on the formation of coal residue, its structure and properties and also to reduce heat effect (20-80 °C) throughout the experiment and intensity of WS charring (1.07-1.29 times) in the conditions of fire tests according to GOST 30403-2012, despite a small amount of flame retardant in the surface layer of the structure. The effectiveness of flame retardants is also evident in the reduction of ignition time by WS in standard temperature conditions of a fire. Fire-retardant treatment of WS compounds allows to increase the resistance of structures to flammability to 1.4-1.8 times. Mechanism of fire retardant effect is evident in change of main phases of wood thermal decomposition as well as in impact on the structure and properties of formed coal layer and it’s oxidizing capacity and heat effect in term of WS fire testing. This is extremely important because these characteristics are closely interrelated with the extent of thermal damage, charring, and the intensity of heat dissipation WS, which determine ultimately their fire danger and fire resistance.

Thermal decomposition of wood: Kinetics and degradation mechanisms

The influence of wood components and cellulose crystallinity on the kinetic degradation of different wood species has been investigated using thermogravimetry. Four wood species were studied: Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP). Thermogravimetric results showed that higher extractive contents in the wood accelerate the degradation process and promote an increase in the conversion values at low temperatures. Alternatively, the results indicated that the cellulose crystallinity inhibits wood degradation; organized cellulose regions slow the degradation process because the well-packed cellulose chains impede heat diffusion, which improves the wood’s thermal stability. The wood degradation mechanism occurs by diffusion processes when the conversion values are below 0.4. When the conversion values are above 0.5, the degradation is a result of random nucleation with one nucleus in each particle.

Innovative processing of lotus-type porous magnesium through thermal decomposition of wood

The aim of this study was to fabricate lotus-type porous magnesium with aligned cylindrical pores through thermal decomposition of wood by unidirectional solidification in the atmospheric pressure. Pores with cylindrical shape, whose growth direction was parallel to the solidification direction, were observed in the samples. The dependence of the pore structure (porosity and pore size) as well as mechanical properties on the wood amount was investigated. It was found that by increasing the wood content, porosity increased while average pore size was not affected. The compressive yield strengths of fabricated porous samples were slightly lower in comparison to the theoretical values mainly due to the presence of short pores with a small aspect ratio as well as existence of wood decomposition products along grain boundaries.

Chemical improvement of surfaces. Part 2: Permanent hydrophobization of wood by covalently bonded fluoroorganyl substituents

Abstract A recently developed esterification method in our laboratory was applied to permanent hydrophobization of wood surfaces. Specifically, the covalent attachment of fluoroorganyl substituents to wood hydroxy groups via benzotriazolyl-activated, substituted benzoic acids was in focus. Weight percent gain values from 10% to 28% were obtained on Scots pine (Pinus sylvestris) sapwood veneer chips. It proved feasible to lower the temperature for wood modification from 150°C to 120°C, or even to 70°C so that thermal decomposition of wood during modification can be neglected. The modified chips were analyzed by attenuated total reflection – infrared and X-ray photoelectron spectroscopy. Covalent attachment of the fluorobenzoic acids led to a very high, permanent hydrophobicity of the wood surface, documented by outstanding contact angles of up to 143°.

Thermal Decomposition of Wood Treated with K<sub>2</sub>CO<sub>3</sub> and Melamine Modified Phenolic Resin by Thermogravimetry–Mass Spectrometry

The flame retardancy of the wood samples treated with K2CO3, melamine modified phenolic resin (MMPR), and their mixture of K2CO3/MMPR was studied with the limiting oxygen index (LOI) method. The thermal degradation process and the composition of the products in gas phase were determined by the thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the K2CO3 accelerates the dehydration reaction of wood and promote the formation of more H2O, CO2, and char residue, while MMPR can act as the thermal barrier during the combustion of the samples. When the wood sample treated with K2CO3/MMPR, there are the catalysis of K2CO3 and the adiabatic effect of MMPR make the samples have better flame retardancy.