Charring Rate Research Articles

Charring depth and charring rate of cross-laminated bamboo slabs exposed to a one-sided standard fire

In recent years, inspired by cross-laminated timber (CLT), cross-laminated bamboo (CLB) has been proposed to promote the development of high-rise bamboo structures. To better understand the charring properties of CLB, three groups of CLB slabs treated with different fire-resistant methods, including no treatment, painting fire-retardant coatings and impregnating flame retardants, were exposed to fire on one side with furnace temperatures following the requirements of ISO 834-1. The test results indicated that under the same fire-exposure duration, the charring degree of the CLB slabs treated with different fire-resistant methods showed a decreasing order as follows: no fire-resistant treatment > impregnating a monobasic ammonium phosphate (MAP) solution > painting fire-retardant coatings. A modified theoretical calculation method (time-location model) was proposed to calculate the charring depth considering the difference in the average charring rates between layers in which the grain direction is parallel or perpendicular to the major longitudinal direction. Furthermore, the temperature versus fire-exposure duration curves were divided into four stages: a slow rising stage, a platform stage, a rapid rising stage and a furnace temperature stage. A modified temperature profile model was proposed and was applicable for the temperature prediction of CLB slabs.

Timber encasement of steel structures as an alternative fire insulation

AbstractThis paper presents the results of an investigation on the thermal behaviour of fire‐exposed steel profiles embedded in timber elements.Several tests were performed on small unloaded specimens in a small furnace. The different specimens were made of bare steel profiles, timber elements or steel‐timber hybrid members. Different welded I or T steel sections and wood species were used. The specimens were set horizontally (3‐side exposure) or vertically (4‐side exposure) in the furnace and heated using a couple of burners. The temperatures of the steel profiles were measured by welded K thermocouples.The results from this experimental campaign, in terms of temperature of the furnace and of the specimens, density and moisture content of timber, were then used to calibrate a heat transfer model under Ansys finite element code. This 2D numerical model is mainly based on the behaviour laws of structural steel and timber from Eurocodes 3 and 5 respectively. Regarding the specific heat of timber, several relationships were applied. A comparative analysis of experimental and numerical results confirms the fire insulation brought to steel by timber. It also highlights the ability of the model to simulate the thermal behaviour of both steel and timber, in terms of heating and charring rates.

The Effect of Heat Flux to the Fire-Technical and Chemical Properties of Spruce Wood (Picea abies L.).

The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW·m−2. The fire-technical properties, such as the mass burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32%·s−1 was reached at the heat flux of 30 kW·m−2. The charring rate ranged from 1.004 mm·min−1 (15 kW·m−2) to 2.016 mm·min−1 (30 kW·m−2). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW·m−2. The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.

Review of large-scale fire tests on cross-laminated timber

Concerns about the environmental impact of building construction is leading to timber being more commonly used. However, it often faces scepticism regarding its safety in the event of fire. This article provides a point of reference on the fire performance of cross-laminated timber through a review of large-scale tests. Although adequately protecting CLT can make its contribution to fire insignificant, some of the internal surface of an enclosure can be exposed whilst still achieving adequate fire performance. Natural fire tests show that the charring rate and zero-strength layer thickness are higher than commonly used in guidance documents. The type of adhesive used to bond lamellae influences performance where delamination can lead to secondary flashovers, particularly in smaller enclosures. Structural elements can potentially collapse without self-extinction and/or suppression intervention. Tests to date have focussed on a residential context and knowledge gaps remain regarding larger enclosures, such as office-type buildings.

Comparative study on fire resistance and zero strength layer thickness of CLT floor under natural fire and standard fire

A study of the fire resistance of cross-laminated timber (CLT) flooring material exposed to different fire conditions (ISO 834 standard fire and natural fire) is described, along with the value of the zero strength layer (ZSL) thickness. Experimental studies of the flexural performance of four groups of CLT floor at ambient temperature and the fire resistance of six groups of CLT floor under the action of fire were conducted. The influence of different laminate compositions (three-ply and five-ply) and different load ratios (10%, 20%, 30%) on the internal temperature field distribution, fire resistance and carbonization of the six groups of CLT floors were compared and analyzed. Subsequently, Abaqus software was used to establish a finite element temperature field heat transfer model of the shedding of the charred layer to analyze the fire resistance of the CLT floor, and to compare the key parameters in the test (charring rate, depth of charring, and shedding of the charred layer), to verify the validity of the model. Finally, the effective residual section method was used to develop a theoretical calculation model for determining the thickness of the ZSL of the CLT floor throughout the fire process. The theoretical calculated charred depth at different times during the fire resistance tests are compared and analyzed to verify the accuracy of the theoretical method.

Self-assembled bio-based coatings for flame-retardant and antibacterial polyester–cotton fabrics

There are many defects in the post finishing flame-retardant modification of polyester–cotton (CT) fabric, leading to shortcomings such as single function and low flame-retardant efficiency, which still need to be solved urgently. Herein, a bio-based flame-retardant and antibacterial coating consisting of phytic acid and DL-arginine was deposited on CT fabrics using layer-by-layer assembly to obtain a flame-retardant and antibacterial CT fabric. Fourier transform infrared spectroscopy confirmed that the assembled coating was successful deposited on the CT fabric. The thermogravimetric analysis revealed that the number of bilayers had no significant effect on the degradation temperature of the coated CT fabric; however, it significantly improved the charring effect of the sample, wherein the char rate of the CT fabric coated with 20 bilayers increased from 0.11 to 8.67 wt% compared with uncoated CT fabric at 700°C. In addition, the limiting oxygen index of the CT fabric coated with 20 bilayers increased to 32.0 ± 0.3%. Furthermore, the vertical results revealed that the CT fabric coated with five bilayers attained the UL-94 V-1 grade. The heat release rate (HRR) and the total heat release (THR) of the coated CT fabric were significantly decreased compared to those of the uncoated CT fabric. In particular, the HRR and THR of the CT fabric coated with five bilayers reduced by 28.97% and 30.49%, respectively. Furthermore, the coated CT fabric exhibited an obvious antibacterial effect on Staphylococcus aureus, and the inhibitory ring increased from 0 to 4.0 mm with an increase in bilayers to 20. This study describes a facile method of flame-retardant and antibacterial modification of CT fabric using biological materials.

Evaluation of the CO2 gasification of residual char under a regeneration atmosphere via calcium‒based chemical looping gasification

Calcium‒based chemical looping gasification plays a vital role in the utilization of carbon‒based fuels. In this study, the effects of various parameters in the regeneration of CO2 gasification of residual char were studied. Since the CO2 gasification of residual char was an endothermic reaction, the reaction rate increased with temperature. The maximum reaction rate appeared at a CO2 partial pressure of 80%. The carbon conversion rate of residual char increased upon increasing the CO2 capture capacity of sorbent. The CO2 gasification of residual char complied with the shrinking core model instead of the volumetric reaction model, and the municipal solid waste (MSW) char after CO2 gasification was cylindrical shape. The apparent activation energy decreased after adding a sorbent, showing that the CO2 gasification of residual char was improved by adding a sorbent. These results provide an approach to enhance the CO2 utilization in regenerator, outlets and help reduce the oxygen demand and heat losses.

Investigation of the combustion behaviors and kinetic modelling of municipal solid waste char under isothermal conditions using a micro-fluidized bed

Approaches to the accurate measurement of combustion kinetics are essential for the numerical simulation, reactor design and process optimization of MSW-fired systems. The micro-fluidized bed reaction analyzer (MFBRA), which consisted of a micro-fluidized bed reactor and electrical control devices, was applied in the investigation of the combustion behaviors and kinetic modelling of noodles char (NC) and bamboo chopsticks char (BC). And the kinetics obtained from the thermogravimetric analyzer (TGA) were compared. The results indicated that the TGA might not fully meet the requirement for kinetic study of MSW char combustion due to the temperature deviation and prolonged testing time. Besides, the lower activation energy suggested insufficient heat and mass transfer in TGA. The combustion rate was strongly temperature dependent in MFBRA and BC exhibited around two times higher reactivity than NC. The combustion behavior would transfer from chemically controlled regime into pore diffusion controlled regime at 973 K for NC, and 923 K for BC. Volumetric reaction model (VRM) would overestimate the combustion rate due to the active surface variation during combustion. In contrast, random pore model (RPM) could well predict the conversion process for both samples at high temperatures, which might correspond to the pore enlargement and coalescence. The obtained activation energies of NC and BC combustion in the chemically controlled regime were 56.12 and 48.73 kJ/mol, respectively. Therefore, elevating the oxygen partial pressure and increasing the feeding rate were feasible ways for acquiring fast combustion rate of MSW char as a result of good reactivity in industrial applications.

Effect of preparation conditions on the performance of K-decorated Fe2O3/Al2O3 oxygen carrier (OC) in chemical looping conversion of coal process with deep OC reduction

Chemical looping conversion of coal (CLCC), an innovative technology, is an efficient and clean way for the utilization of coal. Oxygen carrier (OC) reduction by the coal is the rate-limiting process for the CLCC with deep OC reduction. K-decorated Fe2O3/Al2O3 OC, found to be a promising OC, can increase the reaction rate of OC and char. Unfortunately, due to the complexity of the OC the preparation conditions on the performance of this composite OC were not clear. In this study, the effect of Al2O3 content and calcination temperature on the activity and stability of Fe-based OC were investigated by thermogravimetric analysis (TGA), H2 temperature-programmed reduction (TPR), N2 adsorption analyzer, X-ray diffraction (XRD) and scanning electron microscope (SEM). The impact of K2CO3 loadings on the reactivity and stability of OC was also studied in a fix-bed reactor. In addition, optimal preparation conditions were screened out. The results showed that Al2O3 could increase the specific surface area of OC and anti-sintering ability. However, the Al2O3 had an adverse impact on the mechanical strength and reactivity of OC. The increase of calcination temperature of OC could increase the mechanical strength but decrease the reactivity of OC. The loading of K2CO3 could significantly improve the reactivity of OC, and K2CO3 was favorable for the redox stability of OC. The optimal preparation conditions of the composite OC are as follows: the addition amount of Al2O3 was 30%, the addition amount of K2CO3 was 5%, and the calcination temperature of OC was 1030 °C.

Experimental and numerical investigation of the response of GLT beams exposed to fire

This paper presents a combined experimental and numerical investigation of the behavior of glued laminated timber beams when exposed to fire. The influence on the time variation of charring rates based on the evolution of temperature profiles is examined for different fire scenarios and durations as well as different beam’s cross-section sizes. Predictions of charring depths provided by numerical simulations of heat transfer and simplified charring rate models are compared. In the absence of a mass transport representation, a Bayesian inference is introduced to identify the temperature-dependent material parameters for the conventional heat transfer model. A similar approach is adopted when adjusting the selected parameters of the charring rate models to account for variations in actual fire scenarios, which potentially depart from standard fire exposure. When compared to experimental results, both approaches confirmed their predictive capabilities, particularly in the stage of initial design. Since presented in the framework of Bayesian statistics, they open the door to fully stochastic analysis with an emphasis on the load bearing capacity of the studied beams.

Facile preparation of BP-MoS2/GO composite films with excellent flame retardancy and ultrasensitive response for smart fire alarm

Design and exploitation of smart fire-warning devices with ultrasensitive response capability are always an urgent need for effective fire protection. Herein, a nano-filler (BP-MoS2) is prepared by ball milling black phosphorene and molybdenum disulfide and added into the graphene oxide (GO) film to fabricate a multifunctional film with high fire resistance and rapid response ability. When the addition of BP-MoS2 is 20.0 wt%, the GO/BP-MoS2 20.0 shows an excellent flame retardancy. The residual char rate is improved from 46.60% to 66.65%, and its peak of heat release rate (pHRR) value has reduced from 599.92 W g−1 to 274.00 W g−1, resulting in a 54.33% decrease, which is attributed to the ultra-fast catalytic char formation and synergistic flame retardancy of BP and MoS2. Meanwhile, the composite film can still maintain the original shape within 15 s of ignition. More interestingly, when encountering a flame attack, it reveals an ultra-fast fire warning response (about 1 s), which is attributed to the fast carbonization after contacting with flame. Such approach offers a novel perspective for the preparation of intelligent fire alarm devices with ultra-fast response ability.

Removal of impurities from waste tire pyrolysis char using the molten salt thermal treatment

Thermo-chemical recycling of waste tire to generate pyrolytic char as alternative carbon black is a promising route for waste disposal and environmental sustainability. However, impurities in waste tire (like Zn, Si, Ca and S) are probably enriched in the pyrolytic char, and removal of those impurities is of great importance for char recycling. To avoid generating large amount of waste acids and polluted gases in the traditional impurities removing process, molten salt (Na2CO3-NaOH) thermal treatment was creatively proposed in the current work. The influence of operational temperatures (in the range of 350 to 450 °C) was investigated in relation to the efficiency of impurity removal. Results show that the removal efficiency of impurity components was firstly increased but then weakened by increasing treating temperature from 350 to 450 °C, while the highest removal rate was obtained at 400 °C. Generally, the current system could effectively remove more than 80% of ash and 70% of sulfur at 400 °C, with the recovery rate of char between 71% and 83%. Specifically, calcium carbonate/sulfate was removed from the char due to its good solubility in the molten salts. In addition, molten salts showed good activity to convert char contained inorganic sulfides and ·SH radicals into salts-soluble Na2S. Similarly, silicon and zinc were tended to be transformed into soluble silicate and zincate, which had higher solubility in the used molten salt. In addition, the agglomerated char particles were separated into smaller and more uniform size during molten salt thermal treatment.

Reaction process and characteristics for coal char gasification under changed CO2/H2O atmosphere in various reaction stages

During the operation of industrial gasifier, the concentrations of CO2 and H2O in gasification media vary with the change of stages, causing the gasification process being affected accordingly. Therefore, dividing the gasification process into different stages to study the effect of multi-stage switching atmosphere is significant. The conversion rate, reaction characteristics and reaction process for the gasification of Xiaolongtan (XLT) coal char in different atmospheres (CO2/H2O/N2) switching in the early, middle and late reaction stages were investigated using thermo-gravimetric analysis (TGA). The results indicated that the average reaction rate of coal char with H2O was approximately 3 times that of CO2. Increasing H2O concentration improved the reaction and conversion rate of coal char, which was the most obvious in the early stage. With the H2O concentration increasing from 0 to 95%, the increment of conversion rate in the early, middle, and late stages were 7.13%, 4.40%, and 3.92%, respectively. Thus, considering the problem of H2O corrosion in practical production, the H2O concentration could be appropriately increased in the early stage to improve efficiency. Compared with the random pore model, the shrinking core model fitted the gasification process of coal char better in a highly reactive 95% H2O/5% N2 atmosphere.

On-board zero-discharge water treatment unit for well-boats: Arctic char as a case study

ABSTRACT An onboard zero-discharge water treatment process, aimed at the well-boat industry, is described and demonstrated as an alternative to current techniques. Two live-fish holding trials were carried out with Arctic char for 8 days (84 kg/m3) and 6 days (154 kg/m3). The trials were conducted in a zero-discharge pilot system with a unique water treatment unit relying on electrochemical water-treatment for oxidizing ammonia into N2(g), disinfecting the water, removing fine particles/organic matter and chlorine-species via activated-carbon filtration. No professional skills are required to operate the system. The TAN excretion rate of adult Arctic char under starvation at 5°C amounted to ~22 mgN/(kg·d). Sensory evaluation showed that Arctic char could be successfully held in a system based on the suggested technology without adverse effects relating to mortality and product quality. The costs of operating the system were assessed at 0.30 USD per one ton of standing stock per 24-h journey.

Reaction Kinetics of Palm Char and Coke with Iron Oxides in EAF Steelmaking Slag

The reaction kinetics, activation energy, and reduction rates of different carbon reductant properties with electric arc furnace (EAF) slag determine the effectiveness of carbon in EAF steelmaking. This article investigates the interaction between slag and carbonaceous materials derived from palm char and coke. Palm shells were converted into palm char using chemical activation method (phosphorus acid, H3PO4) and pyrolyzed at 450 °C for 2 h in a horizontal tube furnace. Then, all the carbonaceous materials were mixed with iron oxide from slag with mass ratio of 1:3.73. The reduction reaction was carried out in a horizontal tube furnace at different temperature ranges of 1250–1550 °C under argon gas to understand the reaction kinetics, activation energies, and reduction rates of iron oxide from EAF slag with palm char and coke. All iron oxides in EAF slag were completely reduced into metallic iron at 1550 °C for both reductants. The phase and quantity of reduced iron were confirmed by Rietveld refinement method using X-ray diffraction (XRD) pattern and energy-dispersive X-ray spectroscopy (EDX). Palm char/slag has lower activation energy value, E (38.52 kJ/mol), than coke/slag (47.75 kJ/mol). The reaction rate of palm char was found faster (4.99 × 10–5 mol/cm2 s) than coke due to larger specific surface area, higher pore volume, amorphous carbon structure, and higher fixed carbon with high volatile content leading to lower activation energy, thus accelerating the iron oxide reduction rates. This finding forms the basic understanding of the reaction between EAF slag and carbonaceous materials for future research on the production of palm char as a feasible carbon reductant in EAF steelmaking.

Studying and evaluating catalytic pyrolysis of polypropylene

Renewable energy and alternative fuel from different conventional resources such as biomass, plastic waste, and recyclable polymers are impertinent environmental issues worldwide. Furthermore, to replace fossil fuel and reduce greenhouse gas emissions that have a negative impact on climate change. This article exhibits the effect of metal oxide composite/clay in the thermal decomposition of Polypropylene. That hetrocatalyst composed nano-clay thin layer loaded with MnO2 –NPs works on cracking of polypropylene under different reaction conditions like heating temperature, rate of reaction, reaction time, and composite loading ratio. Various techniques such as GC and TEM were used to characterize pyrolysis gases and char, in addition to scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Thermo-gravimetric analyzer (TGA), and X-ray diffraction (XRD) were used for composite characterize. High gas yield and char rate conversion were obtained using synthesize composite.

Thermal Model for Timber Fire Exposure with Moving Boundary

Fire exposure of timber leads to charring, surface cracking and timber burnout, shifting the external thermal load deeper into the timber domain. This phenomenon plays its role mainly in situations of longer fire exposure. The majority of current approaches and models assume initial geometry during the whole analysis, leading generally to the overestimation of the insulation effect of the charred layer and to a limited burnout. This paper presents a heat transport model which is supplemented with a moving boundary condition, a criterion for the finite element deactivation and the internal heat source. Comparison with experiments using a constant radiative load testifies that the moving boundary condition becomes important after approximately 10 min of fire exposure and rather leads to a constant charring rate observed in several experiments.

Study on the steam gasification reaction of biomass char under the synergistic effect of Ca‐Fe : Analysis of kinetic characteristics

Biomass char gasification is an important part of biomass conversion technology; the addition of additives can effectively change the gasification reaction rate of char. The kinetic characteristics of steam gasification reaction of biomass char particles were explored by adding CaO, Fe2O3, and Ca-Fe mixed catalyst to biomass, and the apparent activation energy and pre-exponential factors of char particles were obtained. Experimental results show that the kinetic reaction process of char steam gasification follows the shrinking cylinder model. Through linear fitting, it can be obtained that there is a good linear correlation between activation energy and pre-exponential factor, which follows the dynamic compensation effect. Under the same temperature conditions, CaO can accelerate the reaction rate of char, while Fe2O3 can delay the gasification rate of char particles because of sintering phenomenon at high temperature. The synergistic effect of Ca-Fe can reduce the total activation energy of the reaction. The addition of CaO can greatly change the kinetic performance of the Fe2O3 catalyst, inhibit the sintering deactivation reaction of Fe2O3 at high temperature, increase the diffusion path of steam, and promote the char steam gasification reaction.

Влияние средств огнезащиты на интенсивность прогрева и особенности обугливания деревянных конструкций

Introduction. Over the past decades, the sphere of wooden house construction has been undergoing revolutionary changes in relation to the development of large-scale construction using wood-based structures. In this regard, one of the first places is the direction associated with ensuring the fire-safe use of such structures in the construction of buildings and structures of various functional purposes. An important sector of this direction is various types and methods of fire protection for wood, materials and structures based on it. The lack of systematic research on these issues hinders the development of effective technical solutions for fire protection of wooden structures. Goals and objectives. Identification of priority areas for research in the field of fire protection of wood, materials and structures based on it. Development of effective flame retardants that can have an impact on reducing fire danger and increasing the fire resistance of wooden structures. Determination of the influence of various flame retardants on the intensity of the process of heating and charring of elements of wooden structures in conditions of fire exposure (fire). Methods. A standard muffle furnace of the SNOL type was used as a test installation with the possibility of one-sided radiation thermal effect on the sample surface and a uniform temperature increase in the furnace up to 1200 С. The muffle furnace was upgraded taking into account the horizontal fixing of the sample on the outer panel of the furnace. To measure the temperature by the thickness of the sample, a set of thermoelectric converters of type K (chromel-kopel) with a junction diameter of 0,8 mm was used. Results and their discussion. Based on the results of theoretical and experimental studies, the main directions of research on the possibility of using various methods and types of fire protection to achieve the required fire hazard characteristics and fire resistance of wooden structures were determined. During the study, the analysis of such characteristics of charring as the rate of charring, the thickness of the charred layer was carried out. Conclusion. The research results show the possibility of certain classes of flame retardants, intumescent and heat-protective materials not only to influence the intensity of the process of charring wood, but also to affect the properties and structure of the charred layer, as well as the intensity of heating of the inner layers of wooden structures. Key words: fire resistance, fire resistance limit, fire hazard, charring, heating intensity, flame retardant efficiency, wood, wooden structures, flame retardant coatings, flame retardants.

Potential amendments for improving productivity of low carbon semiarid soil

AbstractApplying soil amendments with high C content can potentially improve soil properties and increase crop yields. The objective of this 3‐yr field study was to evaluate the effects of organic amendments on soil organic C (SOC), chemical properties, crop nutrient uptake, and crop yields in a low C sandy loam soil near Scottsbluff, NE. The field was planted to dry bean (Phaseolus vulgaris L.) in 2017, maize (Zea mays L.) in 2018, and sugar beet (Beta vulgaris L.) in 2019. Char at 22.3, 44.6, 66.9, 89.2, and 133.8 Mg ha–1; biochar at 5.6 and 11.2 Mg ha–1; and composted manure and municipal compost each at 33.6 and 67.2 Mg ha–1 were applied and incorporated into the soil. In 1 yr after application, organic amendments increased SOC level in top 20 cm by 7–60%. In the second year, maize leaf tissue Fe was greater with char treatments and high biochar rate compared with the control. Greater Fe uptake in beet leaf tissue or trend for such was observed in amendment treatments at high rates compared with low rates and the control in the third year. Maize yield was enhanced with char, municipal compost, and high compost manure rate. Biochar was applied at lower rates than other amendments, and it had no effects on the parameters studied. Results suggest that locally available organic products can be potential soil amendments to increase SOC and enhance productivity. Care needs to be taken to prevent salt buildup and unwanted toxic material accumulation associated with amendments.