Composition Of Char Research Articles

Novel cardanol-containing boron-modified phenolic resin composites

To improve the thermal stability of phenolic resin and develop functional sustainable adhesive, a thermal-resistant cardanol-containing boron–phenolic resin (CBPR) was prepared by copolymerizing salicyl alcohol, cardanol, and boric acid. The structure of CBPR was characterized by Fourier transform infrared spectroscopy. Thermal stability of the investigated composites was estimated using thermogravimetric analysis (TGA). The results of TGA indicated that the modified resin exhibited excellent thermal stability. Specifically, the B-0.2 thermoset had a char yield of 69% when the boron content was only 1.27 wt%. The curing kinetic behavior was well described by differential scanning calorimetry and model-free kinetic analysis. Further, CBPRs, nano-aluminum oxide powders, glass powders with low melting point, and vitreous silica fibers were used as resin matrix, filler, forming additive, and reinforced material, respectively, to produce a novel ceramizable phenolic molding composite. The ablative characteristics of the co-cured blends were explored in terms of linear/mass ablation rate and microscopic pattern of ablation via the oxyacetylene torch tests. After thermal treatment, the formation and growth of the ceramic phase enhanced the thermal stability and ablation performance of the composites at high-temperature region. The morphology and phase composition of the residual chars were studied by scanning electron microscopy and energy dispersive spectroscopy, respectively. The linear and mass ablation rates for the modified composites decreased obviously in comparison with those of the unmodified composites, indicating that the modified composites possessed enhanced thermal stability and ablation property.

Composition of char obtained by agricultural and woody biomass pyrolysis

Composition of char obtained by agricultural and woody biomass pyrolysis

On the novel designs of charring composites for thermal protection application in reentry vehicles

To optimize the performance of the thermal protection system in reentry vehicles subjected to aerodynamic heating, we develop the nonlinear pyrolysis layer model and then present two kinds of novel designs of charring composites. Based on this model, the thermal behaviors of homogeneous and non-homogeneous charring composites under aerodynamic heating are simulated by means of the computer codes that we have written. The numerical results indicate that density variation schemes of novel designs can improve the thermal protection performance of homogeneous composites, e.g. the piecewise linear and the parabola designs have larger effective heat capacity than homogeneous composites. This study will be helpful for the design of charring composites for thermal protection application in reentry vehicles.

Gasification behaviors and kinetic study on biomass chars in CO2 condition

Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of four biomass chars. The chemical composition and microstructures of biomass chars were analyzed by chemical analysis, scanning electron microscope (SEM) and BET method. The results show that the initial gasification temperature (T0.1) and total gasification temperature (T0.9) of peanut shell char (PS-char), corncob char (CC-char) and bamboo char (BB-char) are close, and rice shell char (RS-char) has relatively higher T0.1 and T0.9. Gasification reactivity of biomass char is in the order of BB-char>CC-char>PS-char>RS-char. It has been confirmed by chemical analysis and microscopic structure analysis that there is a good correlation between the biomass char gasification reactivity and the alkali index; that is, the greater the alkali catalytic index, the higher the catalytic effect. The random pore model (RPM), volume model (VM) and unreacted shrinking core model (URCM) were used to fit the experimental data. The results show that the experimental data agree better with the RPM than with other two models. The apparent activation energies of non-isothermal gasification of PS-char, CC-char, BB-char and RS-char calculated by RPM are 238.6kJ/mol, 302.7kJ/mol, 284.9kJ/mol and 242.2kJ/mol.

Influence of the Process Conditions on Yield, Composition, and Properties of the Products Derived from the Thermolysis of Scrap Tire and Used Engine Oil Blends

The thermolysis of waste blends, consisting of shredded scrap tires and used motor oil, was carried out in a semicontinuous distillation reactor. The aim of this research was to investigate the influence of mixture composition, feedstock chopping degree, and pressure on the yield, composition, and properties of thermolysis products, i.e., oil, char, and gas. The distribution of the thermolysis products derived from Tire/Oil (T/O) mixtures was 44.8–60.2% (w/w) of liquid, 22.1–31.6% (w/w) of char, and 17.6–24.6% (w/w) of gas. The highest yield, 60.2% (w/w), of desired product (oil) was obtained from the finer feedstock (Type 1), which was mixed with engine oil in the ratio of 2:2 and thermolyzed at elevated pressure (40 bar). The results of the chemical composition of liquid thermolysis products revealed three dominant classes of hydrocarbons: arenes (21.84–34.48%, w/w), alkenes (21.06–34.54%, w/w), and alkanes (18.36–38.66%, w/w). The liquid products derived from Tire/Oil mixtures can be used as liquid fue...

Cascading microalgae biorefinery: Fast pyrolysis of Dunaliella tertiolecta lipid extracted-residue

The present study aims to valorise, through fast pyrolysis, the solid residue of microalga Dunaliella tertiolecta, after extraction of added-value compounds (β-carotene, phytosterols and fatty acids), which are included in the total lipid fraction, following the “Biorefinery Approach”. This study targets biooil and/or char as pyrolysis end-products. At pyrolysis temperature of 600°C, biooil yield was maximized (45.13wt.%), while char reached 29.34wt.%. Biooil quality was assessed and its potential use as biofuel discussed. In addition, assessment of char composition and properties, either as fertilizer or sorbent for soil remediation, was also discussed. Finally, microalga D. tertiolecta can produce high amounts of lipids which have a high potential application and also renewable fuel/soil amendment by fast pyrolysis of its residue.

Experimental and Modeling Study of the Effect of Torrefaction on the Rapid Devolatilization of Biomass

In the present work, experimental and computational fluid dynamics (CFD) approaches were proposed and applied to assess rapid devolatilization behaviors of four types of biomass (forest residue, torrefied forest residue, Norwegian spruce, and torrefied Norwegian spruce). Biomass particles were subjected to devolatilization experiments at 1073 and 1473 K in a drop-tube reactor. Torrefaction was found to have consistent effects on the size reduction of studied biomass. In addition, similar behaviors of char fragmentation were observed for tested torrefied biomass after rapid devolatilization at 1473 K. Mass loss during devolatilization of biomass was highly dependent on heating condition. Both rates and extents of devolatilization of biomass were increased at elevated temperatures and heating rates. In comparison with raw feedstock, high char yields were realized with the torrefied biomass after devolatilization experiments. Evolution of elemental composition of studied biomass was found to be insensitive to tested conditions. However, organic composition of char was strongly affected by elemental composition of fuel, thus also influenced by torrefaction. CFD simulation showed that sizes of fuel particles had decisive effects on residence time of them in the reactor, especially particles with diameter larger than 355 μm. Particle temperature, in contrast, depended on both particle diameter and particle density. A modified two-competing-rates devolatilization model was also presented in the present work. On the basis of experimental data, one optimal set of kinetic parameters was obtained following a proposed procedure. The model predicted well the mass loss of all tested fuel and the evolution of each organic element in char at all operation conditions.

Determination of pyrolysis behavior of brown coal in a pressurized drop tube reactor

Pyrolysis of a pulverized German brown coal was investigated using a new high pressurized drop tube reactor. Influence of temperature (600, 700, 800 °C), pressure (25, 60 bar (g)) as well as residence time (variation of heated reactor length: 500, 1500, 2500 mm) on pyrolysis product yields as well as char and gas composition were evaluated. Particle heating and residence times of gas and particle in the heated reactor section were calculated based on the obtained data. To trace the pyrolysis progress during particle drop in the reactor tube gas sampling over reactor height was done. A good reactor performance and reliable results for the pyrolysis experiments could be obtained for the new reactor equipment. Only a slight pressure influence on product yields, char composition, and gas composition was found, which was contrary at the different temperatures. This indicates competing reactions taking place at the given conditions. Gas species evolution over the reactor height is mainly promoted by rising temperatures. The long gas residence times in the reactor and the obtained CH4, H2, and C2 and C3 hydrocarbon yields are a result of secondary cracking of tar and gaseous hydrocarbons at temperatures above 600 °C. Furthermore, it was found, that heterogeneous gasification reactions take place at higher temperatures as well. Comparison between thermogravimetric experiments in “drop-in” mode and the DTR results show significant differences attributed to heat transfer limitations in the particle bulk (TGA) and to the long gas residence times (78–368 s) in the drop tube reactor.

Nonlinear pyrolysis layer model for thermal behavior of nonhomogeneous charring materials

ABSTRACTTo improve the performance of charring materials as the thermal protection system in supersonic vehicles subjected to aerodynamic heating, we develop a nonlinear pyrolysis layer model of nonhomogeneous charring composites, propose a scheme of variable density in which the resin distribution of charring materials is taken as a piecewise linear function, and then simulate the thermal behavior of the design by means of the written calculation codes. This model reveals that the thermal behavior of charring materials depends not only upon several key parameters such as heat flux, moving interfaces, moving boundary and temperature‐dependent thermal properties, but also upon variable density. Further numerical investigations point out that the pyrolysis layer plays a very important role in the thermal protection performance. This study will be useful for the optimization of the thermal protection system in supersonic vehicles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42331.

Influence of char composition and inorganics on catalytic activity of char from biomass gasification

Abstract This research investigates the catalytic properties of char which was recovered directly from a biomass gasifier. Poplar wood was gasified in steam and CO2 environments in a fluidized bed reactor at temperatures ranging from 550 to 920 °C. Char was composed of 85% carbon with concentrations of N, H, and S between 0.3% and 3%, depending on gasification conditions. The inorganics (Ca, K, Na, P, Si, Mg) were quantified, revealing that Ca was present in the highest concentration (0.5–1%), followed by K, ranging from 0.1% to 0.8%. The char had catalytic activity for decomposition of methane, which was used as a model molecule. The quantity of inorganics in the char was modified by acid washing in 16% aqueous HCl, which removed >95% of Ca, K, P, and Mg from the char. This resulted in an 18% decrease in the quantity of methane reacted compared to the original char sample, demonstrating that inorganics, which only make up approximately 2% of the char, play a significant role in its catalytic activity for methane cracking reactions. In addition, carbon was found to play an important role in the catalytic activity of the char, both as a catalyst and a support on which the inorganics were dispersed. The activity of carbon free ash was approximately 90% lower than that of char, and deactivated to have no measurable activity after 45 min on stream, demonstrating the importance of carbon and dispersed inorganics for catalytic activity. When char was heated to 1000 °C in N2, inorganics and oxygen migrated to the surface of the char, covering the carbon surface in a metal oxide layer. This decreased the catalytic activity by approximately 40%. Acidic (e.g. carboxylic, lactones) and basic (e.g. carbonyl, pyrone) oxygen functional groups were identified on the char surface. However, acidic oxygen groups desorbed at reaction temperatures, so these groups likely do not participate in cracking reactions.

Pyrolysis of asphaltenes in an atmospheric entrained flow reactor: A study on char characterization

Integration of solvent deasphalting and asphaltenes gasification has been reported as a convenient alternative to coker based upgrading of bitumen, derived from oil sands. However, very limited work has been carried out on pyrolysis and gasification of asphaltenes at entrained flow conditions. The present study aims at addressing this gap, and provides a better understanding of the major intermediate in gasification process – char. Chars were prepared at different operating conditions in an atmospheric entrained flow reactor. Extensive characterization techniques were used to identify the changes in morphology, structure and composition of chars. We estimated the global gasification reactivity of chars with steam and CO2. Chars exhibited an internally hollow structure with porous walls. The nominal size of individual char particles and degree of fragmentation were greatly influenced by the operating conditions. H/C ratio, aromaticity and macro-porosity of chars increased with an increase in operating temperature, while content of heteroatoms and global reactivity showed a gradual decrease. Increase in residence time had marginal effect on char composition, morphology and global reactivity. V and Ni tend to accumulate in chars; however, their effect on global reactivity could not be established.

Kinetics of steam and CO 2 gasification of high ash coal–char produced under various heating rates

Abstract Char particles of high ash Indian coal with different sizes are produced using thermogravimetric method at different heating rates. Particle diameter and porosity changes during devolatilization significantly affect char gasification rates. The effect of coal particle size on char production under various heating rates is reviewed. Char gasification is affected by operating conditions such as reaction temperature, char production method, and particle size in addition to chemical composition and physical structure of char. The measurements of the steam and CO2 gasification rate of the produced chars are performed by an isothermal thermo-gravimetric analysis at the temperatures of 900, 950, and 1000 °C under ambient pressure conditions. It is found that the reactivity of char gasification is increased along with heating rate of char. Three kinetic models are applied to describe the varying conversion rate: volumetric model, grain model, and random pore model. The activation energy of the gasification is varied based on the char generation method and particle sizes. The activation energy is varying from 122 to 177 kJ mol−1 for steam gasification and 130 to 214 kJ mol−1 for CO2 gasification to different sized char particles. The effect of char heating rate on gasification is more pronounced in the activation energies of smaller sized particles.

The effect of temperature and heating rate on char properties obtained from solar pyrolysis of beech wood

Char samples were produced from pyrolysis in a lab-scale solar reactor. The pyrolysis of beech wood was carried out at temperatures ranging from 600 to 2000°C, with heating rates from 5 to 450°C/s. CHNS, scanning electron microscopy analysis, X-ray diffractometry, Brunauer–Emmett–Teller adsorption were employed to investigate the effect of temperature and heating rate on char composition and structure. The results indicated that char structure was more and more ordered with temperature increase and heating rate decrease (higher than 50°C/s). The surface area and pore volume firstly increased with temperature and reached maximum at 1200°C then reduced significantly at 2000°C. Besides, they firstly increased with heating rate and then decreased slightly at heating rate of 450°C/s when final temperature was no lower than 1200°C. Char reactivity measured by TGA analysis was found to correlate with the evolution of char surface area and pore volume with temperature and heating rate.

Does water repellency of pyrochars and hydrochars counter their positive effects on soil hydraulic properties?

Adding carbon-rich solids from pyrolysis (pyrochars) and hydrothermal carbonization (hydrochars) to soils can improve their hydraulic properties and increase the plant available soil water capacity (AWC). However, the effects of the specific char characteristics on soil hydraulic properties are still little understood and thus, difficult to optimize for soil amendment. It is often assumed that the water repellency of chars is an important factor influencing the water retention of soils. In using the evaporation method and saturated conductivity measurements, we investigated how changes of hydraulic properties of a loamy sand with 2% (w/w) char addition depend on (i) production processes, (ii) feedstocks, (iii) particle size, and (iv) wetting properties of added chars. Applied chars comprised pyrochars carbonized at 750°C and hydrochars carbonized at 200°C and 250°C from two different feedstocks (digestate and woodchips) and two particle sizes (<0.5mm and 0.5–1.0mm). The wetting properties of the pure chars and soil–char composites were determined by the sessile drop method. To investigate the impact of the water repellency of chars, pure chars and soil–char composites were saturated by capillary water uptake under atmospheric conditions and by saturation from the bottom under vacuum conditions.The chars showed highly variable wetting properties with the contact angles being strongly correlated to the specific surface area of the chars. The saturated hydraulic conductivity was significantly increased after char addition for both vacuum and capillary saturated samples, while being independent of wettability characteristics. The effects for the unsaturated conductivity were negligible. In contrast to expectation, soil amendments with more water repellent chars caused higher increases of AWC (up to 15%), both after vacuum and capillary saturated conditions. Highest increase of AWC occurred for chars from digestate material, particle size fractions <0.5mm, and chars hydrothermally carbonized at 200°C. The increase of AWC only occurred in the low pressure range (pF1.8 to 2.5), whereas it was decreased in the high pressure range (pF2.5 to 4.2). Our study indicates that water repellency of pyrochars and hydrochars have little counteracting effect on the overall improvement of soil water retention and saturated conductivity, and other factors that also depend on production process and feedstock, such as particle size, intra-particle porosity, shape, and plasticity are more important.

Hemicellulose, cellulose and lignin interactions on Arundo donax steam assisted pyrolysis

Slow Steam pyrolysis of Arundo donax is proposed as possible process for the recovery of a solid material suitable to be used as biochar. In view of the evaluation of the feasibility of such a process, products yields, surface area of char and energetic content of gaseous products needed to assist energetically the process are relevant data to be evaluated in dependence on process operating conditions and biomass characteristics. Biomass main components (hemicellulose, cellulose and lignin) contribute to a different extent to the determination of products yield and characteristics both for their own intrinsic chemical nature and for the onset of possible interactions due to their simultaneous presence in a real biomass. Moreover, it is known that inorganic elements present in the biomass can affect pyrolysis mechanisms and consequently products yields and characteristics. In the present paper the influence of inorganic species and of possible interactions between biomass main components on pyrolysis of A. donax has been studied. To this aim steam assisted pyrolysis tests have been carried out on a mixture of xylan, cellulose and lignin resembling the composition of A. donax canes in a proper experimental apparatus up to 873K, at pressure P=5×105Pa and heating rate HR=5K/min. Products yields, gas releasing rate as function of the temperature, gas composition and specific internal surface of char have been compared to the data computed from the superposition of the results obtained for the single components and to the behavior of untreated and demineralized samples of A. donax canes processed in the same experimental apparatus in the same operating conditions. Results obtained from this study show that primary pyrolysis of holocellulose is affected by the presence of inorganic species that depress the devolatilization of heavier compounds in favor of cracking reactions determining a higher release of light compounds, CO2 and CO. Moreover, interactions between lignin and cellulose are relevant in operating conditions where mass transfer phenomena cannot be neglected. Interesting results have been obtained for the solid residue as for the development of its internal surface that seems to be reduced from both interactions between biomass components and presence of inorganic ions.

An Investigation of the Elemental Composition, Surface Properties, and Soluble Fraction of Kaiyang Bituminous Coal Chars

The effects of heating manner and charring temperature (CT) on elemental composition, surface properties, and soluble fraction of chars from the pyrolysis of Kaiyang bituminous coal (KBC) were investigated. The results show that the chars formed by slowly heating KBC to higher CTs have higher ash and carbon contents but lower volatile matter yield, hydrogen, nitrogen, and sulfur contents, smaller specific surface area and pore volume, and lower extract yields in isometric carbon disulfide/acetone mixed solvent. The compounds detected in the extracts can be classified into aromatics, normal alkanes (NAs), and hexadecane derivates (NADs). The total contents (TCs) of the group components (GCs) in the extracts of the chars formed from rapidly heating KBC increased in the order: aromatics > NADs > NAs, but the TC of aromatics decreased, whereas the TCs of other GCs increased with raising CTs. In contrast, the TCs of the GCs in the extracts of the chars formed from slowly heating KBC to 950°C increased in the order: NADs > NAs > aromatics, while the total content of aromatics increased, whereas the the increase in the TC of aromatics, decrease in the TC of NADs, and almost no change in the TC of NAs were observed.

Evaluation of solid fuel char briquettes from human waste.

The developing world faces dual crises of escalating energy demand and lack of urban sanitation infrastructure that pose significant burdens on the environment. This article presents results of a study evaluating the feasibility of using human feces-derived char as a solid fuel for heating and cooking and a potential way to address both crises. The study determined the energy content and the elemental composition of chars pyrolyzed at 300, 450, and 750 °C. Fecal chars made at 300 °C were found to be similar in energy content to wood chars and bituminous coal, having a heating value of 25.6 ± 0.08 MJ/kg, while fecal chars made at 750 °C had an energy content of 13.8 ± 0.48 MJ/kg. The higher heating values of the studied chars were evaluated using their elemental composition and a published predictive model; results found good agreement between the measured and predicted values. Fecal chars made at low temperatures were briquetted with molasses/lime and starch binders. Briquettes made with 10% starch had an average impact resistance index of 79 and a higher heating value of 25 MJ/kg. These values are comparable to those of commercial charcoal briquettes, making fecal char briquettes a potential substitute that also contributes to the preservation of the environment.

Effect of Titanium Oxide on Fire Performance of Intumescent Fire Retardant Coating

The objective of this research work was to study the thermal efficiency of intumescent fire retardant coating (IFRC) designed to protect structural steel in event of fire. IFRC has been effectively developed by using ammonium polyphosphate (APP), expandable graphite (EG), melamine (MEL), boric acid (BA), titanium oxide (TiO2), and bisphenol A BE-188 with polyamide amine H-2310 as curing agent. Six formulations were developed using different weight percentage (wt. %) of TiO2 and samples were tested for char expansion in furnace at 500°C for 2 h. Bunsen burner test was used to investigate the thermal performance of coating and its performance was compared by using thermal margin value. FESEM was used for char morphology. Char composition was analyzed by XRD and FTIR. Results showed that the coating with 4 wt. % of TiO2 provides better thermal insulation to the steel substrate.

Thermodynamic analysis for syngas production from volatiles released in waste tire pyrolysis

This paper shows the maximum limit on syngas composition obtained from volatiles released in waste tire pyrolysis when they are submitted to an air–steam partial oxidation process. Thus, from mass and energy balances and a stoichiometric equilibrium model, syngas composition and reaction temperature as well as some process parameters were predicted by varying both the equivalence ratio (ER) and the steam to fuel ratio (SF). In addition, pyrolysis experiments were performed using a continuous auger reactor, and the influence of pyrolysis temperature on composition of both volatiles and char was studied. Consequently, the resulting syngas characteristics were correlated with the pyrolysis temperature. The stoichiometric equilibrium model showed that an ER down to 0.4 is a practical limit to perform the air–steam partial oxidation process. When the process is carried out only with air, volatiles obtained at high pyrolysis temperature lead to lower reaction temperature and higher LHV of syngas in comparison with those found at low pyrolysis temperature. The H2 production is favored between 0.20 and 0.40 of ER and seems to be more influenced by the H/C ratio than by the water gas-shift reaction. On the other hand, the steam addition shows a more notable effect on the H2 production for volatiles obtained at the highest pyrolysis temperature (600°C) in agreement with the lower reaction temperature under these experimental conditions. This thermodynamic analysis provides essential data on the optimization of syngas production from volatiles released in waste tire pyrolysis prior to run any test.

The Oxidation of Chars From Huainan Bituminous Coal

The effects of heating manner and charring temperature on chemical composition of chars from the pyrolysis of Huainan bituminous coal were investigated. The results show that the chars formed from Huainan bituminous coal by slowly heating to higher charring temperature have higher ash and carbon contents along with lower volatile matter, hydrogen, nitrogen, and sulfur contents. The yields of water-soluble portions, which, obtained from the oxidation of the extraction residues obtained at higher pyrolysis temperatures and for longer pyrolysis periods of time are higher; the water-soluble portions mainly consist of benzenepolycarboxylic acids, including phthalates to benzenehexacarboxylic acids, suggesting that the extraction residues obtained are composed of condensed aromatics. The above results provide an important scientific basis for understanding the compositions and high value-added utilizations of coal char.