Primary Devolatilization Research Articles

Multi-step kinetic mechanism coupled with CFD modeling of slow pyrolysis of biomass at different heating rates

This study employed numerical modeling to investigate the reactivity and kinetics involved in the slow pyrolysis of lignocellulosic biomass. The model integrates a biomass multi-step kinetics scheme with heat, momentum, and mass transfer, and it was based on the transport of species and flow in a porous medium approach. To develop the multi-step kinetics model, two samples of biomass, avocado stone (AS) with a high hemicellulose content and α-cellulose (CEL), were subjected to TGA experiments in an inert atmosphere. Furthermore, several experimental data in the literature on the evolution of slow pyrolysis products and data obtained by TGA experiments were considered to refine and validate the proposed kinetic mechanism. The temperature range, from 25 to 700 °C, was explored using different heating rates (10, 20, and 40 °C/min). Experimental results showed that CO and CO2 are the predominant gases during primary devolatilization, whereas H2 and CH4 result from secondary reactions at temperatures above 400 °C. The proposed mechanism involves computational fluid dynamic (CFD) simulations of laboratory-scale biomass pyrolysis, comparing temperature and species concentrations with experimental data. The predicted results for individual non-condensable gas mass yields showed an average relative error of below 6.90 % and 11.59 % for CEL and AS, respectively. In the case of biochar, the error was 6.41 % and 9.74 % for AS and CEL, respectively. The developed kinetic model can be applied to simulate the slow pyrolytic degradation of biomass based on its chemical composition.

Simulating the Rapid Devolatilization of Mineral-Free Lignins.

Lig-FC is a network depolymerization mechanism for the rapid primary devolatilization of mineral-free lignins that has already been validated with test data on 16 lignin samples. This paper expands the validation with an additional 13 lignins, including cases that applied different lignin preparations to the same feedstock. The validations reported here cover 27 mineral-free lignins for temperatures to 1150 °C, heating rates from 30 to 8000 °C/s, contact times after heatup to 90 s, and pressures from vacuum to 0.13 MPa. Lig-FC accurately depicts the impacts of lignin quality, heating rate, temperature, contact time, and pressure on the major products and oils' molecular weight distributions (MWDs). All raw lignins contain abundant oil precursors that are released as oils via flash distillation as soon as a flow of noncondensables carries them into the free stream. Consequently, lignin MWD is an essential aspect of lignin constitution because it determines the inventory of inherent volatile chains subject to unhindered flash distillation. Lighter lignin MWDs have larger inherent inventories and therefore produce more oils than heavier MWDs at the onset of devolatilization. Oil yields diminish and char yields increase for progressively heavier MWDs and heavier mean monomer weights and for lignins with relatively less H and more O compared to C.

Modelling and verifying multi-path product generation pyrolysis of waste cabbage leave

This research employs a conventional pyrolysis mechanism model to determine the characteristics and kinetics of waste cabbage leave pyrolysis. Further analysis is conducted using the Multi-path Product Generation model to support the findings. The samples were pyrolyzed from ambient temperature to 1073.15 K at heating rates of 20, 30, 40, and 50 K/min. Average activation energies obtained for waste cabbage leave through the Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Starink methods ranged from 102.44 to 319.71 kJ/mol, 105.43–296.83 kJ/mol, and 115.36–366.19 kJ/mol, respectively. The average values across these methods were 183.97, 181.08, and 207.42 kJ/mol, displaying noticeable variation in activation energies depending on the method employed. Additionally, the model demonstrated: (i) pyrolysis attributes in multi-path reactions, (ii) product-generating regime development, and (iii) valuable insights of pyrolysis product yield and composition. The model comprises three primary devolatilization reactions (iChar, iGas, iTar), two tar cracking reactions (tar to char, tar to gas), and one secondary char reaction. The model parameters accurately align with the thermogravimetric curves at varying heating rates, which demonstrate the progression of multiple product pathways. Thus, this model can be effectively utilized for the simulation of multi-path pyrolysis processes.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass. 8. Validations for hardwoods

This study redevelops and validates a reaction mechanism called bio-FLASHCHAIN® (bio-FC™) to simulate the rapid primary devolatilization of any hardwood at any operating conditions. It presents evaluations with test measurements on 30 hardwood samples at temperatures from 300 to 1400°C; heating rates from 1 to 7200°C/s; contact times to 1800 s; and pressures from 0.01 to 0.13 MPa. Collectively, the test data cover the yields and elemental compositions of oils and char and the yields of CO, CO2, and H2O, but largely exclude light oxygenated gases and H2. Bio-FC™ accurately simulates complete product distributions for a broad selection of hardwoods with widely variable compositions, major component percentages, and AAEM levels, and correctly depicts how variations in heating rate, temperature, contact time, and pressure shift these distributions. This is the first time a reaction mechanism has displayed all these capabilities. The only persistent flaw in the data evaluations is that simulated H-contents of oils are low by approximately 1 wt%. Proximate and ultimate analyses, the percentages of cellulose, hemicellulose, and lignin, and AAEM loadings are required input. Nearly all kinetic parameters were specified directly from previous validations of the submechanisms for mineral-free and AAEM-loaded cellulose, hemicelluloses, and lignins. Cellulose devolatilization invokes both spontaneous and catalytic reaction channels but only spontaneous channels are activated for hemicellulose and lignin because AAEM loadings in hardwoods are moderate. According to bio-FC™, the distinctive devolatilization behavior of particular wood samples is due to acute sensitivities to both heating rate and AAEM loading in the cellulose-derived yields of oils and char, whereas compositions of oils and chars are most sensitive to cellulose percentages in woods. These dependences obscure the relations among cellulose percentages in whole woods and the contributions that cellulose makes to devolatilization products of whole woods, which vary widely among hardwoods. Sensitivities to variations in heating rate and AAEM loading are much weaker in hemicelluloses and lignins.

Thermo‐chemical conversion of pre‐treated cucumber peel

AbstractIn this study, cucumber peel (CP) was treated with Calcium Hydroxide i.e. Ca(OH)2 and its thermal behavior was examined. The pre‐treated cucumber peel (PTCP) was thermally degraded mainly through three steps; first, moisture and light volatile compounds loss (30–132°C); second, primary devolatilization (132 to 337°C) involving intense degradation with mainly re‐formation process and third and final, secondary reactions (337 to 800°C). Lower PTCP activation energy (192.77–183.33 KJ/mol) reflects its easy thermal conversion initiation. The non‐condensable compounds (CO2 & CH4) and condensable products (H2O, CH3CH2OH, CH3COOH, C=C, C6H5OH, HCOOH) were found as 29.75% and 70.25% respectively determined by TG‐FTIR analysis. While, with temperature, relative concentration of condensable compounds decrease significantly and found as 61.38% and 42.5% at lower and higher temperature respectively. By Py/GC–MS analysis, presence of the high energy optimizing compounds and valuable chemicals, i.e. toluene (5.12%), benzene (4.31%) and phenols (27.38%) was confirmed. All these datasets shows that pre‐treatment of CP with Ca(OH)2 might be suitable approach to produce Bioenergy and Bio‐chemicals.

On the primary devolatilization of hemicellulose

This paper presents validation cases on a reaction mechanism for the primary devolatilization of hemicellulose called “hemi-FC.” The analysis incorporates depolymerization via random scission; charring via monomer decomposition, semichar decomposition, and thermal annealing; fragmentation statistics; and the flash distillation analogy. It predicts the yields and elemental compositions of bio-oil and char, oil molecular weight distributions, and the yields of CO, CO2, H2O, H2, and light oxygenates. A single set of model parameters accurately interprets the partitioning of hemicellulose with cation levels from 5000 to 30,000 ppmw into oil, noncondensables, and solid residue for temperatures to 900 °C, heating rates from 10 °C/min to 6000 °C/s, contact times after heatup to 1800 s, and pressures of vacuum and 0.1 MPa. The model results are generally within useful quantitative tolerances of the measured values across the domain of test conditions. Nonetheless, the commercial xylans that have been tested devolatilize at much cooler temperatures than cellulose and produce more gas and char and less bio-oil primarily because their decomposition is strongly catalyzed by excessive residual amounts of Na and Ca from the hemicellulose extraction process. These cation loadings are definitely heavy enough to grossly distort the dynamics of the spontaneous reaction channels and ultimate devolatilization behavior. Consequently, the spontaneous, uncatalyzed reaction channels for hemicellulose devolatilization remain uncharacterized even while they are bound to be prominent in the devolatilization of many natural hemicellulose forms.

Predicting the rapid devolatilization of mineral-free cellulose

This paper extends the validation of a reaction mechanism for the devolatilization of mineral-free cellulose called “cel-FC.” A single set of model parameters accurately interprets the partitioning of raw cellulose into oil, noncondensables, and solid residue and oil molecular weight distributions (MWDs) for temperatures to 600 °C, heating rates from 60 to 6000°C/s, contact times to 120 s, and pressures of vacuum and 0.1 MPa. The analysis incorporates depolymerization via random scission and unzipping from chain ends; charring via monomer decomposition, spontaneous charring, and thermal annealing; fragmentation statistics, and the flash distillation analogy. Random depolymerization is responsible for the induction of primary cellulose devolatilization and eventually generates chains short enough to vaporize. The accompanying surge in the relative concentrations of chain ends activates the unzipping process. The fastest oil production rates are driven by scission plus unzipping and mediated by flash distillation. Whenever vaporization of longer oil precursors is limited, unzipping delivers monomer derivatives into the oil. Whenever longer volatile chains can freely vaporize they are no longer subject to unzipping or scission, so there are necessarily fewer monomers in oil. This is why ultimate oil yields are essentially the same across broad ranges of heating rate, temperature (given sufficient contact time at low temperatures), and pressure, and why oil MWDs shift toward heavier molecular weights for progressively faster heating rates, hotter temperatures, and lower pressures. Cel-FC interprets the optimal primary products - 94 wt% oil plus a mixture of light oxygenates, CO2, and CO in H2O – as the limit of depolymerization via scission and unzipping without any charring reactions. Monomer decomposition and spontaneous charring produce hardly any bio-char from mineral-free cellulose but are major sources of noncondensable gases and responsible for greater gas yields for slower heating rates, hotter temperatures, and higher pressures.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass. 4. V.2.0 decomposition mechanism for mineral-free cellulose

According to cel-FC, the essential aspects of cellulose devolatilization are (1) Depolymerization reactions that disintegrate cellulose chains into a fragment distribution; (2) Probabilities that a given bond rupture produces a certain chain size; (3) A charring cascade that inhibits subsequent bond ruptures while bound glucose monomers decompose into progressively more refractory structures plus noncondensable gases; and (4) The Flash Distillation Analogy whereby volatile chains in the condensed phase vaporize into escaping noncondensable gases, depending on the molecular weight, temperature, and pressure. Predictions from cel-FC are evaluated with measured product distributions including bio-oil molecular weight distributions (MWDs) from mineral-free cellulose for temperatures to 900 °C, heating rates from 100 to 5000 °C/s, contact times to 30 s, and pressures from vacuum to 6.9 MPa. Cel-FC accurately depicts the impacts of temperature, heating rate, and pressure on the major products of primary cellulose devolatilization. Devolatilization during slow heating occurs at relatively cool temperatures where vaporization is limited for all but the lightest oil precursors. Unzipping circumvents this bottleneck by delivering a preponderance of monomer derivatives into the cumulative oil sample. Devolatilization at fast heating usually occurs at hotter temperatures where longer volatile chains can freely vaporize and produce an oil with relatively few monomers but abundant longer depolymerization fragments. As longer precursors vaporize, there are necessarily fewer monomers in a cumulative oil sample. This same observation explains why ultimate oil yields vary little across broad ranges of heating rate, temperature (given sufficient contact time at low temperatures), and pressure, and why oil MWDs shift toward heavier MWs for faster heating rates, hotter temperatures, and lower pressures. Cel-FC also interprets the optimal primary products - 94 wt% oil plus a mixture of light oxygenates, CO2, and CO in H2O – as the limit of depolymerization via scission and unzipping without any charring.

A Study on the Pyrolytic Characteristics of Xanthoceras Sorbifolia Husk and Its Crude Cellulose Extract

Huge amounts of Xanthoceras sorbifolia husks (XSH) are typically discarded after oil extraction. Since pyrolysis represents a promising solution to harness the bio-energy of XSH, in the present work the pyrolytic and kinetic characteristics of XSH and related crude cellulose extract (CCE) were studied considering different rates of heating (10, 30 and 50°C min−1). The pyrolysis activation energy, pre-exponential factors and mechanism function were computed using different models namely Popescu, FWO (Flynn-Wall-Ozawa) and KAS (Kissinger-Akahira-Sunose). The pyrolysis process was articulated into three stages: dehydration (Stage I), primary devolatilization (Stage II), residual decomposition (Stage III). Marked variations in the average activation energy, thermal stability, final residuals and rate of reaction were noted. Stage II of XSH and CCE could be described by the Avramic-Erofeev equations. The average activation energies of XSH and CCE were found to be 269 and 296 kJ mol−1, respectively.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 3. Predicting total yields for torrefied grasses and agricultural residues

This paper extends the interpretation of volatiles yields from torrefied woods in Part 2 to torrefied grasses and agricultural residues (AgRes). The analysis retains the original reaction mechanism and depolymerization kinetics, and implements the fuel constitution submodel from Part 2 that uses the carbon aromaticity added during torrefaction to determine the impacts on primary devolatilization behavior. Torrefaction replaces bridges with char links within macromolecules of both cellulose and lignin and these added char links are entirely responsible for the reductions in volatiles yields, since the primary devolatilization of torrefied biomass abides by the same reaction kinetics as the parent raw biomass. The added char links are estimated without any adjustable parameters, given only an ultimate analysis for the torrefied biomass, plus an ash content for AgRes. Consequently, depolymerization statistics, rather than chemical kinetics, govern the reductions in volatiles yields from torrefied samples. The predictions are validated with volatiles yields from 10 grasses and 20 torrefied grasses, and from 6 AgRes and 16 torrefied AgRes for heating rates from 10 °C/min to almost 104 °C/s; temperatures from 470 to 1200 °C; pressures from 0.1 to 3 MPa; with contact times from tens of milliseconds through tens of minutes.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 1. Lignin devolatilization

This study validates a modeling framework to accurately predict the total and tar yields from any lignin at any devolatilization conditions. The original reaction mechanism and depolymerization kinetics in bio-FLASHCHAIN® are slightly modified for pure lignin, and used to accurately interpret how the molecular weight distribution (MWD) of a lignin governs its primary devolatilization behavior. The only sample-specific input requirements are an ultimate analysis and a weight-average molecular weight (MW), although a measured MW-value is not needed for lignin in whole biomass. Predicted total and tar yields are validated with measured values from 20 diverse lignins for heating rates from 10 °C/min to 5000 °C/s to temperatures from 430 to 950 °C with contact times of several seconds. Predicted tar yields increase for progressively lighter lignin MWDs, and accurately depict how variations in lignin MWD affect total volatiles yields. The strong impact of lignin MWD on its primary devolatilization behavior is accurately interpreted by the flash distillation analogy without any adjustments to the reaction kinetics for a diverse assortment of lignins. The entire reaction mechanism in bio-FLASHCHAIN® is required with non-pyrolytic lignins, whose predicted total and tar yields increase in inverse proportion to reductions in MW. For pyrolytic lignins, bridge scission is superfluous because the whole lignin falls within the size range for tar precursors initially and throughout devolatilization. Consequently, neither total nor tar yields are affected by MW variations because the tar vaporization rates are maximized throughout this MW range. Devolatilization shifts toward hotter temperatures for progressively faster heating rates, in good agreement with data, whereas predicted total and tar yields are insensitive to heating rate variations. Total yields increase for progressively hotter temperatures due to the transition from tar production to char decomposition in the reaction mechanism. Tar yields saturate to an asymptotic ultimate value at approximately 550 °C for fast heating rates.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 2. Predicting total yields for torrefied woods

Apparently, no detailed reaction mechanisms for any torrefied biomass have yet been put forward. This study expands bio-FLASHCHAIN® to accurately predict the total volatiles yields from any torrefied wood. Whereas the original reaction mechanism and depolymerization kinetics are retained, the analysis introduces a fuel constitution submodel that uses the carbon aromaticity added during torrefaction to estimate the changes in torrefied woods that are responsible for the impacts on primary devolatilization behavior. Torrefaction replaces bridges with char links within wood macromolecules of both cellulose and lignin and these added char links are entirely responsible for the reductions in volatiles yields. The added char links are estimated without any adjustable parameters, given only an ultimate analysis for the torrefied wood. The primary devolatilization of torrefied woods abides by the same reaction kinetics as the parent raw woods, except that the energy distribution for bridge scission narrows for progressively more severe torrefaction conditions to coarsely represent the elimination of the most reactive components during torrefaction. The predictions are validated with volatiles yields from 13 woods and 22 torrefied woods for heating rates from several hundred to more than 104 °C/s to temperatures from 500 to 1000 °C with contact times from tens of milliseconds through several minutes. According to this interpretation, the most important chemistry to unravel in raw and torrefied woods is the accumulation of furans and benzenoid and condensed aromatics in cellulose throughout all stages of both torrefaction and primary devolatilization.

Simulating volatiles conversion in dense burning coal suspensions. 1. Validation of chemical reaction mechanisms

The fuels that burn in dense coal suspensions are mixtures of CH4, C2H2, H2, CO, HCN, and H2S, char, and soot. All these fuels except soot effectively compete for the available O2 throughout volatiles conversion, which significantly affects N-species transformations. This simulation study validates a collection of detailed reaction mechanisms that accurately interprets how coal quality and inlet O2 level affect all the major reactants, intermediates, and products, including N-species, within dense burning coal suspensions. Predicted flame structures are generally within measurement uncertainties for three diverse coals and inlet O2 levels from 2 to 15%, provided that the kinetics for tar decomposition into soot, CO, H2, and gaseous hydrocarbons are implemented in a particular way. Tar decomposition kinetics should always be evaluated at the particle thermal history to ensure that they keep pace with primary devolatilization so that gaseous hydrocarbons can mediate HCN conversion into NO under locally reducing atmospheres. Moreover, gaseous hydrocarbons that would otherwise add to soot during the later stages in inert atmospheres should be burned in the free stream along with other noncondensable fuel components, again, to mediate NO production under reducing conditions. However, radical scavenging and heterogeneous NO reduction on soot appear to be superfluous. These findings reveal an important qualification on the limiting scenario for complete mixing of volatiles into an entrainment stream before they are converted: Tars must coalesce into soot in the immediate vicinity of their parent particles even while noncondensable fuels are fully dispersed across an entrainment stream; otherwise, hydrocarbons, H2, and CO will be unavailable to mediate HCN decomposition into NO.

Predicting the Distributions of Oxygen Species from Primary Devolatilization of Coals

Starting from an extension to FLASHCHAIN, this study interprets the evolution of coal oxygen during primary devolatilization. CO2 and H2O are primarily formed via bridge charring that accompanies d...

Predicting ultimate soot yields from any coal

This study presents a simple prediction method for soot yields from any coal, provided that the thermal processing is severe enough to completely incorporate all the aromatics in primary tars and oils into a so-called ultimate soot yield, and given the yield and elemental composition of primary tar. It also introduces a 3-step quasi-global reaction scheme to describe the dynamic approach to ultimate soot yields for deployment in CFD furnace simulations, where the rate parameters are evaluated to match the predicted dynamics from a comprehensive tar conversion mechanism. The predicted ultimate soot yields are validated with measurements for coal ranks from brown coals to anthracites, for heating rates of at least several thousand degrees per second; temperatures from 900 to 1300 °C; and tar contact times from 75 ms through 14 s. Primary tar, defined as the aggregate amount of all condensed aromatics from primary devolatilization, determines the ultimate soot yields from any coal at any operating conditions. Ultimate soot yields from any coal can be evaluated from the yield and FLASHCHAIN®-based elemental composition of primary tar as accurately as they have been measured. On average, only 18% of the primary tar mass is excluded from the ultimate soot product, which mostly reflects the exchange of C2H2 into soot for the CO that carries away tar-oxygen. This exchange nearly compensates for the much more extensive elimination of heteroatoms and aliphatics from tar during soot production. The proposed three-step global scheme accurately depicts the reaction dynamics for tar decomposition at elevated temperatures from the full tar decomposition mechanism, including the maximum and ultimate saturation value of secondary tar. Whereas the kinetic parameters for primary and secondary tar display the established tendencies for different operating conditions and coals, those for soot production are remarkably uniform across this domain.

Predicting nitrogen release during coal tar decomposition

This paper develops a detailed phenomenological reaction mechanism for N-species transformations throughout tar decomposition, including tar-N sequestration into soot. It expands the previously validated mechanism for tar decomposition based on FLASHCHAIN® theory to cover N-transformations during pulverized fuel firing. Tar-N transformations are described by two distinctive features: (1) An elimination reaction that produces HCN governs the decay in the average moles of nitrogen per aromatic nucleus throughout tar decomposition; and (2) Empirical observations determine the fraction of tar-N incorporated into soot. Validation cases represent heating rates of at least several thousand degrees per second; temperatures from 600 to 1100 °C; tar contact times from 75 ms through 2 s; and coal ranks from subbituminous through low volatile bituminous. The predicted partitioning of coal-N into tar-N, HCN, soot-N, and char-N was within measurement uncertainties for all coals for simulated p. f. firing conditions, including the variation in fractional char-N levels from 0.4 to 0.8 across this domain. Since primary tar-N levels are directly proportional to fractional primary tar yields, and since ultimate soot-N levels account for one-third of tar-N with any coal type, the ultimate coal-N partitioning for CFD furnace simulations can be accurately described with two analyses: (1) A primary devolatilization mechanism to predict primary tar yields under rapid heating conditions; and (2) A submechanism to predict HCN release from char throughout devolatilization up to the point of char ignition. Dynamics may be resolved with either global reactions or the full tar decomposition mechanism, depending on the impact of the lag between tar decomposition and soot production in the subject application.

FLASHCHAIN Theory for Rapid Coal Devolatilization Kinetics. 10. Extents of Conversion for Hydropyrolysis and Hydrogasification of Any Coal

This paper extends FLASHCHAIN theory with mechanisms for (i) hydrogenation of labile bridges in the condensed coal phase which enhance tar yields during primary devolatilization under some, but not all, conditions and (ii) heterogeneous hydrogasification of char into CH4. Under the H2 pressures associated with entrained coal gasification technology, coal devolatilization at heating rates faster than 103 °C/s does not provide sufficient time for appreciable bridge hydrogenation so tar yields are not enhanced. Conversely, tar yields under slow heating conditions are strongly enhanced. The mechanisms proposed for bridge hydrogenation and its associated impact on fragment recombination in FLASHCHAIN accurately depict the joint impact of heating rate and H2 pressure on tar yields. Whereas tar yields from rapid devolatilization diminish for progressively higher pressures, total weight loss remains steady or passes through a minimum at some H2 pressure around 1 MPa, because char hydrogasification counteracts the lower weight loss associated with diminished tar yields at progressively higher pressures. A single, half-order methanation reaction within the CBK/G framework gave results within the measurement uncertainties through 15 MPa H2. In combination, the mechanisms for hydropyrolysis and hydrogasification accurately interpreted a database representing coals of rank from lignite to medium volatile bituminous; heating rates from 1 to 103 °C/s; temperatures from 550 to 1150 °C; reaction times to 180 s; and particle diameters to 1 mm. The assigned hydrogasification reactivities are far less variable than those for char gasification by steam and CO2, and show no consistent trend with rank.

Modelling heat of reaction in biomass pyrolysis with detailed reaction schemes

Primary devolatilization and the exothermic heterogeneous secondary charring of the primary volatiles need to be described in a consistent manner in order to correctly predict the heat of reaction of biomass pyrolysis. Detailed reaction schemes can currently predict mass loss and product composition of biomass pyrolysis with good accuracy, but have a weakness in the description of the heat of reaction. In this work it is shown for the first time that including secondary charring reactions a detailed reaction scheme can predict the evolution of the heat of pyrolysis for different conditions. The enthalpy of reaction is calculated for each reaction as the difference between the net calorific value of reactants and products. The presented model is able to describe the heat evolution in micro-TGA-DSC experiments conducted without a lid, where pyrolysis is endothermic, and with a lid, where secondary reactions are enhanced and the global heat of reaction shifts to exothermic. Furthermore, when it is coupled to a particle model, it correctly describes single particle pyrolysis experiments conducted with beech spheres where there is a remarkably exothermic peak in the centre temperature.

FLASHCHAIN Theory for Rapid Coal Devolatilization Kinetics. 8. Modeling the Release of Sulfur Species from Various Coals

This modeling study expands FLASHCHAIN theory to interpret the release rates and yields of H2S, COS, and SO2 and the sulfur contents of tar and char from any coal and thereby completes the theoretical framework for the devolatilization of all five major organic elements in any coal. The proposed reaction set accurately interprets a database that represents heating rates from 10 to almost 104 °C/s, temperatures to 1500 °C, contact times to 7 min, and S product distributions from 27 different coal samples representing ranks from lignites to anthracites, albeit with persistent uncertainties on the split between tar S and noncondensable S products. A single distributed-energy reaction with the same parameters for all coals accurately describes the release of H2S from pyrite during primary devolatilization. Additional kinetic rate data on sulfate decomposition under rapid heating is needed to close the analysis for inorganic S species. By associating aliphatic and aromatic sulfide functional groups with labile...

Temperature influence on the fast pyrolysis of manure samples: char, bio-oil and gases production

Fast pyrolysis characterization of three dry manure samples was studied using a pyrolyzer. A heating rate of 600°C/s and a holding time of 10 s were selected to reproduce industrial conditions. The effect of the peak pyrolysis temperature (600, 800 and 1000°C) on the pyrolysis product yield and composition was evaluated. Char and bio-oil were gravimetrically quantified. Scanning electron microscopy (SEM) was used to analyse the char structure. H 2 , CH 4 , CO and CO 2 were measured by means of gas chromatography (GC). A decrease in the char yield and an increase of the gas yield were observed when temperature increased. From 800°C on, it was observed that the char yield of samples Dig R and SW were constant, which indicated that the primary devolatilization reactions stopped. This fact was also corroborated by GC analysis. The bio-oil yield slightly increased with temperature, showing a maximum of 20.7 and 27.8 wt.% for samples Pre and SW, respectively, whereas sample Dig R showed a maximum yield of 16.5 wt.% at 800°C. CO 2 and CO were the main released gases whereas H 2 and CH 4 production increased with temperature. Finally, an increase of char porosity was observed with temperature.