Pyrolysis Stage Research Articles

Glowing and piloted flaming ignition of vertical wood exposed to power-law thermal radiation

Fire hazards are dangerous to human life and property safety. Fire accidents occur frequently in wood-frame villages all over the world. In this paper, glowing and flaming ignition of vertical wood heated by five power-law heat fluxes (HF) is experimentally studied using a self-built apparatus. Comparative ignition tests with and without piloted ignitor were performed, and some crucial variables were collected, encompassing surface and in-depth temperatures, mass loss rate, and ignition time. A 1D numerical model was developed to simulate experimental results and determine temperature-dependent thermodynamics of wood by inverse modelling. The results showed that ignitor induced flaming ignition, whereas absence of ignitor enabled only glowing ignition. Flaming ignition was preceded by flash ignition. Surface temperatures of flaming ignition were well predicted by numerical model. However, the predictive accuracy declined when modelling in-depth temperatures due to cracks in char layer. Three stages were identified in both ignition modes: a preheating stage, a water evaporation stage, and a pyrolysis stage. The numerical model underestimated mass loss rates due to additional heating contributed by flash ignition and char cracks. Critical temperature and critical mass flux were comparatively analyzed, and the former was used in assessing ignition time. Measured ignition times were well estimated by an analytical correlation. The numerical model accurately predicted flaming ignition times but overpredicted glowing ignition times due to char cracks. The proposed model can contribute to the fire safety retrofitting of historic buildings and minimize human casualties and property damage.

Insights into biomass mild gasification based on mass-energy balance: Establishing condition, thermodynamic mechanisms, and product properties

To alleviate the challenge of gas and char quality competition arising from over oxidation during the biomass gasification. A new concept of biomass mild gasification based on mass and energy balance was proposed, wherein the energy produced during the oxidation stage precisely equals the energy consumed in the pyrolysis and reduction stages. An energy balance index (EBI), obtained through the combined use of TG-DSC-MS-FTIR and Gaussian model fitting to represent the relationship between mass loss and endothermic/exothermic properties among different reaction stages, was optimized by response surface methodology (RSM) to obtain the critical conditions of biomass mild gasification. Under two typical mild gasification conditions, the quality characteristics of mild gasification biochar were analyzed and the gas evolution characteristics and sequence were determined through the combination of two-dimensional correlation spectroscopy (2D COS). The results indicated that mild gasification can be achieved within a heating rate range of 21 °C/min to 26 °C/min, with the oxidation temperature ranging from 776 °C to 869 °C. Under mild gasification conditions, the biochar produced at 850 °C-20 °C/min had higher COOH content, which can regulate soil pH, promote organic matter degradation, and enhance biological activity. Under the 800 °C-25 °C/min mild gasification condition, more CO and CH4 were generated during the pyrolysis stage, but slightly more CO2 was also produced during both the pyrolysis and oxidation stages. This work provides comprehensive thinking on the precious control of gasification process, which lays a foundation for co-generation of high-quality char and gas.

Microwave dielectric characterization and loss mechanism of biowaste during pyrolysis

The effectiveness of microwave heating of biomass depends on the changes in dielectric properties. This study systematically investigated the microwave dielectric properties and loss mechanism of biowaste at different frequencies (915 and 2,450 MHz) and temperatures (25–800 °C) using the cavity perturbation method. The gas emissions and properties of the biochar produced during pyrolysis were characterised by SEM, XRD, and TG-FTIR. The findings revealed that the dielectric properties and penetration depth of the biomass and biochar changed significantly during microwave pyrolysis. The dielectric constant and dielectric loss coefficient first increased and then decreased during the drying stage, and they decreased continuously with the volatile’s generation in the pyrolysis stage, while the formation and high conductivity of biochar promoted a sharp increase in dielectric properties during the carbonisation stage. The loss tangent angle is 0.01–0.05 in the first two stages, while it increased to 0.10–0.25 in the carbonization stage, demonstrated that the biowaste is a low-loss material. However, the microwave absorption capacity was enhanced for pyrolyzed biochar. The loss mechanism revealed that dipole polarisation primarily contributes to the dielectric loss during the drying and pyrolysis stages, whereas interfacial polarisation plays an important role during the carbonisation stage. The data provided in this paper contribute to the evaluation of microwave penetration depth in biomass and the design of large-scale microwave-based heating systems. Furthermore, this study offers a theoretical basis for modelling and simulating the microwave heating of biomass and achieving efficient energy conversion.

Experimental investigation of the influence of calcium oxide on product quality, tar cracking efficiency, heating value, and syngas ratio in two-stage fixed bed gasification

ABSTRACT Biomass gasification is a thermochemical process used to generate hydrogen and methane for energy applications. This experimental study compares the products formed from sugarcane bagasse, bamboo, and rice-straw and evaluates the calorific value of the gas and the efficiency of homogeneous cracking in a novel, two-stage, downdraft, fixed-bed reactor. The formation of tar and the presence of carbon oxides (COx) in the gaseous product are some of the major problems with biomass gasification. In order to solve these issues, calcium oxide (CaO) is introduced with the feed in a 1:1 mass ratio as a CO2 sorbent, and its effect on the amount of tar is studied across the chosen biomasses. Experiments are conducted with the pyrolysis stage at 773 K and the air-gasification stage at 1073 K. The tar cracking efficiency of 97% is obtained with CaO for all biomasses. Rice-straw showed the highest syngas ratio of 1.83 and the volume of hydrogen increased by 13% after the addition of CaO, while bamboo had a 16% rise in hydrogen and showed the highest LHV of 12.21 MJ/m3, followed by bagasse with an LHV of 11.50 MJ/m3. The gasification efficiency for bamboo is the highest overall for both the processes.

Application of Simultaneous and Coupled Thermal Analysis Techniques in Studies on the Melting Process, Course of Pyrolysis and Oxidative Decomposition of Fused Triazinylacetohydrazides.

The effect of the structure of promising antioxidant agents with prospective medical use, i.e., unsubstituted and para-substituted annelated triazinylacetic acid hydrazides, on their melting points, thermal stabilities, pyrolysis and oxidative decomposition stages and the type of volatiles emitted under heating with the use of DSC and TG/DTG/FTIR/QMS methods was evaluated and discussed. The melting point of the investigated compounds increased with an enhanced number of electrons (directly correlated with their molecular weight). Melting enthalpy values were determined and presented for all the studied compounds. The pyrolysis and oxidative decomposition processes of the analysed molecules consisted of several poorly separated stages, which indicated a multi-step course of the decomposition reactions. It was found that the thermal stability of the tested compounds depended on the type of substituent at the para position of the phenyl moiety or its absence. In both atmospheres used (air and helium), the thermal stability increased in relation to R as follows: -CH3 ≤ -OCH3 < -H < -OC2H5. In an inert atmosphere, it was higher by approx. 8-18 °C than in an oxidative atmosphere. The pyrolysis was connected with the emission of NH3, HCN, HNCO, HCONH2, HCHO, CO2, CO and H2O in the case of all the tested compounds, regardless of the substituent attached. In the case of the derivative containing the para-CH3 group, para-toluidine was an additional emitted aromatic product. In turn, emissions of aniline and alcohol (methanol or ethanol) for compounds with the para-OCH3 and para-OC2H5 groups, respectively, were confirmed. In oxidative conditions, the release of NH3, NO, HCN, HNCO, HCONH2, CO2, H2O and cyanogen (for all the compounds) and para-toluidine (for the para-CH3 derivative), aniline (for para-OCH3, para-OC2H5 and unsubstituted derivatives) and acetaldehyde (for the para-OC2H5 derivative) were clearly observed. No alcohol emissions were recorded for either compound containing the para-OCH3- or para-OC2H5-substitututed phenyl ring. These results confirmed that the pyrolysis and oxidative decomposition of the investigated annelated triazinylacetohydrazides occurred according to the radical mechanism. Moreover, in the presence of oxygen, the reactions of volatiles and residues with oxygen (oxidation) and the combustion process additionally proceeded.

Iron powder in-situ catalytic pyrolysis on coated wooden board: Kinetic, products, and recovery

Catalytic pyrolysis is a promising method for the resource utilization of wooden waste, and in-situ catalysis enhances the process and reduces treatment costs. The selection of catalysts is crucial, as their catalytic effect and service life directly impact treatment effectiveness and economic benefits. In this study, iron powder was utilized to examine its potential in in-situ catalytic pyrolysis of coated wooden boards. The results showed that some of the iron powder could compete for oxygen from lignin/ hemicellulose during the early pyrolysis stage, resulting in the formation of FeO and a decrease in CO2. The formed FeO then promoted cellulose decomposition, reducing the pyrolysis activation energy by 26% ∼ 48%. Despite the addition of iron powder, no obvious impact was observed on the distribution of product yields. However, there are differences in the specific composition: the gas products showed a decrease of CO2 by 26% and CH4 by 13%, while the bio-oil showed an increase of phenol by 8%. This revealed that the iron powder primarily changed the energy barrier of the pyrolysis reaction. There was magnetic separation followed by particle size screening for the recovery of solid products. After separation, the recovery rate of iron powder was determined to be only 65.39%. Two kinds of char particles appeared in the separated products: magnetic (M3) and non-magnetic (NM). Approximately 44.45% of total Fe (from Fe powder and coating materials) contents and 73.62% of total Ti (main metal in the primary coating) were found in M3, while only 1.32% and 10.90% in NM, respectively. Interestingly, the distribution of elements Zn, Ba, and Mg was found to be opposite to that of Fe, which mainly distributed in NM and M2. It might be attributed to the primary coating on the M3 surface, which likely to help facilitated the adsorption of iron particles according to the combination of SEM/EDS and ICP-MS results. The adsorption competition effect of Fe and other metals resulted in significant differences in the distribution of metals on several char particles.

Karakteristik Kimia Dan Organoleptik Asap Cair Tempurung Kelapa Dalam Menurunkan Cemaran Logam Timbal (Pb) Pada Ikan Cakalang (Katsuwonus pelamis)

This research aims to determine the chemical characteristics of coconut shell liquid smoke and analyze the effectiveness of using liquid smoke in reducing Pb metal contamination in skipjack tuna (Katsuwonus Pelamis). Grade 2 liquid smoke from coconut shells is produced by the Pulubala IKM center through the stages of pyrolysis and distillation. This study employs a completely randomized design (CRD) with two replications. To determine the chemical characteristics of the liquid smoke, the analyzed methods include pH measurement, phenol content, total acidity, protein content, organoleptic value, and the chelating power of heavy metal Pb with variations in the concentration of liquid smoke test solutions AC (undiluted liquid smoke), AC2, AC4, AC6, and AC10 (liquid smoke with the addition of distilled water at 2%, 4%, 6%, and 10%). The results show that the best treatment is obtained from coconut shell liquid smoke with AC concentration (undiluted liquid smoke) having the best characteristics, namely a pH value of 4, phenol content of 1.6469%, total acidity of 14.94 mg/mL, protein content of 0.6083%, and a chelating power for heavy metal Pb of 97.32%. The results of the organoleptic test indicate that overall, the highest score was obtained with a neutral value at the concentration of AC2 (liquid smoke with the addition of 2% distilled water).

Research on fire early warning index system of coal mine goaf based on multi-parameter fusion

In order to improve the precision of goaf fire early warning outcomes, this paper obtains the temperature characteristic index of goaf fire early warning by using a coal spontaneous combustion thermogravimetric test and a coal spontaneous combustion programmed heating test. The major gas index and auxiliary gas index for early warning are derived using the integration of the Graham coefficient and grey correlation approach. The D-S evidence theory, which involves optimizing weight allocation, is utilized to integrate the early warning temperature index and various gas indexes. Based on the fusion results, a coal mine goaf fire early warning index system is developed through multi-parameter fusion. The early warning index system is then validated through a programmed heating experiment. The results show that the process of coal spontaneous combustion can be categorized into six distinct stages: latent stage, oxidation stage, critical stage, pyrolysis stage, fission stage, and combustion stage. These stages are determined by the characteristic temperatures of coal spontaneous combustion, which are 31.7 °C, 54.8 °C, 153.7 °C, 204.5 °C, and 241.6 °C. The major gas index for early warning of goaf fires can be determined by 100∆(CO)/∆O2(%). Additionally, auxiliary gas indexes such as C3H8/CH4, C3H8/C2H6, C2H4/C2H6, and C2H2 can be used for goaf fire early warning. The programmed heating experiment shows that the early warning system software is designed by the multi-parameter fusion goaf fire early warning index system is accurate and effective. The selection of the goaf fire early warning index is more rational and precise when using the multi-parameter fusion goaf fire early warning index system based on the D-S evidence theory of weight allocation. It offers robust support for enhancing the goaf fire early warning index system and predicting coal mine goaf fires.

Compact and accurate chemical mechanism for methane pyrolysis with PAH growth

A reliable and compact chemical mechanism of gas-phase methane pyrolysis leading to formation of large polycyclic aromatic hydrocarbon (PAH) molecules has been developed. This model is designed for studies of carbon nanostructure synthesis such as carbon black and graphene flakes, including soot growth kinetics. Methane pyrolysis with carbon nanostructure synthesis is a two-stage process where conversion of CH4 to C2H2 precedes the growth of PAH molecules from acetylene. We present a single chemical mechanism that accurately describes both stages. We have constructed a compact and accurate chemical mechanism capable of modeling both stages of methane pyrolysis based on the ABF [1] mechanism which was expanded with the most prominent reaction pathways from the mechanism by Tao [2] for small PAH molecules and HACA pathways for larger PAH molecules, up to 37 aromatic rings. The resulting mechanism was validated through comparison to multiple available sets of experimental data. Good agreement with the experimental data for both processes was obtained. Performance of the mechanism was tested for pyrolysis of methane-rich mixtures under long residence times leading to abundant formation of PAH molecules. It is shown that the inclusion of larger PAH species (up to A37) in the chemical mechanism is important for accurate prediction of the fraction of carbon converted to PAH molecules and, correspondingly, the residual fraction of acetylene in the mixture. The mechanism file is available upon request.

Exploitation and Utilization of Generated Oil and Gas by Pyrolysis Simulation Modeling of Shale Source Rocks under the Condition of In Situ Conversion

Previous studies have mainly focused on the source rocks of the 7th Member of Yanchang Formation (Chang 7 Member) in the Ordos Basin, with very few studies focusing on the extracts from the source rocks. These extracts have important guiding significance for studying the in situ conversion process of shale oil. Taking the shale source rock of the Chang 7 Member as an example, this paper selected the extract of shale source rock (i.e., retained oil), which has been less studied previously, as the sample to carry out the hydrocarbon-generating pyrolysis simulation experiment of a semi-open–semi-closed system. Seven groups of parallel simulation experiments were designed with a pressure of 20 MPa. The generated oil and gas were collected and quantified, and their geochemical characteristics were researched. In addition, the generated oil and gas were investigated from aspects of cumulative yield and net increased yield, and the chromatographic and mass spectral characteristics of the generated oil were also researched. Based on this, an inductive hydrocarbon generation model of retained oil in shale source rocks was established: slow hydrocarbon generation stage (300–320 °C), rapid hydrocarbon generation stage (320–360 °C), and residual oil pyrolysis stage (0.79%Ro–1.47%Ro). This study is of important significance to guide the research on the in situ conversion process of shale source rock.

Role of iron oxide in retarding the graphitization of de-oiled asphaltenes for amorphous carbon.

The solvent deasphalting (SDA) process is widely recognized as a significant technology in processing inferior oil. However, de-oiled asphaltene (DOA), which accounts for about 30% of feedstocks, is not well utilized in conventional processing methods to date. Considering its complicated structure and high heteroatom and metal contents, DOA is suitable for preparing amorphous carbon. Herein, we obtained amorphous carbon from inferior de-oiled asphaltene through direct carbonization of a mixture of DOA and Fe2O3 and revealed the mechanism of iron oxide in retarding graphitization to increase the disordered structure content. After the addition of Fe2O3, XRD results showed that the content of amorphous carbon increased from 25.57% to 59.48%, and a higher defect degree could also be observed in Raman spectra, thus resulting in better electrochemical performance in Na-ion half-cells. As a coke core, Fe2O3 could accelerate the polycondensation of asphaltene molecules; meanwhile, oxygen species derived from Fe2O3 could capture excess H free radicals in the initial pyrolysis stage, which inhibited the formation of planar polycyclic aromatic molecules and weakened π-π interactions. Moreover, O atoms could embed into the carbon skeleton by reacting with DOA at higher temperatures, which could further twist and break the intact carbon layer. Both of the factors enhanced the proportion of amorphous carbon. This work not only provides a new understanding of controlling the carbonization process, but it also promotes the development of the SDA process.

Effects of nano-Al2O3 dosage on pyrolysis kinetics and formation of hydration products in tailings wet shotcrete

The use of tailings as aggregate for the preparation of wet shotcrete is one of the most important technical approaches to the sustainable development of mines. In this study, the pyrolysis kinetics of tailings wet shotcrete with different Nano-Al2O3(NA) dosage and the formation mechanism of hydration products are carried out based on the theory of pyrolysis kinetics and various micro characterization methods. The findings show that 1% NA dosage(NA1) specimen significantly improves uniaxial compressive strength by 48.72% and 34.69% compared to NA0 and NA2, respectively. Pyrolysis of concrete has 3 stages: dehydration of ettringite(AFt) and calcium silicate hydrate(C-S-H), dehydroxylation of calcium hydroxide(CH), and CO2 release from calcium carbonate decomposition. These stages conform to the S-B model. The average apparent activation energy for NA1 specimen during the first pyrolysis stage is 114.01 kJ/mol, indicating an increased energy barrier for the pyrolysis of hydration product, which diminishes when NA dosage exceeds 1%. Furthermore, NA1 specimen exhibits enhanced kinetic parameters, including a notable increase in the preexponential factor during the first pyrolysis stage. This suggests higher activation and effective collision of molecules, leading to optimal AFt and C-S-H formation at 1% NA dosage. Microscopic and thermal analyses reveal that NA aids TWSC hydration through gap filling, nucleation, bond-breaking recombination on tailings surfaces, and calcium (alumino) silicate hydrate(C-(A)-S-H) formation. This process augments hydration product generation, decreases microstructural porosity, and enhances macroscopic strength. However, exceeding 1% NA dosage inversely affects these properties, highlighting an optimal NA concentration for maximizing TWSC performance.

The migration behavior of cesium during plasma gasification melting process of spent radioactive resins by thermodynamic calculation

Plasma gasification melting is an effective method of spent radioactive resin disposal. However, the equilibrium distribution and migration of Cs during the plasma gasification melting process is still unclear. In this study, the volatilization behavior of Cs during the plasma gasification melting process of spent resins was investigated by thermodynamic model. The composition of the stable phase and the release of Cs from the stable phase in the three systems of Cs-C-O, Cs-S-O and Cs-N-O were calculated by HSC Chemistry. The possible composition of Cs during the plasma gasification melting process of spent resins was determined. At the same time, the thermodynamic simulation of spent resins in the temperature range of 300–1800 °C was carried out, and the morphological distribution of Cs during the plasma gasification melting process of spent resins was calculated and analyzed, which will provide theoretical guidance for subsequent experimental research. The results showed that Cs2CO3, Cs2SO4 and Cs2O were identified as the stable phases of each system at 1200 °C in air atmosphere. The existent forms of Cs in the three stages of plasma pyrolysis, gasification and melting are different. In the plasma pyrolysis and melting stage, Cs mainly enters the gas phase in the form of gaseous Cs and CsOH. In the plasma gasification stage, Cs mainly enters the gas phase in the form of gaseous Cs and Cs2SO4. By comparing with the results of some literature, the accuracy of thermodynamic calculation is proved. The migration and transformation law of Cs during the plasma gasification melting process of spent radioactive resins is revealed.

In-depth understanding of the microscopic mechanism of biochar carbonaceous structures during thermochemical conversion: Pyrolysis, combustion and gasification

The thermochemical utilization of biomass char is vital for addressing environmental pollution and the energy crisis. The carbonaceous structure plays a crucial role in this process, and understanding the conversion mechanism aids in optimizing biomass reactors. This study performs a comprehensive analysis of high-temperature rice husk char using 13C NMR, XPS, and FTIR techniques. The carbonaceous structure is classified based on carbon bonding modes and the forms of O and N. The reaction mechanisms of thermochemical transformations under various atmospheres (N2, O2, CO2, H2O) are investigated using ReaxFF-MD. The reaction characteristics are determined, and the reaction activities are compared. The results indicate that the nitrogen-containing heterocycles remain in pyridine-type pyrolysis products under the N2 atmosphere (pyrolysis). Repolymerization occurs in the initial stages of pyrolysis, with the size of aromatic rings affecting the formation of heavy components. Under the O2 atmosphere (combustion), the degree of complete carbon oxidation is linked to the number of aromatic rings. The reactivity of aliphatic carbonaceous structures depends on the hydrogen content. Under the CO2 atmosphere (gasification), the pyrrole-type structure exhibits the highest gasification activity. Aromatic structures with oxygen functional groups are more susceptible to reacting with CO2, indicating higher sensitivity. Aliphatic H atoms tend to be oxidized into H2O. Under the H2O atmosphere (gasification), hydrogen in the gasification of aromatic carbon primarily originates from H at the aromatic boundary. In N2 and CO2 atmospheres, the CO bridge bond breaks first, followed by reactions. In H2O gasification, the breaking of bridge bonds connected to aliphatic carbon occurs simultaneously with gasification. Each reaction system's product distribution and elemental migration processes are also determined. The findings provide valuable theoretical insights into the application of biomass char.

Features of the pyrolysis process of waste batteries using carbon black as an additive in the construction industry

The paper discusses the technology for recycling used lithium-ion batteries. At the same time, one of the important components in the technology for processing such waste is the recycling of anode material with the extraction of graphite or carbon black, which can be used in the production of fire bricks. It has been shown that materials and compounds contained in lithium-ion batteries are sources of hazardous waste of the second hazard class. At the same time spent accumulators are a source of valuable secondary material resources and contain in their composition up to 16 % wt. % of graphite.The paper proposes to consider the process of processing anode materials of lithium-ion batteries in order to obtain graphite and carbon black from them by pyrolysis. Experimental studies were carried out on the process of decomposition of cathode and anode materials of lithium-ion batteries separately, as well as their mixture by pyrolysis. When studying the kinetics and mechanism of pyrolysis of carbon-containing materials, thermogravimetric analysis of the following materials was carried out: 1) powdered graphite grade GAK-2 (GOST 10273-79); 2) graphite released from the anode during manual disassembly of the LKIT; 3) mechanically activated powders containing cathode material LiNiMnCoO2. The characteristics of the pyrolysis process were assessed using thermogravimetric and differential thermogravimetric analyses. Pyrolysis characteristics demonstrate that organic substances contained in batteries can decompose at a pyrolysis temperature of 500 °C for cathode materials and 450 °C for anode materials. This subsequently leads to higher efficiency in the extraction of valuable components with shorter grinding times. It has been shown that the decomposition of a mixture of lithium-ion battery materials removes a larger amount of organic components than the pyrolysis of anode and cathode materials separately. In this case, the rate of decomposition of the mixture of materials occurs more slowly. The activation energy values for lithium-ion battery materials after the pyrolysis stage were determined. The content of components in powder obtained after the pyrolysis stage was determined using the method of atomic emission spectrometry with inductively coupled plasma.

Influence mechanism of K on cellulose pyrolysis by stepwise isothermal method in-situ DRIFTS method

The influence mechanism of alkali metal potassium (K) on cellulose pyrolysis is a vague and fundamental key topic in the field of biomass thermal conversion. In this study, the pyrolysis of cellulose and K-impregnated cellulose was compared by in-situ DRIFTS (Diffused Reflectance Infrared Fourier Transform Spectroscopy) and TG (Thermal Gravimetric)–MS (Mass Spectrum) experiment, and quantum chemical calculations were used to verify the peak position and pyrolysis mechanism of infrared (IR) spectroscopy. Stepwise isothermal in-situ DRIFTS was designed to study the reaction path at high temperatures. It was found that in the early stage of pyrolysis, K accelerated the activation of cellulose by attacking the hydrogen bond (H-bond) in the crystal structure of cellulose, increased the dehydration rate between molecules, and promoted the decomposition of cellulose. Simultaneously, it weakened the epoxy–ether bond, inhibited the formation of dehydrated sugar, and promoted the formation of furan. Subsequently, K combined with carbonyl groups to form C–O–K structures, which improved the thermal stability of certain oxygen-containing functional groups such as carbonyls/aldehydes, so that these structures were retained until higher temperature. K promoted the conversion of dehydrated sugars to straight-chain ketones/aldehydes, which led to an increase in carbon conversion. During the coke generation stage, K promoted the formation of disordered carbon and residues, thereby inhibiting coke aromatization. The isothermal in-situ DRIFTS method proposed in this study was demonstrated to better inhibit the high temperature drift of IR spectrum during pyrolysis. It clarified the conversion between functional groups at high temperatures, which is expected to promote the development of other high-temperature pyrolysis mechanism.

Pyrolysis and combustion characteristics of typical sealing materials for exterior building windows

Seals play a crucial role in preventing flame penetration through building exterior windows. However, as urban renewal accelerates, the number of discarded seals is also gradually increasing, which is not in line with the concept of green, energy-saving sustainable development. To gain a better understanding of the pyrolysis and combustion characteristics of sealing strips and facilitate their effective resource utilization and conversion into value-added fuels, we employed thermogravimetry, cone calorimetry, and flue gas spreading test equipment. Typical sealing and filling materials used for external windows of buildings, including EPDM ordinary adhesive strips (EPDM-O), EPDM flame-retardant adhesive strips (EPDM-R), as well as 20-fold expanding graphite strips and 30-fold expanding graphite strips (EG-20 and EG-30), were investigated. Comprehensive evaluations of their pyrolysis behaviors, kinetic parameters, and combustion characteristic parameters were carried out. The results showed that EPDM exhibits good thermal stability, while EG had better demonstrates favorable pyrolysis properties and expansion densification. Average activation energies of EPDM-O and EPDM-R in the combustion phase were 68.35 kJmol−1 and 92.40 kJmol−1, respectively. Moreover, the average activation energies of EG-20 and EG-30 in the expanding combustion phase were 67.42 kJ·mol−1 and 68.62 kJ·mol−1, respectively. The reaction rate of combustion stage is faster than that of pyrolysis stage. Furthermore, For the combustion, the flame growth index (FGI) of EPDM is greater than that of EG, whereas the flame spread index (FPI) is lower than EG. When EPDM burns, the flame spreads rapidly, while EG expands and generates a large number of wormlike substances, effectively preventing the high temperature from spreading to the interior of the material. Analyses of smoke spreading tests have shown that both EPDM and EG can produce irritating flammable fumes at high temperatures, affecting the environment. These results provide a basis for the development of new materials and contributes to fire safety, smoke management, and personnel escape planning.

A thermogravimetric assessment of eco-friendly biochar from oxidative torrefaction of spent coffee grounds: Combustion behavior, kinetic parameters, and potential emissions

This study investigated how temperature and residence time variations impact the combustion behavior, kinetic, and potential emissions of biochar produced through oxidative torrefaction of spent coffee grounds (SCG). The study examined the characteristics of combustion and kinetics by conducting thermogravimetry analysis under heating rates of 10 °C·min−1. The Coats-Redfern model was utilized to calculate kinetic parameters. While the emission indices were approximated using the data obtained from elemental analysis. The results indicated that biochar's comprehensive combustion index (Cci) from oxidative torrefaction was lower than that of raw SCG, suggesting stable combustion behavior. Moreover, with the escalation of torrefaction intensity, the activation energy (Ea) values exhibited an upward trend for the char combustion stage, ranging from 22.08 kJ mol−1 to 38.46 kJ mol−1. Concurrently, the Ea values pertaining to the oxidative pyrolysis stage decreased from 64.26 kJ mol−1 to 52.65 kJ mol−1. Besides, this study emphasized that the ash content of the biochar was lower than that of coal and remained consistent with the ash content of raw SCG (p > 0.05). Moreover, the study revealed that biochar from oxidative torrefaction emitted less CO2 (67.35 g MJ−1) than lignite coal (76.55 g MJ−1). Additionally, biochar exhibited up to 27 times lower dust emissions than bituminous coal, emphasizing its eco-friendly fuel potential.

Three-stage pyrolysis–steam reforming–water gas shift processing of household, commercial and industrial waste plastics for hydrogen production

Five common single plastics and nine different household, commercial and industrial waste plastics were processed using a three-stage (i) pyrolysis, (ii) catalytic steam reforming and (iii) water gas shift reaction system to produce hydrogen. Pyrolysis of plastics produces a range of different hydrocarbon species which are subsequently catalytically steam reformed to produce H2 and CO and then undergo water gas shift reaction to produce further H2. The process mimics the commercial process for hydrogen production from natural gas. Processing of the single polyalkene plastics (high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP)) produced similar H2 yields between 115 mmol and 120 mmol per gram plastic. Even though PS produced an aromatic product slate from the pyrolysis stage, further stages of reforming and water gas shift reaction produced a gas yield and composition similar to that of the polyalkene plastics (115 mmol H2 per gram plastic). PET gave significantly lower H2 yield (41 mmol per gram plastic) due to the formation of mainly CO, CO2 and organic acids from the pyrolysis stage which were not conducive to further reforming and water gas shift reaction. A mixture of the single plastics typical of that found in municipal solid waste produced a H2 yield of 102 mmol per gram plastic. Knowing the gas yields and composition from the single plastics enabled an estimation of the yields from a simulated waste plastic mixture and a ‘real-world’ waste plastic mixture to be determined. The different household, commercial and industrial waste plastic mixtures produced H2 yields between 70 mmol and 107 mmol per gram plastic. The H2 yield and gas composition from the single waste plastics gave an indication of the type of plastics in the mixed waste plastic samples.Graphical abstract

Pyrolysis of Solid Recovered Fuel Using Fixed and Fluidized Bed Reactors

Currently, most plastic waste stems from packaging materials, with a large proportion of this waste either discarded by incineration or used to derive fuel. Accordingly, there is growing interest in the use of pyrolysis to chemically recycle non-recyclable (i.e., via mechanical means) plastic waste into petrochemical feedstock. This comparative study compared pyrolysis characteristics of two types of reactors, namely fixed and fluidized bed reactors. Kinetic analysis for pyrolysis of SRF was also performed. Based on the kinetic analysis of the pyrolytic reactions using differential and integral methods applied to the TGA results, it was seen that the activation energy was lower in the initial stage of pyrolysis. This trend can be mainly attributed to the initial decomposition of PP components, which was subsequently followed by the decomposition of PE. From the kinetic analysis, the activation energy corresponding to the rate of pyrolysis reaction conversion was obtained. In conclusion, pyrolysis carried out using the fluidized bed reactor resulted in a more active decomposition of SRF. The relatively superior performance of this reactor can be attributed to the increased mass and heat transfer effects caused by fluidizing gases, which result in greater gas yields. Regarding the characteristics of liquid products generated during pyrolysis, it was seen that the hydrogen content in the liquid products obtained from the fluidized bed reactor decreased, leading to the formation of oils with higher molecular weights and higher C/H ratios, because the pyrolysis of SRF in the fluidized bed reactor progressed more rapidly than that in the fixed bed reactor.