Anaerobic Pyrolysis Research Articles

Thermal processing of plastic wastes for fuel

Plastic wastes rise annually as a result of the growing demand for synthetic materials, which contributes to their manufacture. There are four main ways to recycle waste polymer, with thermal treatment for fuel being the most favorable to the environment. In this study, the thermal processing of plastic wastes was investigated with an anaerobic pyrolysis apparatus, and their thermal degradation was evaluated by using the thermogravimetric apparatus.Additionally, the elemental composition was determined by an elemental analyzer, n-alkanes were identified by gas chromatography with flame ionization detection/electron capture detector (GC-FID/ECD), and the hydrocarbons functional group was analyzed by Fourier transform infrared spectroscopy (FTIR). We pyrolyzed the most widely utilized polymers, including polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), at temperatures as elevated as 500°C to obtain plastic pyrolysis oil (PPO). Then PPO was distilled into initial boiling point (IBP)-200°C (gasoline-like fuel), 200-350°C (diesel-like fuel), and over 350°C fraction (residue), and the technical features of each fraction were compared to the MNS 0217:2006 and MNS 6861:2020 standards. Diesel-like fuel (DLF) derived from LDPE consists of the n-alkane hydrocarbons with C8–C23 identified by flame ionization detection (FID) data; C10–C17 represented more than 80% of them.The hydrotreatment results revealed that the diesel-like fraction's nitrogen (N) and sulfur (S) amounts could have reduced from 0.06% to 0.01% and from 0.78% to 0.29%, respectively. In conclusion, it could be done to generate a product with a more stable hydrocarbon content from plastic wastes for fuel.

Effect of different production methods on physicochemical properties and adsorption capacities of biochar from sewage sludge and kitchen waste: Mechanism and correlation analysis

Different pyrolysis methods, parameters and feedstocks result in biochars with different properties, structures and removal capacities for heavy metals. However, the role of each property on adsorption capacity and corresponding causal relationships remain unclear. Here, we investigated various physicochemical properties of biochar produced via three different methods and two different feedstocks to clarify influences of biomass sources and pyrolysis processes on biochar properties and its heavy metal adsorption performance. Experimental results showed biochars were more aromatic and contained more functional groups after hydrothermal carbonization, while they had developed pores and higher surface areas produced by anaerobic pyrolysis. The inclusion of oxygen resulted in more complete carbonization and higher CEC biochar. Different biochar properties resulted in different adsorption capacities. Biochar produced by aerobic calcination showed higher adsorption efficiency for Cu and Pb. Correlation analysis proved that pH, cation exchange capacity and degree of carbonization positively affected adsorption, while organic matter content and aromaticity were unfavorable for adsorption. Microstructure and components determined biochar macroscopic properties and ultimate adsorption efficiency for metal ions. This study identifies the degree of correlation and pathways of each property on adsorption, which provides guidance for targeted modification of biochar to enhance its performance in heavy metal removal.

From the laboratory to the field: Chemical analysis of colored smoke pyrotechnic formulations via mass spectrometry techniques.

Smoke dyes are complex molecular systems that have the potential to form many molecular derivatives and fragments when deployed. The chemical analysis of smoke samples is challenging due to the adiabatic temperature of the pyrotechnic combustion and the molecular complexity of the physically dispersed reaction products. Presented here is the characterization of the reaction byproducts of a simulant Mk124 smoke signal on a multigram scale, which contain the dye disperse red 9 (1-(methylamino)anthraquinone), by ambient ionization mass spectrometry. Our previous work has examined the thermal decomposition of a simplified smoke system consisting of disperse red 9, potassium chlorate, and sucrose by anaerobic pyrolysis gas chromatography mass spectrometry performed at the laboratory milligram scale. The results from the lab scale test were compared with a fully functioned Mk124 in the field. To achieve this, Mk124 smokes were functioned in the presence of sampling swabs that collected byproduct residues from the smoke plume in the ambient environment. These swabs were then analyzed using ambient ionization mass spectrometry to identify the expended pyrotechnic residues, with particular interest in halogenated species. Previous work determined the toxicity of unforeseen byproducts identified on the laboratory scale, which were also detected in the field demonstrating the correlation of the laboratory testing to the fielded systems. By understanding the chemical composition of smokes and their reaction products, potential toxicity effects can be easily assessed, leading to safer formulations with improved performance. These results can help assess how smoke byproducts may impact Warfighter performance, personnel health, and the environment.

One-pot interpenetrating epoxy thermosets from renewable dual biomass to high performance

The 5-hydroxymethylfurfural, honokiol, and magnolol are converted into sustainable epoxy monomers, i.e., 5,5′-(((3′,5-diallyl-[1,1′-biphenyl]-2,4′-diyl)bis(oxy))bis- (methyl-ene))bis(2-((oxiran-2-ylmethoxy)methyl)furan) (MGHF) and 5,5′-(((5,5′-diallyl-[1,1′-biphenyl]-2,2′-diyl)bis(oxy))bis(methylene))bis(2-((oxiran-2-ylmethoxy)- methyl)furan) (MGMF), and they are finally cured by 3,3′-diamino diphenylsulfone (33DDS) and 4,4′-diamino diphenylsulfone (44DDS), thus affording novel interpenetrating polymer networks (IPN). Interestingly, 33DDS induces a twist-stacked structure, whereas 44DDS provides a planar weave matrix. As to the twist-stacked layout MGMF/33DDS, it behaves a superhigh storage modulus (∼5.04 GPa), a high phase transition temperature (Tg, 222.7 °C), and an elevated onset temperature (Td5, 362.8 °C). For planar weave arrays, MGHF/44DDS shows the highest values in Tg (224.9 °C), lap shear strength (∼20.4 MPa), hardness (∼508 MPa), and reduced Young’s modulus (∼6.06 GPa). Furthermore, MGMF/44DDS shows an excellent dielectric property (11.15, 0.02) (∼1 kHz, 25 °C) and a moderate thermal conductivity (0.355 W (m·K)−1) alonging with increased flame retardancy. Besides, those biobased epoxy resin wastes are reclaimable through aerobic or anaerobic pyrolysis. Anaerobic pyrolysis of planar weave networks selectively yields more doped graphene, whereas similar event readily happens to the aerobic pyrolysis of the twist-stacked polymers. In view of these reported advantages, this novel strategy opens new avenues for multifunctional epoxy resins.

Sensitive electrochemical assay of acetaminophen based on 3D-hierarchical mesoporous carbon nanosheets

Acetaminophen plays a key role in first-line Covid-19 cure as a supportive therapy of fever and pain. However, overdose of acetaminophen may give rise to severe adverse events such as acute liver failure in individual. In this work, 3D-hierarchical mesoporous carbon nanosheet (hMCNS) microspheres with superior properties were fabricated using simple and quick strategy and applied for sensitive quantification of acetaminophen in pharmaceutical formulation and rat plasmas after administration. The hMCNS microspheres are prepared via chemical etching of zinc oxide (ZnO) nanoparticles from a zinc-gallic acid precursor composite (Zn-GA) synthesized by high-temperature anaerobic pyrolysis. The obtained hMCNS could enhance analytes accessibility and accelerate proton transfer in the interface, hence increasing the electrochemical performance. Under optimized experimental conditions, the proposed electrochemical sensor achieves a detection limit of 3.5 nM for acetaminophen. The prepared electrochemical sensor has been successfully applied for quantification of acetaminophen in pharmaceutical formulations and the rat plasma samples before and after administration. Meanwhile, this sensor is compared with high-performance liquid chromatography (HPLC) as a reference technology, showing an excellent accuracy. Such an electrochemical sensor has great potential and economic benefits for applications in the fields of pharmaceutical assay and therapeutic drug monitoring (TDM).

Pyrolysis of hydrazine hydrate waste salt: Thermal behaviors and transformation characteristics of organics under aerobic/anaerobic conditions

The production of large quantities of industrial waste salts is becoming an issue of increasing concern with the adoption of the “zero liquid discharge” process for wastewater treatment. Recovery of waste salts as a useful resource after purification provides the best means of solving this problem. In this study, pyrolysis was studied as a purification technique to treat waste salt generated during hydrazine hydrate production (N2H4 WS) within the temperature range of 25–600 °C under aerobic and anaerobic conditions. Aerobic pyrolysis achieved 99.3% organic removal at a temperature that was 50 °C lower than was that achieved by anaerobic pyrolysis (600 °C). The formation of strong fluorescent species at 400 °C during anaerobic pyrolysis was detected using fluorescence excitation emission matrix (FEEM). These species were confirmed to be heterocyclic-N compounds, including pyridinic N and pyrrolic N, that were formed through cyclization reactions, as revealed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric-Fourier transform infrared spectroscopy-mass spectrometry (TG-FTIR-MS). Harmful gases such as HCN and NH3 were released during anaerobic pyrolysis, and this may have been partially associated with the decomposition of heterocyclic-N compounds. Moreover, aerobic pyrolysis effectively reduced CO2 emissions by 8.7% based on energy consumption calculations. Therefore, aerobic pyrolysis is preferable for the purification of N2H4 WS owing to its low decomposition temperature, minimal release of harmful gaseous compounds, and low carbon emissions.

A review of biochar functionalized by thermal air oxidation

Biochar, the product of anaerobic pyrolysis of biomass, has attracted immense interest not only as an adsorbent in agricultural and environmental remediation applications but also as a carbonaceous redox catalyst in air/water purification research. Various chemical approaches have been developed to modify biochar; however, most of them are costly because they require additional chemicals and a series of treatment steps, such as the dewatering the so-treated biochar and post-treatment removal of oxidant products. Recently, researchers, including the author of this article, developed a convenient and inexpensive method for enhancing adsorption of organic and inorganic compounds by subjecting the biochar to a brief thermal air oxidation (AO) step. In this review, the author outlines the basic mechanisms of thermal AO and critically examines the property changes of biochar after the thermal AO treatment. This review aims to improve the understanding of biochar after it is exposed to hot air (e.g., wildfires), provide a detailed discussion of scientific evidence, and offer major directions for future research concerning thermal AO and its applications. A comprehensive review of relevant literature indicates that the important factors governing the resultant biochar after thermal AO include the heat treatment temperature (HTT) at which biochar is made and the feedstocks of biochar. Biochar made from lignin-rich feedstocks such as coconut shells and nutshells is preferable for thermal AO treatment. Thermal reactions between molecular oxygen and biochar (1) improve surface oxygen functionality more effectively for biochar made at HTTs than for high-HTT biochar, (2) increase the surface area and porosity especially for high-HTT biochar; and (3) create new adsorption sites and/or relieve steric restrictions of organic molecules to micropores, thereby enhancing the adsorptivity of biochar.

Highly efficient direct carbon solid oxide fuel cells operated with camellia oleifera biomass

Direct carbon solid oxide fuel cells (DC-SOFCs), energy conversion devices with an all-solid-state structure, utilize solid carbon as a fuel to generate electricity in a green and efficient manner. Recently, the use of biomass-derived carbon as a DC-SOFC fuel has become a key research topic owing to the abundance and renewability of biomass. Thus far, for the majority of studies, an anaerobic pyrolysis process is usually needed for converting the biomass to biochar prior to applying DC-SOFCs. In this study, DC-SOFCs were assembled with perovskite-type La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) and Ag-Gd0.2Ce0.8O2-δ as the electrolyte and electrodes, respectively. The electrochemical performance and stability were evaluated for two types of DC-SOFCs: those filled with Camellia oleifera shell biomass as the fuel and those filled with biochar derived from the biomass. The biomass-filled DC-SOFC achieved a maximum power density of 306 mW cm−2 at 800°C, which is close to that of the biochar-filled DC-SOFC (317 mW cm−2). Moreover, discharge test results of constant current indicate that biomass-filled DC-SOFCs have higher fuel utilization. This study verifies the feasibility and potential of loading biomass directly into DC-SOFCs as a carbon source, and reveals that, compared with DC-SOFCs operated with biochar, biomass-filled DC-SOFCs can deliver remarkable electrochemical performance and stability. Thus, a simpler and more convenient way to generate electricity through efficient and clean utilization of biomass energy is identified.

Palm fatty acid distillate esterification using synthesized heterogeneous sulfonated carbon catalyst from plastic waste: Characterization, catalytic efficacy and stability, and fuel properties

The extensive use of plastics in industries and households contributes to the proliferation of plastic waste (PW) in landfills, the oceans, and the environment, which represents a serious threat to numerous fragile ecosystems. Recycling rates for PW are still low, so solutions to the problem of waste accumulation are urgently needed. We report the transformation of waste polyethylene terephthalate food containers into plastic waste char (PWC) via anaerobic pyrolysis and subsequent conversion to an acidic solid catalyst for conversion of palm fatty acid distillate (PFAD) into biodiesel. Such an approach could provide a promising solution to the environmental issue of PW while simultaneously facilitating production of biofuels. In this study, PW was carbonized at 600 °C to yield a carbon precursor that was subsequently treated with sulfuric acid at three sulfonation ratios (1:10, 1:15 and 1:20) to give a series of solid acid sulfonated carbon catalysts, PWC-SO₃H (a), (b) and (c). The synthesized PWC-SO₃H catalysts were thermally stable up to 375 °C. The deposition of sulfonic acid groups onto the catalytic surface was confirmed by infrared spectroscopy. Surface morphology analysis revealed a mesoporous textural structure with random sulfonate group distribution. Changes in crystallinity for PWC and PWC-SO₃H catalysts were determined by x-ray diffraction spectroscopy and supported by Raman analysis. The catalysts were then evaluated for biodiesel production efficacy via esterification of PFAD with methanol. The PWC-SO₃H (b) catalyst (1:15 impregnation ratio) provided the highest yield of PFAD-derived-biodiesel (96.9%) under the optimum reaction conditions of 5 wt% catalyst at 110 °C for 2 h with a methanol to PFAD molar ratio of 18:1. Recyclability studies revealed that the PWC-SO₃H (b) catalyst was reusable for four consecutive reactions while maintaining high catalytic activity. Lastly, the fuel properties of the resulting PFAD biodiesel were within the limits prescribed in ASTM D6751, the American biodiesel standard.

Silicone-recycled pyrolyzed fillers for enhanced thermal - and flame - resistant silicone elastomers

Two types of fillers were prepared by controlled pyrolysis of a commercial silicone elastomer. An aerobic process led to the formation of a silica powder while an anaerobic pyrolysis generated a silicon-carbon-oxide (SiOC) ceramic. Each filler was incorporated into a silicone gum and thus-prepared obtained formulations were further crosslinked with peroxide to prepare new silicone materials. Silica powder allowed controlling the mechanical properties of the materials whereas enhanced thermal stability was brought by the ceramic; mixing both fillers generated materials with joint properties (tensile strength of about 2 MPa, elongation at break of 300%, onset of degradation at 470 °C). The flame resistance behavior of these silicone materials was tested by cone calorimetry. Early formation of an insulating layer on the heat-exposed surface moderated the heat release (total heat release of 16.4 kJ/gPDMS) and increased final residue (above 50%) compared to commercial silica-filled elastomers. This work opens new possibilities to transform silicone waste into useful inorganic fillers and produce new performant thermal-resistant silicone materials.

Enhancement of Cd(II) adsorption by rice straw biochar through oxidant and acid modifications

To develop high-efficient biochar adsorbents, the effects and mechanisms of oxidant modification and acid modification on Cd(II) adsorption by rice straw biochar were investigated. Three rice straws from Langxi in Anhui Province, Yingtan in Jiangxi Province, and Lianyungang in Jiangsu Province were collected to prepare biochars by anaerobic pyrolysis in a muffle furnace. Rice straw biochars were modified by 15% H2O2 and 1:1 HNO3/H2SO4 mixed acid, respectively, to obtain modified biochars. The untreated rice straw biochar and HCl-treated rice straw biochar with carbonate removed were used as controls. The functional groups on the surfaces of the biochars were qualitatively and quantitatively determined by Fourier transform infrared spectra and Boehm titration, respectively. The adsorption and desorption of Cd(II) onto and from the biochars and modified biochars were measured under various pH conditions. The results showed that oxidant modification with 15% H2O2 and acid modification with 1:1 HNO3/H2SO4 significantly increased the number of carboxyl functional groups on the surfaces of the biochars, and acid modification was more effective than oxidant modification in amplifying carboxyl functional groups on the surfaces of the biochars. The increase of surface functional groups effectively enhanced the specific adsorption of Cd(II) on the modified biochars. Therefore, both oxidant modification and acid modification enhanced the adsorption of Cd(II) on the biochars through increasing functional groups on the surfaces of the biochars.

Investigation of the thermal decomposition mechanism of glycerol: the combination of a theoretical study based on the Minnesota functional and experimental support.

The multiple thermal decomposition channels of glycerol are calculated at the M06-2X-D3/6-311+G(d,p) level. In addition, the CAM-B3LYP and ωB97X-D functionals are used to show the functional influence on the free energy barrier. For the highly competitive primary channels, the DLPNO-CCSD(T)/CBS method is applied for the energy calculations. The results show that the dominant paths are: (1) breakage of the C-C, C-O, and O-H bonds of glycerol successively to form carbonyl and alkene, and then generation of water, formaldehyde, and acetaldehyde; (2) glycerol undergoing an intramolecular dehydration reaction and producing 3-hydroxypropionaldehyde; it has two subsequent reactions: ① C-C bond fracture occurring to form formaldehyde, acetaldehyde, and water; and ② intramolecular dehydration forming acrolein and water. The ΔG1 is 65.6 kcal mol-1 while the ΔG2 is 65.5 kcal mol-1 at 101 kPa and 298 K, and fitted rate equations are 1.09 × 1013 exp[65.6 × 103/RT] s-1 and 8.07 × 1012 exp[65.4 × 103/RT] s-1, respectively. Besides, UPLC and TG-GC/MS are applied complementarily to investigate the anaerobic pyrolysis products of glycerol at different temperatures. The experimental results are consistent with theoretical calculations.

Exploring the Contribution of Two Phosphorus-Based Groups to Polymer Flammability via Pyrolysis-Combustion Flow Calorimetry.

From a set of around 100 phosphorus-containing polymers tested in pyrolysis–combustion flow calorimetry, the contributions to flammability of two phosphorus-containing pendant groups (called 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and PO3) were calculated using an advanced method previously proposed and validated. The flammability properties include total heat release (THR) and heat release capacity (HRC) measured in standard conditions, i.e., anaerobic pyrolysis and complete combustion. The calculated contributions are in good agreement with the main modes of action of both phosphorus groups, i.e., flame inhibition for DOPO and char promotion for PO3. Moreover, the results provide first conclusions about the cooperative interaction between phosphorus and nitrogen, as well as the influence of the architecture of tested co-polymers.

Corncob‐to‐xylose residue (CCXR) derived porous biochar as an excellent adsorbent to remove organic dyes from wastewater

Biochar was prepared from corncob‐to‐xylose residue (CCXR) by KOH activation and anaerobic pyrolysis method. The effect of activation temperature on the microstructure of the biochar was studied. Results showed that the biochar prepared at 850°C (850NBC) possessed high specific surface area and exhibited excellent adsorption property. The maximum adsorption capacity of 2249 mg g−1 was obtained when 850NBC was used for treating methylene blue (MB) solution. Adsorption isotherm fittings revealed that Langmuir and Freundlich models were applicable to 850NBC adsorption process, and the adsorption process was limited by adsorption site and the biochar surface functional groups. Furthermore, 850NBC showed good adsorption property when it was used to treat the other organic dyes of Congo red (751 mg g−1), Orange II (735 mg g−1), Indigo carmine (662 mg g−1) and Methyl Orange (465 mg g−1). Biochar 850NBC also possessed an acceptable recyclability which maintained 68.7% absorption capacity after 6 cycles when it was used to treat MB solution. These results proposed that 850NBC is expected to be a promising potential adsorbent for treating organic dyes waste water.

A novel capacitive electrode based on TiO2-NTs array with carbon embedded for water deionization: Fabrication, characterization and application study

To enhance the structure stability of conventional capacitive deionization (CDI) electrode, this work intends to provide a facile preparation of Titania nanotubes (TiO2-NTs) based electrode with carbon imbedded for capacitive deionization application. The TiO2-NTs array is obtained through anode oxidation method on the titanium substrate, then carbon precursors were induced into the nanochannels of TiO2-NTs carrier by the vacuum pressure and transferred to carbon capacitor through anaerobic pyrolysis process. Such structure possesses a unique combination with hollow carbon fibers as layer binders to fix the upper carbon spheres onto TiO2-NTs substrate. The as-prepared electrode revealed an excellent mechanical stability, electrosorption ability and electroconductibility as well as a favorable hydrophilicity especially after acid modification. This paper also investigates the influence of various operational parameters on the capacitive deionization process, including feed temperatures, flow rates and initial salt concentrations. The electrosorption kinetics is also analyzed within the deionization process, which shows the novel electrode presents a better sorption rate as well as a higher sorption capacity of 13.11±0.58mg/g at 1.2V and 500mg/L feed concentration. Furthermore, the removal principles of CDI electrode under multi-ion circumstance are compared and discussed depending on existing studies.

Preparation and Performance Evaluation of Biochars from Neem Seed Active Substance Extracted Residues (NSASER)

Neem seed active substance extracted residues (NSASER) is industrial by-product, which is often discarded as a waste. It would lead to a certain degree of harm to the environment. The aim of this study was to prepare the biochars with neem seed active substance extracted residues (NSASER) under the anaerobic pyrolysis conditions. The pyrolysis process was studied with different pyrolysis power (200W, 500W, 800W, 1100W and 1400W), and the performance of the prepared biochars was evaluated. The results showed that the required time was to complete the pyrolysis process that gradually decreased with pyrolysis power increased from 200 to 1400 W, and the final pyrolysis temperature was to complete the pyrolysis process that increased with pyrolysis power increased from 200 to 1400 W. The biochars yield decreased with pyrolysis power increased from 200 to 1400 W, and the biochars yield has the maximum value when the pyrolysis power was of 200W. And the prepared biochars still had some characteristics of the plant cell and kept uniform porous structure, which was beneficial to absorb the small molecule substance. The water content of the prepared biochars was 7.18±0.53, the ash content of the prepared biochars was 5.92±0.31 and the fixed carbon content of the prepared biochars was 81.27±0.89. Compared with the bamboo charcoal, the performance index of the prepared biochars was in according with National Standard of the People’s Republic of China GBT26913-2011 of the bamboo charcoal. The prepared biochars had a potential value in application.

Reactivity of the tin homolog of POSS, butylstannoxane dodecamer, in oxygen-induced crosslinking reactions with an organic polymer matrix: Study of long-time behavior

The chemical activity of the heavier POSS homolog, n-butylstannoxane dodecamer cage, in an epoxy matrix containing polopropylene oxide (PPO) chains was studied in detail, especially the long-time development of the effect and its limits in time at different concentrations. A multi-method investigation was carried out, employing spectrometric analysis of chemical composition (NMR, IR), TEM, thermogravimetry, weight loss analysis during isothermal oxidation at 180 °C, as well as dynamic-mechanical thermal analysis (DMTA) of intact and of oxidized epoxy/stannoxane hybrids. The PPO segments of the matrix were found to be preferentially degraded by oxidation or by anaerobic pyrolysis, while at the same time these segments are the sites of crosslinking reactions with stannoxane, which counteract matrix degradation. It was demonstrated, that the cages undergo repeated reactions on the Sn atoms, and remain finely dispersed and well-accessible even after long oxidation times. The repeated reactions also explain the observed very strong stabilizing effect of stannoxane at very low concentrations. Efficient stabilization against the degradation of the mechanical properties was found to require higher – but still very low – concentrations, than the stabilization against weight loss. Interestingly, certain amounts of stannoxane caused simultaneously enhanced weight losses and a mechanical reinforcement due to a higher amount of radical reactions.

Anaerobic Pyrolysis Characteristics of Municipal Solid Waste under High Temperature Heat Source

Abstract This study proposed a new pyrolysis technique for municipal solid waste under anaerobic environment with regenerative radiant tube as the high-temperature heat source within a rotating bed reactor. To obtain the optimum condition of this technique, the effect of heating source temperature, arrangement and bed thickness on the distribution, composition and yield of products was experimentally studied. A three-dimensional transient mathematical model was established to describe the pyrolysis process characterized with simultaneous fluid flow, heat and mass transfer in a rotating bed reactor. The simulation model parameters were also modified based on experimental data. Results showed that this new technique has commercial viability due to the possibility to effectively avoid the problem of tar congestion and obtain high caloricity clean gas.

Spectral Aspects of Bench-Scale Flammability Testing: Application to Hardwood Pyrolysis

The anaerobic pyrolysis of wood material used to palletize commodities is studied in a Fire Propagation Apparatus (FPA) for a range of heating conditions relevant to fires. The data collected, consisting of mass loss rate, cumulative mass loss, and surface temperature, are used to determine model-specific material properties using inverse modeling and optimization methodologies previously developed in our laboratory. However, in this study, considerable effort is placed on determining the radiation environment that characterizes the FPA tests as well as how the radiation interacts with the samples. This is done on the basis of the recognition that boundary conditions have a pronounced effect on the output of a given pyrolysis model and, thus, the optimization results. The spectral radiance from the FPA heaters as well as the absorptivity/emissivity of the material surface are measured herein. The spectral features of the surface indicate that markedly different effective emissivities and absorptivities can be exhibited by the material depending on the spectral distribution of incident radiation. These effects are included in the pyrolysis model used to extract model-specific material properties so that the optimization process can, in a sense, be decoupled from boundary conditions. Therefore, it is expected that the approach described in this study can ensure that the derived model-specific properties can be applied to practical scenarios that are characterized by radiation environments that differ from those in bench-scale test apparatuses such as the FPA.

Cr(VI)/Cr(III) and As(V)/As(III) Ratio Assessments in Jordanian Spent Oil Shale Produced by Aerobic Combustion and Anaerobic Pyrolysis

With the increase in the awareness of the public in the environmental impact of oil shale utilization, it is of interest to reveal the mobility of potentially toxic trace elements in spent oil shale. Therefore, the Cr and As oxidation state in a representative Jordanian oil shale sample from the El-Lajjoun area were investigated upon different lab-scale furnace treatments. The anaerobic pyrolysis was performed in a retort flushed by nitrogen gas at temperatures in between 600 and 800 °C (pyrolytic oil shale, POS). The aerobic combustion was simply performed in porcelain cups heated in a muffle furnace for 4 h at temperatures in between 700 and 1000 °C (burned oil shale, BOS). The high loss-on-ignition in the BOS samples of up to 370 g kg(-1) results from both calcium carbonate and organic carbon degradation. The LOI leads to enrichment in the Cr concentrations from 480 mg kg(-1) in the original oil shale up to 675 mg kg(-1) in the ≥ 850 °C BOS samples. Arsenic concentrations were not much elevated beyond that in the average shale standard (13 mg kg(-1)). Synchrotron-based X-ray absorption near-edge structure (XANES) analysis revealed that within the original oil shale the oxidation states of Cr and As were lower than after its aerobic combustion. Cr(VI) increased from 0% in the untreated or pyrolyzed oil shale up to 60% in the BOS ash combusted at 850 °C, while As(V) increased from 64% in the original oil shale up to 100% in the BOS ash at 700 °C. No Cr was released from original oil shale and POS products by the European compliance leaching test CEN/TC 292 EN 12457-1 (1:2 solid/water ratio, 24 h shaking), whereas leachates from BOS samples showed Cr release in the order of one mmol L(-1). The leachable Cr content is dominated by chromate as revealed by catalytic adsorptive stripping voltammetry (CAdSV) which could cause harmful contamination of surface and groundwater in the semiarid environment of Jordan.