Pyrolysis Gas Composition Research Articles

Manufacturing gaseous products by pyrolysis of microalgal biomass

Algal biomass is considered as an alternative raw material for biofuel production. The search for new types of raw materials including high-energy types of microalgae remains relevant, since the share of motor fuels in the world energy balance remains consistently high (about 35%) with the oil price characterized by high volatility. The authors have considered the advantages of microalgae as raw materials for fuel production. Biochemical and thermochemical conversion are proposed as technologies for their processing. The paper presents the results of the study on the pyrolysis of the biomass of the blue-green microalgae/cyanobacterium Arthrospira platensis rsemsu 1/02-P clonal culture from the collection of the Research Laboratory of Renewable Energy Sources of the Lomonosov Moscow State University. The experimental investigation on the pyrolysis process of microalgal biomass has been carried out with the experimental setup made at the Institute of High Temperatures RAS in pure nitrogen 6.0 to create an oxygen-free medium with a linear heating rate of 10°С/min from room temperature to 1,000°С. The entire pyrolysis process has proceeded in the endothermic region. The specific values for solid residue, pyrolysis liquid and gaseous products have been experimentally determined. The following products have been manufactured by pyrolysis of microalgal biomass weighing 15 g: 1) char with a solid residue mass of 2.68 g, or 17.7% of MAB initial mass (while 9.3% of MAB initial mass has remained in the reactor); 2) pyrolysis liquid with a mass of 3.3 g, or 21.9% of initial mass; 3) noncondensable pyrolysis gases, 1.15 L. The specific volumetric gas yield (amount of gas released from 1 kg of RM) has amounted to 0.076 nm³/kg.In the paper, the analysis of the composition and specific volumetric yield of non-condensable pyrolysis gases produced in the pyrolysis process depending on temperature has been carried out. It is shown that the proportion of high-calorific components of the gas mixture (hydrogen, methane and carbon monoxide) increases with the temperature increase. The heating value assessment for the mixture of these gases has been performed as well.

Prediction of gaseous products from refuse derived fuel pyrolysis using chemical modelling software - Ansys Chemkin-Pro

There can be observed global interest in waste pyrolysis technology due to low costs and availability of raw materials. At the same time, there is a literature gap in forecasting environmental effects of thermal waste treatment installations. In the article was modelled the chemical composition of pyrolysis gas with main focus on the problem in terms of environmental hazards. Not only RDF fuel was analysed, but also selected waste fractions included in its composition. This approach provided comprehensive knowledge about the chemical composition of gaseous pyrolysis products, which is important from the point of view of the heterogeneity of RDF fuel. The main goal of this article was to focus on the utilitarian aspect of the obtained calculation results. Final results can be the basis for estimating ecological effects, both for existing and newly designed installations.Pyrolysis process was modelled using Ansys Chemkin-Pro software. The investigation of the process were carried out for five different temperatures (700, 750, 800, 850 and 900 °C). As an output the mole fraction of H2, H2O, CH4, C2H2,C2H4, C3H6, C3H8, CO, CO2, HCl and H2S were presented. Additionally the reaction pathways for selected material were presented.Based on obtained results, it was established that the residence time did not influenced on the concentration of products, contrary to temperature. The chemical composition of pyrolytic gas is closely related to wastes origin. The application of Chemkin-Pro allowed the calculation of formation for each products at different temperatures and formulation of hypotheses on the reaction pathways involved during pyrolysis process. Further, based on the obtained results confirmed the possibilities of using pyrolysis gas from RDF as a substitute for natural gas in energy consumption sectors. Optimization of the process can be conducted with low financial outlays and reliable results by using calculation tools. Moreover it can be predicted negative impact of obtained products on the future installation.

Investigation of the Composition and Laminar Flame Speed of Pyrolysis Gases

Supercritical thermal cracking experiments using -dodecane (C12) and two hydrocarbon fuels (HF-I and HF-II) were conducted, and the compositions of the resulting pyrolysis gases were determined. The laminar flame speeds of the pyrolysis gases were measured using a constant-pressure chamber by outwardly expanding spherical flames and compared with theoretical values. Both the hydrocarbon classes and the pyrolysis temperature play important roles in defining the composition of the pyrolysis gas. Specifically, variations in the gas composition can be ascribed to disparities in the thermal cracking of different hydrocarbons. Laminar flame speeds decreased in the order of . The flame speeds obtained from C12 pyrolysis gases initially increased with increasing pyrolysis temperature and then gradually decreased, peaking at 560°C. The presence of highly reactive hydrogen and ethylene was found to significantly enhance the laminar flame speed, and so the normalized flame speed varied linearly with increases in the concentrations of these two species. The remaining species exhibited a nearly linear inhibitory effect. Finally, the C/H ratio of the pyrolysis gas played an important role in determining the adiabatic flame temperature and laminar flame speed.

Py-GC-MS of refuse materials in waste to energy point of view

Abstract Thermochemical waste to energy technology could efficiently tackle waste management problem, but it could emit dangerous pollutant if the quality of the feedstock is bad and standard operating condition was not met. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) methodology was used to assess the quality of refuse material for solid fuel by identifying the degradation behavior and produced gas in pyrolysis condition. The material used was a mineral water plastic seal (PS), laminated packaging (LP), refuse derived fuel (RDF) and mechanical biological treatment residue (SR). The results show that PS and LP have similar degradation curve since it mainly consists of polypropylene. The gas product characteristic was also similarly consisted of CO, CO2, and hydrocarbon. RDF and SR have more complex degradation curve consist of three peaks. Both are composite material consist of organics, plastics, and inert materials. CO and CO2 are still major pyrolysis gas composition. This work could be developed to build process simulation to simulate real waste to energy plant.

MANUFACTURING GASEOUS PRODUCTS BY PYROLYSIS MICROALGAE BIOMASS

Algae biomass is considered as an alternative raw material for the production of biofuels. The search for new types of raw materials, including high-energy types of microalgae, remains relevant, since the share of motor fuels in the structure of the global fuel and energy balance remains consistently high (about 35%), and the price of oil is characterized by high volatility. The authors have considered the advantages of microalgae as sources of raw materials for fuel production. Biochemical and thermochemical conversion are proposed as technologies for their processing. This paper presents the results of the study of the pyrolysis of the biomass of clonal culture of blue-green microalgae / cyanobacteriumArthrospira platensis rsemsu 1/02-Pfrom the collection of the Research Laboratory of Renewable Energy Sources of the Lomonosov Moscow State University. An experiment to study the process of pyrolysis of microalgae biomass was carried out at the experimental facility of the Institute of High Temperatures RAS in pure nitrogen grade 6.0 to create an oxygen-free environment with a linear heating rate of 10 ºС / min from room temperature to 1000 ºС. The whole process of pyrolysis proceeded in the field of endothermy. The specific amounts of solid residue, pyrolysis liquid and gaseous products were experimentally determined. As a result of the pyrolysis of microalgae biomass weighing 15 g, the following products were obtained: 1) coal has the mass of the solid residue is 2.68 g, or 17.7% of the initial mass of the microalgae (while 9.3% of the initial mass of the microalgae remained in the reactor); 2) pyrolysis liquid – weight 3.3 g, or 21.9% of the initial weight; 3) non-condensable pyrolysis gases – weight 1.15 l. The specific volumetric gas yield (the amount of gas released from 1 kg of the starting material) was 0.076 Nm3/ kg. The analysis of the composition and specific volume yield of non-condensable pyrolysis gases formed in the process of pyrolysis, depending on temperature. It is shown that with increasing temperature, the proportion of highcalorie components of the gas mixture (hydrogen, methane and carbon monoxide) increases. The calorific value of the mixture of these gases has been estimated.

Ablative thermal protection system under uncertainties including pyrolysis gas composition

Spacecrafts such as Stardust (NASA, 2006) are protected by an ablative Thermal Protection System (TPS) for their hypersonic atmospheric entry. A new generation of TPS material, called Phenolic Impregnated Carbon Ablator (PICA), has been introduced with the Stardust mission. This new generation of low density carbon-phenolic composites is now widely used in the aerospace industry. Complex heat and mass transfer phenomena coupled to phenolic pyrolysis and pyrolysis gas chemistry occur in the material during atmospheric entry. Computer programs, as the Porous material Analysis Toolbox based on OpenFoam (PATO) released open source by NASA, allow to study the material response. In this study, a non-intrusive Anchored Analysis of Variance (Anchored-ANOVA) method has been interfaced with PATO to perform low-cost sensitivity analysis on this problem featuring a large number of uncertain parameters. Then, a Polynomial-Chaos method has been employed in order to compute the statistics of some quantities of interest for the atmospheric entry of the Stardust capsule, by taking into account uncertainties on effective material properties and pyrolysis gas composition. This first study including pyrolysis gas composition uncertainties shows their key contribution to the variability of the quantities of interest.

Co-pyrolysis of lignocellulosic biomass with low-quality coal: Optimal design and synergistic effect from gaseous products distribution

Co-pyrolysis of lignocellulosic biomass and low-quality coal can alternate fossil fuel partially and utilize biomass on a commercial scale. Gaseous products from co-pyrolysis process can be widely applied in industries due to the advantage in transportation and compression. Thus, investigation of synergistic effect and optimal design about gas products is essential for efficiently and comprehensively design of the process. In this research, three model compounds of lignocellulosic biomass (cellulose, hemicellulose, lignin) and wheat straw were co-pyrolyzed with a kind of low-quality coal via a drop tube furnace. Based on the component insight of biomass and response surface methodology, synergetic effects from gas distribution were investigated. The influence of reaction condition (biomass ratio and pyrolysis temperature) on the yield and high heat value (HHV) of gaseous products were explored. Optimal result for the objective of the highest effective gas yield during co-pyrolysis were obtained. Results revealed that both positive and negative synergic effects on yields and composition of pyrolysis gas were presented. When pyrolysis temperature was 600 °C, both wheat straw and three model compounds promoted the formation of H2 and CO. Negative effects on CO2 were observed when co-pyrolysis of cellulose/wheat straw with coal at the temperature of 600 °C to 800 °C. Whether positive or negative synergy existed depended on the mixing ratio, temperature and combined action of lignin, hemicellulose, and cellulose. For coal and hemicellulose mixtures, the mixing ratio of 0.03 and temperature of 936 °C can get the highest yield of H2 (20.56 mmol/g). Moreover, the maximum yield of CO and CO2 was obtained at cellulose mixing ratio of 0.99 and 0.98 at 787 °C and 626 °C, respectively. Based on the view of biomass composition, the results can be used to optimize the gaseous products distribution during co-pyrolysis of coal and biomass.

Effects of various additives on the pyrolysis characteristics of municipal solid waste

Additives can have a significant impact on the pyrolysis process. The effects of three additives (CaO, MSW char and biomass) on the pyrolysis characteristics of municipal solid waste (MSW) were investigated using a fixed-bed reactor. In addition, the effects of additives and temperature on the MSW pyrolysis product yield, the composition of MSW pyrolysis gases, and the composition of MSW pyrolysis tar were investigated using fixed bed reactor, GC–MS and FTIR, respectively. The results showed that the maximum tar yield of the MSW reached 28.73% at 600 °C and the tar yield decreased with increasing amounts of CaO and MSW. The tar yield began to decrease when the additive amount of CaO was 5% and decreased to 23.05% when the additive amount of MSW char (C) was 30%. Synergistic pyrolysis of the biomass and MSW was observed when the additive amount of the pine increased to 75% (with a tar yield of 37.91%). Regarding gas composition, with increasing additives content, the CO2 yield decreased, while the CO yield increased. According to the FTIR analysis of the tar, CaO enhanced the condensation of the aromatic rings and converted the aliphatic hydrocarbons, while C reduced the oxygenic groups of the tar. The GC–MS results revealed that the additives decreased the yield of carboxylic acid and ethanol, and increased the ester yield. The additives were also found to have a deoxidation effect that decreased the acid content, potentially improving the quality and stability of the tar.

Self-activation of biochar from furfural residues by recycled pyrolysis gas

Biochar samples with controllable specific surface area and mesopore ratio were self-activated from furfural residues by recycled pyrolysis gas. The objective of this study was to develop a new cyclic utilization method for the gas produced by pyrolysis. The influences of preparation parameters on the resulting biochar were studied by varying the pyrolysis-gas flow rate, activation time and temperature. Structural characterization of the produced biochar was performed by analysis of nitrogen adsorption isotherms at 77 K and scanning electron microscope (SEM). The pyrolysis gas compositions before and after activation were determined by a gas chromatograph. The results indicated that the surface area of the biochar was increased from 167 m2/g to 567 m2/g, the total pore volume increased from 0.121 cm3/g to 0.380 cm3/g, and the ratio of the mesopore pore volume to the total pore volume increased 17–39.7%. The CO volume fraction of the pyrolysis gas changed from 34.66 to 62.29% and the CO2 volume fraction decreased from 48.26% to 12.17% under different conditions of pyrolysis–gas flow rate, activation time and temperature. The calorific values of pyrolysis gas changed from 8.82 J/cm3 to 14.00 J/cm3, which were higher than those of conventional pyrolysis gases. The slower pyrolysis–gas flow rate and higher activation time increased the efficiency of the reaction between carbon and pyrolysis gas. These results demonstrated the feasibility of treatment of the furfural residues to produce microporous and mesoporous biochar. The pyrolysis gas that results from the activation process could be used as fuel. Overall, this new self-activation method meets the development requirements of cyclic economy and cleaner production.

Effect of autogenous pressure on volatile pyrolysis products

The thermal decomposition of wood, conducted in the absence of oxygen, includes so-called primary and secondary reactions, where secondary reactions are regarded as those involving previously formed decomposition products. This study uses a pyrolysis–gas chromatograph-mass spectrometer, Py-GC/MS, to investigate the degree to which secondary reactions affect the composition of the volatile pyrolysis gases. Samples were Monterey Pine (Pinus radiata) and were held in either open crucibles or sealed capsules. For specified heating profiles ranging from 240 to 700 °C, volatiles escaped soon after they evolved in the open crucibles but in the sealed capsules they were retained at high pressures for long residence times. Differences were observed over the entire range of treatment temperatures, which suggests that secondary reactions occur concurrently to primary reactions and implies that they are more dependent on vapour-phase concentration than on temperature. In comparison to the open crucible experiments, the sealed capsule experiments produced more low molecular weight pyrolysis products and more long chain alkanes, alkenes and methyl ketones, but at the expense of extractives, carbohydrate and lignin derivatives. The sealed capsules also had less oxygen in the condensable fraction, characterised by the presence of alkyl substituted compounds. Instead the open crucible experiments contained methoxyl substituted compounds. These differences are all characteristic of secondary reactions. This study shows that controlling the extent of secondary reactions is an invaluable tool for optimising pyrolysis.

Pyrolysis of wastewater sludge and composted organic fines from municipal solid waste: laboratory reactor characterisation and product distribution

Sludge from municipal wastewater treatment plants and organic fines from mechanical sorting of municipal solid waste (MSW) are two common widespread waste streams that are becoming increasingly difficult to utilise. Changing perceptions of risk in food production has limited the appeal of sludge use on agricultural land, and outlets via landfilling are diminishing rapidly. These factors have led to interest in thermal conversion technologies whose aim is to recover energy and nutrients from waste while reducing health and environmental risks associated with material re-use. Pyrolysis yields three output products: solid char, liquid oils and gas. Their relative distribution depends on process parameters which can be somewhat optimised depending on the end use of product. The potential of pyrolysis for the conversion of wastewater sludge (SS) and organic fines of MSW (OF) to a combustion gas and a carbon-rich char has been investigated. Pyrolysis of SS and OF was done using a laboratory fixed-bed reactor. Herein, the physical characterisation of the reactor is described, and results on pyrolysis yields are presented. Feedstock and chars have been characterised using standard laboratory methods, and the composition of pyrolysis gases was analysed using micro gas chromatography. Product distribution (char/liquid/gas) from the pyrolysis of sewage sludge and composted MSW fines at 700°C for 10 min were 45/26/29 and 53/14/33%, respectively. The combustible fractions of pyrolysis gases range from 36 to 54% for SS feedstock and 62 to 72% from OF. The corresponding lower heating value range of sampled gases were 11.8–19.1 and 18.2–21.0 MJ m−3, respectively.

Energy Evaluation and Techno-economic Analysis of Low-Rank Coal (Victorian Brown Coal) Utilization for the Production of Multi-products in a Drying–Pyrolysis Process

In this paper, utilization of Victorian brown coal in a drying - pyrolysis process to make products is techno-economically assessed. The pyrolysis process is coupled with the drying and briquette making processes in order to improve the overall efficiency and quality of the products. The pyrolysis process led to the production of char, liquid oil and hydrogen – rich, non-condensable gases. A steady-state Aspen Plus simulation model was developed that provides estimated mass and energy balances for the overall system. The effect of a change in the heating mode and heating medium of the dryer on the overall energy and overall product yields was examined. Additionally, the effect of a change in the pyrolysis gas composition and coal initial moisture were studied. Results revealed that the rotary drum dryer with hot flue gas as a heating medium showed the best performance in terms of the final yield of the pyrolysis products and CO2 emission rate. In the best case scenario using hot flue gas directly in a rot...

Experimental investigation of the influence of reaction atmosphere on the pyrolysis of printed circuit boards

Printed circuit boards (PCB) are one of the most challenging fractions of waste electrical and electronic equipment (WEEE) in terms of recycling due to their complexity and diversity. Pyrolysis seems to be a promising alternative for production of energy carriers from its organic fraction with simultaneous recovery of metals. Reaction atmosphere is among the process parameters that affects the thermal decomposition as well as the products’ formation and distribution. In this study, the decomposition of two different PCB fractions in inert and steam atmospheres has been investigated by means of thermogravimetric analysis (TGA) and lab scale fixed bed reactor experiments. It was found that the decomposition of the tested materials in steam atmosphere starts at lower temperatures and proceeds slower compared to the N2 atmosphere. Moreover, a two-step decomposition has been observed on the PCB sockets fraction due to the fact that high amount of antimony oxide was present, a common additive for improving the flame retardancy, which have been also observed on previous studies (Wu et al., 2014). The presence of steam influence the pyrolysis gas composition and promotes additional vaporisation of antimony as verified by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Finally, the liquid fraction has been qualitatively analysed using a GC/MS in order to determine the brominated compounds as well as other compounds that are produced from this process.

CFD Simulation of Devolatilization of Biomass with Shrinkage Effect

Abstract In the present work, a computational fluid dynamics (CFD) model is used to assess devolatilization of biomass under high-temperature condition. The CFD code is based on a multiscale Eulerian–Lagrangian solver previously developed in the framework of OpenFOAM. A particle shrinkage model proposed by Colomba Di Blasi is implemented in this study to better calculate size evaluation of biomass particle. In addition, a two-step devolatilization model is added into the solver. The CFD model is validated against experimental data of rapid devolatilization of biomass in an electric heated drop tube reactor. Compared to the constant volume model and the simplified constant density shrinkage model, the applied model can better reflect changes of particle size at both 750 °C and 950 °C. In particular, the model gives very good prediction on the terminal particle size with the model constants α=0.3, β=0, and γ=0.3. The calculated composition of pyrolysis gas is fairly close to the experimental data as well.

Comprehensive experimental investigation and numerical modeling of the combined partial oxidation-gasification zone in a pilot downdraft air-blown gasifier

A pilot downdraft gasifier is investigated experimentally using almond shell biomass as feedstock. Experimental temperature profiles along the different zones of the gasifier are measured and overlapping regions between the different gasifier stratified zones is proved: we identified two main zones (drying-pyrolysis zone and partial oxidation-reduction zone) instead of four stratified zones as proposed in the literature. In light of this experimental finding, a two dimensional mathematical model is developed for the combined partial oxidation-reduction zone based on conservation equations coupled to the heterogeneous and homogeneous chemistry. Partial oxidation and thermal cracking mechanisms of tar are proposed based on the available kinetic data. The model is developed for the quasi-steady state period of the experiment and used to simulate the heat and mass transport fields within the computational domain, analyze the interaction between the heterogeneous and homogeneous reactions and evaluate the performance of the gasifier in terms of tar conversion and syngas composition. Validation against the mean experimental temperature data and the producer gas composition at the outlet of the reactor are presented and a satisfactory agreement is observed. The influence of pyrolysis gas composition, air flow rate and bed porosity on the process and its outputs is also investigated.

Composition of pyrolysis gas from oil shale at various stages of heating

Underground, the pyrolytic conversion of an oil shale in the nearest future may become an alternative source of a fuel gas and a synthetic oil. The main scientific problem in designing this technology is to provide a methodology for determination of the optimal mode of heating the subterranean formation. Such a methodology must allow predicting the composition of the pyrolysis products and the energy consumption at a given heating rate of the subterranean formation. The paper describes the results of heating of the oil shale fragments in conditions similar to the underground. The dynamics of composition of the gaseous products of pyrolysis are presented and analyzed.

Conversion of non-condensable pyrolysis gases from plastics into carbon nanomaterials: Effects of feedstock and temperature

The conversion of non-condensable pyrolysis gases from plastic feedstock into carbon nanomaterials through catalytic chemical vapor deposition was investigated. Three samples, namely low density polyethylene (LDPE), polypropylene (PP) and a mixture of four plastics (MP), containing LDPE (40%), PP (40%), polystyrene (PS) (10%) and polyethylene terephthalate (PET) (10%), were used as raw materials in the pyrolysis process. The plastics were initially pyrolyzed at 600°C producing condensable oils and non-condensable gases. The non-condensable gases were further heated in the second reactor either at 500 or 800°C. Heating at 800°C caused decomposition of the gases to intermediate products (methane, ethylene and condensable oils), which were converted over a nickel-based catalyst into multi-walled carbon nanotubes with similar yields and properties regardless of the plastic feedstock. Heating at 500°C had no effect on the composition of non-condensable pyrolysis gases. However, the carbon materials produced over the catalyst had different yields and structures implying the influence of plastic feedstock on the properties of materials was more pronounced at lower synthesis temperature. At 500°C, the MP non-condensable pyrolysis gases were converted into a mixture of carbon nanocages and multi-walled carbon nanotubes with higher graphitization degree compared to carbon materials from PP and LDPE, which were mainly multi-walled carbon nanotubes. Furthermore, the carbon yield was the highest using PP followed by LDPE and MP samples (32%, 21% and 3%, respectively). The lower carbon yield using LDPE compared to PP was attributed to the lower concentration of unsaturated hydrocarbons in the pyrolysis gas, while the low yield using MP was caused by the presence of PET in the plastic mixture, decreasing the reactivity of hydrocarbon gases over the catalyst.

Replacing conventional fuels in USA, Europe, and UK with plastic pyrolysis gases – Part I: Experiments and graphical interchangeability methods

The development of effective recycling methods for plastic wastes is critical in terms of resource security and environmental conservation. In this work, we focused on the gaseous pyrolysis products of plastic wastes as alternatives to natural gas (NG) and propane. The pyrolysis of polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET), and their mixtures was carried out under isothermal conditions at 500, 700, and 900°C. The potential for replacing NG and propane with the pyrolysis gases was assessed by graphical interchangeability methods for the first time. The pyrolysis gas compositions obtained from the mixed plastics and HCl-scrubbed gas from the PVC were deemed suitable NG alternatives in Europe and the USA. In addition, PE and PP pyrolysis gases showed the potential for replacing propane in the USA, whereas gases from PET showed the least interchangeability. Thus, the graphical interchangeability methods are promising for evaluating the potential of plastic waste pyrolysis gases as alternatives to NG.

Study of sewage sludge pyrolysis liquids using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

The pyrolysis of a Shanghai municipal sewage sludge sample was conducted using a slowly heating and gas sweeping fixed-bed reactor. The pyrolysis liquids produced at three predetermined temperatures (400, 500 and 700°C) were fully examined using GC×GC-TOFMS. The pyrolysis mechanism of the sewage sludge was analyzed online using in situ FTIR from ambient temperature to 600°C. The primary objectives of this study are to (i) determine the chemical composition of the pyrolysis liquids, and (ii) to assess the effect of temperature on the composition of the liquid products. Whereas studies that use GC–MS have normally found hundreds of compounds, analysis of the pyrolysis liquids by GC×GC-TOFMS detected thousands of compounds. Moreover, this method detected some isomers as well. Pyrolysis in this pyrolyzer was observed to produce abundant cyclosiloxanes, which were rarely reported in previous studies, and this may be related to the use of a comprehensive analytical method (GC×GC-TOFMS). The temperature dramatically affected the liquid composition. The proportions of monoaromatics and polyaromatic ketones increased with increasing temperature, and theoretically, the high temperature could promote the production of phenyl rings. The generation of long-chain aliphatic amides and nitriles occurred mainly below 400°C, whereas nitrogen-containing alicyclic hydrocarbons were generated mainly at 500°C. The cyclosiloxanes were part of the original composition of the sewage sludge and were predominantly released below 400°C. The variation in the functional group of the sewage sludge was consistent with that of the pyrolysis gas and liquid compositions.

Mechanistic and Kinetic Analysis of Na2SO4-Modified Laterite Decomposition by Thermogravimetry Coupled with Mass Spectrometry.

Nickel laterites cannot be effectively used in physical methods because of their poor crystallinity and fine grain size. Na2SO4 is the most efficient additive for grade enrichment and Ni recovery. However, how Na2SO4 affects the selective reduction of laterite ores has not been clearly investigated. This study investigated the decomposition of laterite with and without the addition of Na2SO4 in an argon atmosphere using thermogravimetry coupled with mass spectrometry (TG-MS). Approximately 25 mg of samples with 20 wt% Na2SO4 was pyrolyzed under a 100 ml/min Ar flow at a heating rate of 10°C/min from room temperature to 1300°C. The kinetic study was based on derivative thermogravimetric (DTG) curves. The evolution of the pyrolysis gas composition was detected by mass spectrometry, and the decomposition products were analyzed by X-ray diffraction (XRD). The decomposition behavior of laterite with the addition of Na2SO4 was similar to that of pure laterite below 800°C during the first three stages. However, in the fourth stage, the dolomite decomposed at 897°C, which is approximately 200°C lower than the decomposition of pure laterite. In the last stage, the laterite decomposed and emitted SO2 in the presence of Na2SO4 with an activation energy of 91.37 kJ/mol. The decomposition of laterite with and without the addition of Na2SO4 can be described by one first-order reaction. Moreover, the use of Na2SO4 as the modification agent can reduce the activation energy of laterite decomposition; thus, the reaction rate can be accelerated, and the reaction temperature can be markedly reduced.