Thermal decomposition behavior,characterization and evaluation of pyrolysis products of agricultural wastes

Thermal decomposition behavior during pyrolysis, the composition and the physicochemical characteristics of the pyrolysis products were studied for four agricultural wastes from Southern Greece. These wastes are produced in abundance in the Mediterranean Region but still remain relatively unexploited, while there is also lack or little relevant scientific information. Pyrolysis process for the examined samples was studied using a TGA analyzer and a properly tested and calibrated TG/MS setup, at a heating rate of 10 °C/min up to 850 °C. Determination of important quantitative parameters of pyrolysis as a function of temperature, on an instantaneous or integral basis, and correlation of the evolved gas results with the degradation of pseudocomponents of raw biomass was made possible. The average higher heating value of the pyrolysis light gases was found to be in a satisfactory for energy purposes range of 11.2–14.4 MJ/Nm³. Furthermore, biochars produced at 450, 550 and 650 °C in a fixed bed reactor were found to exhibit calorific value ranging from 20.1 to 28.7 MJ/kg and structural stability. They were also found to have a high nutrients content and below limits or negligible heavy metals content for soils applications, regardless of production temperature.     

Pyrolysis kinetics of invasive coastal plant Spartina anglica using thermogravimetric analysis

The pyrolysis kinetics of invasive plant Spartina anglica biomass was investigated via a thermogravimetric (TG) analyzer from 50 to 800°C in an inert argon atmosphere at different heating rates of 5–30°C/min, and the kinetic parameters were deduced by Starink and master-plots methods. The results showed that three stages appeared in the thermal degradation process, and the mean value of activation energy was calculated to be 291.57 kJ/mol by the Starink method. It suggested that the most probable pyrolysis kinetic model was g(α) = [?ln(1-α)]⁴ deduced by the master-plots method, which meant a random nucleation and nuclei growth mechanism. These results provided fundamental useful information for describing the pyrolysis process, and the subsequent designing and running of a pyrolytic processing system using S. anglica as feedstock.     

Olive residues (cuttings and kernels) rapid pyrolysis product yields and kinetics

A study of pyrolysis of olive residues (cuttings and kernels) at a temperature range from 300 to 600°C, has been carried out. The experiments were performed in a captive sample reactor at atmospheric pressure under helium. The yields of the derived gases, pyrolytic liquids and char were determined in relation to pyrolysis temperature, at heating rates of about 200°C/s.As the pyrolysis temperature was increased the percentage mass of char decreased whilst gas and oil products increased. The oil products increased to a maximum value of ∼30 wt% of dry biomass at about 450–550°C. The major gaseous products are CO and CO₂.A simple first order kinetic model has been applied to the evolution of total losses and gases. Kinetic parameters have been estimated and compared with other reported similar data.     

Thermogravimetric and mass spectrometric analysis of powdered pine bark

Using thermal analysis and mass spectrometry, this study examined samples of powdered pine bark by subjecting them to: (a) complete combustion, (b) partial combustion, and (c) pyrolysis. For each of the examined samples, which heated at the rate of 30°C min^?1, temperature regions corresponded to moisture loss and the degassing process. Global and local maximum values of ionic currents representing H₂O, CO₂, CO, and additionally for hydrocarbons such as CH₄, C₂H₄, and C₂H₅ for pyrolysis were identified. Based on the recorded values of ionic currents of hydrocarbons in the helium atmosphere, C₂H₅ dominance was determined at T ≤ 415°C, and CH₄ dominance was determined at T > 415°C. Assuming first-order kinetics, thermogravimetric data were analyzed by the Arrhenius type model, and kinetic parameters were determined.     

Thermal degradation of corn starch based biodegradable plastic plates and determination of kinetic parameters by isoconversional methods using thermogravimetric analyzer

Oil shortage and awareness of environment pollution leads to the extensive use of biodegradable starch-based materials against synthetic plastics. The accumulated wastes of these plastics takes more time for natural recycling and the process is complex. Therefore the best option of recycling would be to convert these polymers into a source of energy by pyrolysis. So to understand the pyrolytic behaviour, kinetics of such waste plastics is studied by using thermogravimetric analysis at different heating rates of 10 °C, 20 °C, 40 °C, 60 °C, 80 °C and 100 °C in nitrogen atmosphere followed by characterization of the pyrolysis products. The kinetic parameters are obtained for two major stages of decomposition in two different temperature ranges 250–620 °C and 620–855 °C by iso-conversional methods such as Friedman, Coats-Redfern, FWO and Kissinger methods. The regression coefficient data (>0.9) of kinetic plots obtained for different methods best fits to the kinetic equation. Empirical formula of the compound is determined by ultimate analysis is CH_2.214S_0.0018O_0.6910. Proximate analysis gives the idea of volatile component which is74.33%. The range of average value of activation energy is 120.7013 kJ/mol to 140.7707 kJ/mol for the biodegradable plastic plate with different conversion (0.1–0.6) and (0.1–0.3) respectively at two different temperatures. The pyrolysis products obtained using a semi-batch reactor are characterized to know their composition and other properties.     

Conjugate Wall Conduction-Fluid Natural Convection in a Three-Dimensional Inclined Enclosure

Laminar conjugate conduction-natural convection heat transfer in a 3-D inclined cubic enclosure comprised of finite thickness conductive walls and central cavity is numerically investigated. The dimensionless governing equations describing the convective flow and wall heat conduction are solved by the high accuracy multidomain pseudospectral method. Computations are performed for different Rayleigh numbers (10³ ≤ Ra* ≤ 10⁶), thermal conductivity ratios (1 ≤ k ≤ 100), dimensionless wall thickness (0 ≤ s ≤ 0.25), and enclosure inclinations (?30° ≤ α ₁ ≤ 30°, 0° ≤ α ₂ ≤ 45°). The effects of the above controlling parameters on the heat transfer performances of the enclosure system are investigated in detail, with emphases on the variations of wall conduction and fluid convection heat transfer, and the interactive heat transfer conditions between solid walls and fluid in the central cavity. Numerical results reveal that the existence of enclosure walls reduces the temperature gradient across the cavity and alters the temperature distribution within the solid walls; thus, the fluid convection is complexly determined by the combined effects of k and s, and is greatly affected by enclosure inclinations at high Rayleigh numbers. Moreover, the temperature distributions and solid-fluid interactive heat transfer conditions are provided for further interpretation and demonstration of the effects of the solid walls.     

Kinetic characteristics of in-situ char-steam gasification following pyrolysis of a demineralized coal

This study aims to examine the char-steam reactions in-situ, following the pyrolysis process of a demineralized coal in a micro fluidized bed reactor, with particular focuses on gas release and its kinetics characteristics. The main experimental variables were temperatures (925 °C?1075 °C) and steam concentrations (15%–35% H₂O), and the combination of pyrolysis and subsequent gasification in one experiment was achieved switching the atmosphere from pure argon to steam and argon mixture. The results indicate that when temperature was higher than 975 °C, the absolute carbon conversion rate during the char gasification could easily reach 100%. When temperature was 1025 °C and 1075 °C, the carbon conversion rate changed little with steam concentration increasing from 25% to 35%. The activation energy calculated from shrinking core model and random pore model was all between 186 and 194 kJ/mol, and the fitting accuracy of shrinking core model was higher than that of the random pore model in this study. The char reactivity from demineralized coal pyrolysis gradually worsened with decreasing temperature and steam partial pressure. The range of reaction order of steam gasification was 0.49–0.61. Compared to raw coal, the progress of water gas shift reaction (CO + H₂O ? CO₂ + H₂) was hindered during the steam gasification of char obtained from the demineralized coal pyrolysis. Meanwhile, the gas content from the char gasification after the demineralized coal pyrolysis showed a low sensitivity to the change in temperature.     

Transformation and release of potassium during fixed-bed pyrolysis of biomass

To study the release and transformation of fuel K during rapid pyrolysis of biomass, wheat straw, corn stalk and rice hull are pyrolyzed in a fixed-bed reactor system during 400–1000 °C, and weight measurement, elemental composition analysis, and chemical fractionation analysis are performed. The effects of fuel type, pyrolysis temperature, co-pyrolysis of different fuels, and water washing pretreatment are discussed. The results show that for all biomass fuels, the released K is far less than the water-soluble K and a sudden increase occurs in the fraction of ion-exchangeable K at 400 °C, whereas a significant increase happens in the fraction of insoluble K above 800 °C. Wheat straw releases less than 5% of K at 400 and 500 °C. As temperature rises, the K release increases abruptly and around 40% of K enters the gas phase at 1000 °C. Rice hull has a slow and linear K release with increasing pyrolysis temperature. Corn stalk has the lowest K release during 400–800 °C. Co-pyrolysis of wheat straw and rice hull reduce the K release at 1000 °C, and the biggest decrement is 0.76 mg g^?1. Water washing removes all the water-soluble K of corn stalk and part of ion-exchangeable K enters the gas phase during pyrolysis of the washed sample. Water washing decreases the K release from 2.77 to 0.18 mg g^?1 at 1000 °C.     

Study on the nitrogen transformation during the primary pyrolysis of sewage sludge by Py-GC/MS and Py-FTIR

The nitrogen transformation with attention to the intermediates and NO_x precursors has been investigated during the primary pyrolysis of sewage sludge by using Pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS) and Pyrolyzer-Fourier transform infrared spectrometry (Py-FTIR). A three-stage process of nitrogen transformation during the sewage sludge pyrolysis was suggested. The decomposition of labile protein and inorganic ammonium salt mainly occurred in the first stage (<300 °C), giving rise to a small amount of NH₃. In the second stage (300–600 °C), the macromolecular protein firstly cracked into small molecular amine compounds, and then went through deamination process, contributed to a large release of NH₃. In the third stage (600–900 °C), the amine compounds converted into nitriles, and generated a large amount of HCN, while the formation of NH₃ slowed down accordingly.     

Utilization possibilities of Albizia amara as a source of biomass energy for bio-oil in pyrolysis process

Pyrolysis is one of the potential routes to harmless energy and useful chemicals from biomass. The pyrolysis of Albizia amara was studied for determining the main characteristics and quantities of liquid products. Particular investigated process variables were temperature from 350 to 550°C, particle size from 0.6 to 1.25 mm, and heating rate from 10 to 30 °C/min. The maximum bio-oil yield of 48.5 wt% at the pyrolysis temperature of 450°C was obtained at the particle size of 1.0 mm and at the heating rate of 30 °C/min. The bio-oil product was analyzed for physical, elemental, and chemical composition using Fourier transform infrared spectroscopy and gas chromatography spectroscopy. The bio-oil contains mostly phenols, alkanes, alkenes, saturated fatty acids and their derivatives. According to the experimental results, the pyrolysis bio-oil can be used as low-grade fuel having heating value of 18.63 MJ/kg and feedstock for chemical industries.     

Conversion of waste tires to liquid products via sodium carbonate catalytic pyrolysis

This study deals with the pyrolysis of waste tires supplied from the transport industry. The base material of tire is latex, which is derived from natural rubber trees. Nowadays rubber (Hevea brasiliensis) is a fast-growing tropical tree crop, which is being cultivated for latex and ultimately for tire production. Waste tires can be recycled for energy and valuable materials in many ways; however tire burning is the most common practice for heat generation. In recent years, the catalytic conversion of waste tires through pyrolysis into liquid, solid, and gas products was investigated. Liquids product was produced from the catalytic pyrolysis of waste tire at high temperature (up to 600°C) using sodium carbonate (Na₂CO₃) as a catalyst. Thermo-physical characteristics of the produced liquid samples showed that up to 85% of the produced oil can be used in internal combustion engines. Gasoline and diesel fuel contents in the liquid products are 45% and 40%, respectively. The gas chromatographic (GC) analysis of the volatile fraction of pyrolysis products showed styrene (28.1%) and butadiene (10.7%) as dominant compounds. The gaseous phase includes C₁–C₄ hydrocarbons (4.8%) and the liquid phase includes C₅–C₈ hydrocarbons (6.5%) of the total products.     

Liquefaction of palm kernel shell to bio-oil using sub- and supercritical water: An overall kinetic study

Palm kernel shell was liquefied using sub- and supercritical water at 330–390 °C and 25 MPa for different reaction times. The overall kinetics of the liquefaction based on the conversion of biomass was analyzed using kinetic equation adopted from the literature, and the kinetic parameters were estimated from the evaluation of the kinetic equation. In this study, the rate constant (k) increased from 0.43 to 0.49 s^?1 with reaction temperature from 330 to 390 °C. The relationship of rate constant (k) and temperature agreed reasonably well with the Arrhenius equation. The activation energy (E) and pre-exponential factor (A) values for the liquefaction process were estimated to be 6.70 kJ/mol and 1.65 s^?1, respectively. In addition, the experimental bio-oil yields with respect to reaction time were well-fitted using the modified Reverchon-Sesti Osseo equation.     

Study of extraction and pyrolysis of Jordan tar sand

The extraction and pyrolysis of tar sand from Wadi Isal, Jordan have been investigated. Solvent type, mixing time, temperature, particle size and alkali concentration have been identified as important parameters for bitumen recovery. The results show that hot water extraction is ineffective since a small amount of bitumen has been obtained even at 80°C. Kerosene extraction shows a maximum bitumen recovery of about 43% at 80°C and 180–250 μm particle size. The kinetic parameters of pyrolysis have been determined based on first‐order rate expression and their values were in agreement with other published data in the literature. Copyright © 1999 John Wiley & Sons, Ltd.     

Thermal decomposition behavior of tobacco stem Part I: TGA–FTIR–MS analysis

In the present study, the thermal degradation behavior of tobacco stem was examined by means of a thermogravimetric analyzer (TGA) under nitrogen atmosphere at temperature range of 25–1,000°C. The TG curve indicated that the pyrolysis process of tobacco included three zones, and main pyrolysis occurred in the second zone by means of the decomposition of hemicellulose, cellulose, and lignin in a temperature range of 180–540°C. Furthermore, the gases evolved during the degradation were analyzed simultaneously via TGA coupled with a Fourier transform infrared spectrometer (FTIR) and mass spectrometer (MS). Carbon dioxide, methane, water, formaldehyde, and propanal were the main volatiles detected via MS and confirmed by FTIR.     

Energy Applications of Biomass: Pyrolysis of Apricot Stone

Apricot stone (Prunus armeniaca L.) was pyrolyzed in a directly heated fixed-bed reactor under nitrogen atmosphere. Effects of sweeping gas flow rates and pyrolysis temperature on the pyrolysis of the biomass were also studied. Pyrolysis runs were performed using reactor temperatures between 400°C and 700°C with heating rate of about 300°C min^?1. As the pyrolysis temperature was increased, the percentage mass of char decreased while gas product increased. The product yields were significantly influenced by the process conditions. The bio-oil obtained at 550°C, at which the liquid product yield was maximum, was analyzed. It was characterized by Fourier transform infrared spectroscopy (FT-IR). In addition, the solid and liquid products were analyzed to determine their elemental composition and calorific value. Chemical fractionation of bio-oil showed that only low quantities of hydrocarbons were present, while oxygenated and polar fractions dominated.     

Hydrogen-rich syngas produced from the co-pyrolysis of municipal solid waste and wheat straw

The co-thermochemical conversion of Municipal Solid Waste (MSW) and biomass is a new environmental technology and can produce hydrogen-rich syngas. This study investigated the co-pyrolysis of MSW and wheat straw, using a drop-tube furnace experiment. Using a temperature range of 500 °C–1000 °C, the study assessed pyrolysis gas yield, product distribution, gas low heating value, and carbon conversion of co-pyrolysis MSW with different amounts of wheat straw. Adding wheat straw only slightly increases the gas yield and carbon conversion, but improved the carbon monoxide and carbon dioxide in the syngas. At an experimental temperature below 700 °C, adding wheat straw promoted the cracking reaction of hydrocarbon gas, generated by the pyrolysis of MSW. At a temperature of 600 °C, adding 25% wheat straw improved carbon conversion in the blended sample. This study provides a basis for the application of MSW and WS thermo-chemical conversion.     

CO2 gasification characteristics of nascent pyrolyzed particles from coals and oil shale

In this work, the co‐pyrolysis characteristics of oil shale with two typical coals, bitumite and lignite, and the co‐gasification characteristics of the mixture pyrolyzed fuels were studied via thermo‐gravimetric analysis. The individual fuels and mixture fuels were first pyrolysis in N₂ atmosphere to specified temperature (450, 550, and 620 °C) at the heating rate of 20, 30 and 40 °C/min, respectively, and then maintained at the given temperature for 20 min before converted to CO₂ ambient to conduct the CO₂ gasification tests. The kinetic behavior and effects of both fuel types and pyrolysis temperature were investigated. The shoulder peak at around 550 °C observed in the derivative of weight loss derivative thermogravimetry analysis (DTG) curve during the pyrolysis of oil shale has confirmed the existence of specific reactions of oil shale at around 550 °C that leads to a sharp trough in the differential curves of co‐pyrolysis with coals and the unusual change in activation energies of gasification. In isothermal pyrolysis stage, oil shale lost its vast majority of organic matters at the temperature lower than 550 °C. The escape of pyrolysis gas and liquids in the coals is much harder than that in oil shale. The interaction between oil shale and bitumite was too weak to discriminate both in the pyrolysis and CO₂ gasification process. The variation of the particle surface structure caused by the releasing of volatile gases is strongly affected by the reaction rate and temperature. Quick volatile decomposition and gas releasing lead to the increase of surface area, decrease of the average pore diameter as well as the uniformization of the pore structure, while the higher temperature results in the blockade and merging of fine pores. The two factors lead to the greatest mass loss rate in the pyrolyzed particles obtained at 550 °C in temperature programmed CO₂ gasification stage. Two model‐free methods, Friedman method and Flynn–Wall–Ozawa method, were used to extract kinetic parameters from the experimentally determined pyrolyzed fuel conversions. The volatile contend has a significant influence on the fixed carbon conversion during the partially pyrolyzed particles' CO₂ gasification. In this study, significant interactions existed in co‐thermal utilization, both pyrolysis and CO₂ gasification, of oil shale and lignite. It is therefore surmised that co‐gasification of pyrolyzed lignite and oil shale may represent a feasible, practical route to high‐efficiency utilization of these fuels. Copyright © 2017 John Wiley & Sons, Ltd.     

An investigation of raw and torrefied lignocellulosic biomasses with CaO during combustion

The thermal degradation of three categories of raw and torrefied biomass [agri-residue: wheat straw, forest residue: sawdust, energy crop: miscanthus] was studied in a TGA-FTIR system with or without catalyst (CaO). The thermal degradation of biomass was carried out in the temperature range of 25–900 °C at a heating rate of 20 °C/min. The air flow rate was controlled based on the stoichiometric air requirement for complete combustion. The non-linear regression (NLREG) model was adopted to determine the kinetic parameters. The weight loss, heat flow, maximum weight loss temperature, and activation energy were observed to be dependent on the types of biomass and the process parameters. The maximum weight loss temperature was higher for torrefied biomass compared with raw biomass. The activation energy was higher in the case of torrefied biomass compared with raw biomass, and CaO helped to shrink the activation energy. The maximum weight loss temperature and activation energy were varied from 310 to 509 °C and 15–85 kJ/mol, respectively. The CaO supplement seems to have a positive impact on the thermal degradation process; thus, it may help in improving the thermal degradation process of torrefied biomass.     

Combustion behavior of KOH desulphurized coals assessed by TGA-DTG

This work presents the results obtained from the experimental study on the effects of KOH treatment and its combustion behavior of high sulfur Indian coal. Coal was treated with 5–20% KOH (v/v) concentration for 6–24 h reaction time to identify the effects of KOH treatment on coal properties. Experimental results showed that upto 36.79% of total sulfur can be removed from coal with 20% KOH concentration and 24 h contact time at atmospheric condition. However, gross calorific value of coal decreased from 6800 to 6084 kcal/kg due to removal of combustibles from coal. Combustion characteristics of treated coal were assessed by Thermo-gravimetric analysis/ Differential thermo-gravimetric (TGA/DTG analysis). Further various combustion kinetic parameters like ignition temperature, peak temperature, burnout temperature, activation energy (E), and pre-exponential factor (A) are estimated. Experimental results show that the ignition temperature of coal decreased from 321°C to 252°C, peak temperature decreased from 459°C to 409°C due to changes in the coal matrix after desulfurization. The activation energy of coal calculated decreased from 79 to 45 kJ/mol due to desulfurization using 20% KOH concentration and 24 h reaction time.     

Pyrolysis analysis of different Cuban natural fibres by TGA and GC/FTIR

In this work, the pyrolysis of different Cuban biomass such as: sugar cane bagasse, coffee, residue of tobacco and sawdust of pine has been studied. The pyrolysis was carried out at different temperatures in a small furnace placed at the injection port of a gas chromatograph coupled to a Fourier transform infrared spectrometer (Py-GC/FTIR). Thermogravimetric analysis (TGA) was also carried out using a thermobalance. For tobacco residue, pyrolysis yield of charcoal and liquid products decreases with pyrolysis temperature (300–600 °C). When the pyrolysis is carried out at 300 °C charcoal yield is similar for tobacco residue, sawdust of pine and husk of coffee (≈40%) while for husk of coffee and sugar cane bagasse the charcoal yield is lower but the yield of the liquid product is higher.