Pyrolysis of biocollagenic wastes of vegetable tanning. Optimization and kinetic study

Three solid wastes generated from the vegetable tanning of bovine skin in the Leather Industry (shavings, trimmings and buffing dust) were mixed together in the same proportions in which they were produced and the mixture was then used as a pyrolysis precursor for this research study. The optimal pyrolysis conditions for obtaining energy from the generated fractions (char, tar and gas fraction), and the preparation of activated carbons from the carbonaceous material (char), were established. The final conditions were chosen from two different points of view, the thermogravimetric results (TG/DTG) obtained at different heating rates (2–20 °C/min) and an optimization of the pyrolysis parameters by means of experiments carried out in a conventional furnace. The pyrolysis conditions finally selected were: heating rate (5 °C/min), final temperature (750 °C), and time at final temperature (60 min) and inert gas flow (N₂ 150 ml/min). The carbonaceous material (char) obtained exhibits good properties as a solid fuel due to its high calorific value and relatively low ash content. It also shows suitable characteristics as a precursor for the preparation of activated carbons. The condensable fraction has a predominantly phenolic nature and contains significant amounts of nitrogen compounds (nitriles, diketopiperazines, etc.), alkanes, alkenes, acids and esters, derived from the decomposition of tannins and collagen, with possible industrial applications in the preparation of chemical products. The gaseous phase is rich in carbon monoxide and carbon dioxide, and also contains a certain amount of methane and hydrogen. The syngas content increases with the pyrolysis temperature. A kinetic study of the pyrolysis was carried out using a model of independent reactions. The variation in the heating rate produced a slight shift to higher temperatures of the decomposition peaks, although this did not significantly affect either the kinetic parameters of the degradation processes or the percentage weight losses.     

Study of products yield of bagasse and sawdust via slow pyrolysis and iron-catalyze

In this paper, the via slow pyrolysis behavior of the bagasse and sawdust were studied at the different heating rates, the different iron-containing blend pyrolysis and the treatment temperature, the further understood for the pyrolysis of agricultural residues. The distribution of the products yield of the slow pyrolysis process, it is typically performed at temperature between 200 and 600 °C, the pyrolysis temperature increased, the bio-liquids and gas yields tended to increase, which at 400 °C was able to achieve maximum bio-liquids yields, the biochar yields tended to downward. For different heating rate, in the heating rate ranges for 80–100 W, the bio-liquids products yield curve increased from 44.5 wt% to 46.5 wt% for bagasse; the sawdust products yield increased from 41 wt% to 42.75 wt%. Iron-catalysts blend pyrolysis (0, 10, 25, 40 and 50 wt%), the bagasse bio-liquid yields respectively 56.25 wt% in the presence 50% iron-catalysts blend pyrolysis; the sawdust bio-liquid yields respectively 52.5 wt% in the presence 40% iron-catalysts blend. The pyrolysis process were calculated according to the kinetic mechanism were examined, the pyrolysis activation energy was between 6.55 and 7.49 kcal/mol for bagasse. Sawdust the pyrolysis activation energy was between 11.52 and 11.76 kcal/mol. Therefore, in this study a pyrolysis model of bagasse and sawdust thermal treatment may provide both agricultural and forestry transformation importance of resources.     

Pyrolysis of textile wastes: I. Kinetics and yields

Thermal behavior of textile waste was studied by thermogravimetry at different heating rates and also by semi-batch pyrolysis. It was shown that the onset temperature of mass loss is within 104–156 °C and the final reaction temperature is within 423–500 °C. The average mass loss is 89.5%. There are three DTG peaks located at the temperature ranges of 135–309, 276–394 and 374–500 °C, respectively. The first two might be associated with either with decomposition of the hemicellulose and cellulose or with different processes of cellulose decomposition. The third peak is possibly associated to a synthetic polymer. At a temperature of 460 °C, the expected amount of volatiles of this waste is within 85–89%. The kinetic parameters of the individual degradation processes were determined by using a parallel model. Their dependence on the heating rate was also established. The pyrolysis rate is considered as the sum of the three reaction rates. The pyrolysis in a batch reactor at 700 °C and nitrogen flow of 60 ml/min produces 72 wt.% of oil, 13.5 wt.% of gas and 12.5 wt.% of char. The kinetic parameters of the first peak do not vary with heating rate, while those of the second and the third peak increase and decrease, respectively, with an increasing heating rate, proving the existence of complex reaction mechanisms for both cases.     

Pyrolysis of wood impregnated with phosphoric acid for the production of activated carbon: Kinetics and porosity development studies

The pyrolysis of impregnated wood for the production of activated carbon is investigated. Laboratory experiments are performed in a TG for heating rates of 10 °C/min and 20 °C/min and a mathematical model for the kinetics of the pyrolysis process is developed and validated. The effect of the temperature and of the time duration of the pyrolysis process on the specific surface of the activated carbon is examined on the basis of experiments conducted in a crossed bed reactor. Results indicate that the temperature and the residence time in the pyrolysis reactor may be optimised. Indeed, it is found that the maximum specific surface of the end product is obtained for pyrolysis processes conducted at a temperature of 400 °C for a time period of 1 h.     

Characterization of the different fractions obtained from the pyrolysis of rope industry waste

A study of the possibilities of pyrolysis for recovering wastes of the rope's industry has been carried out. The pyrolysis of this lignocellulosic residue started at 250 °C, with the main region of decomposition occurring at temperatures between 300 and 350 °C. As the reaction temperature increased, the yields of pyrolyzed gas and oil increased, yielding 22 wt.% of a carbonaceous residue, 50 wt.% tars and a gas fraction at 800 °C. The chemical composition and textural characterization of the chars obtained at various temperatures confirmed that even if most decomposition occurs at 400 °C, there are some pyrolytic reactions still going on above 550 °C. The different pyrolysis fractions were analyzed by GC–MS; the produced oil was rich in hydrocarbons and alcohols. On the other hand, the gas fraction is mainly composed of CO₂, CO and CH₄. Finally, the carbonaceous solid residue (char) displayed porous features, with a more developed porous structure as the pyrolysis temperature increased.     

Influence of FCC catalyst steaming on HDPE pyrolysis product distribution

A commercial FCC catalyst based on a zeolite active phase has been used in the catalytic pyrolysis of HDPE. The experimental runs have been carried out in a conical spouted bed reactor provided with a feeding system for continuous operation. Different treatments have been applied to the catalyst to improve its behaviour. This paper deals with the optimization of catalyst steaming and pyrolysis temperature in order to maximize the production of diesel-oil fraction. The performance of the fresh catalyst has been firstly studied at 500 °C. This catalyst gives way to 52 wt% gas yield, 35 wt% light liquid fraction and a low yield of C₁₀⁺ fraction (13 wt%). After mild steaming (5 h at 760 °C) the results show a significant improvement in product distribution. Thus, gas yield decreases to 22 wt%, the yield of light liquid is similar to that of the fresh one (38 wt%), whereas the yield of the desired C₁₀⁺ fraction increases to 38 wt%. Nevertheless, the best results have been obtained when a severe steaming is applied to the catalyst (8 h at 816 °C) and pyrolysis temperature is reduced to 475 °C. There is a significant reduction in the gaseous fraction (8 wt%). The light liquid fraction has also been reduced to 22 wt%, but the yield of diesel fraction increases to 69 wt%. Moreover, the deactivation of the catalyst has also been studied under the optimum conditions.     

Feedstock recycling of synthetic and natural rubber by pyrolysis in a fluidized bed

An indirect heated fluidized bed process has been used for the pyrolysis of synthetic and natural rubber. The throughput capacity for the continuously running plant was 500–3000 g/h. The results are compared to a pilot plant for the pyrolysis of whole tires. Beside the recovery of oil and carbon black it was another goal of the study to investigate how much monomer material such as isoprene and isobutene can be obtained from synthetic and natural rubber. The pyrolysis parameters were optimized such as pyrolysis temperature, kind of fluidizing gas, and residence time of the gas in the pyrolysis reactor. Main products of the pyrolysis of tires are an aromatic-rich oil and carbon black, which can be reused. While it was possible to obtain only 2–4 wt% of isobutene, the isoprene content reached 22 wt% from natural rubber.     

Characterization of the water-insoluble pyrolytic cellulose from cellulose pyrolysis oil

Water-insoluble pyrolytic cellulose with similar appearance to pyrolytic lignin was found in cellulose fast pyrolysis oil. The influence of pyrolysis temperature on pyrolytic cellulose was studied in a temperature range of 300–600 °C. The yield of the pyrolytic cellulose increased with temperature rising. The pyrolytic cellulose was characterized by various methods. The molecular weight distribution of pyrolytic cellulose was analyzed by gel permeation chromatography (GPC). Four molecular weight ranges were observed, and the M_w of the pyrolytic cellulose varied from 3.4 × 10³ to 1.93 × 10⁵ g/mol. According to the elemental analysis (EA), the pyrolytic cellulose possessed higher carbon content and lower oxygen content than cellulose. Thermogravimetric analysis (TGA) indicated that the pyrolytic cellulose underwent thermo-degradation at 127–800 °C and three mass loss peaks were observed. Detected by the pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), the main pyrolysis products of the pyrolytic cellulose included saccharides, ketones, acids, furans and others. Fourier transforms infrared spectroscopy (FTIR) also demonstrated that the pyrolytic cellulose had peaks assigned to CO stretching and glycosidic bond, which agreed well with the Py-GC/MS results. The pyrolytic cellulose could be a mixture of saccharides, ketones, and their derivatives.     

The vaporization of semi-volatile compounds during tobacco pyrolysis

Pyrolysis of tobacco, a complex biomass matrix, was investigated to further understand thermal decomposition processes that are accompanied by evaporation of relatively stable non-polymeric endogenous compounds. Pyrolysis of two types of tobacco, bright and burley were studied using thermo-gravimetry mass spectrometry (TG–MS) and field ionization mass spectrometry (FIMS) analyses. Tobacco contains biopolymers and many non-polymeric compounds. Unlike many biomass pyrolysis tars derived from wood or cellulose, tobacco pyrolysis tars can contain significant amounts of high molecular weight endogenous constituents such as waxes and terpenes that are transferred intact. The phenomenon of evaporation of high molecular weight non-polymeric compounds is illustrated by tobacco micro-sample pyrolysis in FIMS under vacuum (at a pressure of 10⁻⁴ Torr). These experiments indicate that the evaporation of relatively stable high molecular weight species occurs below about 220 °C generating 300 Da and higher molecular weight products; and, decomposition of tobacco biopolymers such as starch, cellulose, hemicellulose, lignin, and pectin occurs mostly at temperatures higher than 220 °C producing species mostly with molecular weight below 300 Da. Some of the high molecular weight compounds, such as stigmasterol (412 Da), α-tocopherol (430 Da), and solanesol (630 Da), were tentatively identified using the FIMS spectra.     

Pyrolysis of cohesive meat and bone meal in a bubbling fluidized bed with an intermittent solid slug feeder

Meat and bone meal (MBM) is a mass-produced by-product of the meat rendering industry. It has great potential as a feedstock for the production of bio-fuels. Meat and bone meal, however, is a highly cohesive and temperature sensitive material and has traditionally been found to be very difficult, if not impossible, to feed properly into pyrolysis reactors or bubbling fluidized beds. This study showcases an application of the ICFAR intermittent solid slug feeder technology and its capability of successfully feeding the MBM regularly at an average feeding rate of 0.34 g/s into the reactor.A highly automated and instrumented fast pyrolysis pilot plant has been used to process meat and bone meal residues and to operate within a wide range of temperatures (450–600 °C). This is the first study dealing with the pyrolysis of pure meat and bone meal at various operating conditions continuously fed into a laboratory-scale fluidized bed reactor. All liquid and solid products have been analyzed (yields, HHV, GC–MS, elemental analysis, and ash mineral analysis). The homogenous bio-oil produced is an attractive fuel with a significant high heating value (HHV) of 31.5 MJ/kg and an average liquid yield of 43 wt% at 550 °C. The highest water-free HHV (36.7 MJ/kg) was found at 500 °C, with a liquid yield of 35 wt% at this temperature. The optimized pyrolysis temperature, at which the heat from the gas combustion can provide the heat required for processing MBM, while maximizing the bio-oil liquid yield and process energy yield, is 550 °C. Under these conditions, the pyrolysis process energy yield is 91%.The study also demonstrates a new technique to accurately determine the heat of pyrolysis reaction energy required by the process, using a non-invasive water calibration method.     

Catalytic effects of copper(II) chloride and aluminum chloride on the pyrolytic behavior of cellulose

The cellulose without and with catalyst (CuCl₂, AlCl₃) was subjected to pyrolysis at temperatures from 350 to 500 °C with different heating rate (10 °C/min, 100 °C/s) to produce bio-oil and selected chemicals with high yield. The pyrolytic oil yield was in the range of 37–84 wt% depending on the temperature, the heating rate and the amount of metal chloride. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil. The mixing cellulose with both metal chlorides results with a significant decrease of the liquid product. The non-catalytic pyrolysis of cellulose gives the highest mass yield of levoglucosan (up to 11.69 wt%). The great influence of metal chloride amount on the distribution of bio-oil components was observed. The copper(II) chloride and aluminum chloride addition to cellulose clearly promotes the formation of levoglucosenone (up to 3.61 wt%), 1,4:3,6-dianhydro-α-d-glucopyranose (up to 3.37 wt%) and unidentified dianhydrosugar (MW = 144; up to 1.64 wt%). Additionally, several other compounds have been identified but in minor quantities. Based on the results of the GC–MS, the effect of pyrolysis process conditions on the productivity of selected chemicals was discussed. These results allowed to create a general model of reactions during the catalytic pyrolysis of cellulose in the presence of copper(II) chloride and aluminum chloride.     

The pyrolysis characteristics of moso bamboo

In the research, thermogravimetry (TG), a combination of thermogravimetry and Fourier transform infrared spectrometer (TG–FTIR) and X-ray diffraction (XRD) were used to investigate pyrolysis characteristics of moso bamboo (Phyllostachys pubescens). The Flynn–Wall–Ozawa and Coats–Redfern (modified) methods were used to determine the apparent activation energy (E_a). The TG curve indicated that the pyrolysis process of moso bamboo included three steps and the main pyrolysis occurred in the second steps with temperature range from 450 K to 650 K and over 68.69% mass was degraded. TG–FTIR analysis showed that the main pyrolysis products included absorbed water (H₂O), methane gas (CH₄), carbon dioxide (CO₂), acids and aldehydes, ammonia gas (NH₃), etc. XRD analysis expressed that the index and width crystallinity of moso bamboo gradually increased from 273 K to 538 K and cellulose gradually degraded from amorphous region to crystalline region. The E_a values of moso bamboo increased with conversion rate increase from 10 to 70. The E_a values were, respectively 153.37–198.55 kJ/mol and 152.14–197.87 kJ/mol based on Flynn–Wall–Ozawa and Coats–Redfern (modified) methods. The information was very helpful and significant to design manufacturing process of bio-energy, made from moso bamboo, using gasification or pyrolysis methods.     

Phase transitions of CaTiO3 ceramics sintered with the aid of NaF and MgF2

New phases with initial composition (1 ? x)CaTiO₃ ? xNaF ? xMgF₂ (0 ≤ x ≤ 0.20) have been prepared at low temperature (950 °C) from mixtures of CaTiO₃ and fluorides NaF and MgF₂. The oxyfluorides obtained have been characterized by X-ray diffraction at room temperature and indexed by isotypy with orthorhombic CaTiO₃. The microstructures of these phases are observed by scanning electron microscopy. Dielectric measurements have been carried out during cooling cycle from 500 °C to room temperature at two frequencies (100 Hz, 1 kHz). Differential scanning calorimetry (DSC), thermogravimetry (TG) and differential thermogravimetry (DTG) analyses have been performed, respectively, from room temperature up to 550 °C (DSC) and 920 °C (TG–DTG). The dielectric measurements revealed two anomalies which have been confirmed by DSC analyses. These phenomena are ascribed to second order phase transitions. The variation of the real permittivity with temperature is in agreement with the class I capacitor specifications. However, the dielectric losses have to be improved.     

H2 enriched fuels from co-pyrolysis of crude glycerol with biomass

Pyrolysis of glycerol has been identified as a possible route for producing high added value fuels like renewable hydrogen (H₂). Crude glycerol (CG) is the main byproduct of biodiesel industry and without purification it is a low added value material due to the presence of impurities. Co-pyrolysis of CG with biomass may improve the efficiency of the process and as a primary step of gasification give important information concerning the maximization of H₂ concentration in the produced gas. Moreover, the thermochemical treatment of crude glycerol–biomass mixtures may offer several economic and environmental advantages in biodiesel industry and reduce the cost of biodiesel production. A mixture of CG with olive kernel (OK) was used as pyrolysis feed material. Pyrolysis of a 25 wt% mixture of CG with OK at high temperature (T = 720 °C) seemed to promote steam reforming reactions leading to an increase of H₂ concentration of 11.6 vv% in the pyrolysis gas in comparison to H₂ in gas obtained by low temperature pyrolysis (T = 520 °C).     

Quality variations of poultry litter biochar generated at different pyrolysis temperatures

Producing biochar and biofuels from poultry litter (PL) through slow pyrolysis is a farm-based, value-added approach to recycle the organic waste. Experiments were conducted to examine the effect of pyrolysis temperature on the quality PL biochar and to identify the optimal pyrolysis temperature for converting PL to agricultural-use biochar. As peak pyrolysis temperature increased incrementally from 300 to 600 °C, biochar yield, total N content, organic carbon (OC) content, and cation exchange capacity (CEC) decreased while pH, ash content, OC stability, and BET surface area increased. The generated biochars showed yields 45.7–60.1% of feed mass, OC 325–380 g kg⁻¹, pH 9.5–11.5, BET surface area 2.0–3.2 m² g⁻¹, and CEC 21.6–36.3 cmol_c kg⁻¹. The maximal transformation of feed OC into biochar recalcitrant OC occurred at 500 °C, yet 81.2% of the feed N was lost in volatiles at this temperature. To produce agricultural-use PL biochar, 300 °C should be selected in pyrolysis; for carbon sequestration and other environmental applications, 500 °C is recommended.     

Conventional and microwave induced pyrolysis of coffee hulls for the production of a hydrogen rich fuel gas

This paper describes the conventional and microwave-assisted pyrolysis of coffee hulls at 500, 800 and 1000 °C. The influence of the pyrolysis method and temperature on the product yields and on the characteristics of the pyrolysis products is discussed. It was found that the pyrolysis of this particular residue gives rise to a larger yield of the gas fraction compared to the other fractions, even at relatively low temperatures. A comparison of microwave-assisted pyrolysis and conventional pyrolysis showed that microwave treatment produces more gas and less oil than conventional pyrolysis. In addition, the gas from the microwave has much higher H₂ and syngas (H₂ + CO) contents (up to 40 and 72 vol.%, respectively) than those obtained by conventional pyrolysis (up to 30 and 53 vol.%, respectively), in an electric furnace, at similar temperatures. From the pyrolysis fraction yields and their higher heating values it was found that the energy distribution in the pyrolysis products decreases as follows: gas > solid > oil. Moreover, the energy accumulated in the gas increases with the pyrolysis temperature. By contrast, the energy accumulated in the char decreases with the temperature. This effect is enhanced when microwave pyrolysis is used.     

Production of bio-oil via fast pyrolysis of agricultural residues from cassava plantations in a fluidised-bed reactor with a hot vapour filtration unit

This article reports experimental results on fast pyrolysis of agricultural residues from cassava plantations, namely cassava rhizome (CR) and cassava stalk (CS), in a fluidised-bed fast pyrolysis reactor unit incorporated with a hot vapour filter. The objective of this research was to investigate the effects of reaction temperatures, biomass particle size and the use of simple hot vapour filtration on pyrolysis product yields and properties. Results showed that the optimum pyrolysis temperatures for CR and CS were 475 °C and 469 °C, which gave maximum bio-oil yields of 69.1 wt% and 61.4 wt% on dry biomass basis, respectively. The optimum particle size for bio-oil production in this study was 250–425 μm. The use of the hot filter led to a reduction of 6–7 wt% of bio-oil yield. Nevertheless, the filtered bio-oils appeared to have a better quality in terms of initial viscosity, solids content, ash content and stability.     

Upgrading of woody biomass by torrefaction under pressure

In this study, the upgrading by torrefaction of leucaena, woody biomass, at 200–250 °C under volumetric pressure up to 4 MPa was examined. It was found that the yield of torrefied leucaena decreased with the increase in torrefaction temperature, whereas at the same temperature the yield of torrefied leucaena increased with the increase in torrefaction pressure. From the elemental analyses, the higher carbon content in torrefied leucaena can be achieved by the rising of torrefaction pressure. As large as 92.6% of carbon was recovered in the torrefied leucaena prepared at 250 °C and 4 MPa. On the other hand, the oxygen content decreased to 31.1% for the leucaena torrefied at 250 °C and 4 MPa. The higher heating value (HHV) of leucaena torrefied at high pressure increased significantly when compared to that of leucaena torrefied at atmospheric pressure. As large as 94.3% of energy yield was achieved with the mass yield of 74.4% for the torrefaction at 250 °C and 4 MPa. From the subsequent pyrolysis and combustion in TGA, leucaena torrefied under pressure showed the difference of weight decreasing curves comparing to that of leucaena torrefied at atmospheric pressure. It was found that the weight of leucaena torrefied at high pressure started to decrease at temperature lower than 200 °C. The char yield at 800 °C for the leucaena torrefied at high pressure increased with the increase in torrefaction pressure. These results suggested that the structure of leucaena was changed by the torrefaction under pressure and the cross-linking reactions during the pyrolysis were enhanced by the pressure during the torrefaction resulting in increase in char yields. The substantial increase in char combustion rate was also found for leucaena torrefied under pressure.     

Micro-pyrolysis of technical lignins in a new modular rig and product analysis by GC–MS/FID and GC × GC–TOFMS/FID

A new offline-pyrolysis rig has been designed to allow multifunctional experiments for preparative and analytical purposes. The system conditions can be set and monitored, e.g. temperature, its gradients and heat flux. Some special features include (1) high heating rates up to 120 °C/s with pyrolysis temperatures up to 850 °C at variable pyrolysis times and (2) the selection of different atmospheres during pyrolysis. A complete mass balance of products and reactants (gas, liquids and solids) by gravimetric methods and sequential chromatographic analyses was obtained.The pyrolytic behaviour and the decomposition products of lignin-related compounds were studied under different conditions: heating rates (from 2.6 °C/s up to 120 °C/s), pyrolysis temperatures at 500 °C and 800 °C in different atmospheres (N₂, H₂, and mixtures of N₂ and acetylene). Kraft lignin, soda lignin, organosolv lignin, pyrolytic lignin from pine bio-oil, residues from biomass hydrolysis and fermentation were studied.The obtained pyrolysis products were classified into three general groups: coke, liquid phase and gas phase (volatile organic compounds (VOC) and permanent gases). The liquid fraction was analysed by GC–MS/FID. In addition, comprehensive two-dimensional GC was applied to further characterise the liquid fraction. VOCs were semi-quantified by a modified headspace technique using GC–MS/FID analysis. The micro-pyrolysis rig proved to be an efficient and useful device for complex pyrolysis applications.     

Pyrolytic behavior of cellulose in presence of montmorillonite K10 as catalyst

Cellulose and cellulose/montmorillonite K10 mixtures of different ratio (9:1, 3:1, 1:1) were subjected to pyrolysis at temperatures from 350 to 500 °C with different heating rate (10 °C/min, 100 °C/s) to produce bio-oil and selected chemicals with high yield. The pyrolytic oil yield was in the range of 46–73.5 wt% depending on the temperature, the heating rate and the amount of catalyst. The non-catalytic fast pyrolysis at 500 °C gives the highest yield of bio-oil (84 wt%). The blending cellulose with increasing amount of montmorillonite K10 results in significant, linear decrease in bio-oil yield. The great influence of montmorillonite K10 amount on the distribution of bio-oil components was observed at 450 °C with a heating rate of 100 °C/s. The addition of catalyst to cellulose promotes the formation of 2-furfural (FF), various furan derivatives, levoglucosenone (LGO) and (1R,5S)-1-hydroxy-3,6-dioxabicyclo-[3.2.1]octan-2-one (LAC). Simultaneously, the share of levoglucosan (LG) in bio-oil decreases from 6.92 wt% and is less than 1 wt% when cellulose:MK10 (1:1, w/w) mixture at 450 °C is rapidly pyrolyzed. Additionally, several other compounds have been identified but in minor quantities. Their contributions in bio-oil also depend on the amount of catalyst.