Pyrolysis characteristics of Oriental white oak: Kinetic study and fast pyrolysis in a fluidized bed with an improved reaction system

The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol^− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil.     

Effects of particle size on the fast pyrolysis of oil mallee woody biomass

This study aims to investigate the effects of biomass particle size (0.18-5.6 mm) on the yield and composition of bio-oil from the pyrolysis of Australian oil mallee woody biomass in a fluidised-bed reactor at 500 °C. The yield of bio-oil decreased as the average biomass particle size was increased from 0.3 to about 1.5 mm. Further increases in biomass particle size did not result in any further decreases in the bio-oil yield. These results are mainly due to the impact of particle size in the production of lignin-derived compounds. Possible inter-particle interactions between bio-oil vapour and char particles or homogeneous reactions in vapour phases were not responsible for the decreases in the bio-oil yield. The bio-oil samples were characterised with thermogravimetric analysis, UV-fluorescence spectroscopy, Karl-Fischer titration as well as precipitation in cold water. It was found that the yields of light bio-oil fractions increased and those of heavy bio-oil fractions decreased with increasing biomass particle size. The formation of pyrolytic water at low temperatures (<500 °C) is not greatly affected by temperature or particle size. It is believed that decreased heating rates experienced by large particles are a major factor responsible for the lower bio-oil yields from large particles and for the changes in the overall composition of resulting oils. Changes in biomass cell structure during grinding may also influence the yield and composition of bio-oil.     

Fast pyrolysis of chicken litter and turkey litter in a fluidized bed reactor

Disposal of poultry litter such as chicken litter and turkey litter is becoming a major problem in the USA poultry industry because of environmental pressures and health concerns. Poultry litters form wood chips, chicken litter (flock 1, flock 2 and broiler) and turkey litter were converted into bio-oil, gas and char in a fluidized bed reactor at the temperature ranges of 450–550 °C. The bio-oil yield of poultry litter was relatively low (15–30 wt%) compared to wood derived bio-oil (34–42 wt%). The gas yield was increased from 32 to 61 wt% with increasing reaction temperature, and char yield was between 22 and 45 wt% depending on age and reaction conditions. The higher heating value (HHV) of the poultry litter bio-oil were between 26 and 29 MJ/kg, whereas that of the bedding material (wood chips) was 24 MJ/kg. The dynamic viscosities of bio-oil were varied from 0.01 to 27.9 Pa s at 60 °C, and those of values were decreased with increasing shear rate.     

Fast pyrolysis of rice husk under different reaction conditions

In this work, rice husk, an agricultural waste in Korea, was pyrolyzed under different reaction conditions (temperature, flow rate, feed rate, and fluidizing medium) in a fluidized bed with the influence of reaction conditions upon characteristics of the bio-oil studied. The optimal pyrolysis temperature for bio-oil production was found to be between 400 and 450 °C. Higher flow rates and feeding rates were more effective for its production. The use of the product gas as the fluidizing medium led to the highest bio-oil yield. With the exception of temperature, no single operation variable largely affected the physicochemical properties of the bio-oil.     

Catalytic upgrading of fast pyrolysis oil over hzsm-5

The upgrading of bio-oil, obtained by fast pyrolysis of maple wood, was studied over HZSM-5 in a fixed bed micro-reactor operated at atmospheric pressure and in the temperature range 330-425°C. The objective of upgrading was to maximize the amount of organic distillate product with a high yield of aromatic hydrocarbons. A maximum organic distillate of 38 wt.% of bio-oil, which represented 28.6 wt.% of wood, was obtained at 370°C. The yield of aromatic hydrocarbons was 19.9 wt.% of wood. Above 400°C, nearly 50 wt.% of the bio-oil was converted to coke and char. The conversion of non-volatile components of the bio-oil (pitch) to volatiles was at a maximum of 68 wt. % at 370°C. However, when the bio-oil was co-processed with tetralin, the maximum conversion of non-volatiles increased to 86 wt.% at 410°C and the amounts of coke and char decreased. The yield of aromatic hydrocarbons also decreased to a maximum of 10.3 wt. % of wood. The role of tetralin was mainly as a diluent and not as a hydrogen donor solvent.     

PET pyrolysis and hydrolysis mechanism in the fixed pyrolyzer

In the conventional polyethylene terephthalate (PET) pyrolysis process, the formation of char by excessive pyrolysis is mainly due to the dehydration mechanism, so water is considered an auxiliary agent that can effectively inhibit excessive pyrolysis. The preparation of terephthalic acid (TPA) by steam-assisted pyrolysis of PET is an effective method to achieve closed-loop recycling of waste PET. To ensure that the reaction is mild enough to reduce excessive cracking products such as char and benzoic acid and thus increase the yield of TPA, it is critical to reduce the reaction rate while maintaining a sufficient excess steam coefficient. Under the optimal operating conditions, when the temperature rise rate was 0.5 °C min⁻¹ and the excess steam coefficient was 150, the yield of TPA was 72.5 wt.%, and the purity was 85.5%. Noticeably, the steam-assisted pyrolysis system is a heterogeneous reaction system whose reaction mechanism is different from the conventional hydrolysis and pyrolysis reactions and has a unique reaction path. The mechanistic study indicates that, in addition to the thermal cracking of PET molecules occurring in conventional pyrolysis, hydroxyl attack and transfer, and supplementation of benzene ring hydrogen also occur between water and intermediate molecules. Meanwhile, it has also been proven that the intermolecular hydrogen transfer between intermediate molecules and water molecules is the key to reduce the intensity of the reaction and inhibit the formation of char. This discovery illustrates the mechanism of the reaction between water and PET in the steam-assisted pyrolysis process in the fixed pyrolyzer and justifies the distinction between it and the pyrolysis and hydrolysis processes of PET. It provides a theoretical basis for optimizing the pyrolysis process of PET, which is essential for the industrialization of TPA preparation from PET steam-assisted pyrolysis.     

泡桐水中直接液化制取生物油的实验研究

以水为溶剂,Na₂CO₃为催化剂,在 1 L 高压釜中对泡桐直接液化制取生物油。实验结果表明,在原料量 80 g,水 480 mL,催化剂用量 5%,搅拌速率 300 r/min,停留时间5～10 min,液化温度为300～315℃ 的条件下得到了较佳的液化效果,生物油总产率可达到 60% 以上,残渣率可降至 2% 以下。     

Hydrogen production via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system

Hydrogen production was prepared via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system. Low-cost catalyst dolomite was chosen for the primary steam reforming of bio-oil in consideration of the unavoidable deactivation caused by direct contact of metal catalyst and bio-oil itself. Nickel-based catalyst Ni/MgO was used in the second stage to increase the purity and the yield of desirable gas product further. Influential parameters such as temperature, steam to carbon ratio (S/C, S/CH₄), and material space velocity (W_BHSV, GHSV) both for the first and the second reaction stages on gas product yield, carbon selectivity of gas product, CH₄ conversion as well as purity of desirable gas product were investigated. High temperature (> 850 °C) and high S/C (> 12) are necessary for efficient conversion of bio-oil to desirable gas product in the first steam reforming stage. Low W_BHSV favors the increase of any gas product yield at any selected temperature and the overall conversion of bio-oil to gas product increases accordingly. Nickel-based catalyst Ni/MgO is effective in purification stage and 100% conversion of CH₄ can be obtained under the conditions of S/CH₄ no less than 2 and temperature no less than 800 °C. Low GHSV favors the CH₄ conversion and the maximum CH₄ conversion 100%, desirable gas product purity 100%, and potential hydrogen yield 81.1% can be obtained at 800 °C provided that GHSV is no more than 3600 h^− 1. Carbon deposition behaviors in one-stage reactor prove that the steam reforming of crude bio-oil in a two-stage fixed bed reaction system is necessary and significant.     

Biodiesel production from Nannochloropsis microalgal biomass-derived oil: An experimental and theoretical study using the RSM-CCD approach

Biodiesel production from Nannochloropsis is investigated in the current study. Based on the extraction studies, the used biomass is composed of 50% saponifiable lipids, which turns this species to a vulnerable feedstock for biodiesel production. It should also be noted that the acidity of the obtained crude bio-oil is higher than 2 mg KOH/g, hence it was attempted to survey the biodiesel production from the obtained oil through the esterification reaction with the aid of response surface methodology (RSM). According to the data, the highest biodiesel yield (99.5%) from the bio-oil is obtained at a reaction temperature of 69°C, a reaction time of 30 min, a methanol to oil molar ratio of 9:1, and an H₂SO₄ concentration of 0.13 wt.%. In the next step, the in-situ extraction and esterification of Nannochloropsis were investigated at the observed optimum reaction conditions. Based on the analysis, biodiesel yield from the dry cell weight of the biomass is considered to be 16%, which accounts for 99% conversion of bio-oil to biodiesel.     

Steam gasification reactivity of char from rapid pyrolysis of bio-oil/char slurry

A slurry of bio-oil and char originating from wood pyrolysis is a promising gasifier feed-stock because of its high energy density. When such a slurry is injected into a high temperature gasifier it undergoes a rapid pyrolysis yielding a char which then reacts with steam. The char produced by pyrolysis of an 80 wt% bio-oil/20 wt% char mixture at heating rates of 100-10,000 °C/s was subjected to steam gasification in a thermogravimetric analyzer. The original wood char from the bio-oil production was also tested. Gasification was conducted with 10-50 mol% steam at temperatures from 800 to 1200 °C. Reactivity of the slurry chars increased with pyrolysis heating rate, but was lower than that of the original chars. Kinetic parameters were established for a power-law rate model of the steam-char reaction, and compared to values from the literature. At temperatures over 1000 °C, the gasification rates appeared to be affected by diffusional resistance.     

Investigation of rapid conversion of switchgrass in subcritical water

The reaction characteristics of switchgrass conversion in subcritical water were investigated using a batch reactor under conditions of rapid rising to 250–350 °C and pressure of 20 MPa, with reaction times varying from 1–300 s. The effects of temperature and reaction time on product distribution and yields of chemical products were investigated. High conversion of switchgrass (90 wt.% on dry biomass basis) can be obtained in less than 60 s under a relative lower reaction temperature of 350 °C, compared with that in a switchgrass flash pyrolysis process where switchgrass conversion achieves only 58.9–78.8 wt.% in temperature range of 450–550 °C. The yield of water solubles (WS) can reach 37 wt.% after reaction for 1 s at 250 °C. The increases in temperature and reaction time lead to increases of the biomass conversion and the yield of gas, while WS yield decreases by secondary decomposition reactions. Many lignin-derived compounds were identified by GC-MS analysis and could well be recovered in methanol solubles (MS). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis of methanol insolubles (MI) indicated that the lignocellulosic matrix could be significantly decomposed, and no char formation was observed, while many lignin structures were left in the MI products. These results provide important information for recovering value-added chemicals from energy crops and biomass waste.     

Influence of alcohol addition on properties of bio-oil produced from fast pyrolysis of eucalyptus bark in a free-fall reactor

Fast pyrolysis of eucalyptus bark was carried out in a free-fall pyrolysis unit at different temperatures ranging from 400 to 550 °C to produce bio-oil, char and gas. The bio-oil produced at optimum temperature was mixed with alcohols with an aim to improve its properties. The results showed that the maximum bio-oil yield of 64.65 wt% on dry biomass basis could be obtained at the pyrolysis temperature of 500 °C. The addition of a small proportion (2.5–10%) of alcohol into the bio-oil could improve its viscosity, stability and heating value. These effects were further enhanced when increasing the alcohol.     

Performance assessment of drop tube reactor for biomass fast pyrolysis using process simulator

Biomass pyrolysis process from a drop tube reactor was modelled in a plug flow reactor using Aspen Plus process simulation software. A kinetic mechanism for pyrolysis was developed considering the recent improvements and updated kinetic schemes to account for different content of cellulose, hemicellulose, and lignin. In this regard, oak, beechwood, rice straw, and cassava stalk biomasses were analyzed. The main phenomena governing the pyrolysis process are identified in terms of the characteristic times. Pyrolysis process was found to be reaction rate controlled. Effects of pyrolysis temperature on bio-oil, gases, and char yields were evaluated. At optimum pyrolysis conditions (i.e., 500°C), a bio-oil yield of 67.3, 64, 43, and 52 wt.% were obtained from oak, beechwood, rice straw, and cassava stalk, respectively. Oak and beechwood were found to give high yields of bio-oil, while rice straw produced high gas and char yields compared to other biomasses. Although temperature is the main factor that plays a key role in the distribution of pyrolysis products, the composition of cellulose, hemicellulose, and lignin in the feedstock also determines the yield behaviour and composition of products. With the rise in pyrolysis temperature, further decomposition of intermediate components was initiated favouring the formation of lighter fractions. Comparably, species belonging to the aldehyde chemical family had the highest share of bio-oil components in all the investigated feedstocks. Overall, the present study shows a good agreement with the experimental study reported in the literature, confirming its validity as a predictive tool for the biomass pyrolysis process.     

Preparation of carbon foams with enhanced oxidation resistance by foaming molten sucrose using a boric acid blowing agent

Boric acid was used as a blowing agent as well as a boron precursor for the preparation of boron-doped carbon foams from molten sucrose. The H⁺ generated, due to the formation of a complex between sucrose and boric acid, catalyzes the –OH to –OH condensation reaction leading to the polymerization and the foaming of the molten sucrose. The char yield of the solid organic foams increased from 24 to 39 wt.% when the boric acid concentration increased from 0 to 8 wt.%, due to the formation of the B–O–C cross-links between sucrose polymer by B–OH to C–OH condensation. The inductively coupled plasma analysis showed the presence of 0.44–3.4 wt.% boron in the carbon foams. The density and compressive strength decreased and cell size increased with boric acid concentration. The room temperature thermal conductivity of the boron-doped carbon foams was in the range of 0.057–0.043 W m⁻¹ K⁻¹. The weight loss studies by dynamic and isothermal heating showed the increased oxidation resistance with boron concentration.     

Characterization of the liquid and solid products obtained from the oxidative pyrolysis of meat and bone meal in a pilot-scale fluidised bed plant

Pyrolysis of meat and bone meal material has been studied in an auto-thermal pilot scale unit with a fluidised bed reactor based on Bioware Technology. The heating value of the bio-oil samples is around 33-36 MJ/kg, whilst the nitrogen content is between 7.3 wt.% and 9.0 wt.%. Liquid fractionation with solvents of the bio-oil has been carried out. Chemical analyses of the fractions have shown that the main components in the bio-oil samples are alkanes, alkenes, oxygenated components (as alcohols) and nitrogen compounds (as nitriles) which are identified in the water insoluble fraction. Knowing the chemical composition of the bio-oils is important for assessing possible chemical and pharmaceutical applications of these bio-oils. The char samples have a notable ash content (63 wt.% to 77 wt.%) and its high Ca content could make it suitable for use as a catalyst in gasification processes.     

Synthesis of char,bio-oil and gases using a screw feeder pyrolysis reactor

In this study, char, bio-oil and gases were synthesized with a continuous pyrolysis process from residual plants consisting of Cogongrass and Manilagrass at temperatures in the range of 400–550°C, with a feed rate of 150, 350, and 550 rpm (r min^?1). The product yield calculation showed that the liquid yield was highest at 53.56%, at 350 rpm. After separation of the bio-oil from liquid phase, the bio-oil was found to have components of approximately 33.38%, of which the solid yield (char) was highest at 27.35%, at 350 rpm, and the gas yield was highest at 43.60%, at 150 rpm. This indicates that biomass from residual plants materials produced good yields because of low solid and gas yields while having high liquid yield.     

Pyrolytic characteristics of Jatropha seedshell cake in thermobalance and fluidized bed reactors

Pyrolytic kinetic parameters of Jatropha seedshell cake (JSC) were determined based on reaction mechanism approach under isothermal condition in a thermobalance reactor. Avrami-Erofeev reaction model represents the pyrolysis conversion of JSC waste well with activation energy of 36.4 kJ mol^?1 and frequency factor of 9.18 s^?1. The effects of reaction temperature, gas flow rate and feedstock particle size on the products distribution have been determined in a bubbling fluidized bed reactor. Pyrolytic bio-oil yield increases up to 42 wt% at 500 °C with the mean particle size of 1.7 mm and gas flow rate higher than 3U _mf , where the maximum heating value of bio-oil was obtained. The pyrolytic bio-oil is characterized by more oxygen, lower HHVs, less sulfur and more nitrogen than petroleum fuel oils. The pyrolytic oil showed plateaus around 360 °C in distribution of components’ boiling point due to high yields of fatty acid and glycerides.     

Experimental study of the influence of acid wash on cellulose pyrolysis

The analysis of microstructure and polymerization degree showed that acid wash altered the cellulose morphology and decreased the polymerization degree significantly. A series of experiments were done to study the effect of acid wash on cellulose rapid pyrolysis. Experimental results showed that under acid pretreatment, the yield of bio-oil decreased while the production of gas and char increased. With an increase in acid concentration, this trend would be further enhanced. Sulphuric acid limited the formation of bio-oil more effectively than hydrochloric acid and phosphoric acid. According to the GC-MS analysis of bio-oil, high-concentration acid wash restrained the formation of levoglucosan by catalyzing dehydration process and cross linking reaction. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(2): 179–183 [译自: 燃料化学学报]     

Biofuels from waste fish oil pyrolysis: Continuous production in a pilot plant

Fast pyrolysis of waste fish oil was performed in a continuous pyrolysis pilot plant. The experiment was carried out under steady-state conditions in which 10 kg of biomass was added at a feed rate of 3.2 kg h⁻¹. A bio-oil yield of 72-73% was obtained with a controlled reaction temperature of 525 °C. The bio-oil was distilled to obtain purified products with boiling ranges corresponding to light bio-oil and heavy bio-oil. These biofuels were characterized according to their physico-chemical properties, and compared with the Brazilian-fuel specifications for conventional gasoline and diesel fuels. The results show that the fast pyrolysis process represents an alternative technique for the production of biofuels from waste fish oil with characteristics similar to petroleum fuels.     

Rheology and fuel properties of slurries of char and bio-oil derived from slow pyrolysis of cassava pulp residue and palm shell

Three bio-oil samples, namely, raw bio-oil from pyrolysis of cassava pulp residue (CPR), separated oil phase and aqueous phase of bio-oil from pyrolysis of palm shell (PS), were used as suspending media for preparing slurries of bio-oil and the co-product char. Rheologies of all tested slurries exhibited pseudoplasticity with yield stress and the degree of this non-Newtonian behavior depended on such parameters as slurry type, solid concentration, particle size and slurry temperature. Overall, char/bio-oil slurries gave better fuel properties including higher pH and reasonably high calorific value (18?C32 MJ/kg) as compared to their bio-oil properties. Combustion of char/bio-oil slurries occurred in the temperature range similar to their solid char combustion and without ignition delay.