Maximum Tar Yield Research Articles

Compositional and experimental investigation of the effect of reactor temperature on softwood and hardwood pyrolysis

PurposeThis study aims to investigate the effect of reactor temperature on softwood and hardwood pyrolysis. Experiments are performed at six temperature levels ranging from 300 to 800°C under N2 atmosphere. The weights of char, tar and gas yields produced were measured and recorded in percentage of initial weight of the pyrolyzed samples. Results of the study showed that hardwood produces maximum char, tar and gas yields of 41.02 per cent at 300°C,44.10 per cent at 300°C and 56.86 per cent at 800°C, respectively, whereas softwood produces maximum yields of 30.10 per cent at 300°C, 28.25 per cent at 300°C and 68.73 per cent at 800°C, respectively. Proximate analysis shows that volatile matter, fixed carbon, ash content and moisture content of hardwood are 74.83, 14.28, 2.81 and 8.08 per cent, respectively, and that of softwood are 79.76, 12.65, 0.98 and 6.61 per cent, respectively. Result of the elemental analysis results shows that the carbon, hydrogen, nitrogen, oxygen and sulphur contents for hardwood are 52.20, 6.45, 0.68, 39.64 and 1.03 per cent, respectively, and that of softwood are 45.95, 4.57, 0.56, 48.13 and 0.79 per cent, respectively. The higher heating value of hardwood and softwood are 21.76 and 16.50 kJ/g respectively. This study shows that char and tar yields decrease with increase pyrolysis temperature, whereas gas yield increases as pyrolysis temperature increases for the wood samples considered. At all temperatures considered in this study, gas yields are higher than tar and char yields for softwood, whereas for hardwood, tar yield decreases with increase in temperature with accompanying increase in gas yield.Design/methodology/approachExperiments are performed at six temperature levels ranging from 300 to 800°C under N2 atmosphere.FindingsAt all temperatures considered in this study, gas yields are higher than tar and char yields for softwood, whereas for hardwood, tar yield decreases with increase in temperature with accompanying increase in gas yield.Originality/valueResults of the study showed that hardwood produces maximum char, tar and gas yields of 41.02 per cent at 300°C,44.10 per cent at 300°C and 56.86 per cent at 800°C, respectively, whereas softwood produces maximum yields of 30.10 per cent at 300°C, 28.25 per cent at 300°C and 68.73 per cent at 800°C, respectively.

Catalytic pyrolysis of coal particles in a fluidized bed: Experiments and modeling

ABSTRACTCoal as a form of fossil fuel may be utilized in two thermochemical techniques: directly by combustion of coal particles and indirectly by converting it into valuable products. In this research, a kinetic model of coal devolatilization has been developed based on the Arrhenius expression. To validate the model, an experimental study also has been performed in a drop-tube fluidized bed. There was reasonably good agreement between modeling data and experimental data obtained from single-tube fluidized bed. The effects of reaction temperature on the pyrolysis products and fuel conversion were studied. As a result, the maximum tar yield obtained was 28.3 (%) at 400° C. An increase in activation energy was led to a relative decrease in the fuel conversion maybe due to a decrease of heating rate.

Catalytic pyrolysis of corn straw fermentation residue for producing alkyl phenols

Phenolic-oil can be upgraded by etherification with methanol to decrease the polarity and acidity of the product oil. However, alkoxy phenols have an inhibiting effect to the etherification of alkyl phenols in the phenolic mixture. So, it is very important to produce alkyl phenols with high selectivity and extremely low content of alkoxy phenols, through a catalytic pyrolytic process. Herein, the effects of HZSM-5, NaY, and KH2PO4/AA (KH2PO4 loaded on activated Al2O3) on the pyrolysis of corn straw fermentation residue are investigated, for producing alkyl phenols high efficiently. KH2PO4/AA is found to be the best catalyst in promoting the formation of alkyl phenols and in inhibiting alkoxy phenols. Under the catalysis of KH2PO4/AA, the tar yield increases with rising temperature, and reaches to the maximum tar yield of 13.7% at 500 °C, and then declines with further increasing temperature. The tar obtained under optimized reaction conditions, nearly consists of 50% of alkyl phenols and over 23% of aliphatic hydrocarbons with zero content of alkoxy phenols. K3Al2(PO4)3 is generated from the solid phase reaction between KH2PO4 and Al2O3, through which alkoxy phenols can be high selectively adsorbed and activated, and thus leads to the formation of alkyl phenols.

Characterization and pyrolysis behaviors of sunflower stalk and its hydrolysis residue

AbstractSunflower stalk (SS) and its alkaline hydrolysis residue (SHR) were characterized by means of chemical component analysis, Fourier Transform infrared (FT‐IR) spectrometer and scanning electron microscope (SEM), and their pyrolysis behaviors were investigated by a thermal gravimetric (TG) analyzer, a self‐designed pyrolysis apparatus and a pyrolysis‐chromatograph/mass spectrometer (py‐GC/MS). The results showed that the chemical components, chemical structures and surface morphologies of SS and SHR are notably different as a result of mild delignification during hydrolysis process. TG/DTG analyses indicated that SHR is easier to be decomposed than SS. The temperature of the maximum weight loss rate of SHR is lower than that of SS. The pyrolysis process of SS and SHR could be described with first‐order kinetics model, and the activation energy values are 78.36 and 73.86 kJ/mol, respectively. The results of pyrolysis in fixed bed reactor showed that SHR has higher tar yield but lower gas yield compared with SS. SHR and SS have maximum tar yields of 39.9% and 37.9% at 540 °C and 600 °C, respectively. Gas yields increase with temperature and become more obvious at above 600 °C. Py‐GC/MS analysis exhibited that the main compounds in the pyrolysate includes ketones, aldehydes and phenols. The relative content of phenols in the pyrolysate of SHR is the highest (20.97%) and is remarkably higher than that of SS. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Fast devolatilization characteristics of ‘low cost’ biomass fuels, wood and reed. Potential feedstock for gasification

Fast devolatilization of woody (mixture of softwoods) and herbaceous (reed) biomasses has been studied in a heated foil reactor coupled to an FTIR spectrophotometer. Biomass fuels were chosen based on their potential for contributing to power generation on an industrial scale through gasification in The Netherlands. Heating rate (600°C/s) and holding time (10s) at peak pyrolysis temperature were chosen to correspond to conditions encountered in industrial processes. The effect of peak pyrolysis temperature on pyrolysis products was investigated. Particular emphasis was given to tar collection, and subsequent gravimetric quantification. The results indicated a strong total weight loss increase with temperature, to reach an asymptote char yield of 16.7wt.% at 800°C and of 32.4wt.% at 700°C for wood and reed, respectively. Reed primary devolatilization reactions ceased at lower temperatures compared to wood. The latter was confirmed by the lower activation energy of reed (32.1kJ/mol) compared with that of wood (38.4kJ/mol) during extrapolation of kinetic data from the fast devolatilization experiments. CO2 dominated the gaseous products released at lower temperatures (<700°C) while CO became predominant at higher pyrolysis temperatures (>700°C) reaching a maximum of 19.1wt.% and 18wt.% for wood and reed, respectively, at 1000°C. Maximum tar yields of 38.8wt.% (d.b.) of dry wood and 23.3wt.% (d.b.)of dry reed were able to be recovered at 600°C. An overall mass balance of approximately 90wt.% (d.b.) for both biomass fuels was obtained at high (900–1000°C) pyrolysis peak temperatures.

Pyrolysis of Hesigewula Lignite and Identification of Aromatics in the Pyrolysis Tar by Gas Chromatography-Mass Spectrometry

Hesigewula lignite was studied by fixed bed pyrolysis to achieve the optimal conditions for pyrolysis under low temperature. It was found that the maximum tar yield 6.60wt% under 50 mL/min of gas carrier, 500 °C, 0.5 MPa and holding for 15 min. By column chromatography, we extracted aromatics of the tar generated under the optimal condition. Aromatics with 2 and 3 rings are predominant in the tar from Hesigewula lignite pyrolysis by gas chromatography-mass spectrometry analysis (GC-MS), however, the tetracyclics and above compounds were very few. Naphthalene and its derivatives had pivotal position in aromatics.

Effect of tetrahydrofuran extraction on lignite pyrolysis under nitrogen

Based on the host-guest model of coal, the fixed and mobile phase of coal which can be separated by solvent extraction will present different characteristics during thermal conversion. The pyrolysis of Xilinguole and Huolinhe lignites and their extraction residues with tetrahydrofuran were investigated at 450–700°C under N2 atmosphere. The results indicate that the temperature at the maximum tar yield of extraction residue is lower than that of coal. Compared with raw coal, residue pyrolysis process exhibits lower water yield, higher gas yield and similar char yield. Similar H2 yield, more CO and CO2 yields but less CH4 yield are obtained during residue pyrolysis than those in coal pyrolysis. GC analysis of tar shows that contents of phenols and mononuclear aromatics from residue tar are higher than those from raw coal tar. 1H NMR and 13C NMR of tar indicate that the tar from residue has higher aromaticity factor than that from coal. The total acidity and acid distribution in raw coal, extraction residue and their chars obtained at 600°C show that phenolic OH is the main oxygen contained group in extract. The activity of O in coal could be improved by extraction, and more O will be translated to OH during pyrolysis.

Hot Water Extraction and Fixed Bed Pyrolysis for Bitumen Recovery of an Indonesian Oil Sand

An Indonesian oil sand were studied by hot water extraction and fixed bed pyrolysis for bitumen recovery. It was found that the concentration of alkali and temperature both had effects on the yield of water extraction. But the maximum yield was only 12.74wt% under the investigated condition due to its oil-wet structure. As to pyrolysis in fixed bed reactor, the influence of holding time, flow rate of gas carrier and temperature on the tar yield were considered. The maximum tar yield was 17.01wt% under 140mL/min of gas carrier, 480°C, 0.1MPa and holding for 40min. The results show that pyrolysis is more suitable for bitumen recovery of the oil sand compared with hot water extraction.

Study on the Process Analysis and Kinetics during the Co-Pyrolysis of Low Rank Coal and Enteromorpha

The pyrolysis of low rank coal (LRC) , enteromorpha (EN) and their mixture were carried out in a special prolysis equipment. The experiments showed that the maximum tar yield of blends was 11.39% with a EN ration of 30%, which increased by 28.61% compared to LRC pyrolysis alone and 8.87% compared to calculated value. The thermogravimetric analysis (TGA) of LRC, EN and their mixture indicated that there was significant synergistic effect in the co-pyrolysis process of LRC and EN during 240~750°C. The relative maximum value of synergistic effect was 18.5%. Kinetics analysis showed there was compensation effect between activation energy and pre-exponential factor of co-pyrolysis. The mix of LRC and EN enhanced the reaction activity and lowers the reaction rate. Synergistic effect mainly was reflected in enhancing the reaction activity of co-pyrolysis.

Experimental Research of the Fast Pyrolysis Characteristics for Lignite at Medium Temperature

The lignite fast pyrolysis characteristics at medium temperature was tested ranging from 400°C to 700°C, and the pyrolysis product component was on-line analyzed by using gas chromatograph-mass spectrometer computer and fourier transform infrared spectroscopy. Besides, two different algorithms were used to evaluate the test error. The results show that the maximum experimental error is no more than 6.2%. In addition, the optimum pyrolysis temperature is about 550°C which causes the maximum tar yield with an obvious increases of heat value. The gas component concentration shows divergences because of the tar decomposition at higher temperature. Finally, the proximate analysis of char was tested, which shows that the ash and fixed carbon of char increase with the temperature addition.

Thermal analysis and products distribution of dried sewage sludge pyrolysis

Pyrolysis behavior of dried sewage sludge was studied by thermogravimetric–Fourier transforms infrared analysis (TG–FTIR) and differential scanning calorimetry (DSC) to investigate thermal decomposition and kinetics analysis. A tubular pyrolyzer was used to explore the production distribution of dried sewage sludge pyrolysis under different runs. The results showed that two weight loss peaks were presented in pyrolysis reaction in the ranges of 186–296°C and 296–518°C, and the activation energy of each stage was 82.284kJmol−1 and 48.342kJmol−1, respectively. The main gases identified by FTIR analysis were CH4, CO2, CO and organic volatile compounds such as aldehydes, acids, alcohols and phenols. Under fast pyrolysis of dried sewage sludge, the maximum tar yield obtained was 46.14% at the temperature of 550°C. The concentrations of all gases increased steadily with increasing pyrolysis temperature from 450°C to 650°C except for CO2.

Modeling Effects of Operating Conditions on Biomass Fast Pyrolysis in Bubbling Fluidized Bed Reactors

This numerical study investigates the effects of operating conditions on the product yields of a biomass fast pyrolysis reactor. A numerical approach that combines a multifluid model and pyrolysis reaction kinetics was applied to simulate the biomass fast pyrolysis process in a bubbling fluidized-bed reactor. The model was first validated using experimental data, and a parametric study was conducted. Operating parameters were varied to characterize their effects on the final product yields. For the reactor studied, it was found that the maximum tar yield could be obtained by maintaining both the wall temperature and the inlet temperature of nitorgen at approximately 800 K. The inlet velocity of nitrogen at about 0.6 m/s also produced favorable results. Simulations indicated that the optimal biomass particle diameter and the feeding rate were 900 μm and 1.92 kg/h, respectively, for tar production. Larger sand particle diameter and deeper initial sand bed also favored the tar yield.

Comparative study of pyrolysis behaviors of corn stalk and its three components

To better understand the pyrolysis mechanism for further process optimization, the pyrolysis characteristics of corn stalk and its three major components (i.e. hemicellulose, cellulose and lignin) were investigated and compared by amplifying experiments in a tubular furnace at different temperatures (from 300°C to 900°C). The distributions of pyrolysis products (in terms of gas, tar and char), the influence of temperature, the impacts and contributions of each single component on the pristine biomass pyrolysis were discussed in depth. It was found that, for each sample pyrolysis, the pyrolysis temperature played a huge role on the yields and properties of different products. Optimal temperatures for maximum tar yield were found to be between 450°C and 500°C. The high temperature (>600°C) was favorable to generate gas products, accompanied by a reduction of tar and char yields. Because of their unique chemical structures, profound differences about the characteristics of pyrolysis products from each component were drawn from the analysis results. Among the three components, hemicellulose produced the highest CO2 and H2 yields, cellulose owned the highest CO yield, while lignin generated significantly more CH4. As for tars, hemicellulose tar mainly contained ketones, acids and furans, cellulose tar displayed higher aldehydes and furans, lignin tar was dominated by monomeric phenols and 2,3-dihydro-benzofuran. In addition, the SEM images also revealed the marked differences in the surface morphology of the chars.

Studies on Rapid Pyrolysis Characteristics of Huainan Coal

This paper aims to investigate the rapid pyrolysis characteristics of Huainan coal using a tube furnace. Influence of temperature on yields and compounds of tar and char are tested. The result shows that aliphatic chains break gradually with increasing pyrolysis temperature. This leads an increase in aromaticity. Maximum tar yields were obtained at about 550°C, the char yields decreased and the gas yields increased with the pyrolysis temperature. The tar was isolated to aliphatic hydrocarbon aromatic hydrocarbon, non hydrocarbon and asphaltene, and characterized by chromatography-mass spectrometry (GC/MS). The main content of tar include normal alkanes from C16-C30, two-,three- and four-ring aromatic hydrocarbons and alkyl-substituted hydroaromatic derivatives of polycyclic, phenols, indoles, quinines esters and others compounds.

The Comparative Study of Honghe Lignite Pyrolysis under the Atmosphere of Methanol and Nitrogen

The pyrolysis of Honghe lignite was investigated on low heating rate (about 20°C/min) conditions in a fixed bed reactor with 10g fed in. Nitrogen was used as carrier gas operating at the range from 50 to 200ml/min. And, the temperature was tested from 440 to 560°C, the pressure ranges from 0.1MPa to 1.2MPa. The yields of coal tar, char, water and gas were obtained in experiments. The maximum coal tar yield of 9.77% (dry coal) was achieved at 520°C, 50ml/min nitrogen flow rate, pressure 0.4MPa and 20 minutes holding time. Then methanol was injected in the system at the preheat temperature 240°C(a little higher than its critical temperature). The methanol flow rate, pressure and holding time were also taken into consideration. And the results were compared with those obtained in pyrolysis under nitrogen atmosphere. It showed that higher liquid yield with lower yields of char, gas and loss were obtained with the presence of methanol, but the differences of char yields were slight. The total sulfur removal for methanol presence is considerably higher than the absence of methanol in pyrolysis. Considering the mild conditions of the pyrolysis with presence of methanol, this method may be an appropriate way to make use of the lignite efficiently and environmentally.

Pyrolysis of Phragmites Australis and characterization of liquid and solid products

In this study, an investigation was conducted in order to find out whether Phragmites Australis can be utilized in various ways by means of pyrolysis in a tubular fixed-bed system. To this end, a study was carried out to investigate the effect of the pyrolysis temperature, heating rate, sweep gas flow rate and the size of Phragmites Australis on pyrolysis. The maximum tar yield was achieved at 550 °C pyrolysis temperature, a heating rate of 25 °C/min and a sweeping gas flow rate of 100 ml/min. The average chemical composition of the tar obtained was established by elemental analysis and its structural analysis was conducted by 1H NMR spectrum and FTIR spectrum. Moreover, elemental and proximate analyses were conducted of the chars obtained in all experimental conditions to collect information on their structure.

Pyrolysis of peat: Product yield and characterization

Pyrolysis of peat obtained from Yenicaga, Bolu, Turkey was conducted in a fixed-bed tube furnace under various conditions, and variations in the structure of the char, tar and gas products were examined. The chars produced were studied by proximate and ultimate analyses. The maximum tar yield of 20.41% was obtained at a heating rate of 20 °C/min, a temperature of 450 °C, a sweeping gas flow rate of 100 ml/min and a 0.5–2.0 mm size range. The chemical composition of the tar was examined by elemental analysis, FTIR spectroscopy, 1H-NMR spectroscopy and column chromatography. The chemical composition of the tar with dense aliphatic structure was established to be CH1.22O0.25N0.02. The composition of the gases obtained at a heating rate of 20 °C/min for the 0.5–2.0 mm size range was examined by gas chromatography.

Low Temperature Pyrolysis of an Australian Brown Coal in a Fluidised Bed Reactor

AbstractThe pyrolysis of Loy Yang coal was investigated under rapid heating conditions in a fluidised bed with a feed rate of 10g/h. Nitrogen was used as the fluidising gas operating at fives times the minimum fluidising velocity. The yields of tar, total volatile matter and C1‐C3 hydrocarbons are obtained for pyrolysis temperatures between 300 to 600°C. A maximum tar yield of 24.3% w/w (dry ash‐free coal) was achieved at 550°C and 1.82 s gas residence time. Fourteen fractions were identified in the tar dissolved in methanol. Yields of C1‐C3 hydrocarbons increased with increasing temperature to 3% w/w at 600°C. Elemental analysis showed that the composition of char and the tar yields were strongly dependent on temperature. The effects of gas residence time and feed particle size were also investigated.

EFFECTS OF HEATING RATE AND PARTICLE SIZE ON THE PRODUCTS YIELDS FROM RAPID PYROLYSIS OF BEECH-WOOD

ABSTRACT Effects of pyrolysis temperature (300–1000 °C), heating rates (100, 500, 1000, and 10,000 °C/s), and particle sizes (53–63,104–120,177–270, and 270–500 urn) on the yields and formation rates of tar, light oils, total gases, and char from pyrolysis of beech-wood under 1 atm helium pressure were studied. Wood particles were pyrolyzed in strips of stainless steel wire mesh in a captive sample apparatus; and yields of products were measured in weight percent of original wood as a function of temperature for different heating rates and particle sizes. The overall weight loss achieved from pyrolysis of this wood was about 90%. The total yields of tar and light oils from pyrolysis of this wood accounted for up to 80% of the original wood above 400 °C. Due to the post-pyrolysis reactions of tar and light oils, the tar and light oils yields go through a maximum with pyrolysis temperature for all particle sizes and most heating rates studied here. As particle size increases from 53–63 μm to 270–500 μm the maximum tar yield decreases from 53% to about 38%. The maximum tar yield also decreases with increasing the heating rate from 70% at 100 °C/s to 48% at 10,000 °C/s heating rate. Theses results indicate that as the intra-panicle post-pyrolysis cracking reactions of tar increases at higher heating rates and with larger particles the tar yield decreases. Tar was also analyzed with GPC for the effects of above pyrolysis parameters on the tar molecular weight. The tar average molecular weight. remains relatively constant (Mw = 300 amu, Mn = 155 amu, and Mz = 483 amu) under helium atmosphere with pyrolysis temperature at 1000 °C/s heating rate and with 53/63 u m particle size. The average molecular weight of tar does not significantly varies with heaung rate, but it decreases as the particle size increases.

The potential of hydropyrolysis as a route for coal liquefaction

The use of sulphided molybdenum (Mo) as a dispersed catalyst enables tar yields of ∼ 60% daf coal to be achieved for bituminous coals (80-83% dmmf C) in fixed-bed hydropyrolysis using relatively low-severity conditions. Sulphur-containing Mo precursors, such as ammonium dioxydithiomolybdate are the most effective, Mo concentrations 0-2% being required to achieve maximum tar yield. Ion-exchange preparation procedures offer the potential of improving catalyst dispersions, and concentrations as low as 0-02% are effective when Mo is ion-exchanged onto coals coated with hydrous titanium oxides. Iron sulphides are much less effective than in direct liquefaction because of the higher heating rates used in hydropyrolysis. Low-rank coals can yield up to 50% tar without catalyst, and improvements in yield on catalyst addition are considerably less than bituminous coals