Increase In Torrefaction Temperature Research Articles

Torrefaction of pine wood in a continuous system and optimization of torrefaction conditions

Red pine wood particles were torrefied in a screw conveyor reactor system continuously having a capacity of 5 kg/hour. During torrefaction, operating conditions were very important. Changes in the reactor temperature and the reactor residence times had large influences on product yields. With increasing torrefaction temperature, the volatile matter and oxygen content of biomass decreased, while fixed carbon content and heating value greatly increased. Design-Expert software package was used for the design of experiments (DOE) and to carry out the statistical analysis according to the experimental results. The optimum biocoal yield of 56.59%, energy yield of 47.49%, higher heating value of 26 761.9 kJ/kg, hardgrove grindability index of 91.76, H/C ratio of 0.099, and O/C ratio of 0.312 were obtained at 299.71°C and 28.4 minutes (approximately 300°C and 30 minutes). The biocoal prepared in this work exhibited similar properties to selected Turkish lignites. It suggests that the biocoal can be used as a supplementary fuel for production of energy in coal-fired combustion systems, especially as an auxiliary fuel for existing power plants.

Torrefaction after pelletization (TAP): Analysis of torrefied pellet quality and co-products

Torrefaction is a thermal pretreatment method to increase the energy density and to decrease the grinding energy of biomass. In this study, the torrefaction of two types of commercially available wood pellets was carried out in the temperature range of 230–290 °C for 30 min residence time. Torrefaction produces both the solid fuel known as torrefied pellets and the volatile stream known as torgas. The torgas was further separated into condensable liquids, known as tor-liquid and non-condensable gases. The products yield, its compositions and fuel properties at various torrefaction temperatures were also determined. The increase in temperature reduced the torrefied pellet yield from 89 to 52%, while increased the condensable liquid yield from 5 to 23% within the torrefaction study condition. The heating value (24 MJ kg−1) and the volumetric energy density (12.5 GJ m−3) of torrefied pellets at 270 °C were comparable to that of coal for biopower. The increase in torrefaction temperature improved the hydrophobicity (resistance to water uptake), but adversely reduced the pellet density, hardness, and durability of torrefied pellets causing high susceptibility to breakage and fine generation during handling, transport, and storage. Further research is required to improve the quality of torrefied pellets for safe handling and storage. The non-condensable fraction of torgas was mainly composed of carbon dioxide, carbon monoxide, and traces of methane. The condensable liquid was rich in organic acids, ketones, furfural, and levoglucosan, which could be potentially transformed into high-value chemicals and other commercially viable products.

Torrefaction of oil palm fronds for co-firing in coal power plants

Torrefaction of biomass is a thermochemical process to enhance its fuel characteristics such as energy density and hydrophobicity. In this study, oil palm frond, a highly abundant agricultural waste in Malaysia is the feedstock of interest to investigate the influence of torrefaction temperature on its thermochemical properties. A single holding time of 30 min is used, with temperatures in the range of 200°C to 300°C (25°C increments). The mass and energy yields, as well as energy densification ratio are investigated, along with proximate analysis. Both mass and energy yield decreased with increasing torrefaction temperatures. The higher heating value (HHV) of torrefied oil palm fronds increased with increasing torrefaction temperature. Mild torrefaction temperatures (200°C - 225°C) showed insignificant improvements to HHV and slight reductions in mass and energy yields. Moderate and high torrefaction temperatures increased HHV significantly, while mass and energy yields continued to decrease. The optimum torrefaction temperature is determined to be at 250°C, giving the torrefied oil palm frond a respectable HHV of 26.62 MJ/kg, while maintaining an energy yield of 92.70%. This is within the range of HHV of coal, thus positioning torrefied oil palm frond as a suitable co-firing fuel for coal power plants.

Valorization of Waste Wood as a Solid Fuel by Torrefaction

The aim of this study was to investigate the optimal temperature range for waste wood and the effect torrefaction residence time had on torrefied biomass feedstock. Temperature range of 200–400 °C and residence time of 0–50 min were considered. In order to investigate the effect of temperature and residence time, torrefaction parameters, such as mass yield, energy yield, volatile matter, ash content and calorific value were calculated. The Van Krevelen diagram was also used for clarification, along with the CHO index based on molecular C, H, and O data. Torrefaction parameters, such as net/gross calorific value and CHO increased with an increase in torrefaction temperature, while a reduction in energy yield, mass yield, and volatile content were observed. Likewise, elevated ash content was observed with higher torrefaction temperature. From the Van Krevelen diagram, it was observed that at 300 °C the torrefied feedstock came in the range of lignite. With better gross calorific value and CHO index, less ash content and nominal mass loss, 300 °C was found to be the optimal torrefaction temperature for waste wood.

Thermal behavior and reaction kinetics analysis of pyrolysis and subsequent in-situ gasification of torrefied biomass pellets

Torrefaction followed by densification improves the heating value, grindability, and logistical treatment efficiency of biomass. Study of the pyrolysis and gasification of torrefied biomass pellets has great significance for the efficient conversion and utilization of biomass. In this study, the thermal behavior and reaction kinetics of pyrolysis and following in-situ CO2 gasification of torrefied corn stalk pellets were investigated in a macro-thermogravimetric analyzer. Torrefaction reduced the amounts of volatiles released during pyrolysis and the maximum pyrolysis rate of pellets decreased with the increase of torrefaction temperature. A three-pseudocomponent model applied for the pellet pyrolysis process suggested that the contribution of hemicellulose reduced as indicated by a decrease in activation energy, while lignin contributed more to the overall kinetics with the increased torrefaction temperature. The gasification of chars after the pyrolysis of torrefied pellets based on the nucleation and growth model indicated that as the torrefaction temperature increased, the gasification reactivity decreased, as implied by the evolutions of pore structures, ash compositions and graphitized crystal structures of the pellet pyrolysis chars. The higher activation energy increased the reaction resistance during the pellet gasification process. The results showed that torrefaction and densification together influenced the reaction behavior, reactivity and overall kinetics of biomass.

Torrefaction of densified mesocarp fibre and palm kernel shell

Abstract Mesocarp fibre and palm kernel shell (PKS) are widely used as fuels for boilers at palm oil mills to generate electricity. In the present study, the PKS and mesocarp fibre were densified under a controlled condition in prior to torrefaction process. Then, the briquettes were torrefied with various temperatures of 250–300 °C, residence time of 40 min and nitrogen flow rate of 1 l/min. In general, the torrefied mesocarp fibre briquettes were successfully produced regardless of torrefaction temperature, whereas the production of torrefied PKS briquettes was only feasible for torrefaction temperature of 250 °C, but the outer surface still remained brittle. The results show that an increase in torrefaction temperature causes a decrease in relaxed density and compressive strength of the torrefied mesocarp fibre briquettes. In terms of combustion properties, an increase in torrefaction temperature causes an increase in gross calorific value, fixed carbon content and ash content while volatile matter decreases. Besides, energy density of the torrefied mesocarp fibre briquettes does not change significantly with respect to the torrefaction temperature. Finally, the gross calorific value and moisture content were found to fulfill the requirements for commercialization as stated by international standards.

Improvement of the Energy Density of Rice Husk Using Dry and Chemical Treated Torrefaction

The main objective of this present study was to investigate the Torrefaction process of lignocellulose biomass rice husk produced in Ethiopia through dry and chemical treated Torrefaction. Torrefaction is a technology that a partial pyrolysis of biomass which is carried out under atmospheric pressure in a narrow temperature range of 200-300°C and under an inert environment which yields higher solid yield than pyrolysis. Three different Torre faction temperatures 230, 255 and 280°C with three different holding times 20, 40 and 60 minutes were considered using dry and chemical treated torrefaction. The result showed that a net reduction of the volatiles content, mass yield, moisture content, bulk density and atomic oxygen content correlate with increasing torrefaction temperature and reaction time, while atomic carbon content, higher heating value (HHV), fixed carbon content and energy density increase with higher torrefaction temperatures in both treatment cases. So, torrefaction temperature and holding time had a significant effect on torrefaction process of rice husk. Based on the findings of this study, temperature of 280°C and 60 min for dry torrefaction and 280 with a residence time of 40 min for chemical treated torrefaction could be suggested for an effective and proper torrefaction process to recycle the agricultural biomass. The energy density of dry torrefaction was enhanced by 120% and chemical torrefaction was enhanced by 127.4%. Therefore, the torrefied biomass becomes fuel sources which can be applied to replace with fossil fuel.

Torrefaction of Larix Kaempferi C. and Liriodendron Tulipifera L. Cubes: Impact of Reaction Temperature on Microscopic Structure, Moisture Absorptivity, and the Durability of Pellets Fabricated with the Cubes

Larch (LAR) and yellow poplar (YP) cubes were torrefied at 180, 220 and 260 ℃ for 50 min to determine the alterations in their structural and hydrophobic properties. Through microscopic observations, several cracks and crevices were found on the radial- and tangential-sectioned areas of the 260 ℃-torrefying YP cubes. On the tangential-sectioned areas, horizontal resin canal for LAR and ray cells for YP were darker than vertical cells. Moisture absorptivity (MA) measured for investigating the hydrophobicity of the torrefied LAR and YP cubes decreased with the increase of torrefaction temperature. However, no obvious differences were observed between the colors of the surface and internal parts or between the internal parts of the cubes visually at each torrefaction temperature. In addition, MA of the LAR and YP cubes was not significantly influenced by the depth of the cubes. Accordingly, it can be concluded that the carbonization level of the LAR or YP cubes is affected more by torrefaction temperature th...

Process modeling for torrefaction of birch branches

This work presents a complete biomass torrefaction model for Norwegian birch branches. The model can provide detailed distribution of both the main and by-products from the torrefaction process. Reduction in mass and energy yields as well as increase in heating value of the torrefied biomass with increasing torrefaction temperature are observed. Simulation results show good agreement with available experimental data in the literature. Furthermore, the overall energy consumption and the process energy efficiency can be also estimated, which is essential for process up-scaling. It reveals that drying accounts for 76-81% of the total heat demand. More importantly, the process energy efficiency reduces with increasing temperature thus torrefaction at high temperatures is not advisable. The information obtained from the model is important for industrialization and commercialization of the torrefaction process.

Characterization of torrefied biomass of five reforestation species (Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) in Costa Rica

Torrefaction can increase the energy yield of biomass for better utilization in bioenergy, but chemical changes occur during the pretreatment process. Wood residues of Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea were torrefied for three different time periods (8, 10, and 12 min) and three different temperatures (200, 225, and 250 °C). The mass loss, net calorific value, ash, volatiles, lignin, cellulose, extractives, and infrared spectra were evaluated. The results showed that the mass loss in torrefied biomass varied between 10% and 70%, ash content varied between 0.19 and 7.00%, and volatiles content varied between 63 and 85%. Net calorific value values varied between 17 and 23 MJ/kg, increasing with the increased torrefaction temperature. Cellulose varied between 49.85 and 67.57%. Lignin varied between 27.33 and 41.09%. The extractives varied between 3.70 and 16.86%. The change in the ratio of intensity (RI) for the bands identified using FTIR analyses showed that large changes occurred in hemicellulose components. The multivariate analysis showed that lignin, ash, extractives in hot water, volatiles, and mass loss were the variables that contributed most. The analysis of all these variables showed that torrefaction at 250 °C for 12 min presented the greatest biomass degradation. Torrefaction at 200 °C and 225 °C for 8, 10, and 12 min was optimal for thermal treatment of the biomass of these woody species.

Physical and Compression Properties of Pellets Manufactured with the Biomass of Five Woody Tropical Species of Costa Rica Torrefied at Different Temperatures and Times

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture content, water absorption, and compression force of torrefied biomass pellets of five wood species (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) under three torrefaction temperature conditions (light, middle, and severe) and three torrefaction times (8, 10, and 12 min). The results showed that the bulk density of the pellets was 0.90–1.30 g/cm3. The density variation of the pellets was higher with torrefaction at 250 °C. The moisture content decreased with increasing torrefaction temperature from 3% to 1%. Water absorption was lower in the pellets torrefied at 250 °C. The compression force was lower in the pellets torrefied at 250 °C with approximate loads of 700 N. Based on the above results, it was concluded that pellets made with biomass torrefied at 200 °C have better energy properties and evaluated properties. According to these results, pellets fabricated with the torrefied biomass of tropical species can be used in stove, gas, and hydrogen production because the pellet presents adequate characteristics.

Effect of torrefaction on physiochemical characteristics and grindability of stem wood, stump and bark

In this work, Norway spruce stem wood, stump and bark were torrefied in a bench scale tubular reactor at 225, 275 and 300°C with two residence times (30 and 60min). Effect of torrefaction on general properties, chemical composition, grindability and microstructure and morphology of biomass samples were studied. An increase in heating value and fixed carbon content of the torrefied biomass was observed for increasing torrefaction temperature and residence time. Chemical compositions of torrefied biomass samples considerably changed with increase of torrefaction severity. For the stem wood and stump, the relative hemicellulose content significantly decreased from respectively 42.3% and 29.8% to less than 1% after torrefaction at 300°C for 60min. The hemicellulose content of untreated bark decreased from 27.5% to 0.14% after torrefaction at the same conditions. Additionally, the cellulose content of the torrefied bark drastically decreased already to half the initial value at a torrefaction temperature of 275°C, with only trace amounts left in the 300°C torrefied products. The grindability of stem wood and stump were substantially improved after torrefaction treatment. The energy required for grinding stem wood and stump torrefied at 225°C decreased to respectively 87 and 70kWh/ton, which are less than 50% of the energy needed for grinding the untreated samples. For raw bark, much less grinding energy is required compared to those for raw stem wood and stump, and torrefaction has minor effects on the grindability of bark. The ground torrefied biomass samples have much smaller particles than those of the untreated ones. SEM analysis results show that particles from ground torrefied samples lose their fibrous structure with decrease of length-to-diameter ratios, compared to untreated biomass samples. It explains the shift in particle size distribution curves towards smaller particles as obtained from the sieving tests.

Process modeling and optimization for torrefaction of forest residues

This work aims to build a comprehensive biomass torrefaction model, which can provide a wide range of information essential for industrialization and commercialization of the process. Norwegian forest residue (birch branches) was chosen as feedstock. The model is capable of presenting detailed distributions of main and by-products from the torrefaction process. In addition, important fuel properties (ultimate analysis and heating value) of the main solid product after torrefaction can be predicted. The model is validated and simulation results show good agreement with available experimental data in the literature. Reduction in mass and energy yields as well as improvement in heating value of torrefied biomass with increasing torrefaction temperature are observed. Trends for carbon, oxygen and hydrogen contents are also consistent with other experimental works. Moreover, overall energy consumption and process energy efficiency can be estimated from the model. It reveals that drying accounts for 76–80% of the total heat demand. Furthermore, the process energy efficiency reduces with increasing temperature, thus torrefaction at high temperatures is not advisable. More importantly, process optimization shows that optimal conditions for torrefaction of birch branches are 30 min holding time and a temperature between 275 and 278 °C.

Improving hydrocarbon yield by two-step pyrolysis of pinewood in a fluidized-bed reactor

Two-stage fast pyrolysis of pinewood, was investigated with and without catalysts in a fluidized-bed reactor. The method is using low-temperature pyrolysis (torrefaction) to remove unfavorable compounds firstly and then using high-temperature catalytic pyrolysis to produce hydrocarbons. The effects of torrefaction temperature, residence time and atmosphere on product distribution were investigated. The results show that the acidity of produced liquids reduced with increasing torrefaction temperature and residence time. Torrefaction pretreatment of pinewood reduced the yields of acetic acid and guaiacol effectively during catalytic pyrolysis. The highest aromatic yield was obtained with torrefied pinewood at 250°C, which was boasted 30% of that without torrefaction. Besides, torrefied biomass can obviously reduce coke deposition on ZSM-5 in the catalytic pyrolysis process compared with raw pinewood. Therefore, the two-step pyrolysis can be considered as a more effective and promising method for producing high-quality liquid fuels and chemicals.

Effect of torrefaction temperature on properties of Patula pine

The objective of this work was to study the effect of torrefaction temperature on properties of patula pine (Pinus patula) wood that could be of interest for further thermochemical processing. Torrefaction temperature was varied from 200 to 300 °C for 30 minutes using a batch spoon type reactor. Raw and torrefied materials were characterized for proximate and ultimate analyses, thermogravimetry, and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Results showed that torrefied pine has greater higher heating value and chemical exergy due to the reduction of O/C and H/C ratios. Compared with raw biomass, the material torrefied at 200 and 250 °C did not present significant changes in chemical composition and thermal behavior. Conversely, material torrefied at 300 °C did show important changes in both chemical composition and thermal behavior. Py-GC/MS results suggested that the main constituents of biomass, i.e., hemicellulose, cellulose and lignin, suffer a progressive thermal degradation with increase in torrefaction temperature.

Effect of torrefaction on the properties of rice straw high temperature pyrolysis char: Pore structure, aromaticity and gasification activity

The influence of torrefaction on the physicochemical characteristics of char during raw and water washed rice straw pyrolysis at 800–1200°C is investigated. Pore structure, aromaticity and gasification activity of pyrolysis chars are compared between raw and torrefied samples. For raw straw, BET specific surface area decreases with the increased torrefaction temperature at the same pyrolysis temperature and it approximately increases linearly with weight loss during pyrolysis. The different pore structure evolutions relate to the different volatile matters and pore structures between raw and torrefied straw. Torrefaction at higher temperature would bring about a lower graphitization degree of char during pyrolysis of raw straw. Pore structure and carbon crystalline structure evolutions of raw and torrefied water washed straw are different from these of raw straw during pyrolysis. For both raw and water washed straw, CO2 gasification activities of pyrolysis chars are different between raw and torrefied samples.

Influence of torrefaction on the characteristics and pyrolysis behavior of cellulose

The influence of torrefaction on cellulose structural characteristics and the resulting pyrolysis behavior was investigated in this study. Torrefaction reduced O/C ratio in cellulose and increased its high heating value. The crystallinity of cellulose increased slightly first and then decreased sharply with the increase of torrefaction temperature, which could be ascribed to competitive degradation between crystalline region and amorphous region, as indicated by 13C CP/MAS NMR analysis. Besides, the cleavage of β-1,4-glycosidic bond and the dehydration of hydroxyl were the major reactions occurring in torrefaction. Avrami-Erofeev model was found to be the most suitable kinetic reaction model for explaining the thermogravimetric weight loss during the pyrolysis of the raw and torrefied cellulose. A distributed activation energy model based on Avrami-Erofeev model was subsequently used to reveal the pyrolytic kinetics. It was found that the changes in cellulose structure influenced the kinetic parameters greatly. Torrefaction also changed pyrolytic product distribution. The yields of furfural, alicyclic ketones and anhydrosugars increased while that of 5-hydroxymethyl-furfural decreased as torrefaction temperature increased.

Thermo-physical, Chemical and Structural Modifications in Torrefied Biomass Residues

The study examined the modifications in the thermo-physical and chemical structure of Tectona grandis (TK) and Sorghum bicolour stalk residues that occurred during the process of torrefaction. The analytical techniques used are Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) alongside some basic data characterisation techniques. Data from specific FTIR spectra were used quantitatively in the evaluation of total crystalline and lateral order indices (TCI and LOI) for cellulose and syringyl to guaiacyl (S/G) ratio in lignin. The indices and the ratio were applied in monitoring modifications in cellulose crystallinity and lignin structure. The S/G ratio for untreated TK dropped significantly from 0.6 to 0.12 after torrefaction. An appreciable rise in the TCI and LOI was observed for both samples following the thermochemical conversion process. A distinct thermal decomposition pathway, which widen in discrepancy with increasing torrefaction temperature, was established between untreated and torrefied biomass residues via the TGA. The basic data analysis demonstrated a significant rise in the calorific value of torrefied biomass; approximately from an average of 19.1–26.8 MJ/kg.

TORREFACTION OF PALM BIOMASS BRIQUETTES AT DIFFERENT TEMPERATURE

The climate change has driven towards transformation from the high energy dependence on fossil fuel to inexhaustible renewable energy such as solar, wind, mini hydro and biomass. In Malaysia, abundant of palm biomass residues are produced during the processing of fresh fruit bunch. Therefore it is inevitable to harness these bioenergy sources in order to prevent waste accumulation at adjacent to palm mills. In order to utilize such bioenergy sources and to cope with the fast growing demand of energy, combination technique of densification and torrefaction is one of the potential ways to be practised. In the present study, the physical and combustion properties of torrefied empty fruit bunch (EFB) briquettes were investigated experimentally with constant nitrogen flow rate of 1 l/min , for various torrefaction temperatures (225-300). Before torrefaction process, EFB briquettes were initially produced under controlled condition with compaction pressure of 7 MPa and briquetting temperature of 150. In general, the torrefied EFB briquettes were successfully produced in the present study. The results show that an increase in torrefaction temperature from 225 to 300 causes a significant increase in gross calorific value (from around 17400 kJ/kg to 25000 kJ/kg), fixed carbon content (from 16.2% to 46.2%) and ash content (from 2.4% to 17.2%). On the other hand, relaxed density and volatile matter decrease, from 1017 kg/m3 to 590 kg/m3 and from 73.1% to 29.7%, respectively. As a conclusion, the gross calorific value and fixed carbon content are improved due to torrefaction. In addition, it was found that gross calorific value and moisture content of the torrefied EFB briquettes fulfil the requirement for commercial briquette production as stated by DIN51731 (gross calorific value>17500 kJ/kg and moisture content <10%).

Thermogravimetric and calorimetric characteristics during co-pyrolysis of municipal solid waste components

The thermogravimetric and calorimetric characteristics during pyrolysis of wood, paper, textile and polyethylene terephthalate (PET) plastic in municipal solid wastes (MSW), and co-pyrolysis of biomass-derived and plastic components with and without torrefaction were investigated. The active pyrolysis of the PET plastic occurred at a much higher temperature range between 360°C and 480°C than 220–380°C for the biomass derived components. The plastic pyrolyzed at a heating rate of 10°C/min had the highest maximum weight loss rate of 18.5wt%/min occurred at 420°C, followed by 10.8wt%/min at 340°C for both paper and textile, and 9.9wt%/min at 360°C for wood. At the end of the active pyrolysis stage, the final mass of paper, wood, textile and PET was 28.77%, 26.78%, 21.62% and 18.31%, respectively. During pyrolysis of individual MSW components at 500°C, the wood required the least amount of heat at 665.2J/g, compared to 2483.2J/g for textile, 2059.4J/g for paper and 2256.1J/g for PET plastic. The PET plastic had much higher activation energy of 181.86kJ/mol, compared to 41.47kJ/mol for wood, 50.01kJ/mol for paper and 36.65kJ/mol for textile during pyrolysis at a heating rate of 10°C/min. H2O and H2 peaks were observed on the MS curves for the pyrolysis of three biomass-derived materials but there was no obvious H2O and H2 peaks on the MS curves of PET plastic. There was a significant interaction between biomass and PET plastic during co-pyrolysis if the biomass fraction was dominant. The amount of heat required for the co-pyrolysis of the biomass and plastic mixture increased with the increase of plastic mass fraction in the mixture. Torrefaction at a proper temperature and time could improve the grindability of PET plastic. The increase of torrefaction temperature and time did not affect the temperature where the maximum pyrolytic rates occurred for both biomass and plastic but decreased the maximum pyrolysis rate of biomass and increased the maximum pyrolysis rate of PET plastic. The amount of heat for the pyrolysis of biomass and PET mixture co-torrefied at 280°C for 30min was 4365J/g at 500°C, compared to 1138J/g for the pyrolysis of raw 50% wood and 50% PET mixture at the same condition.