Effect Of Torrefaction Temperature Research Articles

Production of biochars from textile fibres through torrefaction and their characterisation

In this study, the utilization of textile fibres as energy feedstock in the form of biochar was investigated depending on the fibre type. The biochars were produced from waste natural and synthetic fibres and its blends. For this purpose, different types of textile fibres (cotton, viscose, polyester, acrylic) and their blends (cotton/polyester, acrylic/wool, acrylic/polyester, acrylic/viscose) were torrefied at temperatures between 300 and 400 °C. The effects of torrefaction temperature and fibre type on biochar yield and biochar properties (fuel properties, morphological and structural properties and combustion characteristics) were investigated. The results showed that the temperature had a significant effect on biochar yield whereas the fibre type was the only significant factor on energy densification ratio and biochar properties. The torrefaction of tested fibres and blends resulted in an energy-intensive solid fuel, having a negligible amount of ash and sulphur. Although torrefied acrylic based textile fibres had similar H/C and O/C ratios to bituminous coal, it was concluded that high nitrogen contents will limit their usage as fuel. Overally, this study showed that torrefaction of cotton and cotton/polyester textile wastes is a promising process for the production of a solid fuel, which can be used as a substitute fuel in coal/waste co-firing systems.

Oxidative torrefaction of spruce-pine-fir sawdust in a slot-rectangular spouted bed reactor

A slot-rectangular spouted bed (SRSB) reactor was employed to torrefy spruce-pine-fir sawdust in an oxidative atmosphere. The effects of torrefaction temperature (240–300 °C) and feed-gas oxygen concentration (3–9 vol.%) on torrefaction performance and solid product properties were investigated. Adding oxygen in the feed-gas led to more uniform temperature distributions in the SRSB reactor, and was a promising way to achieve stable continuous operation. The mass fraction of cyclone-caught torrefied biomass increased, whereas the mass fraction of torrefied biomass remaining in the reactor decreased, with increasing oxygen concentration and temperature. In oxidative torrefaction, biomass weight loss was 15.4–46.4%, while energy yield was 61.2–99.4%. The effects of oxygen concentration on the weight loss, energy yield and torrefied biomass properties were more significant at 300 °C than at 240 °C. The torrefied sawdust also had greater HHV and contained less volatiles, more carbon, less oxygen and less hydrogen than the raw biomass.

Influence of torrefaction with Mg-based additives on the pyrolysis of cotton stalk

The study presented an approach to introduce Mg-based additives into cotton stalk for strengthening deoxygenation effect during torrefaction. Then catalytic pyrolysis of torrefied feedstock with Mg-based additives residue as catalyst was performed at 550 °C for 10 min in a fixed-bed reactor. The effects of torrefaction temperature (200, 230, 260, 290, 320, 350 °C), type of Mg-based additive (MgO and MgO-K2CO3), mass ratio of additive to biomass (0.5, 1 and 2) on pyrolysis were investigated. The results indicated that yields of bio-char and bio-oil significantly increased and decreased with torrefaction temperature rising to 350 °C. MgO inhibited pyrolysis bio-char yield increase with torrefaction severity. MgO-K2CO3 increased H2 yield a lot from 1.39 to 3.67 mmol/g. It also effectively improved the aromatic hydrocarbons in bio-oil and the reduction of acids. A maximum aromatic hydrocarbons yield of 16.05% was obtained with MgO-K2CO3 (the mass ratio of 0.5:1) at torrefaction temperature of 320 °C.

Utilizing Downdraft Fixed Bed Reactor for Thermal Upgrading of Sewage Sludge as Fuel by Torrefaction

A lab-scale downdraft fixed bed reactor was used for the study of sewage sludge, a non-lignocellulosic biomass, torrefaction to enhance the thermochemical properties of sewage sludge. The torrefaction was carried out for a temperature range of 200–350 °C and a residence time of 0–50 min. Degree of torrefaction, torrefaction index, chemical exergy, gas analysis, and molar ratios were taken into account to analyze the torrefied product with respect to torrefaction temperature. The effect of torrefaction temperature was very pronounced and the temperature range of 250–300 °C was considered to be the optimum torrefaction temperature range for sewage sludge. Chemical exergy, calorific value and torrefaction index were significantly influenced by the change in the relative carbon content resulting in decrease of the O/C and H/C molar ratios.

Kinetic, volatile release modeling and optimization of torrefaction

Torrefaction is a thermal pretreatment of biomass process carried out in the temperature range of 473–573K under inert atmosphere to enhance fuel properties. In the present study, different biomass are analyzed through numerical simulations and optimized parameters are reported. Kinetic, volatile release and solid composition models are coupled & simulated. Results of the kinetic model are verified by comparing with experimental results. Then, compositional coefficients for volatiles of different biomass are found by volatile release model. Further, volatile release model used to calculate composition of releasing volatiles. By means of mass conservation, composition of remaining solid product is estimated. Effect of torrefaction temperature, residence time and nature of biomass on moisture content of biomass, volatiles release, hydrogen to carbon (H/C) & oxygen to carbon (O/C) molar ratios, energy densification and elemental compositions are given. It is found that during mild torrefaction regime 508–548K; water removal and energy densification increases more rapidly as compared to light 473–508K and severe 548–573K regimes. Further, H/C and O/C molar ratios are found to be decreasing linearly in mild regime. In light and severe torrefaction; moisture removal and energy densification are increasing slowly. So, mild torrefaction was found to be optimum regime of torrefaction for practical applications. In mild torrefaction regime energy densification ratio was 1.05-1.52 for different biomasses studied.

Comparative study on the thermal behavior of untreated and various torrefied bark, stem wood, and stump of Norway spruce

In this work, the torrefaction of different parts of Norway spruce (stem wood, bark, and stump) was studied. Three different torrefaction temperatures were applied: 225, 275, and 300°C with 30 and 60min isothermal periods. The thermal stability as well as the evolutions of the decomposition products of the untreated and torrefied samples were measured by thermogravimetry/mass spectrometry (TG/MS). The TG/MS results are interpreted in terms of the chemical composition, namely the cellulose, hemicellulose and Klason lignin content. The inorganic components of the samples were measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES) technique. It was found that the effect of torrefaction temperature was greater than the effect of residence time up to 275°C, while at 300°C the residence time had a significant influence on the composition of the torrefied samples due to the intensive decomposition of cellulose. Principal component analysis has been applied to find statistical correlations between the torrefaction temperature, the residence time, the chemical composition and the thermal parameters of the samples. The results of the principal component analysis confirmed that the chemical composition and hence the thermal properties of the studied samples changed to a greater extent at higher torrefaction temperature than at lower torrefaction temperature.

Effect of Temperature and Duration of Torrefaction on the Thermal Behavior of Stem Wood, Bark, and Stump of Spruce

Abstract In this work the torrefaction of different parts of Norway spruce (stem wood, bark, and stump) was studied. Three different torrefaction temperatures were applied: 225, 275, and 300 °C with 30 and 60 minutes isothermal periods. The untreated and torrefied biomass materials were characterized by thermogravimetric analysis (TGA). The TGA results are interpreted in terms of the chemical composition determined by the cellulose, hemicellulose and Klason lignin content. The alkali ion contents of the samples were measured by ICP-OES technique. It was found that the effect of torrefaction temperature was greater than the effect of residence time up to 275 °C, while at 300 °C the residence time had a significant influence on the composition of the torrefied samples due to the intensive decomposition of cellulose.

Effect of the Torrefaction Temperature on the Structural Properties and Pyrolysis Behavior of Biomass

To improve prospects for high-value utilization of biomass, torrefaction pretreatments were conducted at 210, 230, 250, 270, and 300 °C with a reaction time of 30 min. The pyrolysis of torrefied biomass was also performed on a fixed-bed reactor system at 450 °C. The effect of torrefaction temperature on the yield, energy yield, structure, physical-chemical characteristics, and production composition of bio-oil was studied. The torrefaction pretreatment improved the fuel characteristics of pyrolysis products. When the torrefaction temperature was increased, the -OH and C=O contents decreased, the C=C contents increased, the pyrolysis peak temperature decreased, the residual carbon contents noticeably increased, and the Ea value remained in the range of 69 to 129 kJmol-1. The pore volume increased and the crystallinity index decreased due to degradation and recrystallization. The solid yield of pyrolysis biomass decreased sharply in contrast to the liquid yield. When the torrefaction temperature increased, the bio-oil yield decreased from 36.82 wt.% to 20.13 wt.%. The phenol content in the bio-oil markedly increased; however, oxygen-containing compounds such as acids, sugars, and furans, significantly decreased, which indicated that torrefaction pretreatment efficiently improved the quality of the fuel.

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.

Effects of Torrefaction Temperature on Pyrolysis Vapor Products of Woody and Herbaceous Feedstocks

A variety of hardwood, softwood, and herbaceous feedstocks (oak, southern yellow pine mix, loblolly pine, pinyon–juniper mix, and switchgrass) were each torrefied at 200, 250, and 300 °C. Each of the feedstocks was pyrolyzed and the resulting vapors were analyzed with a molecular beam mass spectrometer (py-MBMS). Compositional analysis was used to measure the total lignin content of three of the feedstocks (southern yellow pine, softwood; oak, hardwood; and switchgrass, herbaceous) before and after torrefaction at 300 °C, and large differences in the fraction of lignin lost during torrefaction were found between feedstocks, with oak having the largest decrease in lignin during torrefaction and switchgrass having the least. It is hypothesized that these differences in the thermal degradation are due to, in part, the different ratios of S, G, and H lignins in the feedstocks. Additionally, the torrefaction of kraft lignin was studied using thermogravimetric analysis coupled with Fourier transform infrared sp...

Evaluation of the structure and fuel properties of lignocelluloses through carbon dioxide torrefaction

Two typical lignocelluloses, pine and poplar, were torrefied in a tubular reactor under carbon dioxide medium at temperatures ranging from 220 to 340°C. The effect of torrefaction temperature on the structure and properties of the chars obtained was investigated to evaluate their fuel applications. As the temperature raised from 220 to 340°C, the mass yield decreased from 96.7% to 48.7% for pine, and from 97.1% to 43.8% for poplar. The higher heating value of the torrefied pine increased to 25.6MJ/kg for the sample torrefied at 340°C. An increase in reaction temperature resulted in a decrease in the contents of cellulose and hemicelluloses but notable increase of the content of lignin, especially for the sample subjected to the strongest torrefaction. The variation of C, H, and O contents of the samples after torrefaction suggested that a high temperature promoted the dehydration and deacetylation reactions. Thermal analysis indicated that the combustion activity of the sample was improved to a level of lignite after torrefaction. The hydrophobicity of lignocelluloses was notably increased with increased torrefaction severity, suggesting the prepared samples are good feedstocks for further processing.

Effects of torrefaction on yield and quality of pyrolysis char and its application on preparation of activated carbon

The effect of torrefaction on the yield and quality of pyrolysis char and its application on preparation of activated carbon was investigated in this study. In addition, the effect of torrefaction temperature at temperature range between 220 and 280°C on fuel characteristics was discussed. The results indicated that torrefaction pretreatment improved the fuel characteristics of rice husk samples, and torrefaction had a significant influence on yield and quality of pyrolysis char. With the increase of torrefaction temperature, the yield of pyrolysis char based on dry rice husk samples increased, and the yield of liquid product decreased, while the yield of gas product remained unchanged. It can be seen that torrefaction has little effect on the fuel characteristics of pyrolysis char. However, it has significant effect on internal pore structure of pyrolysis char which can be used as the precursor for preparation of activated carbon. Four kinds of pyrolysis chars obtained from original and torrefied rice husk samples were activated under the same preparation conditions. Torrefaction pretreatment enhanced the yield and quality of activated carbon. The activated carbon obtained from torrefied rice husk samples at the torrefaction temperature of 280°C exhibited highest specific surface area (2679m2/g) and pore volume (1.8883cm3/g), suggesting the potential application as adsorbent.

Torrefaction of biomass stalk and its effect on the yield and quality of pyrolysis products

Torrefaction is a promising pretreatment technology for biomass and its pyrolysis products upgrading. In this study, the effect of torrefaction temperature (220, 250 and 280°C) on the fuel properties of cotton stalk was investigated. And then pyrolysis experiments of torrefied cotton stalk were performed using a fixed-bed pyrolysis reactor. The effect of torrefaction on the yield and quality of pyrolysis products was also discussed. The results show that after torrefaction, the grinding performance and hydrophobicity of cotton stalk are improved, and the number of functional groups containing oxygen is decreased. Compared with the dried cotton stalk, oxygen content of torrefied cotton stalk reduce greatly while carbon content and heating value increase. The pyrolysis results show that the yield of bio-oil decreases, while the yield of biochar rapidly increases with increased torrefaction temperature. Torrefaction has little effect on the chemical composition of biochar. However, it has important effect on the quality of non-condensable gas and bio-oil. It enhances CH4 and H2 formation and increases the heating value of non-condensable gas. For bio-oil, it reduces acids but increases phenols content. In addition, the water content of bio-oil deceased obviously, leading to a noticeable increase in the heating value of bio-oil.

Response Surface Analysis of Elemental Composition and Energy Properties of Corn Stover During Torrefaction

This research studied the effects of torrefaction temperature (250-250 C) and time (30-120 minutes) on elemental composition and energy properties changes in corn stover. Torrefied material was analyzed for moisture content, moisture-free carbon (%), hydrogen (%), nitrogen (%), sulfur (%), and higher heating value (MJ/kg). Results at 350 C and 120 minutes indicated a steep decrease in moisture content to a final value of about 1.48% - a reduction of about 69%. With respect to carbon content, the increase was about 23%, while hydrogen and sulfur content decreased by about 46.82% and 66.6%, respectively. The hydrogen-to-carbon ratio decreased as torrefaction temperature and time increased, with the lowest value of 0.6 observed at 350 C and 120 minutes. Higher heating value measured at 350 C and 60 minutes increased by about 22% and the maximum degree of carbonization observed was about 1.21. Further, the regression models developed for chemical composition in terms of torrefaction temperature and time adequately described the process with coefficient of determination values (R2) in the range of 0.92-0.99 for the elemental composition and energy properties studied. Response surface plots indicated that increasing both torrefaction temperature and time resulted in decreased moisture content, hydrogen content, and the hydrogenmore » to-carbon ratio, and increased carbon content and higher heating value. This effect was more significant at torrefaction temperatures and times >280 C and >30 minutes.« less

Modelling anhydrous weight loss of wood chips during torrefaction in a pilot kiln

Beech and spruce chips were torrefied in a batch rotating pilot kiln. For each torrefaction the temperature curve of the moving chips bed was recorded. The anhydrous weight loss (AWL) of each torrefaction was measured. Effect of torrefaction temperature and duration on the AWL was studied. In order to optimise short time torrefaction, models that can estimate the AWL from the chips temperature curve are required. Three phenomenological models were successfully applied. They all gave good correlations between experimental and calculated AWL. These three models can be employed to optimise industrial torrefaction. However, the more complex they are, the more difficult it is to understand their physical meaning. It is thus preferable to use simple model for the industrial control of torrefaction.

Improvements of biomass physical and thermochemical characteristics via torrefaction process

AbstractVarious types of feedstocks such as straws and cotton gin waste are characterized by their low bulk density and relatively low energy content as well as irregular particle sizes and shapes. These factors impact the production of bioenergy from these fluffy feedstocks. The goal of this research is to improve the physical and thermochemical characteristics of biomass via torrefaction process. Torrefaction involves the heating of biomass to moderate temperature of 200 to 300°C in an inert atmosphere. Thus, the properties of the biomass undergo chemical and physical changes under torrefaction process.Several batches of wheat straw, rice straw, and cotton gin waste were torrefied at 260°C for 0, 15, 30, 45, and 60 min using a batch torrefaction system located at the bioenergy lab, Stuttgart, AR. Another set of experiments took place in which wheat straw was used as the feedstock. The effects of torrefaction temperature (200, 260, and 315°C) and residence time (60, 120, and 180 min) on the physical and thermochemical characteristics of wheat straw were studied. During 1 hour torrefaction at 260°C, moisture content was reduced by 70.5%, 49.4%, and 48.6% for wheat straw, rice straw, and cotton gin waste, respectively. Insignificant reduction (<1.9%) of the volatile solids was observed under the same torrefaction conditions. The heating value increased by 15.3%, 16.9%, and 6.3% for wheat straw, rice straw, and cotton gin waste, respectively. Rice straw showed the highest weight loss of 30.7% under the same torrefaction conditions.The second set of experiment showed that the torrefaction temperature have stronger effect compared with residence time. The highest heating value (22.75 MJ/kg) and the highest weight loss (54%) of wheat straw were observed at torrefaction temperature of 315°C and 3‐h residence time. Also, improvement of size reduction was visually observed, which has the favorable properties for application for gasification and/or pyrolysis. © 2009 American Institute of Chemical Engineers Environ Prog, 2009