Torrefaction Residence Time Research Articles

Significance of Torrefaction Effect on Energy Properties Palm Kernel Shell

The process of torrefaction is a thermochemical process that is widely used for the conversion of biomass into renewable fuels. In this study, the significance of temperature was determined by carrying out the torrefaction process at temperatures ranging from 275 to 350 degrees Celsius with a fixed residence time of 60 minutes. To ascertain the impact of time on the process, the torrefaction procedure was conducted over a residence time of 20 to 60 minutes at 300°C. Increasing the torrefaction temperature can substantially increase the palm kernel shell's calorific value, decrease water content, decrease volatility, increase fixed carbon, especially from 275 oC to 325 oC, and decrease ash content from 275 oC to 300 oC. Increasing the torrefaction residence time can significantly increase the palm kernel shell's calorific value from 20-40 minutes, decrease ash content and volatile content, and increase fixed carbon from 20-30 minutes. The residence time did not affect the water content in torrefaction temperature at 300 oC. The statistical analysis revealed that temperature and residence time have a substantial impact on the heating value and proximate analysis.

Effect of Leaching and Fungal Attacks During Storage on Chemical Properties of Raw and Torrefied Biomasses

Coffee husk, eucalyptus, and pine residues were torrefied at 290 °C in a screw reactor, during 5, 10, 15 or 20 min. The effects of feedstock type and torrefaction process parameters (holding time) on their energy characteristics were investigated. Raw and torrefied biomasses were then submitted successively to leaching and to white and brown rot fungi, to mimic storage conditions. Mass loss after leaching step, water content and weight loss due to fungal deterioration after 2, 4, 8, 12, 16 weeks were recorded. The chemical composition and high heating value (HHV) of the torrefied samples were measured to determine the alterations compared to raw biomass during their storage. Increasing torrefaction residence time improves the decay resistance of the biomasses. Variation of carbon content (%wt., dry basis) and HHV (kJ/kg, dry basis) were observed during native and torrefied biomasses fungal degradations. Carbon contents and HHV values of raw and torrefied biomasses decreased during Trametes versicolor exposure [49.65% > C > 44.07% and 19.71 kJ/kg > HHV > 17.19 kJ/kg, results from results from all tests combined.], whereas they increased during exposure to Coniophora puteana [46.15% < C < 52.70% and 17.43 kJ/kg < HHV < 20.74 kJ/kg]. Severe torrefaction is therefore a good way to improve coffee husk, eucalyptus, and pine energy properties while limiting loss of their energy properties during storage.

Analysis through thermogravimetric analyses of the impact of torrefaction processes performed under a non-oxidative atmosphere on hydrolysis lignin samples

Hydrolysis lignin samples were torrefied in a fixed bed reactor under a nitrogen flow, under four different isothermal temperatures (225, 250, 275 or 300 °C) and during 30 or 60 min. The impact of such torrefaction conditions on the hydrolysis lignin samples was analyzed through thermogravimetric analyses performed under non-oxidative or oxidative atmospheres and under a heating rate of 5 °C/min. The thermogravimetric profile and the reactivity of the raw and torrefied samples were compared. The optimal values of the kinetic parameters were determined using the EIPR model, first determining the number of constituents to be considered, then their proportions applying Van Soest’s protocol to the raw material and adjusting them for the torrefied samples. These values of the kinetic parameters were validated through observations of the experimental and simulated mass and mass rate curves and computations of the maximal difference between these curves. The values of the kinetic parameters did not significantly vary with the isothermal temperature or with the torrefaction residence time.

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.

Char quality response surfaces from torrefaction of coppiced willow in a horizontal moving bed pilot plant

AbstractCharacterizing the operation of a novel torrefaction plant based on horizontal moving bed reactors was the focus of this research work. Coppiced willow biomass was used as the feedstock for the torrefaction experiments carried out with this plant. The operating temperature and torrefaction residence time were each varied over a wide range in order to understand how these two parameters each influence torrefaction severity. The torrefaction severity was characterized by developing response surface plots for torrefaction metrics, including mass yield, energy yield, milling energy, and elemental composition.The operating conditions were varied from 220–280 °C with an 8–24 min residence time. The coppiced willow biomass was processed into a granular form, resulting in an average length and diameter of 19.3 and 7.5 mm, respectively. The operating conditions were found to produce a wide range of torrefaction severities with a mass yield range from 64.7–91.6 %. Temperature was found to have a greater influence over severity than exposure time. In order to understand the uncertainty of the measurements, experiments were repeated at a central point (250 °C and 16 min) six times. The repeatability was found to be ±0.72 % at the 95 % confidence limit. The response surfaces for mass and energy yield indicate that, for this feedstock, torrefaction severity below 80 % mass yield can be achieved in under 10 min at temperatures of 255 °C and above. This performance compares very favourably with other continuously fed pilot scale torrefaction plants.

Torrefaction of biomass from municipal solid waste fractions II: Grindability characteristics, higher heating value, pelletability and moisture adsorption

The microwave-assisted torrefaction of woody construction demolition waste (CDW) and grass clippings (GC) from municipal solid waste (MSW) was investigated under nitrogen-activated inert condition with respect to microwave power (250, 500 and 750 W), residence time (15, 30 and 45 min), moisture content (12, 16 and 20% w.b.) for CDW and 64% w.b. for GC. The results show that grinding energy consumption decreases as the microwave power level increases, indicating a significant improvement in the grindability of the material after torrefaction. Depending on the treatment combination, grinding energy savings of about 29–70% and 30–68% resulted after microwave-assisted torrefaction of CDW and GC, respectively. The higher heating value (HHV) increases with increasing microwave power level and torrefaction residence time. For CDW, the HHV increased by about 3–39% having HHV of 25,691 MJ/t. While for GC, the HHV increased by about 8–24%, having HHV of 20,936 MJ/t. This investigation further demonstrates that torrefaction reduced moisture adsorption of CDW and GC, which significantly improves their storage capability in humid locations. The moisture uptake ratios for torrefied CDW were found to be 0.66–0.96 and about 0.92 for torrefied GC, against a moisture uptake ratio of 1.0 for raw CDW and GC. However, biomass subjected to severe torrefaction process conditions produced pellets having poor physical quality. Microwave irradiation can be used effectively for torrefaction of MSW investigated at moderate microwave power level and short torrefaction residence time.

Torrefaction of biomass from municipal solid waste fractions I: Temperature profiles, moisture content, energy consumption, mass yield, and thermochemical properties

In this study, construction demolition waste (CDW) and grass clippings (GC) from municipal solid waste (MSW) were torrefied in a blown glass reactor using microwave irradiation with respect to microwave power levels (250, 500 and 750 W), torrefaction residence time (15, 30 and 45 min), moisture content (12, 16 and 20% w.b.) for CDW and 64% w.b. for GC, under nitrogen-activated inert condition. This investigation reflects that microwave power levels and torrefaction time have positive correlation on the temperature profiles. It shows that higher microwave power level contributed to higher heating rate and final temperature. Microwave power level and torrefaction time have negative correlation with the moisture content of CDW and GC after the torrefaction process. The higher the power level and torrefaction time, the higher the reaction temperature and the lower the moisture content of the torrefied MSW. Increasing the microwave power level and torrefaction residence time resulted to a corresponding increase in the thermochemical properties of the materials. As a result of torrefaction of CDW, elemental carbon increased by 1.3–39% over that of the non-torrefied CDW; while the elemental carbon of torrefied GC increased by 9–21% over that of the non-torrefied GC. The results show that the wetter the sample the less torrefaction energy is consumed and the more efficient the torrefaction process. At 500 W power level and 15 min torrefaction residence time of CDW, torrefaction energy of 4338 MJ/t and 3862 MJ/t were expended for 12 and 20% m.c., respectively.

Impact of Torrefaction on Woody Biomass Properties

Abstract In this work, Norway spruce stem wood, stump and bark were torrefied in a tubular reactor. The effects of feedstock type and torrefaction process parameters such as torrefaction temperature and residence time on the grindability and chemical properties of the torrefied biomass samples were investigated. In comparison to torrefaction temperature, torrefaction residence time had smaller effects on the grindability of stem wood and stump. For raw bark, much less grinding energy is required compared to those for raw stem wood and stump. Torrefaction has minor effects on grindability of the bark. The cellulose contents of stem wood and stump were reduced slightly at a torrefaction temperature of 275 °C. On the contrary, the cellulose content of the torrefied bark drastically decreased already at a torrefaction temperature of 275 °C, with only trace amounts left in the 300 °C torrefied products.

Comparative study of torrefaction of empty fruit bunches and palm kernel shell

This paper describes the effect of torrefaction on the characteristics of empty fruit bunches (EFB) and palm kernel shell (PKS). The torrefaction of EFB and PKS was investigated in a horizontal tubular reactor at a temperature ranging from 150 to 600 °C, for torrefaction residence time varying from 0 to 50 min. The torrefied products were characterized in terms of their elemental composition, energy yield, ash content and volatile fraction. The present study developed the torrefaction kinetics of EFB and PKS in a thermogravimetric analyzer to obtain the kinetic parameters. EFB and PKS exhibited excellent energy yield values. The gaseous products from torrefaction of EFB and PKS were also analyzed. Furthermore, the study reveals that the carbon content increases with an increasing torrefaction temperature but the O/C ratio, hydrogen and oxygen content decrease for both EFB and PKS. The energy yield and mass yield were found to decrease with an increase in the torrefaction temperature while the higher heating value (HHV) increased. From this study, torrefaction temperature between 290 and 320 °C is the optimum torrefaction temperature for EFB while torrefaction temperature between 300 and 320 °C is the optimum torrefaction temperature for PKS.

A study on torrefaction of sewage sludge to enhance solid fuel qualities

Torrefaction is a treatment which serves to improve the properties of biomass in relation to thermochemical processing techniques for energy generation. In this study, the torrefaction of sewage sludge, which is a non-lignocellulosic waste was investigated in a horizontal tubular reactor under nitrogen flow at temperature ranging from 150 to 400°C, for torrefaction residence time varying from 0 to 50min. The torrefaction kinetics of sewage sludge was studied to obtain the kinetic parameters. The torrefied sewage sludge products were characterized in terms of their elemental composition, energy yield, ash content and volatile fraction. The energy and mass yields decreased with an increase in the torrefaction temperature. From an elemental analysis, the weight percentage of carbon in the sewage sludge increased with an increase in the torrefaction temperature. On the other hand, the weight percentages of hydrogen and oxygen tended to decrease. The gaseous products from torrefaction of sewage sludge were also analyzed. From this work, it was found that the compounds with oxygen were emitted at a temperature lower than that for hydrocarbon gases and the temperatures of 300–350°C were the optimum torrefaction temperatures for sewage sludge.

A study on torrefaction of food waste

Torrefaction of biomass under anoxic condition can produce an energy dense and consistent quality solid biomass fuel for combustion and co-firing applications. This paper investigates the fuel characteristics of food waste at torrefaction temperatures ranging from 150 to 600°C, for torrefaction residence time varying from 0 to 50min in a horizontal tubular reactor. The torrefied products were characterized in terms of their elemental composition, energy yield, ash content and volatile fraction. The gaseous products from torrefaction of food waste were also analyzed. Thermogravimetric analysis was carried out in order to obtain the kinetic parameters for the torrefaction reaction of food waste. It was found that the food waste undergoes changes in their physical and chemical properties during torrefaction. The energy and mass yield were also found to decrease with an increase in the torrefaction temperature, whereas the higher heating value increased.