• Energy Research

Abstract Municipal solid waste (MSW) disposal is one of the main issues towards sustainable development in Malaysia. Current practices for MSW disposal such as landfilling and incineration poses a serious problems on the environment and health. Therefore a significant efforts have been made to utilize MSW for energy source by employing gasification process. However, the MSW is characterized by its high moisture content and low high heating value (HHV) which lowering the energy efficiency. In order to overcome this problems, torrefaction can be used as pretreatment method to remove the moisture content and upgrading MSW properties. The objective of this work is to study the effects of torrefaction temperatures ranging from 240 to 330°C for residence time of 30 minutes on two types of MSW namely food waste and wood waste. The torrefied MSWs are characterized in terms of ultimate analysis, proximate analysis and HHV. The mass and energy yields are also performed for both MSW. Based on the torrefaction, it was found that both food waste and wood waste show an increment on the weight percentage of C contents and decrement on the weight percentage of H and O content which resulting into reduce O/C ratio as the temperature is increased. The HHV for both food waste and wood waste are also increased after torrefaction between 240 and 330°C. The mass yield and energy yield were found to decrease with an increase in the torrefaction temperature. This suggests that torrefaction can be used as an effective MSW pretreatment and the torrefied MSW is more suitable to be used as fuel in gasification process.

Abstract Torrefaction is a thermal conversion method widely used for enhancing the properties of biomass. Usually this process is conducted under an inert atmosphere within a temperature range of 200 °C – 300 °C with residence time up to 60 minutes. During the torrefaction process, biomass is thermally decomposed thus resulted in biomass weight loss which is known as an anhydrous weight loss (AWL). As the properties of biomass are highly dependent on the AWL, therefore it is important to predict the reaction kinetics which will enable to describe the thermal degradation of the respective biomass for achieving the desired properties of torrefied biomass. In this study, the kinetic parameters of empty fruit bunch (EFB) from palm oil waste torrefied at 240 °C and 270 °C are predicted by applying two different kinetic models namely Di Blasi-Lanzetta Model and Rousset Model for both heating and isothermal phases. For Di Blasi-Lanzetta Model, the kinetic parameters are estimated based on the degradation of EFB into intermediate compound and char whereas kinetic parameters for Rousset Model are predicted based on the degradation of three main constituents of EFB which consists of lignin, cellulose and hemicellulose. All kinetic parameters are estimated according to Arrhenius law and fitted to the experimental result. The result shows that AWL estimation using kinetic parameters predicted from both models are in a good agreement with the experimental result and thus applicable to represent AWL of EFB torrefaction. In conclusion, Di Blasi-Lanzetta Model is more relevant to represent real torrefaction in comparison to the Rousset because of its ability to provide detailed information for the evolution of solid and volatile products during torrefaction.

Abstract In Malaysia, palm oil wastes are identified as the potential biomass for renewable energy sources. Usually the higher heating value (HHV) is essential for energy analysis and can be estimated using bomb calorimeter but this method usually is time consuming with possibilities of experimental errors. Thus many correlations have been established to predict the HHV based on the proximate analysis. However, most of the correlations only take into account the HHV of raw biomass. No attempts have been made on estimating HHV of torrefied biomass using model correlation. Therefore, the objective of this study is to propose new correlation based on proximate analysis which is applicable for raw and torrefied palm oil wastes. The HHV and proximate analysis of raw and torrefied palm oil wastes at different torrefaction temperature ranges from 240 to 330°C are measured experimentally for model correlation. In addition the HHV and proximate analysis of raw and torrefied palm oil wastes from published literature are included in order to enhance the reliability of model correlation. Based on the model correlation, low average absolute error (AAE) of 5.37% and low average bias error (ABE) of -1.00% are obtained indicating the estimated model correlation is suitable and reliable to estimate the HHV of raw and torrefied palm oil wastes from proximate analysis.

Abstract Palm kernel shell (PKS) pellets are used as fuel for boilers due to their uniform shape and carbon content. However, the pellet's low mechanical properties can cause a high level of dust, increased fire explosions, and become health hazards to workers, which become challenging during transportation and storage. In this study, four types of binders, carboxymethylcellulose, lignin, starch, and glycerol, were used to improve the mechanical durability of torrefied PKS pellet. The PKS was torrefied at 250 ℃ for 30 min and pelletized at 130 ℃ and 12 MPa. The torrefied pellets were characterized according to their chemical and physical properties. Results indicate that the density of pellets using all binders achieved more than the standard value (600 kg/m3). Overall, the carboxymethylcellulose could be used as a suitable binder that gives the highest mechanical durability (4449 N), low ash content (4.2 wt%), and improved HHV (20.68 MJ/kg) compared to other binders for torrefied PKS pellets to be used as fuel for power generation.

Abstract Torrefaction is a thermal treatment process used for upgrading lignocellulosic biomass properties into a promising renewable energy, which is performed under inert condition at a temperature range of 200 - 300°C between 15 – 60 minutes residence times. The aim of this study was to investigate the effect of torrefaction treatment on chemical composition and energy properties at different temperature 240, 270, 300 and 330°C with different residence time at 15, 30 and 60 minutes for oil palm biomass (empty fruit bunch). The analysis demonstrated an increase degradation of biomass hence an increase of mass loss was observed due to the combined effect of temperature and treatment duration. Higher heating values was increased by 55% which attributes the energy generations from the torrefied materials. Hemicellulose and cellulose content degraded as temperature and treatment duration increased, while lignin content increased due to the decomposition of hemicellulose and cellulose which accumulated the lignin content in the torrefied biomass. This study proves that torrefied biomass can be used as biofuel as it has higher heating value, and improved the chemical and physical properties of biomass.

Abstract This study investigated the influence of the torrefaction process on thermal degradation and chemical changes of oil palm solid waste (OPSW) through thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) analysis. Palm kernel shell (PKS) showed the highest mass and energy yield after the torrefaction process. Furthermore, torrefied PKS (TPKS) showed the highest heating value (23.10 MJ/kg). Weight loss in active pyrolysis stages was reduced after the torrefaction, thus indicates the lignocellulosic component decomposition. OPSW showed a reduction in hydroxyl group (−OH) after torrefaction resulting in hydrophobicity characteristic. Torrefaction has significantly enhanced the characteristics of OPSW as solid biofuel.

Combining torrefaction and grinding of biomass in one reactor may be an attractive fuel pretreatment process. A combined laboratory torrefaction and ball mill reactor has been constructed for studies of the influence of temperature and residence time on the product yields and particle size reductions of Danish wheat straw, spruce chips, and pine chips. On the basis of initial experiments, which evaluated the influence of reactor mass loading, gas flow, and grinding ball size and material, a standard experimental procedure was developed. The particle size reduction capability of the torrefaction process has been evaluated by the relative change in d50, and this method was compared to the Hardgrove grindability index (HGI), showing reasonably similar results. Significant differences in torrefaction behavior have been observed for straw and spruce chips torrefied at 270–330 °C. Torrefaction of straw for 90 min yielded a higher mass loss (27–60 wt %) and relative size reduction (59–95%) compared with spruce (...

The release of chlorine (Cl) and sulfur (S) during biomass torrefaction and pyrolysis has been investigated via experiments in two laboratory-scale reactors: a rotating reactor and a fixed bed reactor. Six biomasses with different chemical compositions covering a wide range of ash content and ash-forming elements were torrefied/pyrolyzed in the temperature range of 150–500 °C. The relative release of chlorine and sulfur was calculated based on mass balance and analysis of the biomass before and after torrefaction. In selected cases, measurement of methyl chloride (CH3Cl) in the gas from straw torrefaction has furthermore been conducted. The release of chlorine from straw was first observed at 250 °C and peaked with about 60–70% at 350 °C. Analysis of the released gas showed that most of the chlorine was released as methyl chloride. Increasing the straw content in the reactor resulted in a lower fractional release of Cl, probably due to more reactive sites in contact with gas phase Cl species leading to se...