Torrefaction of Municipal Solid Waste in Malaysia

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

Effects of gasification temperature and equivalence ratio on gasification performance and tar generation of air fluidized bed gasification using raw and torrefied empty fruit bunch

This paper presents gasification performance study and tar generation at different gasification temperature and equivalence ratio using air fluidized bed gasification process. Empty fruit bunch (EFB) is selected as feedstock where two types of EFB were used which are raw EFB and EFB undergo torrefaction process as pretreatment. Experimental results show the synthesis gas yield, lower heating value (LHV), cold gas efficiency (CGE) and tar generation are steadily increased for both feedstock when gasification temperature is increased from 700 to 900°C. When ER is increased from 0.26 to 0.33 at fixed gasification temperature of 900°C, all gasification performances except LHV show an increment trend. Torrefied EFB shows superior performance in terms of producing more synthesis gas and better LHV compared to raw EFB. However, tar generated from torrefied EFB is higher than raw EFB. Based on tar component analysis, it has been found that 7 tar components are detected where all of tar components are classified as tertiary polycyclic aromatic hydrocarbons (PAHs) group for both feedstocks. Based on tar analysis, naphthalene is the most produced tar components obtained from gasification of raw and torrefied EFB

Syngas software for biomass gasification process

In this work, the thermodynamic equilibrium model has been developed in Excel software for evaluating gasification process. The software is called as Syngas software is applicable to study the effects of gasification temperature either using air or steam as gasifying agents for a wide range of biomass. The application of Syngas software has been highlighted through gasification of EFB using air as gasifying agents. The effects of gasification temperature between 650°C and 900°C has been conducted. The highest amount of hydrogen gas and carbon monoxide gas produced are 29.4 mol% and 44.1 mol% respectively at gasification temperature of 900°C. Meanwhile around 19.5 mol% of carbon dioxide gas and 5.8 mol% of methane gas have been generated at similar gasification temperature. The thermodynamic equilibrium model developed in the Syngas software has been validated against experimental data where root mean square errors (RMSEs) lesser than 1 is obtained indicating a reliable of the developed Syngas software

GTOP-PELLET : Green torrefied oil palm pellet

Malaysia as world second largest producer of palm oil. An oil palm tree consist 79% of biomass such as oil palm frond (OPF), empty fruit bunch (EFB), palm kernel shell (PKS), palm mesocarp fiber (PMF) and Oil palm trunk (OPT)

Anhydrous weight loss kinetics model development for torrefied green waste

One of the compositions of municipal solid waste (MSW) is green waste (GW) that collected from landscaping, garden, yard and trimming waste. GW has potential in becoming a biomass feedstock, but poses some drawbacks such as high moisture content, low heating value, high O/C and H/C ratios. Implementation of torrefaction as pre-treatment will improve the GW properties. During torrefaction, biomass is decomposed and leads to anhydrous weight loss (AWL). The estimation model for AWL is significant to study thermal degradation of GW. The aim of this work is to study two steps reaction in series for AWL prediction. GW were torrefied under inert condition at 240-300°C, 10°C/min heating rate and 30 minutes holding time using thermogravimetric analysis (TGA). Two steps reaction series model named Di Blasi and Lanzetta with extended non-isothermal phase is used in developing the AWL model. From initial guess, the parameters of activation energy and kinetic constant are adjusted to fit the calculated AWL to experimental AWL data by applying nonlinear optimization 'lsqcurvefit' routine in Matlab. The estimated kinetic parameters been used for AWL model and later being compared to experimental data from TGA. Good agreement obtained between experimental and model data indicating good kinetic parameters estimation

Synthesis Gas Production of Food and Wood Wastes in a Fluidized Bed Gasifier Using Thermodynamic Equilibrium Model

In this paper, the thermodynamic equilibrium model has been developed to predict the synthesis gas produced from food and wood wastes in fluidized bed gasifier. In addition the effect of gasification temperature on the amount syngas produced and gasification performance in terms of synthesis gas yield, lower heating value (LHV), cold gas efficiency and carbon conversion of feedstock are investigated. Based on the simulation of thermodynamic equilibrium model using food waste as feedstock, the results obtained show the amount of hydrogen (H2) and carbon monoxide (CO) gas production are increased linearly from 29.58 to 34.03% and 31.85 to 45.78% respectively as the gasification temperature is increased from 650 to 1000 °C. In contrast, the amount of carbon dioxide (CO2) and methane (CH4) gas produced are decreased from 33.26 to 19.17% and 5.31 to 1.02% respectively. In addition, gasification of wood waste also shows similar behavior as the H2 and CO gas are increased proportionally to the gasification temperature from 31.25 to 39.87% and 26.33 to 34.81% respectively. The production of CO2 and CH4 gas also shows it decrement from 38.75 to 23.38% and 3.67 to 1.94%. Meanwhile, food waste and wood waste gasification also shows the same trend in terms of increment of synthesis gas yield, lower heating value (LHV), cold gas efficiency and carbon conversion. As the gasification temperature is increased from 650 to 1000 °C, the synthesis gas yield are increased for both food waste and wood waste from 1.22 to 1.61 Nm3 /kg and 1.36 to 1.85 Nm3 /kg respectively. The LHV of the food waste and wood waste also increases consistently with gasification temperature from 4.56 to 5.00 MJ/ Nm3 and 5.60 to 6.57 MJ/ Nm3 respectively. CGE is increased from 31.9372 to 46.03 and 39.66 to 63.19% for food waste and wood waste respectively as the gasification temperature increased. The carbon conversion percentage increase corresponds to the gasification temperature from 48.69 to 59.88% and 57.26 to 68.08% for food waste and wood waste respectively

Kinetic parameter estimation for drying stage during gasification of empty fruit bunch

This paper presents kinetic parameter estimation of drying stage at different heating rates for representing drying behavior of empty fruit bunch (EFB) during gasification process. Kinetic constants based on Arrhenius law were estimated by using least-squares method by employing from thermogravimetric analysis data. The results show activation energy estimated are 14.53, 21.12 and 18.82 kJ/mol and pre-exponential factor estimated are 8.74, 236.37 and 275.36 min-1 for 10, 20 and 50 °C/min heating rates. The kinetic constants show good fit with experimental data where standard deviation lesser than 0.05 and R2 values above 0.98 are obtained indicating drying model is reliable to be used for designing biomass gasification

Oil palm waste to green energy : co-torrefied oil palm pellet (Co-TOPP)

Combination of torrefaction and co­pelletization process on producing high quality biofuel pellets form oil palm solid waste. Blending different type of oil­palm solid waste to produce environmentally friendly pellets

Optimization of oil palm empty fruit bunch gasification temperature and steam to biomass ratio using response surface methodology

An experimental work of empty fruit bunch gasification was conducted by using the bubbling fluidized bed to study the effect of the gasification temperature and steam biomass ratio (SBR) on the synthesis gas yield, Lower Heating Value (LHV) and Cold Gas Efficiency (CGE). Response Surface Methodology (RSM) was used to design the gasification experiment from the temperature range of 800-1000°C and SBR range of 0.5-1.5. Thirteen number of runs were generated based on Central Composite Design (CCD) with five replicated center points. Three regression models for predicting synthesis gas yield, LHV and CGE were developed and Analysis of Variance (ANOVA) was performed in this study. From ANOVA, the most influencing factor was gasification temperature which obtained higher F-value compared to SBR. The numerical optimization was also conducted in order to obtain the optimum condition to maximize the synthesis gas yield, LHV and CGE. From numerical optimization, gasification temperature of 800 °C and SBR of 1.14 were determined as the optimum condition which contributes to the maximum synthesis gas yield, LHV and CGE which are 1.25 Nm3/kg, 10.49 MJ/Nm3 and 90.72% respectively. The percentage error between the predicted and actual value of response variables was calculated and the error obtained lesser than 1%. Thus, it confirmed that the models obtained can be used to optimize the gasification of the empty fruit bunch