First of all, I would like to express my gratitude to the almighty Allah who has given me the strength to face the challenges of completing this final year research project. I would like to express my sincere thanks and deep respect to Dr. To Sabil, my final year research project supervisor, for his constant monitoring and continuous guidance during the completion of my research project. I would also like to express my endless gratitude to all the technicians of the chemical engineering department and the bio-hydrogen technician, Mr. Syamil, for their cooperation during the experiment conducted in the laboratory.
I would like to express my gratitude to FELCRA, Bota, Perak and biohydrogen group for their contribution in my research project. Finally, I would like to thank all parties who were directly and indirectly involved in the completion of my study on kinetics of torrefaction process of oil palm biomass. 20 Figure 5: Stages in the heating of moist biomass from 'ambient' temperature to the desired torrefaction temperature and the subsequent cooling of the torrefied product.
INTRODUCTION
Problem Statement
Despite all the reported data, the basic researches on the torrefaction process of oil palm waste remain; namely empty fruit bunches (EFB), palm mesocarp fibers (PMF) and palm kernel shells (PKS) are quite limited. In particular, research on the optimal torrefaction conditions, parameters and kinetics of oil palm waste has not yet been widely discovered. However, using raw biomass materials as fuel poses several problems, such as high bulk volume, high moisture content and relatively low calorific value, which makes raw biomass an expensive fuel to transport [2].
In addition, untreated biomass has a relatively low energy density, high moisture content and is difficult to break down into small particles. These issues contribute to storage complications such as decomposition and self-heating, lower combustion efficiency, and limitations in gasification design. In addition, it is necessary to increase the energy yield to replace an equivalent amount of coal in applications such as combustion and gasification.
Objective and Scope of Study
LITERATURE REVIEW
Torrefaction Temperature and Time (Reaction Time)
Difficulties in interpreting the torrefaction process can arise from the definition of the torrefaction time. It does not tell how long the actual torrefaction takes place, as part of the residence time is "lost" due to heating of the biomass, possibly in combination with drying. When ambient temperature moist biomass is fed into a batch dry fraction reactor, the biomass is first heated to a temperature where the biomass is dried.
During ttor decomposition reactions will contribute mainly, but this will depend on the time contribution of the heating and cooling period. The heating period is important, as during this period the most thermally stable parts of the food biomass will begin to decompose rapidly. It is therefore expected that the decomposition reactions will cease as soon as the temperature is lowered. Therefore, the cooling period hardly contributes to the decomposition of biomass.
Previous Study on Torrefaction
- Torrefaction of wood
Figure 7 shows the weight loss curves of different types of biomass at 248 and 267 °C obtained by isothermal TGA experiments. The weight loss observed during heating of the sample from 200 °C, the temperature at which thermal decomposition begins, to the required temperature is relatively small, except for xylan. A careful study of the experimental weight curves shows that they do not become completely horizontal, but that the weight continues to decrease very slowly.
The final carbon yield is the product of the solid yield for the first decomposition reaction and the second decomposition reaction. The first reaction with a relatively low weight loss may very well be representative of the breakdown of reactive xylan in willow wood, since hardwood contains up to 30% xylan. The high weight loss in the second reaction can be explained by the decomposition of other fractions included in the wood, especially the cellulose fraction, probably in combination with the carbonization of the remaining hemicellulose fraction.
Reaction Kinetic
When the activation energy kV1 (kV2) is higher than the energy k1. or k2), the yield of solids decreases with increasing temperature. Thus, the introduction of separate formation of different classes of products, which may be questionable from the point of view of analytical chemistry, is a mathematical approximation to describe the fact that the ratio of solids to volatiles formed depends on temperature. Assuming that all reactions are first order, the system of equations can be solved analytically.
This system can be solved numerically using a suitable algorithm, for example in Matlab; a one-step solver can be applied, based on a modified Rosenbrock formula of order two.
METHODOLOGY
- Particle Sizing
- Torrefaction Process
- Tube Furnace
- Sample Analyses
- Ultimate Analysis
- Kinetic Parameters Calculation through MATLAB
Biomass sample was fed into the top for the first cutting process (cutting samples into small sizes of about 1 to 2 inches). After that, biomass sample was introduced into the side container for second cutting process (sample size becomes smaller than 1 inch or powder). Then the sample was sized using sieve model BA300N manufactured by CISA (figure 18). Sieve trays are arranged from large to small particle sizes.
After that, the sample was collected in each tray and placed in the corresponding bottle to avoid moisture. The torrefaction process was performed with a thermogravimetric analyzer model S11-AST-2 manufactured by Diamond TG/DTA (Figure 19). We used nitrogen gas as carrier gas, which was fixed at 100 ml min-1, so that the samples were torrefied in an inert environment.
Due to the limited amount of oil palm biomass, the sample was produced from TGA; a tube furnace was used to produce a larger quantity for analyses, ie. the TSH tube furnace model manufactured by Elite Thermal Systems Limited was used for the torrefaction process (Figure 20). The parameters (heating rate, target temperature, reaction time and final condition) were set on the screen of the tube furnace.
After configuring all the required parameters, the isolated button was pressed followed by the run button found on the tube furnace display. Calorific value was measured using bomb calorimeter model C2000 series manufactured by IKA-WERKE (figure 21). The experimental data obtained by TG were used to create a model for predicting fracture yield.
To determine the reaction order of the torrefaction process, we used a graphical method by plotting two types of graphs.
RESULT AND DISCUSSION
Modeling of Torrefaction Process
- Example of Calculation Kinetic Parameters through
- MATLAB
Two reaction steps for oil palm biomass degradation were found during the torrefaction process in TGA. Here A(s) was a solid, B(s) was an intermediate in a solid, and C(s) was a torrefied product in a solid. Thus, it was first order for both reaction steps for all oil palm biomass samples. The slope of the graph was constant and will be used for the next determination of the activation energy and the pre-exponential factor.
Meanwhile, the rate constant was obtained by plotting ln k versus 1/T from derivation of the Arrhenius equation. During the plotting, the slope of the graph, m showed the value of activation energy above the gas constant, and the intercept c showed the value of pre-exponential factor (Figure 29 until Figure 40). All kinetic parameters were identified through the extraction data from the TGA curve. To create a model for EFB, PMF and PKS at different particle sizes, the values of k1 and k2 were important to resolve unidentified reaction rate.
But the model was developed can only be used on particle sizes ranging from 250 to 500 µm for EFB, PMF and PKS. Torrefaction model was created through MATLAB to predict the amount of torrefied product from different amounts of raw material (EFB. PMF or PKS). MATLAB was run and values of torrefied product (EFB, PMF and PKS) were predicted by MATLAB.
Values were shown in Table 3 through Table 8 and plotted in Figure 23 through Figure 28 under discussion of experimental and model curves for different types of biomass.
Torrefied Biomass from Tube Furnace
Intensity Light Dark However, Tables 9 to Table 14 were not desirable to identify the weight loss during the torrefaction process, as TGA was able to accurately analyze the weight loss of the sample during the torrefaction process.
Ultimate Analyses for Raw and Torrefied Biomass
Furthermore, figure 42 to figure 43 showed that hydrogen and oxygen content were changed due to release of methane (CH4), ethane (C2H6), carbon dioxide (CO2) and carbon monoxide (CO) during torrefaction process. It decreased over torrefaction temperature and led to improvement of gasification properties of torrefied biomass [2]. The decrease in O/C ratio was due to the removal of water and carbon dioxide during torrefaction process [7]. The energy yield was referenced to higher heating value (HHV) for both raw and torrefied samples.
It appears that the torrefied product contained different amounts of carbon content, yielding different energy yields. PMF had the highest increase in carbon content, followed by EFB and PKS. emphasized that particle size had a small influence on energy yield and showed similar trends. The kinetic study of the TGA weight loss curve for EFB, PMF and PKS described two reaction steps during the torrefaction process.
The kinetic model can be used to predict the amount of torrefied oil palm biomass product from the torrefaction process. 2 h reaction time was sufficient for EFB, PMF and PKS, where there was no more sample weight loss (weight loss constant). We can conclude that four main parameters are important for the torrefaction process, namely torrefaction temperature, biomass type, particle size, torrefaction temperature and reaction time.
Other than that, ultimate analyzes for EFB, PMF and PKS showed different carbon, hydrogen, nitrogen, sulfur and oxygen contents before and after torrefaction process. During the execution of this torrefaction project, there are some recommendations from my side to make improvement and variety of focus on torrefaction research, so that it is completed with deep investigation. a) conducted research on the determination of composition of hemicellulose, cellulose and lignin for raw and torrefied biomass. Important to do this research is to know the exact composition of hemicellulose, cellulose and lignin after and before torrefaction process.
Furthermore, we can know the initial degradation of hemicellulose, cellulose and lignin during the torrefaction process.
Calorific Values for Raw and Torrefied Biomass…
CONCLUSION AND RECOMMENDATION
Recommendation
It is important to determine its effect on weight loss, energy content and final analysis. With this, a kinetic model already created can be modified and applied with different particle size ranges. Chen, W.-H., and Kuo, P.-C., 2010, "Study on torrefaction of various biomass materials and its effect on lignocellulosic structure simulated by thermogravimetry", Energy.
