Murni M. Ahmad

Hydrogen from renewable palm kernel shell via enhanced gasification with low carbon dioxide emission.

Hydrogen economy has become more attractive with the energy crises and environmental issues associated with fossil fuel utilization more so with the discovery that hydrogen can be produced from renewable biomass. This provides good prospects to Malaysia that generates abundant palm wastes. Nevertheless, there is still limited knowledge on kinetics parameters for hydrogen production from palm kernel shell (PKS) gasification. Hence, this work aims to develop a mathematical model that is able to describe the kinetics of steam gasification of PKS with in situ CO2 capture while considering tar formation. A mean-squared error minimization approach has been used to estimate the kinetics parameters of the gasification process. Using the calculated kinetics parameters the process efficiencies are profiled with respect to the effect of gasification temperature, steam/biomass ratio and sorbent/biomass ratio. The parametric study indicates that the three variables promote hydrogen production at different degree of influence. This developed model can be further extended to incorporate optimization study on the potential clean production of hydrogen from PKS.

Kinetic Study on Palm Oil Waste Decomposition

Malaysia is the largest producer of palm oil and contributes 43% of worldwide production (Shuit et al., 2009). Beside palm oil, palm oil industry generated 169.72 million metric tons solid wastes which contribute 85.5% of total biomass waste produced in the country (Khan et al., 2010). This huge amount of wastes can be converted into valuable chemical feed stocks and fuels due to environmental problems associated with conventional fossil fuels. It is well known that lignocellulosic biomass mainly consists of hemicellulose, cellulose and lignin. The usual proportions (wt%) vary as 40-50% cellulose, 20-60% hemicellulose and 1025% lignin (Yang et al., 2007). The thermal decomposition of these individuals is important since they influence the basics of thermochemical conversion processes such as pyrolysis, combustion and gasification. Decomposition of these components is intensively studied in the literature. Demirbas et al. (2001) observed the ease of lignocellulosic biomass components decomposition as hemicellulose > cellulose >>> lignin. Based on different reasoning, Yang et al. (2007) proposed different decomposition regions of 220-300 °C, 300340 °C and >340 °C for hemicellulose, cellulose and lignin, respectively. Lignin is the last to decompose due to its heavy cross linked structure (Guo & Lua, 2001). Several techniques are available to study the kinetics of biomass decomposition. Among these, thermogravimetric analysis (TGA) is the most popular and simplest technique (Luangkiattikhun et al., 2008), based on the observation of sample mass loss against time or temperature at a specific heating rate. TGA provides high precision (Va rhegyi et al., 2009), fast rate data collection and high repeatability (Yang et al., 2004) under well defined kinetic control region. Very few attempts have been carried out to study the kinetics of empty fruit bunch (EFB) and palm shell (PS) using TGA. Guo & Lua (2001) presented the effect of sample particle size and heating rate on pyrolysis process and kinetic parameters for PS. They concluded a first order reaction mechanism for the decomposition of PS at different heating rates. They also suggested higher heating rates for faster and easy thermal decomposition of PS. Yang et al. (2004) studied activation energy for decompositions of hemicellulose and cellulose in EFB and PS by considering different temperature region for first order kinetic reaction. They evaluated average activation energy and pre-exponential factor from single-step decompositions of hemicellulose and cellulose. Luangkiattikhun et al. (2008) considered the

Upgrading of bio-oil from palm kernel shell by catalytic cracking in the presence of HZSM-5

ABSTRACT Upgrading of bio-oil extracted from palm kernel shell (PKS) was performed using a lab-scale fixed-bed reactor with HZSM-5 as a catalyst. The catalytic cracking was carried out at optimized conditions: 0.3-MPa pressure, temperature of 500°C, and oil to catalyst ratio of 1:5. One of the challenges in upgrading bio-oil by catalytic cracking is deactivation of catalyst due to coke formation on catalyst surface. To overcome coke deposition, the upgrading process was carried out at 0.3-MPa pressure. Characterization of raw and upgraded bio-oil obtained through catalytic cracking was discussed in detail, indicating improvement in its physical properties. The distribution of products after cracking of bio-oil includes 58.89 wt% of organic liquid product, 15.63 wt% of aqueous fraction, 7.84 wt% of coke, and 17.64 wt% of gases. The degree of deoxygenation and calorific value of organic liquid product is 43.74% and 31.65 MJ/kg respectively. Organic liquid product obtained comprises 17.55% of hydrocarbons within the gasoline range. Hence, HZSM-5 proved its effectiveness for upgrading the bio-oil in a continuous mode.

Performance Study of Ni Catalyst with Quicklime (CaO) as CO2 Adsorbent in Palm Kernel Shell Steam Gasification for Hydrogen Production

There is a need to search for efficient material that reduce CO2 content and enhance the hydrogen composition in the product gas from biomass steam gasification particularly for large scale production. The present study was carried out to perform the characterization of commercial quicklime as CO2 absorbent and Ni powder as catalyst. The chemical composition of the materials perform using x-ray fluorescence (XRF) indicated high amount of CaO and Ni in the bulk samples. Using XRF and SEM analyses, it was found that both materials showed high crystalinity. The adsorption isotherm from physisorption analysis suggested that the materials exhibits Type II category according to the IUPAC classification scheme. These types of material exhibit mesoporous structure which was also verified by the pore size of the samples found via BET analysis. The BET surface area reported was 4.16 m2/g and 0.78 m2/g for quicklime and Ni powder, respectively. In conclusion, commercial quicklime has the potential as CO2 absorbent, based on the pore size and surface area. Conversely, the surface properties of the Ni powder were found relatively lower as compared to other commercial catalysts available for biomass steam gasification.

Catalytic Cracking of Synthetic Bio-Oil: Kinetic Studies

Kinetic study on the transformation of model compounds of bio-oil into less oxygenated liquid product was performed. A fixed bed continuous reactor was used for the catalytic cracking of bio-oil model compounds at the temperatures of 300°C, 400°C and 500°C under atmospheric pressure. HZSM-5 was used as the catalyst with the oil to catalyst ratio of 15. The kinetic behavior of the catalytic cracking of bio-oil was represented by a 3-lumped model. The kinetic parameters were calculated using an error minimization approach based on least square method. The results indicated that rate of formation for both gaseous products as well as for liquid product (LP) increased when the temperature increased. The activation energy for liquid product was higher compared to that for gaseous product. The order of reaction was in a fraction form which implies the complex nature of the cracking reaction.

Pre-treatment of Malaysian agricultural wastes toward biofuel production

Various renewable energy technologies are under considerable interest due to the projected depletion of our primary sources of energy and global warming associated with their utilizations. One of the alternatives under focus is renewable fuels produced from agricultural wastes. Malaysia, being one of the largest producers of palm oil, generates abundant agricultural wastes such as fibers, shells, fronds, and trunks with the potential to be converted to biofuels. However, prior to conversion of these materials to useful products, pre-treatment of biomass is essential as it influences the energy utilization in the conversion process and feedstock quality. This chapter focuses on pre-treatment technology of palm-based agriculture waste prior to conversion to solid, liquid, and gas fuel. Pre-treatment methods can be classified into physical, thermal, biological, and chemicals or any combination of these methods. Selecting the most suitable pre-treatment method could be very challenging due to complexities of biomass properties. Physical treatment involves grinding and sieving of biomass into various particle sizes whereas thermal treatment consists of pyrolysis and torrefaction processes. Additionally biological and chemical treatment using enzymes and chemicals to derive lignin from biomass are also discussed.

Comparative Study for Catalytic Cracking of Model Bio-Oil and Palm Kernel Shell Derived Bio-Oil

This work investigates the comparison between upgraded product from model bio-oil and bio-oil from PKS. The process is carried out in the presence of HZSM-5 at temperature of 500oC, 3bar pressure and oil/catalyst ratio of 15. It is observed that the properties such as pH, density, calorific value and elemental value of products are improved. The calorific value for upgraded bio-oil is 31.65 MJ/kg while for model bio-oil the value is 30.32 MJ/kg at same operating conditions. The degree of deoxygenation of the upgraded bio-oil and upgraded model bio-oil is 43.74% and 45.56% respectively. The study showed that the model bio-oil can be used to represent the bio-oil.

Thermogravimetric analysis of palm oil wastes decomposition

Thermal decomposition of palm oil wastes i.e. palm kernel shell (PKS) and palm oil fronds (POF) was studied using thermogravimetric analysis (TGA) under non-isothermal conditions. Thermogravimetric (TG) and its first derivative profiles were depicted to show different breakdown regions for PKS and POF. The decomposition region of hemicellulose, cellulose and lignin was identified. Kinetic parameters i.e. activation energy, pre-exponential factor and order of reaction were then evaluated from the profiles for the temperature range of 50–900°C at a heating rate of 20 °C/min. Nearly 60 wt% of palm oil wastes decomposed at the temperature less than 400 °C. The thermal decomposition of palm oil wastes fitted well as first order kinetics with correlation coefficient of R2 > 0.99. The activation energy of PKS and POF was 35 and 41 kJ/mol, respectively. This fundamental study provides the basic information on palm oil wastes decomposition which can benefit our current development work on palm oil wastes steam gasification unit.

Economic analysis and optimization for bio-hydrogen production from oil palm waste via steam gasification

ABSTRACT Biomass steam gasification with in situ carbon dioxide capture using CaO exhibits good prospects for the production of hydrogen-rich gas. In Malaysia, due to abundance of palm waste, it is a good candidate to be used as a feedstock for hydrogen production. The present work focuses on the mathematical modeling of detailed economic analysis and cost minimization of the flow sheet design for hydrogen production from palm waste using MATLAB. The influence of the operating parameters on the economics is studied. It is predicted that hydrogen cost decreases by increasing both temperature and steam/biomass ratio. Meanwhile, the hydrogen cost increases when increasing sorbent/biomass ratio. Cost minimization solves to give optimum cost of 1.9105 USD/kg with hydrogen purity, hydrogen yield, hydrogen efficiency, and thermodynamic efficiency are 79.9 mol%, 17.97 g/h, 81.47%, and 79.85%, respectively. The results indicate that this system has the potential to offer low production cost for hydrogen production from palm waste.

Process simulation of hydrogen production from bio-oil using iCON.

ABSTRACT This work aims to investigate the feasibility of upgrading bio-oil into hydrogen via steam reforming and water shift reactions using conceptual design and simulation approaches. In the simulation work using PETRONAS iCON software, it is assumed that the aqueous fraction of bio-oil comprises of 67% acetic acid, 16.5% acetone, and 16.5% ethylene glycol. It is observed that increment in temperature and the amount of steam supplied in the steam reformer increase the hydrogen production until a certain extent. Meanwhile, opposite effect on hydrogen production is observed for both the temperature and steam used in the shift reactor. The overall conversion predicted for the process is 84% at operating temperatures and pressures for the steam reformer and shift reactor of 650 and 200°C, and 1 and 17 bar, respectively, and at the molar steam-to-carbon ratio (S:C) of 6.5. The results are compared and showed good agreement with those from published simulation and experimental work. Positive preliminary economic potential was obtained for the process developed, that is, USD 5.56 × 106/year.