Thermochemical conversion of press seed cake produced from non–edible biomass

Demand for energy and its resources are increasing every day due to the rapid growth of population and urbanization. As the major conventional energy resources like coal, petroleum and natural gas are on the verge of getting depleted in this century, biomass, which is an important renewable energy resource, can be used to produce renewable bioenergy (i.e., heat and electricity), biochemical and biofuels. However, the use of biomass for energy, fuels and chemicals production has generated significant concerns across the globe, especially in developing nations, due to the shortage of food and cultivable land and extremely high population density. This has led to the use of non–edible biomass resources such as Karanja, Jatropha, Neem, Mahua, and Sorghum. These biomass resources are widely used for extracting bio–oil in countries like India, Pakistan, Bangladesh, China, and Sri Lanka. However, after the extraction of bio–oil, a significant portion of biomass (i.e., ~60 wt.% of the total biomass) is left as a residual waste and generally referred as Press Seed Cake (PSC). These PSCs, despite having a very high organic content, are currently being landfilled. The current work focuses on the thermochemical conversion of PSCs with an aim to produce bioenergy, biochemical and biofuels. The present study has utilized PSC generated from Karanja, Mahua, and Sorghum. Thermochemical conversion processes that include torrefaction, pyrolysis, gasification, and liquefaction have been investigate in detail. The focus of the thesis is therefore to study the thermochemical conversion of PSC produced from lignocellulosic biomass regardless of the type of original plant source. The first part of this study demonstrated the efficiency of torrefaction process in upgrading the transport, storage and grinding characteristics of Karanja PSC, which is a lignocellulosic biomass. Torrefaction was carried out at different temperatures using residence time ranging from 10 to 90 min. The torrefaction experiments were performed using temperature in the range of 20–300 °C in a bench–scale vertical fixed bed reactor. The results showed that a significant change in elemental composition occurs with the reduction in O/C and H/C thereby increasing the calorific value and hydrophobicity of the torrefied biomass. The weight loss and the total energy remained in the fuel after torrefaction was found to be 30–35% and 80–85%, respectively. The HHV of the torrefied biomass was determined to be in the range of 19.5–21.5 MJ/kg. The kinetic parameters for thermal degradation namely, activation energy and pre–exponential factor, were determined from the experimental data as10.55 kJ/mol 0.341 min-1, respectively using a simple kinetic model involving single–step reaction mechanism for bio–char. The second and third parts of this study systematically investigated the pyrolysis of Mahua PSC and Sorghum, respectively in a bench–scale vertical fixed bed reactor. Both Mahua and PSC and Sorghum are also valuable lignocellulosic biomasses. Effect of pyrolysis temperature on the production of bio–char, bio–oil and bio–gas was studied in detail. The advanced characterisation of bio–char, bio–oil and bio–gas was performed using scanning electron microscope (SEM), x–ray diffraction (XRD), elemental analyser (CHNS), calorific value (CV), Fourier transform infrared (FTIR) spectroscopy and gas chromatography–mass spectrometry (GC–MS). The results obtained indicate that an increase in the pyrolysis temperature from 350 to 550 °C leads to a decrease in the bio–char yield from 42.55 to 30.38%. On the other hand, the maximum bio–oil yield of 15.94% was obtained at 450 °C. The GC–MS analyses of bio–oil samples revealed the presence of various important chemicals such as octadecenoic acid, p–cresol, 2,6–dimethoxy phenol, 4–ethyl 2–methoxy phenol, phenol, o–guaiacol, octadecanoic acid and free fatty acids. In the fourth part of the study, experimental investigations on the liquefaction of Karanja PSC were carried out in the presence of pyrolytic bio–oil (PBO) produced from the slow pyrolysis of the same feedstock. The effects of PBO to PSC ratio and liquefaction temperature were investigated with an aim to achieve the highest liquefaction conversion. Also, a study was carried out to compare the influence of PBO on liquefaction with that of a mixture of a conventional solvent such as phenol and an acid catalyst such as sulphuric acid. A detailed chemical analysis of PBO and liquefied product (bio–crude) was carried out using FT–IR, and GC–MS techniques. The results showed that the Karanja PSC could be directly liquefied in the presence of PBO at moderate reaction conditions. A maximum liquefaction conversion of 99% was obtained at a reaction temperature of 240 °C, a residence time of 160 min and a Karanja PSC to PBO ratio of 1:6. In contrast, ~ 94% conversion was obtained for the same residence time but at a significantly lower temperature of 160 °C when Karanja PSC, phenol and sulphuric acid were used in the mass ratio of 1:2:0.6. In the fifth part of the study, oxygen–steam based entrained flow gasification of torrefied Karanja PSC was carried out in a bench–scale entrained flow reactor with a capacity of 1 kg/hr. The temperature was varied from 600 to 1100 °C. The equivalence ratio (ER), and steam to biomass ratio (SBR) values was ranged from 0.1 to 1.0 while the particle size, Dp was ranged from 0.5 to 3.0 mm. The aim was to obtain the optimum operating conditions for the entrained flow gasification of the torrefied Karanja PSC. The results obtained show that the optimum operating parameters include the temperature of 1100 °C, ER of 0.3, SBR of 0.4 and the particle size of 0.5 mm. The highest values of LHV, CGE, and the carbon conversion were found to be ~12 MJ/Nm3, ~90% and of 98%, respectively for the torrefied Karanja PSC. In the sixth part of the study, an ASPEN Plus process simulation was carried out. A thermochemical equilibrium model (RGIBBS) in ASPEN Plus was used to predict the gasification behaviour of Karanja PSC. The modelling results were validated with experimental results obtained in an updraft fixed bed gasifier. Further to this, the model simulation was extended for different biomass wastes such as sawdust, rice husk, and sunflower husk. The effects of operating parameters like temperature, ER, and SBR on syngas composition, LHV and CGE were investigated. The results obtained from the current study have made a significant contribution in demonstrating the value addition to PSC from lignocellulosic biomass. The knowledge gained from the present study can be applied to develop large–scale thermochemical conversion processes for PSC from any lignocellulosic biomasses with suitable modifications

Pre-treatment of karanja biomass via torrefaction: Effect on syngas yield and char composition

Torrefaction is a mild pyrolysis process that is carried out at relatively low temperatures. In the present study, torrefaction of karanja de-oiled seed cake was carried out in a bench-scale fixed bed reactor under inert (N2) atmosphere. Effects of different reaction variables like temperature and the residence time on the weight loss and carbon conversion have been studied. Experiments were performed to examine the properties of torrefaction products and cold gas efficiency. The effect of torrefaction was studied by measuring the changes in yield, efficiency, tar and char production during gasification of torrefied biomass. The study confirmed that torrefaction of biomass altered the compositions of syngas produced. Increased torrefaction treatment impacted syngas composition yield by reducing carbon dioxide (around 4 to 10 mol %) and increasing H2 and CH4. Observed cold gas efficiency ranged between 40 and 80%. The syngas produced was rich in H2, CH4, and CO implying that the syngas quality is significantly improved by torrefaction. Also as expected, the moisture content of biomass is reduced by torrefaction. This holds the advantage for storage, transport and subsequent treatments of biomass at large scale. For solid products, it is observed that torrefaction increased the energy density, decreased the oxygen/carbon ratio, resulting in a more complex pore structure. The non-condensable gases accounted for about 50% of the gaseous torrefaction products. Effective use of the torrefaction gases will save energy and improve efficiency. The results of the present study prove that torrefaction of karanja seed cake has good application prospects

Derivation of optimum operating conditions for the slow pyrolysis of Mahua press seed cake in a fixed bed batch reactor for bio-oil production

The effect of pyrolysis temperature, retention time and inert gas (i.e. N2) flow rate on the conversion of Mahua Press Seed Cake (PSC) into bio-oil was studied in a slow pyrolysis fixed bed batch reactor. The optimum operating conditions for the process were derived using a Response Surface Methodology (RSM). It was found that the highest bio-oil yield (49.25 wt.%) can be achieved at a moderate temperature of 475 °C and a retention time of 45 min. As expected, the bio-oil yield was found to be affected by the reaction temperature. In a GC-MS analysis of the bio-oil, major compounds found were 6-octadecenoic acid, octadecanoic acid and free fatty acids (FFAs). The physicochemical properties of a raw PSC and bio-char were studied using bomb calorimeter, elemental analysis, and Fourier Transform Infrared (FT-IR) spectroscopy techniques. The heating value of the pyrolytic bio-oil (31.53 MJ/kg) at 475 °C was found to be increased by 46% compared to that of raw PSC (21.592 MJ/kg). The FT-IR analysis indicates that there was a decrease in the number of O-H (hydroxyl), C-H (alkanes) and C-O (primary alcohol) groups and an increase in the number of C=C (aromatics) functional groups with an increase in the pyrolysis temperature. Bio-gas analysis confirmed that, at higher temperatures, higher gas yield with increased CO and CH4 contents was observed. Finally, from the energy balance and economic analysis, it has been confirmed that at the derived optimum operating conditions it is feasible to produce bio-oil from Mahua PSC

Experimental investigations on the effect of pyrolytic bio-oil during the liquefaction of Karanja press seed cake

In this study, experimental investigations on the liquefaction of Karanja Press Seed Cake (PSC) were carried out in the presence of Pyrolytic Bio-oil (PBO) produced from the slow pyrolysis of the same feedstock. The effects of PBO amount and temperature were studied with an aim to achieve the highest conversion in liquefaction experiments. Also, comparison has been established between the use of PBO and conventional solvent and acid catalyst such as phenol and sulphuric acid, respectively for achieving the highest liquefaction conversion. A detailed chemical analysis and a comparison of PBO and liquefied product (bio-crude) have been carried out using FT-IR, and GC-MS techniques. The results showed that the Karanja PSC could be directly liquefied in the presence of PBO at moderate reaction conditions. A maximum liquefaction conversion of 99% was obtained at a reaction temperature of 240 °C, a residence time of 160 min and a Karanja PSC to PBO ratio of 1:6. In contrast, ~ 94% conversion was obtained for the same residence time but at significantly lower temperature of 160 °C when phenol and sulphuric acid were used in the ratio of Karanja PSC, phenol and H2SO4 as 1:2:0.6. It was observed that aromatic structure with less oxygen was evident in bio-crude compared to PBO

An experimental study to investigate the effect of torrefaction temperature on the kinetics of gas generation

Pre-treatment of biomass using torrefaction has been demonstrated to be an efficient process to improve the physical and chemical properties of biomass that can be used as a promising feedstock for gasification and boilers. Karanja, neem, kusum, mahua, and microalgae were the five biomass feedstocks investigated in this work for the torrefaction pre-treatment. The experimental study of torrefaction was carried out in a vertical fixed bed reactor set-up at 200, 250, and 300°C under nitrogen atmosphere. A thorough analysis of gas, liquid and solid products was made and the changes in H/C and O/C ratios in the pre-treated biomass were analyzed by elemental analysis. Among the five biomass feedstocks studied, mahua was found to have the highest heating value of 27.73MJ/kg at 300°C compared to others (neem=19MJ/kg, Karanja=23.3MJ/kg, kusum=25.8MJ/kg, microalgae=26.7MJ/kg). Following a detailed kinetic analysis using the yield of product gas mixtures, it is concluded that the biogases are generated by parallel independent first-order reactions. Also, the activation energy values for the torrefaction reactions of five biomass feedstocks were found to be different from each other

Optimization of process parameters for slow pyrolysis of neem press seed cake for liquid and char production

Slow pyrolysis of neem press seed cake (NPSC) was carried out in a fixed bed batch reactor to study the effects of temperature, retention time, and nitrogen (N 2 ) flow rate on liquid and char yields. Response surface methodology (RSM) based on Box-Behnken design was used to determine the optimum operating conditions to maximize the liquid yield. The highest liquid yield of 52.1 wt% was obtained at 512.5 °C, after 60 min using 0.5 L/min N 2 flow rate. Scanning electron microscopy (SEM), elemental analysis, bomb calorimeter, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffraction techniques and gas chromatography-mass spectrometry (GC-MS) were used to determine the physicochemical properties of NPSC and char, and chemical properties of liquid. GC-MS analysis showed that the bio-oil was rich in 9-octadecenamide, 2-propenyl decanoate, heptadecanenitrile, and oleanitrile. The higher heating value of the bio-oil and NPSC were 32.8 and 16.05 MJ/kg, respectively at 575 °C. The FT-IR results showed a decrease in the number of O-H (hydroxyl), C-H (alkanes), C=O (esters), -C-H (alkanes), and C-O (primary alcohol) groups in NPSC with increasing pyrolysis temperature