Coupled effect of torrefaction and blending on chemical and energy properties for combustion of major open burned agriculture residues in Thailand

Thailand is an agriculture-based country. It produces large amounts of open burned agricultural residues. A strategy to use them as biofuel all year round is to enhance their fuel properties by coupling blending and thermochemical pre-treatment. In this study, the pyrolytic behaviour of major residues (napier grass , rice straw, cassava stalks and corn cob) exposed to a high torrefaction temperature (300°C) was investigated for various blending ratios, i.e. 100:0, 50:50 and 70:30. The release of chlorine was quantified for each biomass blend, including, a new fouling risk index ratio. Also, the synergistic effects of both ignition and burnout temperatures were analysed. Rice starw and napier grass were found to be characterised by a high ash content and so large amounts of solid yield after torrefaction. Raw biomasses and untreated biomass blends were found to be less suitable as biofuel than torrefied biomasses. The ratio K2O:SiO2, indicator of fouling risk during combustion, was found to be low for all torrefied blends. The HHV:Cl ratio, indicator of combustion quality, indicated that NG mixed with RS (50:50 proportion) is the most promising blend. Significant synergetic effects were observed for biomasses mixed before torrefaction. The burnout temperatures for raw and torrefied biomasses were identified in the range 773-787 °C and 786-795 °C. (Résumé d'auteur

Effect of the addition of different waste carbonaceous materials on coal gasification in CO2 atmosphere

YesIn order to evaluate the feasibility of using CO2 as a gasifying agent in the conversion of carbonaceous materials to syngas, gasification characteristics of coal, a suite of waste carbonaceous materials, and their blends were studied by using a thermogravimetric analyser (TGA). The results showed that CO2 gasification of polystyrene completed at 470 °C, which was lower than those of other carbonaceous materials. This behaviour was attributed to the high volatile content coupled with its unique thermal degradation properties. It was found that the initial decomposition temperature of blends decreased with the increasing amount of waste carbonaceous materials in the blends. In this study, results demonstrated that CO2 co-gasification process was enhanced as a direct consequence of interactions between coal and carbonaceous materials in the blends. The intensity and temperature of occurrence of these interactions were influenced by the chemical properties and composition of the carbonaceous materials in the blends. The strongest interactions were observed in coal/polystyrene blend at the devolatilisation stage as indicated by the highest value of Root Mean Square Interaction Index (RMSII), which was due to the highly reactive nature of polystyrene. On the other hand, coal/oat straw blend showed the highest interactions at char gasification stage. The catalytic effect of alkali metals and other minerals in oat straw, such as CaO, K2O, and Fe2O3, contributed to these strong interactions. The overall CO2 gasification of coal was enhanced via the addition of polystyrene and oat straw

Utilization of Waste Biomass Resources for Hydrogen-rich Syngas Production via Steam Co-gasification Process

弘前大学博士（工学）doctoral thesi

Combustion pattern, characteristics, and kinetics of biomass and chars from segmented heating carbonization

The combustion patterns, characteristics, and kinetics were investigated by thermogravimetric analysis for raw maize straw, cotton stalk, and chars obtained from segmented heating carbonization at 300–800 °C. With increasing carbonization temperature, combustion patterns of biomass chars transform from the sequential reaction steps corresponding to pyrolysis and heterogeneous oxidation of volatiles and char to the in situ heterogeneous oxidation of fixed carbon and volatiles, the ignition temperature of biomass chars gradually increases, the ignition index does not monotonically increase, and the burnout index and combustion characteristic index decrease to different degrees. Judging from the combustion characteristic index, chars obtained from 300 to 500 °C of carbonization show better combustibility. The kinetic parameters of raw and carbonized biomass were determined by Coats–Redfern method. Different reaction mechanisms exist in oxidation processes of different chars, which attribute to the synergistic effects of homogenous oxidation of volatiles and heterogeneous oxidation of char. The kinetic parameters obtained from the variation of species and model functions exhibit kinetic compensation effect

Thermochemical conversion of non‐woody biomass: upgrading cotton gin waste into solid fuel

Non-woody biomass is a common waste material found in agriculture. Despite its abundance, the waste is not widely utilised due to unfavorable physical properties (bulkiness, irregular size and varied composition) and low energy content. The aim of this research is to study the solid fuel properties of a non-woody biomass in order to improve their qualities. Cotton gin waste (CGW), a source of non-woody biomass from the processing of cotton, was selected. Methods of densification and blending of biochar were proposed and evaluated for transforming CGW into pellets in order to create a fuel with high density and energy content, as well as uniform physical properties. The development of CGW pellets was achieved by using a small scale pellet mill. CGW was blended with 5 to 20 percent weights of biochar. The developed CGW pellets were accordingly defined as CGW100, CGW95, CGW90, CGW85 and CGW80 pellets, implying the weight percentages of CGW as much as 100%, 95%, 90%, 85% and 80% in pellets, respectively. It has been found that pelleting the CGW increases the bulk density from 112 kg/m3 to 600 kg/m3. The biochar blends upgraded the heating values of CGW pellets from 14 MJ/kg of CGW100 to 18 MJ/kg of CGW80. In the process of stabilisation, the blended pellets slightly shrank, while the pure CGW pellet marginally expanded. In contrast to the pellet durability, the hardness was significantly influenced by the biochar addition. The biochar in the pellets diminished the rancid smell of raw CGW. It has also been found that CGW95 and CGW90 behaviours in the thermogravimetric (TGA) combustion were almost identical with CGW100 combustion. In addition, CGW95 pellets had the highest conversion rate and resulted in the least residual ash. On the contrary, CGW85 and CGW80 pellets were slow in conversion and burn out at closer to the biochar ignition temperature. From the examination of ash content and activation of energies, all the blended pellets show a synergism in co-combustion. Similar to combustion, the TGA pyrolysis using inert gas also resulted in a slightly higher conversion for CGW95. Other biochar blended pellets show a lower and more linear conversion as a function of biochar content. A CFD model has been developed using ANSYS Fluent 17.2 software. The approaches are the discrete phase and non-premix combustion models. The model shows an accurate prediction of the gasifier temperature and resulting gas composition. The simulation also predicts that CGW95 will have a higher CO yield than CGW90. The gasification of CGW95 pellets with air to fuel ratio of 1.3 v/w results in a gas composition of CO, CO2, H2 and CH4 gas of 19.8%, 11.6%, 14.2% and 0.2%, v/v respectively. The estimated gas heating values are in the range of 3.9-5.1 MJ/m3. It has been found that 30% energy produced from CGW pellet gasification is sufficient to cover the energy need for pellet production. The costs of energy in the ginning house can be reduced by 20-40% from the use of produced gas. The GHG emission is also lowered. Overall, it can be concluded that upgrading the non-woody biomass into pellets and applying it in a co-gasification could potentially provide an effective alternative fuel source to achieve agricultural energy self-sufficiency and off-grid operation

Effect of microwave and thermal co-pyrolysis of low rank coal and pine wood on product distributions and char structure

peer-reviewedDirect conversion of a low-rank coal into valuable chemicals or improving its char’s coking value became very demanding goals in coal utilization strategies. In this work, the co-pyrolysis of a low-rank lignite coal and pine wood sawdust biomass blended at a 3:1 coal-to-biomass ratio was investigated along with original coal and biomass samples by microwave assisted and conventional thermal methods at 550℃ under nitrogen and ambient pressure. The carbon structure and its reactivity in generated chars and the product distributions were greatly affected by the applied heating mechanism and the presence of biomass during coal pyrolysis. High gas and low tar yields were observed for all microwave chars in comparison to thermal chars, regardless of composition. The addition of biomass to coal increased the tar yield under both methods and to a higher extent under the microwave. This agrees with the high gas yield and high aromatic-to-aliphatic fraction observed under the microwave and the presence of biomass. The high O/C ratio and low fixed carbon content in a biomass structure relative to coal affect the product distribution during microwave pyrolysis. This could selectively heat the biomass in the sample, remove its polar groups, and convert it into an efficient microwave absorber biochar that can decompose coal efficiently during co-pyrolysis. The aromatic carbon stacking and its ordering in the generated chars were investigated by powder X-ray diffraction, Raman spectroscopy, dielectric property measurements, and electron spin resonance techniques. A synergistic effect was observed upon biomass addition during microwave coal pyrolysis. Electron spin resonance spectroscopy revealed that the microwave coal/biomass char is the most stable char with the lowest free radical concentration. This agrees with the highest IG/Iall band area ratio calculated from Raman analysis revealing a more graphitic nature for carbon in this char. Similarly, the dielectric properties confirmed that the addition of biomass to coal under the microwave has the highest loss tangent, indicating a high graphitic nature compared to pure biochar or coal char

Development of Small-scale Systems for Power Generation and Hydrogen Production by Biomass Thermochemical Conversion

弘前大学博士（工学）doctoral thesi

Thermochemical conversion of biomass: Potential future prospects

The thermochemical conversion of biomass is potentially vital to meeting global demand for sustainable transport fuels so besides combustion; torrefaction, liquefaction, pyrolysis and gasification are reviewed. The merits and demerits of these processes and examples of industrial applications are evaluated, and two promising avenues for future development are identified. The future of biomass upgrading via thermochemical processing will depend on sector coupling, both within the energy sector and with sectors such as food production. Owing to environmental constraints and the need to maintain food production, the availability of traditional feedstocks for biofuels, such as corn, will be limited in the future. Now given the ambitious targets for sustainable aviation fuel – a higher quality fuel – reserving appropriate feedstocks for aviation fuel will be necessary. Such a policy would open opportunities for the commercial development of the sustainable production of such liquid fuels via liquefaction and pyrolysis. The second avenue of opportunity links to the fact that biomass in the form of wooden pellets has established itself as an essential fuel. In the UK and elsewhere, it is already contributing to the decarbonisation of the electricity grids. So worldwide, a positive future for biomass combustion, aided where appropriate by torrefaction, is envisaged as increasingly crucial for the abatement of greenhouse gas emissions. Alongside battery storage and pumped hydroelectric storage, the contribution of biomass processes, such as torrefaction, to tackling the storage problem arising from the intermittent nature of wind and solar energy has been clarified for the first time

Thermochemical conversion and upgrading of wheat straw biomass into solid fuel

Herbaceous biomass is a typical agricultural waste produced from leftover crops. Biomass straw has limited uses due to its unfavourable physical characteristics, including bulkiness, varying sizes, varied compositions, and low energy content, but its availability is abundant. This study investigated the wheat straw’s (WS) potential fuel properties and the methods to improve their qualities. Different additives (sawdust: SD, biochar: BioC and bentonite clay: BC) were used to identify optimal pelleting composition. A small-scale pellet mill was used for WS pellet development, and five types of combinations were first investigated (T1: 100% WS, T2: 90% WS + 10% SD, T3: 90% WS + 10% BC, T4: 90% WS + 10% BioC, and T5: 70% WS + 10% BC + 10% BioC + 10% SD). To compare and improve pellet quality, seven types of pellets (T1, T5 plus T6, T7, T8, T9, and T10) were further considered and analysed with different combinations of additive materials (now including starch and crude glycerol also). Most of these treatments could improve the pellet durability to ≥ 92%, bulk density to ≥ 600 kg/m3 and heating value to ≥18.5 MJ/kg, which meets the pellet ISO 17225-8 standard specification requirements, where the inorganic ash content was all higher than the ISO standard level. The WS pellet pyrolysis process was studied in a laboratory-scale kiln. The maximum pyrolysis temperature of 600°C was obtained at 60 min for slow pyrolysis. The pyrolysis results demonstrated that additive mixing was particularly useful for pellet (T5) making, resulting in an increased conversion rate, achieving a gas yield of 43.52%, thermal conversion efficiency of 75.67% and syngas production of 46%. The thermokinetic behaviour of WS pellets (T1 and T5) for both combustion and pyrolysis was determined by thermogravimetric analysis (TGA). The additives, especially biochar added with WS (T5), considerably changed the thermokinetic behaviour of the pellets compared to pellets without additives (T1). Both pellets followed a multistage reaction and the equilibrium chemical reaction behaviour, but the T5 pellet reaction results (E\u1d6fc and lnA) were significantly higher in pyrolysis and combustion cases. A CFD model was developed using the ANSYS Fluent 2021R2 for gasification simulation. The study was also performed at a steady state regime considering the non-premixed combustion and species transport models. At the same time, biomass and air flow rates were initially set as 9.0 kg/h and 37.78 Nm3/h, respectively. The model could predict the gasifier's temperature and the composition of the produced gas. With an equivalence ratio (ER) of 0.35 during gasification, the proportions of CO, CO2, H2, and CH4 gas produced were 19.8%, 11.6%, 14.2%, and 0.2% v/v, respectively. Furthermore, the techno-economic analysis indicated that the cost of pellet production ranged from $232 to$360 per tonne. Compared with the current market price, the profit from pellet production was about 42%. Drying a one-tonne wheat crop (moisture removed from 20 to 12%) would require 20 kg of pellets. Overall, it was concluded that upgrading the WS biomass into pellets and conversion into energy could provide an efficient alternative fuel source. Additional research is needed to explore alternative additives for reducing ash reduction. Furthermore, modifications are required for the developed CFD model to examine ash and tar production and its validation against data obtained from large-scale gasification