Gasification of polyethylene (PE) and woodchips (WC) mixtures have been investigated in a semi-batch reactor, using high temperature steam as the gasifying agent. The reactor temperature was ...maintained at 900
°C. The ratio of PE–WC was varied from 0% to 100% in 20% intervals. Characteristics of syngas were evaluated based on the yield of syngas, hydrogen, energy, ethylene, total hydrocarbons and apparent thermal efficiency of the process. Results show that properties of syngas evolved during gasification of PE–WC blends cannot be determined from the weighted average syngas properties obtained from separate gasification of WC and PE. Superior results in terms of syngas yield, hydrogen yield, total hydrocarbons yield, energy yield and apparent thermal efficiency from PE–WC blends were obtained as compared to expected weighed average yields from gasification of individual components. Results confirm synergistic interaction between PE and WC during high temperature steam gasification of these mixtures. These results also provide the importance of mixing two or more compounds on the performance of stream gasification of wastes.
This paper reports the use of lignin-rich residues from second generation bioethanol production, to produce syngas that can be applied in the gas fermentation process. Three gasification technologies ...at a different scale were considered in this study. Fixed bed updraft gasification of about 30 kg/h solid feed, bubbling fluidized bed gasification of about 0.3 kg/h solid feed and indirect gasification of about 3 kg/h solid feed. Two lignin-rich residues with different properties were tested and the results were evaluated in terms of feedstock pretreatment (grinding, drying and pelleting) and syngas quality requirements for the fermentation process. The molar H2/CO ratio (ranging from 0.6 to 1.0) and the tar yield (18–108 g/Nm3) obtained from the three gasification technologies was quite different. For the syngas fermentation process, low H2 to CO ratio is preferred, as most of the organisms grow better on CO than H2. Furthermore, different contents of impurities that can reduce the fermentability of the gas (such as hydrocarbons, HCN, HCl, NH3, COS and other organic S- compounds) were detected in the product gas. The concentration of these compounds in the syngas is related to the content of the corresponding compounds in the original feedstock. The different characteristics of the lignin-rich feedstocks are related to the specific pre-treatment technologies for the (hemi)cellulose extraction. By tuning the pre-treatment technology, the properties of the feedstock can be improved, making it a suitable for gasification. Tar and unsaturated hydrocarbon compounds need to be removed to very low levels prior to the fermentation process. As a next step, the combination of the gasification and the appropriate product gas cleaning, with the syngas fermentation process for the production of bio-alcohols will be evaluated and the overall efficiency of the gasification-fermentation process will be assessed.
Kinetics of woodchips char gasification has been examined. Steam and CO
2 were used as the gasifying agents. Differences and similarities between kinetics of steam gasification and CO
2 gasification ...have been discussed. Comparison was conducted in terms of gasification duration, evolution of reaction rate with time and/or conversion, and effect of partial pressure on reaction rate. Reactor temperature was maintained at 900
°C. Partial pressure of gasifying agents varied from 1.5 bars to 0.6 bars in intervals of 0.3 bars. Steam and CO
2 flow rates were chosen so that both gasifying agents had equal amount of oxygen content. CO
2 gasification lasted for about 60
min while steam gasification lasted for about 22
min. The average reaction rate for steam gasification was almost twice that of CO
2. Both reaction rate curves showed a peak value at certain degree of conversion. For steam gasification, the reaction rate peak was found to be at a degree of conversion of about 0.3. However, for CO
2 gasification the reaction rate peak was found to be at a conversion degree of about 0.1. Reaction rates have been fitted using the random pore model (RPM). Average structural parameter,
ψ for steam gasification and CO
2 gasification was determined to be 9 and 2.1, respectively
. Average rate constant at 900
°C was 0.065
min
−1 for steam gasification and 0.031
min
−1 for CO
2 gasification. Change in partial pressure of gasifying agents did not affect the reaction rate for both steam and CO
2 gasification.
The paper presents techno-economic analyses and life cycle assessments (LCA) of the two major gasification processes for producing hydrogen from biomass: fluidized bed (FB) gasification, and ...entrained flow (EF) gasification. Results indicate that the thermal efficiency of the EF-based option (56%, LHV) is 11% higher than that of the FB-based option (45%), and the minimum hydrogen selling price of the FB-based option is $0.3 per kg H2 lower than that of the EF-based option. When a carbon capture and liquefaction system is incorporated, the efficiencies of the EF- and FB-based processes decrease to 50% and 41%, respectively. The techno-economic analysis shows that at a biomass price of $100 per tonne, either a minimum price of $115/tonne CO2e or a minimum natural gas price of $5/GJ is required to make the minimum hydrogen selling price of biomass-based plants equivalent to that of commercial natural gas-based steam methane reforming plants. Furthermore, the LCA shows that, biomass as a carbon-neutral feedstock, negative life cycle GHG emissions are achievable in all biomass-based options.
•Techno-economic analysis and LCA of hydrogen production pathways from biomass.•Impact of gasification technology on the performance of each pathway.•Hydrogen production with negative life cycle greenhouse gas emissions.
The gasification process converts any carbon-containing material into a synthesis gas composed primarily of carbon monoxide and hydrogen, which can be used as a fuel to generate electricity or steam ...or used as a basic chemical building block for a large number of uses in the petrochemical and refining industries. Gasification adds value to low or negative value feedstocks by converting them to marketable fuels and products. This is the first book to cover gasification as a comprehensive topic, covering its many uses, from refining, to natural gas, to coal. This book provides an up-to-date overview of commercial processes and covers applications relevant to today's demands. The new edition is expanded and provides more detail on the integration issues for current generation, state-of-the-art Integrated Gasification Combined Cycles (IGCC); CO2 capture in the IGCC context addressing the issues of pre-investment and retrofitting as well as defining what the term "CO2 capture ready" might mean in practice; issues of plant reliability, availability and maintainability (RAM) including as evaluation of feedback from existing plants; implementation of fuel cell technology in IGCC concepts. This second edition contains statistics, processes and projects, including descriptions of a number of processes, that were not covered in the previous first edition.
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•(Co–)gasification assisted by CO2 or steam was studied for CR, RH, SB and FR.•Multi-faceted synergistic indices based on various parameters were introduced.•FR showed the best ...performance in terms of weight loss and syngas generation.•Synergistic indices of FR + CR were 4–12 times higher than those of RH + CR and SB + CR.•Water-washing pretreatment of FR proved the positive role of acidic properties.
Gasification technology is an effective way to achieve efficient, safe, and resourceful disposal of organic solid wastes (OSWs). Due to the complex sources and variable components of the OSWs, the co-disposal is highly essential. Various typical OSWs, including food waste (cooked rice, CR), agricultural waste (rice husk, RH; sugarcane bagasse, SB), and industrial waste (furfural residue, FR), were selected for this study. The gasification characteristics and synergistic performance were examined in terms of thermal weight loss characteristics under the CO2 atmosphere and gaseous product characteristics under the steam atmosphere. The synergistic indices of performance parameters were introduced to quantify the synergistic effects. The gasification activity of FR was remarkably higher than that of other OSWs. In the co-gasification with CR under the CO2 atmosphere, FR played an excellent positive synergistic effect, but the agricultural wastes played a slight or no synergistic effect. In the steam co-gasification, RH, SB, and FR all promoted the generation of syngas, in which FR showed still significant synergistic effects, with the synergistic indices of H2 yield, syngas yield, CCE, and CGE being 4–12 times higher than those of other blended wastes. The excellent performance of FR in (co–)gasification was mainly attributed to the acidic properties of FR, which was confirmed by comparing the (co–)gasification performance of FR with and without water-washing pretreatment. The work provides guidance for the co-disposal of OSWs in industrial applications.
•Exhaust gases can enhance the thermodynamics of gasification in integrated cycles.•Exhaust temperature, composition, and flow rate affect gasification conditions.•Syngas dilution with CO2 and N2 ...increases for high levels of exhaust recycling.•Dilute syngas causes low gasification temperatures, limiting gasifier thermodynamics.•N2 dilution effects are quantified in terms of cycle efficiency and CO2 emissions.
Partially recycling CO2-rich exhaust gases from a syngas fuelled internal combustion engine to a biomass gasifier has the capability to realise a new method for direct carbon dioxide utilisation (CDU) within a bioenergy system. Simulation of an integrated, air-blown biomass gasification power cycle was used to study thermodynamic aspects of this emerging CDU technology. Analysis of the system model at varying gasifier air ratios and exhaust recycling ratios revealed the potential for modest system improvements under limited recycling ratios. Compared to a representative base thermodynamic case with overall system efficiency of 28.14 %, employing exhaust gas recycling (EGR) enhanced gasification system efficiency to 29.24 % and reduced the specific emissions by 46.2 g-CO2/kWh. Further investigation of the EGR-enhanced gasification system revealed the important coupling between gasification equilibrium temperature and exhaust gas temperature through the syngas lower heating value (LHV). Major limitations to the thermodynamic conditions of EGR-enhanced gasification as a CDU strategy result from the increased dilution of the syngas fuel by N2 and CO2 at high recycling ratios, restricting equilibrium temperatures and reducing gasification efficiency. N2 dilution in the system reduces the efficiency by up to 2.5 % depending on the gasifier air ratio, causing a corresponding increase to specific CO2 emissions. Thermodynamic modelling indicates pre-combustion N2 removal from an EGR-gasification system could decrease specific CO2 emissions by 9.73 %, emitting 118.5 g/kWh less CO2 than the basic system.
Gasification is an efficient process to obtain valuable products from biomass with several potential applications, which has received increasing attention over the last decades. Further development ...of gasification technology requires innovative and economical gasification methods with high efficiencies. Various conventional mechanisms of biomass gasification as well as new technologies are discussed in this paper. Furthermore, co-gasification of biomass and coal as an efficient method to protect the environment by reduction of greenhouse gas (GHG) emissions has been comparatively discussed. In fact, the increasing attention to renewable resources is driven by the climate change due to GHG emissions caused by the widespread utilization of conventional fossil fuels, while biomass gasification is considered as a potentially sustainable and environmentally-friendly technology. Nevertheless, social and environmental aspects should also be taken into account when designing such facilities, to guarantee the sustainable use of biomass. This paper also reviews the life cycle assessment (LCA) studies conducted on biomass gasification, considering different technologies and various feedstocks.
To gain an in-depth understanding of AAEMs (alkali and alkaline earth metals) transformation during biomass gasification, a fixed-bed reactor is built to simulate the CO2 gasification at 500–900 °C. ...The influences of biomass species, gasification temperature, and particle size are examined. The results show that the AAEMs release follow a sequence of candlenut wood > wheat straw > corn stalk. The alkali metals mainly appear as water-soluble inorganic salts and the contents are more than 80%. K mainly occurs as KCl and KClO4. At higher temperatures, K could combine with Al and Si to form K(AlSi3)O8. For candlenut wood, a bigger particle size is beneficial to the transformation of water-soluble K to organic K. For candlenut wood with centimeter-scale, K mainly occurs as organic K in the biochar during 600–700 °C. When the gasification is carried out at 700 °C, K concentrates at the center and its content is even higher than that on the outer surface. While for biochar samples obtained from gasification at 600 and 900 °C, the K content at the center is lower than that on the outer surface due to the continuous outward transformation of K from the central biochar.
•AAEMs release follow an order of candlenut wood > wheat straw > corn stalk.•K can combine with Al and Si to form K(AlSi3)O8 above 900 °C.•Bigger particle is beneficial to transformation of water-soluble K to organic K.•K spatial transformation is related to its occurrence mode and diffusion rate.
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