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Production of Hydrogen through Gasification Technology
Published in Sonil Nanda, Prakash K. Sarangi, Biohydrogen, 2022
The conventional gasification process occurs at high temperatures (typically >700°C), which leads to produces gaseous products and charcoal. The gaseous products are mainly composed of H2, CH4, CO, CO2, and other hydrocarbons. The charcoal is converted to H2, CH4, CO, and CO2. Unlike pyrolysis, the gasification process occurs with gasifying agents such as steam, air, oxygen or a mixture of these components. Produced gases can be reformed by steam to enhance H2 formation and later on reaction between CO and H2O known as water-gas shift (WGS) reaction further increase H2 production (Demirbaş, 2002; Ahmad et al., 2016). Series of complex thermochemical reactions are involved in this process. Therefore, it is not possible to separate the reactor into various zones to perform gasification reactions concurrently. As seen in Figure 2.2, drying, pyrolysis, combustion, reduction, and char gasification steps are involved in the gasification process.
Less Hazardous Chemical Synthesis from Palm Oil Biomass
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
Raja Safazliana Raja Sulong, Seri Elyanie Zulkifli, Fatimatul Zaharah Abas, Muhammad Fakhrul Syukri Abd Aziz, Zainul Akmar Zakaria
Combustion is widely used to burn biomass waste into a charcoal product with the complete presence of oxygen. This process is inconvenient and causes serious air pollution because of extensive smoke formation. The powdery charcoal produced from combustion process can be converted into high energy-concentrated fuel pellets orother different geometric forms (Kibwage et al., 2006). The gasification process is an efficient and environmentally friendly way to produce energy (Hanne et al., 2011). This process is well known in a conversion of biomass fuel into gaseous fuel. This whole process is completed at the elevated temperature range of 800–1300°C (McKendry, 2002). The gaseous fuel generated from gasification is used as an energy in power generation cycles. The liquefaction process operates at a low-temperature and high pressure to break down the biomass waste into fragments of small molecules in water or another suitable solvent (Zhang et al., 2010). Liquefaction has some similarity with pyrolysis where the preferred products is the liquid product. However, in order to operate the liquefaction process, catalysts are essential. Compared with pyrolysis, liquefaction technology is more challenging as it requires more complex and expensive reactors and fuel feeding systems (Demirbas, 2001).
Biomass Energy
Published in Sergio C. Capareda, Introduction to Renewable Energy Conversions, 2019
Thermal conversion processes are biomass conversion processes that utilize high temperatures or heat to convert biomass into useful products. There are basically four types according to the amount of air introduced as well as the temperature used for the reaction. The four thermal conversion processes include (a) torrefaction, (b) pyrolysis, (c) gasification, and (d) combustion. Torrefaction and pyrolysis are reactions that use no oxygen or air, while gasification and combustion both utilize amounts of oxygen or air. Torrefaction is done at lower temperatures, usually below 300°C [572°F], while pyrolysis is done above 300°C [572°F] (Capareda, 2014). Torrefaction is simply a biomass conditioning process— it hardly produces any new product but rather enhances the quality of the biomass in the form of char. Gasification uses incomplete amounts of air (or that below stoichiometry), whereas combustion uses excess amounts of air. As such, the operating temperature for gasification systems is much lower than that of combustion systems. The three thermal conversion systems will be discussed in succeeding sections.
A comprehensive review on techno-environmental analysis of state-of-the-art production and storage of hydrogen energy: challenges and way forward
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Md Rasel Ahmed, Tirtha Barua, Barun K. Das
Because of its significant useful features and broad range of advanced future prospects, biomass gasification has been considered for decades as one of the methods most focused on producing hydrogen. The most common feedstock used in this context is wood, while other waste materials, including wood chips and rice husks, are also being considered (Kirkels and Verbong 2011). As a consequence of numerous studies, new gasification technologies have been developed for a diverse range of biomass materials, such as paper wastes, sugarcane wastes, wastewater sludge, food wastes, palm oil, plastic and wood chips, tree branches, etc. Also, different combinations were found by hydrolyzing biowaste like potato and onion peels with different microbial philosophies to expedite the synthesis of hydrogen from biomass (Patel et al. 2019). About half or even more than 1 liter of gasoline is used in the fermentation methods in the generation of hydrogen (Singh, Asthana, and Singh 2007). By mixing gasoline and hydrogen during his study on hydrogen-based working motors, L. M. Das came to the conclusion that there are no hydrocarbon emissions at all when using pure hydrogen (Das 1991). At a 0.8 equivalent ratio, hydrocarbon emissions are at their lowest possible level.
Plastic waste management via thermochemical conversion of plastics into fuel: a review
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Shah Saud Alam, Afzal Husain Khan, Nadeem Ahmad Khan
Like pyrolysis, gasification is another popular thermochemical method capable of handling multiple waste feeds and mixtures. Gasification involves the controlled partial oxidation of a carbonaceous feedstock into synthesis gas (aka syngas) and other light hydrocarbons at higher temperatures (873.15–1073.15 K) under the effect of a gasifying agent such as air, steam, pure oxygen, or a mixture of these gases (Chan et al. 2019). Air is mainly used as a gasification agent to reduce the overall operational costs, but nitrogen presence reduces the calorific value of syngas. Typically, syngas is used in internal combustion engines for in situ heat and power generation (Ebrahimi and Moradpoor 2016). However, syngas-fueled internal combustion engines’ reported energy generation efficiency is low (15–24%) (Arena 2012). This efficiency can be improved to 30% with the use of combined-cycle gas turbines (Arena et al. 2011) or solid oxide fuel cells (30–40%) (Baldinelli et al. 2016; Pan et al. 2015). Due to these applications, gasification offers optimized utilization of wastes as sustainable energy resources. A significant advantage of gasifiers over incineration and pyrolysis is the lower production of furans and dioxins due to the reducing environment in gasifiers that eliminates residual carbon in the flue gas (Arena 2012). Furthermore, common contaminants such as chlorine-containing species (HCl, KCl, and NaCl) and ash are removed from syngas during the purification stage, further reducing the potential formation of furans and dioxins later (Zhang, Luo, and Yin 2018).
Fuel gas production from asphaltene and recycled polyethylene
Published in Petroleum Science and Technology, 2020
Jia-Ming Zhu, Jia-Bao Liu, Muhammad Kamran Siddiqui, Waqas Nazeer, Yun Liu
Gasification is a process that can play an important role in managing wastes and converting them into energy. Gasification is a thermochemical process that is usually performed in the presence of oxygen, air, steam or their mixture. The quality of gas obtained from the process depends on various factors, including reactor temperature, the amount of oxidizer and the type of fuel used. Since the gasification process is an endothermic one and increasing temperature can significantly increase the quality of produced gas, reactor temperature and the amount of oxidizer are more important than other factors (Higman and van der Burgt 2003; Gomez-Barea and Leckner 2010). The amount of oxidizer is another impactful factor that is often used for increasing the amount of a particular material, like hydrogen. Steam is often used as a gasification agent for producing hydrogen (Kim et al. 1997). Despite steam-gasification’s great potential for producing hydrogen, most of the hydrogen consumed by industries is made through the steam reforming of natural gas process, since the amount of hydrogen produced from the steam reforming process is much more than that produced by the steam-gasification process. Another gasification agent that is not as common is oxygen. Since producing pure oxygen is expensive and requires special processes, using it as a gasification agent is not very economical.