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Cultivation and Conversion of Algae for Wastewater Treatment and Biofuel Production
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Priyanka Yadav, Sivamohan N. Reddy, Sonil Nanda
Combustion is an exothermic process in which different organic components react with oxygen to generate heat energy and steam that can be used to turn turbines to generate electricity. Gasification is thermal degradation of organic matter with a limited supply of oxygen to produce combustible synthesis gas (a mixture of CO and H2). Pyrolysis is the thermal degradation of organic substances in an inert atmosphere to produce bio-oil, biochar, and gases. Liquefaction is a biomass-to-liquid conversion technology that mostly produces bio-oil and traces of tar and char. The bio-oil obtained from liquefaction contains less oxygen and moisture compared to pyrolysis-derived bio-oil, which results in its high-energy value (Nanda et al. 2014). Hydrothermal liquefaction is basically a hydrothermal conversion technique that uses hot-pressurized water acting as the reaction medium to solubilize the biomass directly to bio-oil. In the hydrothermal gasification process, the reaction temperature is greater than 350°C in the absence of an oxidizing agent, which generates a gas phase containing H2, CO, CO2, CH4, and C2+ components. Hydrothermal gasification also uses subcritical and supercritical water to hydrothermally decompose algae to produce H2-rich syngas. Hydrothermal carbonization transforms biomass into hydrochar at a comparatively lower temperature in the range of 180°C–250°C and pressures of 2–10 MPa.
Compositional and Structural Modification of Lignocellulosic Biomass for Biofuel Production by Alkaline Treatment
Published in Jaya Shankar Tumuluru, Biomass Preprocessing and Pretreatments for Production of Biofuels, 2018
Kingsley L. Iroba, Majid Soleimani, Lope G. Tabil
Hydrothermal liquefaction is a biofuel production technology with the capability of converting lignocellulosic or other types of biomass to bio-oil (Zhou et al., 2011). Hydrothermal liquefaction can be performed under neutral, acidic, or alkaline conditions. Various alkaline substances have been used as catalysts for alkaline liquefaction of plant-based materials, including sodium carbonate, potassium carbonate, potassium hydroxide, sodium hydroxide, and calcium hydroxide. Yin and Tan (2012) conducted liquefaction reactions at different pH levels (3, 7, and 14-provided by sodium hydroxide), and temperature and residence time in the range of 275–320°C and up to 30 min, respectively. They reported that under neutral and acidic conditions, the bio-oil mainly composed of 5-hydroxymethyl furfural (HMF), however, the bio-oil from liquefaction under alkaline condition mainly composed of C2–5 carboxylic acids. Under the alkaline condition, lignocellulosic biomass would be mainly liquefied to bio-oil, although the original reaction medium is aqueous. Bio-oil is a complex liquid made of a wide range of chemical compositions. The typical components of bio-oil are glycol aldehyde dimers, anhydroglucose, 1, 3-dihydroxyacetone dimers, 5-HMF, furfural, polyols, organic acids, hydrocarbons, and phenolic compounds (Zhou et al., 2011). In terms of the effect of process parameters in an alkaline medium (using 0.83% sodium carbonate) on reaction rate, it has been shown that cellulose degradation starts at temperatures of less than 533 K, and its decomposition is accelerated at a temperature range of 533 K to 573 K. The generation of bio-oil was reported to occur at temperatures of over 533 K with maximum yields at temperature range of 593 K to 613 K (Minowa et al., 1997). In a similar investigation by Karagoz et al. (2004) who conducted liquefaction using hydrothermal and alkaline catalyzed processes, it was reported that at a lower temperature (180°C for 15 min) of a hydrothermal process, 26.7 wt% of sawdust was convertible with a total oil yield of 3.7 wt%. Total oil yield was increased to 7.6 wt% and 8.5 wt% by increasing process temperature to 250°C (for 15 min) and 280°C (for 15 min), respectively. By conducting the liquefaction in the presence of calcium hydroxide at 280°C (for 15 min), a higher oil yield of 9.3 wt% and gas yield of 11.9% was obtained. Therefore, they concluded that a higher oil yield but lower water-soluble products are achievable in alkaline catalyzed liquefaction compared to the hydrothermal process.
Energy from biomass and plastics recycling: a review
Published in Cogent Engineering, 2021
Samuel Oluwafikayo Adegoke, Adekunle Akanni Adeleke, Peter Pelumi Ikubanni, Chiebuka Timothy Nnodim, Ayokunle Olubusayo Balogun, Olugbenga Adebanjo Falode, Seun Olawumi Adetona
The four main thermochemical conversion processes include liquefaction, gasification, direct combustion, and pyrolysis (Egorov & Strizhak, 2017; Lissianski et al., 2002). Pyrolysis has been found to have the best and the most efficient thermochemical conversion process with its processing cost higher by $3.27 compared to cost of processing one gallon of gasoline fuel (Hossain et al., 2014; Syahirah et al., 2020). Hydrothermal liquefaction is the process of converting biomass into liquid by thermochemical steps in the presence of supercritical water, less temperature (250–350°C) and high pressure (5–20 MPa) (Huang et al., 2011). Hydrothermal liquefaction produces a higher heating value and lowers oxygen content compared to pyrolysis (Choudhary et al., 2020; Durak, 2019). During liquefaction, there is first, the process of hydrolysis where the biomass is broken into pieces, followed by the process of degradation into smaller components, such as dehydration, de-oxygenation, further to decarboxylation, and finally to depolymerization (Ibarra-gonzalez & Rong, 2018).
A critical review of separation technologies in lignocellulosic biomass conversion to liquid transportation fuels production processes
Published in Chemical Engineering Communications, 2022
Paola Ibarra-Gonzalez, Lars Porskjaer Christensen, Ben-Guang Rong
The products from hydrothermal liquefaction are bio-oil, a gaseous stream containing carbon dioxide, biochar and an aqueous phase with small concentrations of soluble organic compounds. For example, the bio-crude produced from algae contains high concentrations of dry solids of up to 34 wt.% (Elliott et al. 2015), leading to low bio-oil yield. As observed, the yield of the bio-crude is a function of the concentration of dry solids in the wet feedstock. As the product from liquefaction is already in liquid phase then filtration is a viable technique for separation of solids. Posmanik et al. (2017) and Karagöz et al. (2005) performed the separation of solids from the aqueous, and oil phases by vacuum filtration.