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Hydrothermal Carbonization (HTC) of Biomass for Energy Applications
Published in Jaya Shankar Tumuluru, Biomass Preprocessing and Pretreatments for Production of Biofuels, 2018
S. Kent Hoekman, Amber Leland, Larry Felix
The van Krevelen diagram is a useful way to illustrate the degree of “coalification” that has occurred through HTC processing, and hence, the fuel value of the produced hydrochar. Originally proposed by van Krevelen and co-workers in 1960 (Schuhmacher et al., 1960), the diagram plots atomic H/C ratios vs. atomic O/C ratios. An example diagram is provided in Fig. 13, where it is used to show the increasing coal-like behavior of hydrochar from loblolly pine, as it is produced under increasingly severe process conditions. The colored shapes indicate regions where typical biomass, peat, lignite, and coal appear. Thus, Fig. 13 illustrates how hydrochar changes from being ‘peat-like’ to being ‘coal-like’ as the HTC process severity increases. The solid and dashed guidelines shown on this van Krevelen diagram indicate directional changes that biomass and its chars would undergo as a consequence of three chemical processes: dehydration, decarboxylation, and demethylation. An inspection of Fig. 13 indicates that HTC treatment of loblolly pine is dominated by dehydration with a lesser contribution from decarboxylation. The general behaviors seen in Fig. 13 are typical of many biomass feedstocks.
Production of Bio-Oil
Published in M.R. Riazi, David Chiaramonti, Biofuels Production and Processing Technology, 2017
Kevin M. Van Geem, Ismaël Amghizar, Florence Vermeire, Ruben De Bruycker, M.R. Riazi, David Chiaramonti
Biomass is generally defined as organic matter generated by photosynthesis. This is biological material that stems from living or recently living organisms. Besides plant-based material, animal- and vegetable-based material can be considered. Since the origin of biomass is so versatile, there are a lot of possibilities to classify it. For instance, biomass can be classified based on origin, and chemical or elemental composition. The diversity regarding the elemental composition of biomass is visualized through the van Krevelen diagram presented in Figure 8.2. In this chapter, two types of biomass for the production of renewable chemicals and fuels will be discussed.
Petroleum Geochemical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
The van Krevelen diagram (VKD) predicts the petroleum-generating capacity of source rock organic matter and maturation of kerogen. The van Krevelen diagram elaborates the kerogen maturation. The maturation process is associated with changes in the chemical structure of the kerogen, the generation of hydrocarbons, oil, wet and dry gases and non-hydrocarbon gases. The van Krevelen diagram is based on elemental analysis and calculated H/C and O/C atomic ratios. The diagram is a plot of the H/C ratio versus the O/C ratio of kerogen I, II, III and IV. Type I is saprogenic, type II is mixed (saprogenic + humic), type III is humic and type IV is residual kerogen. The maturation path way of kerogen and the transformation to oil/gas/residual carbon during diagenesis, catagenesis and metagenesis can be followed with the help of the diagram (VKD). The characteristics of kerogen are related to the relative distribution of the main elements, hydrogen, oxygen and carbon, in the kerogen, during the maturation process. There is a rapid loss of hydrogen (H/C ratio with respect to carbon) for type I kerogen, followed by type II and III. The hydrogen content is slightly altered in type IV kerogen. Type IV kerogen has an already meager amount of hydrogen atoms (<2%). Also, there is a decrease in the O/C atomic ratio (deoxygenation), first slowly and then quickly, relative to the carbon, with the evolution of CO2 and H2O. The oil/gas produced from the kerogen has a higher hydrogen content. Organic matter, having a higher content of hydrogen (higher H/C atomic ratio) atoms, is likely to produce more oil/gas. The kerogen type I derived from organic matter containing oil, fat, wax, spores, algae, flora and fauna preserved in an aquatic environment has the highest H/C atomic ratio. Kerogen type I generates more oil/gas. Type IV kerogen is devoid of sufficient hydrogen and is of low H/C ratio; there is only minor evolution of gases. It is almost equal to residual carbon, having no capacity to generate oil and very little dry gas. In fact kerogen type IV is reworked from types II and III kerogen. Type II is also oil-prone kerogen whereas type III(humic) is gas-prone kerogen. Four distinct phases are witnessed during kerogen maturation resulting in the progressive generation of (1) water and carbon dioxide, (2) oil/gas, (3) wet gas and (4) dry gas. A summary of the change of H/C and O/C ratios from initial diagenesis to the end of metagenesis is as follows:
Study of Pyrolyzates from a Variety of Indian Coals and Their Dependency on Coal Type and Intrinsic Properties – An Analytical Fast Pyrolysis Study
Published in Combustion Science and Technology, 2022
Devi Prasad Mishra, Kanak Kumar, Jaya Narayan Sahu
The composition of volatile products of coal differs with coal type. When handling a large array of coals, it is useful to group the coals under a certain coal type based on the characteristics of coal (Genetti 1999; Mill 2000; Niksa, Liu, and Hurt 2003). The van Krevelen Diagram (1981) relates two sets of atomic mass ratios, YH/YC, (ratio of mass fraction of hydrogen and carbon) and YO/YC, (ratio of mass fraction oxygen and carbon) with various coal properties. Bindar (2013) proposed a new coal type number (NCT) using the mass fractions of carbon, hydrogen, and oxygen obtained from the ultimate analysis of coal. NCT is unique for each coal and it is represented as follows:
Effect of torrefaction on the fuel characteristics of timothy hay
Published in Biofuels, 2021
Daya Ram Nhuchhen, Muhammad T. Afzal, Ashak Mahmud Parvez
While the carbon content increased, the hydrogen and oxygen contents decreased with torrefaction. The carbon content increased to 59.3% (at 300 °C, 45 min, and 30 °C/min), which was 28.5% more compared to raw TH. Because of the decarboxylation and deoxygenation reactions that occur during the torrefaction process, the oxygen content in the biomass decreases significantly. The reduction in oxygen is caused mainly by removal of water, carbon dioxide, carbon monoxide, and acidic compounds such as acetic acid [53]. The reduced oxygen content in torrefied biomass not only helps to improve fuel quality for combustion, but also helps to produce a more stable bio-oil [54]. Hydrogen contents are also decreased as the torrefaction process removes the carboxylic groups containing the hydrogen molecules. These changes in elemental composition are due to different decompositions and depolymerization reactions of three major polymeric compositions in the lignocellulosic biomass materials. These reactions help in releasing the carboxyl group from hemicellulose, methoxy groups from lignin and carbonyl, and carboxyl groups from cellulose, causing solid mass loss during the process [55]. These changes in the elemental composition can also be used to identify the extent of conversion of biomass to bio-coal using a van Krevelen diagram. Figure 2 shows a typical van Krevelen diagram of different torrefied biomass. It clearly shows how the value moves with torrefaction from that of raw TH toward that of low-rank coal (lignite). The reduction of both the H/C ratio and the O/C ratio achieved after the torrefaction process converts biomass waste into a green bio-coal that could partially replace the consumption of coal. Additionally, the reduced oxygen content in the biomass following torrefaction can improve the gasification process [56,57], but one may note that the torrefied material requires a higher gasification temperature to obtain conversion ratios similar to those of the raw biomass [58].