Effect of Feedstock Composition

The thermal chemistry of heavy oils and bitumen is extremely complicated because of wide variations in chemical compositions. The most refractory components in petroleum feedstocks are asphaltenes, which contribute the most to coke formation dining thermal cracking. Next to asphaltenes, resins and large aromatics also contribute to coke. To investigate the effect of these three heavy oil components on the mesophase induction period, Athabasca bitumen fractions containing varying amounts of asphaltenes (obtained by supercritical fluid extraction) and Venezuelan heavy 

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Fig. 33.19. Effect of feedstock composition on minimum ethanol selling price (MESP).

J. Scherzer and d.P. McArthur "Catalytic Cracking of High Nitrogen Petroleum Feedstocks Effect of Catalyst Composition and Properties", Ind. Eng. Chem. Res. 1988, 27, p 1571-1576. 

Fortunately, the effects of most mobile-phase characteristics such as the nature and concentration of organic solvent or ionic additives the temperature, the pH, or the bioactivity and the relative retentiveness of a particular polypeptide or protein can be ascertained very readily from very small-scale batch test tube pilot experiments. Similarly, the influence of some sorbent variables, such as the effect of ligand composition, particle sizes, or pore diameter distribution can be ascertained from small-scale batch experiments. However, it is clear that the isothermal binding behavior of many polypeptides or proteins in static batch systems can vary significantly from what is observed in dynamic systems as usually practiced in a packed or expanded bed in column chromatographic systems. This behavior is not only related to issues of different accessibility of the polypeptides or proteins to the stationary phase surface area and hence different loading capacities, but also involves the complex relationships between diffusion kinetics and adsorption kinetics in the overall mass transport phenomenon. Thus, the more subtle effects associated with the influence of feedstock loading concentration on the... 

Variations in Product Due to Feedstock. While process-related differences in product composition have been evident, extensive study of the effect of feedstock on product composition has never been undertaken. Some limited comparative tests can be gleaned from the literature however, most process research in direct liquefaction of biomass has been performed with woods of various species. Table I provides some of the results available in the literature for non-woody feedstocks. Significant differences in heteroatom content are evident, but only limited chemical analysis is available in most cases. 

The comparison of the peat and wood flash pyrolysis products by Elliott ( ) is a good example of the effect of feedstock on product oil composition. The poplar oil typically was composed of phenolic, ketone and furan compounds with a substantial fraction of low molecular weight organic acids. The main components of the peat oil were hydrocarbons, mostly straight chain olefins. Minor quantities of ketones were noted but no acids, aldehydes or furans were identified by mass spectrometry. Phenols were also present in significant quantities. 

The effect of butene isomer distribution on alkylate composition produced with HF catalyst (21) is shown in Table 1. The alkylate product octane is highest for 2-butene feedstock and lowest for 1-butene isobutylene is intermediate. The fact that the major product from 1-butene is trimethylpentane and not the expected primary product dimethylhexane indicates that significant isomerization of 1-butene has occurred before alkylation. 

In the previous examples, the feed characterizing correlations in Chapter 2 are used to determine composition of the feedstock. The results show that the feedstock is predominantly paraffinic (i.e., 61.6% paraffins. 19.9% naphthenes, and 18.5% aromatics). Paraffinic feedstocks normally yield the most gasoline with the least octane. This confirms the relatively high FCC gasoline yield and low octane observed in the test run. This is the kind of information that should be included in the report. Of course, the effects of other factors, such as catalyst and operating parameters, will also affect the yield structure and will be discussed. 

In addition to the use of composite anodes and cathodes, another commonly used approach to increase the total reaction surface area in SOFC electrodes is to manipulate the particle size distribution of the feedstock materials used to produce the electrodes to create a finer structure in the resulting electrode after consolidation. Various powder production and processing methods have been examined to manipulate the feedstock particle size distribution for the fabrication of SOFCs and their effects on fuel cell performance have also been studied. The effects of other process parameters, such as sintering temperature, on the final microstructural size features in the electrodes have also been examined extensively. 

Therefore, in this chapter we describe major refinery operations and the products therefrom and focus on their composition, properties, and uses. This presents to the reader the essence of petroleum processes, the types of feedstocks employed, and the product produced, as well as warning of the types of the chemicals that can be released to the environment when an accident occurs. Being forewarned offers an environmental analyst the ability to design the necessary test methods to examine the chemical(s) released. It offers environmental scientists and engineers the ability to start forming opinions and predictions about the nature of the chemical(s) released, the potential effects of the chemical(s) on the environment, and the possible methods of cleanup. 

The effect of fines content on the combustion of pulverized coal is quite dramatic (Field et al., 1967 Essenhigh, 1981), and the problems associated with collection of an unbiased sample of pulverized coal need attention (ASTM D-197). Operating samples are often collected from the feedstocks to power plant boilers on a shift or daily basis for calculation of heat balances and operating efficiencies. Another objective of operating samples is to document compliance with air pollution emission regulations based on fuel composition. 

The effects of reactor type, process variables and feedstock type, catalysts, and feedstock composition (Chapters 5 and 6) on the desulfurization process provide a significant cluster of topics through which to convey the many complexities of the process. In the concluding chapters, examples and brief descriptions of commercial processes are presented (Chapter 7) and, of necessity, some indications of methods of hydrogen production (Chapter 8) are also included. 

Nevertheless, there have been some successful attempts to define the behavior of residua (and heavy oils) during the hydrodesulfurization process in terms of physical composition, which has also led to the development of process modifications to suit various heavy feedstocks. This line of investigation arose because of the tendency, over the years, to classify all residua (and heavy oils) as the same type of refinery discard which was, effectively, useless for further processing. The only exception is the production of asphalt from certain residua. It was only when... 

Three issues are discussed under this heading (1) the effect that different feed materials might have on the propensity for PCDD/F formation in combustors (2) whether restrictions in feedstock composition are likely to have a beneficial effect in terms of reduced PCDD/F emissions (3) whether the manner in which the feedstock is presented to the combustor influences PCDD/F formation. Each issue is discussed below. 

Gravimetric Results of Catalytic Cracking. Experiments were conducted to assess the effects of temperature, cat-to-oil ratio, and feedstock composition. In addition to the effect of variables on product yields, it was also important to identify the relative influence of thermal reactions, since free-radical reactions may adversely affect product quality. A series of experiments was conducted in the temperature range of 412°-415°C because this is the temperature of maximum increase in production from thermal cracking and catalytic vs. thermal effects are more easily discernible at this temperature. 

Compositional variability can have a significant impact on biomass conversion process economics. The large effect (i.e., at least 0.30/gal ethanol) of observed compositional diversity on process economics is shown in Fig. 33.19 and is primarily due to the fact that the maximum theoretical product yield is proportional to feedstock carbohydrate content (Fig. 33.20).131 Yield is the major economic driver for the technoeconomic model used to assess the economic impact of composition on minimum product selling price,130 as can be seen from the data in Fig. 33.21. 

By varying both initial and final boiling points of the feedstock, octane numbers, reformate yields and composition as well as gas yields were measured in a once-through, isothermal pilot reactor. The effect of the feedstock boiling point properties on catalyst deactivation was also studied. 

Knowledge of the effects of various independent parameters such as biomass feedstock type and composition, reaction temperature and pressure, residence time, and catalysts on reaction rates, product selectivities, and product yields has led to development of advanced biomass pyrolysis processes. The accumulation of considerable experimental data on these parameters has resulted in advanced pyrolysis methods for the direct thermal conversion of biomass to liquid fuels and various chemicals in higher yields than those obtained by the traditional long-residence-time pyrolysis methods. Thermal conversion processes have also been developed for producing high yields of charcoals from biomass. 

Rodriguez, I. (1996) Ph.D. Thesis Composition Related Effects of Thermal Reactivity of Organic Feedstocks, Univ. of Washington, Dept of Chemical Engineering. 

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