Feedstock characterization

The feedstock used in our experiments was Maya crude oil whose main properties are reported in Table 9.1. Sulfur content in feedstock and products was determined with an HORIBA eqnipment (SLFA-2100), by using the standard ASTM D-4294 method. Boiling point curve was obtained by simnlated distillation by using the ASTM D-5307 method. 

Concentrations of nickel and vanadium in feed and products were carried out in an atomic absorption spectrometer (SOLAAR AA). A sample of 4g was used for each measurement. The sample was diluted with HNO3 solution and burned in order to remove the liquid. After that, the sample was calcined by 5 h at 500°C. After calcination, a mixtnre of HCl and HNO3 was added to the sample, and metals were quantified. 

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Improved feedstock characterization is needed in order to accurately and reliably assess impacts on system performance. 

Feedstock Characterization. The feedstocks studied in this effort were a Wilmington vacuum gas oil and two hydrotreated products of this gas oil. The specific samples considered were sample No. 1693, an untreated Wilmington vacuum gas oil, a low severity hydrotreated product from sample No. 1693 (sample No. WM-2-2R, hydrotreated at 375° C, 1.5 LHSV, and 1500 psig), and a high severity hydrotreated product (sample No. WM-2-9, hydrotreated at 425° C, 0.5 LHSV, 1500 psig). The available physical properties for each of these feedstocks are given in Table I. 

Figures 10 and 11 show some examples of model predictions of the feedstock characterization of crude distillation residues. Figure 10 compares model predictions with the experimental distillation curves of three Arabian atmospheric residues. Figure 11 shows the model ability in predicting the aromatic carbon content and the H/C of different feeds in comparison with some NMR data. A more detailed description and discussion of this residue characterization is reported elsewhere (Bozzano et al., 1995, 1998).

Detailed kinetic schemes also consist of several hundreds of species involved in thousands of reactions. Once efficient tools for handling the correspondingly large numerical systems are available, the extension of existing kinetic models to handle heavier and new species becomes quite a viable task. The definition of the core mechanism always remains the most difficult and fundamental step. Thus, the interactions of small unsaturated species with stable radicals are critical for the proper characterization of conversion and selectivity in pyrolysis processes. Parallel to this, the classification of the different primary reactions involved in the scheme, the definition of their intrinsic kinetic parameters, the automatic generation of the detailed primary reactions and the proper simplification rules are the important steps in the successive extension of the core mechanism. These assumptions are more relevant when the interest lies in the pyrolysis of hydrocarbon mixtures, such as naphtha, gasoil and heavy residue, where a huge number of isomers are involved as reactant, intermediate and final products. Proper rules for feedstock characterizations are then required for a detailed kinetic analysis. 

The described regularities are not strictly valid for the heaviest types of oil feedstock characterized by availability of dense radiation-resistant low-temperature colloid structures. In this case, dose and... 

These feedstock characterizations were the starting point for the development of the reaction network using Boolean relation matrices and characteristic vectors. Components of a hydrocarbon family which are known to be at equilibrium were grouped so as to limit the number of continuity equations to be integrated in reactor simulations. 

Pena-Diez, J.L. Improved Refinery Planning and Operation Through Better Feedstock Characterization , AspenWorld 2002, Washington,D.C.,October 27 -November 1, 2002. 

Nevertheless, within the same work group, once the chromatographic procedures are established, SARA analyses are very often performed to characterize heavy feedstocks or to follow their conversion. 

This equation relates the composition of the copolymer formed to the instantaneous composition of the feedstock and to the parameters rj and r2 which characterize the specific system. Figure 7.1 shows a plot of Fj versus fj-the mole fractions of component 1 in the copolymer and monomer mixture, respec-tively-for several arbitrary values of the parameters rj and r2. Inspection of Fig. 7.1 brings out the following points ... 

The market penetration of synthetic fuels from biomass and wastes in the United States depends on several basic factors, eg, demand, price, performance, competitive feedstock uses, government incentives, whether estabUshed fuel is replaced by a chemically identical fuel or a different product, and cost and availabiUty of other fuels such as oil and natural gas. Detailed analyses have been performed to predict the market penetration of biomass energy well into the twenty-first century. A range of from 3 to about 21 EJ seems to characterize the results of most of these studies. 

Coumarone—indene or coal-tar resins, as the name denotes, are by-products of the coal carbonization process (coking). Although named after two particular components of these resins, coumarone (1) and indene (2), these resins are actually produced by the cationic polymerization of predominantly aromatic feedstreams. These feedstreams are typically composed of compounds such as indene, styrene, and their alkylated analogues. In actuaUty, there is very tittle coumarone in this type of feedstock. The fractions used for resin synthesis typically boil in the range of 150—250°C and are characterized by gas chromatography. 

Synthesis Gas Preparation Processes. Synthesis gas for ammonia production consists of hydrogen and nitrogen in about a three to one mole ratio, residual methane, argon introduced with the process air, and traces of carbon oxides. There are several processes available for synthesis gas generation and each is characterized by the specific feedstock used. A typical synthesis gas composition by volume is hydrogen, 73.65% nitrogen, 24.55% methane, <1 ppm-0.8% argon, 100 ppm—0.34% carbon oxides, 2—10 ppm and water vapor, 0.1 ppm. 

The hterature consists of patents, books, journals, and trade Hterature. The examples in patents may be especially valuable. The primary Hterature provides much catalyst performance data, but there is a lack of quantitative results characterizing the performance of industrial catalysts under industrially reaHstic conditions. Characterizations of industrial catalysts are often restricted to physical characterizations and perhaps activity measurements with pure component feeds, but it is extremely rare to find data characterizing long-term catalyst performance with impure, multicomponent industrial feedstocks. Catalyst regeneration procedures are scarcely reported. Those who have proprietary technology are normally reluctant to make it known. Readers should be critical in assessing published work that claims a relevance to technology. 

Develop procedures to characterize feedstock whenever changes have been made and reevaluate milling conditions... 

The chemical process industries (CPI), petroleum and allied industries apply physical as well as chemical methods to the conversion of raw feedstock materials into salable products. Because of the diversity of products, process conditions and requirements, equipment design is often unique, or case specific. The prime requirement of any piece of equipment is that it performs the function for which it was designed under the intended process operating conditions, and do so in a continuous and reliable manner. Equipment must have mechanical reliability, which is characterized by strength, rigidness, steadiness, durability and tightness. Any one or combination of these characteristics may be needed for a particular piece of equipment. 

FCC feed characterization is one of the most important activities in monitoring cat cracking operation. Understanding feed properties and knowing their impact on unit performance are essential. Troubleshooting, catalyst selection, unit optimization, and subsequent process evaluation all depend on the feedstock. 

Feed characterization relates product yields and qualities to feed quality. Knowing the effects of a feedstock on unit yields, a refiner can purchase the feedstock that maximizes profitability. It is not uncommon for refiners to purchase raw crude oils or FCC feedstocks without knowing their impact on unit operations. This lack of knowledge can be expensive. 

Characterizing an FCC feedstock involves determining both its chemical and physical properties. Because sophisticated analytical techniques, such as mass spectrometry, are not practical on a daily basis, physical properties are used. They provide qualitative measurement of the feed s composition. The refinery laboratory is usually equipped to carry out these physical property tests on a routine basis. The most widely used properties are ... 

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. 

Specifications for chromatographic packings often describe maximum loading in terms of the maximum capacity of a unit quantity of the packing to bind some analyte, often a well characterized protein such as bovine serum albumin. The static loading capacity35 is very different from functional capacity,2 which is the maximum amount of a particular feedstock that can be loaded and still achieve acceptable purification and recovery. Functional capacity is determined empirically for each type of load and associated set... 

QA/QC laboratories. The QA/QC lab is responsible for the testing of feedstocks and raw materials, process intermediates, and finished goods, and may, in addition, be responsible for the development of standards for materials, processes, and procedures. The QA/QC lab is usually characterized by the routine, repetitive nature of its workload. Testing is primarily to specification and, where lot acceptance or rejection is involved, is often on a grade category or pass/fail basis. Data may be archived for compliance with regulatory directives and for analyses of trends In material or process performance. 

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