Correlation index

The correlation index, developed by the U.S. Bnrean of Mines, is based on a plot of specific gravity versns the reciprocal of the boiling point in kelvin (K =°C + 273). For pure hydrocarbons, the line described by the constants of the individnal members of the normal paraffin series is given the value Cl = 0, and a parallel line passing throngh the point for the values of benzene is given as Cl = 100 thus, 

Values for the index between 0 and 15 indicate a predominance of paraffinic hydrocarbons in the fraction. A value from 15 to 50 indicates a predominance of either naphthenes or of mixtures of paraffins, naphthenes, and aromatics. An index value above 50 indicates a predominance of aromatic species. 

---

Smith, H.M. (1940), "Correlation index to aid interpreting crude oil analysis". US Bureau of Mines, techn. paper No. 610, p. 54. 

American Petroleum Institute atmospheric residue atmospheric residue hydroconversion American Society for Testing and Materials Association pour la Valorisation des Huiles Lourdes Anstalt fur Verbrennungskraftmaschinen List Bureau of Mines Correlation Index bromine number... 

Aromaticity is the most important property of a carbon black feedstock. It is generally measured by the Bureau of Mines Correlation Index (BMCI) and is an indication of the carbon-to-hydrogen ratio. The sulfur content is limited to reduce corrosion, loss of yield, and sulfur in the product. It may be limited in certain locations for environmental reasons. The boiling range must be low enough so that it will be completely volatilized under furnace time—temperature conditions. Alkane insolubles or asphaltenes must be kept below critical levels in order to maintain product quaUty. Excessive asphaltene content results in a loss of reinforcement and poor treadwear in tire appHcations. 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

A correlation index is a useful criterion for indicating the crude class or type. The following relationship between the mid-hoiling point in Kelvin degrees (°K) and the specific gravity of a crude oil or a fraction yields the correlation index (Bureau of Mines Correlation index). 

Selling the DO as CBFS yields a better return than selling it as cutter stock. To meet the CBFS specification, DO must have a minimum Bureau of Mines Correlation Index (BMCI) of 120 and a low ash content (Table 6-2). Aromaticity and ash content are the two most important properties of CBFS. 

Figure 9.2 Mass spectra of the same E. coli strain, JM109, acquired under conditions of (a) high- (-12.5 iJ) and (b) low- (-7 pJ) light intensities. Interval correlation values are shown for the comparison of the two spectra. The composite correlation index value, the product of the 13 interval values, is 0.573.

Figure 9.2 displays a division of the mass range into 13 intervals. After multiplication of all the individual normalized correlation values, the composite correlation index is smaller and the method achieves more selectivity than it would if a single correlation function were calculated over the full mass range. A lower limit of 0.0001 was placed on the value for each normalized interval comparison to prevent the method from generating absurdly low values. These... 

Figure 9.3 Mass spectra of four different E. coli strains (a) AD4, (b) DH5, (c) LE3, and (d) Y10. Composite correlation indexes derived by comparing these spectra to one another are listed in Table 9.1.

TABLE 9.1 Composite Correlation Indexes for Modified Correlation of Spectra in Figure 9.3... 

The selection of steam cracker feedstock is mainly driven by market demand as different feedstock qualities produce different olefins yields. One of the commonly used feed quality assessment methods in practice is the Bureau of Mines Correlation Index (BMCI) (Gonzalo et al., 2004). This index is a function of average boiling point and specific gravity of a particular feedstock. The steam cracker feed quality improves with a decrease in the BMCI value. For instance, vacuum gas oil (VGO) has a high value of BMCI and, therefore, is not an attractive steam cracker feed. The commonly used feedstocks in industry are naphtha and gas oil. 

The correlation index, Cl, was originally devised by H. M. Smith from the U.S. Bureau of Mines in 1940 and it relates the average boiling point of a feed to its spe-cihc gravity. It is defined by the following empirical formula ... 

FIGURE 12.9 Correlation index Cl predicted from H-NMR spectra versus calculated from original H. M. Smith s formula. 

The library search is a mathematical comparison of the unknown compound s spectrum with that of all reference compounds in the database. The aim of the comparison is to find the spectrum that most resembles that of the unknown compound. At the end of the search, the computer software makes a list of all spectra that resemble the unknown spectrum. The software lists the spectra relative to the unknown, along with a reliability or correlation index, irrespective of the library used. Because the object of the library search is to help the analyst and not act as a substitute for him/her, the analyst must manually examine the results. The best approaches to identification are interactive approaches in which the analyst can define filters to reduce the field of investigation. Several different algorithms are used for comparison and can lead to different spectra listings. 

The algorithm that uses absolute difference is rapid and simple. For each of the j spectra in the library and n points along the abscissa, the sum St is calculated as the absolute difference between the ordinate of the unknown and that of the corresponding spectrum j in the library (equation (10.10)). Then the summations Sj are ranked. The results are presented along with a correlation index. 

Important characteristics determining the quality of a feedstock are the C/H ratio as determined by elemental analysis and the BMC Index [4.7] (Bureau of Mines Correlation Index), which is calculated from the density and the mid-boiling point resp. the viscosity. Both values give some information on the aromaticity and therefore the expected yield. Further characteristics are viscosity, pourpoint, alkaline content (due to its influence on the carbon black structure), and sulfur content, which should be low because of environmental and corrosion considerations. 

The resulting equation, correlation index R2, and error about the regression line are shown in Figure 3. The correlation index, R2 = 0.77, indicates that 77% of the sum of squares is explained by the model in Equation 1. Two other possible variables that might have contributed... 

Our studies indicate the presence of dieldrin in some samples and DDT plus DDE in all samples of human tissues that were assayed. Total body burdens of DDT ranging from 22 to 300 mg. were estimated. Greater than 95% of the total body burden of DDT plus DDE was found in the fat. Although the actual concentration of DDT plus DDE in the blood is small, the correlation index, R2 = 0.77, indicates a positive correlation between the fat and blood assays. 

The distribution of compounds produced by this operation is quite different from that obtained from naphtha. The main reason for this is the pronounced aromaticity" of gas oils, which affects the maximum ethylene yield. Moreover, this parameter may substantially from one gas oil to another, and in comparable ojserating conditions this partly explains the wide differences observed in the distribution of the hydrocarbons formed. The Stone and Webster Company established a correlation between the BMCI (Bureau of Mines Correlation Index) for gas oils and the maximum ethylene yield. The BMCL created in 1940, represents an aromaticity index" deOned by the foDowing equation ... 

For three narrow fractions with midcut boiling points of 235°-325°C, the Bureau of Mines Correlation Index (BMCI) is 42-45, respectively. 

In all cases the BET isotherm fits satisfactory with correlating index of about... 

---