Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
1999-03-03
2001-08-14
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C208S112000, C208S078000, C208S046000, C208S113000
Reexamination Certificate
active
06275776
ABSTRACT:
This invention relates to fluidized catalytic cracking (FCC) of hydrocarbon feed stocks, and more particularly to an improved method to accurately predict characterizing chemistry of heavy residual oils and petroleum mixtures used for FCC feed stocks.
BACKGROUND OF THE INVENTION
Fluidic catalytic cracking continues to be the largest catalytic process in the world, and planning of FCC feed stock allocations continues to be a very complex problem, which must be addressed by petroleum refiners. For example, feeds of high economic opportunity are often heavy oils that require specialized FCC processing including a particular set of operating conditions that will realize a profitable product slate. Understanding the feed chemistry of petroleum crude oils and refinery streams has been a very important research topic for many years. Since FCC processes involve manipulation of carbon and hydrogen bonds, an accurate understanding of the feed composition and chemistry would allow the refiner to control operations involving catalytic and non-catalytic reactions. Ideally, the refiner would divide the feed into individual molecular components, however, petroleum FCC feeds are far too complex, such that the amount of analytic effort would be prohibitive.
Many methods have been suggested in the literature for characterization of petroleum feed stocks. Some researchers combine bulk analytical tests into correlating parameters. For example, the Viscosity Gravity Constant (J. B. Hill and H. B. Coats, Ind. Eng. Chem., 20, 641, 1928) is one such correlating parameter. As the name implies, the parameter uses specific gravity and Saybolt viscosity to characterize the oil. Another early parameter is the Watson K factor (K. M. Watson and E. F. Nelson, Ind. Eng. Chem., 25, 880, 1933), which is the cube root of the mean average boiling point divided by the specific gravity. For a given carbon number, the boiling point and specific gravity increase going from paraffins to naphthenes to aromatics, however, specific gravity increases more rapidly, such that high Watson K factors (greater than 12) correspond to an oil with high paraffinic content and low Watson K factor (less than 12) corresponds to an oil with higher aromatic content.
Riazi and Daubert (M. R. Riazi and T. E. Daubert, Ind. Eng. Chem. Proc. Des., Dev., 19, 289, 1980) showed that the Watson K factor is inadequate for the complete differentiation of molecular types, and developed a method to predict molecular composition of petroleum fractions using refractive index, Saybolt viscosity, and specific gravity. This method, which characterizes petroleum oils by molecular types rather than carbon content, is the standard given in the API Technical Data Book “Petroleum Refining,” Chapter 2. B.4, (Report No. API-1-80, Apr. 18, 1980). The addition of refractive index complements the other types of tests and helps to better differentiate aromatic, paraffinic, and naphthinic compounds.
For a process such as catalytic cracking, which involves the breaking of carbon-carbon and carbon-hydrogen bonds, characterization of oils by carbon and hydrogen content is more useful than by molecular types. Two common methods used for characterizing the oil in this manner are the n-d-M method (ASTM D3238-80) and a method known as the Total method published by H. Dhulesia (Oil and Gas Journal, 51-54, Jan. 13, 1986). Both of these methods use refractive index as a key correlating property. The data used to develop the n-d-M method were obtained from fractions of five crudes, boiling between 480 and 890° F. (see “Aspects of the Constitution of Mineral Oils,” K. van Nes and H. A. van Westen, Elsevier Publishing Co., 1951). The Total method used thirty-three different FCC feed stocks which included some residual oil blends.
Although the above described methods have the advantage of characterizing FCC feeds by carbon and hydrogen content, they experience the objectional feature of being applicable for material boiling at temperatures less than 1000° F.
Accordingly, it is an object of this invention to rapidly characterize potential heavy FCC feed stocks by carbon and hydrogen content.
It is a more specific object of this invention to analyze FCC feed quality for use in a model for computer simulation of an FCC reaction that predicts product yields.
It is a still more specific object to analyze FCC feeds in a simple and efficient manner, which can be routinely carried out in a refinery laboratory.
Still another objective of this invention is to develop a robust feed chemical analysis which is not dependent on feed source or pretreatment.
SUMMARY OF THE INVENTION
According to this invention, the foregoing and other objectives and advantages are achieved in a method for analyzing a mixture of heavy hydrocarbon oils to determine the aromatic carbon content, aromatic hydrogen content, and total hydrogen content of the oil. The method uses three mathematical model equations based on three bulk properties of the oil, and these properties have individual limiting values for infinitely long carbon/hydrogen groups in the liquid state. The petroleum oil properties are refractive index, specific gravity, and the Watson K factor, and the model equations include the respective limiting values.
In a preferred embodiment, the carbon and hydrogen content of oils with boiling points up to 1400° F. is determined from measurements including: refractive index, API gravity, and simulated distillation. The mathematical model equations, which include the limiting value associated with the property, are as follows:
C
a
=134.4679[RI−1.4750]−20.4858[K−12.5] EQ. (1)
H
a
=333.471[RI−1.4750]
2
−6.687[K−12.5] EQ. (2)
H=−20.77[Sp.Gr.−0.8510]+0.58[K−12.5]+14. EQ. (3)
where:
C
a
=wt. % aromatic carbon
H
a
=wt. % aromatic hydrogen
H=wt. % total hydrogen
K=Watson K factor, i.e.,[(VABP(F)+460)
⅓
]/Sp.Gr.
RI=refractive index at 68° F.
SpGr.=specific gravity, density of oil at 60° F. relative to water at 60° F., and
VABP
=
volume average of distillation curve boiling points at % off
=
[
10
%
+
30
%
+
50
%
+
70
%
+
90
%
]
/
5
The method of this invention using easily measured bulk properties to characterize the hydrocarbon chemistry of a broad spectrum of heavy hydrocarbon oils is advantageous for use in a refinery on a daily basis to aid in optimizing selection of oils for processing in an FCC unit.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein there is shown and described only the preferred embodiments of this invention.
REFERENCES:
patent: 5158670 (1992-10-01), Cody et al.
patent: 5712797 (1998-01-01), Descales et al.
patent: 5730859 (1998-03-01), Johnson et al.
patent: 5841678 (1998-11-01), Hasenberg et al.
patent: 6071402 (2000-05-01), Danot et al.
Ghonasgi Dhananjay B.
Meier Paul F.
Wardinsky Michael
Bogatie George E.
Phillips Petroleum Company
Pretlow Demetrius
Shah Kamini
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