Refinery Feedstock Corrosivity Characterization via Electrochemical Impedance
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Solution Overview
Problem
Current methods for characterizing the corrosivity of crude oils and refinery feedstocks are inadequate, as they rely on traditional approaches like Total Acid Number (TAN) and do not effectively account for the complex corrosive properties of naphthenic acids and sulfur compounds, leading to inefficiencies in blending and corrosion management.
Innovation Solution
The method involves using electrochemical impedance spectroscopy (EIS), linear and cyclic voltammetry, vibrational spectroscopic analysis, and electrical resistivity measurements to evaluate the corrosivity of crude oils by analyzing the dissociation and association of acids and sulfur compounds as a function of temperature, allowing for the optimization of blends to minimize corrosion impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Total Acid Number (TAN) methods are used to characterize corrosivity, then the evaluation process is simple and quick, but the measurement precision and accuracy of corrosivity characterization is insufficient
Solution Approach 1:
The patent transforms the corrosivity evaluation from a single parameter (TAN) to multiple parameters including electrochemical impedance spectrum, capacitance values at different frequencies, and resistance measurements. This multi-parameter approach significantly improves measurement precision while the automated measurement system keeps operational complexity manageable
Solution Approach 2:
The patent introduces electrochemical impedance spectroscopy as an intermediary measurement technique that indirectly characterizes corrosivity through electrical properties. This intermediary approach provides more accurate corrosion information than direct chemical analysis while avoiding the complexity of sophisticated spectroscopic equipment
2Reliability
If blending is performed based on predetermined TAN numbers, then the blending process is straightforward, but the reliability of achieving desired corrosivity levels is insufficient
Solution Approach 1:
The patent implements feedback control by measuring the electrochemical impedance spectrum of the blended feedstock and comparing it against target values. The system automatically adjusts blend ratios to achieve desired corrosivity levels, ensuring reliable control while the automated feedback loop simplifies the operational process
Solution Approach 2:
The patent performs preliminary electrochemical characterization of individual crude oils before blending to predict blend corrosivity. This preliminary action allows operators to pre-calculate optimal blend ratios that will achieve target corrosivity levels, making the actual blending operation straightforward and reliable
3Measurement precision
If advanced electrochemical methods (EIS, voltammetry) are used to characterize corrosivity, then the measurement precision and characterization accuracy are improved, but the device complexity and measurement time increase
Solution Approach 1:
The patent applies partial action by measuring electrochemical impedance at selectively chosen frequencies rather than performing complete spectrum analysis across all frequencies. This approach captures the essential corrosivity information while reducing measurement time significantly compared to full spectral analysis
Solution Approach 2:
The patent performs preliminary screening measurements using simplified electrochemical tests to identify feedstocks requiring detailed analysis. This preliminary action filters out samples that don't need extensive characterization, reducing overall measurement time while maintaining precision for critical samples
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more accurate characterization of corrosivity, enabling the optimization of crude oil blends to achieve desired corrosivity levels, thereby reducing equipment corrosion and improving refinery operations.
Implementation Method 1
performing impedance measurements on the crude oil as a function of temperature to obtain a first electrochemical impedance (EI) spectrum
Implementation Method 2
oxidation/reduction of corrosive species such as acids occurs, allowing the use of voltammetry to characterize the feedstock with respect to is its corrosion property
Data Source
AI summary
A method for characterizing refinery feedstocks according to their corrosivity is provided. The characterization is based on any of: dissociation of acids in the crude, breakup of naphthenic acid molecular associations, and/or dissociation of sulfur compounds in the feedstocks. In one embodiment, the characterization is done via vibrational spectroscopic measurements over a range of temperature, e.g., from ambient to 700° F. The method can be practiced in any of refinery, terminal, and laboratories. It can be used in conjunction with models and hardware to optimize the usage of refinery feedstocks in the blending and valuation of the feedstocks.