Electrochemical Impedance Spectroscopy for Crude Oil Corrosivity
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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 reliability of corrosivity assessment is insufficient
Solution Approach 1:
The patent segments the corrosivity characterization into multiple independent measurement components: electrochemical impedance spectroscopy (EIS) for measuring resistance and capacitance at different frequencies, voltammetry for detecting oxidation/reduction of corrosive species, and temperature-dependent analysis. Each segment targets specific corrosive properties (naphthenic acids, sulfur compounds) rather than using a single blanket method, thereby improving measurement precision without requiring a completely complex integrated system.
Solution Approach 2:
The patent introduces electrochemical measurements as intermediary indicators that indirectly reflect corrosivity. Instead of directly measuring corrosion damage (which would require complex long-term exposure systems), the method uses EIS and voltammetry to detect electrochemical properties (impedance, current-voltage relationships) that serve as proxies for corrosive potential, simplifying the overall characterization system while improving accuracy.
2Reliability
If blending is performed based on predetermined TAN thresholds, then the blending process is straightforward and fast, but the reliability of corrosion protection is insufficient for complex feedstocks
Solution Approach 1:
The patent performs preliminary electrochemical characterization of each feedstock component before blending. By measuring EIS spectra, voltammetric curves, and temperature-dependent properties in advance, the system establishes baseline corrosivity data for each stream. This preliminary action enables more reliable blend formulation while maintaining efficiency, as the actual blending operation simply needs to combine pre-characterized streams according to calculated ratios rather than performing complex real-time analysis during blending.
Solution Approach 2:
The patent changes the characterization parameters from simple TAN values to multi-parameter electrochemical profiles including impedance magnitude, phase angle, capacitance, and voltammetric peak currents. By analyzing how these parameters change with temperature and frequency, the system captures the complex behavior of naphthenic acids and sulfur compounds, enabling more reliable corrosion prediction for blended feedstocks while the computational blending process remains efficient.
3Measurement precision
If comprehensive electrochemical analysis is performed to accurately assess corrosivity, then the characterization precision improves, but the time required for analysis increases
Solution Approach 1:
The patent employs periodic scanning in voltammetry (cyclic voltammetry with forward and reverse scans) and frequency sweeping in EIS (measuring impedance at multiple frequencies from low to high). These periodic measurements efficiently capture the electrochemical behavior of corrosive species at different states, providing comprehensive characterization data within a standardized time framework that balances precision with operational efficiency.
Solution Approach 2:
The patent performs measurements at more data points than the absolute minimum (excessive action) - using multiple frequencies in EIS, multiple scan rates in voltammetry, and temperature steps throughout the operating range. This excessive sampling ensures that no critical corrosive species behavior is missed, achieving high measurement precision. The time cost is managed by automating the measurement sequence and using computational methods to extract key parameters from the abundant data.
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 creation of optimized blends that reduce corrosion risks and improve refinery operations by correlating molecular associations and dissociations with corrosion performance, thereby enhancing the management of corrosive properties in crude oils.
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
current passing through the feedstock is measured as a function of the applied DC voltage. As increasing/decreasing voltage is applied at a constant rate with time, oxidation/reduction of corrosive species such as acids occurs
Implementation Method 3
analyzing the first EI data relative to the second EI data to evaluate the corrosivity of the crude oil feedstock, wherein comparing the first EI data with the second EI data includes comparing at least one of a resistance measurement and a capacitance measurement
Data Source
AI summary
Refinery feedstocks can be characterized 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. The characterization is performed as a function of temperature via any of electrical resistivity measurement, vibrational spectroscopic analysis, voltammetry, electrochemical impedance spectroscopy (EIS) and combinations thereof. 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. In one embodiment, the characterization of refinery feedstocks is via the use of EIS.