Naphthenic Acid Corrosion Joint Industry Project ? Phase 3 - 2017 - 2020
Naphthenic acids corrosion represents an important challenge for oil refining industry when low quality crude oils are processed. The corrosivity of low quality crudes is caused mainly by their natural naphthenic acids (NAP) and sulfur content which becomes particularly problematic at high temperature and high velocity conditions, typical for distilling towers, furnaces and transfer lines, causing important material losses during processing. Understanding and reducing the corrosive effects of NAP became the main focus for numerous research studies over the past decade, done both in the oil and gas industry and in the academia as well.
The Institute for Corrosion and Multiphase Technology (ICMT) at Ohio University started in 2004 a research program sponsored by a major oil and gas company focusing on naphthenic acid and sulfur corrosion and on factors like high temperature and flow that influence this corrosive processes. The project continued for six years (it ended in 2010) and investigated the complex relationships between NAP and sulfur containing compounds in oil fractions using different experimental apparatus and analytical instruments. Based on the knowledge accumulated in six years of experimental and analytical work, the ICMT decided to continue this research project as a Joint Industry Project (NAP JIP) opened to any company interested in
downstream corrosion. NAP JIP started in 2011 and was supported financially by oil and gas companies or companies related to oil industry. NAP JIP has already completed two consecutive 3-year phases (I & II) and started its third phase - NAP JIP 3 - which will end in 2020.
NAP JIP 3 Objectives
NAP JIP Phases (1&2) generated extensive experimental data and scientific insights into the mechanism of NAP and sulfur corrosion. That data and knowledge was incorporated in a corrosion model that was delivered at the end of NAP JIP 2. That model takes into account the combined corrosive chemistry of NAP acids and sulfur under the influence of the high temperature as determined in the laboratory. It also incorporates mass transfer components related to flow (oil velocity, pipe geometry) – conditions typical for distilling towers and side streams. Thus the model predicts the metal loss (corrosion rate) for different periods of time (hours, days, months). NAP JIP 3 is proposing additional experimental and analytical work that is designed to acquire key data for developing a more accurate and robust version of the ICMT/OU corrosion model. Therefore the objectives of the new project phase are:
- Define more accurately key acid and sulfur kinetic parameters (activation energies and kinetic factors) from specific experimental data and use them to improve prediction accuracy.
- Determine the role of acid on scale dissolution (FeS, magnetite, and possibly FeCr spinels) - experiments focusing on scale formation/dissolution processes.
- Evaluate experimentally the effect on scales of changing the corrosive species in sequence or order (changing feeds in distilling towers).
- Incorporate all new experimental results in the new version of ICMT/OU corrosion model - the main deliverable of the project.
The experimental work of NAP JIP 3 is executed at the ICMT on different experimental units specialized for studying NAP acid corrosion under experimental conditions designed to be as close to refinery operating conditions as practical. This equipment is capable of specialized experiments at high temperature under either static conditions - stirred autoclaves or continuous flow conditions in single-phase flow or two-phase flow loops. The analytical work is performed also in our the institute using the Scanning Electron Microscope (JEOL JSM-6390) coupled with an Energy Dispersive X-ray Spectrometer (SEM/EDS), the InfiniteFocus Profilometer Microscope (IFM), or the Atomic Force Microscope (AFM). For chemical analysis of gaseous compounds NAP JIP 2 uses a Micro-GC (Varian 490-GC PRO Micro-GC) and for TAN evaluations according to ASTM D664 the project uses a Micro TAN Titrator (Aquamax Micro TAN).