Corrosion Control and Decreased Operational Costs with Memosens for Desalter pH
The first step in the refining process is the desalter, part of the Crude Distillation Unit (CDU). The desalter separates brine water from the crude oil entering the distillation unit of the refinery. The process heats the crude to about 300°F. Added chemicals and clean water force out the brine. As the crude oil exits the desalter, it still has leftover salts and water that were not completely removed. The desalter outlet runs into the vacuum or atmospheric crude towers, where they process it into lighter hydrocarbons.
Desalter pH measurements at strategic locations around the desalter increase its efficiency and reduce the potential for corrosion in downstream distillation process units. Monitoring the pH in the desalter can indicate the presence of contaminants in the crude oil. Finally, high pH in the desalter can create an emulsion layer, which impacts desalter efficiency.
The Solution
The applications in and around the desalter process are difficult due to oily buildup. Solids and sulfides can plug the pH sensor junction and attack the reference system. The SE571 pH sensor design provides high resistance to buildup due to a PTFE annular ring junction. Additionally, a salt reservoir protects against leaching and the patented Silamid reference slows poisoning of the reference system.
A microprocessor in the head of the pH electrode allows for offline calibration and diagnostics when using a Portavo portable meter. The Portavo allows technicians to do all the work of calibration and troubleshooting in the shop or lab instead of in the process unit. This removes the possibility of exposure to temperature extremes and weather changes that can damage calibration buffers. Therefore, a technician can simply carry the calibrated sensor to the transmitter, disconnect the cable, and do a “hot-swap” with no additional calibration or configuration.
The Stratos Pro is an FM-approved, loop-powered transmitter that provides HART process and diagnostic information. The transmitter can send this information to the DCS. Operators can view the information within AMS software. As a result, this provides predictive maintenance capability reducing the potential for unscheduled process interruptions. Technicians can install a newly calibrated Memosens pH probe in a matter of minutes, resulting in almost no interruption to the measurement.
The CSR 3600 B, a simple ball-valve retractable holder, allows the user to insert or remove the sensor in a double block and bleed installation. The holder design meets refinery API specifications.
What was this Customer’s Return on Investment?
Reduced operational cost: Reliable desalter pH monitoring helps reduce chemical usage by eliminating overdosing for brine removal.
Improved corrosion control in the CDU: Desalter pH monitoring can reduce corrosion of downstream piping and vessels.
Decreased sensor replacement: The SE571’s Teflon diaphragm and patented reference system provide extended life in oily and contaminated processes.
