Minimal Corrosion Thanks to pH Control with ISM pH Measurement

The installation of an intelligent in-line pH measurement with automated electrode cleaning allows for accurate control of sour water pH in Crude Unit Overhead Condenser Boot Water.

Sour water corrosion
Processing of sour crudes often results in serious corrosion problems in the top part of the crude column and condenser tubing. Due to the injection of steam in the column large amounts of water are generated. The crude itself contains contaminants such as sulfur, salts and gases. Dissolved in the produced water, these form a highly corrosive solution normally referred to as sour water. Since the rate of corrosion is largely depending on pH of the sour water, reliable treating and neutralizing is required.

An unsatisfactory situation
In the past our customer used standard pH measuring systems to control the chemical treatment of sour water. Large quantities of hydrocarbons, also present in the process, continuously affected the pH electrode and lowered its performance to such an extent that the customer decided to discard the measurement and turn to testing in the laboratory.

EasyClean solution
Since in-line pH measurement however is still favorable, Mettler-Toledo offered an innovative solution which enables reliable pH measurement and control over long periods of time with minimal maintenance requirements. First of all, the electrode chosen for this application is designed to operate in environments with hydrocarbons and organic solvents. Furthermore, an EasyClean 400 system was installed to automatically clean and calibrate the electrode. Now even extreme amounts of hydrocarbons and sulfides are simply washed away periodically and continuous availability of the measurement is maintained.

The following instruments were installed:

• InPro 4260 i ISM pH electrode;
• M 700 transmitter;
• EasyClean 400 Cleaning and calibration system;
• InTrac 777 retractable housing.

ISM
The unique diagnostics in the ISM electrode enable our customer to predict the little maintenance that is still left to do. Whenever an electrode is approaching the end of its useful life it automatically informs the analyzer engineer, who in turn can replace the electrode with a pre-calibrated one before the measurement actually starts failing. To make things even easier, no configuration is required as the electrode itself takes care of that part also!

Reasons for product selection

• InPro 4260 i ISM
  The InPro 4260 i ISM electrode is best suitable for this application due to its resistance to the high concentration of sulfur and hydrocarbons. As the pH electrode has ISM technology, it is possible for the user to do a much easier maintenance by using pre-calibrated sensors and on-line diagnostics. ISM surpassed customer’s expectations and surely differentiated METTLER TOLEDO’s sensors from other suppliers’.

• Retractable housing
  The retractable housing was chosen for automated cleaning purposes.

• M 700 transmitter
  The M700 is used for both pH and control of the EasyClean 400 unit.

Customer testimonial
Due to high sulfur concentration, InPro 4260iISM was chosen and it has been presenting a step ahead in the customer’s expectations regarding product performance. Additionally, the ISM concept is making the maintenance programming easier as well as the customer’s inventory control.

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