Determination of Ferrous Ion Content of Heat Exchanger Wash Solutions

Significance of the Topic

Precise measurement of ferrous ions in heat exchanger wash solutions is essential to assess the performance of acid inhibitors and prevent corrosion. This method supports quality control in chemical processing and refinery operations by delivering reliable data on metal ion concentrations.

Aims and Overview of the Study

This application note outlines a thermometric titration approach to quantify Fe2+ levels in acid wash solutions used in heat exchanger maintenance. The goal is to establish a reproducible procedure for routine analysis with detection limits between 20 and 100 mg/kg depending on sample matrix.

Methodology and Instrumentation

• Principle: Oxidation of Fe2+ by dichromate in acidic medium, monitored via temperature change at the exothermic endpoint.
• Reagents: Standard 0.1N K2Cr2O7, 10% w/v H2SO4.
• Experimental Parameters:
  • Data acquisition rate: 10 readings/s
  • Titrant delivery: 1 mL/min
  • Data smoothing factor: 35
  • Sample aliquot: 20–50 mL depending on viscosity
• Instrumentation: Thermometric titrator equipped with a precision temperature probe to detect inflection at endpoint.

Main Results and Discussion

Analysis of alumina refinery acid wash solutions demonstrated Fe2+ concentrations ranging from approximately 107 to 356 mg/kg. Replicate determinations showed good precision (<5% RSD). The method effectively handled high silicic acid content by adjusting dilution and aliquot size.

Benefits and Practical Applications of the Method

• Rapid endpoint detection with minimal operator interpretation.
• Suitable for turbid or viscous samples without optical limitations.
• Wide usable concentration range aligns with industrial QC requirements.

Future Trends and Potential Applications

Advances may include inline automation for continuous monitoring, expansion to other metal ions using tailored redox titrants, and enhanced sensor technology to lower detection thresholds and improve robustness in complex matrices.

Conclusion

Thermometric titration with potassium dichromate provides a reliable, efficient approach for quantifying ferrous ions in acid wash solutions, facilitating improved corrosion control and process quality assurance in industrial settings.