Executive Summary
Location
Kriel Power Station (South CW System, Unit 6)
Dosing Protocol
5ppm for 30 min/day
Key Result
Approx. 30% cleanliness-factor improvement within 3 days
1. The Challenge: Baseline Conditions
Prior to the intervention in May 2018, Unit 6 at Kriel Power Station was experiencing significant performance degradation due to condenser tube fouling. Baseline readings indicated poor heat transfer efficiency, severely impacting the unit's thermal performance.
- Initial TTD (Terminal Temperature Difference): Averaged 13°C against a design target of 1.7°C.
- Condenser Cleanliness Factor: Recorded at 29% at the start of the 12-17 May observation window.
- Backpressure: Deviating 2.08 kPa above target optimum levels.
2. The Protocol
A multi-disciplinary team comprising Chemical Services, Auxiliary, and Process Engineering initiated a trial using Mexel®432 on the South Cooling Water (CW) system. The product is a non-oxidizing, film-forming amine emulsion designed to detach biofilm and scale while establishing an anti-corrosion barrier at the molecular level.
Application: The chemical was dosed into the center well of the CW South system. The rate was set to 5 ppm of 100% concentration Mexel®432/0, injected for just 30 minutes daily.
Measurement Methodology: Performance was tracked using real-time DCS (Distributed Control Systems) data via ProcessBook, LIMS, and STEP reports. Condenser efficiency was analyzed using the 4-temperature methodology (Gibbard & Terranova) measuring TTD and backpressure deviation.
3. Measured Results
The intervention produced measurable changes in the monitored condenser indicators during the first 72 hours of dosage.
| Metric | Before / Early Observation | Reported Later Observation |
|---|---|---|
| Condenser Cleanliness Factor (12-17 May) | 29% | 69% |
| Terminal Temp. Diff (TTD) - West | 12.10°C | 6.01°C - 8.22°C |
| Actual TTD vs Target (1.7°C) | 13°C | 4.3°C |
| Backpressure Deviation | +2.08 kPa | +0.6 kPa |
Eskom RT&D Conclusion Summary
The report conclusion records approximately 30% improvement in condenser cleanliness factor within 3 days and notes improved TTD for Unit 6 based on condenser efficiency analysis.
— Official Report RTD/ACM/18/240-142764661
Microbiology Notes
The report includes two separate microbiology references. The Kriel South CW field table records approximately 80% reduction in microbiological count, but the report cautions that monthly microbiology results alone do not justify the chemical performance. The same section refers to a lab biocide comparison in which Mexel®432 reduced total aerobic bacteria by 93% and total anaerobic bacteria by 91%.
4. Derived Heat-Rate and Emissions Review
TTD, TR and backpressure data can support a heat-rate review when assessed against comparable load and ambient conditions. These indicators should be treated as engineering evidence rather than a universal savings claim.
The reported backpressure deviation change from 2.08 kPa to 0.6 kPa is relevant to derived heat-rate and emissions calculations, but any fuel or CO₂ figure requires a site-specific model and independent review before commercial use.
Validate this approach for your station
Our engineering team can review your current TTD and backpressure data to assess whether a structured baseline and monitored deployment is technically appropriate.