Corrosion Inhibitor Study

Section 0. Summary

Ondeo-Nalco Chemicals is supplying JGSPC Utilities and Tank Farm and Westpoint Power Plant for their water treatment program for about two years. UTF employs Nalco 8325 and Nalco 7330 for its closed loop cooling water treatment. This is a nitrite- based treatment supplemented with microbiocide to control the growth of microorganisms that may eventually lead to system's failure. Westpoint, on the other hand, uses Nalco 39LSN for the cooling water treatment of the diesel engine and Nalco 1700, 1800, 7205 and 7208 for its boiler and steam generator. Currently, UTF budgets Php 1M for their annual consumption of Nalco 8325 and Westpoint approximates to Php 300,000 per annum.

The unsteady amount of consumption of both systems and the overdosage of chemicals in the powerplant, plus the fluctuation of chemical prices (due to exchange rate) have triggered the evaluation of the current water treatment program of JGSPC and new water treatment program proposal of another supplier.

This comparative study of the two water treatment program proposals aims to develop recommendations for the improvement of the current system. This takes into account the reliability and effectivity of water treatment programs based on the technical feasibility (chemical composition and application), financial feasibility (cost of the program and economics), customer services (technical services offered, chemicals delivery and availability) and, human health and environmental impact (toxicity of chemicals and waste disposal).

Based on the chemical composition and application, Nalco and Drew chemicals are comparable. However, the following were found to be significant differences:

1. Mekor 70 is a volatile oxygen scavenger and removes more oxygen than Nalco 1700 which is nonvolatile. Mekor 70 can provide O2 scavenging before and after the boiler while Nalco 1700 is limited to condensate side only.

2. Nalco provides a blend of three amines for carbonic acid neutralization more on the steam side while Drew suggests a blend of two amines for neutralizing carbonic acid in both condensate and steam sides. The pH of condensate must be maintained from 8.5 to 9.0 for Nalco and from 7.5 to 8.5 for Drew.

3. Nalco uses the coordinated phosphate program while Drew employs the congruent phosphate program in boiler water treatment. Drew offers a single shot of Drewphos 2600 for minimization of scale deposits and dispersion of particulate and iron. Nalco uses 7208 for the control of scale deposits and Nalco 7205 for the dispersion of particulate and iron as well as ammonia minimization in case of degradation of amines.

4. Nalco uses nitrite- based (Nalco 39LSN) treatment supplemented with microbiocide (Nalco 7330) for cooling water treatment for diesel engine. Drew proposes a nitrate-nitrite treatment by Drewgard 4109 with silica to aid in