Case Study - EDF Le Havre Fossil Plant

Challenge:

This coal-fired power plant along France’s Le Havre harbor was experiencing significant efficiency loss due to fouling in the cooling water circuit. In particular, the plant suffered from serious macrofouling due to mussel growth in the water structures and condenser water boxes. Le Havre furthermore experienced fouling as a result of sedimentation, corrosion and scaling. These problems were unsuccessfully controlled with conventional chlorine and other water treatments. The overall costs and poor performance led the plant to search for alternatives leading them to Mexel 432/0.

Treatment:

Mexel 432/0 was initially tested at LeHavre a decade prior and adopted throughout the whole plant in order to effectively treat an array of fouling and operational problems. The three units under treatment reached a total capacity of 1450 MW and used 53 m3/sec of cooling water at full load. The water circuit inlets were fitted with diffusers allowing full treatment of Mexel 432/0 on all surfaces. The standard treatment levels were 5 ppm for 30 minutes per day with dosing controlled by a fully automated process.

Laboratory studies were conducted to determine the benefits of Mexel 432/0 in inhibiting corrosion of metals found in the condenser and other water circuit equipment. The results showed that under thermal and other typical plant operating conditions, Mexel 432/0 reduced the annual corrosion rate from 283 μm per year to an average of 58 μm per year when an initial coating was followed by a continuous treatment of 2.5ppm. Mexel 432/0 improved a passive coating formation and cleaned the surfaces thereby improving the thermal exchange capacity.

Results:

Mexel 432/0 was highly successful in fouling prevention within Le Havre’s entire cooling water circuit. The frequent water box cleanings that caused reduced power production during the summer season were eradicated due to Mexel 432/0 near elimination of macrofouling. After implementing the Mexel 432/0 process (demonstrated in the pictures below) the improved cleanliness level in the interior cement tunnel surfaces, metal water boxes and condenser tubes was maintained.

Before Mexel 432/0 process

      After Mexel 432/0 process  

Estimates showed that the average annual operating costs for water treatment were reduced by about 35% when using Mexel 423/0 compared to electro-chlorination. In addition, average annual improvement in efficiency and availability of electric generation was estimated to exceed 1.5% therefore reducing the coal costs per unit of electricity. The reduction in CO2 emissions per unit of production also served to lower operating costs of the plant. These additional financial benefits were attributed to Mexel 432/0 extending the life of equipment that is susceptible to corrosion and the simplified operations and maintenance. The Le Havre plant continues to be an extremely satisfied Mexel 432/0 customer. When asked to identify the most beneficial aspect of the Mexel 432/0 process, the plant operator commented “It’s so simple!” further explaining that the automated process has continually been trouble-free and requires little attention and, therefore, maintenance labor.