ENEXIO Water Technologies GmbH

CO2 Reduction by Cooling Tower Retrofit Measures

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Abstract: In the course of a cooling tower retrofit a cold-end-optimisation should be done. Due to installing best available technology of cooling fills a decrease of cooling water temperature and additional power output can be generated. The following consideration shows options of improvement and takes a look at the economic importance.

Introduction
Increase in efficiency of steam power plants is an ongoing demand, relevant for all components of the thermodynamic cycle. The cooling tower is a significant part for the condensation pressure and therefore has an important influence on the efficiency of the low pressure turbine. Most of the cooling towers are designed as evaporative heat rejection devices, implying an environmental interface by transferring condensation heat to atmosphere. Even a good water treatment and water quality does not guarantee the entire prevention of scaling and biological fouling effects on cooling fills, the core of the heat exchanging and mass transferring surface. Hence the thermal performance will be reduced anyway during a 20 to 30 year operating period. The amount of reduction depends e.g. on air pollutant, make-up water condition and water treatment facilities. A reduced thermal performance entails an increase of cooling water temperature and condensation pressure causing a negative effect on power plant efficiency and it´s CO2 emission.

Over the last two decades cooling fills made of fibre and asbestos cement have been mostly replaced by plastic film and splash type fills. Changes of moulds and materials into PP and PVC have raised the heat and mass transfer significantly. Hence power plant companies are able to improve thermal performance of out of date cooling towers, even beyond the original design. In this way a regular refurbishment of a cooling tower creates additional benefit of power generation.

Retrofit of cooling towers is limited by constructional and financial boundary conditions. Mostly the pumping head and structural dimensions are fixed, by contrast other influencing variables like cooling fill height are often mutable within some limits. Recalculations of thermal performance demand a close cooperation between power plant and cooling tower companies, in order to define optimized options. With optional thermal cooling tower calculations a power plant operator should be able to evaluate the best available technology with regard to economic aspects. This approach will be shown by means of a thermal and economic analysis of a typical, in the eighties erected, natural draught cooling tower.

Keywords: Cold-End-Optimisation, Cooling Tower Retrofit, Increase of Plant Efficiency.

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