Backwash filtration system for condensate polishing in power plant

S. Strasser*; L.-M. Ertl; J. Woegerer, Lenzing Technik GmbH, Austria

The requirements on efficiency, environmental protection and operational reliability in power plants are increasing constantly. These growing standards oblige providers to analyze and optimize their processes throughout their running operation.

A european steel mill produces the energy supply for production in an own power plant, operating a steam turbine. A trouble-free operation can only be secured, when all process aggregates are prevented from abrasion- or corrosion products. The boiler feeding the steam turbine in the present case is fueled with furnace and coke oven gas. After the steam turbine, the steam condensates and is re-circulated in the feed tank of the boiler. Over time, this closed circuit is contaminated with solids from turbine abrasion or corrosion of steam-perfused plant components. In order to eliminate the hard and dissolved impurities (salts), the water needs to be filtered and desalted in a bypass stream. This is traditionally done by a manually backwashable candle filter and an ion exchanger.

Due to the high manual handling efforts (manual backwash of the candle filter), the operator was in search for an automatic filtration alternative to the candle filter. Furthermore, the discontinuous mode of operation intensified the search for a reliable, continuous filtration system, as the traditional condensate treatment required the installation of a redundancy candle filter. After evaluation of various technologies, the automatic backwash filter Lenzing OptiFil® was chosen as substitution on trial.

Particulate impurities like abrasion of pumps, turbines or pipework would prevent the ion exchanger from desalting the boiler feed water. In order to protect the downstream ion exchanger and secure trouble-free operation of the steam turbine, the condensate has to be filtered at a fineness of 5µm prior to entering the mixed bed ion exchanger. The aim of the trials was an exchange of the currently installed manually backwashed candle filter. In the present case, the operability of the automatic backwash filter Lenzing OptiFil® was evaluated in a long-term (2 year) trial period. In case of favorable test results, it should be installed as substitution for the conventional candle filter....

Session: L1 - Backwashing Filtration
Day: 13 March 2018
Time: 13:00 - 14:15 h

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