Removal of iron oxide scale from feed-water in thermal power plant using superconducting magnetic separation

Abstract

The superconducting magnetic separation system has been developing to separate the iron oxide scale from the feed water of the thermal power plant. The accumulation in the boiler lowers the heat exchange rate or in the worst case damages it. For this reason, in order to prevent scale generation, controlling pH and redox potential is employed. However, these methods are not sufficient and then the chemical cleaning is performed regularly. A superconducting magnetic separation system is investigated for removing iron oxide scale in a feed water system. Water supply conditions of the thermal power plant are as follows, flow rate 400 t / h, flow speed 0.2 m / s, pressure 2 MPa, temperature $160-200^{\circ}C$, amount of scale generation 50 - 120 t / 2 years. The main iron oxide scale is magnetite (ferromagnetic substance) and its particle size is several tens ${\mu}m$. As the first step we are considering to introduce the system to the chemical cleaning process of the thermal power plant instead of the thermal power plant itself. The current status of development will be reported.

Fig. 1. Feed-water system and location of separator.

Fig. 2. Flow speed dependency of Separation efficiency of membrane filter and high gradient superconducting magnet separation.

Fig. 3. Chemical cleaning line.

Fig. 4. Superconducting magnet used in this work and magnetic field density distribution.

Fig. 5. Magnetic filter stack before (a) and after (b) experiment.

TABLE I CHARACTERISTICS OF SCALE FROM DIFFERENT TEMPERATURE.

TABLE II CONDITIONS OF CHEMICAL CLEANING LINE AND HIGH PRESSURE FEED WATER HEATED DRAIN.