Ferric Substance Formed in Circulateing Water for Boiler and Steam Piping Used for High Temperature Steam Supply Systems in City

Abstract

Boilers are used to generate steam in many fields such as building and thermal power generation. Products from water evaporation adhere to boilers and their piping as scale or precipitate as sludge, obstructing the flow of steam to lower the thermal efficiency of steam. The detailed data on ferric substance in compositions of such scale and sludge are not well known yet. The author have reported about detailed results of studies emphasizing ferric substance in boilers and their piping used for heating building with steam of 100°C. To clarify the compositions of such substance, we have studied boilers that supply high temperature steam of 180°C to high-rise buildings, mainly investigating the ferric substance in boilers and piping. What has attracted our attention in the study is the fact that ferromagnetic magnetite (Fe₃O₄) and weakmagnetic hematite (α-Fe₂O₃) accounted for about 98% of the substances. The average grain sizes of magnetite and hematite were about 105 nm and 160 nm respectively, being larger than those of the heating boilers due to the higher steam temperature. The saturation magnetization was about 79 emu/g, and 82 emu/g when corrected for nonmagnetic layer, being close to the bulk magnetite.