Influence of Solvents, Filtering Oil Temperature and Incubation Period on Membrane Patch Color

Abstract

In recent years, varnish that is caused by oxidation products is a serious problem in thermal power generation. In our laboratory, we have developed diagnosis method for varnish by Membrane patch colorimetry. Membrane patch color is influenced by filtering condition such as solvent, filtering oil temperature and incubation period. Thus, it is important to understand the influence of solvent, filtering oil temperature and incubation period to diagnose varnish properly by using membrane patch colorimetry. In this study, we investigated the influence of solvents, filtering oil temperature and incubation period on membrane patch color. Furthermore, in-situ analysis by using microscopic FT-IR was conducted to investigate the behavior of oxidation products in heating and storing process. As a results, there was a tendency that membrane patch color increased with incubation period. Moreover, when sample oil and solvent were mixed and/or oil temperature is high, the membrane patch color showed a decreasing tendency. From the in-situ analysis by using microscopic FT-IR, in the case of heating process, the peak of 1710 cm^-1 , which is an absorption band of the carboxylic acid (-COOH), shifted to higher wave number. In the case of storing process, the peak of 1710 cm^-1 shifted to lower wave number. These results suggested that oxidation products become low-molecular due to hydrogen bond cleavage and soluble easily in turbine oil when oil temperature is high. On the other hand, the oxidation product become high-molecular by hydrogen bond formation and difficult to dissolve in turbine oil when sample oil is cooled and stored.