Double Filter Concentration Method as a Pretreatment for the Determination of Iron in Ultra-supercritical Pressure Boiler Feedwater

We developed a concentration method using a double filter as a pre-treatment. We call it the "Double filter concentration method". It is a pre-treatment method for the determination of traces of iron by 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ) absorption photometry. It is important to monitor iron concentration in an ultra-supercritical pressure boiler applying an oxygen treatment method as a water treatment. Because the iron in feedwater forms a hematite, it is necessary to control the iron concentration in the feedwater at less than 2 mu g L-1 so as to prevent problems. Therefore, a quick and effective analysis method is necessary on site. The double filter is constructed in the membrane filter and chelate filter having iminodiacetic acid groups. Iron particles are trapped by the membrane filter, and the dissolved iron are trapped by the chelate filter. When we applied this developed method, we were able to measure the low range iron concentrations. This method is suitable for on-site analysis because it can also shorten the analysis time.