Condensing species from flue gas in Puertollano gasification power plant, Spain

Abstract

The occurrence and distribution of trace elements (Pb, Zn, As, Ge, Cd, Tl, Bi, Sn, and also Ni, Fe and V) in condensates arising from coal gasification was investigated through the study of samples physically deposited on the gas cooling system from the Puertollano IGCC 335 MW power plant. These highly metal enriched samples are suitable for a comprehensive evaluation of the mode of occurrence of these elements in IGCC fly ash. Pb, Zn, Ge, and Fe sulfides, Ni–Fe arsenides, Ge and V oxides as well as traces of K chloride and Pb, Zn and Fe sulfates were determined as the major bearing phases for these elements. Three condensation zones were differentiated as function of the condensation temperatures and metal content: 1. Pb zone (520–750 °C), characterized by the dominance of galena (70–90% of the main crystalline phases), and by the condensation of pyrrhotite and nickeline. 2. Ge–Zn–Pb zone (520–470 °C), with sphalerite and wurzite being the dominant crystalline phases (over 40%), and Ge compounds, GeS 2 and GeO 2, reaching 30% of the bulk condensates. 3. Zn zone (300–400 °C), characterized by the dominance of Zn sulfides (over 85% of the main crystalline phases). The results obtained from these highly metalliferous condensates show similar forms of occurrence for the studied elements to those obtained in the bulk Puertollano IGCC fly ash (by using XAFS spectroscopy), where the contents of these elements are much lower. Furthermore, the sequential condensation of sulfides during coal gasification is similar to that from volcanic fumaroles, and may thus promote a better understanding of volcanic deposits.