标题：Thermodynamic prediction of the effect of repeated recirculation of cooled flue gases on the content of major, minor, and trace compounds in oxy-coal combustion products
期刊名称：Bulletin of the Institute of Heat Engineering
印刷版ISSN：2083-4187
出版年度：2020
卷号：100
期号：2
页码：102-114
出版社：Warsaw University of Technology
摘要：This study investigates changes in the composition of oxy-coal combustion products resulting from the recirculation of cooled flue gas (FGR) at 20, 60, 100, 200, and 300 oC^{\ o}C o C (containing 70–95 mol% CO 2 ). It presents the results of thermodynamic calculations describing changes in the content of the major, minor, and trace components of flue gases, ash and condensate. The results reflect a scenario of starting the oxy-coal combustion system in a fluidized bed boiler using low-purity oxygen from an air separation unit. This work demonstrates that in FGR loop the major species, i.e., Ar and N 2 , as well as the minor, e.g., Cl 2 , PbCl 4 , HgCl 2 , and CrOCl 3 , are accumulated. After nine FGR loops cooled to 300 oC^{\ o}C o C , marked increases in concentrations were observed: ZnCl 2 and HCl (3-fold), as well as CrO 2 (OH) 2 (2.5-fold). The ash that was formed contained, among others, CaSO 4 , SiO 2 , CaMgSi 2 O 6 , MgSiO 3 , ZnFe 2 O 4 , and MgCr 2 O 4 , whose mass changed in successive reactors as a result of the repeated FGR. Depending on the temperature of the cooling reactor, flue gases were subjected to recirculation and the main component of the condensate was H 2 O or H 2 SO 4 · 6H 2 O. The condensate contained chloride salts, e.g., PbCl 2 , KCl, and ZnCl 2 , as well as sulfate salts, i.e., K 2 SO 4 and Na 2 SO 4 , in smaller amounts. A consequence of the nine-fold FGR cooled to T≤200 oCT\le200\ ^oC T ≤ 2 0 0 o C was, among others, a percentage mass increase in ZnCl 2 in the condensate. The less cooling applied to flue gases, the more likely the occurrence of sulfates was in the condensate.
