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Language: English

Conflict of Interest: In relation to this article, we declare that there is no conflict of interest.

Publication history: Received July 15, 2016
Accepted December 23, 2016

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Phase diagram of CaSO4 reductive decomposition by H2 and CO

Min Zheng^{1 2†} Yanbing Xing³ Simei Zhong² Hua Wang^{1 2}

¹State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kun Ming 650093, China ²Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China ³Faculty of Material Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China

zhengmin1634@163.com

Korean Journal of Chemical Engineering, April 2017, 34(4), 1266-1272(7)
https://doi.org/10.1007/s11814-016-0360-7

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Abstract

The CaSO4 reductive decomposition is an interesting issue in both the reduction zone of fluidized bed combustors (FBCs) for coal combustion and the fuel reactor of chemical-looping combustion (CLC) system. Under CO or H2 atmosphere, CaSO4 is reduced to CaS and CaO, together with the releases of gas sulfides, which causes environmental pollutions. To lessen sulfur release, it is important to figure out the chemical stability of CaSO4 reductive decomposition. Thus, the chemical stability of CaSO4/CaS/CaO under CO or H2 atmosphere was studied in consideration of SO2, COS and H2S emissions. The results show that regions I (VI), II (V), and III (IV) are the stability fields of CaSO4, CaS and CaO, respectively. The range for CaO stability is increasing with reaction temperature and partial pressures of CO2 and H2O. Within the reaction temperature range of 800 and 1,000 °C, when the CaSO4-CO-H2 reaction system reaches the triple equilibrium point, the main gas sulfur released is SO2, followed by H2S, while COS generation is much smaller. In a real reaction system, when the values of real PH2/PH2O (PCO/PCO2), PSO2, PH2S (PCOS), PH2O (PCO2) and T fall into Region I (IV), or II (V), the final product should be CaSO4 or CaS, and the sulfur release from CaSO4 reduction can be controlled.

Keywords

CaSO4 Reductive Decomposition Phase Diagram SO2 Emission H2S Emission COS Emission

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