Development of calcium coke for CaC 2 production using calcium carbide slag and coking coal
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Development of calcium coke for CaC2 production using calcium carbide slag and coking coal Xu-zhong Gong 1,2,3), Jun-qiang Zhang 1), Zhi Wang 1,3), Dong Wang 1,3), Jun-hao Liu 1,3), Xiao-dong Jing 1,3), Guo-yu Qian 1,3), and Chuan Wang 4) 1) Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China 2) Chemical Engineering School, University of Chinese Academy of Sciences, Beijing 100049, China 3) Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China 4) Department of Process Metallurgy, Swerim AB, Lulea 97125, Sweden (Received: 13 January 2020; revised: 21 March 2020; accepted: 24 March 2020)
Abstract: A type of calcium coke was developed for use in the oxy-thermal process of calcium carbide production. The calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag, which is a solid waste generated from the chlor-alkali industry. The characteristics of the calcium cokes under different conditions were analyzed experimentally and theoretically. The results show that the thermal strength of calcium coke increased with the increase in the coking coal proportion, and the waterproof property of calcium coke also increased with increased carbonation time. The calcium coke can increase the contact area of calcium and carbon in the calcium carbide production process. Furthermore, the pore structure of the calcium coke can enhance the diffusion of gas inside the furnace, thus improving the efficiency of the oxy-thermal technology. Keywords: calcium carbide slag; calcium carbide production; calcium coke; thermal strength; waterproof property
1. Introduction Electro-thermal CaC2 production is characterized by poor kinetic conditions because of the limited contact area between the bulk char and CaO, leading to a higher reaction temperature (~2200°C) [1–2]. As a result, the total energy consumption in electro-thermal CaC2 production is high. The oxy-thermal method involves directly using the heat generated from the coal combustion [3], and, at the same time, coal gas with a high calorific value is also generated [4]. Moreover, the energy consumption in the oxy-thermal method is about 50% less than that in the electro-thermal method [5–6]. Liu et al. [7] proposed an oxy-thermal method that involves the use of CaO powder. In their study, the reaction temperature was reduced to about 1700°C when CaO and char powders were used to form CaC2 [8]. Furthermore, to improve the reactivity, the use of bio-char as the carbon source for CaC2 production has been recommended [9–10]. Studies have shown that the CaO diffusion controls the formation of CaC2 [11–14]. Thus, the contact of reactant
particles is crucial for the process. An increased contact area will improve the mass transfer rate of CaO, leading to a
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