Yang Song, Du Wenguang, Shi Pengzheng, Shangguan Ju, Liu Shoujun, Zhou Changhai, Chen Peng, Zhang Qian, Fan Huiling
Key Laboratory for Coal Science and Technology of Ministry of Education and Shanxi Province, Institute for Chemical Engineering of Coal, Taiyuan University of Technology, Taiyuan 030024, China.
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
PLoS One. 2016 Jun 22;11(6):e0157369. doi: 10.1371/journal.pone.0157369. eCollection 2016.
Nickel laterites cannot be effectively used in physical methods because of their poor crystallinity and fine grain size. Na2SO4 is the most efficient additive for grade enrichment and Ni recovery. However, how Na2SO4 affects the selective reduction of laterite ores has not been clearly investigated. This study investigated the decomposition of laterite with and without the addition of Na2SO4 in an argon atmosphere using thermogravimetry coupled with mass spectrometry (TG-MS). Approximately 25 mg of samples with 20 wt% Na2SO4 was pyrolyzed under a 100 ml/min Ar flow at a heating rate of 10°C/min from room temperature to 1300°C. The kinetic study was based on derivative thermogravimetric (DTG) curves. The evolution of the pyrolysis gas composition was detected by mass spectrometry, and the decomposition products were analyzed by X-ray diffraction (XRD). The decomposition behavior of laterite with the addition of Na2SO4 was similar to that of pure laterite below 800°C during the first three stages. However, in the fourth stage, the dolomite decomposed at 897°C, which is approximately 200°C lower than the decomposition of pure laterite. In the last stage, the laterite decomposed and emitted SO2 in the presence of Na2SO4 with an activation energy of 91.37 kJ/mol. The decomposition of laterite with and without the addition of Na2SO4 can be described by one first-order reaction. Moreover, the use of Na2SO4 as the modification agent can reduce the activation energy of laterite decomposition; thus, the reaction rate can be accelerated, and the reaction temperature can be markedly reduced.
由于结晶性差且粒度细，红土镍矿无法有效地用于物理方法。Na2SO4是品位富集和镍回收最有效的添加剂。然而，Na2SO4如何影响红土矿的选择性还原尚未得到明确研究。本研究采用热重联用质谱法（TG-MS），在氩气气氛下研究了添加和不添加Na2SO4时红土矿的分解情况。将约25mg含20wt%Na2SO4的样品在100ml/min的氩气流下，以10℃/min的升温速率从室温加热至1300℃进行热解。动力学研究基于微商热重（DTG）曲线。通过质谱检测热解气体成分的演变，并通过X射线衍射（XRD）分析分解产物。在前三个阶段，添加Na2SO4的红土矿分解行为与纯红土矿在800℃以下时相似。然而，在第四阶段，白云石在897℃分解，比纯红土矿的分解温度低约200℃。在最后阶段，红土矿在Na2SO4存在下分解并释放出SO2，活化能为91.37kJ/mol。添加和不添加Na2SO4时红土矿的分解都可以用一个一级反应来描述。此外，使用Na2SO4作为改性剂可以降低红土矿分解的活化能；因此，可以加快反应速率，并显著降低反应温度。
