Kinetics of Hydrothermal Reactions of Minerals in Near-critical and Supercritical Water

作     者：ZHANG Ronghua HU Shumin ZHANG Xuetong 

作者机构：Open Research Laboratory of Geochemical KineticsChinese Academyof Geological Sciences26 Baiwanzhuang RoadBeijing 100037 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2000年第74卷第2期

页      面：400-405页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：We would like to thank the Ministry of Science and Technology and the Ministry of Land and Resources for supporting our project The experimental results presented in this paper were obtained with the financial support of GTB basic research fund 9501115 the“Climbing Project”95-Pre-39,G1999043212 National Natural ScienceFoundation of China grant 29673008 

主　　题：kinetics hydrothermal reaction critical state 

摘      要：This work presents new experimental results on the kinetics of mineral dissolution in near-critical and supercritical water in a temperature range (T) from 25 to 400°C and a constant pressure of 23 MPa. Kinetic experiments were carried out by using a flow reactor (packed bed reactor) of an open system. The dissolution rates of albite and magnetite were measured under these experimental conditions. Na, Al and Si release rates for albite dissolution in water were measured as a function of the temperature and flow velocity in the reaction system. The maximum release rates of Na, Al and Si of albite dissolution in the hydrothermal flow systems under different flow velocities were always obtained at 300°C, that is to say, the maximum albite dissolution rates in the flow systems, regardless of different flow rates, were repeatedly measured at 300°C. Results indicate a wide fluctuation in albite dissolution rates occurring close to the critical point of water. The dissolution rates increased when the temperatures increased from 25 to 300°C and decreased when the temperatures increase from 300 to 400°C. At some flow velocities, the dissolution rates rose as the temperature surpassed 374°C. Albite dissolution was incongruent in water at most temperatures. It was only at 300°C that albite dissolution was congruent. The albite dissolution from 25 to 300°C (at 23 MPa) will change from incongruent to congruent, whereas from subcritical 300 to 400°C (at 23 MPa), the dissolution will change from congruent to incongruent. The release ratio of Al/Si (or Na/Si) is positive at T300°C. The dissolution rates of magnetite in water increased with increasing T until T at the critical point of water or around it. The authors believe that this is caused by the wide fluctuations in water properties under the conditions from the near-critical to supercritical state.