| The purification process in zinc hydrometallurgy is to remove impurity ions of Cu2+, Cd2+, Co22+, Ni2+, etc by adding materials in the ZnSO4leachate such that the purified solution satisfies the requirements for electrolyzing. Due to the zinc sulphate solution is characterized by a high temperature, high concentration, high viscosity, and detection of metal ions concentration is accomplished by manual, which has long lag time, it is difficult to realize optimal operation for the entire purification process. Therefore, the research on the online polarographic detection method for detection of impurity ions concentration is of great significance for both optimizing process control and emission reduction.Based on the analysis of characteristics of purification process and detected parameters, an online polarographic analysis method is introduced to detect the Multi-Metallic components concentration and an automatic sampling, injection system and an online analysis process are designed, then solutions to solve the problems of noise disturbance and overlapped peaks resolving are studied. The main content is descriped as follows.1) A novel automatic sampling and injection method to solve the problems of pipeline crystallization and sampling difficulties are put forward, and a platform for online precision dropping mercury polarography detection is studied, which realize rapid polarographic detection, precision dropping mercury control and automatic system cleaning.2) A weighted moving average filter algorithm for embedded online software filtering and an improved wavelet de-noising method used to decrease the computer data noise and transform the derivation of polarographic wave are presented by analyzing the interference factors of the online detection signal. Furthermore, a double wavelet transform filtering method for improving the filtering effect of the polarographic waveform is investigated and the effects of filtering are evaluated.3) Combined with the analysis of the characteristics of overlapping peaks in polarographic wave, a method based on wavelet transform and new similar Gaussian fitting is proposed, which realizes the separation of the overlapping peaks of Co2+and Zn2+with high concentration gradient. Finally, experimental results are compared and the effects of separation are evaluated, which demonstrate the effectiveness of the proposed method.The online polarographic detection of the impurity ion concentration in the purification process of zinc sulphate solution is preliminarily realized on the basis of analyzing and solving these three difficult problems, which lays a solid foundation for the development of the online analyzer. |
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