| As the main desulfurization technology widely used in thermal power plants,wet limestone-gypsum flue gas desulfurization(Wet FGD)process has two key technical indicators: desulfurization rate and calcium sulfite oxidation rate.After years of research and industrial applications,desulfurization rate of the technology can meet the standards of pollutant emissions,and achieve the stringent requirements of ultra clean emissions.But there exists a series problems in the control of oxidation in Wet FGD slurry oxidation system,such as deposition and slagging in WFGD system?inadequate oxidation and per-oxidation.Therefore,how to control the process of forced oxidation desulfurization system scientifically and effectively,to make sure the high rate of calcium sulfite oxidation,thereby preventing scaling,while reducing the energy consumption of FGD system,is the hot issues for desulfurization system of power plant to solve in the current.The desulfurization system which includes the absorption of SO2 and the oxidation of sulfite is a complex process.At present,the desulfurization system has simple p H control.China is not aware of the meaning of oxidation control to the flue gas desulfurization slurry.In terms of desulfurization process,it is not enough to rely on a control method,which requires the coordination of the two control methods.The change of p H and ORP in the process of calcium sulfite oxidation was inquired by experiment.Based on the nature of the oxidation reaction of the desulfurization system as a starting point,the p H and ORP dual control strategy is proposed,that is to put p H and ORP as control parameters of slurry oxidation,relying on real-time monitoring the changes of p H and ORP to determine the oxidation state of desulfurization slurry,and in time to make the appropriate adjustments to oxidation air flow.In order to verify the feasibility of the double control theory in the oxidation control of desulfurization slurry,the change characteristics of oxidation rate curve under different substrate concentration were studied in the experiment.The response of p H and ORP to oxidation process were also obtained.The ideal experimental results were obtained.ORP is a function of many factors in the process of the oxidation of Ca SO3: the reaction temperature,the slurry p H?DO(Dissolved Oxygen)?[HSO3-]/[SO42-] and so on.A L16(45)orthogonal experiment was designed to research the factors of ORP changing in desulfurization slurry oxidation in the different period.The order of the contribution of each factor to ORP in desulfurization slurry according to the influences of different factors on ORP was obtained.And the impact trend of the various factors to the ORP changing was analyzed later.In this paper,the reaction mechanism of slurry oxidation was clarified,and the "major factor" of ORP changing in different oxidation stage was obtained,which provided a theoretical guide for precise control of oxidation in FGD slurry oxidation system.The field test was carried out in a power plant in the southwest of China,usingadvanced ORP measurement means to find the best ORP control range of desulfurization slurry oxidation.Combined with real time online ion monitoring parameter data,the field test verified the practical feasibility of ORP to indicate the oxidation state of slurry.And we got the opening experience of the number of oxidation fan based on ORP,at the same time,achieved the optimization of the oxidation fan operation in FGD system.This paper first introduced the concept of p H and ORP dual control into the desulfurization slurry.It can not only control the oxidation state of slurry accurately,but also avoid the blind control of oxidation fans to save energy.Real time control overcome the hysteresis of traditional oxidation control and ensure the desulfurization system operate stably and efficiently.The product gypsum can also bring some economic benefits to coal-fired power plant.The work laid the foundation for the development and application of the technology. |
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