Study On Redox Characteristics Of Circulating Slurry In Wet Flue Gas Desulfurization

The wet flue gas desulfurization of goal-fired power plants,the energy consumption of oxidation fan occupies about 15%of the energy consumption of the whole wet flue gas desulfurization system,it is an important part of power plant energy consumption.Due to the large selection of oxidation fan in goal-fired power plants,as well as the current most of the crew at low load operation condition,the desulfurization circulating slurry in the bottom will be peroxided and a lot of energy waste and a series of problems.With the gradually work of saving energy and reducing consumption,oxidation fan energy-saving technology research has been more and more attention.The main technical problem involved in oxidation process in wet flue gas desulfurization circulating slurry include:the ion Equilibrium relation in the Oxidation of Sulfite Ions;the Equilibrium relation in oxygen mass transfer process and the determination of dissolved oxygen content which the regulatory index for regulating the energy saving of oxidation fans.The factors affecting the oxidation of the slurry include:the dissolved oxygen content,the pH value and the oxidizing air volume.This article first combines the methods of building models and mechanisms,preliminary exploration of oxidation performance of sulfite ion.Constructed the oxidation process model of sulfite ion and the model of oxygen mass transfer process,The dual-mode theory and chemical equilibrium calculation methods were used to explore the gas-liquid mass transfer process and oxidation reaction in the oxidation process.We acquired the material balance equation,reaction equilibrium equation and reaction equilibrium coefficient in the oxidation process.In the entire process of forced oxidation,the mass transfer of oxygen is mainly controlled by liquid film.Secondly,I designed and built a desulfurization circulating slurry oxidation simulation test bench.Experimental study of the oxidation characteristics of CaCO3 solution,and the effects of solution pH,CaCO3 concentration and oxidizing air volume on the oxidation performance of the solution were investigated.The resule showed that:the key factors affecting sulfite ion oxidation are CaSO3 concentration and oxidation air volume.When the content of sulfite ion in the solution is more than 0.01 mol/L,the dissolved oxygen content in the solution will increase from 0 mg/L to 0.6 mg/L;when the content of sulfite ion is between 0.008 and 0.01mol/L,the dissolved oxygen content in the solution will increase from 0.6mg/L to 2mg/L,at this time,the sulfite ion content in the solution has met the coal-fired power plant's plaster emission standards;when the sulfite ion content is less than 0.008g/L,the dissolved oxygen content in the solution will rise steadily with the decrease of the sulfite ion content.Aimed at the 135 MW unit of the coal-fired power plant,it shows that the dissolved oxygen content in the circulating slurry can be kept at 2 mg/L within 5 minutes of the retention time,which can ensure that the circulating slurry is fully oxidized,and the sulfite ion content reaches desulfurization gypsum emission standards.The energy-saving technology of the oxidation fan in this paper is to detect the oxidation condition of the circulating slurry at the bottom of the desulfurization tower in real time and guide the regulation of the oxidation fan frequency.In the case of low-load operation of the unit,ensuring that the desulfurization cycle slurry is fully oxidized,the energy consumption of the oxidation fan is reduced to achieve the purpose of energy saving.In the final oxidation fan control process,real-time frequency modulation by the oxidation fan ensures that the dissolved oxygen content in the circulating slurry is around 2 mg/L.