Study On Wet Flue Gas Desulfurization Based On PH Control Technology

Energy is an important guarantee for national economic and social development.Although the energy consumption structure of our country has been optimized continuously in recent years,our country is still the largest coal producer and consumer country in the world,and the proportion of coal in the primary energy consumption of our country is almost 60%.In recent years,China has issued stricter emission standards for coal-fired power plants,which requires ultra-low emissions of pollutants such as SO₂.Limestone-gypsum wet desulfurization technology is the most widely used flue gas desulfurization technology in China at present.The dual-pH process developed on this technology can reduce scale formation and achieve higher desulfurization efficiency.In this paper,aiming at the problem of pH control and improvement of desulfurization efficiency,the variation of pH of desulfurization slurry and the influencing factors of desulfurization efficiency are studied.The pH of the slurry will change in the process of flue gas desulfurization.By adding hydrochloric acid to the calcium carbonate solution,the variation of pH of the desulfurization slurry can be simulated.Firstly,by slurry titration experiment,the effect of titration speed,concentration,temperature and composition on the pH of slurry was studied.The experimental results show that the faster the titration rate was,the faster the slurry pH decreased,and the faster the recovery of pH after the titration was stopped.The pH-buffering effect of slurry increased with the increase of slurry concentration,but too much Ca²⁺in the slurry will inhibit the dissolution of calcium carbonate.The slurry temperature had dual effect on the pH of slurry.SO₃^2-will seriously affect the pH recovery capacity of the slurry,so it's important to pay attention to the oxidation of SO₃^2-.Secondly,based on the engineering validation system,the operation data of the dual-pH desulfurization unit were studied and analyzed.The results showed that the pH change of the absorber slurry had a synchronous periodic relationship with the slurry flow rate of the absorber,but the recovery of the absorber pH had some delay with the slurry flow rate.While the change of pH difference of the main and secondary slurry pool was almost completely synchronized with the change of the pH value of the absorber,and the pH difference between the main and secondary slurry pool decreased with the increase of the pH of absorber.The difference of pH between the slurry in the absorber and the tank outside the tower decreased with the increase of flue gas volume,inlet SO₂ concentration and pH of the main slurry pool,and increased with the increase of inlet smoke temperature,which can reach more than 0.3.The desulfurization efficiency of dual-pH desulfurization system decreased with the increase of flue gas volume,inlet SO₂ concentration and inlet flue gas temperature,and increased with the increase of pH in main slurry pool,which can reach more than 99.9%.