Modeling And Real-time Optimization For The Conversion Rate Of SO₂ In Flue Gas Acid-making

Sulfuric acid is an important chemical raw material.It has a pivotal role in the industrial production and is widely used in various industrial sectors.Flue gas acid-making is an important method in the production of sulfuric acid.It can make full use of resources,keep the environment from pollution,and increase economic benefits for enterprises.It is increasing the conversion rate of SO2 that plays the key role in improving the efficiency of sulfuric acid production in flue gas acid-making.To increase the conversion rate of SO2,modeling and real-time optimization for the conversion rate of SO2 in flue gas acid-making is studied.Firstly,the production process of flue gas acid-making is introduced.The factors affecting the conversion rate of sulfur dioxide and the method for adjusting the temperature of the converter entrance are analyzed.Secondly,the mechanism model of SO2 conversion process is established based on the analysis of thermodynamics and kinetics of conversion of sulfur dioxide.Through the thermodynamics analysis of SO2 conversion reaction,the SO2 equilibrium conversion rate under a certain initial sulfur dioxide and oxygen concentration is obtained.Through the kinetics analysis of SO2 conversion reaction,the reaction rate of sulfur dioxide conversion reaction is obtained,and then the required conversion time to complete a conversion rate can be calculated.The computing methods for the conversion rate in a converter and the total conversion rate are obtained.The optimization objective,the optimization variables and the related constraints are analyzed.The model of temperature optimal setting of the entrance converter inlet is established.In this model,entrance temperature of each layer of the converter is the optimization variable,the maximum conversion rate of sulfur dioxide is the optimization objective.And genetic algorithm and Nelder-Mead simplex algorithm are used to solve the optimal setting problem of the converter entrance temperature in flue gas acid-making.Finally,for model parameter mismatch problem in real industrial process caused by the change of catalyst activity and other factors,the modifier-adaptation methodology is studied.The traditional modifier adaptation can be used to deal with the optimization problem of mismatched model,and it shows good performance in most cases.However,the method cannot be used directly,when the gradients of the model outputs with respect to the decision variables are difficult to calculate directly.And the simulation results show that the method cannot achieve the optimum in theory when the gradient estimation is particularly inaccurate.Therefore,a new modifier adaptation methodology for real-time optimization is proposed.A method similar to PID is used to deal with the deviation between the actual gradient and the model gradient and improve the method of modifier terms computation.The validation of the method is demonstrated by the solution of the optimal setting problem of the converter entrance temperature in flue gas acid-making and an artificial example.