柠檬酸盐法烟气脱硫机理

柠檬酸盐法烟气脱硫是治理二氧化硫污染的方法之一。为了从理论上阐明柠檬酸盐溶液吸收和解吸二氧化硫的机理，为脱硫实验和工业应用提供理论指导，本文应用多元缓冲溶液理论和计算机数值计算方法相结合，通过对柠檬酸盐溶液吸收二氧化硫过程中形成的柠檬酸-柠檬酸钠-亚硫酸多元缓冲溶液体系的研究，从理论上分析和计算了多元缓冲溶液的初始pH值、分布系数、缓冲指数和缓冲容量对缓冲溶液性质的影响。结果表明，吸收液中柠檬酸根各种形态的离子分布随着溶液酸度的变化而发生改变，脱硫过程中起缓冲作用的主要离子是H₂Ci^-和HCi^2-;吸收过程中，柠檬酸的形态变化为Ci^3-－HCi^2-－H₂Ci^-－H₃Ci，解吸过程则为H₃Ci－H₂Ci^-－HCi^2-－Ci^3-;当pH＝2.5～6.5时，二氧化硫主要以HSO^-₃形式存在，HSO^-₃在pH＝3.5～5.5时最高可达99%;当pH=4.5～5.5时柠檬酸盐溶液的缓冲能力最强;综合考虑吸收与解吸过程，吸收液较合理的pH值应在4.5左右。

Mechanism of flue gas desulfurization with citrate solution

Flue gas desulfurization with citrate solution is one of the methods to tackle sulfur dioxide pollution.In order to theoretically elucidate the mechanism of absorption and desorption of sulfur dioxide by citrate solution and provide theoretical instruction for experiments and industrial application, the influence of initial pH, distribution coefficient, buffer index and buffer capacity on the properties of the buffer solution were studied in this work.The study was performed through examining the multiple buffer solution system of citric acid - sodium citrate - sulfurous acid formed in the process of desulfurization by applying the theory of multi-buffer solution combined with the method of computer numerical calculation.The results showed that the distribution of various citric acid radical ions in the solution varied with the solution acidity.H₂Ci^-and HCi^2-played the dominant role in the buffer action during the desulfurization process.The transformation of the citric acid radical ions was Ci₃^-－HCi^2-－H₂Ci^-－H₃Ci in the absorption process and H₃Ci－H₂Ci^-－HCi^2-－Ci^3- in the desorption process.When pH＝2.5—6.5，the sulfur dioxide in the absorption solution existed mainly as HSO^-₃ which could maximally reach 99% when pH＝3.5—5.5.When pH=4.5—5.5, the buffer capacity of citrate buffer solution reached its maximum.The optimal pH value of citrate solution should be about 4.5 by considering both the absorption and desorption processes.The experimental results were in good agreement with theoretical analysis.