A Study On The Process Of Simultaneous Desulfurization And Denitration From Flue Gas By Absorption Method

The aim of this thesis is to develop a process of simultaneous desulfurization（de-SO2） and denitration（de-NO） from flue gas by absorption method. Based on ammonia desulfurization and liquid phase denitration, the technique of adsorption of SO2 and NO by complex absorbent were investigated. The key parameters considered included complex absorbent composition, concentration, additives and so on.The mechanism of simultaneous de-SO2 and de-NO by complex absorbent absorption method is as follows: When absorbent ammonium salt solution containing ethylenediamine cobalt contacts with flue gas, ethylenediamine cobalt reacts with NO in flue gas to form NO complex. Then NO in the complex reacts with oxygen in air to form NO2-complex. And NO2 in the complex reacts with aqueous ammonia to form ammonium nitrate. SO2 in the flue gas was absorbed by absorbent solution. Then SO2 in liquid phase was oxidized as sulfate radical and reacted with aqueous ammonia to form ammonia sulfate. Therefore, the purpose was reached for simultaneous de-SO2 and de-NO in one facility.Transition metal（iron, cobalt, nickel, zinc） salt solution was employed to react with ligand ammonia and absorption liquid containing complex was received. In order to improve the complexation reaction ability of absorption liquid, additive urea was added to the absorption liquid. Removing SO2 and NO by complex absorption method featured as moderate operation condition, the product used as fertilizer etc.Cobalt salt and ethylenediamine complexation reaction absorbent was investigated. The examined parameters were cobalt salt concentration and urea concentration. The experiment was produced to studied the efficiency of de-SO2 and de-NO. Consideration the similar characteristics, complex absorption absorbent containing nickel, iron and zinc were tested also.The study showed that Co²⁺ and Fe²⁺ reacted with ammonia had a better performance than Ni²⁺and Zn²⁺ on desulfurization and denitration. On the experimental gas flow（0.5 mol·L-1）, the best recipe of desulfurization and denitration for cobalt ammonia complex were: the concentration of [Co（NH3）6]²⁺ was 1.4 mol·L-1, the ammonia’s was 0.8 mol·L-1（ ligand was excluded）, the urea’s was 0.4 mol·L-1 and the absorption temperature was indoor temperature. The desulfurization rate could be above 95%, and the denitration can reach to about 85%.