Study On Regeneration Mechanism Of Spend Activated Carbon For Sintering Flue Gas Desulfurization And Denitrification

Activated carbon（AC）integrated desulfurization and denitrification technology,as a promising flue gas purification method,has been applied to the sintering flue gas purification process,which resulting in a large amount of spend activated carbon（SAC）.It has important economic and environmental significance to regenerate SAC for recycling.The AC used for desulfurization and denitrification in the sintering process was taken as the research object,the reasons for the deactivation of SAC were analyzed.And the method of combining solution treatment and thermal regeneration was used to regenerate SAC.The effect of Na₂CO₃ solution,HF solution pre-treatment and NH₃thermal regeneration process on the performance of AC was investigated.The main research contents are as follows:Firstly,the AC before desorption（SAC–B）and after desorption（SAC–A）and blockage in funnel were characterized by using XRF,XRD,SEM-EDS,BET and FTIR.The main phases of SAC–A are Ca SO₄,Si O₂,Fe₃O₄,NH₄Cl and（NH₄）₂SO₄.After desorption,the ammonium salt in the AC is decomposed,but Ca SO₄,Si O₂ and Fe₃O₄ are still stored in AC.Those adsorbates blocked the pores in the forms of needles and particulates,resulting in the dramatic decrease in pore parameters.The content of C–O,C=O and O–H in SAC is very low,and there are also Si–O,SO₄ group and other impurity functional groups that are not conducive to desulfurization and denitration,which leads to the deactivation of AC.Secondly,SAC–A was treated with Na₂CO₃ solution and HF solution respectively,and the sulfur conversion rate and silicon removal rate of SAC were investigated.The sulfur conversion of SAC was 95.53%when the Na₂CO₃ solution concentration,reaction time,reaction temperature and liquid-solid ratio were 0.30 mol/L,75 min,40℃and 6 ml/g,respectively.The silicon removal rate of SAC can reach 97.69%when the solution concentration,reaction time and liquid-solid ratio were 0.8 mol/L,30 min and 6 ml/g,respectively.The AC after HF solution treatment had smooth surfaces,abundant and clear pore structures.The surface impurity functional groups completely disappear,but still low content in the content of nitrogenous functional groups.Finally,the effect of thermal regeneration under NH₃ atmosphere on desulfurization and denitrification performance of regenerated activated carbon（RAC）was studied.Under the conditions of regeneration temperature 800℃,regeneration time 60min and NH₃ flow rate 80ml/min,the average desulfurization rate and denitration rate of RAC can reach 92.56%and 72.06%respectively.Thermal regeneration has a significant effect on the surface morphology.After regeneration,the pore structure got more abundant,and the surface is rough,but the skeleton is clear.The content of oxygenic functional groups reduced,but the nitrogen functional groups such as quaternary nitrogen-type（N-Q）,pyridine-type（N–6）and pyrrole-type（N–5）,increased after the thermal regeneration,which effectively improves the denitration rate of AC.