Abstract
The residue from desulfurization and denitrification of exhaust gas treatment process with pyrolusite ore as absorbent is regarded as a potential source of iron and manganese. In this study, an extraction process is proposed for recovery of iron and manganese with ammonium sulphate roasting followed by sulphuric acid leaching. Firstly, the conversion mechanism was analyzed through mineral phase analysis of roasting products at different roasting temperature by means of X-ray diffraction (XRD) technology. Then, the parameters of the roasting procedure such as roasting temperature and time, ammonium sulphate dosage, leaching temperature, leaching time, and sulphuric acid concentration are examined. The results implicate that the iron oxide and manganese dioxide in the residue are firstly converted into the water-soluble ( NH 4 ) 3 Fe ( SO 4 ) 3 and ( NH 4 ) 2 Mn 2 ( SO 4 ) 3 at 200–350 °C, and then the more stable NH 4 Fe ( SO 4 ) 2 and MnSO 4 are formed, at temperature higher than 350 °C. Under optimum conditions, 95.2% Fe and 97.0% Mn can be extracted. Reactant diffusion through inert layer of silicon dioxide was considered as the rate-limiting step for iron extraction with an activation energy of 20.56 kJ/mol, while, the recovery process of Mn was controlled by both reactant diffusion and chemical reaction with an activation energy of 29.52 kJ/mol.
Highlights
SO2 and NOx emission from combustion of coal, fuel oils and waste have brought significantly important effects on environment and human health
The roasting kinetics of pyrolusite absorption residue (PAR) with ammonium sulphate was studied by water leaching in the examine the decomposition gas of ammonium sulphate, and the results show that the NH3 is the main temperature range of 275–400 °C
The process of ammonium sulphate roasting followed by sulphuric acid leaching
Summary
SO2 and NOx emission from combustion of coal, fuel oils and waste have brought significantly important effects on environment and human health. Various kinds of technologies [1,2] have been developed to control and reduce SO2 and NOx emissions worldwide Among these methods, pyrolusite ore adsorption has been regarded as one of the most promising technologies [2,3]. Pyrolusite is a manganese oxide ore with manganese dioxide as its main component [5], which can oxidize the SO2 and NO, NO2 in the exhaust gas into SO24− and NO3− , respectively. These reactions can be written as the following: MnO2 (s) + SO2 = Mn2+ + SO24−
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