Energy & Fuels, Vol.32, No.2, 2630-2637, 2018
Heavy Metal Control by Natural and Modified Limestone during Wood Sawdust Combustion in a CO2/O-2 Atmosphere
This paper experimentally investigated the capture performance of natural and modified limestone for Cr, Cu, Pb, and Zn during the wood sawdust combustion in an 800O2/2002 atmosphere. The addition dosage of limestone had significant effects on the capture efficiency for Cu and Pb, but not for Cr and Zn based on the two-factor analysis of variance method. The presence of NaCl always lowered the capture efficiency for Pb, whereas, for Cu and Zn, the effects of NaCI turned from negative to positive as the temperature increased. Limestone modified with K2CO3 improved the capture performance for Cr and Cu, while limestone modified with Al-2(SO4)(3) improved the capture performance for all studied heavy metals. The best pretreatments for capturing Cu, Zn, Cr, and Pb were modified limestone with Al-2(SO4)(3) (ion ratio gamma = 15), Al-2(SO4)(3) (gamma = 10), K2CO3 (gamma = 10), and Al-2(SO4)(3) (gamma = 10), respectively. The degree of improvement depended on the specific inorganic salt type and ion ratio. Therefore, choosing a reasonable inorganic modification method should depend on specific targeted heavy metals. The results conduce to understand the heavy metal control mechanism of limestone and explore a high-efficiency and low-cost method for heavy metal control during wood oxy-fuel combustion.