Effects of preheating primary air and fuel size on the combustion characteristics of blended pinewood and corn straw in a fixed bed.

This research investigated the effects of preheating primary air and fuel size on combustion behaviors of pinewood and corn straw (50% ratio) in a fixed bed. Primary air temperature (T air) was ranged in 20–130 °C, and the fuel size was varied in the range of 3–8 cm in length, which affected the whole combustion efficiency, emissions of hazardous pollutants and alkali metals and chloride. Results showed that by increasing T air the ignition delay time first decreased by 40% and then increased, and both burning and ignition rates increased by 60%; however, the emissions of CO 2 , CO and CH 4 increased first, and then decreased. At the T air = 85 °C the smallest unburned carbon was left in the ash; the mostly generated N-bearing species was NO followed by HCN, and then by a small of NH 3. The higher T air increased the releases of K (by 16%) to the gas phase and promoted the transfer of Cl to HCl, while mildly effects on Ca. Also, increasing fuel size to 5 cm enhanced the combustion stability and decreased the emissions of NO. Accordingly, mildly increase the fuel size and T air were found to be well-operating condition, which provide guidance for selections in large-grate boiler during blend combustion. • Combustion behaviors and emissions of biomass co-combustion were performed. • The parameters of primary air temperature and fuel size were investigated. • A proper air temperature shortened ignition delay time and promote ignition rate. • By preheating primary air increased the released of K and transfer of Cl to HCl. • A proper fuel size can improve combustion stability and decrease emissions of NO x. [ABSTRACT FROM AUTHOR]