Study on the co-combustion behavior of semi-coke and typical biomass: Combustion, NO emission and ash characteristics analysis

Abstract

In order to realize the integrated utilization of semi-coke (SC) and biomass, the co-combustion behavior of SC and three typical biomass (corn stalk (CS), rice stalk (RS) and pine wood (PW)) was experimentally studied in terms of combustion, NO emission and ash characteristics. The results of thermogravimetric (TG) analysis show that the positive interactions between SC and biomass mainly occur at the later combustion stage of blends, leading to the combustion of SC in advance. Based on the ignition and comprehensive combustion indexes, the optimal blending ratios of CS and RS are considered as 20%. The co-combustion experiments conducted at the biomass blending ratio of ≤40% in an electrical-heated fluidized bed rig also prove that the combustion performance of SC can be improved by biomass, and the NO emission decreases with the biomass blending ratio. The ash deposition problem should be paid attention when more than 20% CS or RS is blended, which is related to the alkali aluminosilicates and K3Na(SO4)2 in the fly ash of SC/CS and SC/RS blends, respectively. Meanwhile, the effect of PW in this regard is limited due to its extreme low ash content. In summary, the blending ratio for CS and RS is suggested as 20% when co-combusting with SC, while the appropriate PW blending ratio is 40%. The achievements of this study are conducive to the clean and high-efficiency utilization of semi-coke and CO2 emission reduction.