Decoupled combustion of alcohol extracted herb residues with blending wasted activated coke: Insight into in-situ NOx emission control by pyrolysis products. (1st October 2022)

• Record Type: Journal Article
• Authors: Wang, Wenyan; Liu, Xuan; Zhang, Guangyi; Zhu, Xinyu; Shi, Bowen; Zhang, Jianling; Xu, Guangwen
• Is Part Of: Applied energy. Volume 323(2022)
• Publication Date: 2022-10-01
• Subjects: Alcohol extracted herb residue (AEHR) -- Decoupled combustion -- Dual fluidized bed -- Nitrogen oxides (NOx) -- In-situ nitrogen control; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2022.119505
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Controlling NOx emission from char-N was crucial for clean combustion of the AEHR. DC of the AEHR enabled good in-situ NOx reduction by its generated volatiles. 600 ℃, higher than that for bio-tar production, generated the best on-line volatiles. WAC with a low content of ash containing fewer light metals facilitated NOx reduction. Char + WAC contributed 18.81–26.51% NOx reduction during DC of AEHR + WAC. Abstract: By a self-established dual fluidized bed combustion apparatus, alcohol extracted herb residues (AEHRs), as well as their derived char and on-line volatiles, were firstly directly combusted to investigate and compare the characteristics of the resulting NOx emissions; and then, the AEHRs were subjected to decoupled combustion (DC) with addition of wasted activated coke (WAC), to realize their safe disposal/clean energy recovery. The result showed that, the DC exhibited a desirable NOx reduction effect, and the on-line volatiles, especially those from pyrolysis at 600 ℃, played a crucial role in the in-situ NOx control. The WAC inhibited NOx formation, due to its lower ash content and containing significantly fewer light metals (mainly K and Mg) than the AEHR char. When subjected to DC at the optimized conditions (600 °C pyrolysis, 850 °C combustion, excessive air ratio (ER) = 1.3 and secondary air proportion = 0.5), blending 20% WAC into the AEHR further reduced the NOx emission concentration from 217.03 to 163.82 mg m −3, corresponding to a 70.40% NOx reduction rate when compared to 553.41 mg m −3 for conventional combustion of the AEHR. Splitting the primary air revealed that the char + WAC contributed 18.81–26.51% of the total NOx reduction amount during the AEHR + WAC DC, justifying the necessity for DC to simultaneously make good use of the hot char and the on-line volatiles for reducing NOx.