Recent progress in the gasification reaction behavior of coal char under unconventional combustion modes. (5th February 2023)

• Record Type: Journal Article
• Authors: Zhang, Zewu; Zhao, Zhenghong; Zhang, Liqi
• Is Part Of: Applied thermal engineering. Volume 220(2022)
• Publication Date: 2023-02-05
• Subjects: Pulverized coal -- Oxy-fuel combustion -- Heat transfer -- Char gasification -- NOx emissions -- C/N synergetic reduced emissions; AR air reactor -- CBK char burnout kinetics -- CBK/E the extended version of CBK model -- CBK/G the expansion version of CBK/E model for gasification -- CCK char conversion kinetic -- CBPMK char burning and particulate matter kinetics -- CCUS carbon capture utilization and storage -- CFD computational fluid dynamic -- CLC chemical looping combustion -- COCOMO coal combustion model -- Char-CO2 char reacting with CO2 -- Char-H2O char reacting with H2O -- Char-O2 char reacting with O2 -- DFT density function theory -- DTF drop tube furnace -- EFR Entrained Flow Reactor -- FR fuel reactor -- IEA International Energy Agency -- IFRF International Flame Research Foundation -- MILD moderate or intense low oxygen dilution -- MILD-oxy moderate or intense low-oxygen dilution-oxy-fuel -- MCF MILD combustion furnace -- POC pressurized oxy-fuel combustion -- POCS pressurized oxy-fuel combustion system -- PBCS pilot-scale bias combustion system -- PM particulate matter -- SKIPPY surface kinetics in porous particle -- TGA thermogravimetric analysis; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2022.119742
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: Char gasification behavior during unconventional combustion modes are introduced. Influences of operating conditions on char gasification behavior are discussed. Effects of char gasification on coal combustion characteristics are analyzed. Currents and application scenarios of unconventional combustion are summarized. The strategy for both NOx and CO2 reduced emissions is proposed and prospected. Abstract: Compared with conventional air combustion, the combustion mode and medium of unconventional combustion technologies (oxy-fuel combustion, moderate or intense low oxygen dilution (MILD) combustion, MILD-oxy combustion, pressurized oxy-fuel combustion (POC), and chemical looping combustion (CLC)) exhibit significant changes, and the gasification behavior of coal char also changes, which can influence the flame temperature, heat transfer, char combustion, NOx emissions, and even particulate matter (PM) formation. This study systemically reviews the current progress in coal char gasification reaction behavior under different unconventional combustion modes. First, the combustion principle and char gasification behavior during unconventional combustion modes of pulverized coal are summarized. Next, the effects of the operating conditions (such as temperature, bulk diffusivity, and species concentration, etc.) on the gasification behavior are discussed. The transformation between the combustion and gasification regimes during pulverized coal combustion can be realized by adjusting the operating parameters. In addition, the influencing mechanisms of the gasification reaction on pulverized coal combustion, including flame temperature, heat transfer, char burnout, NOx emissions and PM formation, are clarified. Especially, NOx emissions can be further reduced by enhancing char gasification with three aspects: the dilution oxygen effect, homogeneous reduction effect, and heterogeneous reduction effect. Besides, the current challenges of these unconventional combustion technologies are summarized, and their application scenarios are expected to achieve CO2 mitigation targets. Finally, this work concludes it necessary to explore the internal association between enhanced gasification and reduced NOx emissions, which is expected to provide valuable guidance for C/N synergetic reduced emissions in the wide applications of carbon-based solid fuels.