Effect of coaxial secondary-air distribution on thermal modification, combustion and NOx emissions of pulverized coal using purifying-combustion technology
{"title":"Effect of coaxial secondary-air distribution on thermal modification, combustion and NOx emissions of pulverized coal using purifying-combustion technology","authors":"","doi":"10.1016/j.fuel.2024.133419","DOIUrl":null,"url":null,"abstract":"<div><div>To meet increasingly stringent NO<em><sub>x</sub></em> emission standards for coal-fired boilers, purification-combustion technology had garnered attention due to its great potential for NO<em><sub>x</sub></em> reduction. Central to this technology was high-temperature reduction unit (HTRU). Previous studies focused on the influence of operating parameters in the HTRU. Nevertheless, the optimization of its structural design was often neglected. This deficiency limited the improvement of its performances, including fuel activation and fuel-N removal, and thus hindered NO<em><sub>x</sub></em> emission control. Addressing this gap, this study systematically investigated the impact of coaxial air nozzle designs in the HTRU, including single-channel and dual-channel configurations, on thermal modification, combustion, and NO<em><sub>x</sub></em> emission characteristics in a 30 kW purification-combustion test rig. Experimental variables for these designs were air jet velocity (<em>v</em><sub>se</sub>) and staged air ratio (<em>c</em><sub>12</sub>). The findings revealed that the purifying burner effectively converted pulverized coal into high-temperature coal gas and highly reactive coal char. CO and NO<sub>2</sub> served as the predominant combustible gas and nitrogen-containing oxide respectively in the coal gas, and their concentrations increased as <em>v</em><sub>se</sub> and <em>c</em><sub>12</sub> increased. Additionally, these conditions improved the particle structure, reactivity, and organic component conversion rates of the coal char. The purifying modification positively impacted combustion efficiency improvement and NO<em><sub>x</sub></em> emission control, resulting in NO<em><sub>x</sub></em> emission reduction while improving combustion efficiency under these conditions. Notably, NO<em><sub>x</sub></em> emissions dropped to a minimum of 54.03 mg/m<sup>3</sup> (@6% O<sub>2</sub>) with combustion efficiency of 99.43 % when <em>v</em><sub>se</sub> and <em>c</em><sub>12</sub> increased to 11.44 m/s and ∞ respectively.</div></div>","PeriodicalId":325,"journal":{"name":"Fuel","volume":null,"pages":null},"PeriodicalIF":6.7000,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Fuel","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0016236124025687","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
To meet increasingly stringent NOx emission standards for coal-fired boilers, purification-combustion technology had garnered attention due to its great potential for NOx reduction. Central to this technology was high-temperature reduction unit (HTRU). Previous studies focused on the influence of operating parameters in the HTRU. Nevertheless, the optimization of its structural design was often neglected. This deficiency limited the improvement of its performances, including fuel activation and fuel-N removal, and thus hindered NOx emission control. Addressing this gap, this study systematically investigated the impact of coaxial air nozzle designs in the HTRU, including single-channel and dual-channel configurations, on thermal modification, combustion, and NOx emission characteristics in a 30 kW purification-combustion test rig. Experimental variables for these designs were air jet velocity (vse) and staged air ratio (c12). The findings revealed that the purifying burner effectively converted pulverized coal into high-temperature coal gas and highly reactive coal char. CO and NO2 served as the predominant combustible gas and nitrogen-containing oxide respectively in the coal gas, and their concentrations increased as vse and c12 increased. Additionally, these conditions improved the particle structure, reactivity, and organic component conversion rates of the coal char. The purifying modification positively impacted combustion efficiency improvement and NOx emission control, resulting in NOx emission reduction while improving combustion efficiency under these conditions. Notably, NOx emissions dropped to a minimum of 54.03 mg/m3 (@6% O2) with combustion efficiency of 99.43 % when vse and c12 increased to 11.44 m/s and ∞ respectively.
期刊介绍:
The exploration of energy sources remains a critical matter of study. For the past nine decades, fuel has consistently held the forefront in primary research efforts within the field of energy science. This area of investigation encompasses a wide range of subjects, with a particular emphasis on emerging concerns like environmental factors and pollution.