Su Zhang , Yixiang Zhang , Yong Zhang , Yixiang Shu , Liming Cui , Tedla Medhane Embaye , Tao Niu , Yili Zhang , Houzhang Tan , Xuebin Wang
{"title":"煤灰中的碱金属和碱土金属(AAEMs)对合成氨和煤共同燃烧过程中 NH3 氧化的催化作用的深入研究","authors":"Su Zhang , Yixiang Zhang , Yong Zhang , Yixiang Shu , Liming Cui , Tedla Medhane Embaye , Tao Niu , Yili Zhang , Houzhang Tan , Xuebin Wang","doi":"10.1016/j.combustflame.2024.113493","DOIUrl":null,"url":null,"abstract":"<div><p>Ammonia as an eco-friendly and carbon-free energy has been greatly concerned at home and abroad. It has been utilized in the ammonia and coal co-firing process, demonstrating robust market viability. Nonetheless, due to the element N within ammonia causing the production of NO<sub>x</sub>, the catalytic effect and reaction mechanics of AAEMs in coal ash on the NH<sub>3</sub> oxidation remain elusive. In this study, the catalytic effects of AAEMs (K, Ca, Na and Mg) on NH<sub>3</sub> oxidation were investigated through experiments, and the reaction mechanism was elucidated from a microscopic perspective by density functional theory (DFT). The experimental results show that the addition of AAEMs does enhance the oxidation potential of NH<sub>3</sub> during coal and ammonia co-firing process, and promote the transformation of NH<sub>3</sub> to NO, N<sub>2</sub>O and N<sub>2</sub>. However, the promotion effect of different AAEMs is different, consequently influencing the selectivity of NH<sub>3</sub> oxidation pathway. At 600–800 °C, alkaline earth metals (Ca and Mg) facilitate the oxidation of NH<sub>3</sub> while alkali metals (K and Na) have the opposite effect. Mg has the highest promoting effect on the conversion of NH<sub>3</sub> to NO at 600–800 °C, but the catalytic effect of K and Na is more dominant from 800 °C to 900 °C. The transformation from NH<sub>3</sub> to N<sub>2</sub>O remains the same, but the catalytic impact of Ca is mostly pronounced. AAEMs can reduce thermal decomposition activation energy of N<sub>2</sub>O, and the decomposition of N<sub>2</sub>O can be promoted at 800 °C. The DFT results indicate that AAEMs can enhance the adsorption capacity of NH<sub>3</sub> on the active site of the coal ash surface, and reduce the activation energy of NH<sub>3</sub> oxidation, thereby accelerating the transformation of NH<sub>3</sub> to other nitrogen-containing species. This study provides new insight into the evidence for the enhanced catalytic effect of AAEMs on NH<sub>3</sub> oxidation during ammonia and coal co-firing process.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":null,"pages":null},"PeriodicalIF":5.8000,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"A deep insight into catalytic effects of alkali and alkaline earth metals (AAEMs) in coal ash on NH3 oxidation during ammonia and coal co-firing process\",\"authors\":\"Su Zhang , Yixiang Zhang , Yong Zhang , Yixiang Shu , Liming Cui , Tedla Medhane Embaye , Tao Niu , Yili Zhang , Houzhang Tan , Xuebin Wang\",\"doi\":\"10.1016/j.combustflame.2024.113493\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Ammonia as an eco-friendly and carbon-free energy has been greatly concerned at home and abroad. It has been utilized in the ammonia and coal co-firing process, demonstrating robust market viability. Nonetheless, due to the element N within ammonia causing the production of NO<sub>x</sub>, the catalytic effect and reaction mechanics of AAEMs in coal ash on the NH<sub>3</sub> oxidation remain elusive. In this study, the catalytic effects of AAEMs (K, Ca, Na and Mg) on NH<sub>3</sub> oxidation were investigated through experiments, and the reaction mechanism was elucidated from a microscopic perspective by density functional theory (DFT). The experimental results show that the addition of AAEMs does enhance the oxidation potential of NH<sub>3</sub> during coal and ammonia co-firing process, and promote the transformation of NH<sub>3</sub> to NO, N<sub>2</sub>O and N<sub>2</sub>. However, the promotion effect of different AAEMs is different, consequently influencing the selectivity of NH<sub>3</sub> oxidation pathway. At 600–800 °C, alkaline earth metals (Ca and Mg) facilitate the oxidation of NH<sub>3</sub> while alkali metals (K and Na) have the opposite effect. Mg has the highest promoting effect on the conversion of NH<sub>3</sub> to NO at 600–800 °C, but the catalytic effect of K and Na is more dominant from 800 °C to 900 °C. The transformation from NH<sub>3</sub> to N<sub>2</sub>O remains the same, but the catalytic impact of Ca is mostly pronounced. AAEMs can reduce thermal decomposition activation energy of N<sub>2</sub>O, and the decomposition of N<sub>2</sub>O can be promoted at 800 °C. The DFT results indicate that AAEMs can enhance the adsorption capacity of NH<sub>3</sub> on the active site of the coal ash surface, and reduce the activation energy of NH<sub>3</sub> oxidation, thereby accelerating the transformation of NH<sub>3</sub> to other nitrogen-containing species. This study provides new insight into the evidence for the enhanced catalytic effect of AAEMs on NH<sub>3</sub> oxidation during ammonia and coal co-firing process.</p></div>\",\"PeriodicalId\":280,\"journal\":{\"name\":\"Combustion and Flame\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.8000,\"publicationDate\":\"2024-05-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Combustion and Flame\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0010218024002025\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ENERGY & FUELS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Combustion and Flame","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0010218024002025","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
A deep insight into catalytic effects of alkali and alkaline earth metals (AAEMs) in coal ash on NH3 oxidation during ammonia and coal co-firing process
Ammonia as an eco-friendly and carbon-free energy has been greatly concerned at home and abroad. It has been utilized in the ammonia and coal co-firing process, demonstrating robust market viability. Nonetheless, due to the element N within ammonia causing the production of NOx, the catalytic effect and reaction mechanics of AAEMs in coal ash on the NH3 oxidation remain elusive. In this study, the catalytic effects of AAEMs (K, Ca, Na and Mg) on NH3 oxidation were investigated through experiments, and the reaction mechanism was elucidated from a microscopic perspective by density functional theory (DFT). The experimental results show that the addition of AAEMs does enhance the oxidation potential of NH3 during coal and ammonia co-firing process, and promote the transformation of NH3 to NO, N2O and N2. However, the promotion effect of different AAEMs is different, consequently influencing the selectivity of NH3 oxidation pathway. At 600–800 °C, alkaline earth metals (Ca and Mg) facilitate the oxidation of NH3 while alkali metals (K and Na) have the opposite effect. Mg has the highest promoting effect on the conversion of NH3 to NO at 600–800 °C, but the catalytic effect of K and Na is more dominant from 800 °C to 900 °C. The transformation from NH3 to N2O remains the same, but the catalytic impact of Ca is mostly pronounced. AAEMs can reduce thermal decomposition activation energy of N2O, and the decomposition of N2O can be promoted at 800 °C. The DFT results indicate that AAEMs can enhance the adsorption capacity of NH3 on the active site of the coal ash surface, and reduce the activation energy of NH3 oxidation, thereby accelerating the transformation of NH3 to other nitrogen-containing species. This study provides new insight into the evidence for the enhanced catalytic effect of AAEMs on NH3 oxidation during ammonia and coal co-firing process.
期刊介绍:
The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on:
Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including:
Conventional, alternative and surrogate fuels;
Pollutants;
Particulate and aerosol formation and abatement;
Heterogeneous processes.
Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including:
Premixed and non-premixed flames;
Ignition and extinction phenomena;
Flame propagation;
Flame structure;
Instabilities and swirl;
Flame spread;
Multi-phase reactants.
Advances in diagnostic and computational methods in combustion, including:
Measurement and simulation of scalar and vector properties;
Novel techniques;
State-of-the art applications.
Fundamental investigations of combustion technologies and systems, including:
Internal combustion engines;
Gas turbines;
Small- and large-scale stationary combustion and power generation;
Catalytic combustion;
Combustion synthesis;
Combustion under extreme conditions;
New concepts.