崔贝贝,王美君,常丽萍,等. 炼焦煤成焦机理再认识:“衍构成焦机理”的提出[J]. 煤炭学报,2024,49(6):2826−2839. doi: 10.13225/j.cnki.jccs.2023.0432
引用本文: 崔贝贝,王美君,常丽萍,等. 炼焦煤成焦机理再认识:“衍构成焦机理”的提出[J]. 煤炭学报,2024,49(6):2826−2839. doi: 10.13225/j.cnki.jccs.2023.0432
CUI Beibei,WANG Meijun,CHANG Liping,et al. A renew cognition of coking mechanism: Proposing the “Structure Derivation Coking Mechanism”[J]. Journal of China Coal Society,2024,49(6):2826−2839. doi: 10.13225/j.cnki.jccs.2023.0432
Citation: CUI Beibei,WANG Meijun,CHANG Liping,et al. A renew cognition of coking mechanism: Proposing the “Structure Derivation Coking Mechanism”[J]. Journal of China Coal Society,2024,49(6):2826−2839. doi: 10.13225/j.cnki.jccs.2023.0432

炼焦煤成焦机理再认识:“衍构成焦机理”的提出

A renew cognition of coking mechanism: Proposing the “Structure Derivation Coking Mechanism”

  • 摘要: 深度认识煤质特性、探究炼焦煤成焦机理是开发精细化配煤炼焦技术的关键。传统成焦机理仅宏观地解释了炼焦煤炭化过程中的塑性和黏结现象,缺乏对煤转变为焦炭所涉及的化学反应的深层次认识。基于此,从分子水平阐述了炼焦煤成焦特性的演化机制并提出了“衍构成焦机理”,其核心观点是:煤的焦化本质是煤分子在温度作用下发生的一系列化学反应;成焦过程中的一切宏观特性都取决于煤基体的瞬态空间结构,即“结构决定性质”;炼焦过程中传热传质条件的动态变化将影响煤的热转化行为进而影响成焦特性和焦炭质量,即“环境影响行为”。基于煤分子结构特性及热解过程中共价键的断裂和重建规律,重点分析了炼焦煤的流动性、膨胀性及其演化机制,探究了煤分子空间结构重排与焦炭强度的内在联系。流动性源于煤中弱共价键的断裂,终于芳香碎片的交联缩聚。在流动过程中,煤热解碎片以分子链段的形式向孔穴相继跃迁并封闭孔隙,形成了包含塑性层和部分煤层及半焦层的低透气带,限制了挥发分的释放从而产生了膨胀压力;同时,碳基质结构发生重排,取向性增加,sp2杂化和sp3杂化形式的碳原子的空间排布方式决定了焦炭的强度。加热速率的合理调控将明显改善焦炭强度并实现焦化过程节能降耗。“衍构成焦机理”是对传统煤成焦机理的补充和延伸,以期为现代煤焦化工业精细化发展提供理论指导和技术支撑。

     

    Abstract: Understanding the coal properties and investigating the coking mechanism is essential to develop fine coal blending coking technology. The traditional coking mechanism explains the phenomenon of thermoplastic and caking properties in the absence of a substantial understanding of chemical reactions during coking process. The evolution of coking properties is recognized at a molecule level and the “Structure Derivation Coking Mechanism” is proposed. A series of chemical reactions occur during coal coking. The macroscopic characteristics depend on the transient spatial structure of the coal matrix, that is, “the properties are determined by structure”. The regulation of heat and mass transfer conditions shows a significant influence on the coal thermal conversion and affects the coking properties and coke performances, that is “environment affects behavior”. The evolution of fluidity and swelling during coking is analyzed and the correlation between coal structural transformation and coke strength is revealed based on the coal structural properties and cleavage and reconstruction of covalent bonds. The breakage of covalent bonds with weak dissociation energy contributes to the development of fluidity while the coal matrix re-solidification is related to the cross-linking and condensation reactions. The coal pyrolysis fragments in the form of molecular chain segments migrate to the pores across the fluidity range, which contributes to the formation of a low permeability zone containing a plastic layer, coal layer and semi-coke layer. Also, the swelling pressure generates because of the restriction of volatiles’ release in the range of low permeability zone. In addition, the rearranged reaction of the carbon matrix occurs, which increases the orientation and order degree of the semi-coke microcrystalline structure. The coke strength is related to the spatial arrangement of sp2 and sp3 carbon atoms. The scientific regulation of heating rate presents a significant superiority in improving the coke strength and realizing energy conservation during the coking process. As a supplement and extension to the traditional coking mechanism, the “Structure Derivation Coking Mechanism” contributes to the theoretical guidance and technical support for the fine development of coal coking industry.

     

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