表面活性剂对褐煤润湿性反转调控机制及水分回吸抑制研究

Strong water absorption due to lignite surface oxygen-containing functional groups hydrophily is the main reason resulting in dried lignite moisture re-adsorbed quickly. The unique chemical structure of surfactant with hydrophilic and hydrophobic groups and the impact of surfactant hydrophilic hydrophilic end on lignite surface carboxyl and hydroxyl polar groups have profound effects on lignite surface wettability changes, which could bring lignite surface wettability alteration from hydrophilicity to hydrophobicity and restrain dried lignite moisture re-adsorption. The key objective of this research project is alteration regulation mechanism of lignite surface wettability with surfactants. For this goal, a comprehensive understanding of the effects factors, such as different type surfactants and their structure characteristics, and oxygen-containing functional groups and their contents, and pore characteristics of lignite and modified methods on adsorption characteristics of lignite surfaces with surfactants is desirable. The wettability alteration mechanism will be explored with a view obtaining an insight into the influence of surfactant adsorption characteristics on lignite surface. The critical condition confirmation of wettability alteration from hydrophilicity to hydrophobicity is necessary, and then main influencing factors and alteration regulation ways impacting on the degree of wettability change would be discovered. The alteration regulation mechanism of lignite wettability with surfactants as well as the effects of lignite surface wettability alteration on the dried lignite moisture re-adsorption could be fully clarified. The theory and control method of dried lignite moisture re-adsorption based on lignite surface wettability alteration regulation would be available. The project is of technological base to solve dried lignite moisture re-adsorption problem.

褐煤表面亲水含氧基团对水分的强吸附性是导致褐煤干燥后水分迅速回吸的主要原因。具有亲、疏水基团表面活性剂通过亲水端作用于褐煤表面的羧基和羟基等极性亲水基团能够改变其表面润湿性，带来褐煤表面润湿性由亲水性向疏水性的反转，润湿性反转会抑制干燥后褐煤水分回吸。本课题围绕表面活性剂对褐煤润湿性反转调控机制核心研究目标，研究表面活性剂类型和结构特征、褐煤含氧基团类型和含量、褐煤孔隙结构以及褐煤表面改性处理方法对表面活性剂在褐煤固体颗粒表面吸附性能的影响；揭示表面活性剂在褐煤表面吸附特征对褐煤润湿性反转作用机理；确定褐煤表面润湿性由亲水性向疏水性反转临界条件，发现影响褐煤润湿性转变程度的主要因素和调控方法；阐明褐煤表面润湿性反转调控机制以及褐煤表面润湿性反转调控对干燥后褐煤水分回吸性影响，建立基于褐煤表面润湿性反转调控机制来抑制干燥后褐煤水分回吸的理论和方法，为解决干燥后褐煤水分回吸难题奠定技术基础。

褐煤表面亲水含氧基团对水分的强吸附性是导致褐煤干燥后水分迅速回吸的主要原因。具有亲、疏水基团的表面活性剂通过定向的吸附改变褐煤表面的自由能，带来褐煤表面润湿性由亲水性向疏水性反转，褐煤表面润湿性的反转会抑制水分的回吸。本项目主要围绕表面活性剂在褐煤表面的吸附特征、吸附层结构及其对褐煤表面润湿性反转作用的影响程度为核心研究目标，系统地研究和阐明了离子类和非离子类表面活性剂以及表面活性剂的亲水基团结构、疏水端的碳链长度、煤中含氧官能团类型及含量变化、吸附的液相环境对表面活性剂在褐煤表面微观吸附行为、吸附性能影响和界面作用机理，阐明了表面活性剂吸附对褐煤表面润湿性影响规律，发现了影响降低褐煤表面亲水性的关键性因素，通过研究褐煤孔隙结构、粒级变化以及煤中矿物质组分对表面活性剂吸附及其对褐煤表面润湿性的影响，总结了煤中矿物质组分、煤粒级变化和孔隙结构对褐煤润湿性影响规律。采用分子动力学方法建立了水-表面活性剂-褐煤三元模拟体系，研究了离子类表面活性剂和两种具有相同疏水烷烃链、不同亲水头基的非离子表面活性剂在褐煤表面吸附及其对褐煤表面润湿性反转的微观机理，分析了表面活性剂在煤/水界面的吸附作用力和吸附形态及其对褐煤润湿性的影响。通过表面活性剂吸附处理后褐煤的水分回吸性的影响研究，阐明和发现抑制褐煤水分回吸的主要影响因素，为基于褐煤表面润湿性反转调控机制来抑制干燥后褐煤水分回吸方法的建立提供了理论指导。