【作者】 李俊国；

【导师】 张光华；

【作者基本信息】 陕西科技大学 ， 应用化学， 2014， 博士

【摘要】 近年来，随着世界石油资源的日益紧缺和石油价格的不断攀升，煤炭资源的综合利用越来越受到人们的关注，然而煤炭的直接燃烧利用却导致了较低的利用效率及严重的气候恶化和环境污染，水煤浆作为一种煤基“节能减排”流体清洁燃料应运而生。水煤浆是煤在水中的粗颗粒分散体系。煤是疏水性物质，水煤浆中的煤粒由于相互之间的疏水作用而易于团聚和沉淀。理想的水煤浆应该在其制备、储存过程中具有较好的稳定性，而在其管道运送和雾化燃烧过程中具有较低的黏度，为了实现这个目的，分散剂的选择使用具有非常重要的意义。目前，用于水煤浆的分散剂主要有萘系、木质素系、腐殖酸系、聚烯烃系、聚羧酸盐系、磺化丙酮甲醛缩合物和非离子分散剂等。然而，这些分散剂中的大多数是以石油产品为原料的，不仅价格较高，而且容易产生环境污染。腐殖酸系分散剂由天然产物腐殖酸经改性而制得，具有原料易得、绿色环保、价格低廉、分散性好等优点。然而，由于目前的研究工作仅限于对腐殖酸的硝化、磺化、磺甲基化等初级改性方面，这虽然提高了腐殖酸系分散剂的亲水性和分散性，但由于分散剂相对分子质量依然较小，从而使该类分散剂存在稳定性差的问题。本论文通过分散剂分子结构设计，采用接枝共聚和缩合反应两种方法对腐殖酸进行化学改性以合成水煤浆分散剂。首先，以腐殖酸（HA）、烯丙基磺酸钠（SAS）、丙烯酸（AA）、丙烯酰胺（AM）、烯丙醇聚氧乙烯醚（APEG,相对分子质量分别为700,1000,1200,2400）、甲基丙烯酰氧乙基三甲基氯化铵（DMC）等为原料，以过硫酸钾为引发剂，采用水溶液自由基共聚合原理并通过工艺条件优化，合成了七种新型腐殖酸接枝共聚物水煤浆分散剂，即三种二元接枝共聚物——HA-SAS（HAS）、HA-AA（HAA）及HA-AM（HAM）；两种三元接枝共聚物——HA-SAS-APEG1000（HSP1000）及HA-AA-APEG1200（HAP1200）；两种两性离子型接枝共聚物——HA-SAS-DMC（HSD）及HA-AA-DMC（HAD）。其次，以腐殖酸、甲醛、尿素、亚硫酸钠等为原料，利用磺甲基化及缩合反应合成了两种腐殖酸缩合物分散剂——磺化腐殖酸甲醛缩合物（SHF）和磺化腐殖酸脲醛缩合物（SHUF），并对其合成工艺条件进行了优化。采用FT-IR、GPC、TG及DSC对九种新型腐殖酸基分散剂进行了结构表征和性能测试。以神木煤、沟口煤、彬长煤及霍林河煤为实验用煤，研究了所合成的分散剂对水煤浆分散性和稳定性的影响，探讨了分散剂分子化学结构与水煤浆应用性能之间的相关性。结果表明，各种新型腐殖酸基分散剂的分散及稳定性均优于传统的萘磺酸盐甲醛缩合物（NSF）分散剂。对于接枝共聚物分散剂，适量磺酸基的引入有利于分散剂应用性能的改善，而适量具有一定链长的聚氧乙烯醚及季胺基阳离子基团的引入可进一步提高煤浆的应用性能。此外，利用尿素进行共缩合因可有效改善缩合物分散剂分子链的柔顺性而有利于分散剂应用性能的改善。以分散和稳定性能良好而又化学结构不同的HSP1000及HSD分散剂制取神木煤水煤浆（煤浓度为66wt%，分散剂加量为0.5wt%）并研究了其流变学行为。结果表明，HSP1000及HSD水煤浆的表观黏度均随剪切速率的增大显著下降，表现出明显的剪切变稀的假塑性流体特征。以Power-law模型、Bingham模型及Herschel-Bulkley模型对浆体的剪切应力/剪切速率关系进行了拟合，结果表明，HSP1000及HSD水煤浆的流变学行为在Herschel-Bulkley模型下吻合度最高，其拟合相关系数R2分别为0.9857和0.9988。在该模型下，HSD水煤浆的流动特性指数n较HSP1000水煤浆小，表明其具有更为明显的假塑性流体特征。研究了九种新型腐殖酸基分散剂在神木煤表面的吸附量、分散剂溶液在煤表面的接触角以及分散剂复合煤粒表面的Zeta电位。结果表明，缩合物分散剂、二元接枝共聚物分散剂及三元接枝共聚物分散剂在神木煤表面的吸附行为均符合Langmuir等温吸附方程，而两性离子型接枝共聚物分散剂服从Freundlich等温吸附方程。两性离子型分散剂具有最大的吸附量，这与其分子中的阳离子基团与煤表面的阴离子基团形成的较强静电引力及其在煤表面易于形成多层吸附有关。所合成的分散剂均能有效降低煤/水界面的接触角，接触角的大小与分散剂分子在煤表面形成的定向排列的紧密程度、分子中亲水基团的亲水性强弱及其数量有关。九种新型分散剂均能有效提高煤粒表面的Zeta电位绝对值，Zeta电位绝对值的高低不仅取决于分散剂分子结构中阴离子基团的种类及其含量，也与分散剂分子链的柔顺性有关。通过SEM对原煤粉和HSD分散剂复合煤粉进行了表面形貌观察，并对分散剂复合煤粉的比表面和孔隙度进行了研究。依据上述测试及分析结果，阐述了不同种类的腐殖酸基分散剂与煤之间的作用机理。总之，本论文对腐殖酸基水煤浆分散剂的合成、表征、性能及其与煤之间的作用机理进行了一系列基础性研究，合成了一系列高性能的分散剂，探索了分散剂分子化学结构与水煤浆性能之间的关系，揭示了分散剂分子与煤之间的作用机理，对水煤浆分散剂的分子结构设计及合成具有一定的理论和实践参考价值。更多还原

【Abstract】 In recent years, with the increasing shortage of petroleum resources andrising price of oil in the world, the comprehensive utilization of coal resources ismore and more interested. However, the direct combustion utilization of coal hasresulted in low efficiency, serious climate deterioration and environmentalpollution. The coal-water slurry (CWS), as a clean coal-based liquid fuel forenergy conservation and emission reduction, has emerged as the times require.The CWS is a suspension system of the coarse coal particles in water. Coalis hydrophobic substance, due to hydrophobic interaction, the coal particles inCWS are apt to agglomerate mutually and precipitate. The ideal CWS shouldhave good stability during its manufacture and storage, meantime have a lowviscosity in the process of its pipeline transportation and atomization. To achievethis, the selection of a dispersant plays a very important role.At present, the dispersants for CWS include naphthalene series, lignin series,humic acid series, polyolefin series, polycarboxylate series, sulfonatedacetone-formaldehyde and non-ionic dispersing agents etc.. However, most ofthe dispersants are synthesized using petroleum products as raw materials, andnot only have high prices, but also are very harmful to environment. The humicseries dispersants are obtained by modifying natural humic acid, and the rawmaterial for their syntheses are readily available, while they areenvironment-friendly, and have cheap prices and good dispersion properties.Whereas, the current research works on humic acid series dispersants are limitedto the primary modifications of humic acid, such as nitration, sulfonation,sulfomethylation etc.. Despite the modifications will help to improve thehydrophilicity and dispersion performance of humic acid, owing to relativelysmall molecular mass, the dispersants exhibit poor stability. The thesis adopts the graft copolymerization and condensation reactions tomodify humic acid for the syntheses of CWS dispersants by dispersant molecularstructure design. Firstly, using humic acid (HA), allylsulfonate (SAS), acrylicacid (AA), acrylamide (AM), allyl alcohol polyoxyethylene ether (APEG,relatively molecular mass is700,1000,1200and2400, respectively) andmethacryloyloxyethyl trimethyl ammonium chloride (DMC) as raw materials,persulfate as initiator, the seven new-style humic acid graft copolymerdispersants have been synthesized, namely, three binary graftcopolymers—HA-SAS (HAS), HA-AA (HAA) and HA-AM (HAM); twotribasic graft copolymers—HA-SAS-APEG1000(HSP1000) and HA-AA-APEG1200(HAP1200); two zwitterionic graft copolymers—HA-SAS-DMC (HSD)and HA-AA-DMC (HAD). Secondly, using humic acid, formaldehyde, urea andsodium sulfite as raw materials, two humic acid condensate dispersingagents—sulfonated humic acid-formaldehyde (SHF) and sulfonated humic acid-urea-formaldehyde (SHUF) have been synthesized by sulfomethylation andcondensation reactions, and the synthesis conditions are optimized. EmployingFT-IR, GPC, TG and DSC, the chemical structures of the nine dispersants arecharacterizated and their performances are also examined. Using Shenmu coal,Goukou coal, Binchang coal and Huolinhe coal as experimental coals, the effectsof the nine dispersants synthesized on the dispersion properties and stabilities ofthe CWSs are investigated, and the relationships between dispersant chemicalstructures and CWS capabilities are also discussed. The experimental resultsshow that the dispersion properties and stabilities of the CWSs prepared from thenine new-style dispersants synthesized are superior to those of the CWSs froman industrialized naphthalene sulfonate formaldehyde condensate (NSF)dispersant. As for a graft copolymer dispersant, the certain amount of sulfonicacid groups introduced in the dispersant molecule could improve the applicationproperties of the dispersant. While the moderate polyoxyethylene chains withspecific length and the quaternary amine cationic groups introduced in the abovemolecule could strengthen further the properties of the dispersant. In addition,the urea introduced in the condensate dispersant molecule may make themolecular chain become flexible, which is helpful to the application properties ofthe dispersant. The Shenmu CWSs (coal mass concentration=66wt%and dispersantdosage=0.5wt%) are prepared from HSP1000and HSD with relatively exellentdispersion properties and stabilities, and the rheological behaviors of the CWSshave been examined. The experimental results show that the apparent viscositiesof the CWSs prepared from HSP1000and HSD decrease significantly with anincrease of shear rate, and the CWSs exhibit pseudoplastic shear-thinning fluidcharacteristics. The relationships between shear stresses and shear rates of theCWSs are fitted by the Power-law model, Bingham model and Herschel-Bulkleymodel. The results show that the Herschel-Bulkley model has the highestmatching degree, and the correlation coefficient R2is0.9857and0.9988,respectively. With the model, the flow behavior index n of the CWS from HSDis smaller than that from HSP1000, which shows the CWS from HSD has moreevident pseudoplastic fluid characteristics.The adsorption amounts of the dispersants synthesized on Shenmu coalsurfaces, contact angles of the dispersant solutions on the coal surface and zetapotentials of the complex coal particle surface with adsorbed dispersantmolecules, are all investigated. The results show that the adsorption behaviors ofthe condensate dispersants, binary graft copolymer dispersants and tribasic graftcopolymer dispersants, are all according to the Langmuir isotherm equation, andthose of the zwitterionic graft copolymer dispersants are in line with theFreundlich model. The zwitterionic dispersants have the highest adsorptionamounts, which could be related not only to forceful electrostatic interactionbetween the cationic groups in the dispersant molecules and anionic groups ofcoal surface, but also to their multilayer adsorptions on the surface. Thedispersants synthesized could all diminish effectively the contact angles atcoal-water interface, which relies not only on the orientation tightness extent ofthe dispersant molecules adsorbed on the coal surface, but also on the numberand hydrophilic ability of the hydrophilic functional groups in dispersantmolecule. The nine new-style dispersants synthesized may all raise markedly thezeta potential absolute values of coal particle surfaces, which relates to the typeand number of the anionic groups in dispersant molecule, as well as theflexibility of the dispersant molecule. The surface morphology of the raw coalparticles and complex coal particles adsorbing HSD molecules is observed by SEM, while the specific surface and porosity of the complex coal particles is alsoinvestigated. Based on the above test results, the action mechanisms between thedispersants synthesized and coal have been described further.In summary, this thesis has studied the syntheses, characterizations,capabilities and action mechanisms of the humic acid-based dispersants for CWS,and a series of high-performance dispersants have been obtained. Therelationships between dispersant chemical structures and CWS capabilities havebeen explored, and the action mechanisms between the dispersants synthesizedand coal have also been disclosed. Therefore, the thesis is of theoretical andpractical significance in research on the molecular structure design and synthesisof a dispersant for CWS.更多还原