【作者】 李强；

【导师】 张文军；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2025， 博士

【摘要】 煤气化粗渣是煤气化后所产生的固体废弃物,其中含有的残炭具有一定热值和石墨化程度,可以回收后作为燃料或者制备碳材料。经过湿法分选获得的富碳煤气化粗渣孔隙结构发达、表面亲水含氧官能团丰富,导致其含水率高且用常规脱水方式难以有效脱除,严重制约其后续的处置和资源化利用。针对该难题,提出并开展了基于磨碎协同疏水改性强化富碳煤气化粗渣的脱水提质机制研究。查明了富碳煤气化粗渣的持水机制,探究了磨碎过程中孔隙结构与水分之间的定量关系;揭示了磨碎协同疏水改性过程中改性剂对磨碎富碳渣脱水效果的影响及疏水改性机制;明确了磨碎协同疏水改性过程中磨碎改性渣的聚集与分散特性及其影响;奠定了基于磨碎协同疏水改性的富碳煤气化粗渣分级脱水提质工艺理论依据;多维度评价了该工艺的综合提质效果。探明了富碳煤气化粗渣的持水机制及磨碎富碳渣孔隙结构与水分的定量关系。富碳煤气化粗渣的孔隙水含量高,无机组分与表面亲水官能增加了其表面亲水性。针对富碳煤气化粗渣大孔、中孔持水量高并且难以脱除的问题,通过磨碎破孔可将孔隙水释放为易于脱除的自由水。磨碎富碳渣比表面积随粒度的减小而增大,表面吸附水含量增加。当磨碎粒度D₉₈为139μm时达到“释-吸”平衡点,吸附水的增加量与自由水及孔隙水的脱除量差值最大,此时水分达到最小值39.18%。分形维数的定量分析表明,随着磨碎粒度降低,与孔隙粗糙度相关的分形维数D₁和与孔隙连通性相关的D₂先降低后增加,D₁和D₂的降低有利于水的脱除。磨碎过程降低了富碳渣大孔、中孔的水分,虽然对脱水有一定的促进作用,但是由于粒度降低导致吸附水含量增加,仍然难以高效脱水。探究了磨碎协同疏水改性过程对富碳渣脱水效果的影响及改性剂的作用机制。磨碎协同疏水改性可以促进改性剂的高效分散及其与磨碎富碳渣的优先吸附。孔隙水的赋存状态分析表明,磨碎协同疏水改性过程中改性剂对新生微孔具有优先吸附及疏水改性作用;磨碎富碳渣的新生表面能高、亲水性强,表面活性剂降低了水的表面张力,但无法有效降低表面亲水性;相比于非极性油,餐厨废油中的含氧官能团与磨碎富碳渣表面极性组分间的氢键或离子键合作用增强了其在磨碎富碳渣表面的亲和力,可以使富碳渣表面的C-C/C-H含量增加至74%以上;富碳渣脱水产品的水分随着改性剂用量增加呈先降低后增加的趋势,相比于非极性油,餐厨废油改性可以将富碳渣水分降低10%以上;磨碎富碳渣中的C-C/C-H、COOH官能团的含量是影响脱水性能的关键因素。研究了磨碎改性渣颗粒的聚集与分散特性对脱水提质的影响。通过PVM观察到磨碎改性渣聚集体粒度达到100μm以上,表明经过疏水改性的磨碎富碳渣中微细颗粒发生了疏水团聚。磨碎改性渣的水分随团聚体分形维数的增加而降低,在最佳脱水状态下分形维数为1.93。改性剂用量过高会使得团聚体的结构松散,表面的油膜包裹水难以脱除,因而导致脱水产品水分增加。随着剪切速率增加,疏水团聚体的分形维数增大,有利于水分脱除,但是团聚体粒度随之降低;由于磨碎过程存在解离效应,解离出来的微细残炭颗粒在疏水作用下形成粒度较大的团聚体,在筛分脱水过程中成为筛上产品;而解离出来的微细灰颗粒则依然呈分散态,在筛分脱水过程中进入筛下水,即在实现磨碎改性渣筛分脱水的同时,还有效降低了其灰分。建立了基于磨碎协同疏水改性的富碳煤气化粗渣高频细筛脱水降灰工艺。通过高频细筛对磨碎疏水改性并选择性团聚后的磨碎改性渣进行处理,既可降低富碳渣的水分,还可降低灰分,并具有一定的防复吸效果。实验表明:水分为49.63%、灰分为29.81%、粒度为+0.25 mm的富碳煤气化粗渣,经磨碎协同疏水改性再进行高频细筛脱水后的筛上产品水分为18.36%、灰分为18.76%、回收率为76.39%,水的复吸量仅为3%左右。该论文有图88幅,表20个,参考文献218篇。更多还原

【Abstract】 Coal gasification coarse slag is the solid waste generated after coal gasification.The residual carbon contained in it has a certain calorific value and graphitization degree,which can be recycled as fuel or carbon material.The carbon rich coal gasification coarse slag obtained by wet separation has developed pore structure and rich surface hydrophilic and oxygen-containing functional groups,resulting in high moisture and difficult to effectively remove by conventional dewatering methods,which seriously restricts its subsequent disposal and resource utilization.To solve the problem,the upgrading mechanism of coarse carbon rich coal gasification slag enhanced by size reduction synergistic hydrophobic modification was proposed and carried out.The water holding mechanism of coarse carbon rich coal gasification slag was found out,and the quantitative relationship between pore structure and water content in the size reduction process was explored.The influence of modifier on dewatering effect of grinding carbon rich slag and hydrophobic modification mechanism in the process of size reduction synergistic hydrophobic modification were revealed.The aggregation and dispersion characteristics and their effects of grinding modified slag in the process of size reduction synergistic hydrophobic modification were clarified.The theoretical basis of grading dewatering and upgrading process of coarse carbon rich coal gasification slag based on size reduction synergistic hydrophobic modification was established.The comprehensive upgrading effect of the process was evaluated from multiple dimensions.The water holding mechanism of coarse carbon rich coal gasification slag and the quantitative relationship between pore structure and water content of grinding carbon rich slag were explored.The pore water content of coarse carbon rich coal gasification slag is high,and the inorganic components and surface hydrophilic function increase its surface hydrophilicity.In view of the high-water holding capacity of macropores and mesopores of coarse carbon rich coal gasification slag and the difficulty of removal,the pore water can be released into free water by size reduction and destroying the pore structure.The specific surface area increased with the decrease of particle size,and the surface adsorbed water content increased.When the grinding particle size D₉₈ is 139μm,the"release-absorption"equilibrium point is reached,and the difference between the increase of adsorbed water and the removal of free water and pore water is the largest,the water content reaches the minimum value of 39.18%and the moisture reaches the minimum.The quantitative analysis of fractal dimension shows that with the decrease of particle size,the fractal dimension D₁ related to pore roughness and D₂related to pore connectivity first decreases and then increases,and the reduction of D₁and D₂ is conducive to the removal of water.During the size reduction process,the water content of macropores and mesopores decreases.Although there is a certain promotion effect on dewatering,it is still difficult to significantly reduce the moisture due to the increase in adsorbed water content caused by the decrease in particle size.The influence of size reduction synergistic hydrophobic modification process on the dewatering effect of carbon rich slag and the mechanism of modifier were explored.Size reduction synergistic hydrophobic modification can promote the efficient dispersion of modifier and the preferential adsorption with grinding carbon rich slag.The analysis of the occurrence state of pore water showed that the modifier had preferential adsorption and hydrophobic modification effect on the new micropores in the process of size reduction synergistic hydrophobic modification.The nascent surface energy of the grinding carbon rich slag is high and hydrophilic,and the surfactant reduces the surface tension of the water but is not effective in reducing surface hydrophilicity.Compared with non-polar oil,the hydrogen bond or ionic bond between oxygen-containing functional groups in kitchen waste oil and polar components on the surface of grinding carbon rich slag enhances its affinity on the surface of grinding carbon rich slag,and can increase the C-C/C-H content to more than 74%.With the increase of modifier dosage,the moisture of grinding carbon rich slag dewatering products decreased first and then increased.Compared with non-polar oil,the water content of grinding carbon rich slag dewatering products decreased by more than 10%after modified by waste cooking oil.The content of C-C/C-H and COOH functional groups in the grinding carbon rich slag is the key factor affecting the dewatering performance.The effect of aggregation and dispersion characteristics of grinding modified slag particles on upgrading was investigated.It was observed by PVM that the particle size of aggregates of grinding modified slag reached more than 100μm,indicating that hydrophobic agglomeration occurred in the microfine particles of the hydrophobically modified grinding carbon-rich slag.The water content of the grinding modified slag decreases with the increase of the fractal dimension of the aggregate.Under the optimal dewatering condition,the fractal dimension is 1.93.The excessive amount of modifier will make the structure of the aggregate loose,and the water wrapped in the oil film on the surface is difficult to remove,resulting in the increase of moisture in the dewatering product.With the increase of shear rate,the fractal dimension increases,which is conducive to water removal,but the particle size of aggregates decreases.Due to the dissociation effect in the size reduction process,the dissociated fine carbon slag particles,due to their strong hydrophobicity,form larger aggregates under the action of hydrophobicity,and become products on the screen in the screening dewatering process.The dissociated fine ash particles are still dispersed due to their strong hydrophilicity,and enter the under-sieve water during the screening dewatering process,that is,the ash content of the grinding modified slag is effectively reduced while the screening dewatering is realized.An upgrading process of coarse carbon rich coal gasification slag based on size reduction synergistic hydrophobic modification was established.The coarse carbon rich coal gasification slag after size reduction synergistic hydrophobic modification and selective granulation is treated by high-frequency fine sieve,which can not only reduce the moisture of carbon rich slag,but also reduce the ash content,and has a significant effect of preventing re-absorption.The experimental results show that:the moisture content of the coarse carbon rich coal gasification slag is 49.63%,the ash content is29.81%,and the particle size is more than 0.25 mm,after size reduction synergistic hydrophobic modification and high-frequency screen classification,the moisture of the product on the screen is 18.36%,the ash content is 18.76%,the recovery rate is 76.39%,and the moisture re-absorption is only about 3%.The thesis has 88 figures,20 tables and 218 references.更多还原