【作者】 王建斌；

【导师】 刘建忠； 程军； 何勇；

【作者基本信息】 浙江大学 ， 热能工程， 2024， 博士

【摘要】 为实现“30·60”的双碳目标,工业部门必须压缩能源消耗,加大碳减排力度,发展绿色低碳的工业循环经济。在工业循环经济中很有意义的一项工作就是变工业废弃物为原料,实现废弃物资源化和能源化利用。将危险固废与煤粉协同制备水煤浆,并在水煤浆气化炉中进行高温气化反应,使危险固废的有机成分转化为合成气等高附加值资源,是一种处置危险固废的新途径。目前,危险固废协同制备水煤浆气化技术仍处在发展的初级阶段,仍需开展大量研究以加深对危险固废水煤浆气化过程及反应机理的认识,加快工业化推广应用。基于以上背景,本文系统地研究了危险固废水煤浆的成浆特性、气化特性、熔融特性以及重金属迁移特性,分别运用热力学、计算流体力学、机器学习等理论深入探究了气化合成气组分的影响因素及规律,最终实现了危险固废水煤浆制备及气化炉上的工业应用。首先,系统地研究了废活性炭、发酵药渣以及制药污泥与煤的共成浆特性,探讨了不同危险固废与煤、添加剂的相互作用机理及添加剂的适配性,成功制备出成浆性能良好的危险固废水煤浆。研究表明,阴离子型添加剂的适配性要优于非离子型和阳离子型添加剂,且其中亚甲基双萘磺酸钠的分散效果最佳。废活性炭、发酵药渣以及制药污泥的掺混均会对水煤浆的成浆性产生不同程度的影响。其中,在15%的高固废掺混比例时,药渣煤浆的浆体浓度已降至56.32%,而污泥煤浆的浆体浓度保持在60.17%。试验还揭示了废活性炭煤浆、药渣煤浆和污泥煤浆的假塑性流体特征,此外危险固废水煤浆的静置稳定性也有所增强。其次,先后开展了危险固废水煤浆在不同氧化剂氛围下的气化反应试验,研究原料理化性质和气化温度对浆料气化的协同作用与影响机制,并从碱金属及碱土金属（AAEMs）催化作用和碳结构演变角度探究了危险固废水煤浆的气化反应机理。研究发现,提高气化温度有助于废活性炭煤浆焦总产气量的增加,而热解温度则对其产生相反的影响。在相同的气化温度下,400℃热解焦和500℃热解焦的H₂产量始终高于其它热解焦。分析气化反应机理发现,400℃热解焦和500℃热解焦中的AAEMs表现出较强的气化催化性,且500℃热解焦的无序度和碳活性达到了最高水平。其无序的碳晶格增加了微晶结构的缺陷,使得碳分子与水蒸气分子的接触更为充分,从而展现出了最佳的气化反应性。随后,探讨了危险固废水煤浆气化反应过程的熔融特性与气化残渣中重金属的浸出行为,结合矿物学和化学形态解释了气化残渣中的重金属分布特征。研究表明,在废活性炭煤浆灰渣中,低熔点矿物占据了显著的比例,这有利于气流床气化炉实现液态排渣。在重金属的化学形态分布上,当废活性炭与水煤浆进行共气化反应后,所得气化残渣的重金属元素中残留态的比例有所上升,这意味着重金属元素在环境中的稳定性得到了增强。此外,本文采用了风险评价指数（RAC）值来分析气化残渣中重金属对环境的潜在风险,发现废活性炭煤浆气化残渣中的重金属元素对环境不构成高风险或极高风险。接着,分别运用了热力学、计算流体力学以及机器学习等理论,对危险固废水煤浆气化进行数值计算与数学建模研究。研究发现,废活性炭煤浆的气化有效气产率要明显高于药渣煤浆和污泥煤浆。气化炉内的气相浓度场与温度场之间存在密切的耦合关系,在火焰高温区域主要分布着燃烧产物H₂O和CO₂,而在低温区域气化产物CO和H₂显著增加。探讨操作参数对气化过程的影响时,发现增加氧浆比会加剧燃烧反应,降低有效气的产率。同时,调整中心氧的分配比例会改变火焰的形态和位置,影响炉内温度分布。而浆体固相浓度的增加则会提高气化温度,提高气化有效气的产率。此外,针对危险固废水煤浆气化的有效气产量进行建模分析,发现CNN-LSTM模型预测性能最佳,SVR模型次之,随后是LSTM模型,ARIMA模型则最差。说明将CNN与LSTM模型相结合,优化提取多变量时间序列的空间特征,可以提高时间序列模型对有效气产量的预测精度。最后,开展了水煤浆气化协同处置多源危险固废的工业化应用试验,验证了危险固废水煤浆在实际工程中制备和气化的效果。研究表明,固废水煤浆气化的有效气占比相较于纯水煤浆有所下降,冷煤气效率和碳转化率也分别降低了0.84%和0.52%。尽管如此,不同时间工况下的合成气组成接近,且平均残渣热灼减率低至3.14%,这证明了固废水煤浆在气流床气化炉中能够进行稳定的气化反应。固废水煤浆气化残渣的重金属浸出浓度低于危险废物鉴别标准中的浸出限值,表明危险固废与水煤浆共气化后的气化残渣属于一般固体废物,水煤浆气化工艺实现了对危险固废的无害化处置。更多还原

【Abstract】 In order to realize the carbon peaking and carbon neutrality goals,the industrial sector must compress energy consumption,increase carbon emission reduction,and develop a green,low-carbon industrial circular economy.A significant task in the industrial circular economy is to turn industrial waste into raw materials and realize the resourcefulness and energy utilization of waste.The synergistic preparation of coal-water slurry from hazardous solid waste and coal and the high-temperature gasification reaction in the coal-water slurry gasifier,which converts the organic components of hazardous solid waste into high-value-added resources such as syngas,is a new way to dispose of hazardous solid waste.Currently,coal-water slurry gasification technology for recycling hazardous solid waste remains in its initial stages of development.Further studies are necessary to enhance comprehension of the gasification process and reaction mechanisms involved with coal-water slurry containing hazardous solid waste,thereby expediting its industrialization and widespread application.Based on the background provided,this study systematically investigates slurry formation,gasification,melting processes,and the migration of heavy metals in coal-water slurry containing hazardous solid waste.Thermodynamics,computational fluid dynamics,and machine learning theories were used to investigate the influencing factors and laws of gasification syngas components.Finally,the preparation of coal-water slurry containing hazardous solid waste and its industrial application on gasifier were realized.Firstly,the co-slurrying characteristics of waste activated carbon,bioferment residue of drugs,and pharmaceutical manufacturing sludge with coal were systematically studied.The interaction mechanism of different hazardous solid wastes with coal and additives,as well as the suitability of the additives,were investigated so that coal-water slurry containing hazardous solid waste with good slurrying performance was successfully prepared.The study shows that the suitability of anionic additives is better than that of nonionic and cationic additives,and the dispersing effect of sodium methylene bis-naphthalene sulfonate is the best.The blending of waste activated carbon,bioferment residue of drugs,and pharmaceutical manufacturing sludge can affect the slurrying ability of coal-water slurry to different degrees.In particular,at a high solid waste blending ratio of 15%,the maximum solid concentration of the coal-bioferment residue of drugs-slurry had decreased to 56.32%,while the maximum solid concentration of the coal-pharmaceutical manufacturing sludge-slurry remained at 60.17%.The experiments also revealed the pseudoplastic fluid characteristics of coal-waste activated carbon-slurry,the coal-bioferment residue of drugs-slurry and coal-pharmaceutical manufacturing sludge-slurry,in addition to the enhanced static stability of coal-water slurries containing hazardous solid wastes.Experiments were conducted to investigate the gasification reaction of coal-water slurry containing hazardous solid waste under various oxidant atmospheres.This study also examined the synergistic effect and influence mechanism of physical-chemical properties and gasification temperature on the gasification of the slurry.The gasification reaction mechanism of coal-water slurry with hazardous solid waste was also investigated from the viewpoints of the catalytic effect of alkali and alkaline earth metals（AAEMs）and the evolution of carbon structure.It was found that increasing the gasification temperature contributed to the increase in the total gas production of coal-waste activated carbon-slurry coke.In contrast,the pyrolysis temperature had the opposite effect.At the same gasification temperature,the H₂ yields were consistently higher than those of other pyrolysis coke.The analysis of the gasification reaction mechanism revealed that the AAEMs in pyrolysis coke at 400℃and 500℃exhibited strong gasification catalytic properties,and the disorder and carbon activity of pyrolysis coke at 500℃reached the highest level.Its disordered carbon lattice increased the defects in the microcrystalline structure,which made the carbon molecules come into contact with water vapor molecules more adequately,thus exhibiting the best gasification reactivity.Subsequently,the melting characteristics of the gasification reaction process of coal-water slurry containing hazardous solid waste and the leaching behavior of heavy metals in the gasification residue were discussed.The distribution characteristics of heavy metals in the gasification residue were explained by combining mineralogy and chemical morphology.Low melting point minerals occupy a considerable proportion of the gasification residue of coal-waste activated carbon-slurry,which is conducive to realizing liquid slag discharge in the gasifier.In terms of the geochemical distribution of heavy metals,when the co-gasification between waste activated carbon and coal-water slurry was carried out,the proportion of heavy metal elements in the residual state of the gasification residue increased,which implied that the stability of heavy metal elements in the environment was enhanced.In addition,this paper used the risk assessment code（RAC）to analyze the potential risk of heavy metals in the gasification residue to the environment,and it was found that the heavy metal elements in the gasification residue of coal-waste activated carbon-slurry did not pose a high or very high risk to the environment.Subsequently,thermodynamics,computational fluid dynamics,and machine learning theories were applied to numerically calculate and mathematically model the gasification process of coal-water slurry containing hazardous solid waste.It was found that the effective gas yield of gasification of coal-waste activated carbon-slurry was significantly higher than that of the coal-bioferment residue of drugs-slurry and coal-pharmaceutical manufacturing sludge-slurry.There is a close coupling between the gas-phase concentration field and the temperature field in the gasifier,and the combustion products H₂O and CO₂ are mainly distributed in the high-temperature region of the flame.In contrast,the gasification products CO and H₂ increase significantly in the low-temperature region.When exploring the effects of operating parameters on the gasification process,it was found that increasing the oxygen-slurry ratio would intensify the combustion reaction and reduce the effective gas yield.Meanwhile,adjusting the oxygen percentage of the inner ring would change the shape and position of the flame and affect the temperature distribution in the furnace.An increase in the solid concentration of the slurry will increase the gasification temperature and the effective gas yield of gasification.In addition,modeling analysis for the effective gas yield of gasification of coal-water slurry containing hazardous solid waste reveals that the CNN-LSTM model has the best prediction performance,followed by the SVR model.The LSTM model and the ARIMA model are the worst.It shows that combining CNN and LSTM models to extract the spatial features of multivariate time series optimally can improve the prediction accuracy of time series models for effective gas production.Finally,an industrial application test of coal-water slurry gasification for the co-processing of multi-source hazardous solid waste was carried out to verify the effectiveness of the gasification of coal-water slurry containing hazardous solid waste.It was shown that the effective gas percentage of gasification of coal-water slurry containing hazardous solid waste decreased compared with that of pure coal-water slurry,and the cold gas efficiency and carbon conversion ratio also decreased by 0.84%and 0.52%,respectively.Nevertheless,the syngas compositions at different time conditions were close to each other,and the average loss on ignition of gasification residue was as low as 3.14%,which proved that the coal-water slurry containing hazardous solid waste was able to carry out a stable gasification reaction in the gasifier.The heavy metal leaching concentration of the gasification residue of coal-water slurry containing hazardous solid waste was lower than the leaching limit in the hazardous waste identification standard.It indicates that the gasification residue after the co-gasification of hazardous solid waste and coal-water slurry belongs to the general solid waste,showing that the coal-water slurry gasification process has achieved the harmless disposal of hazardous solid waste.更多还原