【作者】 刘豪；

【导师】 邱建荣；

【作者基本信息】 华中科技大学 ， 热能工程， 2006， 博士

【摘要】 煤炭是我国最主要的能源,煤燃烧除向大气排放大量的气态污染物外,还生成许多难以处理的固体废弃物-灰渣,造成严重的大气和水土污染。本文将燃烧、污染物形成和控制以及无机成分的高效利用有机关联起来,借鉴燃烧学、矿物学、硅酸盐物理化学、环境科学、材料科学等相关交叉学科知识,采用先进的测试方法对不同复合添加剂在燃煤脱硫过程中的化学反应过程尤其是无机成分的迁移和化学反应机理进行了系统和深入的研究。重点考察了煤中掺入添加剂前后硫氧化物的排放特性及固体产物的矿物组成和利用价值,探讨了不同复合添加剂的固硫机理及固硫产物的分解转化规律,特别是对煤中掺入添加剂后无机组分的多相反应机理以及反应的热、动力学特征进行了深入的研究。在无机组分的多相反应机理方面,利用高温反应器、沉降炉、单火嘴燃烧试验台等试验设备对煤粉、煤灰、添加剂以及模拟纯矿物试剂分别进行混合燃(煅)烧,并采用XRD、FESEM对不同条件下燃(煅)烧后得到的固体产物的矿物组成、微观形貌进行测定,分析了添加剂的组成和加入量、温度、颗粒细度、时间、燃烧方式及接触程度、CaO含量以及矿化剂等因素对煤与添加剂体系中无机组分的多相反应过程及反应产物组成的影响规律。在试验研究的基础上,根据多相平衡原理建立了复杂矿物质体系CaO-SiO2-Al2O3-Fe2O3-CaSO4的产物组成计算模型并进行了模拟计算,探讨了煤中无机组分与复合添加剂的多相反应机理,预测了不同条件下煤中掺入添加剂后灰渣的矿物组成,并根据矿物的种类、含量及水化特性分析了改性灰渣的活性和可利用性。在燃煤固硫与固硫灰渣的物相表征方面,利用高温电阻炉、滴管炉对高硫煤中掺入不同添加剂后在800～1400℃的温度范围内进行燃烧试验,采用自动定硫仪、综合烟气分析仪对不同燃烧工况下的固硫效率、硫氧化物的释放特性进行测试分析,并采用XRD、FESEM对固硫灰渣进行微观物化分析,探讨了温度、Ca/S、添加剂组成、停留时间、细度等因素对固硫效率和固硫灰渣矿物组成的影响,揭示了不同添加剂的固硫机理以及固硫灰渣中无机组分彼此间、无机组分与含硫物相之间反应产物的生成与分解规律。在固硫物相的形成、分解和转化方面,采用TG-DTG-DSC-FTIR联用的方法研究了CaO、SiO2、Al2O3、Fe2O3、BaCO3与CaSO4的相互作用规律,并采用高温反应器、XRD以及SEM等试验设备和测试方法对不同矿物质与CaSO4混合煅烧后的产物组成及微观形貌进行分析表征,结合多相平衡、热分析动力学以及硅酸盐固相反应动力学原理,探讨了不同矿物质对固硫产物CaSO4稳定性的影响,建立了不同矿物质体系中CaSO4分解的动力学模型,揭示了不同矿物质体系中各种含硫物相的形成、分解和转化规律。在研究脱硫与灰渣利用的同时还考察了燃烧与结渣行为。采用热重分析和单火嘴燃烧试验台对煤中掺入不同比例的添加剂后的燃烧特性进行试验研究,探讨了添加剂的加入对煤粉着火、稳燃、燃尽以及放热特性的影响,并在热力学模拟计算的基础上分析了加入复合添加剂后混合灰样熔融温度的变化特性,从宏观上考察了添加剂加入后对煤粉燃烧和结渣的影响。通过本文大量的试验研究和理论分析,揭示了复杂矿物质体系中的多相反应机理,得到了燃煤固硫与灰渣资源化利用的优化条件,为实现燃煤污染物的有效控制、燃烧副产物的高效利用进而实现能源-资源-环境一体化奠定了理论基础。更多还原

【Abstract】 Coal is the most abundant and widely used fossil energy resource in china. During coal combustion, large amounts of solid residues (coal combustion by-products: CCBs) are generated besides gaseous pollutants, which may cause serious environmental pollution and need well disposal. In this paper, coal combustion, pollutants formation and control as well as high efficiency utilization of the inorganic constituents have been systematicly integrated, and the chemical reaction process of different compound additives during coal combustion and desulfurization, especially the transformation and reaction mechanisms of the inorganic fractions were well investigated in the presence of many advanced testing methods, based on the knowledge of combustion science, mineralogy, physical chemistry of silicate, environment science, material science etc. SOx emission as well as mineral composition and usability of solid resiudes were maily studied before and after additives added into coal, simultaneously the desulfurization mechanisms of different additives with the rule of desulfurization products decomposition and transformation were discussed, furthermore, the heterogeneous reaction mechanisms as well as thermodynamics and kinetics of reactions in inorganic fractions were carefully analyzed when injecting compound additives into coal.To investigate the heterogeneous reaction mechanisms of inorganic constituents, combustion (calcination) experiments of pulverized coal, coal ash, additives and pure mineral reagent as well as the mixture blended with each others were conducted on testing facilities such as high temperature reactor, drop tube furnace and single burner furnace respectively. The mineral composition and micro appearance of the combustion (calcination) solid products were analyzed by XRD and FESEM, then the influences of additive composition and quantity, temperature, particle size, residence time, combustion style and contacting extent, CaO content, and mineralizer on heterogeneous reaction process and products composition of inorganic fractions in the coal-additive system were studied. Based on experimental results, according to heterogeneous equilibrium principles, calculation model of the products about complex mineral system CaO-SiO2-Al2O3-Fe2O3-CaSO4 was established and the equilibrium product compositions under different conditions were simulated, in order to investigate the heterogeneous reaction mechanisms between additives and the inorganic components in coal. The solid products were predicted when coal mixing with additives, moreover, the activation and potential utilization of modified ash were discussed according to the mineral species, concentration and hydration capacity.Researches on desulfurization and the phase characterization of desulfurization residues were conducted on high-temperature electric resistance furnace and drop tube furnace. High sulfur coals mixed with different additives were combusted at the temperature of 800～1400℃, with automated sulfur determinator and integrated flue gas analyzer to determine the sulfur retention efficiency and the emission characteristics of SOx under different combustion conditions, also the mineral composition and microstructure of desulfurization residues were dectected by XRD and FESEM. The effects of temperature, Ca/S ratio, composition of additives, residence time, and particle size on desulfurization efficiency and desulfurization residues composition were investigated to discover the desulfurization mechanisms of different additives and the formation and decomposition fundamentals of the products resulted from the reactions among inorganic constituents as well as reations between inorganic fractions and the sulfur-contained species.For exploring the formation, decomposition and transformation of desulfurization products, integrated TG-DTG-DSC-FTIR was used to study the interactions of CaO、SiO2、Al2O3、Fe2O3、BaCO3 and CaSO4. With the facilities and methods such as high temperature reactor, XRD and SEM, the composition and micro appearance of products generated from calcinations experiments of different minerals blended with CaSO4 were analyzed. Combined with the theories of multiphase equilibrium, thermoanalysis dynamics and silicate solid reaction kinetics, the influences of minerals species on the stability of desulfurization product CaSO4 were studied, and the CaSO4 decomposition kinetic model in different mineral systems was developed to disclosure the formation, decomposition and transformation behaviors of sulfur-contained species in various mineral systems.Combustion and fusion behavior were also investigated with the research of desulfurization and ash utilization. Combustion test of coals doped with different ratio of additives was finished using TG analysis and single burner furnace, and the influences of additives on coal ignition, stable combustion, burn-off as well as exothermic were discussed. Basing on thermodynamic calculation, the change of ash fusion temperature after coal doped with additives was analyzed. The influences of additives on coal combustion and ash fusion were exposed from macroscopic view.Through detail experimental research and theoretic analysis, heterogeneous reaction mechanism in complicated mineral system was explored, and the optimal conditions were obtained to realize coal desulfurization and ash utilization. The whole research work provided scientific basis for effective pollution control and byproducts utilization during coal combustion, as well as harmonious development of energy-resource-environment.更多还原