【作者】 王文龙；

【导师】 骆仲泱； 倪明江； 岑可法；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 博士

【摘要】 在我国的能源消费构成中，煤炭占绝对主导地位，从而产生了数量庞大的电厂灰渣，到2001年，年排放量已经超过1.6亿吨。对于电厂灰渣的综合利用，人们已经进行了几十年的研究；然而，目前我国的灰渣利用率仍不足60％，每年由于建灰场贮灰而占用的土地依然在不断增加，不但污染环境，还耗费了大量的人力财力，从而形成了虽然在拼命利用却仍然不断累积的困惑局面。其难点就在于没有途径能够将数量如此巨大的固体废物全部消费掉。只有彻底改变灰渣的性质，从源头杜绝废物的产生，才能使灰渣综合利用问题得到根本解决，也使循环经济实现真正的闭路发展。 回转窑工艺是当前主导的水泥烧成技术，但研究如何使生料的预热、分解与烧成均能在悬浮或流化状态完成，在1300℃左右烧成熟料，一直是水泥煅烧新工艺的重要发展方向。而悬浮燃烧和流化床燃烧技术是燃煤电厂锅炉中广泛应用的成熟技术。于是本文创造性地提出了在煤粉炉中直接悬浮烧成水泥熟料，实现电力和水泥联产的设想。 为验证在煤粉炉中直接烧成水泥熟料的可行性，本文以分段多相反应实验台为主要的试验系统，开展了一系列探索性的试验研究。试验中，分段多相反应实验台炉温设定在1300℃，物料在高温区的停留时间可达7s。试验证明，煤与CaO在适当的配料组成下是可以在悬浮燃烧的同时烧成硅酸二钙、硫铝酸钙等水泥熟料矿物的，但在悬浮煅烧的状态下硅酸三钙难以形成。这证明了煤粉锅炉直接联产水泥熟料具有可行性，不过联产所能实现的肯定不会是常规的硅酸盐水泥熟料。本文经过反复试验，得出了CaO的最佳掺加范围，用石灰标准值KSt值表示应在63～68之间。在用CaCO₃替代CaO进行的试验中发现，煅烧出的样品游离CaO较高，并且含钙物相的含量也有所减少，因此综合考虑，在进一步研究前用CaCO₃替代CaO还不适宜。 为了获得最佳的煅烧制度，本文通过大量试验和理论分析，较系统地研究了煅烧温度，物料停留时间，物料聚集状态，粉磨方式，以及煤种的自身组成等各种因素对水泥熟料矿物在悬浮状态下快速烧成的影响，从而为扩大性试验以及工业上的实际应用奠定了基础。在悬浮状态下快速烧成水泥熟料矿物，煅烧温度的选择范围比较宽，在1200℃以上都可以，对于本文试验所选用的长广煤而言，最佳温度范围在1250～1350℃之间；并且随着煅烧温度的提高，产品的硅酸二钙含量增加，钙铝黄长石含量减少，于是产品的性能得以提高。物料停留时间在1～7s内变化时，产品质量没有太大变化，但随着停留时间的延长，固相反应进行得更为完全。而增加物料颗粒在燃烧过程中的聚集程度，增加颗粒间碰撞接触的机会，也有利于固相反应的进行，有利于产品质量的提高。将煤与生石灰进行共同粉磨，可以促进煤粉颗粒与氧化钙颗粒之间的粘结附着，从而在燃烧过程中可以更充分的进行固相反应。另外，通过采用兖州煤进行试验，证明在悬浮状态下快速烧成水泥熟料矿物更适合于硫分较高的煤，从而为高硫煤的使用开辟了新路。 通过将长广煤与生石灰混磨后悬浮煅烧出的样品进行定量x衍射分析，发现样品中75％左右的成分属于具有水硬性的矿物，其中大部分是α′-2CaO·SiO₂和β-2CaO·SiO₂，其余是早强型的硫铝酸钙，另外不足25％的是没有水硬活性的矿物摘要成分。从样品的矿物组成看，它接近于硫铝酸盐系列的水泥，而又与现有工业产品的成分含量有差别，因此，根据其特点可以定义为“高硅硫铝酸盐水泥熟料”。 对于高硅硫铝酸盐水泥熟料，通过净浆强度试验和砂浆强度试验，发现其具有早期强度偏低但后期强度发展潜力大的特点，在掺加上30%的硅酸盐水泥熟料后，强度可以达到32.5强度等级的硅酸盐水泥的国家标准。因此这就为高硅硫铝酸盐水泥熟料的实际应用指明了途径:对前期强度性能要求不是很高的一般性工程可以直接使用高硅硫铝酸盐水泥:而对前期和后期强度性能要求都较高的工程则可以将高硅硫铝酸盐水泥与硅酸盐水泥混合使用，其效果甚至比单独使用硅酸盐水泥更好。 本文还对高硅硫铝酸盐水泥熟料的水化机理进行了研究，建立了初步的水化化学。其水化过程中主要的水化产物是高硫型水化硫铝酸钙（AFt）和水化硅酸钙 （CaO一5102一玩O），这两者也是其强度的主要来源。 本文还通过理论模型的建立，阐述了高硅硫铝酸盐水泥熟料的形成机理，建立了在超快速升温锻烧条件下的矿物形成化学，从而为燃煤电厂锅炉联产水泥技术奠定了初步的理论基础。物料颗粒在1300℃悬浮燃烧时的升温速率可高达105¹06℃/s，因此，可以说物料颗粒几乎瞬间就达到了环境温度，从而使物料颗粒的燃烧、灰化和固相反应过程也几乎是同时发生。在煤的燃烧和灰化过程中，原煤中的矿物质主要是粘土矿物完成脱水和分解，形成氧化物形式的si仇、A12岛、FeZ伪;同时，大部分的有机硫和无机硫都氧化形成S伍，然后Sq进一步与Cao进行气固反应，形成CaS04。继而，由于新生态的si仇、从伪、FeZO3和CaS伍等物质都具有很高的活性，它们与Cao之间的固相反应得以迅速进行。本文通过相图分析、热力学分析、固硫机理分析和动力学分析等多种手段，最终确定了煤与Cao的混合物料悬浮燃?更多还原

【Abstract】 Coal is the most important energy source in China. To date, over 70 percent of energy consumption still stems from coal combustion. Therefore, large amounts of solid wastes are generated from thermal power plants every year. In 2001, for instance, the newly generated ashes amounted to 160 million tons. Although researchers have studied the comprehensive utilization of ashes for decades and have found many ways to use these solid wastes, it is a problem that there are still a lot of ashes left which cannot be used and must be put into landfills, which require large area of land and may pollute the surroundings. The difficulty is that the amount of ashes generated in thermal power plants is too large to be completely utilized. In China, for example, the ashes that can be utilized are less than 60 percent.Rotary kilns, whose disadvantage is the low heating rate of raw materials, are generally used in cement clinker calcination. The development direction of cement clinker calcinations is to calcine at about 1300C with raw materials in suspended or fluidized state. In this way, raw materials can finish heating, decomposing and calcining nearly at the same time, for the hating rate of particles is very high. It is well known that suspended-bed and fluidized-bed combustion are widely applied in the boilers of power plants. Hence, in this dissertation the idea is put forward to calcine cement clinker in PCC(Pulverized Coal Combustion) boilers, so that electric power and cement can be produced together.To testify the above idea, a serial of groping experiments were done on a two-stage polyphase reaction setup, which was designed and put up by myself. In the experiments, the experimental setup worked at 1300’C, and the material particles could stay at high temperature for about 7s. Through the experiments, it is found that some cement minerals, such as dicalcium silicate(2CaO SiO2) and calcium sulfoaluminate(3CaO 3Al2O3 CaSO4), etc, can generate when coal and lime are grinded together and burnt in suspended state. The best range of added CaO is about 63-68, expressed in the form of KSt. The experiments with CaCO3 replacing CaO were also done in the dissertation, but the results were not exciting because of the high amount of free CaO. In all the experiments, tricalcium cilicate(3CaO SiO2) had not been found all through. Then it can be concluded that co-generating cement clinker in PCC boilers is feasible, yet the product may not be the common silicate cement clinker.This dissertation roundly studied the effect of calcination temperature, calcination time, material coherent condition, material grinding process, and coal component on the formation of cement clinker minerals while calcining in suspended state. To form cement clinker minerals, the temperature above 1200C is enough. For the Changguang coal selected in the experiments, the best range is between 1250~1350C. With higher temperature, usually, more 2CaO SiO2 and less 2CaO Al2O3 SiO2 can be generated. While the calcination time of materials varies between l~7s, the product performancechanges little. However, when the material coherent condition is improved, the material particles can get more chances of collision, so the solid phase reactions can proceed more deeply and the product quality can be better. In addition, by grinding together, the coal and CaO can form agglomeration particles, which can promote the solid-solid reactions. Comparing the experiment result of Yanzhou coal with that of Changguang coal, it is found that coals with high sulfur are more suitable to form cement-like product. Through all the experiments, the practice base has been founded for larger-scale experiments and production on real PCC boilers.The sample, calcined after grinding Changguang coal and CaO together, was quantitatively measured by X-ray diffraction (XRD) analysis. The result shows that in the sample about 75 percent are hydraulic minerals, most of which are ’-2CaO S1O2 and -2CaO SiO2, the left is 3CaO 3A12O3 CaSO4, and that the other 25 percent, mainly 2CaO Al2O3 SiO2, hav更多还原