【作者】 金航；

【导师】 张世红； 陈汉平；

【作者基本信息】 华中科技大学 ， 热能工程， 2011， 硕士

【摘要】 随着经济社会的发展,超高温烟气发生工艺在钢铁、水泥、冶金等行业有着迫切的需求,但以煤作为燃料的工艺会产生大量的污染性气体,对环境造成破坏,煤中硫就是其中主要的污染源。本文针对超高温烟气发生工艺过程中的脱硫控制机理进行了相关基础性和工艺性研究,对工艺过程中硫的迁徙及脱除特性进行了深入分析,为实际生产过程中进行脱硫提供了理论依据和经验参数。选取四川煤、山西II类烟煤、黄陵烟煤和林南仓煤四种煤在固定床台架上进行了氮气氛围下的热解实验和氮气/水蒸气氛围下的气化实验,对热解和气化过程中煤中各形态硫的迁徙特性、硫在各产物中的分布等进行了研究。煤中大部分无机硫在热解和气化过程中均会发生分解,但只有一部分会逸出,其中黄铁矿硫的分解以及煤中碱土金属的固硫作用均可生成无机硫化物残留于半焦中。温度的升高及水蒸气含量的降低均不利于无机硫化物的析出。煤中有机硫的脱除与煤种性质存在较大联系,另外高水蒸气含量可以有效抑制煤中活性有机质的固硫作用,有利于煤中有机硫的脱除。H₂S是煤热解和气化过程中主要的含硫气体,其释放量与原煤含硫量、水蒸气含量、煤阶、碱土金属含量等有关。硫在热解和气化产物中的分布为:焦中最多,其次为气相,焦油中较少,水蒸气含量的增加有利于硫从焦中向气相中迁徙。选用四川煤在流化床台架上进行了空气/水蒸气气化实验,以及气化半焦与灰渣混合物的燃烧实验,对Ca/S比、水蒸气含量、石灰石品种等因素对脱硫的影响进行了研究。在气化及燃烧过程中,水蒸气含量越高,气化部分释放的硫越多,但总体来讲,大部分硫在燃烧部分释放。Ca/S比的增加有利于脱硫效率的提高,石灰石的品种对于脱硫的影响存在差异。水蒸气含量的提高不利于脱硫效率和石灰石利用率的提高。最后结合实验结果,对超高温烟气发生工艺的脱硫提出了一些意见:工艺过程中脱硫的重点在于燃烧部分,以未煅烧石灰石作为脱硫剂的效果并不理想,脱硫效率和脱硫剂利用率均较低,主要原因在于燃烧部分未能较好地脱除SO2。为了改善超高温烟气发生工艺的脱硫效果,有必要在燃烧部分单独添加脱硫剂,另外对脱硫剂提前进行煅烧也是手段之一。更多还原

【Abstract】 With the development of economic and society, there exists a urgent need of ultra-high temperature fume producing process in the steel, cement, metallurgy and other industries. However, the process with coal as its main fuel would produce large amounts of polluting gases which would damage the environment, and the critical reason is sulfur in coal. In this paper, the fundamental and technological research of desulfurization mechanism of the ultra-high temperature fume producing process was studied. The migration and removal characteristics of sulfur during the process was analyzed in-depth, which provided theoretical basis and empirical parameters to the actual production.In this study, Sichuan coal(SC), Shanxi coal(SX), Huangling coal(HL) and Linnancang coal(LN)were used. The pyrolysis experiment under nitrogen atmosphere and gasification experiment under nitrogen/steam atmosphere were determined in a fixed bed bench at atmospheric pressure. The migration characterisics of different forms of sulfur and the distribution of sulfur in different products druing pyrolysis and gasification were studied. Most inorganic sulfur in coal decomposes during pyrolysis and gasification, but only part of them release.The decompositon fo pyrite and the sulfur fixation of alkaline earth metals in coal could generate inorganic sulfide sulfur which remains in semi-coke.The increasing of temperature and the decreasing of the steam content both have a negative influence on the releasing of inorganic sulfide sulfur. There is a big link between the removal of organic sulfur in coal and the coal properties. High content of steam could inhibit the sulfur fixation of active organic matter effectively, which is propitious to remove the organic sulfur in coal. H2S is the main sulfurous gas during pyrolysis and gasification, and the amount of it is impacted by the sulfur content of raw coal, the steam content, the coal rank, the alkaline earth metal content and so on. The distribution of sulfur in products druing pyrolysis and gasification is as follows: most in coke, followed by gas, tar least. The increasing of steam content is in favor of transforming the sulfur from coke to gas.Sichuan coal was chosed to take gasification experiment under air/steam and combustion experiment of the mixture of semi-coke and ash in a fluidized bed bench at atmospheric pressure. The impacts of some factors, such as Ca/S ratio, steam content, kind of limestone and so on, on the desulfurization were studied. The releasing characteristics of sulfur in coal during gasification and combustion is related with the steam content. The higher the steam content is, the more sulfur would release during the gasification, but generally speaking, most sulfur releases during combustion. The increasing of Ca/S ratio is in favor of increasing the desulfurization efficiency. The impacts of different kinds of limestone to the desulfurization are different. The increasing of steam content isn’t in favor of increasing the desulfurization efficiency and the use ratio of limestone.Finally, combined with the experiment results, some advises about desulfurization of the ultra-high temperature fume producing process were proposed: the desulfurization of combustion is important. Using uncalcined limestone as the desulphurization agent is not ideal, both the desulphurization efficiency and sorbent utilization was low, primarily due to not remove SO2 effectively druing combustion. In order to improve the desulfurization in ultra-high temperature fume producing process, it’s necessary to add desulfurization agent in the combustion part, and another way is to calcine the desulfurization agent in advance.更多还原