【作者】 杨柳；

【导师】 王世和； 王小明；

【作者基本信息】 东南大学 ， 环境工程， 2006， 博士

【摘要】 石灰石-石膏湿法烟气脱硫工艺是目前技术最成熟、应用最广泛的脱硫工艺,在可预见的将来,典型的石灰石一石膏法仍将占据主要地位。而随着国家《火电厂大气污染物排放标准》的提高和《排污费征收使用管理条例》的实施,对氮氧化物的控制,必将提高到新的地位,因此,对石灰石-石膏湿法烟气脱硫工艺进行适当的改造使之同时具有脱氮能力,是今后脱氮技术研究的一个重点。加入添加剂后,使石灰石-石膏湿法烟气脱硫工艺同时具有脱氮能力,是本研究的重点内容。这既是国内外领先的研究内容,也是中国国电集团公司下达国电环境保护研究院的重点研究项目。本研究的全部试验研究在该研究院完成。研究从以下几个方面展开:1、收集和消化国外最新的脱氮技术和工艺,掌握世界上最新的脱氮技术;调研国内最新脱氮技术的研究内容和手段,摸清国内的脱氮现状;针对国内外的脱氮研究现状,制定适合我国火电厂现状的脱氮技术的研究重点和思路。2、通过小试,对数种添加剂进行初步筛选,得出尿素在脱氮过程中有着非常明显的作用。以此作为添加剂具有价廉、易得的优点,故将之定为进一步小试的添加剂。在进一步小试中,对吸收反应的pH值、吸收反应气液接触时间、吸收反应温度、烟气中NO_x的氧化度以及添加剂的加入量等因素进行优化,找出最佳的工艺条件,为下一阶段的中试打下基础。3、中试所使用的设备是国电环境保护研究院的简易湿法脱硫工艺试验装置,将该系统改造后用于脱硫脱氮一体化工艺试验。研究过程中,探索了尿素添加剂在湿法烟气脱硫脱氮吸收反应中的作用、特性、反应速率、反应机理以及各种工艺条件对脱硫脱氮效率的影响。结果表明:在简易湿法石灰石-石膏烟气脱硫系统的石灰石浆液中添加尿素后,其有着较好的脱氮能力。在简易湿法石灰石-石膏烟气同时脱硫脱氮工艺试验台上运用尿素作添加剂,按小试得出的最佳工艺条件进行试验,烟气中SO₂的脱除效率达到90%以上,NO_x的脱除效率可达到50%以上。4、在确认尿素具备脱氮能力后,又从热力学上对尿素作添加剂湿法烟气同时脱硫氮吸收反应的可行性和限度进行分析计算,结果表明:该吸收反应不仅是可行的,而且在通常情况下,有着非常高的脱氮效率。5、通过对反应产物的分析可知,如果排浆后的浓吸收液不进行强制氧化,反应后吸收液中含有大量的亚硫酸盐,这样生成的石膏副产品将无法使用。但通过曝气氧化处理后,有90%以上的亚硫酸根转化为硫酸根。经脱水分离,副产品石膏中的半水亚硫酸钙的含量非常低,对石膏的正常应用无任何影响。化学分析还表明,添加尿素后,添加剂对原工艺系统和副产品的影响皆可忽略。6、经济技术分析表明:尿素作添加剂湿法烟气同时脱硫脱氮工艺具有投资省、运行费用低、对原有的WFGD系统无不良影响,有着广阔的应用前景,其应用将会产生很好的经济效益,与同时投产WFGD和SCR系统相比,可节约大量的资金。7、通过对SO₂和NO_x吸收过程的分析可知,在尿素作添加剂石灰石-石膏湿法烟气同时更多还原

【Abstract】 Wet limestone-gypsum FGD（flue gas desulfurization）technology is the maturest and most largely applied currently. In the foreseeable future, the typical limestone-gypsum way will be still dominant. With the raise of“The Exhausting Standard of the Air Contamination in the Power Plant”and the execution of“the Managing Ordinance of How to collecting and Using the draining Fee”, the control of NO_x will be more important. Therefore, it will be the main research to remove DeNox in the FGD process. It is also the main research point of the essay to add the additive to FGD process to remove DeNox. It is new both abroad and at home. It is largely invested by the China Guodian Group.The research has been developed in the following aspects:1. Collecting, digesting and mastering the latest DeNox technology around the world; researching the most advantaged DeNox technology in China; finding out the research highlight of the proper DeNox technology for the power plants in China according to the current situation.2. Comparing the effect of the different additives in DeNox process, Carbamide was proved to be most effective. Besides, it’s cheap and easily got. Optimizing the pH value during the absorbing reaction, liquid gas contact time, temperature, oxidizability of NO_x and the add-on of additive, finding out the best condition for the next test.3. The equipment in the next test is that for simple wet desulfurization and DeNox process with the capacity of 10000Nm3/h. The simulated flue gas comprises air, liquefacient SO₂ and NO. The gas enters the absorber ofπtype from the inlet duct,then goes down to the downstream reacting area and then goes up to the upstream reacting area. After being washing, it goes to the ME of two layers （the first layer on the upper reacting area while the second on the outlet duct）. The clean stimulated gas is discharged through the ID fan. In the research, the effect, characteristic, reacting velocity, reacting principle of the carbamide in wet flue gas desulfurization process and the different effect of the various process conditions to the carbamide. It turns out that adding carbamide to the limestone slurry in simple limestone-gypsum FGD process could deprive NO_x. Under the best working condition with carbamide as the additive, the removal efficiency of SO₂ is higher than 90% and that of the NO_x is higher than 50%.The above mentioned research that carbamide is added to the limestone slurry as additive is the innovative way in the world.4.After confirming that carbamide could help remove NO_x, I have analyzed its feasibility according to thermodynamics theory and calculated its limitation. The conclusion is such absorbing reaction is feasible with very high DeNox efficiency.5. By analyzing the reaction product, I have found that there will be large quantity of sulfite in the reacted slurry without oxidizing forcedly the dense absorbing slurry. Then the byproduct of gypsum could not be used. Yet over 90% of SO₃^2- could be transformed to sulfite by being aerated. After dewatering separation, the content of calcium sulfitc in the gypsum is very small, which doesn’t effect the normal use of the gypsum. It’s also concluded that the effect of carbamide to the process system and byproduct could be neglected.6. Through analyzing from economy and technology, there will be low investment, low operation cost and no bad effect to the original WFGD system with carbamide as the additive for desulfurization and DeNox at the same time. Then it will be largely applied in更多还原