煤的电化学脱硫基础研究

【作者】 李登新；

【导师】 高晋生； 徐庆莘；

【作者基本信息】 华东理工大学 ， 化学工艺， 2000， 博士

【摘要】 本文在总结前人煤隔膜电化学脱硫的基础上,以北宿、杉木树、南桐煤及汶南煤系黄铁矿为样品,以二苯并噻吩为有机硫模型化合物,在无隔膜电解池中,研究了电解条件对脱硫率的影响。在此基础上利用化学动力学和热力学的原理,借助有关测试技术（XPS、XRD、FT-IR及TG等）,探索了无隔膜条件下电化学脱硫机理和脱硫动力学,最后讨论了电化学处理对煤质的影响。主要结果如下:1、首次运用无隔膜电解装置,较系统地研究了酸性和碱性介质条件下影响脱硫的因素。在适宜的条件下,电化学法能脱除63%以上总硫,无机硫脱硫率最高达到100%,有机硫脱硫率可达60%,同时能脱除部分灰分。2、引入了电化学催化概念,采用催化剂在酸性条件下脱除煤中的硫。研究表明,煤在10%H₂SO₄溶液中电化学处理,锰盐是较优的脱硫催化剂。3、首次对煤系黄铁矿的电化学脱硫进行了研究。结果显示,煤系黄铁矿可以利用电化学方法生产硫酸和铁盐,有可能替代传统的黄铁矿利用方法,并实现零污染排放。4、利用化学热力学原理和有关分析手段,研究高硫煤在碱性和酸性条件下的电化学脱硫机理。在碱性条件下,阳极表面产生的活性氧氧化煤中的硫,将黄铁矿氧化为硫酸根和铁的氢氧化物,有机硫氧化为砜或亚砜,而砜水解为可溶于水的物质而脱除。在酸性条件下,阳极表面产生的Mn³⁺氧化黄铁矿为硫酸铁盐,有机硫为砜或亚砜,进而水解离开煤有机质本体。5、利用化学动力学原理,研究了煤系黄铁矿和煤中黄铁矿的脱硫动力学模型。煤系黄铁矿的脱硫模型为半径缩小的缩核模型,脱硫表观活化能为7.89KJ/mol。煤中黄铁矿的脱硫模型与纯黄铁矿不同,由于煤有机质的影响,在煤表面存在‘活性,黄铁矿（可接近）和“隋性’黄铁矿（难接近）,脱硫速率符合Langumuir-Hinshelwood近似,脱硫表观活化能为10.44KJ/mol。6、电化学处理对煤质的影响与脱硫率有关。更多还原

【Abstract】 A number of coal cleaning methods have been developed,which range from simple crushing and pulverizing to reduce inorganic sulfur,to extensive chemical treatment to reduce inorganic sulfur and a part of organic sulfur.However,an effective and economic process to remove finely disseminated inorganic sulfur and organic sulfur remains to be found.Recently, electrochemical desulfurization,as an economic,lower cost and milder sulfur removal method, has received more attention.Usually,the high sulfur coal was electrolyzed in a diaphragm cell in order to eliminate the sulfur in coal.The anode is a large-area and expensive Pt foil electrode.In the process of desulfurization,the membrane was easily plugged.So a small-area platinum anode or large-area graphite was used to study the electrochemical cleaning of coal in a cell without membrane in this thesis.The effects of electrolytic conditions including potential,temperature,time,kinds and the concentration of catalysts,concentration of coal as well as forms of sulfur in coal on the rate of desulfurization were studied.According to the relationship between the rate of desulfurization and electrolytic conditions,the math models of desulfurization of coal-derived pyrite and pyrite in coal were established in use of chemical kinetic and thermodynamic principles.Then,the reactions of desulfurization were postulated by means of some necessary analytic methods such as XPS,XRD,FT-IR and TG.At last,the influence of electrolysis on the organic matter of coal was also examined.The main results of this thesis are summarized as follows:（1）The effects of electrolytic conditions on desulfurization in acid or alkaline media in the cell without membranes were studied.Under the selective conditions,over 63 percent of total sulfur,60 percent of organic sulfur,I00 percent of inorganic sulfur and a part of ash content can be removed.（2）By means of the concept of electrocatalysts,the effect of catalysts on the desulfurization in acid media was studied.The experimental results show that Mn³⁺is better than Fe³⁺as an electrocatalysts for desulfurization and the rate of desulfurization is related to the kinds and concentration of catalysts,electrolytic temperature,time and so on.If Mn³⁺is selected as the catalyst for desulfurization,the 100 percent of inorganic sulfur and a part of organic sulfur can be removed under these conditions:the room temperature（298K）,8h,smallarea Pt electrode as anode,10 percent of H₂SO₄.（3）It is the first time to study the desulfurization of coal-derived pyrite by electrolysis. When MnSO₄ was used as the catalyst,100 percent of pyrite can be oxidized into SO₄^2- and Fe³⁺at 298K and other selective electrolytic conditions and no pollutant is emitted. Therefore the electrolysis may be a better method by which pyrite can be oxidized into useful products than common pyritic utilization ways.（4）By aid of law of chemical thermodynamics and new analytic instntrnents,the mechanism of desulfurization of coal in acid or alkaline media was investigated.In alkaline media,the pyritic sulfur is oxidized into SO₄^2-,Fe（OH）₂,Fe（OH）₃,and organic sulfur into sulfone or sulfoxide by the active oxygen from anode surface.Then sulfone or sulfoxide can be eliminated by hydrolysis in alkaline media.In acid media,the pyritic sulfur can be oxidized into SO₄^2-and Fe³⁺by Mn³⁺or Fe³⁺from anode surface,While organic sulfur can react with Mn³⁺or Fe³⁺and a part of them can be oxidized into sulfone or sulfoxide.At last sulfone or sulfoxide is leached into solutions by hydrolysis.（5）By means of chemical kinetic principles,the desulfurization math models of coalderived pyrite and pyrite in coal were established.（a）the desulfurization model of coal-derived pyriteThis model is a shrinking core model.By this model,the apparent activity calculated is 7.89KJ/mol.（b）The desulfurization model of pyrite in coalThe pyrite in coal can be divided into the ’high reactive’ pyrite and ’low reactive’ pyrite.So the relation between the kinetic equation of desulfurization according to Langmuir-Hinshelwood approach is as follow:By this model,the apparent activity calculated is 10.44KJ/mol.（6）The influence of electrolysis on the organic matter of coal was studied.It is limited if the rate of organic sulfur removal is not high.Otherwise the influence of electrolysis on the organic matter of coal is strengthened and the yield of cleaning coal becomes lower.更多还原