【作者】 任耀剑；

【导师】 孙智；

【作者基本信息】 中国矿业大学 ， 矿物材料工程， 2009， 博士

【摘要】 炭阳极是电解铝生产的关键。尽管多年来炭阳极的生产工艺、成分配比等方面都得到了很大发展,但其主要原料没有改变,依然是石油焦和煤沥青。为缓解日益匮乏的石油资源及有效的利用我国的无烟煤资源,本文研制了一种新的用于电解铝生产的炭阳极以替代目前主要采用石油焦为原料的炭阳极。本文以低灰无烟煤为研究对象,对无烟煤和石油焦的热解进行了考察。分析了煅烧和酸碱脱灰处理对无烟煤结构和灰分成分的影响。考察了煅烧无烟煤和煅烧石油焦颗粒性质的差异。研究发现:石油焦的热解在200℃到850℃之间较宽的范围内完成,石油焦的结构重排在1050℃左右;无烟煤的热解过程主要集中在550～900℃之间较窄的温度区间,电热煅烧可促使无烟煤趋于石墨化,同时使煅烧无烟煤结构紧凑,其(002)对应的衍射角由25.83o增加至25.89o。脱灰处理使灰分由2.0%降低至0.58%,酸碱脱灰处理对其结构具有解体作用,经过脱灰的煅烧无烟煤的堆砌厚度由原来的10.78782nm降低至8.95094nm,微晶碳的层面由153个碳环降低至123个。脱灰煅烧无烟煤灰分的杂质含量均在要求的范围之内,具有催化作用的Ni、V的统计平均值远低于石油焦的标准,煅烧无烟煤中的S含量仅为0.1%,远低于煅烧石油焦的1.22%。煅烧无烟煤颗粒压碎强度系数比煅烧石油焦高出10~30%,而且耐磨性好,颗粒回胀系数比煅烧石油焦低。采用正交试验方法确定了最佳的粒度级配配方:4~2mm:20%,2~1mm:15%,1~0.075mm:20%,-0.075mm:45%。在炭阳极的制备过程中考察了煅烧无烟煤粉添加量、煤沥青含量及焙烧工艺对焙烧体性能的影响。结果表明:40%煅烧无烟煤粉添加量和18%煤沥青含量的炭阳极灰分为0.95%,体积密度(1.452 g/cm3)和孔隙率(22.77%)配合较好,抗压强度(37.59MPa)和电阻率(54.72μ?·m)均在我国炭阳极标准的一级要求范围内。升温速率对炭阳极的结构影响较大,而对性能参数影响不明显。炭阳极在室温到950℃之间,电子受温度的激发跃迁占主导地位,表现为负电阻温度系数。电阻率随温度的变化关系可用ρt =ρ20 +α(t ? 20)表示。完全石油焦炭阳极电阻温度系数为-0.00932;添加40%煅烧无烟煤粉炭阳极电阻温度系数为-0.01750。对石油焦炭阳极和无烟煤炭阳极的970℃CO2反应性进行了考察,研究了添加剂对970℃CO2反应性的影响。结果表明:无烟煤炭阳极的氧化度和脱落度分别为17.61%和4.42%,比石油焦试样分别低1.29%和0.13%。铝系添加剂在970℃CO2反应性试验中能显著降低炭阳极的氧化度和脱落度以及总的消耗速率。尤其是含量为0.8%的Al粉的氧化度和脱落度达到最小值,分别比不添加时降低32.8%和70%,总消耗速率为39.28 mg·cm-2·h-1。CaF2的加入会增加炭阳极的氧化度3%以上,脱落度增加4倍,总的消耗速率增加一倍以上。NaF的催化作用更加明显,添加1.6%NaF氧化度为29.76%,脱落度增加至33.85%,总的消耗速率为不含添加剂时的3倍。对炭阳极的氧化机理进行分析,认为添加煅烧无烟煤的炭阳极能够阻止600℃的空气氧化燃烧。而炭阳极的970℃CO2反应性则要通过改善炭阳极微观结构和降低煤沥青焦的反应性两个方面来综合考虑。该论文有图57幅,表39个,参考文献122篇。更多还原

【Abstract】 Carbon anode is the key to electrolytic aluminium production. Petroleum coke and coal pitch are still the principal raw materials of carbon anode though there is a quite great progress in the production technology, ratio of constituents and other aspects. In order to release the situation that increasingly scarcity petroleum resources and utilize anthracite resources more efficiently of China, a new electrolytic aluminium carbon anode was adopted to replace petroleum coke carbon anode.In this paper, low ash content anthracite was taken as the investigated subject, thermolysis process of anthracite and petroleum coke were investigated at the same time. The effect of calcined and acid-base deliming to the structure and ash constituent of anthracite was analysised. Particle properties difference between calcined anthracite and calcined petroleum coke were studied in the same time. The results show that thermolysis process of petroleum coke acted in a width temperature range form 200℃to 850℃, and the structure reconstructe at 1050℃, thermolysis process of anthracite mainly concentrated in a narrow temperature range form 550℃to 900℃and electrolytic calcine would made anthracite more graphitization and the structure transformed more compacted at the meantime, diffraction angle of (002) crystal plane form 25.83o inceased to 25.89o. The ash content of calcined anthracite descended form 2.0% to 0.58% after deliming treatment and acid-base deliming has some decomposition effect to the structure of anthracite, stack thickness form 10.78782nm reduced to 8.95094nm and the number of carboncycle in microcrystallite carbon form 153 reduced to 123.All impurity elements content of deliminged calcined anthracite are in the range of requirements, assembly average of some elements for example Ni and V that have catalysis effect are far below the standard of petroleum coke. Besides this, sulfur content of calcined anthracite is only 0.1% while the value is 1.22% in calcined petroleum coke. Calcined anthracite has better abradability and lower resillent-elasticity recovery coefficient than petroleum coke, withal particle crushing strength coefficient exceeded the value of petroleum coke 10~30%. The best size fraction batch formula that determined by orthogonal test was listed as follows: 4~2mm:20%, 2~1mm:15%, 1~0.075mm:20%, -0.075mm:45%.Effect of calcined anthracite content, coal pitch content and roasting technology to carbon anode properties were researched in carbon anode preparation process. The results show that ash content is 0.95%, volume density(1.452g/cm3) and porosity(22.77%) match well, compression strength(37.59MPa) and electrical resistivity(54.72μ?·m) are all in range of the first class standard of carbon anode of China when carbon anode including calcined anthracite content and coal pitch content is 40% and 18% respectively. Heating-up speed has a relative great effect to the structure of carbon anode and obscure to the properties. Electron transition occupated principal position and the carbon anode shown negative temperature coefficient of resistance when the temperature raised from room-temperature to 950℃. The relationship of electrical resistivity with temperature changed could been described as follows:ρt =ρ20 +α(t ? 20). Temperature coefficient of resistance is -0.00932 when carbon anode was made by total petroleum coke, and the value is -0.01750 when carbon anode had 40% calcined anthracite content.CO2 reactivity of petroleum coke and calcined anthracite carbon anode at temperature 970℃were investigated in this paper, the effect of additives to CO2 reactivity at temperature 970℃were explored at the same time. The results show that oxidization degree and slough degree of calcined anthracite carbon anode is 17.61% and 4.42% respectively, 1.29% and 0.13% lower than petroleum coke carbon anode sample in the same condition. Aluminium serial additives could obviously reduced oxidization degree, slough degree and total consumption speed. In all additives, 0.8% Al powder content could decreased oxidization degree and slough degree both to minimum value, 32.8% and 70% lower than no Al powder addition respectively ,and total consumtion speed has the mininum value 39.28 mg·cm-2·h-1. The additive CaF2 would increased oxidization degree more than 3% compared with no additive carbon anode, slough degree would increased four times and total consumtion speed would raised to more than two times. The catalysis effect of NaF additive is more markedly than the others. When the content of NaF is reach to 1.6%, oxidization degree would arrived to 29.76%, slough degree would increased to 33.85% and total consumtion speed would raised to three times compared with no additive carbon anode.Oxidation mechanics of calcined anthracite carbon anode and petroleum coke carbon anode were both analysed,and it draw a conclusion that adding calcined anthracite into carbon anode could impeded air oxidate burning at 600℃temperature and CO2 reactivity at temperature 970℃improvement must consider form two aspects: microstructure of carbon anode improved and depress reactivity of coal pitch coke.更多还原