【作者】 李寒旭；

【导师】 张明旭；

【作者基本信息】 安徽理工大学 ， 环境工程， 2009， 博士

【摘要】 深入研究淮南煤中矿物组成、矿物粒度分布规律、还原性气氛下灰的行为特征和熔融机理,对于从根本上解决淮南煤在气化过程中与灰相关的各种技术和环境问题具有重要的作用,对于淮南煤的清洁、高效、经济利用具有重要意义。本论文利用计算机控制扫描电镜(CCSEM)、X射线衍射仪(XRD)、X射线荧光光谱(XRF)研究了淮南矿区煤样的矿物组成、煤灰的晶体矿物组成和化学组成以及矿物颗粒分布规律;在还原性气氛下,考查了利用助熔剂和配煤降低淮南煤灰熔融温度,改善粘温特性的影响规律,探讨了煤中矿物组成、晶体矿物组成与煤灰熔融温度的关系;利用傅立叶变换红外光谱仪(FT-IR)、XRD、CCSEM等现代分析测试手段,探讨了助熔剂和配煤对淮南煤灰的矿物组成变化规律和煤灰熔融过程的影响机理;利用FactSage热力学软件计算了还原性气氛下,随温度变化,煤灰液相生成量和矿物组成变化趋势、对高温下煤灰行为特征和煤灰熔融温度进行了预测。主要得到如下几个方面的结论。1.淮南煤中矿物组成和粒度组成分布规律(1)淮南煤中矿物主要由高岭石、蒙脱石、石英、黄铁矿、方解石、白云石、未知组成和其它微量矿物所组成。高岭石等粘土矿物和石英含量占矿物含量的60%以上,高岭石含量愈高的淮南煤,其煤灰熔融温度也呈现愈高的趋势。淮南煤与G3、B1和H煤三种外地煤(煤灰熔融温度小于1350℃)所含主要矿物组成种类基本相似,但含量差别很大,主要区别是淮南煤中高岭石和其它粘土矿物含量高。粘土矿物、黄铁矿、方解石和白云石含量对于煤灰熔融温度高低起决定性作用。(2)淮南煤中高岭石、石英矿物的粒度呈现双峰分布的规律,直接导致煤中矿物颗粒分布也呈双峰分布的趋势,矿物颗粒直径分别在10μm和100μm左右时达到最大值。蒙脱石、方解石和黄铁矿颗粒的分布呈现单峰分布的规律,黄铁矿在煤中主要以100μm大颗粒形式存在。矿物颗粒的大小和分布对煤气化过程中灰的化学行为、熔融特性和飞灰粘附特性会产生重要的影响。2.助熔剂与配煤对煤灰熔融温度的影响(1) ADC、ADF、ADN三种助熔剂均可不同程度的降低淮南煤灰熔融温度,三种助熔剂对淮南煤灰的助熔效果的排列顺序为ADN＞ADF＞ADC。ADC对HN115和HN119煤灰熔融温度的影响趋势相似,随助熔剂加量增加,煤灰熔融温度呈现先上升,迅速下降和上升的变化趋势,说明了ADC助熔剂助熔反应的复杂性。ADN助熔剂对淮南四种煤的助熔效果十分明显。ADN助熔剂的灰基添加量为4.55%时,可以使KL1煤灰熔融温度降到1380℃,满足Texaco液态排渣操作温度的要求,助熔效果相比其它淮南煤更为显著。随ADF添加量增加,四种淮南煤灰熔融温度均呈线性下降趋势。(2) H、G3、B1煤与淮南煤配合可以使淮南煤灰流动温度降低至1380℃以下,满足Texaco气化炉运行要求。三种煤对淮南煤配煤助熔效果排序为:B1＞H＞G3。随配煤比例的增加,除B1与HN106配煤灰流动温度呈现非线性变化趋势外,配煤后煤灰的流动温度的变化呈现线性下降的变化趋势。(3)利用多元线性回归原理,分别建立了助熔剂添加量、配煤比例与淮南煤灰熔融温度关系数学模型。3.助熔剂与配煤对煤灰粘温特性影响(1)淮南HN119与KL1煤灰粘度对温度变化的反应较敏感,随温度的降低,粘度迅速升高,属于“结晶渣”类型,不适合在液态排渣气化炉中使用。在相同温度下,B1和G3煤灰的粘度比淮南煤灰的粘度要低的多,B1煤的灰渣型为“近玻璃体”类型,G3煤为典型的“玻璃体渣”类型,较为适合在液态排渣气化炉中使用。(2)添加助熔剂和配煤都能有效降低淮南煤灰渣粘度。添加灰基8.7%ADN助熔剂时,可以使HN119煤灰在1380℃时粘度达到20Pa·s,其渣型由“结晶渣”转变为“近玻璃体渣”类型。60%KL1与40%B1煤相配,粘度达到25Pa·s时对应温度比KL1原煤降低250℃,且渣型也由“结晶渣”转变为“近玻璃体渣”类型。(3)三组粘度经验公式被用于预测配煤和添加助熔剂后淮南煤灰的粘温特性,并通过实测值与计算值的对比讨论了经验公式的适用性。4.高温煤灰化学行为和熔融机理研究(1) XRD与FTIR分析结果表明,还原性气氛下,当温度高于1350℃时,淮南煤灰主要含有莫来石和非晶态物质,升温过程中莫来石的形成是淮南煤灰熔融温度高的主要原因。(2)配煤可以有效降低淮南煤的熔融温度,配入低灰熔融温度煤后,高温下莫来石衍射峰强度下降,同时形成钙长石、铁橄榄石和铁尖晶石,它们与石英等矿物之间易发生低温共熔作用,形成低熔点的共晶体使得煤灰熔融温度降低。添加助熔剂ADC、ADF和ADN后,在高温、还原性气氛下,有效破坏了铝硅酸盐的结构,抑制了高温下莫来石的生成,同时钠长石、钙长石、铁橄榄石的含量逐渐增多,与煤灰中石英等矿物在高温下发生反应,形成低熔点的共晶体,从而降低熔融温度。5.利用FactSage热力学软件预测煤灰熔融过程(1) FactSage热力学软件可以预测还原性气氛下高温煤灰行为和煤灰熔融温度。对淮南原煤灰及淮南HN115(FT=1400℃)、HN106煤(FT＞1600℃)添加ADC助熔剂后,进行了液相生成量计算,得出液相生成量为75-80%时,对应的温度与实测煤灰流动温度(FT)接近,可以很好的预测煤灰流动温度。(2)利用FactSage热力学软件计算的高温煤灰矿物的转化过程与XRD分析的结果相一致。FactSage热力学软件结合XRD分析测试技术,可以用于很好的预测矿物之间的反应、以及矿物的转变和熔渣的形成。可以用来定量预测在气化过程熔渣的形成过程。总之,本研究为高灰熔融性淮南煤在煤气化过程中的清洁、高效、合理利用提供了理论基础依据,对于解决煤炭利用过程中与灰有关的各种问题具有理论指导意义。更多还原

【Abstract】 To solve the ash related problems of Huainan coal during the commercial gasification process,it is essential and significantly important to know the proportion and particle size distribution of mineral matter in coal and to understand and predict the mechanism of mineral transformation and the ash behaviour in reducing conditions.Understanding the properties of mineral and ash behaviour of Huainan coals will help in providing a better understanding of the factors that control their performance in gasifier and a clean,effective and economic way to use Huainan coal resources.Huainan coal samples and three other coal samples from Shangdong, Henan,Gansu province of China,were analyzed by Computer-controlled scanning electron microscope（CCSEM）,X-ray diffraction（XRD） and X-ray fluorescence （XRF） for their mineralogical phases,particle size distribution and elemental composition respectively.Effect of coal blending and flux addition on ash fusion temperature（AFT） and slag viscosity were studied.The mineral transformation and ash behaviour were characterized by XRD,Fourier transform infrared spectroscopy （FTIR） and CCSEM coupled with a modified ash fusion tester.The liquid phase formation,mineral phase change and conversion were calculated by FactSage thermodynamics software.The main conclusions are shown as below.1.The mineral composition and particle size distribution in Huainan coal samplesThe mineral phases,which vary with coal samples somewhat,generally include quartz,hematite,anhydrite,muscovite and anatase,implying the complicated behaviour of ashes though they were collected from Huainan coal deposits.The mineral matter was characterized by higher aluminosilicate clay minerals contents （more than 60%of the total mineral matter in coal） with quartz,which accounts for the higher ash flow temperatures（FT）,frequently higher than1500℃.It is suggested that the higher the kaolinite in Huainan coals,the higher the AFT.Comparisons of the mineral contents of Huainan coal with that of G3,B1,and H coals（FT＜1350℃） showed the mineral phases are similar while the mineral contents are quite different. Low content of kaolinite-type clays and high content of calcite,dolomite and pyrite in coals are beneficial to ash melting.The ash melting behavior of Huainan coal in reducing condition is to be controlled by the mineral phases,mainly by that of kaolinite,illite,pyrite and calcite,rather than by the average chemical composition of coal ash.The mineral grains in Huainan coals have bimodal size distribution in six typical Huainan coals as a result of the high contents of kaolinite and quartz show the bimodal particle size distribution.The diameter of mineral grains reaches peak maximum at about 10μm and 100μm respectively.The particle size of the montmorillonite,quartz and pyrite is in a single size unimodal distribution.The minerals composition and grains size distribution are extremely important and have an effect on the ash melting behavior,minerals transformation and fly ash deposit in the coal gasification process.2.Effects of fluxes and coal blending on the ash fusion temperatureThe AFT of four Huainan coal samples,HN113,HN115,HN119 and KL1,could be reduced at certain degree by adding fluxes of ADN,ADC,ADF（wt%,ash base）. The fluxing action rank for Huainan coal samples was listed as ADN＞ADF＞ADC. The addition of CaO at around 8%increased the melting temperature of HN115 and HN119 coal ashes somewhat.With the increase of its addition,the melting temperature of ash initially decreased gradually,reaching its minimum value at the amount of CaO around 25%,and however increasing again with the further addition of CaO,indicating the complicated behaviors of mineral phase change.The flux of ADN had the most significant effect on the AFT of four Huainan coal samples, especially for KL1 coal samples.The FT of KL1 coal ash could be reduced to 1380℃with the addition of 4.55%ADN,which fulfils the requirement of Texaco gasification process.With the addition of ADF,the ash fusion temperature of four coal samples showed a linear decrease tendency.The FT of Huainan coal ash samples could be decreased to less than 1380℃by blending with G3,B1 and H coals respectively.The effect for lowering the ash fusion temperature of coal blends was listed as the sequence B1＞H＞G3.With the exception of HN106 coal blended with B1,the ash flow temperature of blended coal showed linear decrease with the increase of blending ratio of G3,B1 and H coal.The mathematical model of ash FT with blending ratio and the adding amount of fluxes were established by the principle of multiple linear regressions respectively.3.Effects of fluxes and coal blending on the viscosity-temperature properties of Huainan coal ashThe slag viscosity of HN119,KL1 coal increased sharply with the decline of temperature,which implies a crystalline slag（short slag） at high temperature and is not suitable to be used in Texaco and Shell gasifier.The slag viscosity of G3 and B1 coal is much less than that of Huainan coal ash at the same temperature.The slag viscosity-temperature plot showed a typical glass slag（long slag） for G3 coal and a glass like slag for Blcoal,which is suitable for the operation of Texaco and Shell gasifier.The slag viscosity of Huainan coal could be effectively decreased by coal blending and flux addition.The slag viscosity of HN119 coal by adding 8.7%ADN （ash base,wt%） reached to 20Pa·s at 1380℃.Meanwhile the slag type changes from crystalline slag to glass like slag.The slag viscosity of 60%KL1 coal blended with 40%B1 coal reached to 25Pa·s at the temperature less 250℃than that of the parent KL1 coal.In the mean time,the slag type changes to glass like slag type.The slag viscosity was calculated through three empirical formulas for coal blending and fluxes addition.The fitness between the results calculated by empirical formulas and the tested results was also discussed.4.Ash behaviour and melting mechanism of Huainan coal at high temperatureThe minerals transformation and ash behaviour were characterized by XRD and FTIR.The results showed that the main components at 1350℃in the slag of Huainan coal were mullite and glass phase.The formed mullite phase,which caused the high ash melting temperature of Huainan coals,reached to maximum at 1250℃,but showed a tendency of slow decline when the temperature was over 1250℃. Differences in peak intensity of mullite and anorthite reflected differences in phase concentration of the quenched slag fractions,which contributed to the differences of ash melting temperature.The intensity of mullite formed at high temperature was declined by blended with low AFT coals.Meanwhile the formed anorthite（CaO·Al₂O₃·2SiO₂）,hercynite （FeO·Al₂O₃） and hematite phases reacted with quartz to form a low-melting eutectic mixture.The structure of main aluminosilicate phases in Huainan coals was broken at high temperature by adding flux of ADC,ADN and ADF under reducing atmospheres. The formation of mullite was restrained while albite,anorthite,hercynite phases increased gradually and reacted with quartz to form a low-melting eutectic mixture which lowered the AFT of Huainan coals.5.Prediction of Ash behaviour of Huainan coal by FactSage Thermodynamics softwareFactSage has been an invaluable tool to predict the ash behavior and AFT at high temperature under reducing atmosphere.It had demonstrated a good agreement between the liquid phase formation of Huainan coal ashes as the function of temperature and the tested AFT.The predicted FT,at which the calculated weight percentage of liquid phase reaches to about 75～80%for Huainan coal ash samples, was quite fit for the tested FT.The maximum temperature difference between the tested FT and the predicted FT is less than 74℃,which is within acceptable range.It could be concluded that FactSage in combination with XRD is a new tool to predict the reactions occurring between minerals,as well as the mineral transformation and slag formation.This is probably an improved way to interpret melting properties of mineral matter in coal and assist in quantifying slag formation in gasifier operation.In a word,this paper will provide the fundamental knowledge of Huainan coal for the purpose of utilizing Huainan coal in a clean and efficiency way.It will help us to better understand the ash behaviour of coal in reducing condition and solve the ash related problems in coal utilization process.更多还原