催化剂对煤粉燃烧特性的影响及动力学研究

 采用热分析技术,研究了CaO、Fe2O3、MgO和MnO2 4种催化剂对精煤和瘦煤燃烧特性的影响,以及非等温燃烧条件下,催化剂对燃烧反应动力学参数的影响。研究表明：当加入量为1%时,4种催化剂都能降低精煤和瘦煤的初始燃烧温度,其中CaO对煤粉的催化助燃效果最为显著。同为过渡金属氧化物,当加入量小于2%时,MnO2降低两种煤粉初始燃烧温度的效果要好于Fe2O3;当加入量为2%时,MnO2降低两种煤粉初始燃烧温度的作用减弱,比Fe2O3的作用?睿尤胧菝菏匝保孟窒笥任飨浴?种催化剂都能降低精煤和瘦煤在第1反应阶段的活化能,其中CaO表现出的助燃效果最好;在第2反应阶段,CaO对精煤的催化燃烧作用最好,而4种催化剂对瘦煤的催化燃烧作用不明显。     

煤粉高速加热条件下的快速热分解

高炉喷吹煤粉和熔融还原铁浴粉煤气化等高速加热条件下,快速热分解是第一步。为研究1160-1750℃温度条件的这一过程,作者用等离子体加热的实验装置,加热速度可达4.3×10³-2.4×10⁴K/s。实验表明增加温度可明显改善烟煤的快速热分解过程,而旦效果比无烟煤明显得多;但气氛对快速热分解过程的影响不太明显。进而说明了铁浴气化粉煤和氧化介质可分开吹入,有利于控制喷嘴前端过热并减少金属蒸发后进入产品气体之中。     

煤粉富氧燃烧特性及动力学分析

 利用热分析法研究了富氧条件下高炉喷吹煤粉的燃烧特性。结果表明,富氧气氛可以改善煤粉燃烧特性,使煤粉着火点、失重峰提前,失重峰值增大,燃尽温度降低,综合燃烧特性指数明显提高,燃烧特性得到改善。当氧的体积分数小于40%时,煤粉燃烧特性改善幅度较大;氧的体积分数大于40%时,煤粉燃烧特性改善趋势变缓。同时采用非等温模型Flynn-Wall-Ozawa(FWO)对富氧之后煤粉燃烧过程进行动力学分析,当氧的体积分数由21%增加到100%,煤粉燃烧活化能从95. 15kJ·mol-1增加到169. 99kJ·mol-1。     

提高预热煤粉燃烧率的机制

 以邯郸钢铁公司2种高炉喷吹用煤粉作为原料,用马弗炉进行预热,测定不同温度预热后的失重率和燃烧率,并采用扫描电镜（SEM）观察预热后煤粉表面结构的变化。试验结果表明,烟煤150℃预热时的失重率为512%,且随着预热温度升高,煤粉的失重率增加,预热温度300℃时失重率可达到17.24%。无烟煤预热后失重率变化不大,预热温度为300℃时失重率仅为5.66%。预热后煤粉燃烧率明显升高。300℃预热条件下的烟煤燃烧率为89.74%,相对于原煤提高了15.67%,无烟煤燃烧率为85.19%,相对于原煤提高了24.80%。预热后煤粉表面结构发生了明显变化,层状和孔隙结构增加,从而提高了煤粉的燃烧率,为提高预热煤粉的燃烧率提供了理论基础。     

利用热重法研究混煤的燃烧

 为了研究混煤的燃烧特点,利用热重法研究了5个单种煤和4个混煤试样燃烧至不同温度时的燃烧率。方法是在热天平中将煤粉试样加热至完全燃烧,根据得到的TG曲线计算燃烧至不同温度时煤粉已燃的可燃值与全部可燃值之比,即燃烧率。结果表明,这些混煤试样的实测燃烧率大于加权燃烧率。动力学计算结果表明,混煤燃烧的活化能低于无烟煤和贫煤而更接近烟煤。当神府烟煤的质量分数在20%~40%时,对混煤燃烧的促进作用最为显著。     

高炉采用氧煤燃烧器后回旋区煤粉燃烧过程的数值模拟

针对高炉风口前回旋区内氧煤燃烧器喷入煤粉燃烧的过程，应用数值模拟方法对氧煤燃烧器在不同喷煤粉量和氧浓度条件下的燃烧过程进行了计算机数值模拟。结果表明，高炉风口产生的回旋区流场及温度场有利于煤粉的燃烧，而氧浓度大则有利于煤粉较早着火及较高的燃烬率。     

基于二维数值模拟的煤粉燃烧性能的研究

运用数值模拟的方法,建立燃烧炉内煤粉燃烧过程的二维数学模型,对两种混煤粉和新钢高炉现用喷吹煤粉在燃烧炉内的燃烧特性进行了模拟,分别得到了两种混煤及新钢高炉喷吹煤粉在燃烧炉内燃烧形成的温度场和焦炭分布规律。结果表明：两种混煤的燃烧性能明显好于新钢高炉喷吹煤粉。采用热重法测得3种煤的燃烧率和与CO2的反应性,得出了与模拟结...     

CeO2及其复合催化剂对煤粉燃烧效率的影响

 利用热重分析法研究了稀土氧化物CeO2和其复合催化剂对煤粉燃烧特性的影响。研究了稀土氧化物及其复合催化剂的添加量、配比对煤粉燃烧特性的影响。结果表明：CeO2可以促进烟煤挥发分析出和燃烧,改善其燃烧性能,CeO2添加质量分数为4%时其催化效果最为显著;不同催化剂对无烟煤燃烧的催化效果各异,MnO2有利于挥发分析出,而CeO2促进了残碳的燃烧,其催化作用不同于烟煤;Ce-Fe-Mn系复合催化剂催化效果优于单组分催化剂,其中CeFeMn(3∶1∶1)的催化效果最佳。利用Coats-Redfern动力学模型分析了煤粉燃烧活化能、指前因子等动力学参数,添加CeFeMn(3∶1∶1)的煤粉反应速率常数较大,催化效果显著。     

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Experiments of combustion and granularity analysis as well as infrared spectroscopy were carried out on the investigation of raw and microwave irradiated pulverized coal (PC). It is indicated in the results that combustion properties of PC under different heating rates are ameliorated after irradiation. Meanwhile, a small decrease in granularity of PC is noticed after microwave treatment, which can prove to be invalid in optimizing the combustion performance of PC in the combustion of devolatilized PC. Simultaneously, radicals of high activity in PC are found to be increased, namely the superior combustion of irradiated PC is due to the activation of volatiles by microwave. Flynn-Wall-Ozawa (FWO) model is adopted to investigate the kinetics of PC combustion, it is indicated that the activation energy of irradiated PC is lower than that of raw PC under the conversion rate of 50%. After microwave treatment, the activation energy of Yungang and Yangquan PC is reduced by 20. 37 and 26. 91J??mol-1 respectively at the conversion rate of 20%. However, the difference in activation energy between raw and irradiated PC is reduced with the increasing of conversion rate. The activation energy of Yungang and Yangquan irradiated PC respectively returns to the level of raw PC at conversion rate of 50% and 60%. When conversion rate of two PC exceeds this level, the activation energy of irradiated PC becomes slightly higher than that of raw PC while the extent was not that significant.     

煤粉在直吹管内燃烧行为的数值模拟

 建立了直吹管内气固流动、传热和煤粉燃烧的数学模型,基于实际高炉工艺参数,借助商业软件通过数值模拟的方法研究了直吹管内的气体成分和温度变化,并重点考察了煤粉粒径、鼓风含氧量和鼓风温度等操作参数对煤粉燃尽率的影响。研究结果表明：减小粒径、增加含氧量、提高鼓风温度都可以使煤粉在直吹管内的燃尽率得到提高。煤粉在直吹管内的燃烧行为以挥发分的脱除为主,该过程对温度敏感,而对氧气浓度不敏感。这一结论与前人在回旋区内得到的模拟结果相反。因此在研究变量对喷吹煤粉燃尽率的影响时,模拟区域应同时包含直吹管和回旋区。     

Combustion Property and Kinetic Modeling of Pulverized Coal Based on Non-isothermal Thermogravimetric Analysis

Non-isothermal combustion kinetics of two kinds of low volatile pulverized coals （HL coal and RU coal） were investigated by thermogravimetrie analysis. The results show that the combustibility of HL coal was better than that of RU coal, and with increasing heating rate, ignition and burnout characteristics of pulverized coal were improved. The volume model （VM）, the random pore model （RPM）, and the new model （NEWM） in which the whole combustion process is considered to be the overlapping process of volatile combustion and coal char combustion, were used to fit with the experimental data. The comparison of these three fitted results indicated that the combustion process of coal could be simulated by the NEWM with highest precision. When calculated by the NEWM, the activation energies of volatile combustion and coal char combustion are 130.5 and 95.7 kJ · mol^-1 for HL coal, respectively, while they are 114.5 and 147.6 kJ ·mol^-1 for RU coal, respectively.     

Radiant Image Simulation of Pulverized Coal Combustion in Blast Furnace Raceway

The numerical si mulation of combustion processhas been performed[1,2],but thereis still no suitabletemperature measuring technique for three-di men-sional analysis[3].Nowadays,the radiant i mage pro-cessing technique has been developed at home and a-broad[4,5].The relation between radiant i mage andpulverized coal combustion process in blast furnaceraceway was studiedin present work withthis meth-od to examine three-di mensional temperature distri-butionin blast furnace raceway.1Radiant Image…     

O2/CO2气氛下煤粉燃烧数值模拟

采用CFD技术对不同气氛下煤粉燃烧过程进行了研究。用Fluent软件模拟不同工况下煤粉燃烧,获得煤粉燃烧的一些基础性参数,为实际应用提供相应的指导;建立包括气相湍流流动、气固之间传热、煤挥发分析以及燃烧等过程在内的三维数学模型;将不同气氛下煤粉燃烧的特性进行对比,研究气氛变化对燃烧的影响规律。     

Mechanism of Effect of Microwave Modification on Pulverized Coal Combustion Properties

The mechanism of microwave modification on facilitating the combustion properties of pulverized coal(PC)was investigated.Experimental researches on granularity and functional group as well as combustion properties of PC before and after modification were carried out.Micromorphology observation indicated that the size of PC particles was relatively small,which was in accordance with the results of granularity analysis of PC.FT-IR(Fourier-transform infrared)spectra of two PCs indicated that the proportion of the functional groups with high activity increased after microwave irradiation.Furthermore,no valid effect of microwave was found on carbon matrix except small variations in PC particle size,which only led to subtle improvement in combustion of residual coke.Activation energies of Yungang and Yangquan PCs in temperature zone between 450-650℃ were reduced by 12.00%and 10.13%,respectively,which meant that microwave modification might effectively facilitate the combustion properties of PC.Nevertheless,decrease in activation energies of residual cokes was 3.56%and 3.67%respectively,which was subtle and can be regarded as the result of smaller particle size produced by microwave irradiation.     

O_2/CO_2气氛下煤粉燃烧特性模拟研究

针对煤粉燃烧器燃烧工况,采用Fluent软件,探索辐射模型、气氛和煤粉粒径对煤粉燃烧过程的影响及污染物生成情况。结果表明:采用DO+WSGG模型时,煤粉的燃烧温度有所降低;跟空气气氛相比O_2/CO_2气氛下煤粉的燃烧温度降低,NO的量也降低;氧浓度增大,煤粉燃烧的温度峰值增加;随着超细煤粉混合比的增加,燃烧高温区而向前移。     

Gas-Particle Flow and Combustion Characteristics of Pulverized Coal Injection in Blast Furnace Raceway

The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles,as well as components concentration and temperature distribution of coal gas in the process of pulverized coal injection of blast furnace raceway.The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere,and the residence time of coal particles in the region of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary.The pressure is the highest at the bottom of raceway and the maximal temperature is about 2423 K.The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3×10-4 kg/s.     

单颗粒煤粉燃烧数学模型

建立了单颗粒煤粉燃烧数学模型，并模拟了不同条件下煤粉的燃烧过程。模拟给出了煤粒表面温度随燃烧时间的变化关系，燃烧率与燃烧时间及煤粒直径的关系，煤粒周转膜层中气相成分及温度的分布等。     

An Improved Model for Char Combustion in Blast Furnace Pulverized Coal Injection

An improved char combustion model has been presented, taking additional consideration of the influence of the finite‐rate heterogeneous reduction and oxidation. Explicit algebraic expressions for the overall rate of combustion, the surface temperature of the particle, and the gas temperature at the flame sheet are given in the model. The transition between various limiting combustion conditions was analysed using the improved model. A Fourier Transform Infrared spectroscopy (FTIR) system was established to measure the particle temperatures. Rational agreement was achieved between the predictions and the data from the present work and the literatures. Compared with the single‐film model, the predictions of particle temperature by the improved model were in much better agreement with those predicted by the rigid continuous‐film model, while the calculation time for the improved model is 100,000 times faster than that using the continuous‐film model. It is shown that the present model could not only be integrated easily into comprehensive computing codes for industrial pulverized coal flame, but also considers most of the physico‐chemical processes involved and is then accurate enough for engineering applications.     

煤粉在Corex熔融气化炉内的燃烧行为研究

Corex熔融还原炼铁是新兴的炼铁工艺,虽然它可以不用或少用焦炭冶炼铁水,但是需要用块煤来生产.为了替代一部分块煤以及充分利用产生的煤粉,提出了往熔融气化炉喷吹煤粉的方法.Corex喷煤可以借鉴高炉喷煤的经验,但是它们之间有一些区别.采用热态模拟的方法对煤粉在Corex熔融气化炉内的燃烧行为进行研究,得到煤的粒度、挥发分含量以及喷吹位置和CO浓度等因素对煤粉燃烧率和气化率的影响规律.实验将为Corex喷煤技术的开发提供必要的理论支持.     

鞍钢高炉喷吹煤粉合理配煤的试验研究

介绍了国家“八五”重点攻关课题“氧煤强化炼新工艺研究”中高炉吹烟煤、无工混配煤的实验室研究及工业试验室研究应用情况,探讨了高炉喷吹煤粉的合理配煤结构。在鞍钢生产条件下,对于喷煤量１００ｋｇ／ｔ铁以下,不富氧成低富氧的１０００ｍ＾３级高炉,所喷混煤的挥发分控制在１８％左右比较合适。