振动流化床干燥分选细粒褐煤试验研究

发布时间：2018-04-05 07:03

本文选题：褐煤　切入点：振动流化床　出处：《中国矿业大学》2016年硕士论文

【摘要】：近年来随着中国煤炭资源持续开采,优质煤炭资源枯竭,煤炭行业整体经济效益下降,且目前普遍采用的湿法选煤工艺具有成本高、分选褐煤易泥化等缺点。另外褐煤本身煤化程度低,具有水分高、密度小、挥发分高、不粘结、化学反应性强、热稳定性差、发热量低、易风化和自燃、难以洗选和储存,使褐煤的利用受到很大限制。与此同时一批新建煤化工项目因褐煤价格相对低廉而纷纷改用褐煤作为原料,使褐煤资源需求量大幅上升,褐煤高效降灰干燥提质逐渐受到重视。本文通过实验利用振动流化床在低流化气速下对褐煤进行干燥之后进行分选实验,为褐煤高效节能利用提供一定的技术支持。本文首先对比了褐煤与一种在空气重介质流化床中分选效果较好的焦煤在流化床中流化特性与分选特性差异。实验过程中利用压力波动采集与处理设备、高速动态摄影机等设备对两种煤颗粒在流化床中运动规律、床层流化稳定性、气泡的生成与运动轨迹等进行分析。结果表明煤粒种类、入料量、粒度、密度以及是否在磁铁矿粉中加入煤粉等因素通过影响流化床流化特性与床层密度与压力波动稳定性最终对分选效果产生重要影响。在传统的磁铁矿粉基础上加入10%的0.5-0.9mm褐煤粉可有效降低分选床层的密度,实现低密度褐煤的分选。由于褐煤原煤密度较轻且具有一定水分,分选效果劣于焦煤,但可以起到一定的排矸效果。针对-3+1mm细粒褐煤相对易流化,干燥过程中利用振动流化床直接对其进行干燥而不外加重介质。通过实验分析了振幅、频率、风速、温度、粒度、加介量等各因素对干燥-3+1mm细粒褐煤的影响,发现振动能量的加入使得颗粒在流化床中即使处于临界流化风速以下,颗粒之间也可产生明显的返混,利于褐煤干燥的高效化与节能化。随着振动强度增加干燥速率变大,但振幅与频率对干燥速率的影响不同:当二者均较大时增大振幅对于干燥速率的提升效果明显高于增大频率的提升效果,理想的振动强度应保持温和频率的同时适当增大振幅,本实验最佳振幅与频率分别为15Hz、25mm;温度与粒度对干燥的影响趋势恰好相反:温度越高干燥速率越大,当温度T=140℃时为最佳干燥温度,高于此值温度的提升对干燥效果的提升不明显;另外振动流化床干燥褐煤粒度较大时效果不佳,宜将粒径限制在小于3mm范围内。由于-3+1mm褐煤灰分较高,干燥后不适合直接利用,且单纯煤进行分选时效果不佳,因此对利用振动重介质流化床对干燥后褐煤进行分选,结果表明当N=1.40左右时达到最佳分选效果,此时精煤灰分可达10%左右。通过实验研究了在振动重介质流化床中-13+6mm褐煤的干燥特性,结果表明重介质的加入对较粗煤粒起到润滑作用,使床体内颗粒更加活跃增大颗粒返混碰撞机会增大。另外较细的加重质在流化后填充在较大煤粒之间的缝隙中增大接触传热,可大大提高较粗煤粒特别是粒度在6mm以上煤粒的干燥效果。另外介质的润滑作用可使床层在较高的频率下继续增大时对干燥速率的提升效果依然明显,最佳振动频率与振幅分别定为25Hz、2.5mm。除此之外,其他各因素对振动重介质流化床中干燥较粗粒级褐煤相似。在上述研究基础上,结合数据处理拟合软件与几种典型的干燥模型对振动流化床与振动重介质流化床干燥两种不同粒径煤粒进行了干燥动力学分析;对比了临界流化条件以下与传统的高气速下干燥以及加介质与不加介质条件下有效扩散系数与活化能的差异。结果表明:Modified Henderson and Pabis模型拟合结果与实际实验符合程度更高,其相关系数在各模型中最接近于1,且均方差RMSE最小为最佳干燥模型。在其他条件相同时,流化数为0.9与振动重介质流化床干燥褐煤活化能分别小于流化数为1.8与振动流化床干燥褐煤条件下活化能。低流化风速结合振动能量的给入可以达到较好的干燥效果又大幅度降低了能耗,同时磁铁矿粉对褐煤特别是较粗粒级褐煤的干燥起到大幅度促进作用。
[Abstract]:In recent years, with the continuous exploitation of China coal resources, coal resources depletion, decrease the overall economic benefits of the coal industry, is currently widely used wet coal preparation process and high cost of sorting, lignite easy to slime and other shortcomings. In addition low rank lignite itself, with high moisture content, low density, high volatilization, no adhesion, chemical reaction strong, poor thermal stability, low calorific value, easy weathering and spontaneous combustion, it is difficult to wash and storage, so that the utilization of lignite is very limited. At the same time a number of new coal chemical projects for lignite prices relatively low have to use lignite as raw material, the lignite resources demand rose sharply, reducing ash lignite drying and upgrading gradually attention. Through the experiment using vibrating fluidized bed gas at low flow velocity of lignite drying separation experiment, for the efficient utilization of lignite to provide technical support to certain Holding. This paper first compared the separation effect of lignite and a heavy medium in the air in a fluidized bed better in coking coal characteristics and separation characteristics of fluidized bed pressure fluctuation difference. Acquisition and processing equipment used in the course of the experiment, the movement law of two kinds of coal in fluidized bed of particles on the high-speed dynamic camera and other equipment, fluidization stability, bubble the generation and motion trajectory were analyzed. The results show that the coal particle type, feeding amount, particle size, density and whether the magnetite powder added in pulverized coal and other factors affected by the fluidization characteristics and bed density and pressure fluctuation stability have an important influence on the separation effect. The addition of 10% traditional magnetite powder on the basis of 0.5-0.9mm brown coal can effectively reduce the sorting of bed density, low density to achieve separation. The density of raw coal lignite is light and has certain water separation efficiency The fruit is inferior to the coking coal, but can play a certain effect. The gangue for -3+1mm fine grained lignite is relatively easy to flow, the drying process by vibrating fluidized bed directly on the dry rather than aggravating medium. Through the experimental analysis of amplitude, frequency, wind speed, temperature, particle size, and effects of various factors on the drying medium plus -3+1mm fine grained lignite, found that adding the vibration energy of the particles in the fluidized bed even at the critical fluidization velocity, particles can produce obvious backmixing, conducive to efficient and energy-saving of lignite drying. With the vibration intensity increase drying rate increases, but the influence of amplitude and frequency of different drying rate: when two both large amplitude for the drying rate was significantly higher than that to enhance the effect of increased frequency to enhance the effect of vibration intensity, the ideal should maintain a moderate frequency and increasing the amplitude of the vibration experiment, the best Amplitude and frequency are respectively 15Hz, 25mm; temperature and particle size on the influence of drying temperature is the opposite trend: high drying rate increases, when the temperature is T=140 DEG C for optimum drying temperature, the temperature is greater than the value to enhance the drying effect is not obvious; the other vibration fluidized bed drying of lignite particle size larger effect is poor. It should be limited in size less than 3mm. Because -3+1mm lignite ash is higher, after drying is not suitable for direct use, and simple coal separation effect is poor, so the vibration of heavy medium fluidized bed drying of lignite were selected, and the results show that when the N=1.40 is about to achieve the best separation effect, about the coal ash up to 10%. The drying characteristics of heavy medium in vibration fluidized bed -13+6mm lignite are studied through experiments, the results show that the heavy medium added to thick coal particle lubricates the bed of particles in the more Increase of active particle back mixing collision probability increases. In addition increase the quality is fine in the flow after filling increases the contact heat transfer in a large gap between the coal particles, which can greatly improve the special thick coal particle is the drying effect of coal particle size in the 6mm above. In addition, medium lubrication can make the bed to continue to increase at higher the frequency of the drying rate increase is still obvious, the best vibration frequency and amplitude were set at 25Hz 2.5mm., in addition, the other factors on the vibration of heavy medium fluidized bed drying of relatively coarse grained lignite. On the basis of these studies, combined with data processing software and several typical drying model fitting on vibration and vibration fluidized bed dense medium fluidized bed drying of two different particle size of coal particles were drying kinetics analysis; comparison of critical fluidization conditions following with the traditional high gas velocity and medium with and without drying The effective diffusion coefficient of variation and the activation energy of the medium conditions. The results show that with a higher degree of Modified Henderson and Pabis model fitting with the experimental result, the correlation coefficient in the model most close to 1, and the minimum mean square error RMSE as the best drying model. In other conditions are the same, the flow number is 0.9 vibration and heavy medium fluidized bed drying lignite activation energy were less than the flow number is 1.8 and vibration fluidized bed drying lignite under the condition of low activation energy. The flow of the wind speed with the vibration energy input can achieve good drying effect and greatly reduces the energy consumption at the same time, the magnetite powder of lignite is relatively coarse grained lignite drying to greatly promote role.

【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD94

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