本文選題：褐煤　切入點(diǎn)：振動(dòng)流化床　出處：《中國(guó)礦業(yè)大學(xué)》2016年碩士論文

【摘要】：近年來(lái)隨著中國(guó)煤炭資源持續(xù)開(kāi)采,優(yōu)質(zhì)煤炭資源枯竭,煤炭行業(yè)整體經(jīng)濟(jì)效益下降,且目前普遍采用的濕法選煤工藝具有成本高、分選褐煤易泥化等缺點(diǎn)。另外褐煤本身煤化程度低,具有水分高、密度小、揮發(fā)分高、不粘結(jié)、化學(xué)反應(yīng)性強(qiáng)、熱穩(wěn)定性差、發(fā)熱量低、易風(fēng)化和自燃、難以洗選和儲(chǔ)存,使褐煤的利用受到很大限制。與此同時(shí)一批新建煤化工項(xiàng)目因褐煤價(jià)格相對(duì)低廉而紛紛改用褐煤作為原料,使褐煤資源需求量大幅上升,褐煤高效降灰干燥提質(zhì)逐漸受到重視。本文通過(guò)實(shí)驗(yàn)利用振動(dòng)流化床在低流化氣速下對(duì)褐煤進(jìn)行干燥之后進(jìn)行分選實(shí)驗(yàn),為褐煤高效節(jié)能利用提供一定的技術(shù)支持。本文首先對(duì)比了褐煤與一種在空氣重介質(zhì)流化床中分選效果較好的焦煤在流化床中流化特性與分選特性差異。實(shí)驗(yàn)過(guò)程中利用壓力波動(dòng)采集與處理設(shè)備、高速動(dòng)態(tài)攝影機(jī)等設(shè)備對(duì)兩種煤顆粒在流化床中運(yùn)動(dòng)規(guī)律、床層流化穩(wěn)定性、氣泡的生成與運(yùn)動(dòng)軌跡等進(jìn)行分析。結(jié)果表明煤粒種類(lèi)、入料量、粒度、密度以及是否在磁鐵礦粉中加入煤粉等因素通過(guò)影響流化床流化特性與床層密度與壓力波動(dòng)穩(wěn)定性最終對(duì)分選效果產(chǎn)生重要影響。在傳統(tǒng)的磁鐵礦粉基礎(chǔ)上加入10%的0.5-0.9mm褐煤粉可有效降低分選床層的密度,實(shí)現(xiàn)低密度褐煤的分選。由于褐煤原煤密度較輕且具有一定水分,分選效果劣于焦煤,但可以起到一定的排矸效果。針對(duì)-3+1mm細(xì)粒褐煤相對(duì)易流化,干燥過(guò)程中利用振動(dòng)流化床直接對(duì)其進(jìn)行干燥而不外加重介質(zhì)。通過(guò)實(shí)驗(yàn)分析了振幅、頻率、風(fēng)速、溫度、粒度、加介量等各因素對(duì)干燥-3+1mm細(xì)粒褐煤的影響,發(fā)現(xiàn)振動(dòng)能量的加入使得顆粒在流化床中即使處于臨界流化風(fēng)速以下,顆粒之間也可產(chǎn)生明顯的返混,利于褐煤干燥的高效化與節(jié)能化。隨著振動(dòng)強(qiáng)度增加干燥速率變大,但振幅與頻率對(duì)干燥速率的影響不同:當(dāng)二者均較大時(shí)增大振幅對(duì)于干燥速率的提升效果明顯高于增大頻率的提升效果,理想的振動(dòng)強(qiáng)度應(yīng)保持溫和頻率的同時(shí)適當(dāng)增大振幅,本實(shí)驗(yàn)最佳振幅與頻率分別為15Hz、25mm;溫度與粒度對(duì)干燥的影響趨勢(shì)恰好相反:溫度越高干燥速率越大,當(dāng)溫度T=140℃時(shí)為最佳干燥溫度,高于此值溫度的提升對(duì)干燥效果的提升不明顯;另外振動(dòng)流化床干燥褐煤粒度較大時(shí)效果不佳,宜將粒徑限制在小于3mm范圍內(nèi)。由于-3+1mm褐煤灰分較高,干燥后不適合直接利用,且單純煤進(jìn)行分選時(shí)效果不佳,因此對(duì)利用振動(dòng)重介質(zhì)流化床對(duì)干燥后褐煤進(jìn)行分選,結(jié)果表明當(dāng)N=1.40左右時(shí)達(dá)到最佳分選效果,此時(shí)精煤灰分可達(dá)10%左右。通過(guò)實(shí)驗(yàn)研究了在振動(dòng)重介質(zhì)流化床中-13+6mm褐煤的干燥特性,結(jié)果表明重介質(zhì)的加入對(duì)較粗煤粒起到潤(rùn)滑作用,使床體內(nèi)顆粒更加活躍增大顆粒返混碰撞機(jī)會(huì)增大。另外較細(xì)的加重質(zhì)在流化后填充在較大煤粒之間的縫隙中增大接觸傳熱,可大大提高較粗煤粒特別是粒度在6mm以上煤粒的干燥效果。另外介質(zhì)的潤(rùn)滑作用可使床層在較高的頻率下繼續(xù)增大時(shí)對(duì)干燥速率的提升效果依然明顯,最佳振動(dòng)頻率與振幅分別定為25Hz、2.5mm。除此之外,其他各因素對(duì)振動(dòng)重介質(zhì)流化床中干燥較粗粒級(jí)褐煤相似。在上述研究基礎(chǔ)上,結(jié)合數(shù)據(jù)處理擬合軟件與幾種典型的干燥模型對(duì)振動(dòng)流化床與振動(dòng)重介質(zhì)流化床干燥兩種不同粒徑煤粒進(jìn)行了干燥動(dòng)力學(xué)分析;對(duì)比了臨界流化條件以下與傳統(tǒng)的高氣速下干燥以及加介質(zhì)與不加介質(zhì)條件下有效擴(kuò)散系數(shù)與活化能的差異。結(jié)果表明:Modified Henderson and Pabis模型擬合結(jié)果與實(shí)際實(shí)驗(yàn)符合程度更高,其相關(guān)系數(shù)在各模型中最接近于1,且均方差RMSE最小為最佳干燥模型。在其他條件相同時(shí),流化數(shù)為0.9與振動(dòng)重介質(zhì)流化床干燥褐煤活化能分別小于流化數(shù)為1.8與振動(dòng)流化床干燥褐煤條件下活化能。低流化風(fēng)速結(jié)合振動(dòng)能量的給入可以達(dá)到較好的干燥效果又大幅度降低了能耗,同時(shí)磁鐵礦粉對(duì)褐煤特別是較粗粒級(jí)褐煤的干燥起到大幅度促進(jìn)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.

【學(xué)位授予單位】：中國(guó)礦業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TD94

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本文編號(hào)：1713681