本文選題：濃相氣固流化床 + 床層高度��； 參考：《中國(guó)礦業(yè)大學(xué)》2017年碩士論文

【摘要】：在濃相氣固流化床中,流化床床層高度是流態(tài)化技術(shù)的一個(gè)重要參數(shù),直接影響著床層的流化行為。對(duì)于流化床選煤技術(shù)來(lái)說(shuō),床層太淺,分選空間不夠,分層不好,影響分選效果;床層太高,易產(chǎn)生大氣泡和騰涌現(xiàn)象,影響流化床穩(wěn)定。而床層高度對(duì)于處于分選下限的細(xì)粒煤的影響較大,由于床層高度的增加,必然會(huì)影響分選下限,因此本文著重于探究濃相氣固流化床中床層高度對(duì)分選下限的影響。從流態(tài)化角度出發(fā),本試驗(yàn)以床層密度分布標(biāo)準(zhǔn)差、不均勻度為評(píng)價(jià)指標(biāo),探究了加重質(zhì)顆粒大小模型、布風(fēng)板壓降、介質(zhì)二維組分和流化數(shù)等因素對(duì)流態(tài)化的影響,并在確定以上因子為最佳條件的基礎(chǔ)上,進(jìn)一步探究不同床層高度下的流化特性、空隙率特性和密度空間分布,并揭示了不同床層高度下穩(wěn)定流態(tài)化區(qū)域的變化特征,得出流化穩(wěn)定區(qū)域S與床層高徑比H/D的關(guān)系模型:從分選角度出發(fā),本試驗(yàn)首先探索了各粒度級(jí)煤樣的最大入料率rmax與煤樣平均粒度級(jí)(?)的關(guān)系模型:rmax=0.004369(?)+0.05350基于此關(guān)系模型的斜率數(shù)值上,確定其實(shí)際入料率。在不同床層高度下、不同流化數(shù)下,分別對(duì)-10+8mm、-8+6mm、-6+5mm、-5+4mm、-4+3mm、-3+2mm、-2+1mm和-1+0.5mm八個(gè)粒度級(jí)煤樣進(jìn)行了分選試驗(yàn)。以灰分離析度和可能偏差為評(píng)價(jià)指標(biāo),得出相關(guān)結(jié)論:首先,在較大粒度級(jí)入料時(shí),其分選效果在較大流化數(shù)下其分選效果更佳;而在較小粒度級(jí)入料時(shí),其分選效果在較小流化數(shù)下其分選效果更佳。其次,在同一床層高度下,分選效果隨入料煤樣粒度級(jí)的減小而變差,較小粒度級(jí)的分選效果不理想。再次,隨著濃相氣固流化床床層高度的增大,各粒度級(jí)入料煤樣的分選效果在變好,當(dāng)床層高度增大到240mm時(shí),其分選下限能達(dá)到-4+3mm粒度級(jí)。從次,從混合粒度級(jí)煤樣入料的分選效果來(lái)看,與單粒級(jí)煤樣入料分選效果相似,其粒度級(jí)、流化數(shù)與床層高度的關(guān)系與單粒級(jí)煤樣入料的分選結(jié)果基本一致。最后,在較短的分選時(shí)間內(nèi),高床層流化床的分選效果不如低床層床,隨著時(shí)間的增加,高床層床和低床層床的分選效果都開(kāi)始變好,但是高床層床的變好幅度大于低床層床,高床層床的分選效果從不如低床層床,變化為超過(guò)低床層床的分選效果。從分析機(jī)理的角度出發(fā),氣速-壓降、氣固兩相模型、散式流化區(qū)域和顆粒沉降理論等流態(tài)化理論對(duì)本試驗(yàn)中的流化及分選過(guò)程進(jìn)行了闡明,并且從高速動(dòng)態(tài)分析上對(duì)該結(jié)論進(jìn)行了驗(yàn)證。
[Abstract]:The fluidized bed height is an important parameter of fluidization technology in dense phase gas-solid fluidized bed, which directly affects the fluidization behavior of fluidized bed. For fluidized bed coal preparation technology, the bed is too shallow, the separation space is not enough, the stratification is not good, and the separation effect is affected. The bed height has a great influence on the fine coal at the lower limit of separation. Because of the increase of bed height, it will inevitably affect the lower limit of separation. Therefore, this paper focuses on the study of the influence of bed height on the lower limit of separation in the dense phase gas-solid fluidized bed. From the point of view of fluidization, based on the standard deviation and non-uniformity of bed density distribution, the effects of aggravation particle size model, pressure drop of air distribution plate, two-dimensional composition of medium and fluidization number on fluidization were investigated. On the basis of determining the above factors as the best conditions, the fluidization characteristics, voidage characteristics and density spatial distribution at different bed heights are further explored, and the variation characteristics of stable fluidized areas at different bed heights are revealed. The relationship model between S and H / D ratio of bed height to diameter in fluidized stable region is obtained. From the separation point of view, the maximum feed rate (rmax) of coal samples of different granularity grades and the average grain size of coal samples are explored in this experiment. Based on the slope value of the model, the actual feed rate is determined. Under different bed height and different fluidization number, the coal samples of -108 mm ~ (-6) -8 ~ (6) mm ~ (-6) ~ (-5 mm) ~ (-54) mm ~ (-1) ~ (-3) ~ (-2) mm ~ (-2) 1mm and 1 ~ (-1) 0.5mm were separated from each other. Taking the degree of ash segregation and possible deviation as the evaluation index, the relevant conclusions are drawn: firstly, the separation effect is better under the larger fluidization number, but at the smaller granularity grade, the separation effect is better. The separation effect is better under the smaller fluidization number. Secondly, at the same bed height, the separation effect becomes worse with the decrease of the granularity level of the coal sample, and the separation effect of the smaller granularity level is not ideal. Thirdly, with the increase of the bed height of dense phase gas-solid fluidized bed, the separation effect of each granularity grade coal sample is becoming better. When the bed height increases to 240mm, the lower limit of separation can reach -4 3mm granularity level. From the point of view of the separation effect of mixed granularity grade coal sample, the separation effect is similar to that of single grain grade coal sample, and the relation among granularity, fluidization number and bed height is basically consistent with the separation result of single grain grade coal sample. Finally, in a short separation time, the separation effect of high bed fluidized bed is not as good as that of low bed. With the increase of time, the separation effect of high bed and low bed begin to improve, but the better range of high bed is larger than that of low bed. The separation effect of high bed is not as good as that of low bed, and the separation effect of high bed is higher than that of low bed. From the point of view of analysis mechanism, the fluidization and separation process in this experiment are expounded by the fluidization theory, such as gas-velocity pressure drop, gas-solid two-phase model, dispersed fluidization region and particle settlement theory. The conclusion is verified by high-speed dynamic analysis.
【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】：2017
【分類號(hào)】：TD94

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