本文選題：空氣重介質(zhì)流化床　切入點(diǎn)：二元加重質(zhì)　出處：《中國(guó)礦業(yè)大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：空氣重介質(zhì)流化床能夠?qū)崿F(xiàn)對(duì)-50+6 mm粒級(jí)煤炭的有效分選,但傳統(tǒng)的空氣重介質(zhì)流化床使用單一加重質(zhì)(除自生介質(zhì)外),只能形成單一且較高的分選密度。為降低床層分選密度,實(shí)現(xiàn)物料的有效分選,將低密度石英砂和高密度磁鐵礦粉作為混合加重質(zhì)給入到空氣重介質(zhì)流化床中,形成較低密度的床層,擴(kuò)寬氣固流化床分選密度、粒度下限,為實(shí)現(xiàn)低密度煤炭的有效分選提供理論基礎(chǔ)。試驗(yàn)中石英砂物料粒度組成為0.25-0.35 mm,磁鐵礦粉粒度組成為0.15-0.2mm。選擇兩類(lèi)介質(zhì)顆粒粒度組成為窄粒級(jí),不僅考慮石英砂顆粒與磁鐵礦粉顆粒存在較大的密度差異,還考慮使整個(gè)床層形成一個(gè)相對(duì)穩(wěn)定的低密度分選介質(zhì)層,這不僅有利于低密度煤炭顆粒的分選,更有利于阻止高密度煤炭顆粒的錯(cuò)配,加快各密度級(jí)煤炭顆粒的分層,改良?xì)夤塘骰卜诌x效果。對(duì)于床層介質(zhì)流化質(zhì)量的評(píng)價(jià)從兩個(gè)方面考慮。首先是床層密度的分布規(guī)律性,包括床層密度沿床高軸向及床層水平面徑向的空間分布。其次是床層密度的均勻穩(wěn)定性,床層密度以各組測(cè)壓點(diǎn)測(cè)量計(jì)算的密度值作為樣本,用樣本標(biāo)準(zhǔn)離差Δ表征床層密度的均勻穩(wěn)定性。由試驗(yàn)結(jié)果可知,二元混合加重質(zhì)床層密度分布受石英砂含量、流化數(shù)及靜床高的影響而呈現(xiàn)不同的分布規(guī)律。當(dāng)石英砂含量介于5%-20%之間時(shí),當(dāng)流化數(shù)1.0≤N≤1.3時(shí),床層密度整體分布不均,波動(dòng)較大。當(dāng)石英砂含量大于25%時(shí),床層密度沿豎直方向自下向上呈逐漸降低的變化趨勢(shì)。不同組成加重質(zhì)床層密度分布標(biāo)準(zhǔn)差變化規(guī)律也不盡相同。當(dāng)加重質(zhì)中石英砂含量較低(ω=5%-15%)時(shí),床層密度標(biāo)準(zhǔn)差隨流化數(shù)的增大而減小;當(dāng)加重質(zhì)中石英砂含量增大(ω=20%-30%)時(shí),床層軸向或徑向密度標(biāo)準(zhǔn)差均較大,床層受氣速影響,床層密度波動(dòng)較大,床層穩(wěn)定性差,為了使床層密度均勻分布,需控制試驗(yàn)流化數(shù)N=1.4-1.6的范圍。根據(jù)理論推導(dǎo)的計(jì)算床層密度的公式,測(cè)定相關(guān)試驗(yàn)參數(shù),得出二元混合加重質(zhì)流化床床層密度與石英砂含量、床層流化數(shù)的數(shù)學(xué)關(guān)聯(lián)式,得出流化床床層密度模型,并與實(shí)測(cè)值比較,檢驗(yàn)其適應(yīng)性。試驗(yàn)中選擇-13+6 mm粒級(jí)中等灰分等級(jí)的焦煤作為分選研究對(duì)象。分選結(jié)果顯示,對(duì)試驗(yàn)原煤的分選可能偏差為0.085 g/cm~3。當(dāng)使用單一加重質(zhì)分選時(shí),分選所得精煤灰分偏高;當(dāng)使用二元混合加重質(zhì)分選時(shí),隨石英砂含量的增加,床層分選所得精煤產(chǎn)物灰分呈逐漸降低的變化規(guī)律,精煤灰分最低可達(dá)8.76%。
[Abstract]:The air heavy medium fluidized bed can realize the effective separation of -506mm granular coal. However, the traditional air-heavy medium fluidized bed uses a single aggravation (except for the autogenous medium, which can only form a single and high separation density.) in order to reduce the separation density of bed and realize the effective separation of materials, The low density quartz sand and high density magnetite powder are used as mixed additives to be fed into the air heavy medium fluidized bed to form a lower density bed, and the separation density and the lower particle size of the gas-solid fluidized bed are widened. In order to realize the effective separation of low density coal, the particle size composition of quartz sand and magnetite powder is 0.25-0.35mm and 0.15-0.2mm. Not only the density difference between quartz sand particles and magnetite particles is considered, but also the formation of a relatively stable low density separation medium layer in the whole bed is considered, which is not only beneficial to the separation of coal particles with low density. It is more helpful to prevent the mismatch of high-density coal particles and accelerate the stratification of coal particles of different density levels. Improved separation effect of gas-solid fluidized bed. The evaluation of fluidization quality of bed media is considered from two aspects. First, the distribution regularity of bed density, It includes the spatial distribution of bed density along the axial direction of bed height and the radial direction of bed horizontal plane. Secondly, the uniform stability of bed density. The uniform stability of bed density is characterized by the standard deviation 螖 of samples. From the experimental results, it is known that the density distribution of binary mixed aggravation bed is affected by the content of quartz sand. When the content of quartz sand is between 5% and 20%, when the fluidization number is 1.0 鈮，

本文編號(hào)：1576562