本文選題：褐煤　切入點(diǎn)：振動(dòng)重介質(zhì)流化床　出處：《中國礦業(yè)大學(xué)》2015年碩士論文

【摘要】：我國褐煤資源豐富,約占全國煤炭儲量的13%,但其含水率高、熱值低,使褐煤利用效率低,經(jīng)濟(jì)性差,并導(dǎo)致環(huán)境污染。因此,深入研究褐煤干燥及清潔高效利用技術(shù)迫在眉睫。本論文在普通流化床基礎(chǔ)上引入振動(dòng)和重介質(zhì)(磁鐵礦粉),針對褐煤的流化特性、混合度及干燥特性進(jìn)行實(shí)驗(yàn),結(jié)合薄層干燥模型分析干燥過程中有效水分?jǐn)U散系數(shù)、活化能、干燥速率和熱量利用,著重研究了褐煤在振動(dòng)重介質(zhì)流化床中的干燥特性。通過對褐煤與磁鐵礦粉混合物在振動(dòng)流化床中的流化特性及混合度的研究發(fā)現(xiàn),隨著振幅和頻率的增大,床層最小流化氣速先減小后增大;隨著介質(zhì)量的增多,床層最小流化氣速先減小后不變;溫度的升高及褐煤顆粒粒徑的減小也會減小床層最小流化氣速;床高對振動(dòng)重介質(zhì)流化床的最小流化氣速影響不大。床層混合度隨著風(fēng)速和振動(dòng)強(qiáng)度的增大先減小后增大,最后達(dá)到穩(wěn)定的較大值;隨著介質(zhì)量的增多而增大,隨著床高的增高先增大后不變。在80-160℃條件下,對四種狀態(tài)(無振動(dòng)無介質(zhì)、無振動(dòng)加介質(zhì)、加振動(dòng)無介質(zhì)、加振動(dòng)加介質(zhì))進(jìn)行了干燥實(shí)驗(yàn),并對結(jié)果進(jìn)行擬合分析:Midilli-Kucuk模型最適用于描述勝利褐煤的干燥;由于溫度的升高,使褐煤干燥速率增大,有效水分?jǐn)U散系數(shù)增大,其值在7.38×10-9-5.37×10-8 m2/s范圍內(nèi);同時(shí),振動(dòng)和介質(zhì)的加入使活化能減小,四種狀態(tài)下活化能分別30.20KJ/mol、29.40 KJ/mol、30.04 KJ/mol、24.47 KJ/mol。褐煤在振動(dòng)重介流化床的干燥過程中,外水干燥速率受振動(dòng)強(qiáng)度、風(fēng)速、粒徑、溫度及介質(zhì)量的影響較大,受床高的影響較小;內(nèi)水干燥速率受溫度影響最大,受其他因素影響很小。因此,干燥外水適用于中溫高氣速及適量的介質(zhì),干燥內(nèi)水時(shí)適用于高溫低風(fēng)速條件。對干燥過程中熱量衡算發(fā)現(xiàn),水分蒸發(fā)所需要的熱量、顆粒升溫所需熱量以及熱效率均隨著濕含量降低而降低,在濕含量降低到10.11%時(shí),平均熱效率為52.15%,而當(dāng)褐煤濕含量由10.11%至干燥完全,其平均熱效率僅為4.48%;而尾氣溫度隨含濕量降低而升高,尾氣帶走熱量也增大,尾氣中水汽少,因此,在干燥褐煤內(nèi)水時(shí)可考慮循環(huán)使用尾氣,減少能耗。
[Abstract]:China is rich in lignite resources, accounting for about 13% of the national coal reserves, but its high moisture content and low calorific value make lignite use efficiency low, economy poor, and lead to environmental pollution.Therefore, it is urgent to study the drying and clean and efficient utilization of lignite.In this paper, vibration and heavy medium (magnetite powder) are introduced on the basis of ordinary fluidized bed. Experiments on fluidization, mixing degree and drying characteristics of lignite are carried out. The effective moisture diffusion coefficient and activation energy are analyzed in combination with thin-layer drying model.The drying characteristics of lignite in a vibratory heavy medium fluidized bed were studied in terms of drying rate and heat utilization.The fluidization characteristics and mixing degree of the mixture of lignite and magnetite powder in a vibratory fluidized bed are studied. It is found that with the increase of amplitude and frequency, the minimum fluidization gas velocity of the bed decreases first and then increases, and with the increase of the medium mass,The minimum fluidized gas velocity of the bed will decrease first and then remain unchanged, the increase of temperature and the decrease of the particle size of lignite will also decrease the minimum fluidized gas velocity of the bed, and the bed height will have little effect on the minimum fluidized gas velocity of the vibrating heavy medium fluidized bed.With the increase of wind speed and vibration intensity, the mixing degree of the bed first decreases and then increases, and finally reaches a larger value of stability, and increases with the increase of the medium mass, increases first with the increase of the bed height, and then remains the same with the increase of the bed height.Under the condition of 80-160 鈩，

本文編號：1703796