【摘要】：中國褐煤資源儲量豐富,價格低廉,但褐煤具有水分高、熱值低、燃燒效率低、易自燃的特點,不利于儲存和遠(yuǎn)距離運(yùn)輸。褐煤提質(zhì)預(yù)處理已成為國內(nèi)外研究的熱點,熱解提質(zhì)即其中的一種簡單可靠的處理方式。由于褐煤是一種類似膠質(zhì)體的多孔性物質(zhì),提質(zhì)煤表面存在大量的孔洞和縫隙,在潮濕的環(huán)境中會再次吸水,即產(chǎn)生復(fù)吸水現(xiàn)象。研究提質(zhì)煤的復(fù)吸水機(jī)理并尋求降低復(fù)吸水率的途徑,對改善提質(zhì)煤品質(zhì)、提高褐煤的利用效率有重要意義。本文選取收到基水分為52.3%的云南昭通褐煤為研究對象,進(jìn)行低溫?zé)崽豳|(zhì)(提質(zhì)溫度為200-500℃),提質(zhì)前分別使用三種方式對原煤進(jìn)行預(yù)處理,以期達(dá)到降低提質(zhì)煤復(fù)吸水率的目的。從物理結(jié)構(gòu)角度使用瀝青負(fù)載處理,從化學(xué)結(jié)構(gòu)角度分別使用鹽酸、硼氫化鈉預(yù)處理。實驗采用傅里葉轉(zhuǎn)換紅外光譜(FTIR)分析了提質(zhì)過程中煤表面含氧官能團(tuán)OH和C=O相對含量的變化,采用氮氣等溫吸附法和掃描式電子顯微鏡(SEM)分析了提質(zhì)煤的孔隙結(jié)構(gòu)和表面形貌特征變化。使用恒溫恒濕箱測試了提質(zhì)煤的復(fù)吸水特性,使用TG-DTG系統(tǒng)分析了提質(zhì)煤樣的燃燒特性。研究表明:1)隨著提質(zhì)溫度的升高,褐煤中的含氧官能團(tuán)C=O和OH含量逐漸減少,提質(zhì)煤的孔容積和比表面積逐漸增大,平均孔徑逐漸減小;提質(zhì)煤的復(fù)吸水率和自燃傾向都逐漸降低;2)鹽酸預(yù)處理提高了提質(zhì)煤的發(fā)熱量,降低了提質(zhì)煤中的OH含量,顯著降低了提質(zhì)煤的復(fù)吸水率,降低了自燃傾向和反應(yīng)活性、提高了燃燒劇烈程度和燃盡性能;3)硼氫化鈉預(yù)處理抑制了揮發(fā)分的析出,降低了提質(zhì)煤的發(fā)熱量;抑制了微孔的生成和發(fā)展,對降低復(fù)吸水率的作用較小,提高了褐煤的自燃傾向,降低了燃盡性能、燃燒反應(yīng)活性和燃燒劇烈程度;4)瀝青負(fù)載處理抑制了微孔的生成,降低了提質(zhì)煤的比表面積,瀝青對提質(zhì)煤的復(fù)吸水特性表現(xiàn)在極性影響和負(fù)載影響兩個方面,在200-300℃提質(zhì)時,瀝青濃度高于5wt%時才能降低復(fù)吸水率,在400-500℃時,提質(zhì)煤的復(fù)吸水率隨瀝青濃度的升高而降低,瀝青負(fù)載處理對提質(zhì)煤燃燒特性的影響取決于熱解溫度區(qū)間。
[Abstract]:Lignite resources in China are rich in reserves and low in price, but lignite is characterized by high moisture content, low calorific value, low combustion efficiency and easy spontaneous combustion, which is not conducive to storage and long-distance transportation. The pretreatment of lignite has become a hot spot at home and abroad, and pyrolysis is one of the simple and reliable methods. Because lignite is a kind of porous material similar to colloid, there are a large number of holes and gaps on the surface of the coal, which will absorb water again in the wet environment, that is, the phenomenon of reabsorption. It is of great significance to study the mechanism of reabsorbing water and to find a way to reduce the rate of water absorption. It is of great significance to improve the quality of extracted coal and improve the utilization efficiency of lignite. In this paper, Yunnan Zhaotong lignite, which is divided into 52.3% basic water, is selected as the research object. The raw coal is pretreated with three methods before the pretreatment, which is carried out at low temperature (200 ~ 500 鈩，

本文編號：2334133