本文選題：褐煤 + 水分復(fù)吸�。� 參考：《太原理工大學(xué)》2016年碩士論文

【摘要】：煤炭作為我國能源消費的基石,長期以來占到能源消費結(jié)構(gòu)的70%左右。隨著優(yōu)質(zhì)煤資源的日益緊缺,儲量豐富的褐煤的大規(guī)模開采利用勢在必行。但是褐煤水分含量高、熱值低、易風化、易自燃等特點嚴重制約了褐煤的高效清潔利用。褐煤表面含有豐富的含氧官能團,加之疏松多孔的結(jié)構(gòu)使其即使是在干燥提質(zhì)后也會再次吸收水分。因此,在干燥提質(zhì)過程中對褐煤物理和化學(xué)結(jié)構(gòu)進行調(diào)變,是褐煤清潔高效利用的理論基礎(chǔ),具有非常重要的現(xiàn)實意義。本文選取我國典型的褐煤作為研究對象,運用原位傅里葉紅外光譜儀對不同提質(zhì)條件下褐煤基團的變化情況進行了表征,分析了褐煤在干燥提質(zhì)中各種基團的分解、氧化和轉(zhuǎn)化規(guī)律。結(jié)合化學(xué)滴定法及氮吸附表征結(jié)果,考察了不同提質(zhì)氣氛和時間下褐煤物化結(jié)構(gòu)的演變及其對水分復(fù)吸特性的影響。研究結(jié)果主要包括以下幾個方面:(1)提質(zhì)褐煤的平衡含水量(EMC)隨著提質(zhì)時間的延長及溫度的升高而降低。160 oC和200 oC下,氮氣氣氛中所得提質(zhì)煤樣的EMC明顯低于空氣氛中所得煤樣,但240 oC下,兩種氣氛下所得煤樣的EMC基本相等。(2)CHX基團在提質(zhì)溫度高于200 oC時明顯減少,尤其在空氣氣氛下減少較多。分解活化能的大小順序為CH2CHCH3,氧化活化能大小順序為CHCH3CH2。褐煤中羧基的親水性最強,醛類物質(zhì)次之,其分別約為酮類物質(zhì)的9倍和3倍。醌類、酯類和酸酐物質(zhì)與其平衡含水量之間沒有明顯關(guān)系。(3)提質(zhì)溫度高于160 oC時,N2和水蒸氣以及CO2和水蒸氣的混合氣氛中煤樣的失重率大于單一氣氛。混合氣氛中水蒸氣的存在使得褐煤在提質(zhì)過程中的中孔數(shù)量減小,比表面積明顯降低,從而使得提質(zhì)煤的EMC減小。提質(zhì)煤的在相對濕度95%時水分子填滿小于40nm的孔道,EMC與孔體積有良好的線性關(guān)系。(4)N2和水蒸氣混合氣氛下所得提質(zhì)煤樣的COOH含量較N2中得到的煤樣有明顯增加,但在CO2中,水蒸氣的引入對COOH的分解影響不大。N2氣氛下,隨著干燥提質(zhì)的進行,OH和C=O含量逐漸減少。在N2和水蒸氣混合氣氛中,C=O在干燥過程中先減少后增加。(5)相對濕度小于17%時,煤樣的水分復(fù)吸量主要與含氧官能團的量有關(guān)。在17%~75%時,EMC的變化速率較慢,說明水分在褐煤表面形成多層吸附。相對濕度由75%增加到95%時,水分在褐煤孔道中形成毛細凝聚,同時水分在脫附過程中出現(xiàn)滯后現(xiàn)象。
[Abstract]:As the cornerstone of energy consumption in China, coal has accounted for about 70% of the energy consumption structure for a long time.With the increasing shortage of high quality coal resources, it is imperative to exploit lignite with abundant reserves.However, the high moisture content, low calorific value, easy weathering and easy spontaneous combustion of lignite seriously restrict the efficient and clean utilization of lignite.Lignite has abundant oxygen-containing functional groups on the surface, and the porous structure makes it absorb water again even after drying and tempering.Therefore, adjusting the physical and chemical structure of lignite during drying and upgrading is the theoretical basis for the clean and efficient utilization of lignite, which is of great practical significance.In this paper, the typical lignite in China is selected as the research object. The changes of lignite groups under different quality conditions are characterized by in situ Fourier transform infrared spectroscopy (FTIR), and the decomposition of various groups in the drying process of lignite is analyzed.Oxidation and conversion.Combined with the results of chemical titration and nitrogen adsorption, the evolution of the physicochemical structure of lignite and its influence on the water reabsorption characteristics were investigated under different upgrading atmosphere and time.The results include the following aspects: (1) the equilibrium water content of lignite is decreased with the increase of temperature and time. The EMC of extracted coal in nitrogen atmosphere is obviously lower than that in empty atmosphere.However, at 240oC, the EMC of the coal samples obtained in two kinds of atmospheres was basically equal. The EMC group decreased obviously when the quality temperature was higher than 200oC, especially in the air atmosphere.The order of decomposition activation energy is Ch _ 2CHCH _ 3 and the order of oxidation activation energy is CHCH _ 3CH _ 2.The hydrophilicity of carboxyl group was the strongest in lignite, followed by aldehydes, about 9 times and 3 times of ketones, respectively.There is no obvious relationship between quinones, esters and anhydride and their equilibrium water content. 3) the weight loss rate of coal samples in mixed atmosphere of nitrogen and water vapor and CO2 and water vapor is higher than that in single atmosphere when the temperature is higher than 160oC.The presence of water vapor in the mixed atmosphere decreases the number of mesoporous and the specific surface area of lignite in the process of upgrading, thus reducing the EMC of lignite.There is a good linear relationship between the pore volume of extracted coal and the pore volume when the water molecule is filled with water molecule less than 40nm at 95% relative humidity. The COOH content of the extracted coal sample in mixed atmosphere is obviously higher than that of the coal sample in N2, but in CO2, the content of EMC is higher than that of the coal sample in N _ 2, but in CO2, the content of COOH is much higher than that of coal sample in N _ 2.The introduction of water vapor had little effect on the decomposition of COOH in N _ 2 atmosphere, and the content of OH and C _ 2O gradually decreased with the drying and upgrading.In the mixed atmosphere of N2 and water vapor, the moisture reabsorption of coal samples is mainly related to the amount of oxygen functional groups when the relative humidity is less than 17.The change rate of EMC is slow in the range of 17 ~ 75, which indicates that the water is adsorbed on the surface of lignite.When the relative humidity is increased from 75% to 95%, the capillary condensation is formed in the lignite pore channel, and the moisture lags in the desorption process.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TD849.2

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