發(fā)布時間：2018-02-27 14:10

  本文關(guān)鍵詞： 超臨界狀態(tài)吸附 注熱 吸附勢理論 密度泛函理論 最優(yōu)注熱比　出處：《太原理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：注熱增產(chǎn)煤層氣是時下煤層氣增產(chǎn)的有效方法之一。儲層條件多數(shù)超過甲烷的臨界溫度和臨界壓力,所以煤層中的甲烷更多以超臨界狀態(tài)存在。注熱增產(chǎn)煤層氣時,面臨的首要問題是如何置換出吸附態(tài)的超臨界狀態(tài)甲烷。當(dāng)煤層中注入水蒸氣時,水蒸氣同樣會在煤孔隙裂隙表面上吸附,打破煤吸附超臨界狀態(tài)甲烷的吸附平衡。由于煤層中的超臨界甲烷大多以吸附態(tài)存在的,所以研究煤吸附超臨界狀態(tài)甲烷吸附模型和水蒸氣吸附機(jī)理與吸附規(guī)律顯得尤為重要。本文依據(jù)熱力學(xué)理論分析了吸附過程熱量的變化;依據(jù)表面物理化學(xué)原理分析了不同煤階煤吸附超臨界甲烷和水的吸附特性;依據(jù)有機(jī)化學(xué)知識分析了煤分子結(jié)構(gòu),并采用密度泛函理論(DFT)模擬計算不同煤階與甲烷、水的競爭吸附機(jī)理,探索注熱開采機(jī)理。主要結(jié)論如下:(1)以超臨界狀態(tài)甲烷為研究對象,分別根據(jù)吸附勢理論模型和等量吸附熱吸附模型,構(gòu)建了兩種由超臨界吸附等溫方程和任意兩組等溫吸附實驗數(shù)據(jù)預(yù)測計算任意等溫度條件下的超臨界吸附量的方法。根據(jù)27.5℃、50℃下的實測吸附等溫線,采用兩種計算方法分別計算了40℃下的超臨界吸附等溫線。計算結(jié)果與40℃實測的吸附等溫線比較,兩種計算方法都與實測結(jié)果基本一致,吸附勢模型計算過程更簡單。(2)根據(jù)量子化學(xué)密度泛函理論,采用Gaussian軟件模擬了褐煤分子、高揮發(fā)分煙煤分子、無煙煤分子等不同煤階煤分子與CH_4分子之間、水分子之間的吸附機(jī)理和注熱開采煤層氣的增產(chǎn)機(jī)理。模擬計算結(jié)果表明:(1)不同煤階的煤分子吸附CH_4的吸附位點(diǎn)不同,褐煤分子吸附CH_4最穩(wěn)定的位點(diǎn)在褐煤分子上方3.9683×10-10m處,吸附能為-20.92k J/mol;高揮發(fā)分煙煤分子最穩(wěn)定吸附位點(diǎn)在于高揮發(fā)分煙煤分子上方,六元環(huán)側(cè),分子之間的距離為4.596×10-10m,吸附能為-27.79k J/mol;無煙煤分子吸附最穩(wěn)定位點(diǎn)在無煙煤分子平面上方4.6107×10-10m處,吸附能為-38.92k J/mol。上述三種煤階吸附CH_4的作用范圍都在范德華力有效作用范圍以內(nèi),無論煤階如何,煤分子與CH_4之間是物理吸附,且隨著變質(zhì)程度增加,吸附CH_4的吸附能增加,即煤階越高,吸附越穩(wěn)定。(2)當(dāng)水分子吸附平衡時,H_2O和褐煤分子、高揮發(fā)分煙煤分子和無煙煤分子中的羥基形成氫鍵。通過Mulliken電荷布局分析,得知煤分子中的羥基為氫鍵給予體,水分子為氫鍵受體,由于電荷偏移,導(dǎo)致了煤分子中的羥基鍵能和水分子中的羥基鍵能都發(fā)生了改變。褐煤分子中含氧官能團(tuán)種類較多,羧基吸附H_2O能力最強(qiáng),此時的吸附結(jié)構(gòu)最穩(wěn)定。通過比較吸附CH_4時的和H_2O時的吸附能,得到不同煤階煤分子對H_2O的吸附能力均要強(qiáng)于CH_4,氫鍵的作用強(qiáng)于范德華力。(3)當(dāng)CH_4、H_2O同時存在吸附體系中時,H_2O會搶占CH_4的吸附位,并且H_2O與煤分子之間的距離均要比CH_4近,吸附H_2O的能力要強(qiáng)于吸附CH_4。由于水與煤的吸附能大,與煤分子間距離近,H_2O與CH_4之間存在競爭吸附,所以注熱蒸汽能提高煤層氣采出率。(3)為最大限度的置換出吸附態(tài)下的超臨界甲烷,又不注入過量水蒸氣,提高注氣效果,根據(jù)單組分吸附勢模型計算的單組分吸附量和吸附能,再根據(jù)多組分N-A吸附模型計算混合氣體總吸附量,最后導(dǎo)出了單純考慮水蒸氣和超臨界甲烷競爭吸附下最優(yōu)注熱比。該參數(shù)對注熱工藝設(shè)計具有一定指導(dǎo)意義。
[Abstract]:Note the hot coal gas production is one of the effective methods nowadays for enhancing coalbed reservoir conditions. The critical temperature and the critical pressure of methane over the majority, so in the coal seam methane more in supercritical state. Heat injection enhancing coalbed methane production, the primary problem facing is how to replace supercritical methane adsorbed. When steam injection in coal seam, water vapor will also be adsorbed on coal pore and fracture surface, breaking the adsorption equilibrium of supercritical methane adsorption of coal. Because of coal in supercritical methane mostly exist in the adsorbed state, so research on coal adsorption supercritical methane adsorption model and water vapor adsorption mechanism and adsorption law is this is particularly important. Based on the theory of thermodynamics analysis of the change of the adsorption process of heat; based on the surface physical chemistry principle analysis of adsorption characteristics of supercritical methane and water adsorption of different rank coals According to the knowledge of organic chemistry; analysis of the molecular structure of coal, and using density functional theory (DFT) simulation of different rank coal and methane, the competitive adsorption mechanism of water, to explore the mechanism of heat injection exploitation. The main conclusions are as follows: (1) uses the supercritical methane as the research object, according to the model and the isosteric adsorption potential theory the heat adsorption model, and constructs two kinds of prediction methods of supercritical adsorption and calculation of arbitrary temperature conditions by supercritical adsorption isotherm and the adsorption isotherm any two groups of experimental data. According to the measured 27.5 DEG C, adsorptionisotherm 50 C, 40 C under supercritical adsorption isotherms were calculated by two the calculation method respectively. Adsorption isotherm calculation results and measured 40 degrees, two kinds of calculation methods are basically consistent with the measured results, the adsorption potential model process is more simple. (2) according to quantum chemical density functional theory, using G Aussian software to simulate the lignite molecules, high volatile bituminous coal, anthracite and other molecules between different rank coals and CH_4 molecules, water molecules between adsorption mechanism and heat injection exploitation of coalbed gas production mechanism. The simulation results show that: (1) adsorption sites of coal molecular adsorption of CH_4 with different coal ranks of lignite CH_4 is the most stable adsorption sites in the molecule above 3.9683 * 10-10m lignite, adsorption energy of -20.92k J/mol; high volatile bituminous coal is the most stable molecular adsorption sites of high volatile bituminous coal molecule above six membered ring side, the distance between the molecules is 4.596 * 10-10m, the adsorption energy is -27.79k J/mol the most stable adsorption; Anthracite location above the molecular plane of 4.6107 * 10-10m anthracite, the adsorption energy range above three J/mol. -38.92k rank CH_4 adsorption were within the effective range of fan Edward force, regardless of rank as Where, between the coal molecule and CH_4 physical adsorption, and with the degree of metamorphism increases, the adsorption of CH_4 increases, the rank is higher, more stable adsorption. (2) when the water molecular adsorption, H_2O molecules and lignite, high volatile bituminous coal and anthracite molecules in molecular hydrogen bond formation. Through hydroxyl Mulliken charge distribution analysis, that the coal molecule hydroxyl donor hydrogen bonds, water molecules are hydrogen bond acceptor, because the charge migration leads to hydroxyl bond hydroxyl bond in coal molecular energy and water molecules can be changed. The oxygen molecule to many kinds of lignite, adsorption capacity of the strongest H_2O carboxyl group at this time, the most stable adsorption structure. By comparing the adsorption adsorption of CH_4 and H_2O when the can, get the adsorption capacity of different rank coals of molecular H_2O were stronger than CH_4, the role of strong hydrogen bonds in Van Edward. (3) when CH_4, H_2O and adsorbent System, the adsorption of H_2O will occupy the CH_4 bit, and between H_2O and coal molecular distance than the CH_4, the adsorption of H_2O is stronger than CH_4. adsorption due to the adsorption of water and energy of coal, and coal molecular distance between near, existence of competitive adsorption between H_2O and CH_4, so the steam injection can improve the recovery rate of CBM. (3) a supercritical methane adsorption state for the replacement of maximum limit, and the excess water vapor injection, improve gas injection effect, according to the single component adsorption potential calculation model of single component adsorption capacity and adsorption energy, according to the multicomponent adsorption of N-A mixed model calculation the total gas adsorption capacity, finally derived only consider the adsorption of water vapor and supercritical methane injection. The optimal competition ratio parameter has certain guiding significance on the heat injection process design.

【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】：2017
【分類號】：O647.3;TE37

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