本文選題：天然氣水合物 + 降壓法��； 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：隨著當(dāng)今工業(yè)技術(shù)的不斷發(fā)展，對(duì)能源的需求不斷增加。能源問題陸續(xù)被提上世界各國的議事日程，成為亟待解決的重要問題。天然氣水合物被認(rèn)為是21世紀(jì)最具有開發(fā)前景的潛在新型潔凈能源之一，具有高密度、高熱值、潔凈環(huán)保的優(yōu)點(diǎn)。1m3的天然氣水合物完全分解可以產(chǎn)生164m3標(biāo)準(zhǔn)狀態(tài)下的甲烷氣體。天然氣水合物主要存在于陸地（基本為永久凍土層）和海洋中。目前在有關(guān)天然氣水合物分布、儲(chǔ)量以及運(yùn)輸?shù)然A(chǔ)研究方面已取得重大進(jìn)展，但是在開采方法上的研究相對(duì)滯后。 本文對(duì)國內(nèi)外天然氣水合物的研究概況做了簡單介紹。目前對(duì)于開采天然氣水合物主要有四種開采方案：注熱法、降壓法、注化學(xué)試劑法和CO2置換法，在這四種不同的開采方案中，由于降壓法在實(shí)際操作中只要開始就不需要連續(xù)的投入設(shè)備和材料，，在所有開采方案中成本最為低廉。本文數(shù)值模擬降壓法開采天然氣水合物的過程，在具體的數(shù)值模擬中，運(yùn)用了商業(yè)軟件FLUENT，建立降壓法開采天然氣水合物的數(shù)學(xué)模型，數(shù)值模擬了天然氣水合物的分解。 在FLUENT軟件中加入自編的用戶自定義函數(shù)（UDF），用于修改質(zhì)量守恒方程、能量守恒方程和相對(duì)滲透率。采用二維軸對(duì)稱的幾何模型，數(shù)值模擬一個(gè)天然氣水合物降壓分解實(shí)驗(yàn)。模型中考慮氣相、水相和天然氣水合物相。天然氣和水的流動(dòng)符合達(dá)西定律。開始時(shí)，打開模型兩端的閥門，使天然氣水合物與外界的低壓環(huán)境接觸，天然氣水合物開始分解，甲烷氣體和水開始流動(dòng)。 數(shù)值模擬過程包括多孔介質(zhì)中多相流動(dòng)以及傳熱和化學(xué)反應(yīng)。分別得到當(dāng)天然氣水合物分解過程進(jìn)行至10分鐘、40分鐘、80分鐘、160分鐘和200分鐘時(shí)的壓力場(chǎng)、溫度場(chǎng)，數(shù)值模擬的結(jié)果表明，水合物的分解速率受出口壓力和周圍環(huán)境溫度等參數(shù)的影響，提高周圍環(huán)境溫度或者降低出口壓力都有助于提高水合物分解速率。分解過程在0到80分鐘內(nèi)溫度變化率和壓力變化率最大，在80至120分鐘內(nèi)天然氣水合物的溫度變化率和壓力變化率相對(duì)平緩，在120分鐘至200分鐘溫度變化率和壓力變化率逐漸減小。研究成果為進(jìn)一步開展室內(nèi)模擬實(shí)驗(yàn)以及工程應(yīng)用研究提供了重要依據(jù)。
[Abstract]:With the development of industrial technology, the demand for energy is increasing. Energy issues have been put on the world's agenda one after another, becoming an important issue to be solved. Natural gas hydrate is considered as one of the most promising potential clean energy sources in the 21st century. The gas hydrate with high density, high calorific value and clean environmental protection can completely decompose methane gas under 164m3 standard state. Natural gas hydrate mainly exists on land (basically permafrost) and ocean. At present, great progress has been made in the basic research of gas hydrate distribution, reserves and transportation, but the research on exploitation methods is lagging behind. This paper briefly introduces the research situation of natural gas hydrate at home and abroad. At present, there are four kinds of exploitation schemes for exploiting natural gas hydrate: injection heat method, depressurization method, chemical reagent injection method and CO2 replacement method. In these four different mining schemes, Since the depressurization method does not require continuous input equipment and materials as long as it starts in practice, it is the cheapest in all mining schemes. In this paper, the process of exploiting natural gas hydrate by depressurization method is simulated. In the concrete numerical simulation, the mathematical model of natural gas hydrate extraction by pressure reduction method is established by using commercial software fluent, and the decomposition of natural gas hydrate is numerically simulated. The user defined function is added to fluent software, which is used to modify the mass conservation equation, energy conservation equation and relative permeability. A gas hydrate decomposing experiment is numerically simulated using a two-dimensional axisymmetric geometric model. Gas phase, water phase and gas hydrate phase are considered in the model. The flow of natural gas and water follows Darcy's law. At the beginning, the valve at both ends of the model is opened to make the gas hydrate contact with the external low pressure environment, the natural gas hydrate begins to decompose, and the methane gas and water begin to flow. The numerical simulation process includes multiphase flow, heat transfer and chemical reaction in porous media. The pressure field, temperature field and numerical simulation results are obtained when the gas hydrate decomposition process is carried out to 10 min / 40 min / 80 min / 160 min and 200 min, respectively. The decomposition rate of hydrate is affected by the parameters such as outlet pressure and ambient temperature. Increasing the ambient temperature or lowering the outlet pressure can help to increase the rate of hydrate decomposition. The temperature change rate and pressure change rate of natural gas hydrate is the largest in 0 to 80 minutes, and the temperature and pressure change rate of gas hydrate is relatively flat in 80 to 120 minutes. From 120 minutes to 200 minutes, the temperature change rate and pressure change rate gradually decreased. The research results provide an important basis for further indoor simulation experiments and engineering application research.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P744.4

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