本文關鍵詞：水下礦物漿料氣力提升理論模型與流動特性實驗研究　出處：《武漢大學》2016年博士論文　論文類型：學位論文

  更多相關文章： 氣力提升 三相流 進氣方式 流型 振蕩特性

【摘要】：隨著有利于淺層開采的礦產(chǎn)資源逐漸枯竭,著眼于深部與超深部資源的高效、無污染漿料提升技術己迫在眉睫。作為舉升漿料的有效工具之一,氣力提升系統(tǒng)不含運動部件,具有結構簡單、體積小、成本低、污染少、不易堵塞和使用可靠等優(yōu)點,特別適合應用于鉆孔水力開采、深海采礦以及深水域庫區(qū)疏浚等領域,對改善環(huán)境、解決自然能源供應緊張與經(jīng)濟高速發(fā)展之間的矛盾、倡導可持續(xù)性發(fā)展具有重要的經(jīng)濟戰(zhàn)略意義。目前,因多相流的復雜性和不可預見性,針對于漿料氣力提升技術的基礎理論與實驗研究尚不完善,特別是系統(tǒng)理論模型及其內部流動機制的研究極為缺乏。本文以獲取精確、高效、通用性強的理論模型以及多相流動特性為目的,通過理論與實驗研究揭示漿料氣力提升系統(tǒng)的外部及內部特性。所開展的主要工作及其研究成果如下：(1)考慮氣體沿管軸向的非線性變化特征,基于動量定理并結合相含率、壓降與能量控制方程,建立了氣力提升系統(tǒng)的理論模型,有效解決了傳統(tǒng)模型中經(jīng)驗公式偏多及其受限于單一流型等弊端,計算得出了系統(tǒng)運行與結構參數(shù)對氣力提升性能的作用規(guī)律,結果表明：液體表觀流速、固體表觀流速與提升效率隨氣體表觀流速和管徑增加均呈先升后降之趨勢,而隨浸入率和進氣口高度增加則體現(xiàn)出單調性；氣、液、固各相體積份數(shù)沿軸向在進氣口位置出現(xiàn)突變,而在液-固兩相中基本恒定不變,即使處于氣-液-固三相段也僅發(fā)生細微變化；隨氣體表觀流速與浸入率上升,兩相段壓降基本恒定不變,而三相段壓降卻受此作用極為明顯。(2)以顆粒在液-固兩相段中的臨界模型為基礎,結合氣相含率控制方程建立了氣-液-固三相段的臨界模型,并通過與前者的比較判定顆粒得以提升的臨界條件取決于液-固兩相段。此外,考慮水底靜壓持效應,對上述兩相段中的臨界模型進行修正,其計算結果表明靜壓持效應極不利于顆粒的“啟動”,甚至造成氣力提升系統(tǒng)失效。(3)為驗證理論模型的可靠性,搭建了總高度為3m的小型氣力提升系統(tǒng),并以中、小尺度球形麥飯石陶瓷顆粒為提升介質,同時利用壓力傳感器獲取測點靜壓,實驗分析了系統(tǒng)基本性能、壓降特征與臨界條件的影響因素及其內在聯(lián)系,結果發(fā)現(xiàn)中等氣體表觀流速下實驗值與模型結果吻合較好,而其值過低與過高均因各相滑移加大及流場結構的瞬變性、隨機性等復雜因素增強引發(fā)模型預測失準,同時浸入率降低也會導致模型精確性降低。此外,對氣力提升液體與固體顆粒的臨界情況分別展開研究,發(fā)現(xiàn)前者對應臨界氣體表觀流速不受顆粒影響,而后者卻因其位置與尺度變化存在較大差異,且實驗證實了水底靜壓持效應的確使得氣力提升性能出現(xiàn)大幅惡化。(4)提出了一種兼有傳統(tǒng)氣舉和射流泵雙重功效的環(huán)噴式進氣方式,使其固體表觀流速與效率較徑向式進氣大幅升高,不過液體表觀流速并未受此影響。對兩種進氣方式下的實驗數(shù)據(jù)無量綱化處理還發(fā)現(xiàn),兩者分布規(guī)律基本服從于同一分布曲線,繼而基于能量守恒首次推導了對應的無量綱理論模型,有效支撐了上述實驗結論。另外,還通過引入水射流噴嘴研究其對氣力提升性能的影響規(guī)律,結果表明水射流噴嘴不僅可解除水底壓持效應,還使得顆粒易于躍過液-固兩相段,從而大幅增強了氣力提升性能,且噴嘴沿周向布置應適度“偏心”。(5)基于高速攝像技術對氣-液-固三相流型進行劃分,提出了泡狀流,小彈狀流,不規(guī)則彈狀流,大彈狀流(彈狀流),攪拌流,細泡狀流和環(huán)狀流七種流型,并通過與固體表觀流速峰值位置的比較判定細泡狀流為氣力提升性能對應的最佳流型,繼而基于圖像處理技術獲得了各流型下的灰度直方圖及概率圖,從而通過提取其中統(tǒng)計特征值,獲得了基于標準偏差的流型識別方法。通過利用高速攝像儀對混合流體及其中氣泡與顆粒的分布和運動特性的分析發(fā)現(xiàn),氣泡與顆粒在提升性能增強過中逐漸滲入流道芯部,反之則向管壁靠攏并趨于離散,且氣、液、固各相運動具有較強的周期性,從而使得混合流體呈振蕩式上升運動規(guī)律。而且在固體顆粒的周期運動中發(fā)現(xiàn)其提升比極小,從而找出了長期以來氣力提升性能一直偏弱的根本原因。鑒于此,利用高速攝像儀對環(huán)噴式進氣方式作用下的混合流體實測,發(fā)現(xiàn)其中提升比顯著升高。此外,氣泡的塌陷式收縮還會引發(fā)鄰近氣泡與顆粒出現(xiàn)跳躍現(xiàn)象。(6)針對湖南省道縣后江橋鐵錳礦區(qū)的特有地質條件,提出了脈沖水射流和氣力提升聯(lián)合采礦方法,實現(xiàn)了國內特大型涌水礦床開采的先例。試驗結果證實了氣力提升技術在鉆孔水力采礦中的優(yōu)越性。
[Abstract]:With the help of shallow mining of mineral resources gradually exhausted, focusing on deep and ultra deep resource efficient, pollution-free pulp lifting technology is imminent. As one of the effective tools lifting slurry, pneumatic lift system has no moving parts, and has the advantages of simple structure, small volume, low cost, less pollution, no blockage reliable and use, especially suitable for hydraulic drilling, deep-sea mining and deepwater reservoir dredging and other fields, to improve the environment, to solve the contradiction between the tension and economic supply of natural energy of rapid development, has important strategic significance to promote economic sustainable development. At present, because of the complexity of multiphase flow and unpredictable and on the basis of theoretical and Experimental Research on slurry pneumatic lifting technology is still not perfect, especially the research of system model and its internal flow mechanism is extremely lacking. In this paper, in order to obtain Accurate, efficient, strong universal theoretical model and multiphase flow characteristics for the purpose, through theoretical and experimental studies reveal the slurry pneumatic lifting external and internal characteristics of the system. The main work and research results are as follows: (1) considering the nonlinear characteristics of gas along the axial tube, and the combination of momentum theorem based on the content, pressure drop and energy control equation, establishes the theoretical model of pneumatic lift system, effectively solve the traditional model in the empirical formula of partial and limited to single flow pattern defects, calculate the operation and structure parameters of the system on the role of the law. The results showed that the performance of pneumatic lifting liquid superficial velocity, solid apparent the velocity and efficiency with the superficial gas velocity and the increase of diameter first increased and then decreased, with the immersion rate and inlet height increase reflects the monotonicity of the gas, liquid and solid; the phase volume The number of copies in the inlet position along the axial direction of mutation, but not in liquid solid two phase constant, even in the gas liquid solid three-phase section only subtle changes occur; with the superficial gas velocity and immersion rate, two-phase pressure drop is basically constant, but the pressure drop and phase effect is extremely obvious. (2) with particles in liquid-solid two-phase critical model in section as the foundation, combined with the gas holdup control equation is established for the critical model of gas liquid solid three-phase section, and through the comparison with the former decision depends on the critical condition of the particles to improve the liquid-solid two-phase section. In addition, consider the bottom the static pressure hold effect on the critical period in the two-phase model was modified, the calculation results show cuttinghold effect is not conducive to the particle "start", even cause the failure of pneumatic lift system. (3) to check the reliability of theoretical model, built a total height of 3M small Type pneumatic lift system, and in small scale spherical stone ceramic particles to enhance the media, at the same time using pressure sensors to obtain the measured static pressure, the experimental analysis of the basic performance of the system, factors affecting the characteristics of pressure drop and the critical conditions and its internal relations were found to moderate the superficial gas velocity under the experimental values are in good agreement with the model results. While its value is too low and too high due to the phase slip flow structure and increase the transient, randomness and other complex factors lead to enhanced prediction model of misalignment, and the immersion rate will lead to decrease the accuracy of the model is reduced. In addition, the critical situation of pneumatic lifting of liquid and solid particles were studied and found apparent velocity the former is not affected by the particle effects of the corresponding critical gas, while the latter is due to the differences of location and scale change, and the experiments confirmed the static effect really makes the gas to the bottom of the lifting force Can a sharp deterioration. (4) proposed a method of cyclic type intake with traditional gas lift jet pump and double effect, the apparent solid velocity and efficiency significantly increased radial intake, but the liquid superficial velocity was not affected. The dimensionless treatment was also found on experimental data two inlet mode, distribution between the basic subject to the same distribution curve, and then based on the conservation of energy is derived for the first time the dimensionless corresponding theoretical model, effectively support the experimental results. In addition, through the introduction of water jet nozzle on the influence of air lift performance. The results show that water jet nozzle can not only remove the bottom cuttinghold effect, also makes the particles easily over the liquid-solid two-phase section, thus greatly enhance the performance of pneumatic lifting, and the nozzle arrangement along the circumferential direction should be "eccentric". (5) high speed camera technology for gas - liquid - based Solid pattern was divided, put forward small bubbly flow, slug flow, irregular slug flow, large slug flow (slug flow), mixing flow, fine bubble flow and annular flow of seven flow regimes, and by comparing the determined velocity peak position and the apparent solid fine bubble flow pneumatic lifting of optimal flow pattern corresponding to the image processing technology, and then obtained the gray histogram and the probability map of each flow based on which via extracting the statistical characteristic value, the flow pattern identification method based on standard deviation. By using a high-speed camera and the analysis of mixed fluid distribution and movement characteristics of bubbles and particles. Found that the bubbles and particles in the performance enhancement in the core flow gradually, and close to the tube and tend to be discrete, and gas, liquid, and solid phase movement has a strong cyclical, so that a mixed fluid oscillation type ascending motion rule Law. And periodic motion of solid particles in that it increase than the minimum, so as to find out the long lift root cause of performance has been weak. In view of this, the use of high speed camera measurement instrument on the effect of mixed fluid inlet ring jet mode, found promoted than significantly increased. In addition, the bubble collapse will shrink the cause of bubbles and particles near the jump phenomenon. (6) the special geological condition in Hunan province after the Daoxian County River Qiaotie manganese mine, put forward the pulse water jet and air lift combined mining method, realizes the large inflow of mining precedent. The experimental results confirm the superiority of pneumatic lifting technique in borehole hydraulic mining.

【學位授予單位】：武漢大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TD857

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