本文選題：脈動(dòng)氣流分選　切入點(diǎn)：分選機(jī)理　出處：《中國礦業(yè)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：脈動(dòng)氣流分選技術(shù)作為一種新型氣流分選技術(shù),利用顆粒在非穩(wěn)定氣流中的運(yùn)動(dòng)規(guī)律,彌補(bǔ)了傳統(tǒng)氣流分選按密度分選的不足,目前已在電子廢棄物和工業(yè)廢催化劑回收利用,非金屬礦分選等領(lǐng)域得到了應(yīng)用,為礦物分選、二次資源回收利用提供了新的思路和方法。但由于非穩(wěn)定氣流中,氣流和顆粒運(yùn)動(dòng)復(fù)雜,對(duì)脈動(dòng)氣流的機(jī)理研究尚有不足,限制了脈動(dòng)氣流分選技術(shù)的進(jìn)一步發(fā)展。論文分析了已有脈動(dòng)氣流分選機(jī)理的不足。認(rèn)為脈動(dòng)氣流利用顆粒到達(dá)沉降末速前的加速度差進(jìn)行分選,缺乏理論和實(shí)驗(yàn)支持,并與實(shí)際不符。而以單顆粒動(dòng)力學(xué)方程為基礎(chǔ)的虛擬質(zhì)量力理論,無法解釋高密度顆粒按密度分選的行為,并且對(duì)阻力系數(shù)的修正需要進(jìn)一步研究。為了完善分選機(jī)理,本文提出了基于顆粒群的脈動(dòng)氣流分選理論,認(rèn)為分選柱內(nèi)的濃相區(qū)域是實(shí)現(xiàn)顆粒按密度分選的主要區(qū)域,對(duì)脈動(dòng)氣流波形的作用原理也進(jìn)行了討論。論文通過大渦模擬模擬了顆粒在脈動(dòng)氣流場中的繞流問題,通過脈動(dòng)氣流與穩(wěn)定氣流下阻力系數(shù)的比較,發(fā)現(xiàn)脈動(dòng)氣流下阻力系數(shù)的變化與雷諾數(shù)區(qū)間和氣流加減速有關(guān)。同時(shí)對(duì)球體繞流、渦旋結(jié)構(gòu)的變化情況進(jìn)行了研究,分析了阻力系數(shù)變化的原因。研究結(jié)果表明,阻力系數(shù)變化不是顆粒按密度分選的主要原因,減少顆粒處于低雷諾數(shù)段時(shí)間,控制氣流加減速段比例有助于提高分選效果。為了進(jìn)一步驗(yàn)證基于顆粒群的分選理論,論文以脈動(dòng)氣固流化床為載體,研究了顆粒在濃相環(huán)境下的運(yùn)動(dòng)規(guī)律。通過研究脈動(dòng)氣流操作參數(shù)對(duì)床層和氣泡特性的影響,發(fā)現(xiàn)了氣流脈動(dòng)頻率對(duì)床層穩(wěn)定性影響較大,但床層膨脹率變化絕對(duì)值不大;氣流脈動(dòng)頻率的增加有助于氣泡生成頻率和尺寸增加。通過觀察外加顆粒的運(yùn)動(dòng)規(guī)律,發(fā)現(xiàn)氣泡對(duì)于顆粒下落起加速作用,虛擬質(zhì)量力能夠促進(jìn)顆粒按密度分離,并隨氣流脈動(dòng)頻率和顆粒體積濃度增加而變得顯著。論文最后對(duì)-6+3 mm的難選細(xì)粒煤進(jìn)行了實(shí)際分選實(shí)驗(yàn),Ep值達(dá)到0.17,最佳分選效率為48.08%,可燃體回收率達(dá)到68.22%。利用前述分選機(jī)理解釋了脈動(dòng)氣流振幅、脈動(dòng)頻率、入料量對(duì)分選效果的影響,提出了臨界脈動(dòng)頻率和臨界顆粒體積濃度的概念。本文結(jié)合數(shù)值模擬和實(shí)驗(yàn)技術(shù)對(duì)顆粒在脈動(dòng)氣流場中的運(yùn)動(dòng)和分離規(guī)律進(jìn)行了研究,完善了脈動(dòng)氣流分選理論,為實(shí)際分選過程中,操作參數(shù)的控制,設(shè)備結(jié)構(gòu)和分選工藝的設(shè)計(jì)提供了理論基礎(chǔ),對(duì)于其它涉及脈動(dòng)氣固兩相流的研究,具有一定的參考價(jià)值。
[Abstract]:As a new type of gas flow separation technology, pulsating flow separation technology makes use of the movement law of particles in unstable airflow, which makes up for the shortage of traditional airflow separation according to density. At present, it has been recovered and used in electronic wastes and industrial waste catalysts. The application of non-metallic ore separation and other fields has provided a new way of thinking and method for mineral separation and secondary resource recovery. However, due to the complex movement of air and particles in unstable airflow, the study on mechanism of pulsating flow is still insufficient. The further development of pulsating flow separation technology is limited. The paper analyzes the shortcomings of the existing mechanism of pulsating airflow sorting. It is considered that pulsating airflow is separated by the acceleration difference before the particle reaches the final velocity of settlement, which lacks theoretical and experimental support. The virtual mass force theory based on single particle dynamics equation can not explain the separation behavior of high density particles according to density, and the modification of resistance coefficient needs further study. In this paper, the theory of pulsating airflow separation based on particle group is put forward. It is considered that the dense phase region in the column is the main region to realize the separation of particles according to the density. The working principle of pulsating flow waveform is also discussed. The particle flow around the pulsating flow field is simulated by large eddy simulation, and the drag coefficient under pulsating and steady airflow is compared. It is found that the variation of drag coefficient under pulsating flow is related to the Reynolds number range and the acceleration and deceleration of airflow. At the same time, the variation of the vortex structure and the flow around the sphere are studied, and the reasons for the variation of the drag coefficient are analyzed. The change of drag coefficient is not the main reason for particle separation by density, and the reduction of particle size at low Reynolds number, and the control of the proportion of airflow acceleration and deceleration are helpful to improve the separation effect. In order to further verify the separation theory based on particle group, In this paper, the moving law of particles in dense phase environment is studied with pulsating gas-solid fluidized bed as carrier. By studying the influence of operating parameters of pulsating airflow on bed and bubble characteristics, it is found that the frequency of pulsating gas flow has a great influence on the stability of bed. However, the absolute value of the bed expansion rate is small, and the increase of the gas flow pulsation frequency contributes to the increase of the bubble formation frequency and the size. By observing the motion law of the added particles, it is found that the bubble accelerates the falling of the particles. Virtual mass forces facilitate the separation of particles by density, At the end of the paper, the actual separation experiment of 6 ~ 3 mm fine coal was carried out, and the optimum separation efficiency was 48.08, and the recovery rate of combustible body reached 68.22. Finally, the actual separation experiment was carried out for the refractory fine coal with 6 ~ (-3) mm. The optimum separation efficiency was 48.08 and the recovery rate of combustible body was 68.22. The aforementioned sorting mechanism explains the amplitude of the pulsating airflow, The effects of pulsating frequency and feed quantity on the separation efficiency are discussed. The concepts of critical pulsation frequency and critical particle volume concentration are proposed. The motion and separation of particles in pulsating airflow field are studied by numerical simulation and experimental techniques. The theory of pulsating airflow separation is perfected, which provides a theoretical basis for the control of operational parameters, the design of equipment structure and separation process in the actual separation process. It is of certain reference value for the study of pulsating gas-solid two-phase flow.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TD94

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 劉成永;楊麗娜;朱憲然;程亮;;中速磨煤機(jī)動(dòng)態(tài)分離器特性研究及其對(duì)鍋爐性能的影響[J];華北電力技術(shù);2014年07期

2 董良;趙躍民;謝衛(wèi)寧;段晨龍;李浩;華成鵬;;Insights in active pulsing air separation technology for coarse coal slime by DEM-CFD approach[J];Journal of Central South University;2013年12期

3 賀靖峰;何亞群;段晨龍;趙躍民;王帥;;脈動(dòng)氣流回收蛭石的實(shí)驗(yàn)研究與數(shù)值模擬[J];中國礦業(yè)大學(xué)學(xué)報(bào);2010年04期

4 王帥;何亞群;王海鋒;周念鑫;蘭亮;;細(xì)粒煤主動(dòng)脈動(dòng)氣流分選試驗(yàn)研究[J];選煤技術(shù);2010年03期

5 賀靖峰;何亞群;張洪召;溫保峰;左蔚然;;主動(dòng)脈動(dòng)氣流分選處理廢棄催化劑[J];環(huán)境工程;2008年S1期

6 何亞群;趙躍民;段晨龍;左蔚然;張文軍;;主動(dòng)脈動(dòng)氣流分選動(dòng)力學(xué)模型及其數(shù)值模擬[J];中國礦業(yè)大學(xué)學(xué)報(bào);2008年02期

7 ;Low Density Dry Coal Beneficiation Using an Air Dense Medium Fluidized Bed[J];Journal of China University of Mining & Technology;2007年03期

8 段晨龍,何亞群,趙躍民,宋樹磊,王海鋒;阻尼式脈動(dòng)氣流分選裝置處理電子廢棄物的基礎(chǔ)研究[J];環(huán)境工程;2005年04期

9 鄒建鋒,任安祿,鄧見;圓球繞流場的尾渦分析和升阻力研究[J];空氣動(dòng)力學(xué)學(xué)報(bào);2004年03期

10 沈凌;;中國礦產(chǎn)資源的特點(diǎn)及可持續(xù)發(fā)展戰(zhàn)略[J];科技進(jìn)步與對(duì)策;2003年13期

，

本文編號(hào)：1645465