中速球式磨機(jī)流場(chǎng)分析及結(jié)構(gòu)優(yōu)化
發(fā)布時(shí)間：2019-05-30 00:22
【摘要】：中速球式磨機(jī)利用碾磨件相互擠壓作用來磨制煤粉,集研磨、烘干、傳輸、分選等工序于一體,其流程簡(jiǎn)單、粉磨效率高。現(xiàn)已經(jīng)廣泛用于鋼鐵、火電、水泥以及其它工業(yè)領(lǐng)域。但在實(shí)際生產(chǎn)中出現(xiàn)了許多問題,如壓損很大、產(chǎn)量不穩(wěn)定、煤粉粒度變粗、過粉現(xiàn)象嚴(yán)重等。掌握磨腔內(nèi)流場(chǎng)分布規(guī)律和粉磨機(jī)理,為腔內(nèi)結(jié)構(gòu)優(yōu)化提供理論指導(dǎo),并對(duì)提高粉磨效率和降低能耗具有重要的意義。本文以江蘇大\丶派杓蒲蟹⒌腅M型磨機(jī)為研究對(duì)象,依據(jù)CFD技術(shù)和工程流體動(dòng)力學(xué)理論,采用離散相模型(DPM),湍流模型Realizable k-ε及SIMPLE算法對(duì)磨腔湍流運(yùn)動(dòng)進(jìn)行數(shù)值模擬。分析研究磨腔速度場(chǎng)、壓力場(chǎng)、溫度場(chǎng)、顆粒軌跡和流線等特性。先對(duì)氣相流場(chǎng)進(jìn)行數(shù)值模擬,待其收斂后,再加入離散顆粒相,顆粒運(yùn)動(dòng)采用隨機(jī)軌道模型,對(duì)氣固兩相流采用單向耦合的方法,最后根據(jù)模擬結(jié)果對(duì)風(fēng)環(huán)、風(fēng)室及灰斗進(jìn)行結(jié)構(gòu)優(yōu)化。綜合分析結(jié)果表明:中速球式磨機(jī)腔內(nèi)流場(chǎng)具有明顯的三維旋轉(zhuǎn)流動(dòng)特性,運(yùn)動(dòng)主要由突擴(kuò)運(yùn)動(dòng)、射流、回流、和繞流運(yùn)動(dòng)耦合而成。當(dāng)氣體經(jīng)過風(fēng)環(huán)時(shí)速度很大,形成射流,在灰斗與磨盤間形成渦流區(qū)。在風(fēng)環(huán)處高溫?zé)犸L(fēng)與煤粉顆粒開始耦合,并伴隨著大量的能量交換,上升的氣流夾帶煤粉顆粒向上運(yùn)動(dòng),較大顆粒落回磨盤,較小的顆粒隨氣流進(jìn)入分離器中再次分離,不合格的煤粉通過灰斗落回磨盤。受磨盤和磨球旋轉(zhuǎn)的影響,氣流沿著磨球做繞流運(yùn)動(dòng),磨球周圍形成許多小渦流。磨機(jī)在運(yùn)行過程中能耗大,壓降很大。通過增加入磨風(fēng)量來研究氣流的變化規(guī)律,結(jié)果表明隨著氣流增加,風(fēng)環(huán)處風(fēng)速增加明顯,但磨腔內(nèi)壓損也明顯增大。根據(jù)磨腔流場(chǎng)仿真結(jié)果并結(jié)合工程中出現(xiàn)的問題,本文對(duì)中速磨機(jī)的結(jié)構(gòu)優(yōu)化主要側(cè)重于風(fēng)環(huán)、風(fēng)室以及灰斗的改進(jìn),并對(duì)改進(jìn)模型進(jìn)行流場(chǎng)分析。通過封堵部分風(fēng)環(huán)后,風(fēng)環(huán)出口處的流量增加,但壓損也明顯增加。針對(duì)風(fēng)室結(jié)構(gòu),在風(fēng)室底部入口安裝導(dǎo)流板。分析表明,各風(fēng)環(huán)處的流通量分布趨于均勻化,有利于氣粉耦合和傳遞。對(duì)灰斗的錐體進(jìn)行延長(zhǎng),數(shù)值模擬結(jié)果表明流場(chǎng)湍流脈動(dòng)現(xiàn)象較弱,縱向渦流明顯減小。通過分析可以看出,結(jié)構(gòu)優(yōu)化后的中速磨機(jī)湍動(dòng)現(xiàn)象、粉體輸運(yùn)效率均有所改善,磨機(jī)內(nèi)壓力損失有不同程度的下降。
[Abstract]:The medium speed ball mill uses the mutual extrusion of grinding parts to grind pulverized coal, which integrates grinding, drying, transmission, separation and other working procedures. The process is simple and the grinding efficiency is high. It has been widely used in iron and steel, thermal power, cement and other industrial fields. However, there are many problems in practical production, such as large pressure loss, unstable output, thicker particle size of pulverized coal, serious overpowder and so on. Mastering the distribution law and grinding mechanism of flow field in grinding cavity provides theoretical guidance for the optimization of intracavity structure, and is of great significance to improve grinding efficiency and reduce energy consumption. This paper is based on Jiangsu University. According to CFD technique and engineering fluid dynamics theory, the discrete phase model (DPM), turbulence model Realizable k-蔚 and SIMPLE algorithm are used to simulate the turbulent motion of the grinding cavity. The velocity field, pressure field, temperature field, particle trajectory and streamline of the grinding cavity are analyzed and studied. The numerical simulation of the gas phase flow field is carried out, and then the discrete particle phase is added after it converges. The stochastic orbit model is used for the particle motion, and the unidirectional coupling method is used for the gas-solid two-phase flow. Finally, according to the simulation results, the wind ring is used. The structure of air chamber and ash hopper is optimized. The comprehensive analysis results show that the flow field in the cavity of the medium speed ball mill has obvious three-dimensional rotating flow characteristics, and the motion is mainly composed of sudden expansion motion, jet, reflux, and flow around the motion. When the gas passes through the wind ring, the velocity is very large, forming a jet and forming a vortex zone between the ash bucket and the grinding disk. At the air ring, the high temperature hot air and pulverized coal particles begin to be coupled, and with a large amount of energy exchange, the rising air flow carries the pulverized coal particles upward, the larger particles fall back to the grinding disk, and the smaller particles enter the separator again with the air flow. The unqualified pulverized coal falls back into the grinding disk through the ash bucket. Under the influence of the rotation of the grinding disk and the grinding ball, the air flow moves around the grinding ball, and many small swirls are formed around the grinding ball. In the operation process of the mill, the energy consumption is large and the pressure drop is very large. The variation of air flow is studied by increasing the air volume. The results show that with the increase of air flow, the wind speed at the wind ring increases obviously, but the pressure loss in the grinding cavity also increases obviously. According to the simulation results of grinding cavity flow field and combined with the problems in engineering, the structure optimization of medium speed mill mainly focuses on the improvement of air ring, air chamber and ash bucket, and the flow field analysis of the improved model is carried out. After blocking part of the wind ring, the flow rate at the outlet of the wind ring increases, but the pressure loss also increases obviously. According to the structure of the air chamber, the guide plate is installed at the bottom entrance of the air chamber. The analysis shows that the flux distribution at each wind ring tends to be uniform, which is beneficial to the coupling and transmission of gas and powder. The cone of the ash bucket is prolonged. The numerical simulation results show that the turbulent pulsation of the flow field is weak and the longitudinal vortex is obviously reduced. Through the analysis, it can be seen that the turbulent phenomenon of medium speed mill after structure optimization, the powder transport efficiency has been improved, and the pressure loss in the mill has decreased to varying degrees.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TH69
本文編號(hào)：2488350
[Abstract]:The medium speed ball mill uses the mutual extrusion of grinding parts to grind pulverized coal, which integrates grinding, drying, transmission, separation and other working procedures. The process is simple and the grinding efficiency is high. It has been widely used in iron and steel, thermal power, cement and other industrial fields. However, there are many problems in practical production, such as large pressure loss, unstable output, thicker particle size of pulverized coal, serious overpowder and so on. Mastering the distribution law and grinding mechanism of flow field in grinding cavity provides theoretical guidance for the optimization of intracavity structure, and is of great significance to improve grinding efficiency and reduce energy consumption. This paper is based on Jiangsu University. According to CFD technique and engineering fluid dynamics theory, the discrete phase model (DPM), turbulence model Realizable k-蔚 and SIMPLE algorithm are used to simulate the turbulent motion of the grinding cavity. The velocity field, pressure field, temperature field, particle trajectory and streamline of the grinding cavity are analyzed and studied. The numerical simulation of the gas phase flow field is carried out, and then the discrete particle phase is added after it converges. The stochastic orbit model is used for the particle motion, and the unidirectional coupling method is used for the gas-solid two-phase flow. Finally, according to the simulation results, the wind ring is used. The structure of air chamber and ash hopper is optimized. The comprehensive analysis results show that the flow field in the cavity of the medium speed ball mill has obvious three-dimensional rotating flow characteristics, and the motion is mainly composed of sudden expansion motion, jet, reflux, and flow around the motion. When the gas passes through the wind ring, the velocity is very large, forming a jet and forming a vortex zone between the ash bucket and the grinding disk. At the air ring, the high temperature hot air and pulverized coal particles begin to be coupled, and with a large amount of energy exchange, the rising air flow carries the pulverized coal particles upward, the larger particles fall back to the grinding disk, and the smaller particles enter the separator again with the air flow. The unqualified pulverized coal falls back into the grinding disk through the ash bucket. Under the influence of the rotation of the grinding disk and the grinding ball, the air flow moves around the grinding ball, and many small swirls are formed around the grinding ball. In the operation process of the mill, the energy consumption is large and the pressure drop is very large. The variation of air flow is studied by increasing the air volume. The results show that with the increase of air flow, the wind speed at the wind ring increases obviously, but the pressure loss in the grinding cavity also increases obviously. According to the simulation results of grinding cavity flow field and combined with the problems in engineering, the structure optimization of medium speed mill mainly focuses on the improvement of air ring, air chamber and ash bucket, and the flow field analysis of the improved model is carried out. After blocking part of the wind ring, the flow rate at the outlet of the wind ring increases, but the pressure loss also increases obviously. According to the structure of the air chamber, the guide plate is installed at the bottom entrance of the air chamber. The analysis shows that the flux distribution at each wind ring tends to be uniform, which is beneficial to the coupling and transmission of gas and powder. The cone of the ash bucket is prolonged. The numerical simulation results show that the turbulent pulsation of the flow field is weak and the longitudinal vortex is obviously reduced. Through the analysis, it can be seen that the turbulent phenomenon of medium speed mill after structure optimization, the powder transport efficiency has been improved, and the pressure loss in the mill has decreased to varying degrees.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TH69
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