本文選題：氧氣高爐 + 氣-固兩相流　； 參考：《北京科技大學(xué)》2017年博士論文

【摘要】：隨著全球變暖、環(huán)境惡化及能源資源短缺等問題日益嚴重,各國制定了嚴格的環(huán)保減排政策,對于高能耗、高污染的鋼鐵行業(yè)來說更是面臨巨大壓力,其中高爐煉鐵工序節(jié)能減排是減少鋼鐵企業(yè)能源消耗和CO2及其它污染物排放的重要途徑。爐頂煤氣循環(huán)-氧氣鼓風(fēng)高爐煉鐵技術(shù)(簡稱氧氣高爐)的節(jié)碳減排能力已經(jīng)通過理論計算和高爐試驗得到了驗證。爐身噴吹部分脫除CO2并預(yù)熱到一定溫度的爐頂循環(huán)煤氣是氧氣高爐的關(guān)鍵特征之一,本文采用物理模型實驗和DEM-CFD耦合數(shù)學(xué)模型相結(jié)合的方式,對氧氣高爐內(nèi)氣-固兩相流進行了研究,同時對影響氧氣高爐爐身噴吹煤氣分布特征的因素進行了研究,最后提出了未來高爐DEM-CFD耦合數(shù)學(xué)模型的發(fā)展方向。首先,依據(jù)相似原理搭建了縮小比例的氧氣高爐二維冷態(tài)物理模型,并對不同高爐操作條件下尤其是氧氣高爐不同操作條件下的氣-固流動行為進行了模擬實驗研究,結(jié)果表明:氧氣高爐內(nèi)固相流動的主要特征區(qū)域與傳統(tǒng)高爐一致仍可分為四個流動區(qū)域;隨著批重的增加,靜止區(qū)形狀有向矮胖方向發(fā)展趨勢;在不同工藝條件下,處于活塞流動區(qū)域的爐料下降速度大致相同;隨著爐身噴吹煤氣量所占比例的增加,靜止區(qū)有往瘦高方向發(fā)展的趨勢。其次,結(jié)合多種數(shù)值模擬前處理軟件,完成了對二維和三維高爐DEM-CFD耦合數(shù)學(xué)模型的前處理過程,主要包括實際高爐抽象出模型高爐、幾何模型數(shù)據(jù)化處理、網(wǎng)格劃分、模型局部特殊處理、控制方程確定等部分。再次,建立了與二維冷態(tài)模型相對應(yīng)的DEM-CFD耦合數(shù)學(xué)模型,對前期已經(jīng)完成的冷態(tài)模型實驗進行簡單地數(shù)值模擬,數(shù)值模擬結(jié)果表明:與實驗結(jié)果一致,氧氣高爐爐內(nèi)仍分為四個流動區(qū)域;爐身噴吹煤氣對于氧氣高爐爐內(nèi)固體爐料運動特征沒有顯著影響,數(shù)值模擬結(jié)果比物理實驗結(jié)果更接近實際氧氣高爐爐內(nèi)顆粒運動狀態(tài);處于快速流動區(qū)域的顆粒所受到的壓力較小,但是處于爐身塊狀區(qū)和爐缸死料柱兩個區(qū)域的顆粒受擠壓力較大,這兩個區(qū)域顆粒擠壓嚴重,透氣性較差。進一步利用二維扁片氧氣高爐DEM-CFD耦合數(shù)學(xué)模型分析了多影響因素下氧氣高爐爐內(nèi)的氣-固兩相流動特征,考察了爐料粒徑、爐身風(fēng)口尺寸及爐身噴吹煤氣量與爐內(nèi)總煤氣量之比等參數(shù)對爐身噴吹煤氣分布的影響,結(jié)果如下:隨著爐內(nèi)顆粒運動達到穩(wěn)定狀態(tài),在高爐中心軸向會形成一個空隙率較低的煤氣通道,利于上升煤氣中心發(fā)展;在爐身噴吹煤氣出口水平,噴吹煤氣向中心的滲透距離最短,但隨著向上流動,逐漸滲透到高爐中心;隨著爐料粒徑和鼓風(fēng)動能的增加,爐身噴吹煤氣可以更加深入到高爐中心;爐身噴吹煤氣量與爐內(nèi)總煤氣量之比對優(yōu)化噴吹煤氣在爐內(nèi)的分布有決定性作用;影響爐身噴吹煤氣滲透距離的本質(zhì)因素是爐身風(fēng)口水平之上和之下的氣體壓力差,壓力差越小,爐身噴吹煤氣便可以更加深入到高爐中心。利用三維氧氣高爐DEM-CFD耦合數(shù)學(xué)模型,分析了氧氣高爐爐內(nèi)氣-固兩相流特征,考慮了軟熔帶、回旋區(qū)等重要特征,通過改進耦合代碼使顆粒數(shù)量更接近實際高爐,對三種爐身風(fēng)口排布方式做了計算對比,提出最優(yōu)配置。結(jié)果如下:三維模型可以消除二維模型中的壁面效應(yīng),軟熔帶以上的顆粒幾乎全部處于活塞流動中;除了在風(fēng)口回旋區(qū)及其附近,高爐邊緣的固相體積分數(shù)均比中心大,利于煤氣中心發(fā)展;固相體積分數(shù)在軟熔帶附近達到最大值(透氣性最差),在軟熔帶部位氣相單位高度壓降達到最大,且煤氣的流動方向經(jīng)過軟熔帶后也發(fā)生了微小變化;當爐身噴吹煤氣的水平速度增加到一定程度,由于其和上升煤氣的強烈碰撞,其會出現(xiàn)向下流動的趨勢,不利于充分利用;爐身風(fēng)口最優(yōu)的排布方式為爐身風(fēng)口和爐缸風(fēng)口等數(shù)量,且爐身風(fēng)口處于爐缸風(fēng)口兩兩之間,該方式可以為全爐提供更加合理的熱分布。將三維模型建模思路移植到二維扁片模型中,建立了氧氣高爐復(fù)雜二維DEM-CFD耦合模型,爐料粒徑進一步減小,研究結(jié)果如下:復(fù)雜二維模型中,固相體積分數(shù)與三維模型相比有所提高,爐內(nèi)透氣性變差;爐身上部與三維模型一致出現(xiàn)了礦石顆粒和焦炭顆粒的分層現(xiàn)象,但在爐身中下部時爐料的分層現(xiàn)象相較于三維模型提前消失;復(fù)雜二維模型在相同的爐身噴吹煤氣比例下,相較于簡單二維模型,爐身水平噴吹煤氣更難以達到高爐中心,邊緣特征剛好相反。復(fù)雜二維模型與之前模型相比準確性得到提高。氧氣高爐的DEM-CFD耦合模型未來的發(fā)展重點應(yīng)該在以下幾個方面:逐漸加入氣-固換熱、顆粒下降過程粒徑變化及軟熔帶顆粒收縮等更接近實際高爐的模型和控制方程;更為先進的DEM-CFD耦合模型,應(yīng)該考慮加入液相、氣-固-液多相間反應(yīng)、反應(yīng)進程-顆粒參數(shù)耦合模型等。氧氣高爐仿真模型的完善離不開實驗室研究及工業(yè)試驗研究基礎(chǔ)數(shù)據(jù)的支持,同樣也依賴于計算方法和計算機能力的改進。
[Abstract]:With the global warming, environmental deterioration and the shortage of energy resources and other problems, countries have formulated strict environmental protection and emission reduction policies for high energy consumption and high pollution iron and steel industry. Energy conservation and emission reduction in the blast furnace process is an important way to reduce energy consumption and CO2 and other pollutants in iron and steel enterprises. The carbon emission reduction capacity of the furnace top gas cycle oxygen blast furnace ironmaking technology (BF for short oxygen blast furnace) has been verified by theoretical calculation and blast furnace test. It is one of the key features of the oxygen blast furnace to remove CO2 and preheat to a certain temperature to a certain temperature. In this paper, the physical model experiment and DEM-CFD are used in this paper. Coupled with the coupled mathematical model, the gas solid two-phase flow in oxygen blast furnace is studied. At the same time, the factors affecting the distribution characteristics of gas distribution in the oxygen blast furnace body are studied. Finally, the development direction of the DEM-CFD coupling mathematical model in the future is put forward. First, according to the similar principle, a reduced proportion of oxygen blast furnace is built. A two-dimensional cold physical model was used to simulate the gas solid flow behavior under different operating conditions of the blast furnace, especially in the oxygen blast furnace. The results showed that the main characteristic region of the solid flow in the oxygen blast furnace could be divided into four flow regions in accordance with the conventional blast furnace. With the increase of batch weight, the static zone shape was increased. Under different technological conditions, the decreasing speed of the furnace material in the piston flow area is approximately the same. With the increase of the proportion of gas in the furnace body, the static zone has the tendency to develop in the lean direction. Secondly, combined with a variety of numerical simulation pretreatment software, the two and three dimensional blast furnace DEM-CFD coupling is completed. The pre-treatment process of the mathematical model mainly includes the actual blast furnace abstract model blast furnace, the geometric model data processing, the mesh division, the local special treatment of the model, the control equation and so on. Thirdly, the DEM-CFD coupling mathematical model corresponding to the two-dimensional cold model is established, and the cold model experiment has been completed in the earlier period. The numerical simulation results show that the oxygen blast furnace furnace is still divided into four flow areas in accordance with the experimental results, and the furnace body injection gas has no significant influence on the motion characteristics of solid charge in the oxygen blast furnace. The numerical simulation results are more close to the physical experiment results than the actual oxygen blast furnace. The pressure of the particles in the fast flow area is smaller, but the particles in the two regions of the two regions of the hearth block and the hearth die are heavily squeezed, and the two regions have serious extrusion and poor permeability. Further, the two dimensional flat sheet oxygen blast furnace DEM-CFD coupling mathematical model is used to analyze the oxygen blast furnace under the multiple influence factors. In the gas solid two phase flow characteristics, the effects of the size of the furnace material, the size of the furnace body and the ratio of the amount of gas in the furnace body and the ratio of the total gas in the furnace to the gas distribution of the furnace body are investigated. The results are as follows: with the steady state of the particle movement in the furnace, a gas channel with low void ratio will be formed in the axial direction of the blast furnace, which is beneficial to the rise of the gas. The gas center develops; in the gas outlet level of the furnace body, the penetration distance from the gas to the center is the shortest, but with the upward flow, it gradually penetrates into the center of the blast furnace; with the increase of the particle size and the kinetic energy of the blast, the furnace body can be more deep into the center of the blast furnace; the ratio of the amount of gas to the total gas in the furnace is optimized. The distribution of gas in the furnace is decisive; the essential factor affecting the penetration distance of the gas injection is the difference between the gas pressure above and below the level of the body of the furnace body. The smaller the pressure difference is, the lower the pressure difference, the gas can be further penetrated into the center of the blast furnace. The oxygen blast furnace is analyzed by the mathematical model of the DEM-CFD coupling of the three dimensional oxygen high furnace. The characteristics of gas solid two phase flow in the furnace are characterized by the consideration of the important characteristics of the soft melting zone and the gyration zone. By improving the coupling code, the number of particles is closer to the actual blast furnace. The calculation and comparison of the three kinds of furnace tuyere arrangement are made and the optimal configuration is put forward. The results are as follows: the three-dimensional model can eliminate the wall effect in the two-dimensional model and the particles above the soft melting zone. In addition to the piston flow, the solid volume fraction of the blast furnace edge is larger than that of the center, which is beneficial to the development of the gas center, and the solid volume fraction reaches the maximum value near the soft melt zone (the worst gas permeability), and the maximum pressure drop of the gas phase in the soft melt zone reaches the maximum, and the flow direction of the gas passes through the flow direction. There is a slight change in the soft melt zone. When the horizontal velocity of the gas is increased to a certain extent, the downward flow trend will appear because of the strong collision with the rising gas, which is not conducive to the full use of the gas. The best arrangement way of the body of the furnace body is the number of the hearth vents and the tuyere of the hearth, and the body of the body is in the vate tuyere. 22, this method can provide more reasonable heat distribution for the whole furnace. The three-dimensional model modeling idea is transplanted into the two-dimensional flat plate model, and the complex two-dimensional DEM-CFD coupling model of the oxygen blast furnace is established. The particle size of the furnace is further reduced. The results are as follows: in the complex two-dimensional model, the solid volume fraction is improved compared with the three-dimensional model. The gas permeability in the furnace becomes worse; the upper part of the furnace body is consistent with the three dimensional model of the stratification of ore particles and coke particles, but the stratification of the furnace material is disappearing earlier than the three-dimensional model in the lower part of the furnace body, and the complex two-dimensional model is compared to the simple two-dimensional model, and the furnace body is blown by the furnace body horizontally under the same proportion of the gas blowing in the same furnace body. It is more difficult to reach the center of the blast furnace and the edge features are just opposite. The accuracy of the complex two-dimensional model is improved compared with the previous model. The future development of the DEM-CFD coupling model of the oxygen blast furnace should be in the following aspects: the gradual addition of gas to solid heat, the change of particle size and the shrinkage of the soft melting zone particles are more close to the actual height. The model and the control equation of the furnace, the more advanced DEM-CFD coupling model, the liquid phase, the gas-solid liquid multiphase reaction and the reaction process particle parameter coupling model should be considered. The improvement of the oxygen blast furnace simulation model can not be separated from the support of the laboratory research and the basic data of the industrial test research. It also depends on the calculation method and the computer. Improvement of ability.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TF53

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