本文選題：氣固流化床 + 攪拌�。� 參考：《浙江大學》2015年碩士論文

【摘要】：氣固流化床反應(yīng)器廣泛應(yīng)用于聚烯烴工業(yè),高粘結(jié)性固體顆粒較難流態(tài)化,極易發(fā)生聚合物粘釜、顆粒聚團結(jié)塊甚至死床等不正常操作現(xiàn)象,影響流化床裝置的正常運行。為了解決粘結(jié)性顆粒穩(wěn)定流態(tài)化的問題,論文在普通流化床中引入攪拌構(gòu)件,設(shè)計和開發(fā)具有自清潔特征的攪拌流化床反應(yīng)器。圍繞這一目標,開展了三方面的研究工作：(1)攪拌流化床中D類顆粒的流化特性研究；(2)攪拌流化床中粘結(jié)性顆粒的流態(tài)化實驗研究；(3)粘結(jié)性顆粒流態(tài)化的數(shù)值模擬研究。取得了以下研究成果：(1)獲得了攪拌對Geldart D類顆粒流態(tài)化行為的影響規(guī)律。攪拌可以抑制和破碎氣泡,使得攪拌流化床與普通流化床相比具有較小的氣泡尺寸和相對較低的壓力脈動；攪拌與氣流湍動協(xié)同作用,大槳葉面積的自清潔槳攪拌作用強烈,適宜中等轉(zhuǎn)速的操作條件,而較高的轉(zhuǎn)速易形成槳葉前方的顆粒堆積和槳葉后方的氣體短路等不利現(xiàn)象,雙層錨式槳、框式槳等小槳葉面積的攪拌槳需要較高的轉(zhuǎn)速以強化流態(tài)化過程。(2)開發(fā)了自清潔攪拌流化床反應(yīng)器,實現(xiàn)了粘結(jié)性固體顆粒的穩(wěn)定流態(tài)化。研究了石蠟顆粒在普通流化床、雙層錨式攪拌流化床和自清潔攪拌流化床中流態(tài)化與粘結(jié)行為,攪拌槳葉與內(nèi)構(gòu)件的嚙合剪切作用可以有效破碎粘結(jié)性顆粒的聚團,維持床層的聚團流態(tài)化；采用床層壓降、壓力脈動標準偏差和S吸引子多種指標監(jiān)測流態(tài)化過程,S值能及時準確地反映顆粒的粘結(jié)程度與粘結(jié)發(fā)展趨勢。(3)獲得了顆粒間相互作用對氣固流動行為的影響規(guī)律�；谟嬎懔黧w力學(CFD)模擬發(fā)現(xiàn)氣固流動強烈依賴于顆粒碰撞的恢復系數(shù),當恢復系數(shù)較大時,顆粒趨于理想碰撞,床層發(fā)生均勻流態(tài)化,與轉(zhuǎn)速無關(guān)；攪拌轉(zhuǎn)速較低時,流化質(zhì)量改善不明顯,轉(zhuǎn)速較高時,氣泡尺寸減小,床層可由均勻流態(tài)化向均勻流態(tài)化轉(zhuǎn)變�；诙S床實驗和離散單元法(DEM)模擬發(fā)現(xiàn),粘結(jié)性顆粒首先粘附在一起形成粘結(jié)核,顆粒粘結(jié)性較強時,越來越多的顆粒粘附于粘結(jié)核上,形成單邊或雙邊架橋結(jié)構(gòu),很短的時間就會發(fā)生死床；若顆粒的粘結(jié)性不強,床層中氣流作用與顆粒的粘附作用相當,則以聚團的形式流態(tài)化。
[Abstract]:Gas-solid fluidized bed reactor is widely used in polyolefin industry. It is difficult to fluidize solid particles with high adhesion, and it is easy to occur abnormal operation phenomena such as polymer cladding kettle, particle agglomeration and even dead bed, which affects the normal operation of fluidized bed plant. In order to solve the problem of stable fluidization of cohesive particles, a stirred bed reactor with self-cleaning characteristics was designed and developed by introducing a mixing component into a common fluidized bed. Around this goal, three aspects of research work were carried out: 1) fluidization characteristics of D particles in agitated fluidized bed; (2) fluidization experiment of cohesive particles in agitated fluidized bed; (3) numerical simulation study on fluidization of cohesive particles. The effect of stirring on fluidization behavior of Geldart D particles was obtained. The agitation can restrain and break the bubble, make the agitated fluidized bed have smaller bubble size and lower pressure pulsation compared with the conventional fluidized bed. It is suitable for the operation condition of medium speed, but the higher speed is easy to form the unfavorable phenomena, such as the accumulation of particles in front of the blade and the gas short circuit behind the blade, etc. A self-cleaning agitated fluidized bed reactor was developed for the agitator with small blade area such as frame propeller, which needs higher rotating speed to strengthen the fluidization process. The stable fluidization of cohesive solid particles was realized. The fluidization and bonding behavior of paraffin particles in conventional fluidized bed, two-layer anchor agitated fluidized bed and self-cleaning agitated fluidized bed were studied. Maintain the agglomeration fluidization of the bed, adopt the pressure drop of the bed, The pressure fluctuation standard deviation and S attractor can accurately reflect the bonding degree of particles and the development trend of bonding in time. The influence of particle interaction on gas-solid flow behavior is obtained. Based on computational fluid dynamics (CFD) simulation, it is found that the gas-solid flow strongly depends on the recovery coefficient of particle collision. When the recovery coefficient is large, the particle tends to collide perfectly, and the bed has a uniform fluidization, which is independent of the rotational speed, and when the stirring speed is low, The fluidization quality is not improved obviously, and the bubble size decreases when the rotating speed is high, and the bed can be changed from uniform fluidization to uniform fluidization. Based on the two-dimensional bed experiment and discrete element method (DEM) simulation, it is found that the cohesive particles first adhere to each other to form a cohesive core, and when the particle adhesion is strong, more and more particles adhere to the bonding nucleus, forming a unilateral or bilateral bridging structure. The dead bed will occur in a very short time, and if the adhesion of particles is not strong and the air flow in the bed is equivalent to the adhesion of particles, the fluidization will be in the form of agglomeration.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ021.1

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本文編號：1946585