本文選題：流化床　切入點(diǎn)：脈動(dòng)氣流　出處：《東北電力大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：流化床在工業(yè)中具有廣泛的應(yīng)用范圍,它在工業(yè)應(yīng)用中可以將固態(tài)顆粒等屬性物質(zhì)進(jìn)行流態(tài)化處理從而實(shí)現(xiàn)大規(guī)模、高效率的工業(yè)應(yīng)用。流化床與傳統(tǒng)的反應(yīng)器及設(shè)備相比較,流化床設(shè)備具有設(shè)備大型化、過程易于控制、傳熱傳質(zhì)效率較高、床內(nèi)溫度分布較均勻等優(yōu)點(diǎn),并且能夠改善氣固兩相間的接觸效率,減少傳熱熱阻,從而提高傳熱效率。但是在處理一些較細(xì)顆粒、比重較低的生物質(zhì)和含水較大原料時(shí)容易出現(xiàn)溝流、結(jié)塊等非正常流化現(xiàn)象。所以應(yīng)對流化床進(jìn)行部分改進(jìn)。我們針對上述流化床所出現(xiàn)的運(yùn)行非正�，F(xiàn)象進(jìn)行了技術(shù)探討和改進(jìn),提出了脈動(dòng)流化床的解決方案,并針對此種方案的可行性以及同普通流化床的運(yùn)行特性進(jìn)行了對比,對脈動(dòng)流化床的運(yùn)行特征進(jìn)行了分析,嘗試找到其合理的運(yùn)行工況參數(shù)。為此我們進(jìn)行了以下幾方面的探究:本次試驗(yàn)系統(tǒng)在原有常規(guī)流化床的基礎(chǔ)上增加脈動(dòng)氣流,這種情況下在脈動(dòng)氣流停止加入時(shí)也會(huì)有一股穩(wěn)定的氣流進(jìn)入對流化床對原料進(jìn)行流化。并且在總進(jìn)氣流量不變的情況下來研究穩(wěn)定氣流和脈動(dòng)氣流不同比例分配對流化床流動(dòng)特性及傳熱傳質(zhì)效果帶來的影響,通過實(shí)驗(yàn)探究了在總氣流量一定的情況下,改變穩(wěn)定氣流和脈動(dòng)氣流流量分配比例并利用采集的溫度、壓力、濕度等參數(shù)對流化床的流化情況以及傳熱傳質(zhì)效果進(jìn)行分析,嘗試?yán)脷饬鞑▌?dòng)圖以及空氣焓值進(jìn)行分析。發(fā)現(xiàn)在較低脈動(dòng)氣體流量下低頻率的0.25Hz脈動(dòng)氣流適合流化內(nèi)傳熱傳質(zhì)的進(jìn)行,而在脈動(dòng)氣流流量加大后則高頻率的3.3Hz更為適合;并且在加入脈動(dòng)氣體之后會(huì)提高氣固兩相間的傳熱傳質(zhì),但在頻率提升到一定高度之后優(yōu)勢減弱。而溫度參數(shù)對物料最終的干燥程度即最終濕含量影響最大,在進(jìn)行了多個(gè)溫度的實(shí)驗(yàn)之后發(fā)現(xiàn),在90℃時(shí)流化床內(nèi)傳熱傳質(zhì)速度最快干燥效果最好,并且能量消耗較少;在進(jìn)氣配比方面,進(jìn)氣比例的大小具有一定的影響,在進(jìn)氣流量較小時(shí)應(yīng)提高脈動(dòng)氣流流量,而在流量較大時(shí)應(yīng)使穩(wěn)定氣流保持在最小流化風(fēng)速流量附近。在對相關(guān)實(shí)驗(yàn)結(jié)果進(jìn)行分析后,提出利用脈動(dòng)氣流波動(dòng)曲線圖合理的解釋了相關(guān)結(jié)論;利用濕空氣焓值變化來分析并合理解釋了相關(guān)實(shí)驗(yàn)現(xiàn)象,提出了一種合理的解釋方法。
[Abstract]:Fluidized bed has a wide range of applications in industry, it can fluidize solid particles and other attribute matter to realize large-scale, high-efficiency industrial application. Fluidized bed equipment has the advantages of large-scale equipment, easy control of the process, high efficiency of heat and mass transfer, uniform temperature distribution in the bed, and can improve the contact efficiency between the gas-solid phases and reduce the heat transfer resistance. So as to improve the heat transfer efficiency. But it is easy to appear ditch flow when dealing with some fine particles, low specific gravity biomass and higher water content raw materials. Therefore, some improvements should be made to the fluidized bed. We discussed and improved the operation abnormal phenomenon of the fluidized bed mentioned above, and put forward the solution of the pulsating fluidized bed. In view of the feasibility of the scheme and the operation characteristics of the conventional fluidized bed, the operating characteristics of the pulsating fluidized bed are analyzed. We try to find out the reasonable operating condition parameters. For this reason, we have carried out the following research: this test system increases pulsating air flow on the basis of the original conventional fluidized bed, In this case, there will also be a steady flow of air entering the fluidized bed to fluidize the feedstock when the pulsating flow stops to be added, and the different proportion of stable and pulsating airflow will be studied under the condition of constant total intake air flow. The effect of flow characteristics and heat and mass transfer in fluidized bed, The fluidization and heat and mass transfer effect of fluidized bed are analyzed by changing the distribution ratio of steady and pulsating air flow and using the parameters of temperature, pressure, humidity and so on under the condition of constant total gas flow. It is found that 0.25Hz pulsatile flow at low frequency is suitable for heat and mass transfer in fluidization, but 3.3Hz at high frequency when the flow rate of pulsating gas is increased. After adding pulsating gas, the heat and mass transfer between the gas and solid phases will be improved, but the advantage will be weakened after the frequency is raised to a certain height, and the temperature parameters will have the greatest influence on the final drying degree of the material, that is, the final wet content. After several temperature experiments, it is found that the fastest heat and mass transfer speed in fluidized bed is the best at 90 鈩，

本文編號(hào)：1566234