本文選題：氣固流化床　切入點：靜電　出處：《浙江大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：氣固流化床中顆粒的劇烈運動和循環(huán)使得氣固兩相得以充分混合與接觸,因而流化床反應(yīng)器具有良好的熱質(zhì)傳遞性能,廣泛應(yīng)用于煤燃燒和氣化、催化裂化、造粒和干燥、烯烴聚合等工業(yè)過程中。烯烴聚合流化床中顆粒之間、顆粒與壁面之間的不斷摩擦、碰撞導(dǎo)致靜電荷的產(chǎn)生和累積。過量靜電荷的累積可能會引起粘壁、結(jié)塊等現(xiàn)象的發(fā)生,甚至造成反應(yīng)器的緊急停車,為安全穩(wěn)定生產(chǎn)帶來隱患。無論是揭示靜電的產(chǎn)生機理,還是對其進行調(diào)控甚至消除,準確的靜電檢測手段必不可少。但現(xiàn)有的顆粒荷質(zhì)比測量方法仍然存在著諸如無法實現(xiàn)在線檢測、侵入流場、信號解析過程復(fù)雜等缺點,建立一種結(jié)構(gòu)簡單、非侵入式的顆粒荷質(zhì)比在線測量方法是靜電檢測領(lǐng)域亟待解決的問題。荷電顆粒流化過程產(chǎn)生的靜電信號中蘊含著大量與顆粒運動有關(guān)的動態(tài)信息,但目前對這些動態(tài)信息的挖掘卻十分有限。基于靜電信號的相關(guān)速度測量技術(shù)已經(jīng)在氣力輸送等稀相體系中有著較為廣泛和成功的應(yīng)用,但目前尚無該方法在氣固流化床中應(yīng)用的研究報道。如果通過互相關(guān)計算方法,利用流化床中的靜電信號獲得與顆粒運動行為有關(guān)的參數(shù),則有望建立一種氣固流化床中顆粒運動的表征手段,實現(xiàn)流化床中關(guān)鍵流動參數(shù)的在線測量,對于保障反應(yīng)器的安全穩(wěn)定運行、提高生產(chǎn)效率、實現(xiàn)過程的優(yōu)化控制,具有十分重要的意義。本論文以烯烴聚合氣固流化床反應(yīng)器為研究對象,利用壓力脈動、靜電等測量手段,結(jié)合頻譜分析、互相關(guān)計算等信號處理方法,系統(tǒng)對比和分析了多級法拉第筒流化床中靜電流與壓差信號的相似性,建立了靜電流與壓差信號的定量模型,并以此為基礎(chǔ)提出了基于環(huán)形感應(yīng)電極的流化床中顆粒荷質(zhì)比的在線測量方法。結(jié)合弧形感應(yīng)電極陣列和互相關(guān)計算方法,測量了流化床中的顆粒群相關(guān)速度及其分布,建立了基于靜電信號的流化床中顆粒運動的表征方法,并基于相關(guān)速度測量方法,系統(tǒng)考察了靜電對顆粒運動的影響,擬合得到了顆粒平均荷質(zhì)比預(yù)測模型,實現(xiàn)了顆粒運動行為和顆粒荷電量的同步測量。研究結(jié)果可用于氣固流化床中靜電的檢測與防控、顆粒流動參數(shù)的測量和流化質(zhì)量的監(jiān)測,對提升反應(yīng)器的安全性和穩(wěn)定性,具有重要的指導(dǎo)意義。論文主要開展了以下四方面的研究工作：1.在自行設(shè)計的多級法拉第筒流化床中,利用頻譜分析方法系統(tǒng)對比了靜電流與壓差信號的相似性,發(fā)現(xiàn)靜電流和壓差均受到平均空隙率的影響,建立了靜電流與壓差信號之間的定量模型。當假設(shè)顆粒尺寸均一,荷電量均勻且穩(wěn)定時,靜電流與壓差信號對時間的一階導(dǎo)數(shù)成正比,比例系數(shù)與顆粒荷質(zhì)比和流化床尺寸有關(guān)。2.以上述定量模型為基礎(chǔ),提出了一種基于環(huán)形感應(yīng)電極的顆粒荷質(zhì)比在線測量方法。該方法的顆粒平均荷質(zhì)比測量結(jié)果隨表觀氣速的增加而增大,隨液體抗靜電劑(LAA)含量的增加而減小,與法拉第筒取樣法測量結(jié)果的變化趨勢一致。環(huán)形電極寬度為20 mm時,顆粒平均荷質(zhì)比測量結(jié)果的相對誤差小于23%。3.建立了基于靜電信號的流化床中顆粒群相關(guān)速度的測量方法。通過在有機玻璃流化床外壁面設(shè)置弧形感應(yīng)電極陣列,結(jié)合互相關(guān)計算方法,測量并對比了Geldart B類和D類顆粒流化床中的顆粒群相關(guān)速度平均值及其概率密度分布。在流化床密相區(qū)內(nèi),顆粒群平均相關(guān)速度隨表觀氣速和軸向高度的變化趨勢與氣泡群上升速度理論值一致；在相同過量氣速下,D類顆粒平均相關(guān)速度小于B類顆粒；提出了一種基于感應(yīng)電極陣列和顆粒群相關(guān)速度分布的流化床動態(tài)料位的檢測方法,平均料位高度測量結(jié)果的相對誤差小于10%。4.建立了一種基于感應(yīng)電極陣列的同步實現(xiàn)顆粒運動行為表征和顆粒荷質(zhì)比在線測量的方法。通過向流化床中注入微量LAA實現(xiàn)了對顆粒整體荷電水平的調(diào)控,系統(tǒng)考察了靜電對顆粒群相關(guān)速度平均值及其分布的影響,發(fā)現(xiàn)隨著靜電水平的降低,顆粒運動劇烈程度增強。當過量氣速為0.35 m/s時,與不帶電的情況相比,D類和B類顆粒飽和荷電后的顆粒群平均相關(guān)速度分別降低了約26%和50%�；诓煌o電水平下的感應(yīng)靜電壓、顆粒群平均相關(guān)速度和顆粒平均荷質(zhì)比數(shù)據(jù),擬合得到了顆粒平均荷質(zhì)比預(yù)測模型,不同表觀氣速下,模型預(yù)測結(jié)果與法拉第筒取樣法測量結(jié)果變化趨勢一致,相對誤差低于40%。
[Abstract]:Strenuous exercise and circulation of particles in gas solid fluidized bed makes the gas-solid contact and can be fully mixed, and fluidized bed reactor with good heat transfer performance, widely used in coal combustion and gasification, catalytic cracking, granulation and drying, olefin polymerization in the industrial process. Olefin polymerization of particles in fluidized bed, constant friction between particle wall collision, resulting in the accumulation and accumulation of electrostatic charge. May be excessive static charge will cause wall adhesion, agglomeration phenomenon, and even cause the reactor shutdown, brings the hidden danger for the safe and stable production. It is produced to reveal the mechanism of static electricity, or the control or even eliminate the essential. Electrostatic detection means accurately. But the existing particle charge mass ratio measurement method still exists such as cannot realize online detection, non-invasive, signal analysis process of complex defects, The establishment of a simple structure, non intrusive particle charge mass ratio measurement method is an urgent problem. The electrostatic field of electrostatic detection signal of charged particle fluidization process produced contains a large number of dynamic information related to the motion of the particles, but the mining of these dynamic information is very limited. The speed of electrostatic signal the measurement technology has been in Dilute Pneumatic Conveying has been used widely and successfully in the heterogeneous system based on, but there is no reports on this method in gas solid fluidized bed application. If by calculating the cross-correlation method, obtain the parameters associated with the behavior of particles by electrostatic signals in a fluidized bed, is expected to set up by means of a movement of particles in the gas-solid fluidized bed, measurement of flow parameters in the fluidized bed of the key, to guarantee the safe and stable operation of the reactor, improve production efficiency , to realize process control optimization, it has very important significance. This paper takes olefine polymerization reactor of gas solid fluidized bed as the research object, the use of pressure pulsation, electrostatic measurements, combined with spectral analysis, cross correlation signal processing method, system comparison and analysis of the similarity of static current and differential pressure signals of multistage Faraday tube in a fluidized bed, a static pressure difference and the quantitative model of current signal, and proposes the measurement method of particle fluidized bed induction electrode in charge mass ratio based on inductive electrode array. The combination of arc and cross-correlation calculation method in a fluidized bed of particles relative velocity and its distribution measurement, set up characterization method of moving particle fluidized bed based on the electrostatic signal, and based on the cross-correlation velocity measurement method, investigated the effects of electrostatic on particle motion, fitting to flat particles Both charge mass ratio prediction model, realizes the synchronous measurement of particle movement and particle charge. The results can be used for detection and prevention of electrostatic in gas solid fluidized bed, flow parameters measurement and monitoring of particulate fluidization quality, to enhance the safety and stability of the reactor, which has important guiding significance. This paper the research work has been carried out in the following four aspects: 1. in the multi-stage Faraday cylinder self-designed fluidized bed, system analysis method compares the similarity of static current and differential pressure signal spectrum, found that the static current and differential pressure are affected by the average air gap ratio, established the static current and differential pressure signal between the quantitative model when the assumption of the homogeneous particle size, charge uniform and stable, the electrostatic current is proportional to the pressure difference signal is a derivative of time, ratio and particle charge mass ratio and the size of the.2. in the fluidized bed The quantitative model, proposed a particle charge induction electrode based on on-line measurement method. The method of average particle charge mass ratio measurement results with the increase of apparent gas velocity increases with the liquid antistatic agent (LAA) content decreases with the increase of the trend and the Faraday tube sampling method the measurement result. The ring electrode width is 20 mm, the relative error of the average particle charge mass ratio measurement results is less than 23%.3. to establish the measurement method of electrostatic signal in particle fluidized bed. By setting the related speed based on arc induction electrode array in organic glass wall with cross-correlation fluidized bed, calculation method, the average measurement and comparison the Geldart B class and D class of particles in fluidized bed of particle velocity and its associated probability density distribution in circulating fluidized bed, particle average velocity associated with the superficial gas velocity and axial height The changing trend of the bubbles rising speed of the theoretical value; at the same excess air velocity, the average velocity is less than D particles related to B particles; a sensing electrode array and particle velocity distribution in fluidized bed dynamic related material level detection method based on the material level, the average relative error of the measuring result is less than 10%.4. a sensing electrode array to realize the synchronization of particle movement behavior and characterization of particle charge mass ratio method of on-line measurement. Based on the injection of LAA to realize the control of particles in the fluidized bed overall charge level, investigated the electrostatic effect on the average value and distribution of particles was found to decrease with increasing speed, static level the particle motion intensity is enhanced. When the excess gas velocity is 0.35 m/s, compared with uncharged, D and B particles of charged particles saturated average phase Clearance rates were reduced by about 26% and 50%. levels under different electrostatic induction based on static voltage, particle velocity and particle average average relative charge mass ratio data obtained by fitting average particle charge mass ratio prediction model, different superficial gas velocities, the model prediction results measured with Faraday tube sampling method the results are consistent. The relative error is less than 40%.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TQ051.13
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本文編號：1601731