發(fā)布時(shí)間：2018-06-02 13:13

  本文選題：CO_2吸收 + 離子液體　； 參考：《重慶大學(xué)》2015年博士論文

【摘要】：隨著經(jīng)濟(jì)的快速發(fā)展,化石能源的大量消耗,CO2的過(guò)量排放給人類(lèi)環(huán)境與生存帶來(lái)了嚴(yán)重威脅,因此CO2的捕集和封存在國(guó)內(nèi)外引起了廣泛關(guān)注。據(jù)統(tǒng)計(jì),全球CO2排放量的40%以上是來(lái)自于電廠(chǎng)及其它化石燃料轉(zhuǎn)化活動(dòng),聯(lián)合國(guó)政府間氣候變化專(zhuān)門(mén)委員會(huì)(IPCC)已將針對(duì)燃煤電廠(chǎng)的CO2捕集與封存技術(shù)作為2050年溫室氣體減排目標(biāo)最重要的技術(shù)方向。在各種捕集CO2的方法中,降膜吸收法具有氣液膜之間相互不貫透、設(shè)備壓降小、降膜較薄、接觸面積大、傳質(zhì)阻力小等優(yōu)點(diǎn),特別適合用在電廠(chǎng)煙氣流量大,CO2分壓低(燃煤電廠(chǎng)的煙氣中CO2體積含量為12%15%)的場(chǎng)合。為深入分析新型綠色有機(jī)溶劑離子液體(IL)和有機(jī)胺混合溶液在降膜反應(yīng)器內(nèi)的流動(dòng)特性及CO2吸收性能,本文采用四甲基銨甘氨酸離子液體([N1111][Gly])與乙醇胺(MEA)混合溶液作為吸收劑,針對(duì)其降膜吸收過(guò)程中涉及到的CO2吸收性能、液膜流動(dòng)特性及傳熱傳質(zhì)過(guò)程中的液膜界面湍動(dòng)現(xiàn)象等問(wèn)題進(jìn)行了研究。本文的主要研究?jī)?nèi)容和結(jié)論如下:①研究了豎直降膜反應(yīng)器在均勻冷卻條件下,5%IL+15%MEA混合溶液在豎直反應(yīng)器內(nèi)的流動(dòng)特性,對(duì)比了液膜在豎直平板和豎直槽道內(nèi)成膜的區(qū)別,討論了液體流量和液膜與平板之間溫差對(duì)液膜鋪展寬度和鋪展面積的影響。結(jié)果表明:隨著液體流量及液膜與平板之間溫差的增加,液膜的鋪展寬度和面積增加;由于豎直槽道內(nèi)角區(qū)處毛細(xì)力作用的影響,使液膜在降膜槽道內(nèi)的鋪展有別于液膜在豎直平板上的鋪展,對(duì)液膜的鋪展面積、液膜流型等有較大的影響;液膜在豎直平板上流動(dòng)時(shí)具有較大的鋪展面積;通過(guò)水和混合工質(zhì)的降膜流動(dòng)特性對(duì)比得出,液體物性影響液膜的擴(kuò)展強(qiáng)度,進(jìn)而影響液膜的鋪展寬度和面積。②對(duì)比了四種吸收劑20%MEA、20%IL、5%IL+15%MEA、10%IL+10%MEA(質(zhì)量比)的CO2吸收性能,從中選擇一種性能較好的工質(zhì)5%IL+15%MEA作為CO2吸收劑,研究了在逆流氣體吹掃下,其在降膜反應(yīng)器中的流型轉(zhuǎn)換規(guī)律,給出了流型之間相互轉(zhuǎn)換的臨界液體流量,并分析了在不同流型下的CO2吸收速率、液體利用率和液相傳質(zhì)系數(shù),最后探討了液體溫度、氣體流量、氣體進(jìn)口CO2濃度對(duì)CO2吸收速率和脫除率的影響。實(shí)驗(yàn)結(jié)果表明:5%IL+15%MEA每摩爾胺吸收的CO2量達(dá)到最大,且相對(duì)其他三種吸收劑,5%IL+15%MEA吸收劑更易被完全利用;在降膜流動(dòng)過(guò)程中,隨液體流量的改變,液膜呈現(xiàn)溪流、片狀流和完整流三種流型,逆流氣體提高了液膜流型相互轉(zhuǎn)換的臨界液體流量;液膜流型對(duì)CO2吸收性能的影響很大,相對(duì)溪流和片狀流,完整流具有較高的CO2吸收速率和液體利用率,而液相傳質(zhì)系數(shù)卻在溪流和片狀流下較大;由于接觸角的滯后性,在液膜成膜過(guò)程中,先以較大的液體流量使液膜在反應(yīng)器內(nèi)形成完整流之后,再逐漸減小液體流量至完整流轉(zhuǎn)換成片狀流的臨界流量,可以使液膜在較小的液體流量下維持完整流,從而達(dá)到較高的吸收速率和液體利用率;適當(dāng)提高吸收劑溫度可以提高CO2的吸收速率和脫除效率,而氣體流量的改變需要均衡考慮CO2吸收速率和CO2脫除率兩者的變化,氣體進(jìn)口CO2濃度的增加可以提高CO2吸收速率,但是對(duì)CO2脫除率并沒(méi)有太大的影響③采用紋影儀觀察了四種工質(zhì)(H2O、20%MEA、20%IL、5%IL+15%MEA)的靜止液膜中心,被單根或雙根加熱管局部加熱時(shí)的界面湍動(dòng)現(xiàn)象,分析了不同溫度場(chǎng)對(duì)界面對(duì)流結(jié)構(gòu)的影響。實(shí)驗(yàn)結(jié)果表明:在相同溫度梯度下,四種工質(zhì)界面均呈現(xiàn)清晰的與溫度梯度方向一致的滾筒狀暗條紋結(jié)構(gòu),條紋之間相互獨(dú)立;與純水相比,當(dāng)加入乙醇胺MEA或離子液體IL時(shí),局部界面對(duì)流結(jié)構(gòu)發(fā)生改變;對(duì)于每一種工質(zhì),隨著界面溫度梯度的不同,其界面對(duì)流結(jié)構(gòu)亦發(fā)生改變,當(dāng)液膜整體溫度升高時(shí),由于溶劑的揮發(fā),溫度梯度和濃度梯度的共同作用會(huì)影響界面對(duì)流形態(tài);相比液膜被單根加熱管局部加熱時(shí)的界面湍動(dòng)形態(tài),當(dāng)液膜被雙根加熱管同時(shí)加熱時(shí),在兩根加熱管中心產(chǎn)生了一條分界線(xiàn),此外,界面溫度的非穩(wěn)態(tài)變化導(dǎo)致兩根加熱管中心的分界線(xiàn)也是在逐漸變化,并不是一條穩(wěn)定在兩根加熱管之間的直線(xiàn)。④采用紋影儀觀察了三種CO2吸收劑(20%MEA、20%IL、5%IL+15%MEA)在吸收CO2過(guò)程中,由于傳質(zhì)不均引起的界面湍動(dòng)現(xiàn)象,分析了液膜厚度和氣體流量對(duì)界面對(duì)流形態(tài)及液相傳質(zhì)系數(shù)的影響。結(jié)果表明:界面局部濃度發(fā)生變化導(dǎo)致Marangoni對(duì)流可以強(qiáng)化液相傳質(zhì),使實(shí)際液相傳質(zhì)系數(shù)遠(yuǎn)遠(yuǎn)大于理論的液相傳質(zhì)系數(shù),且?值(實(shí)際測(cè)量得到的液相傳質(zhì)系數(shù)與理論計(jì)算得到的液相傳質(zhì)系數(shù)之比)與吸收過(guò)程緊密相關(guān),隨吸收時(shí)間的增加,?值先是呈上升趨勢(shì),到達(dá)峰值后,隨之減小;在不同液膜厚度和氣體流量下,界面對(duì)流形態(tài)不同,?值隨液膜厚度和氣相流量的變化沒(méi)有呈現(xiàn)明顯的規(guī)律。⑤界面處的微細(xì)對(duì)流可以強(qiáng)化液膜內(nèi)的擴(kuò)散傳質(zhì),基于此,提出了在液膜表面構(gòu)造非均勻溫度場(chǎng)從而誘導(dǎo)液膜內(nèi)產(chǎn)生微細(xì)對(duì)流的方法。采用紅外熱像儀研究了液膜在局部加熱的豎直平板和豎直槽道內(nèi)流動(dòng)時(shí)的表面溫度場(chǎng)分布,探討了局部加熱時(shí)液膜破裂的臨界溫度。結(jié)果表明:在豎直槽道內(nèi),隨局部加熱溫度的增加,液膜會(huì)發(fā)生破裂,液膜破裂的臨界溫度隨液體流量的增加而增加,相比在橫向方向加熱,在槽道縱向方向上加熱時(shí),液膜表面的溫度場(chǎng)分布更加不均勻,且液膜破裂的臨界溫度大于在橫向方向加熱時(shí)的情況,布置三根加熱片時(shí)的液膜破裂臨界溫度大于布置一根時(shí)的情況;而在豎直平板上,實(shí)驗(yàn)過(guò)程中并沒(méi)有觀察到液膜的破裂,而是發(fā)現(xiàn)了液膜在流動(dòng)方向上逐漸收縮,隨局部加熱溫度的增加,液膜收縮加劇,液膜鋪展面積急劇減小。
[Abstract]:With the rapid development of the economy and the large consumption of fossil energy, the excessive emission of CO2 poses a serious threat to the human environment and survival. Therefore, the capture and sealing of CO2 has aroused widespread concern at home and abroad. According to statistics, more than 40% of the global CO2 emissions are derived from the power plant and its fossil fuel conversion activities, and the Intergovernmental climate of the United Nations The change special committee (IPCC) has taken the CO2 capture and storage technology for coal-fired power plants as the most important technical direction for the greenhouse gas emission reduction targets in 2050. In the various methods of collecting CO2, the falling film absorption method has the advantages of interpenetration between gas and liquid membranes, small pressure drop of equipment, thin film reduction, large contact area and small mass transfer resistance. It is suitable for the situation that the flue gas flow rate of the power plant is large and the CO2 partial pressure is low (the volume content of CO2 in the flue gas of the coal-fired power plant is 12%15%). In order to analyze the flow characteristics and CO2 absorption properties of the new green organic solvent ionic liquid (IL) and the organic amine mixed solution in the falling film reactor, the four methammonium glycine ionic liquid ([N1111][Gly]) is used in this paper. The mixed solution of ethanolamine (MEA) is used as an absorbent to study the CO2 absorption properties involved in the process of falling film absorption, the liquid film flow characteristics and the turbulent phenomenon of the liquid film interface during the heat and mass transfer process. The main contents and conclusions of this paper are as follows: (1) the vertical drop film reactor was studied under uniform cooling condition, 5 The flow characteristics of%IL+15%MEA mixed solution in a vertical reactor were compared. The difference between the film formation in the vertical plate and the vertical channel was compared. The effect of the temperature difference between the liquid flow and the liquid film and the flat plate on the spreading width and spread area of the liquid film was discussed. The results showed that the liquid film was increased with the temperature difference between the liquid film and the flat plate. The spreading width and area increase; the spreading of the liquid film in the falling film channel is different from the spreading of the liquid film on the vertical plate because of the influence of the capillary force at the inner corner of the vertical channel. It has a great influence on the spreading area of the liquid film and the flow pattern of the liquid film; the liquid film has a larger spreading area when the liquid film is flowing on the vertical plate; through water and the water, the liquid film has a large spreading area. The comparison of the flow characteristics of the mixed refrigerants shows that the liquid property affects the expansion strength of the liquid film, and then affects the spreading width and area of the liquid film. Secondly, the CO2 absorbability of four absorbents, 20%MEA, 20%IL, 5%IL+15%MEA, 10%IL+10%MEA (mass ratio), is compared, and a better refrigerant 5%IL+15%MEA is selected as a CO2 absorbent from it. The flow pattern conversion law in the falling film reactor was carried out under the flow of countercurrent gas. The critical liquid flow rate between the flow patterns was given. The CO2 absorption rate, the liquid utilization rate and the liquid mass transfer coefficient under different flow patterns were analyzed. Finally, the liquid temperature, the gas flow rate, the gas inlet CO2 concentration and the CO2 absorption rate were discussed. The experimental results show that the CO2 amount per mole of 5%IL+15%MEA is maximum, and the 5%IL+15%MEA absorbents are more easily utilized relative to the other three absorbents. In the process of falling film flow, the liquid film presents stream, flake flow and complete flow pattern with the change of liquid flow, and the countercurrent gas improves the flow pattern of the liquid film. The liquid film flow pattern has a great influence on the absorption properties of CO2, relative stream and flake flow, the complete flow has higher CO2 absorption rate and liquid utilization ratio, while the liquid mass transfer coefficient is larger under the stream and flake flow. After the complete flow of the liquid film is formed in the reactor, the critical flow of the liquid flow to the complete flow is gradually reduced, and the liquid film can maintain a complete flow under the smaller liquid flow, thus achieving a higher absorption rate and liquid utilization. The absorption rate and removal efficiency of CO2 can be improved by increasing the absorbant temperature properly. The change of gas flow rate and CO2 absorption rate and CO2 removal rate need to be balanced. The increase of CO2 concentration in gas inlet can increase the absorption rate of CO2, but there is no significant effect on the CO2 removal rate. (3) the static liquid membrane center of four types of refrigerants (H2O, 20%MEA, 20%IL, 5%IL+15%MEA) is observed by the schlierer. The effects of different temperature fields on the interfacial convection structure are analyzed. The experimental results show that under the same temperature gradient, the four types of working fluids have a clear structure of roller like dark stripes that are consistent with the direction of the temperature gradient, and the lines are independent of each other. Compared with pure water, when ethanol is added to the ethanol, it is added to the ethanol. At the time of amine MEA or ionic liquid IL, the convective structure of the local interface changes; for each material, the interfacial convection structure changes with the temperature gradient of the interface. When the overall temperature of the liquid film increases, the common action of the temperature gradient and the concentration gradient will affect the interfacial convection morphology because of the evaporation of the liquid film. When the root heating tube is heated locally, the boundary of the two heating tubes is heated at the same time when the liquid film is heated at the same time. In addition, the non steady state change of the interface temperature leads to the gradual change in the dividing line between the two heating tubes, which is not a straight line stable between the two heating tubes. The effect of three CO2 absorbents (20%MEA, 20%IL, 5%IL+15%MEA) on the interfacial turbulence caused by uneven mass transfer during the absorption of CO2 was observed by schlieren. The effect of the thickness of the liquid film and the flow of gas on the interfacial convection morphology and the mass transfer coefficient were analyzed. The results showed that the change of the local concentration of the boundary caused the strong convection of Marangoni to be strong. The mass transfer in liquid phase makes the mass transfer coefficient of the actual liquid phase far outweigh the theoretical liquid mass transfer coefficient, and the value (the ratio of the liquid phase mass transfer coefficient obtained by the actual measurement and the theoretical calculation of the mass transfer coefficient) is closely related to the absorption process. With the increase of the absorption time, the value of the liquid phase is on the rise first, and then decreases after the peak, and in the different liquid. Under the film thickness and gas flow, the convection morphology of the interface varies with the thickness of the liquid film and the change of the gas flow rate. 5. The micro convection at the interface can strengthen the diffusion and mass transfer in the liquid film. Based on this, an inhomogeneous temperature field on the surface of the liquid film is proposed to induce the micro convection in the liquid film. The temperature distribution of the surface temperature field of the liquid film in a vertical plate and a vertical channel with local heating is studied by infrared thermography. The critical temperature of the rupture of the liquid film is discussed when the local heating is heated. The results show that the liquid film will break up with the increase of the local heating temperature in the vertical channel, and the critical temperature of the rupture of the liquid film follows the liquid flow. When heating in the transverse direction and heating in the longitudinal direction of the channel, the temperature distribution on the surface of the liquid film is more uneven than in the longitudinal direction of the channel, and the critical temperature of the rupture of the liquid film is greater than that in the transverse direction. The critical temperature of the rupture of the liquid film when the three heated sheets is arranged is greater than that of the arrangement of one time; but on the vertical plate, In the course of the experiment, the rupture of the liquid film was not observed, but it was found that the liquid film gradually contracted in the flow direction. With the increase of the local heating temperature, the shrinkage of the liquid film increased and the spreading area of the liquid film decreased sharply.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：X773

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相關(guān)期刊論文 前3條

1 方誠(chéng)剛;張鋒;馬靜文;王淵濤;耿皎;張志炳;;氨基酸離子液體-MDEA混合水溶液對(duì)CO_2的降膜吸收[J];化工學(xué)報(bào);2011年03期

2 趙賢廣;張鋒;彭t，

本文編號(hào)：1968886